New method could end lettuce contamination, say researchers
The Institute of Food Research, based in Norwich, said that it is currently at the patent application filing stage in regard to an agent it has devised to inhibit bacteria such as E-coli and Salmonella attaching to spinach and lettuce. A world first, according to the researchers, the bacterial inhibitor is likely to be of interest to fresh produce growers, processors and retailers, as an outbreak of a foodborne disease can be extremely costly, as well as potentially fatal for the consumer. Microbiological safety is a key issue for entire fruits and vegetables and for ready-to-eat prepared vegetable tissues, because all are intended for consumption raw, without further preparation or cooking. Confidential component The project's lead researcher, Tim Brocklehurst, told FoodProductionDaily.com that the next stage of the process is to make a compound with a higher co-efficiency than the microbes so that it attaches to the tissues of the fruit and vegetables and thus inhibits bacterial contact. The Norwich team's patent application was announced at the Food Factory conference 'Hygienic Processing' in Laval, France last week. However, Professor Brocklehurst would not be drawn on the inhibitor's components, claiming confidentiality reasons. No indication was given as to when the inhibitor would be commerically available. Washing ineffective Bacteria can contaminate crop plants in situ during the growth of the plant or during harvesting, handling, processing, distribution or preparation. "Our experiments have shown that conventional commercial washing and sanitizing methods to remove microbial contaminants from produce surfaces are only marginally effective," said Brocklehurst "The method we have developed can prevent the attachment of bacteria to leaf tissues at the harvesting stage or the processing stage, thus increasing food safety at critical points in the supply chain," added Brocklehurst. Bacterial study The Institute's research team investigated the kinetics and mechanisms of attachment of bacteria to growing plant crops of industrial importance. The researchers found that bacteria prefer to grow on the cut surfaces of fruit and vegetables and that they multiply throughout storage to form an extensive layer, often many cells thick. The team also looked at the speed and the persistence of attachment in different environments and found that salmonella, in particular, attaches in minutes and that this attachment is often difficult to reverse. Safety concerns Foodborne illnesses are an important area of food safety. An estimated 76 million cases occur each year in the US alone, causing about 325,000 hospitalizations and 5,000 deaths, according to the Center for Disease Control and Prevention (CDC). In the past week, 145 people in the US, including 23 who required hospital treatment, were infected by the contamination of certain types of raw red tomatoes by Salmonella. The bacteria causing the illnesses are Salmonella serotype Saintpaul, an uncommon type of Salmonella. An outbreak of E. coli in September 2006 was traced back to packaged cut spinach originating from California. The outbreak killed three people and sickened more than 200 people across the US.