PerspectivesAre you interested in submitting a Perspective Article? Be sure to read The Science Advisory Board's Editorial Guides for Perspective Articles. Click here. Microbial Contamination: The Importance of Microbiological Testing to Prevent Its Spread From the Field to the Consumer by M.V. Rao, Ph.D. Microbial contamination of foods is a growing issue of concern for the producer, processor, trade and consumer. Food microbiology is a vast subject and this article is based on my personal experiences at the field level and with the industry, trade and laboratory. These are some of the observations in the course of my work for the past 12 years on the following products: Karaya Gum, Cochlospermum Gum, Indian gooseberries, tamarind, and other spices like chilies and turmeric. Field Level: The post harvest operations begin at the field level with the picking of spices from the plant and separating them from the other plant parts. The source of microbial contamination can be air, water, soil or the human touch with bare hands. Then comes the process of drying. Drying of the spice to an acceptable level involves sun drying or drying in the shade -- both of which are out in the open. Usually because the produce is voluminous, it is spread on the floor and shuffled often. This typically is a time consuming process involving as many as three weeks or more and is the phase of maximal microbial growth and contamination. The next stage is sorting of the infested pieces and manual grading. The final stage is packing at the field level where some partially wet material may be packed, which sometimes leads to a strong infestation. Science and scientists should come into the picture at all stages of these field operations. The producer (farmer) and his workmen should be made aware of the invisible microbes and the toxins. The farmer needs to be educated on the hygienic practices of picking, drying, packing and storage. The dangerous effects of pathogens and disease outbreaks should be made explicit to them. A microbe analysis profile of their own produce should be explained, and visual presentations of prevention techniques should be made. Storage: Some commodities are stored in cold storage for preserving their properties. Here, it is essential to understand the proper temperatures that are most suitable for the individual spices. It should also be borne in mind that once the produce is spoiled at the field level, it cannot be rectified by mere cold storage. Work needs to be done on the types of bacterial contamination in each spice and their survival and growth rates at various temperatures. The scientist needs to explain these aspects to the producer and the cold storage operators. Processor level: Let us take a look at a very minimal level of processing -- like sorting of the whole spices and grinding. Contamination in a process house can be from the floor area, air, water or humans who handle the produce. Very often we encounter pathogenic contamination due to unhygienic practices at the process house. The workmen should be constantly trained about the dangers of E. coli, Salmonella, Shigella, Staphylococcus and given measures to avoid their contamination. For every step in processing, proper safety precautions must first be instituted in the plant. Personal hygiene and hygiene-equipment make a very big impact in the processing. Some terminal heat treatments are advised for some spices, which should not however spoil their organoleptic properties. Testing: (The crucial part) Testing for microbes is laborious and tedious, and it involves specialized skills. The type of methodology employed greatly influences the results obtained from various laboratories. For example, in a simple total plate count there will be significant differences when one uses nutrient agar versus standard plate count agar. Thus, a test for Salmonella, which takes more than 120 hours of time, may show false positives due to overlapping strains like Proteus. Furthermore, the non-uniformity of the contaminants can pose an enormous problem. The microbiologist should be an open-minded scientist who is cognizant of the possibility of false positives. The microbes are so deceptive that they show an identical pattern of results until the confirmatory stage. The microbial scientist is the real link between the producer, processor and the consumer and has a great responsibility. There needs to be a free and constant exchange of information between laboratories, scientists and equipment manufacturers. It is the use of the most validated techniques that is important rather than the use of the latest technique, which is not adequately validated. We sometimes may find, therefore, that a Thin Layer Chromatographic picture and reaction on a plate is more valid for some forms of identification than HPLC. Cutting-edge techniques should be well validated against standard procedures before they are recommended for general use. Test kits: Test kits play a very vital role in all stages of production, processing and trade of spices. There is an urgent need for developing rapid test kits for instantaneous estimation at the field level (e.g., aflatoxin identifications). There is also a need for proper test kits for analytical work in the laboratories in order to produce faster results. However, test kits should be thoroughly studied before using them as replacements for conventional testing methods. Information should be obtained to ensure that test kits yield similar results to conventional methods and can also rule out false positives. We find that many laboratories use the rapid test kits without first evaluating their effectiveness. The test kits should be validated in food laboratories for food analysis. Mere extension of validation from clinical laboratory data is not adequate since contaminants and false positives may vary from food to human sputum, blood or urine. Unfortunately, with the ease-of-use of these fast test kits, analysts may tend to refuse the traditional test because they believe it to be "out-dated". Some rapid test kit manufacturers may also release the product without substantial testing in the field -- usually the only testing data available is from their own R&D. In addition, the test kits or procedures often must be product specific. Thus, it is probably inappropriate to recommend that the same columns and conditions for HPLC aflatoxin analysis in peanuts also be used on red chilies. The cleanup cannot be as perfect in red chilies as in peanuts in view of various other fluorescent contaminants. Microbiological science should reach the field and farmer and should not be confined solely to the laboratories. It should reach the trade and help in instituting practical, feasible and stringent specifications. There should be a constant exchange of thought between microbiologists at the universities/research institutes, private researchers/analysts, rapid test kit makers and equipment manufacturers. Finally, importance should be given to unpublished observations since it is not always possible to transform every small (but vital) observation into a formal publication or document. ### Dr. M.V.Rao, Ph.D. Dr. Rao's Laboratories India The author is a private researcher and analyst working on spices and other natural products. A Science Advisory Board member since April 2002 ### << Previous Next >> [ View All Perspectives ] |
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