Microwave sterilization process
    Unlike conventional microwave sterilization heat sterilization , pasteurization rely conventional heat from the heating process, the heat transfer to the inside surface of the food , the transfer rate is dependent on the heat transfer characteristics of the food , and the desired temperature as the sterilization time is sterilized species may be. Thus , the sterilization process determines its center temperature of the food surface temperature difference , and the temperature of the inner layer lag state , faced with the same food sterilizing time difference , thus extending the overall time required to sterilize the food , the microwave sterilization time is considerably shorter than the conventional heating sterilization time , because the microwave the food uniformly heated both internally and externally , it does not need food to achieve sterilization temperature warm-up time required , not to mention microwave sterilization factors than just heat unilateral factor. Accordingly, unlike conventional heat sterilization microwave sterilization characteristics, combined microwave sterilization process may bring negative effects , use the following sterilization process .
    An intermittent microwave irradiation
    Japanese Red Star professors have used pulsed microwave irradiation of food, achieved better bactericidal effect , a short pulse is generated intermittently strong microwave electric field acts on the food, the food temperature after absorption of microwave energy , but because it is instant high-energy , food warming changes are not large , thus greatly improving the bactericidal effect , according to red Star experimental data show that the common E. coli , Bacillus subtilis and Aspergillus species such as suspension medium inoculated in the oil , the microwave frequency of 2800MHz, the pulse width 1 ms , pulse repetition frequency of 2000Hz strong microwave pulse irradiation of the sample , when the pulse power, respectively , and 400Kw 200Kw , the irradiation time was 90 seconds and 60 seconds to achieve complete sterilization , when the sample temperature up to 17 ℃ respectively , and the 22 ℃ 86 ℃ up to 92 ℃, if the traditional method of heat-sterilized to kill Bacillus subtilis , usually sterilized in hot and humid conditions, a temperature of 100 ℃, take time to 11 3 minutes.
    In addition, for sausages for intermittent microwave irradiation , conventional heating (90 - 95 ℃ hot water boiled 4.5 minutes ) sterilization sterilization compared with the control group test, the results show that , despite the low average power microwave irradiation , time is short ( 370 watts , 160 seconds ) , but its bactericidal effect is better than traditional pasteurization , compared with the control group , a significant bactericidal effect , the samples for the determination of residual bacteria routine testing . Intermittent Microwave irradiation strength lies in high electric field strength can be used within a short time to achieve sterilization , but the high electric field strength and power density will be processed microwave equipment and penetration resistance of materials , higher demands , and the need for precise controlling the irradiation time , these requirements are microwave equipment cost will increase .
    Two continuous microwave irradiation
    To compensate for intermittent microwave irradiation defects , you can use a lower field strength , an appropriate extension of the continuity of the microwave irradiation time of microwave irradiation sterilization process . Generally speaking , tunnel box type microwave equipment cabinets low power density , can be suitable for the process requirements. In the material on the temperature and the heating time ( heat-resistant ) permitting , appropriate to extend the exposure time , will help strengthen the bactericidal effect , but also make the material heated state equilibrium , so they can have enough time to make the material by means of heat conduction temperature difference between inside and outside the decrease , according to tests, the frequency , the power is continuously adjustable microwave equipment, seasoning seaweed ( plastic compound bag ) , beer , soy sauce ( both glass bottles ) for sterilization treatment , the results showed that: microwave heaters box , seasoning seaweed by microwave irradiation 40-2 seconds later, completely kill E. coli ; beer you need two minutes and 30 seconds to 3 minutes sauce you need 2 points to 2 minutes and 50 seconds , compared to conventional heat sterilization ratio, seasoned laver 2 minutes under microwave irradiation retort sterilization effect on heat-treated for 30 minutes rather , the soy sauce 2 minutes under microwave irradiation sterilization effect will be better heated for 4 minutes in a water bath effect, and by the physical and chemical indicators for the soy sauce and reducing sugars , amino acids and other components analysis, their grades have improved. Similarly, if the microwave heater is flat , right seasoning seaweed and other sterilization tests also achieve better results. It is noteworthy that the continuous microwave sterilization test samples were add any preservatives .
    Three times fast microwave irradiation and cooling
    The purpose of this sterilization process designed to quickly change the microbial ecology ambient temperature, and repeated microwave irradiation sterilization , thus avoiding long continuous manner so that the material is hot , to keep the material color, aroma , taste and nutritional components to provide favorable conditions for the process suitable for temperature-sensitive liquid sterilization, such as beverages , wine sterilization preservation. Sterilization temperature sterilization objects of different visual setting control . According to the Japanese foreign language Yokouchi patent ( 1990 ) report on the killing Lactobacillus sake of test results : If the lactic acid concentration of 102 / ml of magnitude , then by 1. 5Kw power microwave radiation , the temperature reached 63 - 65 ℃, and more heating and cooling times of microwave sterilization time of 1 second , you can kill all the concentration of lactic acid bacteria .