In Vitro Study for Lipolysis of Soybean Oil, Pomegranate Oil, and Their Blended and Interesterified Oils under a pH-Stat Model and a Simulated Model of Small Intestinal Digestion.

In this study, two in vitro digestion models were employed to compare the rate of lipolysis in soybean oil (SBO), pomegranate oil (PGO), a physical blend (PHY, 1:1 molar ratio of SBO:PGO, w/w), and their enzymatically interesterified oil (IO). In the pH-stat digestion model (emulsified oils with bile salts), PGO emulsion containing 74.7% conjugated form of linolenic acid (CLn) showed a significantly lower release rate of free fatty acid (FFA) than the other oil emulsions (p < 0.05). In FFA release rates and oil droplet sizes between PHY and IO emulsions, no significant differences were observed (p > 0.05). In a simulated model of small intestinal digestion, the lipolysis rates of SBO, PGO, PHY, and IO after digestion for 30 min in digestion fluids were 80.4%, 66.5%, 74.8%, and 77.0%, respectively. The rate of lipolysis in PGO was significantly lower than that in SBO (p < 0.05), and the lowest lipolysis rate was observed in the conjugated form of trilinolenoyl glycerol (CLn-CLn-CLn).

Antioxidant Properties of Caffeic acid Phenethyl Ester and 4-Vinylcatechol in Stripped Soybean Oil.

Caffeic acid was used to synthesize 4-vinylcatechol (4-VC) by thermal decarboxylation and to prepare caffeic acid phenethyl ester (CAPE) by esterification reaction. The identities of synthesized products were confirmed by (1)H NMR. Antioxidative activities of 4-VC and CAPE were compared with α-tocopherol and BHT in stripped soybean oil at 60 °C under the dark. To evaluate the degrees of oxidation at different concentrations and combinations, peroxide value (PV) and (1)H NMR were performed. From the results of PV, the formation of primary oxidation products (i.e., hydroperoxides) in stripped soybean oil containing 200 ppm CAPE was the slowest. The relative oxidation degree of 200 ppm CAPE (9.5%) was lower than other samples on 9 d. Similar results were obtained by (1)H NMR analysis. After 15 d of storage, levels of conjugated diene forms and aldehydes of 200 ppm CAPE sample (57.3 and 0.9 mmol/mol oil) were also lower than other treatments. In addition, 4-VC and α-tocopherol were found to have a synergistic antioxidant effect.

Relative oxidative stability of diacylglycerol and triacylglycerol oils.

To compare the oxidative stability between diacylglycerol (DAG) oil and conventional triacylglycerol (TAG) oil (that is, soybean oil), the prepared stripped diacylglycerol oil (SDO) and soybean oil (SSBO) were stored at 60 °C in the dark for 144 h. During storage peroxide values (POVs), contents of aldehydes, unsaturated fatty acids were measured to evaluate the oxidative stabilities of the 2 oils. The results showed the content of C18:2, C18:3, and total unsaturated fatty acid decreased faster in DAG oil than in soybean oil, whereas the decreased rate of C18:1 was similar in 2 oils. Also, both rate constants (K1 and K2) obtained from POV (K1 ) and total aldehydes (K2 ) indicated that DAG oil (K1 = 3.22 mmol/mol FA h(-1) , K2 = 0.023 h(-1)) was oxidized more rapidly than soybean oil (K1 = 2.56 mmol/mol FA h(-1) , K2 = 0.021 h(-1)), which was mainly due to the difference of acylglycerol composition of the 2 oils along with higher C18:3 (9.6%) in SDO than SSBO (5.7%). It is concluded that DAG was more easily oxidized than soybean oil at 60 °C in the dark for 144 h.

Effects of flavonoid glycosides obtained from a Ginkgo biloba extract fraction on the physical and oxidative stabilities of oil-in-water emulsions prepared from a stripped structured lipid with a low omega-6 to omega-3 ratio.

