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Institute of Medicine (US) Subcommittee on Technical Specifications for a High-Energy Emergency Relief Ration. High-Energy, Nutrient-Dense Emergency Relief Food Product. Washington (DC): National Academies Press (US); 2002.

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High-Energy, Nutrient-Dense Emergency Relief Food Product.

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3Processing and Packaging of the Emergency Food Product

Developing energy-dense nutritional foods that can be packaged and stored for extended periods of time in environments that vary from arctic to tropical presents a challenge to the processor. In an emergency situation these products must also meet the nutritional needs of all age groups from infants to adults, and be sufficiently palatable to be consumed for up to two weeks as the sole food. Nutrient profiles for an emergency food product (EFP) can and have been developed (see Chapter 2), but the required useful life of the product will be met only through careful consideration and selection of ingredients, processing techniques, and packaging materials. Key considerations include microbiological and chemical safety, dispersability, and ease of use.


The use of a few nutrient-dense products in a variety of emergencies by relief organizations such as the United Nations High Commissioner for Refugees, the World Food Programme of the United Nations, and the International Committee of the Red Cross and Red Crescent, has resulted in anecdotal information about the desirable characteristics of such foods. These characteristics should be taken into consideration during prototype development in order to develop a superior EFP. Historically, some of the most important emergency relief food products available in Europe, particularly the most successful one—the Norwegian BP-5—were not developed with food relief in mind. They were intended to be rations stowed in lifeboats for use in the event of passengers and crews having to abandon ship. Nevertheless, their use in the field during diverse emergencies, such as the Ethiopia and Eastern Sudan famine of 1985 to 1986 and the more recent Balkans conflicts, have permitted an evaluation of their efficacy from the standpoint of nutrition, acceptability, ease of delivery, and some practical aspects such as potential for diversion seldom discussed in refereed publications. The following sections provide some aspects that representatives from various relief organizations urged be considered in developing specifications for the EFP.

Packaging the EFP for Airdrop or Surface Delivery

Considering that the EFP is for use at the onset of emergencies, when infrastructure destruction and security considerations make it impossible to run feeding centers, the EFP should be available in a packaging modality amenable to low-altitude airdrop as well as delivery on land. There have been attempts to configure EFPs in ways that facilitate air delivery without damaging the product upon impact on the ground or hurting the intended recipients. Such packaging must also allow for dissemination of the product over a wide area so that it may reach many people. (Past experience indicates that concentrating the drop in the form of parachuted pallets, for example, contributed to hoarding, thus defeating the primary objective of ample distribution of the food relief, and also contributed to its diversion to unintended uses).

Packaging the EFP to Discourage Diversion

Information provided by relief organizations indicate that the high energy content of some EFPs, the density of nutrients in them, and the ease with which they may be carried has resulted in these products being collected by military combatants in emergency situations involving armed conflict. Biscuit-type EFPs are easily diverted to become military rations in emergencies involving armed conflict to the detriment of and even at a risk to the intended civilian recipients. The diversion is facilitated when the shape and size of the unit makes it easy to fit into the side pockets of military wear; rectangular, thin presentations seem to be best suited for this purpose. In addition, the use of eye-catching, glittery, space-age packaging materials encourages such diversion. It has been, therefore, the consensus among representatives of several relief agencies that the shape and size of the outside package of a successful EFP should be uncomfortable to carry in military pockets and should be made of nonlustrous materials. Furthermore, separation of the ration into smaller portions that cannot easily be rewrapped after opening also discourages diversion while aiding in apportioning the ration among children and adults.

Packaging to Facilitate Distribution and Consumption of the EFP and Reuse of its Secondary Package

Based on information from relief organizations, other anecdotal considerations for a superior EFP are the size of the unit and the potential for reuse of the secondary package. It is important that the size of the total unit and its breakdown into meal portions are designed so that adults can apportion it to individual sittings. Meal-size portions should be scored to facilitate partitioning them for children.

It is also important that the primary and secondary packages be able to serve additional uses in emergency situations. For example, a combustible primary package for emergency rations has found use in various emergencies as fuel for cooking. The secondary package may also be put to good use by recipients. For example, tin cans used to package emergency rations have been used as containers for water, as storage boxes, and even as metal shingles for building roofs after being pounded flat. In addition, from the technical standpoint, this type of secondary packaging might be very helpful in maintaining the integrity of the EFP against impact and pressure damage, insect and rodent attack, and other environmental challenges during transport, storage, and delivery. Therefore, the secondary package for the EFP should be designed such that it could afford secondary uses to the recipients.

Characteristics of Similar Ration Products

Conventional and novel technologies were considered for manufacturing the EFP. Combining some of these technologies may be the best approach to optimize the stability of the product and preserve its nutritional and sensory qualities. Dehydration, infusion, compression, and cold extrusion are some examples of processing technologies to be considered. These processes have been tested by the U.S. Army to obtain calorie-dense rations (Briggs et al., 1986; Schulz et al., 1992). A caloric density of 1.1 kcal/cc can be obtained using dehydration and compression. Higher caloric densities (up to 5 to 6 kcal/cc) are also possible using extrusion. The U.S. Air Force General Purpose (GP) Survival Packet ration for aircraft and life rafts, in turn, includes a variety of compressed bars such as a shortbread bar, a chocolate chip bar, a granola bar, and a corn flake cereal bar. The GP is designed to be consumed for periods of less than 5 consecutive days and contains approximately 100 g of carbohydrate and a low protein level (< 8 percent of calories) to counteract the effects of starvation and to conserve body water. This ration provides 1,447 kcal with 18 g of protein (5 percent of calories), 202 g of carbohydrate (56 percent of calories), and 64 g of fat (39 percent of calories). Its storage requirement is 5 years at 80º F and 1 month at 140º F (SBCOMM, 2001a).

The Meal Ready-to-Eat, Individual (MRE) is the standard military ration developed to support the individual soldier in all the U.S. Armed Forces (Army, Air Force, Navy, and Marine Corps). The MRE replaced the C Ration in the early 1980s and has since been continuously updated. It is designed to serve as the sole source of food for up to 10 days in a field environment, until group rations are available. Its use has in many situations been for longer—up to 145 days were reported during the Gulf War in 1993. Feedback from Operations Desert Shield and Desert Storm suggested that soldiers would consume more if their preferences were taken into account (IOM, 1993).

Improvements have focused on revising items to make the rations more acceptable and to expand variety (SBCOMM, 2001b). For example, the MRE bread is a pouch bread (Natick Research, Development, and Engineering Center, 1993) that contains glycerol, sucrose esters, lipids, and sorbic acid to extend shelf life up to 3 years, and has received high hedonic ratings (Hallberg and Chinachoti, 1992). This is now in every MRE ration. The average equilibrium pH and water activity of this bread are 5.0 and 0.86, respectively. The bread is further preserved by controlling oxygen content and initial microbial load (Hallberg et al., 1990; Powers and Berkowitz, 1990).

