Tuesday, February 11, 2014


Pasteurization is an age old process using the principle that most pathogens perish at a temperature of about 60C and fluid milk was mrketed fir decades under chilled conditions after pasteurization. Emergence of sterilization process using temperatures beyond 100C practically eclipsed the pasteurization process though for short term preservation it is still  being used. High temperature treatment of most foods does cause some damage to their characteristic texture and flavor. Of course there are many alternate options to food processing industry for safeguarding the quality of foods which include use of chemical preservatives, controlled atmosphere storage, ionizing radiation, high pressure treatment etc and depending on the type of food to be sterilized industry deploys them to get optimum results. Though microwave energy is supposed to be clean and easily controllable, most processes involving use of microwave energy tend to be batch operations affecting the their productivity very significantly and industry always looks to mega scale processes, continuous in nature, for achieving better economic results. It is in this context the recent development of a semi-continuous microwave based pasteurization process is a welcome development. Here is a take on this new development which may be some what exciting to food scientists as well as the industry.       

"According to Tang, the 915 MHz microwave-assisted pasteurization process significantly improves upon traditional thermal pasteurization, offering food producers a more efficient means of making foods safe while retaining consumer appeal. After two to four minutes of heating the product to 194 F/90 C, which is below the boiling point of water, the numbers of pathogenic bacteria can be reduced a million-fold.
"We can control foodborne pathogens and viruses and provide high-quality products," said Tang. The process also allows traditionally frozen meals to be refrigerated instead of frozen, saving retailers and consumers significant energy costs. "We had some exciting early results. The quality of microwave pasteurized foods – specifically mollusks, shrimp and tofu – is substantially better than conventionally pasteurized foods," said Barbara Rasco, professor in WSU's School of Food Science and collaborator on the project. A shelf life exceeding one month at refrigeration temperatures has been achieved for several formulated food items, including stroganoffs, curries, burritos and hors d'oeuvres. Shyam Sablani, another WSU collaborator, is leading package development. Pasteurizing chilled meals using the new method preserves product quality more than commercial canning (sterilization) processes for shelf-stable foods. Traditional canning typically operates at 249 F/120 C or higher in order to kill the dangerous pathogen Clostridium botulinum; but the temperature, pressure and length of the canning process often degrades food quality, making it less acceptable to consumers, said Tang

According to the innovators, the process is capable of raising temperatures slightly beyond pasteurization but never above 100C, the boiling point of water. Since no significant positive pressure is developed within a closed packet containing the food, there is less likely to be any damage to its integrity due to this process. There are other issues which need to be sorted out before coming out with a commercially viable technology which include the type of packaging materials compatible with microwave radiation and their cost aspects, extent of leachables getting into the food, equipment cost etc. Eventually there will be a commercial technology emerging in not too distant a future and food industry can look fore ward for such a day. 


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