Physicochemical and thermal characteristics of Australian chia seed oil
Graphical abstract
Introduction
Plant oils have become increasingly popular in recent years due to their high proportion of healthy polyunsaturated fatty acids (PUFAs). The composition of oils, especially the fatty acid profile, is vitally important from human nutrition and public health points of view because lipid profile of an individual is effectively governed by the type and the quantity of fats and oils in their foods (Cunnane et al., 1993). Epidemiological and scientific findings have shown a strong relationship between the type and amount of fat intake and the occurrence of certain diseases, including coronary heart disease (CHD), cancer, diabetes, and depression (Cunnane et al., 1993, Simopoulos, 2002). In this respect, replacement of saturated and trans-fats with healthier unsaturated fats in human dietary intake has become one of the focus of food and nutrition research (Ayerza, 2010). Unsaturated fatty acids perform various vital functions in biological membranes and are considered as precursors of diverse lipid regulators of the cellular metabolism (Guillén & Ruiz, 2004). Although PUFAs are scientifically proven to be healthy fatty acids, human body is often unable to efficiently synthesize them de novo to a sufficient level. Therefore, they must be supplied through diet or dietary supplements. Although fish oils are currently the main industrial sources of PUFAs, they are neither suitable for vegetarian and vegan consumers nor can meet the increasing global demand of omega-3 PUFA from natural fish sources. Besides, there is an increasing concern of presence of mercury and organic pollutants such as polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and dioxin-like polychlorinated biphenyls (DL-PCB) in ocean fish (Smutna, Kruzikova, Marsalek, Kopriva, & Svobodova, 2008). Accordingly, many food manufacturers and research organizations are interested in alternative plant-based PUFA resources to meet the increased consumer demand of PUFA rich oils.
Chia plant (Salvia hispanica L.) belongs to mint family (Lamiaceae). Chia plant produces tiny seeds (∼1 mm in diameter), which are oval in shape and come in white, gray or black color (Ixtaina et al., 2011). Chia seeds are increasingly being recognized for their nutritional benefits and are included in products such as yoghurts, pasta, breads, hamburgers and sports nutrition (Franklin & Hongu, 2016). As a consequence, industrial production of chia seeds and food products containing chia seeds has been rapidly growing in many parts around the world including Mexico, Argentina, Australia, Bolivia, Colombia, Ecuador, Nicaragua and Paraguay (Crawford, Deards, Moir, & Thompson, 2012). Nevertheless, Australia has recently become one of the largest global producers of chia seeds (Crawford et al., 2012).
In general, the major constituents in chia seeds include 25–40% oil (Ixtaina et al., 2011, Timilsena et al., 2016a, Timilsena et al., 2016b), 17–24% protein (Timilsena, Adhikari, Barrow, & Adhikari, 2016c) and 18–30% dietary fibres (Timilsena et al., 2016a). Chia seed oil (CSO) is rich in α-linolenic acid (ALA) and linoleic acid (LA) which are essential fatty acids (EFAs). These two EFAs constitute more than 80% of fatty acid composition, making CSO as one of the healthiest oils (Segura-Campos, Ciau-Solís, Rosado-Rubio, Chel-Guerrero, & Betancur-Ancona, 2014). Intake of chia seeds has been reported to substantially reduce serum triglycerides (TG) and low-density lipoprotein (LDL), and increase high-density lipoprotein (HDL) (Fernandez, Vidueiros, Ayerza, Coates, & Pallaro, 2008). These proven health benefits make CSO a highly sought staple oil for a healthy diet.
ALA and LA contents in chia seed oils produced in the United Sates, Argentina, Chile, Mexico and Italy were reported to vary from 6.3% to 69.0% and 15.3% to 46.3%, respectively (Segura-Campos et al., 2014). Likewise, the composition of monounsaturated fatty acid (MUFA) such as oleic acid (OA) and saturated fatty acid (SFA) such as palmitic acid (PA), and stearic acid (SA) in chia seeds were also reported to vary in the ranges of 2.9%-16.2%, 6.5%-7.5% and 0.3–3.0%, respectively (Segura-Campos et al., 2014). The observed differences in fatty acid composition suggest strong influence of geographical location, climatic condition, growing practice and variety of plant on the fatty acid profile of CSO (Ayerza, 2009). Aforementioned studies only reported the physical properties and chemical composition of CSO that was extracted from seeds grown outside of Australia. To the best of our knowledge, there is no documented literature so far on the physicochemical aspects of Australian CSO. Besides, the thermal characteristics of oils such as melting and crystallization are important parameters for their processing and utilization. These characteristics of CSO are not yet reported in any literature. The aim of this study was to investigate physicochemical characteristics, fatty acid profile and triacylglycerol composition, as well as thermal characteristics (i.e. crystallization and melting profiles) of CSO extracted from Australian-grown chia seeds. This study also aimed to determine the oxidative stability of CSO and correlate it with its structure and composition.
Section snippets
Materials and methods
Chia seeds (S. hispanica L.) (Lot No. 15180) were obtained from The Chia Company (Melbourne, Australia). These samples were stored at ambient condition in air tight plastic containers until used. These seeds were sieved using 60 mesh sieves (250 mm) and any foreign materials such as stone, dirt, and immature seeds were separated manually by visual observation. The seeds free of foreign matter were then used directly for oil extraction after grinding into fine powder. All chemicals used in this
Yield and physicochemical characteristics
The yield of CSO extracted in this study was found to be 26.6%, which is in the same range as those reported for Mexican, Guatemalan, Colombian and Bolivian chia seeds (Segura-Campos et al., 2014). This yield was, however, substantially lower than that of Argentinian chia seeds (35.6–38.6%). The yield of oil from chia seeds is slightly lower than that from ground nuts (37.8%) (Nkafamiya, Maina, Osemeahon, & Modibbo, 2010), sunflower seed (∼48.0%) (Flagella, et al., 2002) and rapeseeds (∼36.0%)
Conclusions
The CSO extracted from Australian grown chia seeds, was a yellowish liquid at ambient temperature, and contained more than 80% PUFAs as evidenced by the results from GC–MS, FTIR and NMR analysis. The predominant fatty acids were found to be (ω-3) α-linolenic followed by (ω-6) linoleic acid at ω-3 to ω-6 ratio of 3:1, which is ideally beneficial for maintaining good health. Owing to a high polyunsaturated fatty acid content, CSO gets oxidized rapidly (OSI = 2.4 h) requiring a suitable method for
Conflict of interest
There is no conflict of interest recorded for this work.
Acknowledgements
The first author acknowledges the PhD scholarship supported by RMIT University and CSIRO (Australia). The authors wish to thank The Chia Company (Melbourne, Australia) for providing chia seed samples used in this study.
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2023, Food BioscienceCitation Excerpt :The curves of PSOs extracted by different solvents were almost indistinguishable, and consistent with that by hot pressing. Generally, the melting of lipid crystals is related to the length and branch of fatty acids chains, the degree of unsaturation and the spatial conformation of fatty acids (Timilsena et al., 2017). The result was verified by the above results of fatty acid composition.