Xiaosan Wang

The effect of ultrasound on enzymatic degumming process of rapeseed oil by the use of phospholipase A1

Comparative studies of enzymatic degumming process of rapeseed oil were carried out in mechanical-stirring and ultrasonic-assisted mechanical-stirring systems. The influences of enzyme dosage (10-50 mg/kg), pH (4.5-6), temperature (45-65 °C), water amount (1-3%), ultrasonic power (0.06-0.09 W/cm(3)) and reaction time were investigated subsequently. A suitable ultrasonic power of 0.07 W/cm(3) was determined to guarantee satisfactory degumming efficiency and enzyme activity. Compared to the mechanical-stirring system, optimum temperature of phospholipase A (PLA) in the ultrasonic-assisted mechanical-stirring system was about 5 °C higher, while the effects of pH on both of the two systems were quite similar. Less time and water were used in the ultrasonic-assisted mechanical-stirring system for enzymatic degumming. The study on the quality changes of degummed oils showed that ultrasound could accelerate the oxidation of edible oils due to the effect of cavitation, thus more attention should be paid on the oxidative stability in the further application.

A novel method for the synthesis of symmetrical triacylglycerols by enzymatic transesterification.

A novel two-step enzymatic method is described in this study to synthesize symmetrical triacylglycerols (TAGs) with arachidonic acid (ARA) at the sn-2 position. The processes included the synthesis of 2-monoacylglycerols (2-MAGs) rich in 2-arachidonoylglycerol (2-AG) by enzymatic ethanolysis and the synthesis of symmetrical TAGs by enzymatic transesterification between 2-MAGs and vinyl palmitate. Under the optimal conditions, desired symmetrical TAGs were obtained at 89% yield. In this study, vinyl palmitate rather than palmitic acid was used as a novel acyl donor to react with 2-MAGs. It was the first study reporting the synthesis of symmetrical TAGs by enzymatic transesterification. The reaction using fatty acid vinyl ester as acyl donor is irreversible and temperature is low. Low-temperature reaction greatly suppressed the acyl migration of 2-MAGs and the irreversible reaction is much more effective compared to reversible reactions using free fatty acid and fatty acid ester as acyl donors.

Screening of glucosinolate-degrading strains and its application in improving the quality of rapeseed meal

Two myrosinase-producing fungi, Lichtheimia sp. JN3C and Aspergillus terreus, were newly isolated from decayed rapeseed meal samples obtained in Anhui Province, China. After preliminary screening, re-screening and combination of two screened strains with a yeast, an optimal composite strain to ferment rapeseed meal was obtained. Results demonstrated that the glucosinolate content of products with two molds fermentation was overall lower than that with single strain fermentation. Fermentation with composite strains containing Candida tropicalis CICIM Y0079(T) had a similar glucosinolate content, whereas the protein content was remarkably increased compared to two molds fermentation. Under sterile conditions, a 96-h fermentation with the composite strains resulted in the degradation of 66.2% of crude fiber, 28.3% of phytic acid, and 98% of total glucosinolates, which are responsible for goiter, and an increase of the protein and tannins content by 27.4 and 15.8%, respectively. In addition, glucosinolates and protein content under the non-sterile condition were not significantly different compared to the sterile condition. The fermentation greatly improved the nutritional quality of rapeseed meal by both degrading undesired substances and increasing protein content.

Analysis of phospholipids in Schizochytrium sp. S31 by using UPLC-Q-TOF-MS

Phospholipids are the main constituent of cell membranes and play multiple roles in cells, in forming the permeability barrier, supporting matrix, surfaces for many catalytic processes, and precursors of signal processing and macromolecular synthesis. Hydrophilic interaction (HILIC) ultra-performance liquid chromatography (UPLC) coupled with quadrupole time of flight (Q-TOF) mass spectrometry (MS) was used to analyze the composition of phospholipids from Schizochytrium sp. S31. Phosphatidyl-cholines, -ethanolamines, -inositoles, and -glycerol, and phosphatidic acid were separated by using an acetonitrile/ammonium formate gradient mobile phase. The structures of 70 phospholipids were identified by LC-MS/MS measurements in negative ion mode. The main phospholipid in Schizochytrium sp. S31, phosphatidylcholine, accounted for 49.8% of the total phospholipids, and the major phospholipid fatty acids were C16 : 0 and DHA.

Comparison of solvents for extraction of krill oil from krill meal: Lipid yield, phospholipids content, fatty acids composition and minor components

The effects of seven different extraction solvents (ethanol, isopropanol, acetone, ethyl acetate, isohexane, n-hexane, and subcritical butane) on the lipid yield and quality of the oil extracted from krill meal were investigated in this study. Phospholipids (PL), fatty acids (FA) composition and minor components including sterols, astaxanthin, vitamin A and tocopherols in the extracted krill oil were analyzed. The results indicated that ethanol and isopropanol led to comparatively higher lipid yields (16.33 and 14.52%, respectively) and PL contents (39.2 and 38.7%, respectively) but lower contents of the minor components than the other solvents. The krill oil extracted with acetone had the lowest PL content (20.63%) but contained more astaxanthin (206.74mg/kg), vitamin A (27.84mg/100g), and sterols (39.00mg/g). Moreover, high levels of n-3 FA were present in the extracts with high PL contents. Further analysis revealed that 23.65-28.10% of eicosapentaenoic acid (EPA) and 16.71-21.03% of docosahexaenoic acid (DHA) were present in the PL, while only 2.83-3.48% of EPA and 1.40-1.74% of DHA were detected in the triacylglycerols (TAG). In addition, subcritical butane proved to be an alternative to n-hexane and isohexane; krill oil extracted with these three solvents had similar qualities.

