Extraction Conditions and Moisture Content of Canola Flakes as Related to Lipid Composition of Supercritical CO2 Extracts

Canola flakes obtained before and after conventional cooking were extracted with supercritical carbon dioxide (SC-CO₂) at 35–75°C and 20.7–62.0 MPa. Moisture content was adjusted to 12.7–42.5% (w/w, moisture-and oil-free basis). Moisture content of residual flakes after extraction was monitored. Amount of extract recovered increased with increasing temperature and pressure, except at 20.7 MPa pressure it decreased with temperature indicating a crossover of the solubility isotherms. Some water was co-extracted with canola oil. Free fatty acid (FFA) concentration of the extracts increased with decreasing pressure due to a decrease in triglyceride (TG) solubility. Oleic and linolenic acids had highest concentrations in the FFA fractions of all extracts. The lowest TG content of extracts was attained at 20.7 MPa and 75°C. The effect of extraction conditions was more pronounced than seed pre-treatments on yield and composition of SC-CO₂ extracts.     

Conjugated linoleic acid and vaccenic acid in rumen, plasma, and milk of cows fed fish oil and fats differing in saturation of 18 carbon fatty acids

The objective of this study was to examine the effect of feeding fish oil (FO) along with fat sources that varied in saturation of 18 carbon fatty acids (high stearic, high oleic, high linoleic, or high linolenic acids) on rumen, plasma, and milk fatty acid profiles. Four primiparous Holstein cows at 85 d in milk (+/- 40) were assigned to 4 x 4 Latin squares with 4-wk periods. Treatment diets were 1) 1% FO plus 2% commercial fat high in stearic acid (HS); 2) 1% FO plus 2% fat from high oleic acid sunflower seeds (HO); 3) 1% FO plus 2% fat from high linoleic acid sunflower seeds (HLO); and 4) 1% FO plus 2% fat from flax seeds (high linolenic; HLN). Diets were formulated to contain 18% crude protein and were composed of 50% (dry basis) concentrate mix, 25% corn silage, 12.5% alfalfa silage, and 12.5% alfalfa hay. Milk production, milk protein percentages and yields, and dry matter intake were similar across diets. Milk fat concentrations and yields were least for HO and HLO diets. The proportion of milk cis-9, trans-11 conjugated linoleic acid (CLA; 0.71, 0.99, 1.71, and 1.12 g/100 g fatty acids, respectively), and vaccenic acid (TVA; 1.85, 2.60, 4.14, and 2.16 g/100 g fatty acids, respectively) were greatest with the HLO diet. The proportions of ruminal cis-9, trans-11 CLA (0.09, 0.16, 0.18, and 0.16 g/100 g fatty acids, respectively) were similar for the HO, HLO, and HLN diets and all were higher than for the HS diet. The proportions of TVA (2.85, 4.36, 8.69, and 4.64 g/100 g fatty acids, respectively) increased with the HO, HLO, and HLN diets compared with the HS diets, and the increase was greatest with the HLO diet. The effects of fat supplements on ruminal TVA concentrations were also reflected in plasma triglycerides, (2.75, 4.64, 8.77, and 5.42 g/100 g fatty acids, respectively); however, there were no differences in the proportion of cis-9, trans-11 CLA (0.06, 0.07, 0.06, and 0.07 g/100 g fatty acids, respectively). This study further supports the significant role for mammary delta-9 desaturase in milk cis-9, trans-11 CLA production.     

液质联用分析常见植物油甘油三酯

采用高效液相色谱-串联飞行时间质谱法分析了常见植物油如大豆油、芝麻油、花生油、特级初榨橄榄油、葵花籽油、玉米油、油茶籽油、棉籽油和菜籽油的甘油三酯。结果显示每种植物油甘油三酯的种类和含量均不相同。该方法测定甘油三酯有效可行,可为甘油三酯结构信息研究及油脂掺伪鉴别提供基础支持。     

Transitions of saturated monoacid triglycerides: Modeling conformational change at glycerol during α→β′→β transformation

The glycerol region geometry of modeled saturated monoacid triglycerides was altered by bond rotations and minor angle distortions to convert theoretical α-forms into bent β′- and β-forms. Direct α to β conversion involves lateral disruption of fatty chain packing to generate side-chain character typical of the β-form. Such disruption, which could contribute to fat bloom, allows additional molecular movement and shifts in molecular mechanics energy (MME) that may approximate thermal changes observed by differential scanning calorimetry during α to β transformations. Energy calculations at 100 points throughout each transformation identified plausible conversion routes. A two-stage conversion, α to either of two stereospecific β′-forms bent at glycerol followed by subsequent conversion to β, showed less chain movement and more favorable MME than direct α to β conversion. The preferred path, based on energy profiles of each conversion, involves a β′-D form and rotation of carbonyl to α-carbon bonds in chain #2 and a side chain (chain #3).     

