Irradiation makes food ‘Salmonella’-free

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Written by Lyn Resurreccion / Science Editor   

Sunday, 12 April 2009 18:37

Salmonella contamination has been in the news lately in some peanut-butter and pistachio brands.  First, peanut-butter brands from the US were reported contaminated. Later on, samples from two local brands were reported tainted. Now it’s pistachio nuts mainly from the US that are affected, although most of the brands were voluntarily recalled just as a precaution.

Salmonella bacteria are the most frequently reported cause of food-borne illness, the US Department of Agriculture (USDA) web-site fact sheet said. To reduce salmonellosis or Salmonella infection, it said, a comprehensive farm-to-table approach to food safety is necessary. Farmers, industry, food inspectors, retailers, food-service workers and consumers are each critical links in the food-safety chain.

The Salmonella family includes more than 2,300 serotypes of bacteria which are one-celled organisms too small to be seen without a microscope. Two types, Salmonella Enteritidis and Salmonella Typhimurium, are the most common in the United States and account for half of all human infections.

Salmonella lives in the intestinal tract of humans and other animals, including birds. It is usually transmitted to humans by eating food contaminated with animal feces.

Being heat-sensitive, Salmonella present in raw meat and poultry could survive if the product is not cooked to a safe minimum internal temperature, the USDA said.

Salmonella can also cause salmonellosis through cross-contamination, wherein juices from raw meat or poultry come in contact with ready-to-eat foods, such as salads.

The bacteria have been known to cause illness for over 100 years. They were discovered by American scientist Dr. Daniel E. Salmon.

To prevent food from Salmonella contamination, the Philippine Nuclear Research Institute (PNRI) said the use of irradiation may be among interventions that may be used.

Zenaida de Guzman, head of PNRI’s biomedical research section and project leader of food-irradiation research and development project, said that in tandem with Good Manufacturing Practices and Hazard Analysis and Critical Control Points the use of irradiation in food may eliminate pathogenic microbes.

“We want the public to know that we use this technology [irradiation] to eliminate microbes, such as Salmonella, E. coli and Listeria in food,” de Guzman told the BusinessMirror in an interview.

De Guzman, however, was quick to say that the peanut butter and pistachio which were recently found or still suspected to be contaminated with Salmonella could no longer be irradiated by the PNRI.

She explained that only raw agricultural materials are irradiated, like the peanut in the peanut butter, or the raw pistachio, because the finished products have already passed a long process—from planting to harvesting, drying, processing, up to transporting, which might have caused the contamination, or that toxins might have already developed.

“Agricultural raw materials have many sources of microbial contamination, including water,” she noted.

Besides, she said, food irradiation observes certain protocols, wherein the raw food materials are irradiated immediately after they are dried after harvest to prevent the development of more microbes. She said if there is a big amount of microbes present, it might require a higher dose of irradiation that may affect the quality, taste or color of the produce.

However, she said Filipino food manufacturers should consider irradiation to make their products free from disease-causing bacteria.

Irradiation uses high-energy ionizing radiation, a PNRI flyer said, to reduce postharvest losses, disinfest fresh fruits and other agricultural products, extend shelf life of food and agricultural commodities, such as fruits, vegetables, meat, poultry, fish and seafood, reduce microbes that cause spoilage and eliminate pathogenic microbes.

De Guzman explained that irradiation—which uses 300 Gray (Gy) to 1,000 Gy dose, depending on the product that will be irradiated—is safe for human and animal consumption because there is no radioactive residue left on the product.

“It is like putting the product under x-ray,” she noted.

The PNRI’s irradiation facility was set up as pilot-scale in 1984 and was upgraded to semicommercial scale in 2008. It could handle 2 tons of products per load.

It irradiates spices and dehydrated vegetables, such as ground black and white peppers, powders like cayenne, turmeric, onion, garlic, ginger, tamarind, chives and other condiments.

De Guzman added that there is a growing volume of herbal products, like ampalaya and malunggay powder, that are irradiated at the PNRI. The same with frozen fruits for export that are used in the production of ice cream.

Fresh onions and garlic also undergo irradiation in the PNRI facility to inhibit sprouts. It, likewise, irradiates medical products for sterilization purposes, such as syringes, cotton, orthopedic implants, gauze, tubings, catheters.

She said that in foreign countries 80 percent use irradiation for sterilization. In the US even pet foods are irradiated.

Patties for hamburgers, hot dogs or frozen chicken may also be irradiated.

De Guzman announced that the Philippines may soon export mango to the US after the three-year study affirmed the absence of seed weevil in the whole country. Luzon and Visayas were already found to be seed weevil- free. The results of the same study in the Mindanao situation are being awaited this year.

The mangoes for export to the US will still be irradiated against fruit flies.

In another export prospect, de Guzman said China is making inquiries on its possible importation of irradiated mangoes from the Philippines.


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