In this study, we have produced a structured lipid with a low ω6/ω3 ratio by lipase-catalysed interesterification with perilla and grape seed oils (1:3, wt/wt). A Ginkgo biloba leaf extract was fractionated in a column packed with HP-20 resin, producing a flavonoid glycoside fraction (FA) and a biflavone fraction (FB). FA exhibited higher antioxidant capacity than FB, showing 58.4 mmol gallic acid equivalent (GAE)/g-of-total-phenol-content, 58.8 mg quercetin equivalent (QUE)/g-of-total-flavonoid-content, 4.5 mmol trolox/g-of-trolox-equivalent antioxidant capacity, 0.14 mg extract/mL-of-free-radical-scavenging-activity (DPPH assay, IC50), and 2.3 mmol Fe2SO4 · 7H2O/g-of-ferric-reducing-antioxidant-power. The oil-in-water emulsion containing the stripped structured lipid as an oil phase with FA exhibited the highest stability and the lowest oil globule diameters (d43 and d32), where the aggregation was unnoticeable by Turbiscan and particle size analyses during 30 days of storage. Furthermore, FA was effective in retarding the oxidation of the emulsions.

Preparation of recombined milk using modified butterfats containing α-linolenic acid.

UNLABELLED: Modified butterfats (MBFs) were produced by lipase-catalyzed interesterification with 2 substrate blends (6:6:8 and 4:6:10, by weight) of anhydrous butterfat (ABF), palm stearin, and flaxseed oil in a stirred-batch type reactor after short path distillation. The 6:6:8 and 4:6:10 MBF contained 21.7% and 26.5%α-linolenic acid, respectively. Total saturated fatty acids of the MBFs ranged from 41.4% to 47.4%. The cholesterol contents of the 6:6:8 and 4:6:10 MBFs were 21.0 and 12.1 mg/100 g, respectively. In addition, the melting points of the 6:6:8 and 4:6:10 MBFs were 32 °C and 31 °C, respectively. After preparation of recombined milks (oil-in-water emulsions) with MBFs, the stability of emulsions prepared with the MBFs (6:6:8 and 4:6:10) was compared to those with ABF during 10-d storage at 30 °C. Skim milk powder (containing 1% protein) was added to prepare emulsions as an emulsifier. Microstructures of emulsions freshly prepared with the ABF and the MBFs consisted of uniform fat globules with no flocculation during 10-d storage. With respect to fat globule size distribution, the volume-surface mean droplet diameter (d(32)) of the 6:6:8 and 4:6:10 MBF emulsions ranged between 0.33 and 0.34 µm, which was similar to the distribution in ABF emulsion. PRACTICAL APPLICATION: Milk, an expensive dairy food, has been widely used in various milk-derived food products. Modified butterfats (MBFs) contain α-linolenic acid as an essential fatty acid. Emulsion stability of recombined milks (oil-in-water emulsions) with MBFs was similar to that in anhydrous butterfat emulsion during 10-d storage. They may be a promising alternative for reconstituted milks to use in processed milk-based products.

Antioxidative activities of Ginkgo biloba extract on oil/water emulsion system prepared from an enzymatically modified lipid containing alpha-linolenic acid.

UNLABELLED: The desired mix of alpha-linolenic acid (ALA)-enriched structured lipid (SL) and physically blended lipid (PB) was prepared from grape seed oil and perilla oil at a weight ratio of 3:1. The major triacylglycerol species (LnLnL) in PB was drastically increased after interesterification (SL), from 0.5% to 16.8%. After the reaction, the total unsaturated fatty acid at the sn-2 position was decreased from 98.83% in PB to 91.36% in SL. The reduction of vitamin E compounds was also observed. Compared with a PB-based emulsion, SL-based emulsions showed oxidative instability, as assessed by lipid hydroperoxide (LOOH) and 2-thiobarbituric acid-reactive substances (TBARS) values, which was mainly due to the SL which contained less LA, ALA, and ΣUSFA at the sn-2 position and less γ-tocopherol than did PB. PB-, and SL-based emulsions with Ginkgo biloba extract (GBE) which showed significantly lower values of LOOH and TBARS compared to a blank control. GBE was effective in retarding the oxidation of the emulsion by quenching the free radicals in the water phase of the emulsion and inhibiting the formation of primary and secondary oxidation products. These results indicate that GBE could be used as an antioxidant additive for stabilizing ALA-enriched emulsions. PRACTICAL APPLICATION: The results suggest the possibility to supplement Ginkgo biloba extract in alpha linolenic acid-enriched structured lipid-based emulsions which would increase the therapeutic value and enhance the antioxidant potential of the emulsions.

