DSC Melting Profile of Cold-Pressed Hemp Seed Oil as an Authenticity Fingerprint Influenced by Scanning Rate

Abstract

Among the variety of edible cold-pressed oils on the market, hemp seed oil is becoming increasingly popular among scientists and consumers due to its plethora of nutritional compounds. In this study, the goal was to examine the thermal characteristics of cold-pressed hemp seed oil pressed from seeds of the Henola cultivar procured by five different suppliers in two different seasons. This aim of this research was to establish how various scanning rates can affect the unique thermal profile of cold-pressed hemp seed oil in terms of an authenticity assessment. The melting transition was manifested by curves with four peaks for all hemp seed oils; however, they differed for each scanning rate in terms of the shape and peak intensity. Comparing the curves obtained at heating rates of 1 and 2 °C/min, noticeable differences were observed in the melting transition parameters between hemp seed oils, showing that small differences in fatty acid composition can cause changes in DSC profiles. In contrast, at a scanning rate 5 °C/min, the melting curves were similar for all hemp seed oils. It was also observed that for all the scanning rates, there was a strong negative correlation between the total content of polyunsaturated fatty acids (ƩPUFAs) and the peak temperature of the three peaks (Tm2, Tm3, and Tm4). The most abundant fatty acids were PUFAs, i.e., linoleic acid (C18:2), with contents ranging from 47 to 55%; and α-linolenic acid (C 18:3 n–3), with contents ranging from 17 to 25%. The application of linear discriminant analysis (LDA) enabled a discriminant model to be built based on the DSC data obtained for differentiation of oils pressed from fresh and stored seeds.

Discrimination of Selected Cold-Pressed and Refined Oils by Untargeted Profiling of Phase Transition Curves of Differential Scanning Calorimetry

“…This information can provide insight into the oil's purity and authenticity, as well as its thermal stability. Different exothermic or endothermic curves obtained by DSC technique can provide information about the energy changes that occur inside fats or oils during phase transitions, such as melting [Islam et al, 2023] or crystallization [Brożek et al, 2022]. These curves are determined by the structure and behavior of triacylglycerols (TAG), which are the major constituents of fats and oils.…”