In an investigation to develop a high-energy biscuit for use as an EFP in disaster relief, low-moisture (3.5 percent) biscuits were prepared using a traditional baking method, with formulation and processing strategies as the means to control caloric density and sensory quality (Young et al., 1985). The products were highly acceptable to sensory panels made up of children both in England and India. This shows that traditional processing methods—perhaps in combination with some of the novel MRE technologies described above—can be used to produce baked EFPs such as biscuits having desirable sensory and nutritional qualities and long shelf life.

Role of Water Activity, Water Mobility, and Water Content in Packaged Food Products

Three aspects of water are important to consider in describing a food system: water activity (a w ), water mobility, and water content. Water activity is defined as the ratio of partial pressure of water in the product over that of pure water at the same temperature. The concept of a w was first put forward in the early 1950s, as a means of explaining the availability of water for chemical and biological reactions. It has been a useful tool in the food industry for many years and it is particularly useful when dealing with intermediate and high moisture biological systems (Ruan and Chen, 1998; Taoukis et al., 1988). The rate-limiting step in a chemical reaction is frequently associated with the mobility of water and its ability to participate in those reactions. At low a w , the binding of water (monolayer moisture) to components of the system makes it unavailable as a solvent. As a w increases, water exists in multilayers and is more mobile. Solvation and reactant mobility increase, so biological and chemical changes occur. This classic general relationship between moisture content, a w , and reaction rate was characterized over 30 years ago (Labuza, 1971).

Water activity is used to predict the stability of food systems and quality changes likely to occur. However, in the past 10 years there have been numerous papers pointing out the limitations of the concept (Frank, 1991; Ruan and Chen, 1998; Slade and Levine, 1991). There are practical and theoretical concerns because a w measurement assumes that the food system is at equilibrium, a condition where the partial vapor pressure above the food system is the same as that of the water within it (Ruan and Chen, 1998). Since most food systems are not in equilibrium, this frequently does not hold true.

Water mobility, as measured by nuclear magnetic resonance, is thought to be a more accurate way of determining the “availability” of water. Slade and Levine (1992) proposed the “polymer” approach to describe the role of water in food systems as a plasticizer that affects the glass transition temperature, which, in turn, could help explain the relationship between moisture and reaction rates (Nelson and Labuza, 1994).

In practice, the use of a w as a means to predict product stability remains important, while the polymer science approach can be viewed as a more generalized theoretical explanation (Reid, 1995). Water activity is a better indicator of food product susceptibility to spoilage than is water content. Dried foods normally contain 2 to 20 percent moisture, corresponding to a w in the range 0.20 to 0.60. In contrast, intermediate moisture foods (IMFs) normally contain 15 to 40 percent total moisture and have an a w of 0.60 to 0.85 (Jayaraman, 1995; Karel, 1973; Sloan et al., 1976).


Moisture control, mostly by dehydration, to lower the a w of the product is considered critical to attaining the required shelf life of the EFP of 2 to 3 years. The basic principle underlying drying and IMF technologies is the premise that water—the universal solvent—can become a limiting factor for spoilage and pathogenic microbial growth in foods when it is adequately reduced to low enough levels (Bone, 1973; Davies and Birch, 1976; Erickson, 1982; Gould, 1985; Rahman and Labuza, 1999). This reduction in moisture content and a w is sometimes accompanied by the use of other preservation factors such as chemical preservatives (e.g., antimicrobial agents, antioxidants, or antibrowning compounds), reduction of oxygen by vacuum and/or gas flushing techniques with maintenance through means of oxygen barrier packaging and/or oxygen-absorbent materials (oxygen scavengers), pH adjustment, and selection of packaging designs that protect the food from light, moisture, and environmental contamination. In the case of the EFP, moisture plays a critical role in determining microbial, sensory, chemical, and physical stability.


High-temperature, short-time extrusion cooking has been extensively applied in IMF and dried food production. Basic phenomena in extrusion cooking have been described by many (Harper, 1978, 1979, 1988; Linko et al., 1981; Rossen and Miller, 1973; Smith, 1982). In an extruder, the raw food material is subjected simultaneously to heat, pressure, and shear within a short time. Desirable product functional characteristics are typically controlled by altering the feed composition and extrusion process parameters. Water is always an integral part of physicochemical processes (e.g., gelatinization of starch and protein denaturation and plasticization) that determine the final textural characteristics of an extruded product.

Extrusion can be applied to produce foods having various moisture levels, from dry IMF products (e.g., puffed snacks and ready-to-eat breakfast cereals) to soft, moist ones. Production of modern IMFs can belong to either one of three categories: (1) moist infusion, in which solid food pieces are soaked and/or cooked in a solution having low a w , (2) dry infusion, where initial dehydration is followed by soaking the food in a solution having low a w , and (3) blending, in which the components are weighed, blended, cooked, and extruded (Erickson, 1982). Extruded IMF products are also considered thermally processed as high-temperature, short-time (HTST). This not only helps to further preserve the product from potential microbial growth and adverse enzymatic action, but also can help reduce the amount of preservatives that would be necessary otherwise. HTST processes are rapid by definition, so little destruction of vitamins or loss of protein quality are expected. According to Harper (1988), heat-stable B vitamins and pantothenic acid are stable under extrusion conditions. However, oxidation of ascorbic acid or carotenoids could occur, particularly in puffed products, so puffed processing is not recommended for the EFP.

It may be possible to hot extrude some combination of the ingredients, such as a protein and carbohydrate mixture, and then combine it with other ingredients (e.g., fat) in a compressed bar. Microencapsulation might be used for some nutrients and flavors that are mixed into a compressed bar formulation, given that most encapsulation materials are not intended for heat-processed foods. Spray coating of some ingredients after heat processing might also provide ways of incorporating heat labile ingredients during manufacturing of the EFP, as is done in breakfast cereals (Caldwell et al., 2000). Thus, the more stable vitamins might be included in the extrusion mix and others incorporated later (e.g., ascorbic acid and thiamin).

Maillard Browning Reaction

The Maillard reaction leads to brown color and to the appearance of new odors and flavors. The reaction involves reducing sugars and amino acids. It is a series of reactions that start with the formation of Amadori compounds from aldose or hexose carbonyl compounds condensing with free amino groups of amino acids or protein. The condensing product is a Schiffs base that later becomes aldosylamine, and this, in turn, is converted into ketosamines in the Amadori rearrangement. The final step involves formation of melanoidins, which are brown nitrogenous polymers or copolymers. Due to the complexity of Maillard reactions and their dependence on multiple factors (e.g., pH, temperature, composition of the medium, and moisture), it is difficult to predict the extent of browning. Sugars with different degrees of reducing power greatly influence the reaction kinetics. Water also affects it in a variety of ways. For example, a concentration of solids increases the reaction rate because of a reactant concentration effect; further concentration of solids leads to a reduced rate as the reactant mobility is decreased. In highly concentrated systems, the Maillard reaction is inhibited or retarded until, at some point, caramelization is more likely to occur than Maillard.

