Biochemical and Microbial Changes during the Storage of Minimally Processed Cantaloupe

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Abstract
The effect of storage time on pH, titratable acidity, °Brix, organic acids, sugars, amino acids, and color of minimally processed cantaloupe melon (Cucumis melo L. var. reticulatus Naud. cv. Mission) was determined at 4 °C and 20 °C. Changes in most of the biochemical parameters with storage time were relatively slow at the lower temperature. At 20 °C, a 17% loss in soluble solids and a 2-fold increase in acidity occurred after 2 days. Organic acid content also increased considerably with time at this temperature as a result of the production of lactic acid. Oxalic, citric, malic, and succinic acids were the organic acids, and glucose, fructose, and sucrose were the sugars present in the freshly cut cantaloupe. Malic acid concentration decreased concurrently with lactic acid production indicating the possible involvement of anaerobic malo-lactic fermentation along with sugar utilization by lactic acid bacteria. The effect of storage on microbial growth was determined at 4, 10, and 20 °C. Gram-negative stained rods grew at a slower rate at 4 °C and 10 °C than the Gram-positive mesophilic bacteria that dominated microorganism growth at 20 °C. Eighteen amino acids were identified in fresh cantaloupe: aspartic acid, glutamic acid, asparagine, serine, glutamine, glycine, histidine, arginine, threonine, alanine, proline, tyrosine, valine, methionine, isoleucine, leucine, phenyl alanine, and lysine. The dominant amino acids were aspartic acid, glutamic acid, arginine, and alanine. Total amino acid content decreased rapidly at 20 °C, but only a slight decrease occurred at 4 °C after prolonged storage. Changes in lightness (L*), chroma, and hue at both temperatures indicate the absence of browning reactions. The results indicate the potential use of lactic acid and lactic acid bacteria as quality control markers in minimally processed fruits. Keywords: Melons; fresh-cut; fruits; Cucumis melo L.; carbohydrates; sugars; organic acids; amino acids; microorganisms; lactic acid bacteria; shelf life; quality