Freshcut Cabbage

Shredded cabbage is usually distributed in polymeric film bags. Washing in chlorinated water followed by dewatering by centrifugation are common in the industry. Citric acid-containing dips are also employed by some manufacturers, purportedly to delay both physiological disorders and microbial growth, although there is little experimental evidence that such treatments are effective. Quality defects due to the development of off-flavors, odors, and changes in color are not uncommon in distribution systems.

Whole cabbage is frequently stored for extended periods of time before processing. Temperatures are maintained near 0°C and relative humidity above 90%. Stored cabbage is at risk of spoilage by fungi and the use of fungicides (such as benomyl, thiabendazole) is practiced in some countries [9]. Microbiological examination of whole cabbage heads by King et al. [10] showed that outer leaves carry much higher microbial populations than tissues close to the core. These ranged from a density of 1.4 x 106CFU/g on the outer leaves to 3.8 x 102 CFU/g in core samples of stored cabbage sampled over a period of several months. Psychrotrophic bacteria belonging to the genera brevibacter-ium, chromobacterium, citrobacter, pseudomonas, and xanthomonas were the largest group of microorganisms present, although yeast and mold were also recovered in large numbers. Geeson [9] also found that the outer leaves of stored cabbage carry large populations of fluorescent pseudomonads, pectolytic bacteria, yeasts, and molds. In the latter study, postharvest application of benomyl and thiabendazole by drenching was correlated with higher bacterial populations in cabbage stored for a period of several months at various relative humidities.

Unfortunately, the impact of unit operations on the microbiology of shredded cabbage has not been examined in detail. However, commercial experience has shown that removal of outer leaves prior to slicing improves the microbiological stability of shredded products. Shredding likely distributes remaining contaminants throughout the product and provides extensive opportunities for growth on cut surfaces. Hao et al. [11] examined the microbiology of shredded cabbage stored in both low- and high-oxygen transmission films at 4, 13, and 21°C. Carbon dioxide levels rose and oxygen levels declined faster in the headspace above product packaged in less permeable films. Surprisingly, the observed spoilage patterns were consistent for all treatments, and populations of aerobic bacteria tended to dominate the spoilage association. However, lactic acid bacteria populations increased to high densities regardless of packaging treatment or storage temperature. The development of sourness and blowing of packages can occur in these products and has been associated with extensive growth of these bacteria. Growth of this relatively minor component of the raw cabbage microflora can be stimulated by the addition of salt for the manufacture of fermented products. Reasons for their rapid growth in shredded cabbage despite the presence of active, large populations of Gramnegative, psychrotrophic bacteria remain unclear.

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