Generally, the activation energy of the Maillard reaction increases with decreasing moisture content, suggesting that mobility retardation may be the rate-limiting factor (Labuza and Saltmarch, 1981). There is an a w range where maximum Maillard reaction occurs that depends on: (a) the extent of the dilution effect at the high-moisture end, and (b) the limited mobility of reactants at the low-moisture end. For instance, the maximum a w range in apple is 0.53 to 0.55, whereas in dried anchovy it is 0.93 (Labuza, 1980). Unfortunately, most of the data available on reaction kinetics of the Maillard reaction is limited to a w values higher than 0.3 (Eichner and Karel, 1972; Warmbier et al., 1976). This suggests that if the EFP had an a w below 0.3, it would have an extended shelf life. Additionally, not much information is available on very high moisture systems that are believed to have slower reaction rates. From an equilibrium consideration, a Maillard reaction is not favored at high moisture because the advanced reaction and the early formation of a Schiff base involve removal of water (Hodge and Osman, 1976).

One of the nutritional implications of this reaction is a possible decreased digestibility and the loss of reactive amino acids, such as lysine (Kaanane and Labuza, 1989; Labuza 1994; Saltmarch and Labuza, 1982). This has been related to the cross linking of proteins, as demonstrated in freeze-dried meat (Barnett and Kim, 1997). In related work using an MRE chicken-a-la-king stored for 3 years between 4º and 30º C, Barnett and Kim (1997) reported that textural and sensory deterioration occurred much before the observed decrease in nutritive value. The Q10 (i.e., the increase in the rate constant as temperature is increased by 10º C) in military MREs has been reported as 3 to 4, suggesting that under abusive storage conditions, a decrease in nutritive value in terms of reduced digestibility and loss of lysine can occur.

From the lysine-loss data, an estimation of the loss in nutritive value of the proteins in chicken meat heated at 73º C for 8 days in a high concentration of reducing sugar has been calculated to be about 13 percent (Barnett and Kim, 1997). If the above Q10 is assumed for the browning reaction, heating for 8 days at 73º C would correspond to a storage for 22 years at an ambient temperature of 23º C, which exceeds the military shelf-life requirement of 3 years (ambient). Unfortunately, this information applies to chicken protein, but the EFP would contain only vegetable proteins. Therefore, the validity of this effect would need to be tested using EFP prototypes and conditions of storage and use simulating those expected during actual use of the EFP. Nevertheless, the key implication of this issue is that although the sensory quality may decrease and the nutritive value, to a lesser extent, may also be reduced because of the Maillard reaction, proper selection of ingredients for the EFP can help minimize sensory deterioration (e.g., appearance of brown color and firmer texture) and keep its nutritional quality from being adversely compromised.


Microencapsulation provides a physical barrier to oxygen, metal catalysts, and other pro-oxidants. This type of technology has been used in the food industry for many years, but a wide range of patented processes have been developed in recent years (Brazel, 1999; Risch and Reineccius, 1995). The protection of nutrients and other unstable additives is made possible by microencapsulation formulations that can allow controlled release of the nutrient during digestion as well as preserve it during storage (Deasy, 1984; Kondo, 1979). By using microencapsulation, flavor, color, and texture can be improved, thus making the product more acceptable.

The selection of shell material for microencapsulated nutrients will depend on the material being protected, processing needs, and storage stability concerns (Brazel, 1999). Capsule shell-wall materials are food additives by definition, and include polysaccharides (e.g., alginates, agarose), proteins (e.g., caseinates, zein), and fats. The water or oil solubility of the component to be protected will dictate the shell material composition (Brazel, 1999).

Diffusion of oxygen and catalysts in the aqueous matrix of a food is dependent on the amorphous or crystalline nature of the aqueous phase (Shimada et al., 1991), and it has been proposed that the glassy-rubbery transition temperature (T g —the temperature at which a rigid, amorphous, glassy material becomes molten and rubbery) plays a key role in governing oxidation of lipids embedded in the matrix (Roos and Karel, 1991). The free volume theory implies that gas diffusion through intermolecular spaces in the barrier (i.e., the continuous matrix in a dried micro-emulsion containing the oil droplets) depends on the glassy or rubbery state. As a glassy amorphous material undergoes a glass transition it gains a greater intermolecular freedom that can be described as the increase in molar free volume. A crystalline solid is a perfect barrier to diffusion and thus diffusion rate would depend on the intricacy of the barrier. In a system where water and oxygen diffusion occur simultaneously, the penetration front of water into a glassy, hydrophilic region would result in a decrease in T g , with possible swelling or other structural change (e.g., collapse) at the hydration front as the polymer relaxes, transforming into a rubbery material depending on the time frame of the relaxation process with respect to diffusion time. This is expected to have a strong influence on oxygen diffusion (Chinachoti, 1998).

Therefore, migration of oxygen and other small molecules depends on polymer chain flexibility that can “flip-flop” according to local chain mobility, which creates openings or holes for small molecules to travel through. This mobility depends on the state of hydration.

The microstructure of microencapsulated oil has been reported to be a critical factor (Hardas et al., 2000, 2002; Ponginebbi et al., 2000). Oxidation rates of surface and encapsulated lipids have been shown to follow various mechanisms depending on the physical integrity and mobility of the matrix. Hence, the effect of moisture on oxidation of surface and encapsulated lipid fractions can vary widely (Hardas et al., 2002).

Vitamins and minerals are often encapsulated to prevent unpleasant flavors and to prevent oxidation. Labile components such as fat-soluble vitamins are blended with lipids in emulsion droplets as part of the encapsulation process. Proper selection of surfactants that are antioxidants is advised, and care must be taken to ensure emulsion stability. To prevent easy moisture penetration, the encapsulation matrices should not have a low T g . However, for enhanced bioavailability, they should disintegrate upon rehydration in the mouth or upon adding water. Capsule materials that ensure release of the nutrient during digestion are usually hydrophobic fats or waxes, but some cellulose and protein derivatives can be used (Brazel, 1999).

Microencapsulation has been shown to greatly retard the oxidation of some oils that are rich in unsaturated and polyunsaturated fatty acids (Lin et al., 1995; Velasco et al., 2000). Typically, the oil is homogenized in water with the aid of an emulsifier and the resultant mixture is rapidly dried—most often in a spray drier—to yield a powdered, encapsulated product. Numerous encapsulation formulas have been tried; those that result in the highest amount of oil in the core of the particle have the best stability. Combination of antioxidants such as Δ-tocopherol (Han et al., 1991) and ascorbic acid or α-tocopherol and ascorbyl palmitate (Kaitaranta, 1992) may be used for additional protection. However, very few investigations have focused on the effect of storage and antioxidants on the oxidation of surface (free) and encapsulated lipids in microencapsulated fish oil (Velasco et al., 2000). In addition, the physical changes from amorphous to crystalline discussed above are factors that remain to be further investigated in order to improve product stability.

