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Quality improvement of frozen fruit by changing the vitreous transition temperature.

Miglioramento della qualita's di frutta congelata mediante modificazione della temparatura di transizione vetrosa.

Author(s) : TORREGGIANI D., BERTOLO G.

Summary

Vitreous transition is one of the key factors in the osmotic dehydration (i.e. dehydration-impregnation in concentrated solutions: DIC) of fruit before freezing. The hypothesis is that the stability of a food product can be improved if its storage temperature is as near as possible to its vitreous transition temperature. The vitreous transition temperature is the transition from "rubbery" state to vitreous (amorphous and meta-stable) state. The authors describe the procedures and results of tests carried out on a model system in the IVTPA (Institute for the valorisation of agricultural produce technology) of Milan (Italy). They studied the effect of the composition of strawberry juice, pure and with various sugar additives, on the vitreous transition temperature of non-frozen phase. This factor conditions the stability of anthocyan pigments all through the cold storage time. The tests showed that the total anthocyan content significantly decreased in the course of storage at -10 °C and that the addition of sugars increased the retention of such pigments. The main protective effect was obtained with maltose and sorbitol for 4-month storage, with sorbitol only for 8-month storage. The higher was sugar concentration, the better was anthocyan retention. These test results were confirmed by other research on kiwifruit. Nevertheless, the protective effect of sorbitol on the anthocyan content of strawberries (and apricots) cannot be explained using the concept of vitreous transition temperature alone. Further research is in progress on other factors, such as pH and sorbitol structural characteristics.

Details

  • Original title: Miglioramento della qualita's di frutta congelata mediante modificazione della temparatura di transizione vetrosa.
  • Record ID : 2000-2649
  • Languages: Italian
  • Source: Le ultime tecnologie del freddo e del condizionamento./ Latest technologies in refrigeration and air conditioning.
  • Publication date: 1999/06/18
  • Document available for consultation in the library of the IIR headquarters only.

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