Effect of Pretreatments on the Drying Characteristics and Quality of African Star Apple (Chrysophyllum albidum)

Fruits, due to high moisture content, deteriorate quickly when not adequately preserved. Drying, a common preservation method, will affect quality of final product if not properly controlled. Pretreatments prior to drying have been established as a way of retaining product qualities. This study investigated the effect of pretreatments on the qualities of dried African star apple flesh. African star apple fleshes were sliced (2, 4, 6 and 8 mm) and subjected to pretreatments [blanching (80 ºC for 3 min), lime juice (100%), ascorbic acid and salt solution (1:25 w/v)]. Untreated samples served as control. Samples were dried in cabinet dryer (50, 55 and 60 ºC) at 2 m/s constant air flow-rate, monitored at intervals, until constant weight was obtained. Ascorbic acid and colour measurement of the fresh and dried sample were determined using standard method. The moisture contents of the African star apple flesh were observed to reduce from a mean value of 70.44%, 71.55% and 73.24% to 2.38%, 1.91% and 3.23% at temperatures of 50, 55 and 60 °C, respectively. The total drying time ranged between 7 to 8 h. Colour of the dried African star apple was significantly preserved by the pretreatments used, and low overall color change (ΔE) was obtained at the lowest drying temperature (50oC). The ascorbic acid and lime pretreatments however had better colour overall. Lime pretreatment for 2 mm thick at 50ºC gave the best result in terms of ascorbic acid retention. Hence, lime juice pre-treatment has potentials of retaining quality of dried fruits.