Coating or encapsulation is routinely done in the manufacture of fortification nutrients and flavors, but because the techniques are proprietary, it is difficult to find specific studies in the scientific literature. The primary reasons for encapsulation are to prevent interactions with other nutrients, prevent losses due to oxidation or moisture, and to minimize undesirable flavors from vitamins or minerals. The type of coating or capsule used is dependent on the compound, and to a lesser extent, the matrix (Meyers, 1998). Vitamin C (ascorbic acid) is most often coated with fat or Ethocel to provide stability against oxidation. Vitamin K encapsulated in gum acacia is available on the market.

Stable Nutrient Forms

Stable nutrient forms, other than encapsulated, may also include metal chelates such as sodium iron EDTA (NaFe EDTA), which has been shown to be effective in reducing anemia, particularly in diets high in phytates, without adversely affecting other minerals (Davidsson et al., 1994, 1998; Hurrell et al., 2000). Iron chelates have been tested in various feeding situations and found to enhance absorption of soluble iron fortificants, such as ferrous sulfate or ferrous fumarate. For example, both NaFeEDTA and Na2EDTA were effective enhancers of iron absorption from cereal foods (Davidsson et al., 2001a, 2001b; Hurrell et al., 2000). Ascorbic acid had a similar effect in high-phytate foods (Davidsson et al., 2001a, 2001b; Hurrell et al., 2000).


The addition of small amounts of solutes and dehydration are two main methods of decreasing a w and of increasing osmotic pressure in a food system to inhibit microbial growth. Reduced availability of water contributes to impaired microbial growth, and hence it has been used widely as a microbiological safety parameter (Beuchat, 1987; Gould, 1985; Lenovich, 1987; Troller, 1987; Troller and Christian, 1978). However, a w is not a universal parameter but rather an empirical one (Franks, 1982). The efficacy of manipulating a w is limited to certain types of microorganisms and is affected by food composition and environmental conditions (Andrews and Pitt, 1987; Corry, 1978; Vaamonde et al., 1982), and by the presence of microbial inhibitors (Leistner, 1995). Hence, there is no single minimum a w for inhibiting microbial growth that can be applied to all foods and all microorganisms.

It is generally accepted that bacteria are more susceptible to osmotic effects than are molds and yeasts (with some exceptions). For IMF products, the main pathogenic bacterium of concern is Staphylococcus aureus, which can produce serious food poisoning if a significant amount of its enterotoxin is ingested. S. aureus, implicated in 20 to 40 percent of all foodborne illness outbreaks in the United States (Lavoie et al., 1997), is able to grow at an a w as low as 0.85. Additionally, yeasts and molds, particularly the xerophilic kind (those that prefer dry ambient conditions), survive and grow in moisture-limited environments. The lowest a w values at which mold growth may occur, albeit very slowly, are 0.61 to 0.62 (Pitt and Christian, 1968), whereas mold sporulation does not take place at a w less than 0.75 (Pitt, 1975).

In addition to a w , factors influencing microbial survival and growth have been investigated with respect to water mobility, the translational or rotational motion of water molecules (Lavoie et al., 1997; Pham et al., 1999). It has been demonstrated that water mobility may influence transport of nutrients to microbial cells and hence growth. Under conditions of limited moisture, mold spore germination and mycelial growth strongly correlate with water mobility (Pham et al., 1999). For the EFP, the type and composition of ingredients used will influence the interaction of solids with water, thereby affecting water mobility and a w , and thus the survival and potential growth of pathogenic microorganisms. More importantly, should spores or vegetative cells of microorganisms able to withstand dry conditions survive the processing, they could germinate and grow during storage if moisture is not properly controlled in the product and other provisions, such as addition of preservatives, are not made to inhibit microbial growth. To minimize the risk of biological hazards, a multiple hurdle approach is highly recommended (Leistner, 1995). In this approach, also called the combined methods approach, several factors are used together to inhibit microbial growth, such as thermal processing, plus a w , storage temperature, preservatives, and packaging. For the EFP, it can be expected that there will be little, if any, opportunity to control storage temperature and ambient humidity. On the other hand, the cost of production and materials (including packaging) that would be incurred in making an IMF-type EFP might be too high, and there would also be a price to pay in terms of product shelf life and safety. As pointed out earlier, dehydration and IMF technologies can only stop microorganisms from growing but do not necessarily inactivate them. Consequently, and although an EFP having IMF characteristics should not be ruled out as an option, the optimal approach to the microbiological stability of the EFP would be a product design having an a w value lower than those in the IMF range (e.g., 0.4) and to add some preservatives.


Lipid Oxidation

Auto-oxidation of lipids occurs in foods largely via a self-propagating free radical mechanism. Since direct reaction of unsaturated linkages in lipids with oxygen is energetically difficult, production of the first few radicals needed to start the propagation reaction must occur through some catalytic mechanism (Nawar, 1996). It has been proposed that the initiation step may take place by decomposition to free radicals of preformed hydroperoxides via metal catalysis or heat, by exposure to light, by direct reaction of metals with oxidizable substrates, or by mechanisms where singlet oxygen is the active species involved (Nawar, 1996).

Upon formation of sufficient free radicals, a chain reaction is initiated by the abstraction of hydrogen atoms at positions alpha to double bonds followed by oxygen attack at these locations. The result is production of peroxy radicals, ROO●, which in turn abstract hydrogen from α-methylenic groups or other molecules, RH, to form hydroperoxides, ROOH, and yield R● groups that react with oxygen, and so on. Due to resonance stabilization of the R● species, the reaction is usually accompanied by shifting in the position of double bonds resulting in the formation of isomeric hydroperoxides that often contain conjugated diene groups.

Lipid oxidation gives rise to formation of a number of breakdown products, some of which are responsible for various off-flavors known as rancidity (Nawar, 1996). Even if only a single type of substrate is involved (e.g., one unsaturated fatty acid), the rate and pathway of its oxidation will depend on many factors that include its molecular structure (i.e., the number and location of double bonds), concentration, type of oxidant, oxygen tension, temperature, surface area, pH, time, physical state, and pro- and antioxidants present (Nawar, 1996).

Numerous antioxidant compounds have been studied, including α-tocopherol, α-tocopherol acetate, ascorbyl palmitate, butylated hydroxytoluene, butylated hydroxyanisole, di-t-butylhydroquinone, green tea catechins, and flavonoids, with mixed results (Lindsay, 1996). Briefly, it appears that the degree of oxidation inhibition apparently attained with antioxidants is affected by the method used to measure it and on the system studied.

Effect of Moisture on Lipid Oxidation

Although moisture reduction may discourage or inhibit microorganisms from growing in a food during storage, the moisture that remains may promote some chemical reactions such as nonenzymatic browning and enzymatic reactions. Depending on the system, these reactions are normally slowed down at low a w values, and, in general, at a w < BET1, the rates can be very slow and the product may remain in good condition through extended storage if it is properly formulated, processed, and packaged.

