Postharvest Quality and Safety in Fresh-Cut Vegetables and Fruits

NON-TECHNICAL SUMMARY: The incidence of foodborne illness is rising as more fresh and fresh-cut produce is consumed. The absence of a definitive kill step in the preparation of fresh-cut and fresh produce has allowed human pathogen presence and survivability in these products. New, more virulent pathogen species that are acid-tolerant are evolving. The stability and antimicrobial action of ozone and electrolyzed oxidizing (EO) water in the decontamination of fresh produce is examined. Surfactants of low HLB may disrupt the hydrophobic interactions between E. coli O157:H7 and cut lettuce leaves.
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APPROACH: An overview of UGA departmental research involving evaluating novel approaches for assuring the safety of fresh and fresh-cut produce (Objective 2) was presented at the 2003 meeting in Tampa, Florida. Fundamental studies were conducted on the use of ozone, ozonated water under pressure and ozonated water plus heat treatment for inactivation of E. coli O157:H7 on inoculated alfalfa sprouts. The efficacy of using electrolyzed oxidizing (EO) water for the inactivation of E. coli O157:H7 on strawberries and broccoli was also addressed. The influence of using hydrophobic surfactants for the detachment of E. coli O157:H7 from cut lettuce surfaces was evaluated.
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PROGRESS: 1999/10 TO 2004/09<BR>
A cooperative CREES project has developed a biosecurity audit system to survey measures being taken by fresh produce and fresh-cut operations in the Southeast. Most fresh-cut operations have a written security plan, conduct security training for employees and have restricted access to their facilities. (Obj. 2 - Hurst) Effectiveness of chlorine, ClO2 and commercial raw fruit and vegetable sanitizer on spores of B. cereus and B. thurgingiensis is being tested to develop treatments to counteract B. anthracis (anthrax) contamination. (Obj. 2 - Beuchat) Biofilms formed by E. coli O157:H7 under EPS may protect the organism against sanitizers used to decontaminate lettuce and other produce. (Obj. 2 - Beuchat) Cantaloupe has been linked to several outbreaks of salmonellosis over the past few years. Ten yeasts were tested for potential antagonistic activity against S. Poona populations on cantaloupe rind and in cantaloupe juice as a natural biological process. Some molds known to cause decay of cantaloupes can allow pathogens to migrate from the rind into the edible tissue. Thus it is recommended that consumers do not eat cantaloupe from which diseased tissue has been removed, since enteric pathogens may still be present. (Obj. 2 - Beuchat) Methods of handling cantaloupe during harvesting were also studied, comparing the amount of aerobic bacteria on surfaces after transport from the field, washing and packing. Cantaloupe were washed with chlorinated water, water heated to 41-50 deg. C, or a combination of heat and chlorinated water in processing. Aerobic populations after packing were approximately the same as on pre-washed cantaloupes! Thus washing, chlorination and hot water treatments applied under actual field packing conditions do not significantly affect the total aerobic population on cantaloupes. (Obj. 3 - Harrison) Manure compost is known to attract nematodes that feed on bacteria. Within one to seven days, S. Newport was found on the surfaces of lettuce, strawberry and carrot samples placed on nematode-infested, S. Newport inoculated soil. No transfer occurred on samples placed on pathogen-inoculated soil with no nematodes. Thus nematode activity can disperse foodborne pathogens such as E. coli O157:H7, S. Poona, and Listeria monocytogenes in manure-amended soil, increasing the risk of contamination on produce. (Obj. 3 - Beuchat) Lethality of ClO2 to Salmonella enterica, yeasts and molds on blueberries, strawberries and raspberries was higher when treated at 75-90% relative humidity than at lower RH. Treatment with 4.1 mg/L ClO2 did not markedly affect the sensory quality of fruit stored for up to 10 days at 8 deg. C. (Obj. 3 - Beuchat) The use of electrostatic sprays combined with sanitizing chemicals on fresh produce and produce processing surfaces is being tested to determine whether electrostatic spray can provide uniform and effective coverage with minimal chemical use. (Obj. 2-3 - Hung) Use of citrus PME with CaCl2 increased firmness of eggplant and strawberry halves over time in storage at 4 deg. C. (Obj. 3-Wicker)
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IMPACT: 1999/10 TO 2004/09<BR>
Cost-effective recommendations for improving security for fresh produce growers and processors are being developed. Locks on chemical storage areas and cooling rooms, fencing and employee training can be implemented fairly easily. Food safety plans should include methods of monitoring and documenting security measures implemented. Control of nematodes in manure and compost amended fields can help to minimize transfer of soil-borne pathogens to fresh produce prior to harvest, thus reducing risk of contamination during fresh-cut processing. Vacuum infusion of enzymes and CaCl2 to increase cell wall strength of cut fruits and vegetables will increase the marketability of fresh-cut produce. Determining which sanitizing agent is most effective against spores of Bacillus cereus and B. thurgingiensis, which act as surrogates for B. anthracis, will shed light on how one might detoxify anthrax, should B. anthracis ever be used in a terrorist incident. The possibility of using yeasts as a natural competitive inhibitor against Salmonella Poona population growth on cantaloupe tissue may reduce the incidence of salmonellosis outbreaks associated with cantaloupe. The risk of contamination spreading during processing to edible fruit from damaged, bruised or moldy cantaloupe as it is removed must be considered carefully.