213 Evaluation of Quality Attributes of Fresh-Cut Lettuce (Lactuca sativa L.) Stored in Different Controlled Atmospheres H.M. Darezzo, B.C. Benedetti R. Deliza, S. Cenci, E.B. Gonçalves Postharvest Department, Agricultural Engineering Faculty, UNICAMP EMBRAPA – Food Technology Av. das Américas, 29501, Guaratiba Caixa Postal 6011, CEP 13081-970 Campinas/SP CEP 23020-470 Rio de Janeiro/RJ Brazil Brazil Keywords: Lactuca sativa L., minimally processed, storage, gas mixture, sensory evaluation, quality. Abstract The market of fresh-cut vegetable products is increasing in Brazil. Mechanic injuries, caused by cutting, increase the respiration rate and biosynthesis of ethylene, stimulating chemical and biochemical reactions responsible by changing sensory characteristics. Therefore, the storage of fresh-cut products is critical in maintaining quality. This paper evaluated the storage of fresh-cut lettuce (Lactuca sativa L.) of cultivar Lorca, a kind of iceberg lettuce grown in Brazil, stored 15 days at 5°C in different controlled atmospheres: 5%O 2 + 10%CO 2 ; 3%O 2 + 10%CO 2 ; 3%O 2 + 12%CO 2 and atmosphere air, called control. The samples were chemically and sensory analysed. A panel consisting of eight selected and trained judges evaluated the attributes: green intensity; turgidity; midrib browning; edge browning; cooked appearance; dark spots; overall appearance impression. Midrib browning was the main problem in the storage studied. It must be considered as the principal limiting attribute to extend the shelf life of fresh-cut lettuce. The treatments 3%O 2 +10%CO 2 and 3%O 2 +12%CO 2 were found to conserve best the sensory characteristics during the used storage time due their efficiency to retain turgidity and overall appearance, and to retard midrib browning. These conditions induced only minor chemical changes in acidity and chlorophyll levels. Russet Spotting was not a limiting factor for the fresh-cut ‘Lorca’ lettuce quality. INTRODUCTION The commercialisation of fresh-cut vegetables in the Brazilian market yielded US$ 50 mil. in 1999, with the perspective of increasing to US$ 150 mil. for the next four years (Rabello, 1999). The conservation of the fresh-cut products is critical due to the physicals injuries of the vegetable tissues inflicted upon processing. These injuries accelerate the metabolism and, subsequently cause changes in nutritional and sensory properties, leading to a quick decrease of quality and shelf-life. Cutting of vegetable tissues and the cell rupture promote contact between enzymes and substrate, causing among others, an early enzymatic browning by phenylalanine ammonia lyase and polyphenol oxidase enzymes activity. The enzymatic darkening of the midrib is a major processing-induced disorder for the fresh-cut lettuce, causing a significant reduction in its commercial value (Brecht, 1995; Varoquaux & Wiley, 1996). The main techniques for fresh-cut products preservation are the utilization of the cold chain together with packaging in beneficial atmospheres (López-Gálvez et al., 1996). The packaging in modified active atmosphere has as its basic principle the reduction the O 2 level, and, consequently, a decrease of the respiration rate of the product. Also, an increase in CO 2 level is beneficial because of a reduced enzymatic browning due to the inhibitory effect on the polyphenoloxidase activity. Also minor effects on ethylene formation and activity were reported (Kader et al., 1989). Each product has its particular adequate atmosphere condition, which depends on the temperature and time of storage (Gorny, 1997). According to Cantwell (2000), the mixture of 0.5 to 3% O 2 + 10 to 15% CO 2 was beneficial for fresh-cut lettuce, contributing to a prolongation of shelf-life by maintaining Proc. 8 th Int. CA Conference Eds. J. Oosterhaven & H.W. Peppelenbos Acta Hort 600, ISHS 2003