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Food Chem. 2020 Jul 1;317:126381. doi: 10.1016/j.foodchem.2020.126381. Epub 2020 Feb 10.

Impact of thermal pretreatment on crystallization of Thompson raisins.

Author information

1
Centro Regional de Estudios en Alimentos Saludables (CREAS), Valparaíso, Chile. Electronic address: lalvarez@creas.cl.
2
Centro Regional de Estudios en Alimentos Saludables (CREAS), Valparaíso, Chile; Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
3
Centro Regional de Estudios en Alimentos Saludables (CREAS), Valparaíso, Chile.
4
School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia.
5
RMIT University, Bundoora Campus (West), Melbourne, VIC 3083, Australia.
6
Centro Regional de Estudios en Alimentos Saludables (CREAS), Valparaíso, Chile; Departamento de Ingeniería Química y Ambietal, Universidad Técnica Federico Santa María, Valparaíso, Chile.

Abstract

After prolonged storage or during the shipment of raisins, a crystalline material may be developed on their surface, affecting the final acceptability of the product. The mild thermal pretreatment (50 °C for a period of 12 h and 48 h) was applied to dissolve any potential tiny crystals and nuclei already present in the raisins. The thermal pretreatment of raisins resulted in a reduction on the percentage of crystallized raisins (w/w) from more than 46% in control samples to less than 10% after 30 days of storage at 57% and 66% of relative humidity and 15 °C and 25 °C. X-ray diffraction analysis identified d-Glucose monohydrate as the main crystalline component. All the thermal treatments increased the hardness of the raisins, when they were incubated at 57% relative humidity. To mitigate the problems of crystallization of raisins during shipping, it is recommended that the raisins are thermally pretreated and the shipping conditions are controlled.

KEYWORDS:

Chilean raisins; Crystallization; Relative humidity; Sugaring; Temperature

Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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