Comparison and analysis of the quality of the hott

2022-09-23
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Comparative analysis of the quality of vacuum freeze-dried and heat dried bamboo shoots (Part 2)

2 results and discussion

2.1 comparison of sensory quality

vacuum freeze-dried bamboo shoots are white, soft tissue, good taste after rehydration, no lumps and difficult to chew, with the freshness and smell of fresh green bamboo shoots. The hot dry green bamboo shoots are dark in color, and their hands feel hard at the end of June this year. The original taste of green bamboo shoots is insufficient, with a certain cooking taste. Moreover, the surface of the products is hardened and dry, so it is difficult to rehydrate to the fresh state of the raw materials (see Table 1 and table 2)

from the results in Table 1 and table 2, the color of vacuum freeze-dried bamboo shoots is much lighter than that of heat dried bamboo shoots, and is close to the color of fresh green bamboo shoots. The hot dried bamboo shoots are red in color and low in brightness. This is related to vacuum freeze-drying of Lentinus edodes and Hami melon. And so on

2.2 comparison of water content and rehydration

the water content of vacuum freeze-dried and heat dried dried dried bamboo shoots is required to be 2% - 5% according to the water content of the product. In this experiment, the corresponding water activity of the product stored for 6 months is 0.351 and 0.479 respectively, while the water content is 3.25% and 4.68% respectively. Dried vegetables generally need to be rehydrated before cooking and eating. The degree to which they return to their original fresh state after rehydration is one of the important indicators to measure the quality of their products. The main factors affecting the rehydration of dried vegetables are material composition, texture, rehydration temperature, processing temperature and rehydration volume. After 10 minutes of rehydration, the rehydration ratio of hot dried bamboo shoots is r heat =1.01, while the rehydration ratio of vacuum freeze-dried bamboo shoots is r true =7.68, indicating that freeze-dried bamboo shoots can quickly and completely re absorb water and recover, which is convenient for eating. It does not need too long time to rehydrate, and normal temperature water can be cooked and eaten in a short time; Heat therefore affects the accuracy of the experimental data. Dried bamboo shoots can't be eaten at all after rehydration for 10 minutes. The rehydration ratio after 3 hours is only R heat =5.55, which was also confirmed by Cui Fuxiang and others in the study of vacuum freeze-drying spinach

2.3 camp, which will show an additional significant cultivation score comparison in this year's K exhibition

due to the cleaning, cutting and scalding processes in the processing of dried bamboo shoots, there is a certain loss of nutrients. In this experiment, the two kinds of dried bamboo shoots and fresh green bamboo shoots are compared from the content of water-soluble total sugar and heat sensitive VC. The results are shown in Table 3

Table 3 Comparison of nutritional components between vacuum freeze-dried and heat dried bamboo shoots. It can be seen from table 3 that the total sugar and Vc content of vacuum freeze-dried bamboo shoots are higher than that of heat dried bamboo shoots, and the total sugar is not much different between the two. The VC content is much higher, while the VC content of vacuum freeze-dried bamboo shoots is close to that of fresh samples, and the relative loss is relatively small

3 conclusion

(1) vacuum freeze-dried bamboo shoots completely maintain the original shape and color of fresh green bamboo shoots, and have good rehydration, which can quickly re absorb water and recover, and their quality is basically the same as that of fresh bamboo shoots. While hot dried bamboo shoots are the opposite

(2) because vacuum freeze-drying dried bamboo shoots are dried at a very low temperature, there is little loss of nutrients and flavor substances in dried bamboo shoots, which can maximize the original nutrition, taste and aroma of fresh green bamboo shoots

(3) compared with hot dried bamboo shoots, vacuum freeze-dried bamboo shoots are small in size and convenient for transportation under the same weight

(author/xiaolixia 1, Yan Shijie 2, Liu Ye 2, Hu Xiao 2 put the tested spring on the lower pressure plate or hang it between the upper and lower hooks and loosen 2

1 (School of food science and engineering, Yangzhou University

2 (School of food science and Nutritional Engineering, China Agricultural University)

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