Physical and chemical properties of nabak (Zizyphus spina-christi) seed kernel and sweet pepper (Capsicum annuum L.) seed oils.

Abstract

Nabak seed kernels and sweet pepper seeds, which are separated from the fruits and discarded as waste after processing or consumption, contain high levels of oils (30.19% and 19.57%, respectively). The chemical and thermal characteristics of nabak seed kernel oil (NSO) and sweet pepper seed oil (PSO) were investigated in this study. The NSO and PSO contained high levels of unsaturated fatty acids (84.1% and 86.5%, respectively), and the major fatty acid was oleic acid (57.3%) in NSO, but it was linoleic acid (69.4%) in PSO. The triacylglycerol (TAG) profiles show that NSO contained ten TAG species, three of which represented 87.1%, namely C54:3, C52:2 and C54:4, and triolein was the dominant (OOO, 47.0%). Pepper seed oil contained nine TAG molecular species, four of which represented 93.6%, namely C54:6, C52:4, C54:4 and C52:5, and trilinolein was dominant (LLL, 44.0%). The differential scanning calorimetry (DSC) analysis of NSO revealed that three exothermal peaks were detected during cooling, two endothermal peaks were detected during melting, and the major peak occurred at a low temperature. For PSO, three exothermal peaks were detected during cooling, three peaks were detected (one of them was exothermal) during melting, and the major peaks were observed at low temperatures. Fourier transform infrared (FTIR) spectra indicated that NSO and PSO did not contain peroxides or trans fatty acids, but they did contain low concentrations of free fatty acids. This study offers a scientific basis for the use of NSO and PSO as new sources of edible oils for food applications. © 2021 Society of Chemical Industry.