Table 101

Potential Sources of Melon Contamination

Preharvest

Direct fecal contamination — human, birds, reptiles, insects, other wildlife Indirect fecal contamination — irrigation water, dust from animal production During harvest

Poor worker hygiene Packing plant

Contaminated process water Poor plant sanitation Ineffective washing Cross contamination during washing Poor worker hygiene locations are highly sporadic and localized, e.g., to individual melons with adhering avian feces or insect damage, a melon defect observed by one of the authors in a California packing shed. Duffy et al. [32] reported that salmonella isolates obtained from washed cantaloupes in Texas were most closely related to isolates obtained from equipment and irrigation water, but DNA fingerprinting did not conclusively establish relationships between contamination sources. Contamination of melons could occur during harvest if worker hygiene was deficient [10].

Research is needed to identify specific sources of preharvest contamination of melons and to develop guidelines and good agricultural practices (GAPs) that reduce the risk of contamination. Appropriate training of farm workers in personal hygiene and avoidance of behaviors that result in melon contamination is essential.

10.3.2 Postharvest Conditions

Gagliardi et al. [33] reported in most cases little change or an increase of indicator microorganisms (total and fecal coliforms and enterococci) on melons during washing in samples obtained at packing facilities in the Rio Grande River Valley of Texas. They attributed contamination to the management of primary wash tanks or hydrocoolers, e.g., use of contaminated river water, buildup of soil in tanks, and depletion of chlorine. The contamination of cantaloupes in Mexico may have been due to cooling and washing with contaminated water [10]. The potential for such contamination also exists in the U.S. One of the authors has observed melon processing operations in which cantaloupes were tightly packed in tanks containing chlorinated water, with minimal opportunities for agitation of the melons or mixing of the water, prior to fresh-cut processing. Under such conditions, rapid depletion of chlorine at the melon surface and survival of attached bacteria on contaminated melons might be expected with the possibility of cross contamination of other melons in the tank.

Other potential sources of postharvest sources of contamination include poor personal hygiene or work practices by workers (one of the authors observed the failure of packinghouse employees to wear gloves or hairnets while handling melons; another worker used his foot to move cantaloupes down a ramp from a receiving platform to a conveyor) and inadequate plant sanitation. Accumulation of debris from incoming melons was visible on the aforementioned ramp and conveyors. Conveyors and processing equipment must be cleaned and sanitized on a regular schedule with sufficient frequency so as not to allow debris to accumulate and microbial populations to build up on food contact surfaces.

Such deficiencies can be addressed by development and implementation of a hazard analysis critical control point (HACCP) plan and an effective cleaning and sanitation program, and adherence to good manufacturing practices (GMPs). Of equal importance is employee training in food safety. Such training should be appropriate to the employee's job and in the employee's native language.

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