Influence of process variables on the drying kinetics and color properties of pear slices (Pyrus communis)

In this work, the effect of drying conditions on pear slices' physicochemical properties was determined. The factors investigated were drying temperature, air velocity, and addition of ascorbic acid. An analysis of variance indicated that the factors affected (P ≤ .05) the response variables significantly. The lowest drying time resulted at 60°C, 3 m s−1, at 0%, and 1% of ascorbic acid concentration. At these drying conditions, the final moisture content in pear samples was 0.14 g H2O g d s−1. The water activity of the pear samples was in the range from 0.27 to 0.39. A low value of 6.36 of color difference was obtained at 50°C, 1 m s−1, and 0% of ascorbic acid. During the drying process, the lightness in pear samples increases as the air velocity and the drying temperature increases. The highest hue values (from 54.66° to 63.27°) resulted in dried pear samples without ascorbic acid; therefore, the dried pear slices tended to yellowness. Chroma results ranged from 19.51 to 21.41 and from 14.96 to 19.16 in pear slices with and without ascorbic acid. Therefore, the color of the pear slices resulted in grayish‐yellow. An increment in sugar content was observed from an initial value of 18°Brix to values from 37.5 to 48.7°Brix. This behavior is because the sugar core is concentrated in large amounts during the drying process as the residual water content decreases.