Development of dried water chestnuts product

Abstract

The development of dried water chestnuts is aimed to study the appropriate concentration of calcium chloride for preparation of water chestnuts before drying process; a proper duration for drying process by using hot air oven; the comparison of drying processes between solar dried-oven and hot air oven; and the use of dried water chestnuts for Thai dessert products. The research result can be summarized that the concentration of calcium chloride solution is 0.25% that yield the best quality for water chestnuts which had 0.63 water activity (aw); 3.47 moisture content, color value of (L*) 62.38, (a*) 4.82, (b*) 35.66; and 0.79 specific density. It also yields the best quality to rehydrate water chestnuts comparing to their previous condition. A proper drying duration of water chestnuts, soaking in 0.25% calcium chloride by using solar dried-oven at different duration of drying. Dried water chestnuts dried at 9 hours and average dehydration temperature 50-55 Celsius had 0.31 water activity (aw); and color value of dried water chestnuts is of bright red with (L*) 80.14. Also, the brightness of rehydrated water chestnuts decreased to (L*) 58.30 and firmness (Newton) to 68.70. By using hot air oven, the study of a proper duration of soaking water chestnuts, in 0.25% calcium chloride indicated that drying for 3.5 hours of drying time, water chestnuts had highest moisture content, while drying for 4.5 hours had the least moisture content. Therefore, decreasing of moisture content depends on the drying duration with different methods. The study also found that dried water chestnuts using solar dried-oven had less water activity (aw) and moisture content than those using hot air oven. Moreover, dried water chestnuts from solar dried-oven had brightness value (L*) less than those from hot air oven; but dried water chestnuts from solar dried-oven had more reddish yellow than those from hot air oven. Also, there is similarity of specific density of water chestnuts from both drying methods. For rehydration of water chestnuts, color values of these 2 methods are similar. However, color, which is similar to fresh water chestnuts, is resulted by drying water chestnuts with hot air oven; and the brightness (L*) of water chestnuts texture increases. Also, value of (a*) and (b*) of water chestnuts from hot air oven are more reddish yellow. Meanwhile, firmness (Newton) from drying with hot air oven is able to maintain strength or firmness of water chestnuts. Percentages of water chestnuts absorption are similar between two drying methods. The sensory test of Thai pudding using dried water chestnuts indicated that there is no statistically significant at 95% level of average scores in the terms of color, smell, taste, dried texture and overall acceptance. The result of microbial analysis from dried water chestnuts found that there is no microorganism. In addition, the result of raw material cost calculation showed that drying 1 kilogram of fresh water chestnuts yielded 108 grams of dried water chestnuts. The total cost of production is 48.43 Baht per kilogram.