Influencia de la temperatura, el envase y la atmósfera en la conservación de uvas pasas y de albaricoques deshidratados

Abstract

This study addresses the evolution of dehydrated foods during its storage. The general objective is determination of shelf life of the foods submitted to different conservation processes and analysis of the influence of the conservation conditions on their shelf life. Packages based on polypropylene trays thermosealed with polymeric material and glass flasks and nitrogen and air as inside atmospheres were used. The storage temperatures ranged from 5ºC to 40ºC. The evolution of the moisture content during the preservation has been modelled considering the exchanges with the environment and the production of water due to Maillard reactions, obtaining a good correlation. The most drastic changes in the characteristics of the product have been observed at the highest conservation temperatures. The SO2 content and moisture can be depicted by means of a first order kinetics. An important decrease was observed in the SO2 content, leading to a more intense browning. This decrease was also observed in the moisture in samples packaged in trays thermosealed with film. On the contrary, in the case of samples packaged in glass, a small increase in the content of moisture was observed at high temperatures. This could be interpreted as a result of the water generated in Maillards reactions. Due to the highest reactivity of glucose regarding fructose in these reactions, the browning of the samples is accompanied by an increase in the ratio between fructose and glucose contents. With regard to the texture, for the samples packaged in films, the value of maximum force increases with the temperature, along with a moisture decreases. For the samples packaged in glass, the values remain almost constant at the lower temperatures and increase slightly at higher temperatures. The fact that at the temperatures of 35 and 40ºC the moisture of the samples hold in glass containers increases and however the texture suffers a slight increment, could be explained by the appearance of changes in the structure of the product between 25 and 35ºC. A calorimetric analysis of the dried products considered was also carried out, obtaining a second order phase transition at 32 + 1ºC. As a result of this study a set of shelf life values are proposed for each storage conditions-product group.