脱水蔬菜粉射频杀菌研究

近年来，低水分活度食品包括果蔬粉等的安全性开始受到人们的广泛关注。虽然微生物在低水分活度食品中无法生长，但是可以存活很长一段时间，且一旦条件适宜将会引发严重的食品安全问题。因此，急需建立适宜的方法对低水分活度食品进行杀菌以提高其安全性。以椰菜粉为原料，用功率为6 kW,频率为27.12 MHz的射频设备进行杀菌，研究其在射频过程中的加热模式和温度分布，发现样品内部和中心的温度明显高于表面温度，这可以通过加热过程中样品的翻转来改善。并研究了射频处理不同阶段椰菜粉的微生物失活及颜色改变情况，结果表明经射频处理5 min后微生物失活显著，且颜色基本不变。射频处理后的冷激（-18℃，48 h）可将微生物从3.0 log CFU/g降低到低于1.0 log CFU/g。射频与冷激相结合是一种很有前景的低水分活度食品杀菌技术，且具有最大限度保持食品原有品质的优点。

Studies on Radio Frequency Heating to Inactivate Microorganisms in Broccoli Powder

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.