FEATURE ARTICLE
Safer Salads
Contaminated fruits and vegetables are more common than ever. Why? And what can consumers do to protect themselves?
Jorge M. Fonseca, Sadhana Ravishankar
Putting Safety in Place
Not all sanitizing treatments that succeed in the laboratory will work in a commercial setting. For conventional washing systems, it's not unusual for a disinfectant to be 100 times less effective at reducing microbial contamination in the field than it was in the laboratory. This failure is often linked to poorly designed equipment that doesn't do a good enough job of applying the sanitizer to the product.
Indeed, sprays and baths, the most common application methods, are inadequate for some kinds of produce. Better alternatives include vapor-phase treatment and vacuum infiltration, both of which penetrate hard-to-access sites and maximize contact with microorganisms. Some fruits and vegetables can also be surface-pasteurized with steam, hot water or superheated air. Because different strategies target different pathogens, growers in the future may use combinations of disinfectants, such as organic acids with other chemicals, or UV light with a spraying sanitizer.
In the more distant future, pathogens might be controlled by antimicrobial substances produced by other plants or by selected microorganisms. For example, raw carrots and freeze-dried spinach powder both inhibit the growth of Listeria monocytogenes, and some indigenous bacteria can outcompete pathogenic bacteria to prevent its growth. Such "natural" agents may be the next big thing in microbicides and preservatives, although the mechanisms of many of these natural compounds are unclear and require considerable research.
From an industry standpoint, it's important to emphasize that none of the sanitizing treatments listed above represents a "silver bullet" for ensuring the microbiological safety of fresh produce. Indeed, the best way to get rid of pathogens in produce is to prevent their introduction in the first place. Regardless of the potency of their sanitizing agents, operations that handle fresh produce gently (and hence provide no avenue for pathogen entry) will probably yield safer fruits and vegetables than operations in which nicks and bruises are common.
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