Factors affecting the postharvest quality of MA packaged broccoli

Packaging with suitably gas permeable plastic bags (low-density polyethylene film or polybutadiene film) kept the, freshness and content of chemical components of broccoli (Brassica oleracea L., Italica group), but packaging with thicker film and subsequent storage at higher temperature made the gas concentrations inside the bags low in O-2 and high in CO2. These conditions further induced the production of acetaldehyde, ethyl alcohol, and acetic acid, and more from stem tissues than from florets. High CO2 appeared to enhance the alcohol fermentation of broccoli at 2% O-2 tested. Under anaerobic conditions, alcohol dehydrogenase and pyruvate decarboxylase activity were very low and the aldehyde dehydrogenase concerned with acetic acid formation was not detected in broccoli. Acetic acid was produced in broccoli under lower O-2 and was higher in flower buds than in stem tissues, but both materials tested separately produced very low levels of acetic acid. Cleaning broccoli with available chlorine at 1000 ppm reduced acetic acid formation under anaerobic conditions. Acetobacter in Bower buds tested was observed microscopically. From these results the off-flavor formation associated with anaerobiosis of broccoli may be largely affected by the production of acetaldehyde, ethyl alcohol and acetic acid in flower buds and stem tissues.