There is one exception, however, with respect to oxidative deterioration of lipids and fat-soluble nutrients. It has been shown that lipid oxidation can be increasingly high at moisture levels below a “critical a w ” (Nelson and Labuza, 1992a, 1992b). This critical a w value is reached when a reduction in the moisture content is accompanied by a decrease in the oxidation rate up to a minimum. At moisture levels below this point, oxidation may rise again. Thus, there is a line of demarcation for lowering a w : in the a w range of 0.2 to 0.3, lipid oxidation is likely to be accelerated, whereas at a w between 0.3 and 0.6, lipid oxidation and other deteriorative reactions are minimized. There are a number of proposed explanations for this effect that implicate the state of hydration of catalysts (e.g., metals) and hydroperoxides, phase transition, mobilization of pro- and antioxidants, and diffusion-related phenomena (Fritsch, 1994).

In the case of the EFP, oxidative changes in the lipid phase would be of concern when unsaturated lipids and minerals are present in significant amounts, for not only could they lead to adverse changes in flavor and acceptability, but also to production of toxic by-products and destruction of fat-soluble vitamins (Gregory, 1996). Therefore, although products at an intermediate moisture range may be more appealing in sensory quality, they may also be more prone to spoilage, browning, and other reactions. On the other hand, lowering the water content of the product to a dry state (< 5 percent moisture) may promote lipid oxidation. A solution to this dilemma would be to develop a dry product (< 5 percent moisture) in which lipids and pro-oxidants are kept separate by means of physical barriers, such as in encapsulation. Use of antioxidants also may be necessary depending on the level of saturation of the lipids. Additionally, the packaging method and materials used would play an important role in the oxidative stability of the EFP (Burke, 1990). The advantages of a dry product must be weighed against the fact that, for a thirsty recipient, eating it may be an unpleasant experience.

It should be noted that in the event the product is amenable to hydration before consumption, its microbiological safety should be evaluated. Potential growth of pathogenic microorganisms after rehydration—particularly if the product is not immediately consumed—could pose serious health risks, especially for recipients having impaired immune systems and vulnerable subgroups such as young children and the elderly.

Because of the above considerations, it is advisable that the lipids and pro-oxidants (e.g,. added mineral ingredients) in the EFP be kept physically separated within the product during manufacturing and subsequent storage by encapsulation of the minerals . Careful design of the encapsulation materials will be required so that they cover the intended ingredients efficiently, hold their integrity under the selected processing conditions, and disintegrate upon consumption so that nutrients are made physiologically available. Further protection against oxidation of unsaturated fats and vitamins in the EFP may be accomplished through a combination of microencapsulation, use of suitable antioxidants, development of stable emulsion prior to drying, and appropriate packaging.

Nutrient Stability During Processing and Storage

Experimental data on vitamin stability and degradation kinetics have been extensively reviewed (Karmas and Harris, 1988; Kirk, 1981; Villota and Hawkes, 1992). The nutritional quality of dehydrated foods is a function of temperature, light, oxygen, moisture, and the physicochemical state of the water (Bluestein and Labuza, 1988). The various chemical forms of added nutrients are subjected to degradation differently (Gregory, 1996). The description below reflects some major aspects of the degradation kinetics of nutrients related to the effect of moisture.

Experiments have been conducted on the effects of long-term storage at 4.4º, 21.1º, and 37.8º C, nutritional quality, oxidative and browning reactions, and sensory quality of fruit cake and chocolate brownies (Salunkhe et al., 1979). When stored in retort pouches at 37.8º C , the approximate half-life for thiamin was 30 months (fruit cake) or 15 months (chocolate brownies); for riboflavin and niacin, the half-life was less than 30 months in both products. However, the products were unacceptable due to off-flavor, dryness, and rancidity at about the half-life time for thiamin (at this point, rancidity had doubled). This indicates that the shelf life of this type of product could be less than 6 months when stored in a hot environment (e.g., 37º C), and that additional deterrents such as dehydration, reduction of a w , and others might be necessary to provide vitamin stability.

Fat-soluble vitamins, particularly vitamins A and E, exhibit stability similar to unsaturated fat. Their degradation rates significantly increase with increasing a w values from very low (~0) to 0.4. Temperature can also greatly influence their destruction; their activation energy is in the range 10 to 25 kcal/mol and decreases with increasing a w . In the presence of metal catalysts, the degradation kinetics of vitamin A are not affected if the a w is kept adequately low so that the catalyst is immobilized (Kirk, 1981; Labuza, 1971).

In the case of water-soluble vitamins, their degradation is dependent on the state of the water (free to act as a solvent for reactants and catalysts or bound) and the a w in the system. Degradation of thiamin seems to be enhanced when a Maillard-type browning is observed, which is to say, when reactants are mobile. A study by Kirk (1981) indicated that when thiamin, vitamin A, and riboflavin are used in fortification of dehydrated foods, very little degradation (< 2 percent loss) takes place at an a w in the range 0.1 to 0.4 and storage in paperboard boxes at 30º C. However, at a higher temperature (37º C), a significant decrease in vitamin retention was observed with an increasing a w over the same range. Ascorbic acid degradation studies in a dry model food system indicated that the rate of degradation of this nutrient increased with increasing relative humidity of storage or increasing initial moisture content (Purwadaria et al., 1979).

Therefore, based on the information available, some conclusions may be advanced regarding retention of nutrients that will need to be confirmed when the exact prototypes of the EFP are developed. First, to ensure nutrient retention, a w may need to be kept lower than 0.4; the lower the a w , the more stable some of the nutrients would be . This is more critical in tropical and arid areas, where storage of the EFP at elevated temperatures could accelerate the degradation process. In addition, this low a w would be in agreement with that necessary to provide protection against microbial growth in the EFP. A higher a w (e.g., up to 0.6) may be used if there are compelling reasons to do so and its influence on stability and shelf life of the EFP are determined . Second, it might be possible to apply microencapsulation technology to add additional oxygen barriers to labile components such as fat-soluble vitamins, always keeping a low a w (< 0.4) in the product. Third, for water-soluble vitamins, it is most critical that water mobility be kept low again by keeping a w adequately low (< 0.4), and that minerals are encapsulated. Minerals are unlikely to be influenced by a w , since they are stable during most processing and storage regimens.

Testing of EFPs must be conducted throughout the expected shelf life of the EFP and under conditions of delivery and storage simulating actual use, to ascertain the initial content and stability of nutrients . Standard methodologies for determining vitamin and mineral content are well described in the literature, and appropriate procedures, such as those used for nutritional labeling, can be applied to the EFP. Determining bioavailability of micronutrients from the EFP is not a feasible outcome of its development and manufacture, given the complex issue of such testing (Van Campen and Glahn, 1999).