Studies of reaction variables for lipase-catalyzed production of alpha-linolenic acid enriched structured lipid and oxidative stability with antioxidants.

Alpha-linolenic acid (ALA) enriched structured lipid (SL) was produced by lipase-catalyzed interesterification from perilla oil (PO) and corn oil (CO). The effects of different reaction conditions (substrate molar ratio [PO/CO 1:1 to 1:3], reaction time [0 to 24 h], and reaction temperature [55 to 65 °C]) were studied. Lipozyme RM IM from Rhizomucor miehei was used as biocatalyst. We obtained 32.39% of ALA in SL obtained under the optimized conditions (molar ratio-1:1 [PO:CO], temperature-60 °C, reaction time-15 h). In SL, the major triacylglycerol (TAG) species (linolenoyl-linolenoyl-linolenoyl glycerol [LnLnLn], linolenoyl-linolenoyl-linoleoyl glycerol [LnLnL]) mainly from PO and linoleoyl-linoleoyl-oleoyl glycerol (LLO), linoleoyl-oleoyl-oleoyl glycerol (LOO), palmitoyl-linoleoyl-oleoyl glycerol (PLO) from CO decreased while linolenoyl-linolenoyl-oleoyl glycerol (LnLnO) (18.41%), trilinolein (LLL) (9.06%), LLO (16.66%), palmitoyl-linoleoyl-linoleoyl glycerol (PLL) (9.69%) were increased compared to that of physical blend. Total tocopherol content (28.01 mg/100 g), saponification value (SV) (192.2), and iodine value (IV) (161.9) were obtained. Furthermore, oxidative stability of the SL was also investigated by addition of 3 different antioxidants (each 200 ppm of rosemary extract [SL-ROS], BHT [SL-BHT], catechin [SL-CAT]) was added into SL and stored in 60 °C oven for 30 d. 2-Thiobabituric acid-reactive substances (TBARS) value was 0.16 mg/kg in SL-CAT and 0.18 mg/kg in SL-ROS as compared with 0.22 mg/kg in control (SL) after oxidation. The lowest peroxide value (POV, 200.9 meq/kg) and longest induction time (29.88 h) was also observed in SL-CAT.

Oxidative comparison of emulsion systems from fish oil-based structured lipid versus physically blended lipid with purple-fleshed sweet potato (Ipomoea batatas L.) extracts.

The effects of the purple-fleshed sweet potato extract (PFSPE) on oxidation stabilities of a model oil-in-water emulsion prepared with enzymatically synthesized fish oil-soybean oil structured lipid (SL) versus physically blended lipid (PBL) without modification were evaluated. The anthocyanins in PFSPE were analyzed and identified by HPLC-MS. The fatty acid composition of SL was similar to that of PBL, except palmitic acid (1.48 in PBL and 9.61% in SL) and linoleic acid (62.47 in PBL and 49.58% in SL). Peonidin 3-caffeoylsophoroside-5-glucoside, peonidin-3-(6',6'-caffeoylferuloylsophoroside)-5-glucoside, peonidin-dicaffeoylsophoroside-5-glucoside, peonidin 3-(6',6"-caffeoyl-p-hydroxybenzoylsophoroside)-5-glucoside were identified as the major anthocyanin compounds in PFSPE. Different levels (200, 500, 1000 ppm) of PFSPE were added into both SL- and PBL-based emulsions, with 200 ppm catechin as comparison. Oxidation was monitored by measuring the peroxide value and thiobarbituric acid reactive substances. The antioxidant activity of PFSPE increased with an increased concentration, the concentration of 1000 ppm showed high antioxidant ability similar to that of catechin in both PBL- and SL-based oil-in-water emulsions. It is notable that the SL-based emulsion appeared to have better oxidative stability than the PBL-based emulsion.