Saturday, March 28, 2009


Cold sterilization and pasteurization processes are generally based on gamma radiation or X-Ray exposure at ambient temperature without recourse to heating. They have the unique advantage of not affecting the organoleptic quality or the nutrient content of the foods processed. How ever both these technologies are viewed with suspicion by the consumers because of the use of radiation energy which is mistakenly being associated with the lethal Hiroshima Atom Bomb responsible for the death and miseries of thousands of people during World War II. Tons of scientific data have been generated to prove the absence of live radiation in the products treated and more than 40 countries have cleared the use of gamma radiation in selected foods for both indigenous consumption as well as for exports. As for X-Ray treatment, it is a young technology, yet to take off, with lot of promises.

Food contamination with pathogens like E.coli, Salmonella, Listeria, etc is assuming alarming proportion in some of the developed countries in the American and European continents in spite of strict vigilance and the much acclaimed monitoring systems in place. Yet these countries could not prevent the outbreak of E.coli infection in spinach in 2006 in USA killing 3 people and sickening another 200. In USA alone 40000 cases of Salmonellosis per year are being reported killing at least 400 people and 70000 cases of E.coli infection resulting in dozen fatalities. The recent Salmonella contamination reported in Peanut products made in USA, requiring calling back of millions of dollars worth of products containing peanut paste or butter as an ingredient, is still fresh in our memory, hitting hard the credibility of their safety monitoring machinery.

Most difficult materials to be decontaminated are fresh farm produce as they suffer significant quality damage if standard thermal treatment regime is adopted. Though Salmonella is associated more with fish and meat products, their presence in fresh produce is suspected to be due to careless farm practices and indifferent handling in the packing sheds. Treatment with chlorine does help to some extent but this is not a fool proof practice and post-treatment cross infection can still take place with potential hazard to the consumer. Food chain accountability being lax in many countries, it is becoming increasingly difficult to trace the source of infection.

The prayer by the industry for a low cost technology for decontamination of thermally sensitive foods seems to have been answered by the development of a technique using low wattage electricity in the US. Though it may take some time before commercial equipment become available for decontamination of foods, the promise it holds for the future of food industry may be exciting. Excellent results have been reported with tomatoes which after packing in sealed plastic bags were exposed to a plasma field created by two high voltage, low wattage electric coils on either side. Generation of Ozone from the oxygen present with in the bag kills the pathogens within a matter of few seconds. After the treatment ozone does not stay to cause any oxidative damage to the contents and decomposes to the original atomic oxygen. Besides tomatoes, this treatment was found to be effective for spinach also and may work for any food material. The low electricity consumption of 30-40 watts, practically no rise in temperature in side the bag, no electrode intrusion into the container and suitability of both flexible and rigid plastic containers, make this technique attractive to processors as well as the consumers.

Before this technique is adopted some questions regarding use of ozone in food system need to be addressed. Generally ozone is considered a pollutant when it is present at the ground level and it is known to cause head aches, burning eyes and irritation in the respiratory passage at levels as low as 100 ppb. How much residue will remain in the treated produce must be assessed after processing. A concentration of 300 ppb is necessary to get a 99.99% kill of food borne pathogens. Also of importance is the susceptibility of the packaging material to ozone action and possibility of chemicals and artifacts generated that can contaminate the contents during processing. A claim that ozone can decontaminate fruits ad vegetables with respect to pesticide residues also calls for further study. Optimum time of processing for total kill, influence of moisture in the product on the efficacy of the process, effect of varying sizes and shapes of the materials to be treated on the product quality, etc will have to be worked out for different products.

It is likely that the above process, if technically found feasible, will be eventually patented and cost of acquiring it may be exorbitant. In the mean time why not Indian food scientists work on this principle and come out with a successful low cost gadget that will benefit thousands of small scale processors in extending the shelf life of many fresh as well as processed products in the country. Such innovations only can drive Indian food industry up the growth chart on a sustained basis.


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