The characteristics of a food product (i.e., appearance, flavor, and texture), the conditions under which it is consumed, and the appeal that it has for a specific consumer determine its acceptance. Measurement of liking, described below, is used during product development to predict consumer response before investments are made in equipment, production, and distribution (Stone and Sidel, 1993).

Measurement of Liking

Preference and liking are generally thought to be almost the same, and techniques used for their measurement are often similar (Peryam, 1998). However, preference implies a choice between products, without considering how well liked each one is. Therefore, measurement of the degree of liking, or “hedonic value,” is a means of determining not only whether one food is preferred to another, but how acceptable or well liked it is.

In the 1950s, considerable work was done at the U.S. Army Quartermaster Food and Container Institute to establish methodology for predicting soldiers' food choices (Peryam and Girardot, 1952). The relevance and reliability of the hedonic scale method, based on known rating scale methods used in psychology, were established through extensive field testing of army rations of all types (Peryam and Pilgrim, 1957). Since the development of the technique, the nine-point hedonic scale has been used extensively and validated by numerous studies of food products. Although there are still issues regarding its use, it remains one of the most useful tools for determining consumer acceptance (Lawless and Heymann, 1999; Meilgaard et al., 1999; Stone and Sidel, 1993).

In hedonic rating, testers are presented with a continuous or discrete scale with nine marked points, where 1 is “dislike extremely,” 5 is “neither like or dislike,” and 9 is “like extremely” (Peryam and Pilgrim, 1957). Other points are like or dislike “very much,” “moderately,” or “slightly.” Testers are asked to respond to the food product on this scale and express their honest opinion of liking. They are reassured that there is no correct answer. The data are then interpreted numerically and analyzed statistically.

Interpretation of hedonic testing results is open to debate. At what value on the nine-point scale does a product become unacceptable, and when is it an excellent product? According to Peryam (Peryam and Girardot, 1952; Peryam and Pilgrim, 1957), a hedonic rating less than 4.5 is unacceptable, while an ordinary staple food would range between 6.25 and 7.25. Interpretation is based on the food product; some items, such as candy and ice cream, would be expected to achieve averages higher than 7.25 or be poor prospects.

Prediction of food consumption is an area of continuing research in both food and behavioral sciences. Cardello and colleagues (2000) pointed out that food preference and acceptability testing may not be a successful indication of consumer behavior towards consumption. However, affective tests of liking remain an integral part of food product development and marketing. Cardello and coworkers (2000) found that predicting consumer behavior toward foods in real-life situations is difficult and that standard methods of determining liking in controlled situations may not be reliable. In the case of the EFP, it will not be possible to test the product in a real-life situation. However, testing under conditions similar to those used by the U.S. Army for GP Survival Packets and MREs is recommended .

Shelf-Life Testing

The length of time that a product is acceptable and meets consumer expectations of its quality is considered to be its shelf life (Labuza, 1982). Procedures for determining shelf life comprise microbiological, chemical, and sensory testing to give an objective point for stating that the product does not meet expected quality. In general, microbiological and sensory endpoints are used. Criteria for determining shelf life must be determined prior to starting the process. However, moisture content, a w , lipid oxidation, and vitamin losses can be correlated with sensory changes and serve as indices of stability (Giese, 2000).

A standard guide for shelf-life determination by sensory methods is being considered by the ASTM E-18 Committee (1997), which describes criteria and experimental design considerations for real-time and accelerated shelf-life testing. For products expected to have an extended storage time, such as the EFP, accelerated testing is needed (Labuza and Schmidl, 1985). The concept behind these tests is that subjecting foods to a controlled environment in which temperature or humidity, for example, is higher than normal causes an increased deterioration rate. At least one characteristic (e.g., sensory quality, vitamin content, or oxidative rancidity) must be measured analytically so that a prediction model can be built (Labuza and Schmidl, 1988; Ragnarsson and Labuza, 1977). Based on the accelerated testing, a prediction of the storage stability of the product can be made. Other models are available: Nelson and Labuza (1994) examined two models for determining the effects of a w on shelf life, while others (Cardelli and Labuza, 2001; Duyvestyen et al., 2001; Gacula, 1975a, 1975b; Gacula and Singh, 1984) have evaluated the Weibull Hazard Analysis proposed for use in shelf-life testing by Gacula in 1975.

The critical issue for the EFP is maintenance of eating and nutritional quality. Shelf-life testing for the product, therefore, should be based on both of these criteria, as well as on microbiological safety for an at-risk population. The suggestion made by the U.S. Army to use its facilities at various overseas locations to test the EFP among local populations, so that its acceptability by populations having diverse ethnic and cultural backgrounds can be evaluated, seems to be a realistic method to evaluate the prototypes.


EFP Configuration and Packaging

The EFP will be used in environments that exhibit a wide range of temperature and humidity conditions, including extreme environments, often characterized by a lack of a delivery infrastructure. Therefore, all packaging components must be capable of withstanding a wide range of temperatures (Riordan, 1970) and physical abuse. In addition, these food items will be delivered by various modes of transportation, including airdrop. Separate packaging, or more likely, additional packaging, may be necessary for EFP airdrop operations.

The first step in defining packaging requirements is to define a product configuration for product delivery and the use and protection requirements for each component. The starting point in the configuration for the EFP is a daily ration required to provide 2,100 kcal along with proteins, lipids, vitamins, and minerals to maintain nutritional status. This unit must be protected for a 3-year shelf life, and because of the product's dual susceptibility to moisture and oxygen, moisture and oxygen must be removed from the product environment before or during packaging and essentially excluded throughout its storage life. The ration is likely to be a low-moisture product (< 5 percent) that achieves microbiological stability through limited a w (< 0.4), and includes polyunsaturated fatty acids, which are prone to oxidation. Moisture should be restricted through the initial formulation. Oxygen, on the other hand, must be removed during the packaging operation by drawing a vacuum, flushing with nitrogen, or both. A high barrier to both moisture and oxygen transmission is also essential to protect the product post-packaging.

Oxidation of food components is curtailed in low-oxygen environments, as described earlier. Oxygen levels below 1 percent have been found to reduce oxidation sufficiently to provide stability for unsaturated fatty acids (Brody, 1989). Some molds can grow at oxygen levels as low as 0.1 percent and produce mycotoxins (Nielsen et al., 1989). Oxygen levels of 0.2 to 0.5 percent (2,000 to 5,000 ppm) can be achieved using vacuum and vacuum plus gas flush technologies for solid products. Initial oxygen concentrations at these levels can be obtained for porous products as well, but degassing of these products (i.e., gas losses by the product itself) may quickly raise the initial oxygen concentrations into the 1 to 2 percent range. Salame (1974) suggested that dried foods required protection to restrict oxygen gain to a maximum of 5 to 15 ppm and could tolerate a maximum moisture gain of 1 percent over their shelf life.

