Effect of Alginate Edible Coatings Formulated with Linoleic Acid on the Aroma and Quality of Fresh-cut Golden Delicious Apple Wedges

Edible coatings (EC) preserve the quality of fresh-cut apple by creating semipermeable barriers to gases, avoiding quality loss. EC also serve as carriers of active ingredients. In this study alginate coatings were used as carriers of linoleic acid, for fresh-cut apple. The aim of this study was to evaluate the ability of Golden Delicious fresh-cut apple to metabolize linoleic acid to enhance the biosynthesis of volatile aroma compounds (VACs). Fresh-cut apple wedges were immersed in a CaCl2 solution followed by a coating of alginate (ALG), or alginate containing linoleic acid (ALG-FA) and stored at 4 °C and 85 % RH. VACs were analyzed by two means: a) in apple macerated tissue, periodically during 12 days; b) in the headspace of apple wedges kept in 0.5 L sealed containers, periodically during 7 days. In both experiments VACs content was determined by HS-SPME and GC-MS. Browning and tissue softening was delayed and texture was improved significantly by both ALG and ALG-FA coatings, when compared to uncoated wedges (CTRL). ALG-FA treatment significantly reduced weight loss in fresh-cut apples. The presence of linoleic acid caused an increase in the concentration of butyl acetate on apple tissue, been 4, 6, and 12 fold higher when compared to control apples at days 3, 6 and 9 of storage, respectively. Butyl acetate is one of the main VACs in apples, which is derived from linoleic acid metabolism trough β-oxidation pathway. No effect of linoleic acid was observed in apple tissue on VOCs derived from linoleic acid trough the lipoxygenase pathway such as hexyl acetate, hexanol and hexanal. Furthermore, higher concentration of hexanal (as well as 3-hexenal) was observed in control wedges. The concentration of aldehydes and alcohols was greater in apple tissue than in the headspace of apple wedges; while, esters showed a higher concentration in the headspace. 2-methylbutyl acetate and butyl 2-methylbutanoate content in the tissue was higher for the coated treatments, while content of hexyl butanoate and hexyl hexanoate was higher in CTRL wedges. ALG-FA coatings preserved the quality, induced the biosynthesis of butyl acetate. ALG coatings offered improved barrier properties to VACs in fresh-cut ‘Golden Delicious’ apple wedges. However, further studies are necessary to better understand the alginate EC properties as substrates carriers for the biosynthesis of VACs, and the activation of enzymes related to apple metabolism.