Strawberry Freeze-Dried Product Of Process And Testing Methods

Vacuum drying is a method of evaporation from food under low-pressure, low temperature to obtain higher quality food. And then we put Principle of ice sublimation with vacuum drying method together. In high vacuum conditions, the water in frozen food without passing through the melting of the ice sublimates directly from solid ice to water vapor to dry the food products. This process is vacuum freeze-drying technique. Products which is after vacuum freeze-drying process can keep most part of nutrition, flavor, colour and thermal components. The lost is very limited. The materials in sublimation and dehydration after freeze can form a stable solid skeleton, so the solid skeleton remains unchanged after the sublimation. That is why dry products without losing the original solid structure maintain the original form. The porous structure of the products has very good instant and rapid rehydration. With the rapid development of economic, vacuum freeze-drying technology can apply in the pharmaceutical, medical, food industry, chemical industry and many other fields. The application which is popular in market is a lot, such as instant coffee, instant milk powder and some other instant convenience foods. And they are all being subjected to consumer pro-gaze. Vacuum freeze-drying products supply great convenience to people’s lives and work.This essay is discussing the best freeze-dried process flows of Vacuum freeze-dried sliced strawberries and the food additive in the products. The purpose is that to supply Theoretical and practical basis for the industrial production and supervision departments to supervise dried strawberries products. The research is including 4 parts below:1) The research of process flows of Freeze-dried strawberriesRelated data of experimentation are below: - Eutectic point: -21℃～-23℃- Degree of ripeness of strawberries: 80%-90% - Size of strawberries: 6-8mm - Time of protective coloration with Colour retention agent: 10 min. - Time of pre-freeze: 30 min. - Time of Vacuum freeze-dried: 21h. The other influence factors of Vacuum freeze-dried method of strawberries have been studied as well.2) The research of Rehydration test The curves of dehydration rates under different temperatures are drawn which are based on the detection of dehydration rates.3) The research of detection method of vitamin C content in the productsWe use fluorimetric method and Colorimetry method to detect the content of vitamin C in Vacuum freeze-dried sliced strawberries. The procedure is looking for the conditions, feasibility and applicability of experimentation. And the best method and conditions of this product are decided at the end of experimentation4) The research of detection method of sulfite contentFood Additives aroused much public concern recently. Freeze-dried strawberries product is included in the food production licensing catalog, belongs to vegetables and dried products. <The examination specification of vegetables and dried products process permit> limits the quantity of sulfite in food products. This assignment try to find out a high-efficiency, fast and accurate detection method by the comparison of distillation method (regular method in the lab) and chromatography of ions(advanced method).