Acceptably low oxygen levels can be maintained only with packaging materials having sufficient barrier properties. The initial oxygen level and the upper limit of oxygen to be permitted in the package must be set in specifying actual barrier requirements. The necessary oxygen barrier to limit oxygen influx to 10 ppm over 3 years for the EFP would require an essentially perfect barrier to oxygen. More realistically, to maintain an oxygen level below 2 percent for the expected 3-year shelf life of the EFP at 23º C (70º F) in a 10×10×5-cm configuration, which yields 500 cc (450 cc for a product having an approximate density of 1.0 and a 50-cc allowance for primary wraps), and assuming a pouch surface area of 400 cm 2 , for example, and an initial oxygen concentration of 0.1 percent, sufficient barrier is achieved with a maximum oxygen transmission of 0.00088 cc/100 in 2 /day .

Such a barrier can be achieved using glass, metal, or thick films of high-barrier polymers. Glass packaging would be inappropriate for the EFP because of excessive weight, field disposal, and fragility. Rigid metal or plastic containers are contraindicated for similar reasons. This leaves flexible materials: aluminum foil, high-barrier polymers, and metalized films. The optimal choice for barrier and cost reasons is an aluminum foil laminate (Lampi, 1977; Szczeblowski, 1971).

To be sufficiently thick, high-barrier polymers such as ethylene vinyl alcohol or polyvinylidene chloride would be too costly and too bulky. “Metalized” films, in turn, can be prepared with excellent barrier properties if—and only if—the metalization completely covers the substrate. Typically, these films would be able to provide moderate, but not sufficient, barrier for use in the EFP. Therefore, aluminum foil would be the choice material.

Aluminum foils range in thickness from 4.3 µm (0.00017 in) to 150 µm (0.0059 in). By industry definition, rolled aluminum becomes foil at a thickness below 152.4 µm (0.006 in). Foils exhibit pinholes as a function of thickness. When foils are rolled to gauges below 10 µm, the incidence of pinholes increases exponentially (Anderson, 1988). Studies conducted in 1961 and 1985 showed that improvements in rolling techniques reduced the incidence of pinholes for thin foils (Anderson, 1988). For example, approximately 200 pinholes were observed per square meter with 9-µm foils in 1961, whereas a similar performance was obtained with 8-µm foils in 1985.

Foils are considered impermeable at a thickness of 25.4 µm (0.001 in) and above. At 8.9 µm (0.00035 in), the water vapor transmission rate (WVTR) is equal to or below 0.065 cc/m2 (0.02 cc/100 in2)/day at 37.8º C (100º F) (Brody and Marsh, 1997). These values drop if foil is laminated to appropriate polymeric materials. The thickness for the foil layer, therefore, could be within the range 8.8 to 18.0 µm (0.00035 to 0.0007 in), which provides the needed barrier at the lowest thickness, and therefore, at the lowest cost . Within this thickness range, foils still exhibit minor pinholes (Anderson, 1988), but lamination with polyolefin provides sufficient protection from influx of oxygen. At a thickness of 0.00035 in, aluminum foil was reported to present pinholes of approximately 0.00004 in2/100 in2. Marsh (1996) calculated that a 1-mil polypropylene coating applied to a foil substrate with an effective surface area for permeation of 0.00004 in2/100 in2 of film would exhibit reduced transmission values of 0.0076 cc/100 in2/day/atm for oxygen and 0.00002 cc/100 in2/day/atm for water vapor. These transmission rates are expected to be sufficient to maintain an oxygen level below 2 percent and to provide acceptable protection against moisture influx for 3 years at 23º C.

Aluminum foil is fragile and prone to tearing unless it is protected. A tough polymer—toughness being defined as the area under the stress strain curve (Marin and Sauer, 1954)—can provide both puncture and tear protection to aluminum foil. Two applicable polymers are polyethylene terephthalate (polyester) and polyamides (nylon). According to Lampi (1977), a 0.0005-in thick film laminated to the outside of the foil via extrusion or adhesives would provide sufficient protection: an O2 transmission rate below 1 cc/100 in2/atm/day (15.5 cc/m2/day) and a WVTR below 0.05 cc/100 in2/day. Compared to the numbers given in the paragraph above, and by current standards, these specifications for barrier properties appear to be high. However, the apparent discrepancy is easily resolved after considering that Lampi's values represented an untested level. The verification of low water and oxygen transmission was through sensory testing rather than permeation testing (Szczeblowski, 1971). Additionally, the limit of permeation detectability in the 1970s was lower than today. In 1970, the level of oxygen transmission detectability was 0.003 cc/100 in2/day (0.0456 cc/m2/day); in 2001 the level of detectability was 0.00003 cc/100 in2/day (0.0005 cc/m2/day) (personal communication, MOCON, 2001). Foil laminates, therefore, would have measured below the limits of detectability in the earlier work.

As a result of the above discussion, a trilaminate structure that has been extensively tested for long shelf-life food applications is recommended for the EFP (Lampi, 1977; Szczeblowski, 1971). Because lamination costs are related to quantity, primarily because short-run set-up charges can render lamination costs prohibitive, the trilaminate currently used by the military is recommended (from inside to outside: 0.003- to 0.004-in thick polyolefin/0.00035- to 0.00078-in thick aluminum foil/0.0005-in thick polyester [Natick Research, Development, and Engineering Center, 1993]). Other laminations with the recommended properties are also applicable, including the enhanced laminate currently recommended by the military that uses both polyester and nylon for additional protection against distribution (mechanical) forces. The package should be nitrogen flushed, and residual oxygen must not exceed 0.5 percent .

A notch in the package seal must be provided to facilitate opening by EFP recipients, who would likely have no scissors or other tools at their disposal .

Individual EFP Bars

Although the EFP has been designed to provide 2,100 kcal/day to recipients as a daily ration of approximately 450 g, it should be divided into smaller units for a number of reasons. First, considering that most people would normally eat more than one meal during the course of the day, dividing the daily ration into smaller portions provides for multiple meals. Second, it facilitates feeding children who need smaller amounts to meet energy needs. Third, it helps prevent the entire ration from being exposed when only part of it is going to be consumed. Therefore, it is suggested that the ration be divided into equal portions having the shape of bars . To facilitate packaging, nine bars would be appropriate. To further facilitate division of portions for young children, each individual bar should be centrally scored across the width of the bar to provide two 116-cal portions upon breaking it .

Each one of the nine bars should be wrapped in a primary packaging defined as the package that is in intimate contact with the product (Saroka, 1999)—that does not need to be a barrier material. (Lampi [1977] defined the pouch and carton used for retort pouches as the “immediate container” in the EFP application, the immediate container would include this primary wrap, the barrier container for each daily ration, and the bundling bag for multiple days or people.) It is recommended that this primary wrap be pulp-based and have a moisture-barrier coating. Individual bars could be wrapped in polyethylene or wax-coated paper (Fennema and Kester, 1991) as an unsealed wrapping similar to the inner wrapping of a candy bar. This wrap would provide a minor moisture barrier for individual bars after the EFP trilaminate is opened. More importantly, it would separate individual bars for easier access and would prevent microbial contamination from insects, handling, and surroundings. In addition to separating individual bars, the wrappings could be used by refugees or victims of emergencies to start fires for cooking or providing heat.

