Effect of different maturity (measured as IAD index) on storability of apples in CA-bags

At main commercial harvest four pallet sized boxes of apple (Malus ×domestica) cultivar ‘Aroma’ from one grower were assessed for maturity by using a portable spectrometer giving an IAD index (index of the absorption difference between 670 and 720 nm) indicating chlorophyll content. The apples were sorted into three groups; IAD index <0.65, 0.66 - 0.80 and >0.81. Apples of all groups were assessed for quality parameters at harvest and after storage in CA-bags at 2°C (about 100% RH) or natural atmosphere (NA) at 1°C (about 90% RH) for three months and after simulated shelf life at 20°C for 14 days. At the same times the apples were assessed for decay, both physiological disorders and fungal attacks. The CA-bags were gas-tight plastic bags for one pallet and were connected to an external gas control unit. The atmosphere inside the CA-bags consisted of 2% O2 and 2% CO2 during the cold period. At the start of the experiment apples from the different IAD index groups were not similar in subjectively judged ground colour and cover colour but similar in firmness and starch content. After three months of cold storage both apples stored at natural atmosphere and in CA-bags were still different in ground and cover colour and IAD index. In apples from CA-bags the titratable acidity content was higher in >0.81 group than on those with an IAD index <0.65. After 14 days at 20°C apples with IAD index >0.81 were different from <0.65 group in ground-colour and IAD index, but other parameters assessed were similar. After three months CA-bag stored apples had 2% visible decay but apples stored in NA had up to 27% decay. The apples with IAD index <0.65 had highest incidence of decay. After 14 days at 20°C apples with IAD index <0.65 stored in CA-bags had developed 5% decay while there was no decay in the other IAD index groups. Apples with IAD index <0.65 stored in NA had developed 45% decay after 14 days at 20°C while apples from the other groups had developed about 20% decay. Senescent decay and breakdown accounted for 90% of the physiological disorder while bitter rot was the major reason of fungal decay. CA-bags were found to be an efficient tool to prolong storage period and IAD index values might be useful in determining the potential storage life.