Comprehensive Thermal Characteristics of Different Cultivars of Flaxseed Oil (Linum usittatissimum L.).

Jolanta Tomaszewska-Gras,Mahbuba Islam,Emilia Fornal,Liliana Grzeca,Anna Kaczmarek

doi:10.3390/molecules26071958

Abstract

The aim of this study was to describe the thermal properties of selected cultivars of flaxseed oil by the use of the differential scanning calorimetry (DSC) technique. The crystallization and melting profiles were analyzed depending on different scanning rates (1, 2, 5 °C/min) as well as oxidative induction time (OIT) isothermally at 120 °C and 140 °C, and oxidation onset temperatures (Ton) at 2 and 5 °C/min were measured. The crystallization was manifested as a single peak, differing for a cooling rate of 1 and 2 °C/min. The melting curves were more complex with differences among the cultivars for a heating rate of 1 and 2 °C/min, while for 5 °C/min, the profiles did not differ, which could be utilized in analytics for profiling in order to assess the authenticity of the flaxseed oil. Moreover, it was observed that flaxseed oil was highly susceptible to thermal oxidation, and its stability decreased with increasing temperature and decreasing heating rate. Significant negative linear correlations were found between unsaturated fatty acid content (C18:2, C18:3 n-3) and DSC parameters (OIT, Ton). Principal component analysis (PCA) also established a strong correlation between total oxidation value (TOTOX), peroxide value (PV) and all DSC parameters of thermo-oxidative stability.

Highlights

The differential scanning calorimetry (DSC) technique allowed differences in the shape of crystallization and melting profiles obtained by different scanning rates to be identified, and the oxidative stability of five different flaxseed oil cultivars at various thermal conditions to be measured
The crystallization process measured using the DSC technique was manifested as a single peak, which among the cultivars ranged between −55.35 and −54.59 ◦ C for a cooling rate of 1 ◦ C/min, while for the scanning rate of 2 ◦ C/min, the temperature ranged from
Analysis of the melting process at different scanning rates revealed that melting curves were more complex, and in the case of rates 1 and 2 ◦ C/min, the cultivars differed in curve shape, while the profiles did not differ for a scanning rate of 5 ◦ C/min

Summary

Introduction

Flax (Linum usitatissimum L.) is an important plant known and cultivated all over the world mainly for oil and fiber. Originating from West Asia and the Mediterranean region, flaxseed (Linum usitatissimum, Latin; meaning “very useful”) has long been cultivated as one of the oldest multi-purpose crops in history [1]. The use of flaxseed for human consumption dates back to ancient times, the revelation of the flax genome sequence in 2012 has added a new value and attention to the study [3]. The potential nutritional benefits of flaxseed oil are associated with its active biological compounds. Flaxseed oil comprises outstanding quantities of polyunsaturated fatty acids (PUFA), phytoestrogenic lignans (secoisolariciresinol diglucoside, SDG) [8], and an array of antioxidants such as phenolic acids and flavonoids. ALA in flaxseed can be metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) [9]

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