Controlled Atmosphere Storage of Fruits and Vegetables, Second ...

12 Chapter 2●●●formation of undesirable flavour andodoursaltered texturedevelopment of physiological disorders.Thompson (2003) also reviewed some of theeffects of increased CO 2levels on stored fruitsand vegetables as follows:●●●●●●●●●●●●●●●●decreased synthetic reactions in climactericfruitdelaying the initiation of ripeninginhibition of some enzymatic reactionsdecreased production of some organicvolatilesmodified metabolism of some organicacidsreduction in the rate of breakdown ofpectic substancesinhibition of chlorophyll breakdownproduction of off-flavourinduction of physiological disordersretarded fungal growth on the cropinhibition of the effect of ethylenechanges in sugar content (potatoes)effects on sprouting (potatoes)inhibition of postharvest developmentretention of tendernessdecreased discoloration levels.The recommendations for the optimum storageconditions have varied over time duemainly to improvements in the control technologyover the levels of gases within the stores.Bishop (1994) showed the evolution of storagerecommendations by illustration of the recommendationsfor the storage of the apple cultivarCox’s Orange Pippin since 1920 (Table 2.1).CA storage is still mainly applied toapples, but studies of other fruits andvegetables have shown it has wide application,and an increasing number of crops arebeing stored and transported under CAconditions. The technical benefits of CAstorage have been amply demonstrated fora wide range of flowers, fruits and vegetables,but the economic implications of usingthis comparatively expensive technologyhave often limited its commercial application.However, with technological developments,more precise control equipmentand the reducing cost, CA storage is beingused commercially for an increasing rangeof crops.The question of changes in quality offruit after long-term storage is important.Johnson (1994a) found that the storage practicesthat retard senescence changes in applesgenerally reduced the production of volatilearoma compounds. Reduced turnover of celllipids under CA conditions is thought toresult in lack of precursors (long-chain fattyacids) for ester synthesis. The lower O 2levelsrequired to increase storage duration and tomaximize retention of the desired texturalcharacteristics can further reduce aromadevelopment. Using hydrated lime or activatedcarbon to reduce the level of CO 2didnot affect aromatic flavour development,although there may be concern over continuousflushing of N 2/air mixtures. The prospectof improving flavour in CA-stored apples byraising O 2levels prior to the opening of thestore is limited by the need to retain texturalquality.Table 2.1. Recommended storage conditions for Cox’s Orange Pippinapples, all at 3.5 °C (Bishop, 1994).O 2(%) CO 2(%) Storage time (in weeks)Approximate date ofimplementation21 0 13 –16 5 16 19203 5 21 19352