Effect of pectin-based coating on the kinetics of quality change associated with stored avocados

Undesirable storage conditions lead to physical and chemical quality loss in stored avocados, which affect its consumer acceptability. Studies aimed at quantifying the extent of quality changes under different storage conditions are valuable for minimizing the deleterious effect on product quality. The objective of this study was to quantify the effect of pectin-based coating on the kinetics of quality change in stored avocados. Avocados were coated with a pre-evaluated pectin-based emulsion and stored at three temperatures (5, 10 and 20C) for various times. At selected storage times, samples were removed and evaluated for quality parameters (physical: texture and color; chemical: ascorbic acid, pH, titrable acidity and total soluble solids; and physiological: respiration rate). Results revealed that avocados became softer and darker with the passage of time, and higher temperatures resulted in more rapid changes in the different quality parameters. The rate of CO2 evolution at the climacteric peak in control samples was 287, 253 and 186 mL/(kg(.)h) at 20, 15 and 10C, respectively, reached after 6, 12 and 16 days, while in coated samples, the peak values of 232, 210 and 152 mL/(kg.h) were reached after 8, 14 and 22 days, respectively. Control fruits lost 5.2, 6.8 and 11.5% of their original weight during 7 days of storage at 10, 15 and 20C, respectively, while coated fruits lost 3.8, 4.5 and 9.1% under the same conditions. A zero-order model was used for Delta E, and a first-order model was used for L value. Coating extended the shelf life to over a month at 10C. The textural softening of avocados during storage followed a first-order kinetic model. Typical climacteric behavior was observed in stored avocados under all conditions, with the appearance of respiratory peak delayed as a result of the coating. In general, most changes were well described by some form of kinetic model. Temperature sensitivity of the rate constant was adequately described by the Arrhenius model.