Aassociation drying Method for preparing dehydrated vegetable and fruit

Abstract

The invention relates to a dehydrating and drying method for the top-grade vegetable and fruit. After being sliced, the vegetable and the fruit are placed in a microwave vacuum dryer for being dried, the exerting microwave power density is between 0.5 w / g and 1.2 w / g (watt / gram), the vacuum rate is between 2.5KPa and 4.5KPa (remaining pressure), the materials to be dried can do reciprocating movement along with the drying dish in the microwave vacuum dryer. After being dehydrated by about 40-50 percent of the total moisture by the microwave vacuum drying, the materials are taken out and positioned on a stainless steel dish and then are positioned in a freezing dryer, and are frozen and sublimed dry under 25 DEG C below zero, the drying time is about 7-10 hours, and the moisture is lowered to the safe moisture of 6-7 percent. The preserving of the color, the scent, the taste, and the nutritious components of the dehydrated vegetable and fruit which are produced by the invention are quite approximate to that of the single freezing dried products, the volume is 60-70 percent of the volume of the single freezing dried products, the appearance and the organic structure are approximate too, the drying cost is low, and the energy can be saved by 40 percent above.

Description

technical field [0001] The invention relates to the field of food and agricultural product processing, in particular to a dehydration processing method for fruits and vegetables. Background technique [0002] Among many drying methods, due to high drying temperature and long drying time, hot air drying results in poor quality of dried food, large color change, large loss of color, fragrance and nutrients, hard tissue structure and poor rehydration; traditional vacuum Although the drying temperature is relatively low, since the convection heat transfer in the drying room is almost non-existent, but the heat conduction is the main method, so the heat transfer speed is slow, the drying time is still relatively long, and the retention of color, fragrance and nutrients is still limited. The tissue structure also hardens, and the rehydration property is also poor; the drying quality of freeze-drying is the best, it can basically retain the original color, aroma, taste and nutritio...

AI Technical Summary

Problems solved by technology

[0002] Among the many drying methods, hot air drying has a high drying temperature and a long drying time, which leads to poor quality of dried food, large color changes, large loss of color, fragrance and nutrients, hard tissue structure, and poor rehydration; traditional vacuum drying Although the drying temperature is relatively low, since the convective heat transfer in the drying room is almost non-existent, but mainly heat conduction, the heat transfer speed is slow, the drying time is still relatively long, and the retention of color, fragrance and nutrients is still limited. The tissue structure also hardens, and the rehydration property is also poor; the drying quality of freeze-drying is the best, it can basically retain the original color, aroma, taste and nutritional components or biological activity of the food, and the shape of the product after drying is basically unchanged , the tissue structure is porous, good rehydration

In the processing of high-grade dehydrated vegetables, fruits and other foods, the drying process is the key to determine the product quality. At present, high-grade dehydrated fruit and vegetable products are all produced by freeze-drying process. Traditional drying processes cannot produce high-quality dehydrated fruits and vegetables.

However, freeze-drying is not only expensive in equipment, but also high in operating costs. It needs to maintain a low temperature of -25°C, a high vacuum of 0.5Kpa, a drying time of about 20 hours, and a limited production capacity, so the production cost of the product is very high.