Application of Microwave Vacuum Drying in Processing of Agricultural Products

1. Microwave Vacuum Drying technology has the characteristics of low processing temperature, low nutrient loss rate and high dehydration efficiency. Therefore, the advantages of fruits and vegetables with high water content can be played in dehydration processing.
In 1979, citrus powder produced by microwave-vacuum technology on an industrial scale in France had foam and was easily dissolved. Its natural color, fragrance and taste are maintained well, and the vitamin retention rate is much higher than that of spray drying. The research of the University of California uses microwave vacuum drying technology to produce Dehydrated expanded Grapes, Dehydrated Vegetables, etc., which can maintain the flavor and color of fresh grapes well, and the shape will not shrink. 
Due to the low microwave drying temperature and short drying time, vitamin B1, vitamin B2 and vitamin C can Get a higher retention rate. The dried garlic was dried by hot air drying, vacuum drying, freeze drying, microwave vacuum drying and vacuum drying. The results showed that the drying time of microwave vacuum drying and vacuum drying at 40 ° C was greatly shortened, and the sulfur of garlic after drying was dried. The retention rate of sulfinate is relatively close to freeze-drying, which can reach 90%. The difference in color difference from vacuum freeze-dried garlic is very small, even slightly better than the whiteness of freeze-dried garlic. However, the only drawback is that the structure of garlic is not as tight as freezing. Dry and loose. The large amount of by-product pumpkin slag obtained when processing pumpkin juice was microwave vacuum-dried under different microwave power and pressure conditions. It was found that the retention rate of carotene in the material was high at 92.37W and 4000Pa, reaching 92.31%. Using microwave vacuum drying and puffing technology to process apple chips, the purpose of drying and puffing apple slices can be achieved in a few minutes at 40 °C, greatly improving the production capacity, the product is beautiful in appearance, good in color and flavor, crisp in taste and high in nutrients. It realizes the rapid, low temperature and non-fried puffing processing of apple chips. The process of making instant banana powder by sterilizing banana juice after enzymatic hydrolysis by microwave vacuum drying equipment was studied. It was found that many indexes of products after microwave vacuum drying were superior to those of hot air drying. Based on the microwave vacuum drying experimental equipment developed by Guangdong Agricultural Machinery Research Institute, the author studied the microwave vacuum drying characteristics of pineapple powder. The test results show that pineapple powder products maintain the original color, aroma and vitamin C of pineapple. Such as nutrients, the moisture content is below 5%, and the solubility is good.

2. Application in aquatic product processing Microwave vacuum drying technology also has great development potential in other food processing fields. At present, there has been a microwave vacuum drying of shrimp, and microwave vacuum dried shrimps were compared with hot air dried and freeze-dried shrimps. It was found that the shrimps dried by microwave vacuum were smaller than the hot air drying shrinkage. Water and moisture retention, and close to rehydrated frozen shrimp in terms of color, texture and flavor. Zhang Guofan and others used a microwave oven to dry the scallops. The results showed that the dried scallops, color, aroma, taste and drying time all achieved satisfactory results.