Effect of freezing rate on the kinetics of freeze drying and rehydration of apple slices

• Grant number: 10/04245-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: August 01, 2010
• End date: January 31, 2013
• Field of knowledge: Agronomical Sciences - Food Science and Technology - Food Engineering
• Principal Investigator: Vânia Regina Nicoletti Telis
• Grantee: Natalia Guardia Corrêa
• Host Institution: Instituto de Biociências, Letras e Ciências Exatas (IBILCE). Universidade Estadual Paulista (UNESP). Campus de São José do Rio Preto. São José do Rio Preto , SP, Brazil

Abstract

The use of new processing technologies, which permit keeping the quality attributes of the product at similar levels of those observed in the raw material, has permitted to obtain dehydrated fruits with sensorial aspects appreciated by consumers and contributed to extend their availability for periods beyond their harvest season, allowing their consumption during the whole year. Among the dehydration processes that result in products of good sensorial and nutritional attributes, the freeze drying, in which the water separation is based on the sublimation phenomenon, has an outstanding position. Taking into account that the freezing conditions exert influence on the physical properties and on the quality and nutritional attributes of freeze dried products, the objective of this work is to study the freeze drying of apple (Malus domestica) slices of the Gala variety, evaluating the effects of the samples' freezing temperature and slices' thickness on the freezing rate, drying kinetics, rehydration kinetics and on some quality attributes (texture, color, and vitamin C retention) of the final dehydrated product. In addition a comparison of the mentioned quality attributes will be carried out between apple dried by freeze drying, conventional drying with forced convection at 60 ºC, and vacuum drying at 60 ºC. (AU)