Cauliflower

Cauliflower is normally only stored for short periods to fill gaps in the supply chain caused by periods of hot dry weather. There also appears to be interest in storing cauliflower florets for longer periods following blanching and dehydration for subsequent use in catering packs (Kadam et al., 2005). Under optimal conditions (0°C and 95% relative humidity), cauliflower may be stored for up to 6 weeks. In practice, storage beyond 2-3 weeks is inadvisable. Cauliflower curd is very susceptible to damage during harvesting and even cryptic injuries will enlarge during storage into blemishes and discoloration associated with fungal and bacterial invasions. Spoilage can develop very quickly, leading to downgrading or outright rejection of the curds. Even during the normal time periods of distribution, curd discoloration develops and this is exacerbated where the heads are overwrapped with polyethylene film. Alternaria spp. cause leaf spots prior to harvest; these affect the wrapper leaves and can cause downgrading during cutting and grading.

Infection of the white curds is a source of much more serious wastage during storage and marketing. Small lesions (<5 mm) will spread and coalesce within 7 days of cutting, favoured by warm, moist conditions. Rapid cooling to remove field heat and cool chain marketing at 4°C are recommended to inhibit Alternaria-induced brown rotting of the curds. Since both A. brassicae and A. brassicicola are seed-borne pathogens also capable of survival on soil debris, there are several avenues by which cauliflower crops may become infected. Transfer to the developing curds leads to postharvest sporulation and spoilage during storage, distribution and marketing.

Infection of cauliflower heads by downy mildew (P. parasitica) causes pale greyish to brown discoloration on the curd surface. Inside the head, grey or black spotting and streaking extend through the bract tissues. Apparently healthy curds stored at 20°C and 70% relative humidity are rapidly spoiled by downy mildew sporulation. Storage at 4°C retards the expression of symptoms. Secondary invasion by soft rotting bacteria increases the rate of disintegration and deterioration of cauliflower heads. As with cabbage, ringspot (M. brassicicola), grey mould (B. cinereae) and in some instances sooty moulds (Cladosporium spp.) have been associated with postharvest spoilage of cauliflower.

Several Pseudomonas spp. and E. carotovora cause bacterial soft rots in cauliflower postharvest. Mechanical damage or bruising during harvesting and transit provide entry for soft rotting bacteria that may be spread between infected and healthy heads by the knives used for harvesting. Bacteria may also enter following primary infection by fungi such as Alternaria. Free water on cauliflower curds increases the rapidity of bacterial rotting, hence harvesting under wet conditions and overwrapping heads increases the likelihood of spoilage. Temperatures in excess of 10°C also encourage the rotting of cauliflower curds.

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