The secondary packaging is defined as that which bundles the primary packages (Saroka, 1999). A daily supply of nine bars should be packaged together under a nitrogen flush or vacuum into a barrier package to provide the barrier against oxygen and moisture needed for extended shelf life. The secondary packaging could be a pouch having a similar construction to that of the trilaminate pouch utilized by the military for long shelf-life rations, which consists, from the inside out, of polyolefin, aluminum foil, and polyester or nylon (defined above). This daily supply is considered a “unit.”

Five-Day EFP Package for Distribution

Anecdotal evidence provided by relief agencies indicates the convenience of grouping five daily rations into a single bundle. The rationale for this selection is that it permits 5 days worth of food for a single individual or 1 day of feeding a five-member family to be distributed as a unit. In addition, it is desirable to have a distribution-bundled package that is not easily carried by soldiers or personnel for which the EFP is not intended. Therefore, it is recommended that five EFP daily rations be bundled into a monoaxially- or biaxially-oriented polyolefin bag. The bag should be notched to facilitate opening .

A rigid container could be used for the bundling instead of the polymeric bag. This could be a rigid plastic or metal container. Although such containers would add weight, they offer additional protection against rodents and may also serve additional purposes after consumption of the EFPs, such as carrying water. This option becomes especially attractive if such use (e.g., as a water carrier) replaces or precludes a separate delivery of such items.

Shipping Containers

Eight bundles of five EFPs each will be placed into a shipping container to constitute a case. The shippers could be of corrugated construction, sufficient to pass distribution protocols of ASTM International or the International Safe Transit Association . Their dimensions will depend upon the actual shape of the bars, which is not specified in this performance-based recommendation. It is anticipated that single-wall, C-flute corrugate would suffice. Each shipper will weigh in the vicinity of 40 lb. Shipping containers could also be constructed of metal so that they can be recycled for use as storage or water containers as suggested by anecdotal evidence.


Shippers will be assembled onto a pallet for transport. Pallets will be of construction and dimensions to provide efficient transport, with overhang and underhang restricted to a maximum of 2 in . Approximately 50 cases will be placed on a pallet. Pallets may be unitized using stretch wrap, banding, adhesive, or other means.


Naked Rations

Depending upon the ultimate shape and density of the EFP, it should be possible to airdrop individual EFP packs in ways similar to MREs, using the Triad (tri-wall aerial distribution system) that was used to airdrop food in Bosnia (Roos, 1993). Individual MREs were found to fall with a terminal velocity of 58 mph, which was suitable for delivery. The tri-wall distribution container was used to transport the MREs, but was not included in the drop. This method may be applicable if the terminal velocity of the EFP is found to be sufficiently low to allow for safe delivery. However, given the caloric density requirements of the EFP, it is anticipated that it will be a heavy product such that additional packaging protection will be required for air delivery in this manner.

Flutter Packs

The World Food Programme developed a plastic film tube package with unequal amounts of food product sealed into each end. The length of tube between the product catches air during free fall and slows the descent. The unequal product weights cause a precessing (whirling) motion that absorbs energy during the free fall, thus the package name. However, because the weight of product delivered using this system is less than that of the EFP, its applicability for EFP delivery must be tested.

Wing Packs

Alternate configurations to the Flutter Pack may be developed that provide sufficient wind resistance to slow descent to a safe level.

Bubble Packs

Bubble packs or suitable cushioning material may be layered such that impact is attenuated as successive layers absorb impact and rupture. This would constitute an individual pack adaptation of the airbag approach that has been developed for bulk delivery (see below). Dimensions of bubbles, pressure of enclosed gas (which would change with altitude), and strength of substrate that will rupture must all be determined to prove efficacy for specific ration configurations (single or multiple) and specified drop heights. Drop height may be extended if terminal velocity is acceptable.

Cushion Packs

Additional cushioning materials may be employed to attenuate impact to acceptable levels for EFP delivery. These cushions could be composed of a variety of materials (thermoset or thermoplastic foams, rubber, cellulosic), composites, or constructions (such as paperboard honeycomb, mentioned below). Two considerations are required for suitability, however: the integrity of the EFP and the safety of the delivery. Unless remote delivery is assured, the airdrop must not present a hazard to the intended recipients.

Bulk Drops


The steady descent velocity experienced with parachute airdrops is about 28 ft/sec (Lee, 1992). Ground impact at this velocity requires an energy absorber to dissipate the impact energy. An evaluation of cushioning materials by Ellis and coworkers (1961) concluded that paperboard honeycomb was the most cost-effective, all-around, airdrop, energy-dissipating material. A majority of U.S. Army airdrops are delivered by the Container Delivery System, which has a 2,000-lb payload and uses honeycomb protection. Other cushioning materials may also prove adequate, but any material will require evaluation to assure proper loading and effectiveness under the environmental conditions that may be expected during the airdrops .


The U.S. Army evaluated alternatives to cushions because of specific short-comings. Cushioning materials take up substantial warehouse space, are labor-intensive to use (primarily for equipment loads that require assembly, but would be less of a concern with uniform loads for items such as the EFP), and may degrade in high humidity (especially the paperboard honeycomb). Foams offers an alternative that overcomes these difficulties (Goldberg, 1990). As mentioned above, testing would be necessary to determine loading and use conditions.

Air Bag

Another option for airdrop impact reduction is air bags. This option utilizes the restricted venting of the air bag to reduce impact forces. Complex air bags using vent control and/or gas injection, and augmented air bags using paperboard honeycomb or other cushioning, have been found to improve the performance of simple air bags by decreasing peak gravity forces (Lee, 1992). Such systems offer further alternatives for bulk air drops of the EFP that could be evaluated when prototypes are prepared.


The goal of this report is to develop an EFP that has an optimal nutritional profile and could meet the most severe environmental, storage, and logistic conditions. However, it is recognized that the requirements to produce such a sophisticated product are substantial. If funds are limited, a high unit cost can dramatically reduce the quantity of rations available to a needy population. Given this concern, the technical specifications recommended in this report should be considered optimal; however, the sponsoring agencies may choose to consider developing EFPs prepared and packaged to less stringent specifications if cost becomes a primary consideration. Under these circumstances, an EFP packaged in airtight foil bags inside a water-repellent paperboard box, for example, would allow greater quantities of products to be procured for a fixed cost and would be adequate in many relief situations, particularly for disaster relief. However, in this case, the long shelf-life objective and possibly also the goal of prepositioning supplies around the world would have to be modified by the agencies.


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Brunauer-Emmett-Teller value, normally 4 to 5 percent moisture (Brunauer et al., 1938).

Copyright 2002 by the National Academy of Sciences. All rights reserved.
Bookshelf ID: NBK220578


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