ABSTRACT
M in i m a l processing is defined as the handling, preparation, packaging, and distribution of agricultural commodities in a fresh-like state (Shew felt, 1987). Problems such as enzymatic browing and microbial growth are a concern when using this process, especially for apples. Enzymatic browning in apples is caused by the enzyme polyphenoloxidase (PPO), also called ortho diphenol oxidase or catecholase (Nicolas et al., 1994). Polyphenoloxidase is one of the most important color deteriorative enzymes in fruits and vegetables (Uhlemann, 1993). In apples, PPO catalyzes the oxidation of phenolic com pounds containing two o-dihydroxy groups to the corresponding o-quinone (Nicolas et al., 1994). Condensation of the 0-quinones results in the formation of dark brown polymers called melanin. To inactivate PPO, refrigeration alone is insufficient. Although refrigeration temperatures slow enzymatic browning, they do not stop it from occurring. One promising way to inhibit PPO is the application of edible polysaccharide films because they are effective gas barriers and have little impact on the fresh taste of apple slices (Guilbert, 1986). Application of an edible film formulated with FDA-approved ingredients with desirable physical, sensory, and microbial properties to minimally processed apples could reduce the development of enzymatic browning. Among the possible approved ingredients, ascorbic acid proves to be a good reducing agent for oxidized polyphenolic substrates because it prevents polymerization, which causes the discoloration (Uhlemann, 1993). Potassium sorbate functions as an antimicrobial preservative to retard the growth of yeasts, molds, and bacteria. To maintain or improve the texture of apple slices, calcium chloride
can be incorporated into the film. The ideal edible film should create a barrier that can retard the loss of desirable flavor volatiles and moisture while re stricting the exchange of oxygen and carbon dioxide. Respiration and ethylene production should also be inhibited. The film should not create an anaerobic environment, as this would lead to anaerobic respiration, growth of anaerobic microbes, and an undesirable product. Research has shown that edible films protect apple pieces from moisture loss and oxidative browning for up to three days (Baldwin et al., 1995). The specific objectives of this research were to evaluate color changes in apple slices coated with a polysaccharide edible film by identifying instrumental measurements and sensory evaluation correla tions on apple slices’ color changes.
