MICROBIOLOGICAL QUALITY AND THE INABILITY OF PROTEOLYTIC CLOSTRIDIUM-BOTULINUM TO PRODUCE TOXIN IN FILM-PACKAGED FRESH-CUT CABBAGE AND LETTUCE

The production of toxin by a 10-strain mixture of proteolytic Clostrid ium botulinum in fresh produce packaged in polyethylene films having h igh (7,000 cc/m(2)/24 h; HOTR) and low (3,000 cc/m2/24 h; LOTR) relati ve oxygen permeability was determined. Shredded cabbage and lettuce in oculated with similar to 10(2) spores/g were placed in bags composed o f the two films (1.4 kg/bag), and the bags were then vacuum sealed. Pr oduce was stored at 4, 13, and 21 degrees C for up to 21 (cabbage) or 28 (lettuce) days and analyzed periodically. At each sampling time, th e gas composition within the bags, pH of the produce, and microbial po pulations (total aerobic and anaerobic microoganisms, lactic acid bact eria, psychrotrophic bacteria, and yeasts and molds) were determined. In addition, the presence of botulinal toxin was determined using the standard U.S. Food and Drug Administration mouse bioassay protocol. Ba gs made of HOTR film prolonged sensory quality of cabbage and lettuce, especially at 13 and 4 degrees C. Packaging material had an effect on the growth of various groups of microorganisms; however, there was no t a general trend. For example, lettuce packaged in HOTR bags had high er aerobic microbial populations than that packed in LOTR, but no sign ificant difference (P less than or equal to 0.05) was observed with ca bbage. Growth of psychrotrophic bacteria was greater in vegetables pac kaged in HOTR film while growth of yeasts and molds was not affected b y either packaging film. Most differences in microbial populations in produce packaged in LOTR and HOTR films were less than 1 log(10) CFU/g . Botulinal toxin was not detected in cabbage or lettuce packaged in e ither film or stored under any test condition.