关键词: 低水分活度食品, 椰菜粉, 射频, 杀菌

Abstract:

Recently, the safety of food with low water activity (aw), including dried vegetables powder, has been a major concern of the people. Although the microorganism could not grow in low aw foods, it can survive for a rather long period of time. Once the environment becomes suitable, a severe food safety problem would occur. Therefore, it is necessary to develop decontamination methods to improve the safety of low aw foods. Taking broccoli powder as material, this paper disinfected 27.12 MHz pilot scale RF system by 6 kW radio frequency (RF), and studied the heating pattern and temperature distribution during RF heating. It was found that the temperatures in the interior and central parts of the sample were much higher than that in the surface. Overturn and rotation during RF treatment was proven effective to improve the heating uniformity. This paper also studied the situation of microbial reduction and color change of the sample during different periods of RF heating. The results showed that RF heating for 5 min had a high efficiency in microbial inactivation with insignificant color degradation. The cold shock treatment (freezing at -18℃ for 48 h) following RF heating could further reduce microorganism in broccoli powder from 3.0 log CFU/g to less than 1.0 log CFU/g. Cold shock combined with RF heating is a promising disinfection technology for food of low aw. It can preserve to the large extent the original superiority of low moisture foods.

Key words: low water activity food, broccoli powder, radio frequency, disinfection