Food Chemistry 110 (2008) 428–435 www.elsevier.com/locate/foodchem
Eﬀect of chitosan coating combined with postharvest calcium treatment on strawberry (Fragaria Â ananassa) quality during refrigerated storage
´ Pilar Hernandez-Munoz a,*, Eva Almenar b, Valeria Del Valle a,1, Dinoraz Velez a, ˜ Rafael Gavara a
Institute of Agrochemistry andFood Technology, CSIC, Apdo. Correos 73, 46100 Burjassot, Valencia, Spain b School of Packaging, Michigan State University, East Lansing, MI 48824-122, United States Received 25 October 2007; accepted 11 February 2008
Abstract Strawberries (Fragaria Â ananassa Duch.) were coated with either 1% or 1.5% chitosan (CS) or chitosan combined with calcium gluconate (CaGlu). Following treatment,strawberries were stored at 10 °C and 70 ± 5% RH for one week. The eﬀectiveness of the treatments in extending fruit shelf-life was evaluated by determining fungal decay, respiration rate, quality attributes and overall visual appearance. No sign of fungal decay was observed during the storage period for fruit coated with 1.5% CS (with or without the addition of CaGlu) or 1% CS + 0.5% CaGlu. By contrast,12.5% of the strawberries coated with 1% CS lacking calcium salt were infected after ﬁve days of storage. The chitosan coating reduced respiration activity, thus delaying ripening and the progress of fruit decay due to senescence. Chitosan coatings delayed changes in weight loss, ﬁrmness and external colour compared to untreated samples. Strawberries coated with 1.5% chitosan exhibited less weightloss and reduced darkening than did those treated with 1% chitosan, independently of the presence or absence of CaGlu. However, addition of calcium to the 1% chitosan solution increased the ﬁrmness of the fruit. Coated samples had greater visual acceptability than had untreated fruits. The addition of calcium gluconate to the chitosan coating formulation increased the nutritional value byincrementing the calcium content of the fruit. Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Strawberry; Chitosan concentration; Calcium gluconate; Shelf-life; Refrigerated storage
1. Introduction Strawberry (Fragaria Â ananassa) is a highly perishable non-climacteric fruit. It must be harvested at full maturity to achieve maximum quality in terms of visual appearance (freshness, colour andabsence of decay or physiological disorders), texture (ﬁrmness, juiciness and crispness), ﬂavour and nutritional value (vitamins, minerals, dietary ﬁbre and phytonutrients). Grey mold, caused by Botrytis cinerea Pers. Fr., is the most economically signiﬁcant postharvest pathogen of strawberry fruits. Strawberry spoilage after
Corresponding author. Tel.: +34 963900022; fax: +34 963616101. ´ E-mailaddress: firstname.lastname@example.org (P. Hernandez-Munoz). ˜ 1 Present address: Sigdopack S.A, Guacolda 2151, casilla 4, Quilicura, Santiago, Chile. 0308-8146/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2008.02.020
harvest, can also occur by mechanical injury and desiccation. Low storage temperatures and modiﬁed atmospheres with elevated CO2 levels are commontools for avoiding, at least partially, mold growth and senescence, and extending fruit shelf-life (Manning, 1996). However, prolonged exposure of berries to high CO2 concentrations can cause oﬀ-ﬂavour development (Ke, Zhou, & Kader, 1994). The use of synthetic chemical fungicides has been the main method for reducing postharvest disease. However, consumer concern over pesticide residues onfoods, along with pathogen resistance to many currently used pesticides, has increased the need to ﬁnd alternative methods for decay control. Recently, biologically active natural products have started to become an eﬀective alternative to synthetic fungicides (Tripathi & Dubey, 2004).
´ P. Hernandez-Munoz et al. / Food Chemistry 110 (2008) 428–435 ˜
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