Flaxseed Oil: Extraction Using Ultrasound Assistance, Stabilization With Compound Antioxidants, And Microencapsulation

Flaxseed oil (FO) is one among unstable vegetable oils due to its high content of polyunsaturated fatty acids (PUFA) which is mainly composed of alpha linolenic acid (ALA). Among the effective ways to ensure a high quality of lipids and lipid-containing products and prolong their storage time, the addition of suitable antioxidants and use of microencapsulation are considered to have good techno-economic values. The stabilization of flaxseed oil is expected to help increase its shelf life and use to different applications.FO is found recently to have many beneficial functions to human health. ALA, which occurs in large amounts in FO, is one among the essential fatty acids and may also be converted in the body to eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA); hence, it may help for essential growth and development and also is believed to be associated with the prevention and treatment of heart disease, arthritis, inflammatory and autoimmune diseases. The major tocopherols found in FO are y-tocopherols which are considered more potent in inhibiting platelet aggregation and thrombogenesis, low density lipoprotein and delaying intra-arterial thrombus formation.Orthogonal array design (L9 (3)4) was applied to optimize FO yield,β-andγ-tocopherols yields (mainly tocopherols found in FO) and total oxidation value (totox value) using ultrasound assistance extraction (UAE). The optimized results were then compared with the one extracted by Soxhlet extraction (S.E). The results revealed that 80.05% FO yield can be extracted for 30 min,30℃and 10:1 solvent/solid ratio by UAE compared to 100% yield obtained by 8 h,60℃and 20:1 solvent/liquid ratio by S.E.β-andγ-tocopherols yielded 40.39 mg/100 g oil at 30 min,20℃and 10:1 solvent/liquid ratio by UAE compared to 56.37 mg/100 g oil by S.E. Totox value of FO by UAE was lower compared to S.E. No significant different were shown for fatty acids between both extraction methods (p<0.025). UAE is capable to save time, energy and is environmental friendly.Stabilizing of FO with individual and different mixtures of antioxidants was studied. In vitro tests of tea polyphenols (Tp), tert-butylhydroquinone (TBHQ) and monoglyceride citrate (MGC) with their different mixtures as to their reducing power revealed that the reductive capability of Tp+TBHQ was found to be stronger compared to other mixture of antioxidants at almost all concentration levels studied (p< 0.025). However, DPPH radical scavenging activity had shown both the ternary mixture and the binary mixture of Tp+TBHQ of the antioxidants were more effective compared to other mixtures. Oxidation stability of FO in the absence and presence of antioxidants as a function of time at high temperature was also investigated. Tp, TBHQ and MGC with their mixtures at different concentration levels were used whereby peroxide value (PV) and p-anisidine value of FO were determined as indicators of oxidation at 60℃during 20 days. The results revealed that TBHQ200+Tp400+MGC200, Tp400+TBHQ200, TBHQ200+MGC200 and Tp2oo+TBHQ100 as the best for controlling oxidation in FO (subscript denotes in mg/kg). On Rancimat tests conducted, showed the most effective antioxidant formulation was ternary mixture of TBHQ200+Tp400+MGC200 followed by TBHQ200+MGC200, Tp400+TBHQ200 TBHQ100+Tp200+MGC100, TBHQ100+MGC100 and Tp200+TBHQ100.Due to worldwide preference of naturalism and minimization in using food additives, the use of multi-component antioxidants, wherein some natural substances is included to achieve synergistic antioxidative activity, Tp+TBHQ would be a better choice for minimizing the additions of synthetic antioxidants in food lipids.Response surface methodology (RSM) was used to establish optimum conditions for FO, soy lecithin and xanthan gum to yield stable flaxseed oil droplet (FOD) size and high microencapsulation efficiency (M.E.E). Gum arabic and maltodextrin were used at constant ratio of 1:1. FO loading (20-35%), lecithin (1-2%) and xanthan gum (0.1-0.4%) were studied regarding their effects on emulsion and the spray dried powder. Results indicated that response surface models significantly fitted to all response variables studied. Regression models describing variations of responses of FOD size and M.E.E showed high coefficient of determination (R2) of 0.9963 and 0.9944 respectively. Overall numerical optimization predicted a desirable system attainable using gum arabic and maltodextrin each at an amount of 10%(w/w),22.78%(w/w) FO loading,1.14%(w/w) soy lecithin and 0.10%(w/w) xanthan gum, which resulted into FOD size of 446.9nm, M.E.E of 92.3% and good stability towards oxidation during 10 weeks of storage tests.