EFFECT OF GRADUAL COOLING STORAGE ON CHILLING INJURY AND PHENYLALANINE AMMONIA-LYASE ACTIVITY IN TOMATO FRUIT AURELIO BOJÓRQUEZ GÁLVEZ, MISAEL VEGA GARCÍA 1 , JOSÉ CARO CORRALES, ARMANDO CARRILLO LÓPEZ and JOSÉ ANGEL LÓPEZ VALENZUELA Maestría en Ciencia y Tecnología de Alimentos Facultad de Ciencias Químico Biológicas Universidad Autónoma de Sinaloa 80000, Culiacán Sinaloa, México Accepted for Publication May 21, 2008 ABSTRACT Changes in phenylalanine ammonia-lyase (PAL) activity and chilling injury (CI) index were evaluated in tomato (Lycopersicon esculentum M.) during storage and ripening. Fruits were stored at 12C, 4C and from 12 to 4C (gradual cooling, decreasing 2C from 12 to 8C at 3 days intervals and then at 4C) and 85–90% relative humidity for up to 21 days followed by a ripening period of 8 days at 21C. PAL activity showed an increase during the storage period, showing a maximum value after 21 days of storage at 12–4C and 4C. Development of CI symptoms was coincident, and closely correlated with the increase in PAL activity. Gradual cooling reduced 1.5-fold the CI symp- toms. It appears that low temperatures induced the tomato fruit defense response, as suggested by the behavior of PAL activity, and gradual cooling increased chilling tolerance. PRACTICAL APPLICATIONS The storage of tomatoes at temperatures below 12C could lead to chilling injury, a physiological disorder that affects the quality of tropical and sub- tropical fruits resulting in commercial losses or reduced consumer acceptabil- ity. In this study, a gradual cooling storage treatment was used to induce tolerance of tomato against this disorder. The results of this research showed that gradual cooling could be an alternative for using temperatures below 12C 1 Corresponding author. TEL: +52-667-7136615; FAX: +52-667-7136615; EMAIL: mvega@ uas.uasnet.mx DOI: 10.1111/j.1745-4514.2009.00279.x Journal of Food Biochemistry 34 (2010) 295–307. © 2010, Wiley Periodicals, Inc. 295