113 Indian Journal of Agricultural Sciences 91 (3): 445–9, March 2021/Article Effect of evaporative cooling on peel browning and quality of litchi (Litchi chinensis) SHILPA 1 , B V C MAHAJAN 1 *, NAVPREM SINGH 1 , K S BHULLAR 1 and SUMANJIT KAUR 1 Punjab Agricultural University, Ludhiana 141 004, India Received: 06 October 2020; Accepted: 02 November 2020 ABSTRACT The present study was carried out during 2016–18 at Punjab Agricultural University Ludhiana to examine the effect of evaporative cooling (EC) on peel browning and postharvest quality of litchi fruit during cold storage. The litchi fruits cv. Dehradun were harvested at the physiological maturity and subjected to EC treatments for 2 h, 4 h and 6 h. The fruits without EC were kept as a control. Thereafter, fruits were packed in corrugated fberboard boxes and stored in a walk-in-cold room maintained at 2-3°C temperature and 90-95% relative humidity. The fruit samples were analyzed at weekly interval till four weeks for various physiological attributes, biochemical traits and enzymatic activities. The application of evaporative cooling for 6 h maintained lower physiological weight loss (6.38%), retained higher frmness (106.1g force),TSS (16.96°B), acidity (0.26%), anthocyanins (0.19 ∆A/g FW) and total phenols (218.43 mg/100g) during storage. The browning index of fruits was observed to be 3 (1/4-1/2 surface area brown up to 14 days of storage) with 4 and 6 h exposure to EC. The fruits subjected to EC for 6 h also maintained the lower activities of polyphenol oxidase (PPO) and peroxidase (POD) activity as compared to control. The study exhibited the expediency of EC treatment (6 h) to maintain the acceptable peel colour and prolong the storage life of fruits for 14 days as compared to 7 days in case of control. Keywords: Browning, Evaporative cooling, Polyphenol oxidase, Peroxidase activity, Quality Litchi is a prominent fruit of India, known for its pleasant favour, attractive colour and nutritious value. It occupies an area of 92 thousand ha with the production of 6 lakh MT with a productivity of 6.2 MT/ha (Anonymous 2018). It is a nutritious fruit containing vitamin C, proteins and a fair amount of calcium, phosphorus, iron and vitamin A & B. It is also a great source of dietary fbres, proanthocyanidins and polyphenolics, which boosts the immune system (Deerasamee and Chaisawadi 2014). However, peel browning normally starts within 24-48 h of harvest, is the major hurdle infuencing its visual acceptance, leading to decline in its commercial value (Xiao et al. 2019). Browning is thought to be due to breakdown in cellular compartmentation of enzymes and substrates which in turn cause oxidation of phenolics, producing brown by-products (Jiang et al. 2004). The harvesting of litchi coincides with the extreme high temperature and pre-monsoon rains leading to huge postharvest losses. Moreover, short span of harvesting period (2-4 weeks) further aggravates the problem. Pre- cooling is the most vital technique to remove the feld heat from freshly harvested produce. This process slows down the metabolism and reduces deterioration (Ferreira et al. 2006).Among various pre-cooling methods, evaporative cooling is a simple, easy-to-operate and cost-effective. It is an affordable technique and can be executed by the farmers at their farms. The objective of this study was to examine the effcacy of evaporative cooling to diminish the pericarp browning and maintain the postharvest quality of litchi fruits during storage. MATERIALS AND METHODS Fifteen uniform litchi plants of cv. Dehradun were selected at Fruit Research Station, Gangian, Punjab during 2016–18. The litchi fruits were harvested at the physiological mature stage from all the four directions of the plant. Thereafter, small bunches of half kilogram fruits were prepared and packed in plastic crates and transported in an air-conditioned van to the Punjab Horticultural Post Harvest Technology Centre P.A.U. Ludhiana. Method of evaporative cooling: Evaporative cooling works on the principle of conversion of liquid water into vapour using the thermal energy in the air, resulting in a lower air temperature. The litchi fruits packed in plastic crates were put before the dessert cooler and cool humidifed air was allowed to pass through the vents of plastic crates inside the enclosed chamber. The fruits were given EC treatments for 2, 4 and 6 h respectively. The pulp temperature of the produce was monitored regularly with the help of a Present address: 1 Punjab Agricultural University, Ludhiana. *Corresponding author email: mahajanbvc@gmail.com. https://doi.org/10.56093/ijas.v91i3.112531