Due to the high moisture content of vegetables and fruits, the cost of microwave drying of fruits and vegetables is extremely high, while microwave vacuum drying has the disadvantage of dehydration of vegetables and fruits.
Have greater potential. So far, the application of microwave vacuum drying technology has focused on the drying of vegetables and fruits.
Its application in food production is still relatively small. For example, the University of California and the California Pacific Gas and Electric Company have cooperated for many years.
The use of microwave vacuum drying technology to produce dehydrated puffed grapes [14], can maintain the flavor and color of fresh grapes well, and the shape of the grapes is not
Shrinking, the fresh grape has a 25% yield. When drying grapes with microwave vacuum drying equipment, due to its low drying temperature and short time,
The original vitamins B1, B2 and vitamin C can achieve a high retention rate. In addition, the use of microwave vacuum drying equipment to process seedless
Raisins, the traditional process hot air drying (65 °C, 24 h) into microwave vacuum drying (50 °C, 5 h), so that the product quality is greatly improved.
France uses the microwave vacuum dryer (2 450MHz 48kW) manufactured by International Microwave Company to process instant orange powder.
The color, aroma and taste of the vitamins are much higher than those of spray drying . Drouzas and Schubert
Used to dry by microwave vacuum technology Banana slices, the results show that there is no uneven heating during the drying process, by adjusting the vacuum and microwave output intensity,
It can control the product temperature and drying rate, and the processed products have obvious indexes such as taste, flavor and rehydration rate compared with traditional methods.
Better than other drying methods. Yongsawatdigul and Gunasekaran
The microwave vacuum drying study of the acid raspberry was carried out, and the results showed that The microwave can be used to intermittently control the vacuum to further improve the uniformity of microwave heating. The intermittent wave is more efficient than the continuous wave.
In addition to speeding up the drying rate, the internal vapor pressure difference can also prevent the shrinkage of the dried product, and the pores can be formed by capillary action.
The tissue increases rehydration. Lin applied microwave vacuum drying to the drying of carrots and found that compared with hot air drying, microwave vacuum
The drying time is greatly shortened, and the oxygen content is low, and the loss of carotene is small. Yousif et al. [17] analyzed in depth the different drying methods.
The effect of the formula on the flavor and texture of the flavor, and found that the product of the microwave vacuum dried product has aroma and texture and fresh or Compared to freeze-dried products, there is no significant difference, and it has good color and rehydration ability. Therefore, microwave vacuum drying is completed.
It can replace costly and time consuming freeze drying. In addition, Drouzas and Schubert Yongsawatdigul and Gunasekaran, Kiranoudis .The research on drying fruits and vegetables by microwave vacuum was also carried out, and the results showed that microwave and vacuum dried fruits and vegetables
The retention rate of color, aroma, taste and heat sensitive ingredients is very close to that of freeze-drying, but the texture of dried fruits and vegetables is hard.
There is a certain gap with freeze-drying, but the drying time and production cost can be greatly reduced.
Microwave vacuum drying technology also has great potential in other food processing fields.