EFFECT OF DIFFERENT STORAGE CONDITIONS ON THE OXIDATIVE STABILITY OF AFRICAN PEAR (Dacryodes edulis) PULP OIL
ONWUZURUIKE UZOCHUKWU ANSELM *
Department of Food Science and Technology, College of Applied Food Sciences and Tourism, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.
A. C. NWACHUKWU
Department of Food Science and Technology, College of Applied Food Sciences and Tourism, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.
G. ANYANWU SADDAM
Department of Food Science and Technology, College of Applied Food Sciences and Tourism, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.
U.C. UZOCHUKWU
Department of Food Science and Technology, College of Applied Food Sciences and Tourism, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
African pear pulp oil (36.01%) was obtained through Soxhlet extraction method, divided into three (3) portions and stored under three different conditions: dark cupboard (20-25 °C, acclimatized environment), a refrigerator (4-8 °C), and at room temperature exposed to natural light (26-32 °C). The oxidative stability of the oil samples was studied for eight weeks and were assessed for their quality indices; free fatty acid, peroxide, iodine, viscosity, refractive index, tocopherol and thiobarbituric acid values. The results for dark cupboard condition at the beginning and end of storage ranged from 4.95 to 7.07% free fatty acid, 1.83 to 3.03 meq O2/kg peroxide value, 36.05 to 27.95 gI2/100g iodine value, 19.87 to 27.97 Pa.s viscosity, 1.422 to 1.463 refractive index, 225.40 to 177.42 mg/100g tocopherol, and 0.94 to 2.07 mg/g thiobarbituric acid value. Under refrigerated condition (2-8 °C), the values at the beginning and end of storage ranged from 4.95 to 5.07% free fatty acid, 1.83 to 2.11 meq O2/kg peroxide value, 36.05 to 34.05 g I2/100g iodine value, 19.87 to 23.45 Pa.s viscosity, 1.422 to 1.429 refractive index, 225.40 to 207.87 mg/100g tocopherol content and 0.94 to 1.08 mg/g thiobarbituric acid value. At room temperature (26-32 °C), the values ranged from 4.95 to 10.84% free fatty acids, 1.83 to 11.63 meq O2/kg peroxide value, 21.35 to 36.05 g I2/100g iodine value, 19.87 to 31.75 Pa.s viscosity, 1.422 to 1.493 refractive index, 225.40 to 161.56 mg/100g tocopherol, and 0.94 to 4.05 mg/g thiobarbituric acid value. African pear pulp oil samples stored under refrigerated storage condition had the best quality indices at the end of storage period (8 weeks), hence, better oxidative stability.
Keywords: African pear, oxidative stability, storage conditions, pulp oil