Study of thermal intermittence and edible coating application to papaya drying and its effects on process efficiency and product quality

Abstract

The problem to be addressed in this proposal is the substantial loss of nutrients, besides other quality issues that occur in fruits during the conventional hot air drying, an extensively used method due its relative simplicity. The proposal consists in the determination of operational conditions in a rational way to the drying process in order to minimize nutritional losses and energy consumption. This methodology is complemented with the use of edible coating applied prior to drying, which partially protects the product from contact with oxygen during the process. Therefore, the beginning of the project will consist on a detailed literature review about the characteristics of edible films most used in food products, from which will be selected a film with suitable properties for the application as edible coating prior to convective drying. The object of study will be the papaya (Carica papaya L.), a tropical fruit that presents substances with good nutritional value, such as carotenes, vitamin C and mineral salts. Dehydration at low temperatures can preserve a great amount of vitamin C from papaya, however, this leads to long drying periods. The intermittence will consist of temperature modifications in such a way that the product temperatures will not exceed predetermined values and will reduce the drying time. Tempering periods, during which the drying is interrupted, will also be tested. During the tempering, the moisture is transferred from the center of the solid to the surface, after which the drying is resumed. The establishment of the intermittence operational conditions will be determinate by measuring temperatures on the solid surface and the kinetics of vitamin C degradation during the initial drying period. Then the coating effect and the different types of drying operation (with or without intermittence) on the reduction of time process and on the physical and nutritional characteristics of the final product will be evaluated. To assess the quality during the storage, accelerated shelf life tests will be conducted on covered and uncovered dried papaya pieces. (AU)