Effects of heat treatment on postharvest quality of peaches Tao Zhou a , Shiying Xu a , Da-Wen Sun b, * , Zhang Wang a a Department of Food Science and Engineering, Wuxi University of Light Industry, Wuxi, Jiangsu 214036, China b FRCFT Group, Department of Agricultural and Food Engineering, University College Dublin, National University of Ireland, Earlsfort Terrace, Dublin 2, Ireland Received 3 June 2001; accepted 19 September 2001 Abstract ‘‘Hujin’’and‘‘Baihua’’peaches(Prunus persica (L.)Batsch.)weretreatedattemperaturesrangingfrom37to43 °Cfor1–3hwith hot water and for 3–48 h with hot moist air, respectively. Heat treatment with hot water caused heat injury to Hujin peach, and therefore is not suitable for Hujin peach. Hujin peaches were heated by moist air at 37 °C for 3–48 h. Heating of Hujin peach at 37 °C for 12 h was most effective in maintaining hardness and reducing mass loss, while for Baihua peach, the most effective treatment was heating at 37 °C for 16 h. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Peach; Heat treatment; Firmness; Mass loss; Postharvest; Fruit; Hot water; Hot moist air 1. Introduction Peach is a popular fruit in China. Wuxi (Jiangsu, China) is one of the most famous growing areas for peaches.NativepeachesfromWuxiarefamousfortheir richnutritionandsuitableratioofsugartoacidaswellas theirstrongflavour.However,theyareeasilydamagedin transportationandhaveaveryshortshelflifeoflessthan 7 days at ambient temperature. Chemical treatments have been used to prevent insect attack and prolong postharvestshelflife.However,theuseofchemicalshas been minimised for food safety and environmental rea- sons. Therefore, many physical methods are being ex- tensively studied as substitutes for the current chemical methods in commercial applications (Klein & Lurie, 1990; Paull, 1990). An example of a physical method is high-temperature treatment, which can control pests, preventpathogeninfection,increaseresistancetochilling injury, delay fruit ripening and extend postharvest shelf life (Civello, Martinez, Chaves, & A~ no n, 1997; Ketsa, Chidtragool, Klein, & Lurie, 1998; Wang, 1998). In recent years, heat treatments have been used ef- fectively to extend the shelf life of fruits. Research in- dicates that prestorage heat treatment at 38 °C for 4 days could maintain apple firmness, colour, soluble solids and organic acids while promoting resistance to physiologicaldisorderssuchasscaldandfungaldiseases during storage (Conway, Sams, Wang, & Abbott, 1994; Klein & Lurie, 1991). Furthermore, thermal stress af- fects the capacity of biological systems to synthesise proteins, resulting in greater or lesser synthesis of the proteins present and the synthesis of a new set of spe- cialproteinstermed‘‘heatshockprotein’’(HSP)(Brodl, 1989). The precise function of HSP is not yet totally explained, but at least in yeasts, there is increasing evi- dence that a 70 kDa HSP can be a cytoplasmic factor involved in the translocation of proteins cross mem- branes (Brodl, 1989). Unfortunately, such research is not yet available for peaches. The purpose of the present work was to study the effectofhigh-temperaturetreatmentsonqualityandrip- ening parameters of peaches. To this end, peaches were treated with hot moist air and hot water under different time–temperature combinations to evaluate the effec- tivenessofthetreatmentstomaintainthepeachquality. 2. Materials and methods 2.1. Sample preparation Two varieties of peaches (variety: Hujin and Baihua) were obtained from a local orchard in Yangshan of Journal of Food Engineering 54 (2002) 17–22 www.elsevier.com/locate/jfoodeng * Corresponding author. Tel.: +353-1-716-5528; fax: +353-1-475- 2119. E-mail address: dawen.sun@ucd.ie (D.-W. Sun). URL: www.ucd.ie/refrig 0260-8774/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0260-8774(01)00179-0