Method for improving fruit and vegetable powder microwave sterilizing effect using steam pre-treatment

Abstract

The steam pre-treatment method for raising the microwave sterilizing effect of fruit and vegetable belongs to the field of dewatered fruit and vegetable sterilizing technology. The technological process includes the first steam heating on fruit and vegetable powder with water content of 2-7 wt% for 5-15 min to raise water content to 13-22 wt% and the subsequent microwave drying and sterilizing for 90-150 s. The fruit and vegetable powder through the said sterilizing process has ultimate water content of 2-7 wt%, 3-4 log order lowered bacteria amount and high sanitary quality. The steam pre-treatment can raise the dielectric constant of the fruit and vegetable powder so as to raise the microwave sterilizing effect greatly while providing certain sterilizing effect.

Description

technical field [0001] The invention discloses a method for improving the microwave sterilization effect of fruit and vegetable powder by steam pretreatment, and the invention belongs to the technical field of sterilization of dehydrated fruits and vegetables. Background technique [0002] Fruit and vegetable powder is an extended product of dehydrated fruits and vegetables. Dehydrated fruits and vegetables are convenience foods that are processed by drying and dehydrating fresh fruits and vegetables. Poor storage of finished products, pollution in the production process, etc.), it is easy to cause microorganisms to exceed the standard, and thus cause huge losses. Due to the particularity of dehydrated fruit and vegetable food itself, general heating or chemical sterilization methods are not applicable. In order to achieve hygienic indicators, gamma ray irradiation sterilization technology is currently the most widely used sterilization treatment for dehydrated fruit and ve...

AI Technical Summary

Problems solved by technology

Irradiation can effectively control the microbial content and improve the hygienic quality of fruit and vegetable powder to a certain extent, but it has the following disadvantages: limited by the location of the radiation source, the odor of radiation or the residue of radiation will be generated, and the unique aroma of food will be lost. Some products The color changes greatly after irradiation treatment

The steam sterilization method usually uses water vapor at about 100°C or high-pressure superheated steam above 100°C for sterilization. Generally, heating with steam for 30-60 minutes can achieve the desired sterilization effect. This method has no radiation residue, but the heating time is too long. If the temperature is too high, the nutrition, color and flavor of the fruit and vegetable powder will be lost more, and the product moisture will increase after steam treatment, which requires secondary drying

In terms of microwave sterilization, Zhang Hongfa et al. (1999, Meat Industry) studied the comparison of microwave sterilization effects of different food media and found that the higher the moisture content in the food, the better the microwave sterilization effect, and concluded that the presence of water can significantly enhance the microwave sterilization effect. Conclusion: Zhu Jinguo et al. (2005, Chinese Journal of Food Hygiene) studied the sterilizing effect of mold in tea with microwaves, and found that the moisture content of tea has a significant impact on the efficiency of microwave sterilization. The content should be greater than 5%. If the moisture content is too low, the microwave action time needs to be increased, which will cause the tea to produce a burnt smell; but they have not pointed out how to take measures to improve the microwave sterilization effect and prevent scorching of low-moisture materials. , to ensure food quality

Zhou Yongsheng (2004, Chinese seasoning) used microwaves to sterilize seasoning powders such as chili powder, pepper powder, turmeric powder, licorice powder, tangerine peel powder, and cumin, and found that microwaves are feasible for most seasoning powders. Most of the seasoning powder can be heated at 100°C for 6 minutes at a microwave frequency of 2450MHz to reach its hygienic index. However, the microwave treatment time is relatively long, and the total number of bacteria is reduced by about 1 to 2 logarithmic levels. Powder) The reason for the poor bactericidal effect

Liang Jin etc. (1999, food industry science and technology) in the sterilizing test of chili powder, directly add 30ml aseptic distilled water in 100g chili powder and then microwave sterilize for 20min, the sterilization rate reaches 99.9%, has proved that increasing water content can Improve the sterilization effect, but the method of directly adding sterile distilled water is not suitable for all fruit and vegetable powders, it is easy to cause agglomeration, uneven water distribution, and uneven sterilization, and he uses microwave sterilization for up to 20 minutes

Generally speaking, most of the current microwave sterilization of food is to increase the microwave power and prolong the sterilization time to improve the sterilization effect. For dry products such as fruit and vegetable powder, the sterilization effect is often not much improved, and the product quality is greatly reduced.

[0004] As a new method of dehydrating fruits and vegetables, microwave drying and sterilization can greatly shorten the drying time, and the product is safe and hygienic, but it cannot solve the problem of excessive microorganisms in fruit and vegetable powder produced by other drying methods; Therefore, in the later stage of other drying methods, microwave drying and sterilization are often carried out when the moisture content drops to about 20% to improve drying efficiency and exert the bactericidal effect of microwaves. However, the production process is limited, and other dried products such as freeze-dried fruit and vegetable powder are obviously not so sterilizing

The microwave sterilization effect of low water content fruit and vegetable powder is poor and the problem of instability still cannot be solved