Oxidative stabilities of mango kernel fat fractions produced by three-stage fractionation

ABSTRACT Trans-free mango kernel fat stearins and oleins were produced by three-stage acetone fractionation to achieve the sufficient utilization of fat. Fatty acid and triacylglycerol compositions, slip melting points, iodine values, micronutrient (tocopherol, sterol, and squalene) levels, as well as oxidative stability indexes of the fractions were analyzed to evaluate their qualities. The most abundant fatty acids in the stearins were saturated fatty acids (57.3–65.1%, mainly including palmitic, stearic, and arachidic acids), and the major triacylglycerols were symmetrical monounsaturated types (78.3–93.7%). The unique properties make the stearins show highest slip melting points 34.7–38.3°C and oxidative stability indexes (12.0–14.2 h), and very suitable for the manufacturing of hard chocolate fats. The oleins contained high percentages of monounsaturated (48.3–53.7%) and polyunsaturated fatty acids (7.8–8.5%). Their oxidative stability indexes (6.3–6.7 h) were lower than the stearins but higher than common commercial oils. About 85.2% of tocopherol, 99.2% of sterol, and 79.2% of squalene were transferred to the liquids after fractionation, which could improve their antioxidant abilities. Further multiple linear regression analyses between oxidative stability indexes and fat compositions revealed that polyunsaturated fatty acid and sterol were the main factors that affect the oxidative stabilities of the fractions. The results suggested that the moderated refining techniques should be developed to retain more sterol to improve the oxidative stabilities and nutritive values of the fats.

Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids

A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil.

The Synthesis of Methyl Oleate Catalyzed by Phosphotungstic Acid Immobilized on the Functionalized Palygorskite

Abstract Esterification of oleic acid with methanol was investigated using tungstophosphoric acid (H3PW12O40) immobilized on the 3-aminopropyltriethoxysilane (H2N(CH2)3Si(OC2H5)3) functionalized palygorskite. Among different loading catalysts, 15% (w/w) H3PW12O40 immobilized onto functionalized palygorskite showed stable and substantially high activity with about 90% oleic acid conversion. Immobilized catalysts were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, and temperature programmed desorption of NH3 for their surface element compositions and chemical states, crystallization, and acid strength, respectively. Characterization results indicated that H3PW12O40 was chemically and uniformly dispersed on modified palygorskite.

Production of sn-1,3-distearoyl-2-oleoyl-glycerol-rich fats from mango kernel fat by selective fractionation using 2-methylpentane based isohexane

High-purity isohexane containing 88.12% 2-methylpentane, which has a higher polarity than industrial hexane, was selected to selectively fractionate mango kernel fat to produce 1,3-distearoyl-2-oleoyl-glycerol (SOS)-rich fat. The three-stage fractionation process was optimized by considering the stearin yield and its SOS content to obtain a third stearin (TS). This fat contained a high percentage of SOS (69.2%) with only 0.8% diacylglycerol. Mass spectra and sn-2 fatty acid analyses further revealed that the TS was mainly composed of symmetrical monounsaturated triacylglycerols. Compared with cocoa butter (CB), the unique composition of the TS improved its thermal properties (35.6% and 0% solid fat content at 35°C for the TS and CB, respectively). In particular, tempered binary fat blends, which were composed of 20-50% TS and 50-80% CB, showed acceptable compatibility at 20-28°C. The TS could be utilized by chocolate manufacturers to make products suitable for sale and consumption in tropical conditions.

Synthesis of 1,3-distearoyl-2-oleoylglycerol by enzymatic acidolysis in a solvent-free system

1,3-Distearoyl-2-oleoylglycerol (SOS) is widely used as a cocoa butter improver and an anti-blooming agent in the chocolate industry. In this study, an effective process was developed to prepare SOS by enzymatic acidolysis. Under optimal reaction conditions (substrate molar ratio of 12, NS40086 loading of 10%, a solvent-free system, 75°C for 4h), a SOS yield of 70.2% was obtained. Subsequently, two-step purification was applied to purify the crude SOS product. Free fatty acids were completely removed after molecular distillation. After acetone fractionation, the purity of SOS reached 92.2% with an 85.1% recovery. Comparison of various physicochemical properties of purified SOS and a commercial cocoa butter improver showed their properties to be similar. This study provides an effective and sustainable process for the synthesis of SOS product, which is expected to be used as a high-quality cocoa butter improver or an anti-blooming agent in the chocolate industry.