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

16 Chapter 2Fig. 2.1. CO 2injury on apples in the UK. (Photograph courtesy of Dr R.O. Sharples.)appear’ (Fig. 2.1). They also showed that theappearance of CO 2injury symptoms is a functionof concentration, exposure time and temperature.They describe external CO 2injurywhere ‘initially the damaged area is markedlysunken, deep green in colour and with sharplydefined edges. Later in storage the damagedtissue turns brown and finally almost black.’It may be that the injury that is referred to asspongy tissue in Alphonso mangoes and someother mango varieties may be related to CO 2injury, since they display similar morphologicalsymptoms as those described for apples.Injury caused as a result of low O 2levelsis due to fermentation, also called anaerobicrespiration, resulting in the accumulation ofthe toxic by-products alcohols and aldehydes.These can result in necrotic tissue, which tendsto begin at the centre of the fruit (Fig. 2.2).The lower O 2limit for apples was foundto be cultivar dependent, ranging from a lowof about 0.8% for Northern Spy and LawRome to a high of about 1.0% for McIntoshin cold storage. For blueberries, the lower O 2limit increased with temperature and CO 2level. Raising the temperature from 0 to 25 °Ccaused the lower O 2limit to increase fromabout 1.8% to approximately 4%. RaisingCO 2levels from 5 to 60% increased the lowerO 2limit for blueberry fruits from approximately4.5 to >16% (Beaudry and Gran,1993). Marshall McIntosh apples held at 3 °CFig. 2.2. O 2damage to apples taken from acontrolled atmosphere store. (Photograph courtesyof Dr R.O. Sharples.)in 2.5–3.0% O 2+ 11–12% CO 2developedsmall desiccated cavities in the cortex associatedwith CO 2injury (DeEll et al., 1995).Mencarelli et al. (1989) showed that high CO 2concentrations during storage (5, 8 or 12%)resulted in CO 2injury of aubergines, characterizedby external browning without tissuesoftening. Wardlaw (1938), also workingwith aubergines, showed that high CO 2can