Faculty Publications
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Item A new strategy to refine crude Indian sardine oil(Japan Oil Chemists Society yukagaku@jocs-office.or.jp, 2017) Charanyaa, S.; Belur, B.D.; Iyyaswami, R.Current work aims to develop a refining process for removing phospholipids, free fatty acids (FFA), and metal ions without affecting n-3 polyunsaturated fatty acid (n-3 PUFA) esters present in the crude Indian sardine oil. Sardine oil was subjected to degumming with various acids (orthophosphoric acid, acetic acid, and lactic acid), conventional and membrane assisted deacidification using various solvents (methanol, ethanol, propanol and butanol) and bleaching with bleaching agents (GAC, activated earth and bentonite) and all the process parameters were further optimized. Degumming with 5%(w/w) ortho phosphoric acid, two stage solvent extraction with methanol at 1:1 (w/w) in each stage and bleaching with 3% (w/w) activated charcoal loading, at 80ºC for 10 minutes resulted in the reduction of phospholipid content to 5.66 ppm from 612.66 ppm, FFA to 0.56% from 5.64% with the complete removal of iron and mercury. Under these conditions, the obtained bleached oil showed an enhancement of n-3 PUFA from 16.39% (11.19 Eicosapentaenoic acid (EPA) + 5.20 Docosahexaenoic acid (DHA)) to 17.91% (11.81 EPA + 6.1 DHA). Replacing conventional solvent extraction with membrane deacidification using microporous, hydrophobic polytetrafluoroethylene membrane (PTFE), resulted in a lesser solvent residue (0.25% (w/w)) in the deacidified oil. In view of lack of reports on refining of n-3 PUFA rich marine oils without concomitant loss of n-3 PUFA, this report is significant. © 2017 by Japan Oil Chemists’ Society.Item Enhancement of n-3 polyunsaturated fatty acid glycerides in Sardine oil by a bioimprinted cross-linked Candida rugosa lipase(Elsevier Inc. usjcs@elsevier.com, 2018) Sampath, C.; Belur, P.D.; Iyyaswami, R.Considering the advantages of bioimprinting and carrier free immobilization, cross-linked enzyme aggregates (CLEA) were prepared by using bioimprinted Candida rugosa lipase (CRL) with Bovine serum albumin (BSA), Polyethyleneimine and glutaraldehyde. Effect of various factors such as CRL-Oleic acid ratio, CRL-BSA ratio, CRL- Polyethyleneimine ratio, glutaraldehyde loading, cross-linking time etc., on lipase activity recovery and aggregate yield were studied and optimized. This immobilized lipase (CRL-CLEA) was used for the selective hydrolysis of ester linkages of non-PUFA glycerides, with an aim to concentrate EPA and DHA glycerides in the Sardine oil. Imprinting with oleic acid in the presence of ethanol and Tween 60, and further immobilization with co-aggregates and cross-linking agent showed 10.4 times higher degree of hydrolysis compared to free enzyme. As result, 2.83-fold increase of n-3 PUFA content in deacidified oil was obtained by using CRL-CLEA. The resultant oil had negligible di- and triglycerides content, proving higher efficiency in hydrolysing ester bonds of fatty acids, other than n-3 PUFA. Reusability studies showed CRL-CLEA could be reused up to 5 runs without a substantial reduction in its performance. Improvement in degree of hydrolysis, thermostability, efficiency of hydrolysis and reusability were achieved due to bioimprinting and subsequent immobilization of CRL in the form of CLEA. © 2017 Elsevier Inc.Item Designing of A Synergistic Mixture of Natural Antioxidants Through Statistical Approaches for Enhancing the Oxidative Stability of Sardine Oil(Enviro Research Publishers, 2023) Mishra, S.K.; Belur, P.D.; Chandrasekar, V.; Iyyaswami, R.Given the diverse routes of oxidation and a variety of oxidation products, the right combination of antioxidants is expected to exhibit synergistic effects in retarding refined sardine oil oxidation. In this study, a full factorial design (24) was utilized to choose a combination of natural antioxidants which exhibit interactive effect and response surface modelling (RSM) was used to identify the optimal concentration of the selected antioxidant mixture which exhibit synergistic effect. Catechin and resveratrol showed a strong interactive effect among the four natural antioxidants (sinapic acid, vanillic acid, catechin, and resveratrol) studied in sardine oil stored for 50 days at 25ºC under darkness. Two optimal concentrations of interactive antioxidants were found through RSM. Catechin and resveratrol at 0.5 mM and 0.625 mM respectively, exhibited a strong synergistic effect whereas, at 0.5 mM and 3.7 mM respectively, showed prooxidant effect. This is the first of its kind report on the formulation of a synergistic antioxidant mixture for retarding oxidation using statistical approaches. © 2023 The Author(s).Item Synthesis and characterization of 3,4-dihydroxyphenyl acetic acid esters and study of their efficacy in bulk fish oil(Elsevier Ltd, 2024) Arunachalam, S.S.; Chandrasekar, V.; Belur, P.D.Lipophilization of natural antioxidants is a proven strategy to enhance the solubility in bulk oil systems, thereby increasing their efficacy against oxidative degradation. This study aims to synthesize esters of 3,4-dihydroxyphenylacetic acid (3,4-DHPA) using Amberlyst-15 and to study the application of these esters in refined fish oil. Lipophilic esters were synthesized by esterification and transesterification of 3,4-DHPA in various solvent systems. Esters of methanol, butanol and hexanol were obtained with percent conversion of 81.1, 69.3 and 78.8 respectively, and were subjected to molecular characterization and in vitro oxidant assays. The 3,4-DHPA and its methyl ester showed 36% reduction in the TOTOX value over 30 days of storage. The length of the acyl chain in the ester was found to exert a high influence on its efficacy and lipophilicity. This is the first report of 3,4-DHPA and its lipophilic esters studied for enhancing the oxidative stability of fish oil. © 2024 Elsevier LtdItem Effect of combinations of 3,4-dihydroxyphenylacetic acid and its esters on the oxidative stability of fish oil–containing trace water(John Wiley and Sons Inc, 2024) Arunachalam, S.S.; Chandrasekar, V.; Belur, P.D.The current study aims to comprehend the effect of the various combinations of 3,4-dihydroxyphenylacetic acid (3,4-DHPA) and its esters in varying molar ratios on retarding oxidation in bulk refined fish oil in the presence of 0.3% w/w water. All the esters and 3,4-DHPA exhibited better performance than the synthetic antioxidant butylated hydroxytoluene. In the presence of trace water, the parent compound was found to have a synergistic effect with hexyl ester when used at a molar ratio of 2:1, respectively, exhibiting a higher percent reduction among all the esters and their combinations. The study also showed that the presence of extraneous water can significantly accelerate the oxidation (twofold) in a bulk fish oil system. This suggests that the microenvironment of the oil is altered when water is present and that association colloids play a key role in enhancing the rate of oxidation. Thus, while designing a competent mixture of antioxidants, the specific site of oxidation involved and the surface-active components should be taken into consideration to efficiently retard oxidation. Practical Applications: Analyzing the impact of trace amounts of water on the efficiency of natural antioxidants, including 3,4-DHPA and its lipophilic esters, helps to comprehend the required optimal antioxidant concentrations for such a dynamic bulk oil system. The study finds application in controlling oxidation in PUFA-rich oils containing surface-active minor components that can accelerate oxidation. The results of the study show that 3,4-DHPA and its esters could be a potential replacement for the synthetic antioxidant BHT in all aspects. © 2024 Wiley-VCH GmbH.