The effects of hot water dip treatments and modified atmosphere packaging on antioxidant compounds and storage quality of pomegranates having different acidity levels

In this research, the effects of hot water dip treatments and modified atmosphere packaging (MAP) on antioxidant compounds and storage quality of Hicaznar cultivar which is widely grown in our country and Beynar cultivar which is commonly grown in Antalya region were investigated. Studies were carried out for two years between the years of 2007 and 2009.In the first part of the research, hot water treatment was applied to Hicaznar fruits at the temperature of 45 ? C for 4 min and at the temperature of 55 ? C for 2 min. After hot water dip treatments pomegranates were packed in modified atmosphere bags (Xtend). Then all fruit samples including control pomegranates were stored at 2 and 6 ? C temperature with 90-92% relative humidity for 210 days.In the second part of the research, MAP was applied after harvest to Hicaznar and Beynar pomegranates. For this purpose, the first group of fruit was stored in Xtend modified atmosphere bags (MAP 1), the second group of fruit was stored in Zoe Pac modified atmosphere bags (MAP 2), and the third group of fruit was considered as control group. After packaging, all fruit samples were stored at 6 ? C temperatures with 90-92%. In the experiment, Hicaznar and Beynar fruit were stored for 210 and 140 days, respectively.During the storage period various physical and chemical analysis were performed on the fruit samples taken from the cold storage rooms at 30 and 20 days intervals for Hicaznar and Beynar pomegranates cultivars.According to the experiment results, in the first part of the research, an increase in weight loss of pomegranates was observed during the entire storage duration in both experimental years. The weight loss of the pomegranates was relatively lower in the fruit stored at 2 and 6 ? C temperatures and dipped in hot water at 45 ? C than other treatments. In the study, some decreases occurred in the amount of titratable acidity, soluble solids content, and vitamin C of pomegranates during the entire storage. Hot water dip treatment at 45 ? C was found very effective in terms of reducing of decomposition of the amount of titratable acidity and soluble solids content. During the storage, some increases were observed in the overall amount of total anthocyanin and phenolic compounds of pomegranate fruits. The amount of vitamin C, total anthocyanin and phenolic compounds was higher in control fruits then other treatments in both experiment years. C* and h ? angle values of the pomegranates dipped in hot water were found to be higher than the control group. Storage of pomegranates at 2 ? C resulted chilling injury in the fruit. Chilling injury symptoms especially become more visible after transfering the fruit to 20 ? C for 3 days, these symptoms included brown discoloration of the skin, pale colour of the arils and brown discoloration of the white segments separating the arils. The severity of chilling injury was especially higher in control fruits then other treatments in both experiment years. There were no chilling injury symptoms on the fruit stored at 6 oC. Hot water dip treatment at 45 ? C for 4 min reduced the severity of chilling injury in both temperatures and experimental years. In terms of visual quality and decays hot water dip treatments were more effective than other treatments and the pomegranates could be stored at 6 ? C temperatures for 210 days with minimal quality losses after application of this treatment.According to the results obtained from the second part of the research, it has been determined that the longer storage period resulted with higher weight losses. While there were increases in the loss of weight of Hicaznar and Beynar cultivars stored at two different MAP, there were a decrease in the amount of titratable acidity, soluble solids content and vitamin C during entire storage. At the of storage period, soluble solids, vitamin C, total anthocyanin and phenolic compounds of the pomegranates stored at MAP 1 and MAP 2 were found to be lower than the control fruits. Storing of pomegranates in both MAP created a favorable environment around the fruits and the amount of decay fruits and weight losses was lower at these treatments. Besides weight losses and decay fruits both MAP treatments were very effective in maintaining the amount of titratable acidity and skin color of the pomegranates. As a result of the experiment, the best storage temperature was 6 ? C for both cultivars and storage of pomegranates in MAP created favorable effects in terms of above indicated features. Under these conditions, Hicaznar pomegranates could be stored up to 210 days, and Beynar pomegranates for 140 days with minimal quality losses.KEY WORDS: Pomegranate, storage, antioxidant compounds, atmosphere packaging, hot water treatment