Mechanism of chilling injury amelioration in guava (Psidium guajava L.) fruit cv. Allahabad Safeda under modified atmosphere

The study was conducted to determine the critical temperature for chilling injury development in 'Allahabad Safeda' guava fruits and to elucidate the mechanism of chilling injury amelioration with low density polyethylene (LDPE) packaging and Semperfresh-coating. Chilling injury occurred in guava fruits held at 5 deg C for three weeks and then transferred to ambient condition (20 deg C). Desiccation, pitting and peel discoloration were the prominent symptoms of chilling injury which became prominent only when fruits were removed from cold storage. Keeping fruits at 8 deg C and 15 deg C did not result in chilling injury bu the fruits ripened while in storage. Modified atmosphere (MA) storage exemplified by LDPE packaging and Semperfresh-coating effectively ameliorated chilling injury in fruits stored at 5 deg C for 4 weeks. LDPE packaging and Semperfresh-coating served as physical barrier to moisture loss thus significantly reducing weight loss, desiccation and pitting. The maintenance of cell integrity and high water content in the tissues resulted in higher firmness values of MA-treated fruits as a consequence of a lower polygalacturonase activity during ambient holding (24 deg C). The high total phenolic content and low polyphenol oxidase activity of MA-treated fruits resulted in retardation of peel and pulp browning upon removal from storage and during ambient holding. Retardation of ripening due to modification of internal atmosphere was reflected in the high chlorophyll level, low carotenoid content and high firmness value of fruits from these treatments. LDPE packaged fruits were highly preferred by the panelists due to better flavor, aroma and absence of off-odor and off-flavor compared with the Semperfresh-coated and control fruits.