Influence of frying parameters and cooking oil type on the physicochemical composition of used cooking oil in bitter yam chips production

Abstract

Bitter yam is an underutilized but nutrient-dense tuber, and it has the potential of being converted to value-added bitter yam chips through the deep fat frying technique. This study aimed to investigate the influence of frying temperature, frying cycle and cooking oil type on the physicochemical composition of used cooking oil in bitter yam chips production. Response surface methodology was used to interact the effect of frying temperature (170℃, 180℃, 190℃), frying cycle (1st, 2nd and 3rd cycle) and cooking oil type (soybean oil, coconut oil and peanut oils) on the viscosity, peroxide value, colour (L*, a* and b*), iodine value, free fatty acid (FFA), p-anisidine, saponification value and refractive index of the used cooking oil. The frying cycle significantly influenced the viscosity, peroxide value, iodine value, L*, b*, FFA and p-anisidine of the used cooking oil. The quadratic effect of cooking oil type affected the a* while the quadratic effect of the frying cycle influenced the refractive index of the used cooking oil. The used coconut oil had the highest viscosity (78.74), peroxide value (3.23), iodine value (80.10) and saponification value (203.21). However, the used peanut oil had the highest L* (25.39), p-anisidine (3.44), and refractive index (1.52) while soybean oil had the highest a*(4.40), b*(1.60) and FFA (62.16) at varied frying conditions. This information would be valuable to producers of bitter yam chips on cooking oil reusabilit