Screening catalytic lipase activities with an analytical supercritical fluid extractor

Two different screenings of several commercial lipases were performed to find a lipase with superior performance for the conversion of lipid moieties to their fatty acid methyl ester (FAME) derivatives under supercritical conditions. The first screening was done under hydrolytic conditions in a buffer. The second screening was done under supercritical conditions with CO₂, utilizing some of the same lipases for the methanolysis of different lipids. For the substrates studied, there was a significant difference in lipase activity under the two above conditions. Significant hydrolytic activity was demonstrated for three different lipid types (triglycerides, sterols, and phospholipids) with Lipase PS30, but when the same lipase was immobilized on an Accurel carrier (polypropylene), the activity decreased considerably. The opposite was found for Lipase G, which showed strong activity when immobilized and under supercritical conditions. Furthermore, Chirozyme L-1 was superior under supercritical conditions. The altered substrate specificity that some of these lipases show in supercritical CO₂ suggests several interesting synthetic options and applications under these conditions.     

Dynamic polymorphic phase transitions in a model binary triglyceride system measured by position-sensitive X-ray diffraction methods

X-ray diffraction measurements have been made on a binary mixture of pure tripalmitin and tristearin which undergoes particular polymorphic phase transitions on heating from the solid. The results were obtained using a position-sensitive detector which can record the whole diffraction pattern in time periods less than a minute. This allows many patterns to be recorded during the transformations where heating rates can be up to several^oC/min. As such the transitory existence of the intermediate β' phase has been unambiguously identified. The results serve to exhibit the usefulness of the X-ray apparatus and indicate its potential for future studies in dynamic crystallization and melting. On behalf of Loders-Croklaan     

Rapid Quantification of Low-Viscosity Acetyl-Triacylglycerols Using Electrospray Ionization Mass Spectrometry

Acetyl‐triacylglycerols (acetyl‐TAG) possess an sn‐3 acetate group, which confers useful chemical and physical properties to these unusual triacylglycerols (TAG). Current methods for quantification of acetyl‐TAG are time consuming and do not provide any information on the molecular species profile. Electrospray ionization mass spectrometry (ESI–MS)‐based methods can overcome these drawbacks. However, the ESI–MS signal intensity for TAG depends on the aliphatic chain length and unsaturation index of the molecule. Therefore response factors for different molecular species need to be determined before any quantification. The effects of the chain length and the number of double‐bonds of the sn‐1/2 acyl groups on the signal intensity for the neutral loss of short chain length sn‐3 groups were quantified using a series of synthesized sn‐3 specific structured TAG. The signal intensity for the neutral loss of the sn‐3 acyl group was found to negatively correlated with the aliphatic chain length and unsaturation index of the sn‐1/2 acyl groups. The signal intensity of the neutral loss of the sn‐3 acyl group was also negatively correlated with the size of that chain. Further, the position of the group undergoing neutral loss was also important, with the signal from an sn‐2 acyl group much lower than that from one located at sn‐3. Response factors obtained from these analyses were used to develop a method for the absolute quantification of acetyl‐TAG. The increased sensitivity of this ESI–MS‐based approach allowed successful quantification of acetyl‐TAG in various biological settings, including the products of in vitro enzyme activity assays.     

Glycerolysis of fats and methyl esters

The glycerolysis of methyl esters and triglycerides with crude glycerol, a coproduct from the transesterification of triglycerides, was studied. Three procedures were followed for this conversion. The first procedure was a one-step glycerolysis with methyl esters. The second procedure was a two-step process. This procedure involved an initial partial glycerolysis with methyl esters, followed by fat glycerolysis. The third procedure was a simultaneous glycerolysis with methyl esters and triglycerides. In the glycerolysis with methyl esters, the removal of methanol is vital to the production of mono- and diglycerides. Methanol was removed either by drawing vacuum on the reactor or by stripping methanol out by means of an inert carrier gas (nitrogen). Different molar ratios of methyl esters to glycerol were tested in the first two processes. At low concentration of methyl esters, total conversion of methyl esters to mono- and diglycerides was achieved. As the concentration of methyl esters was increased, the conversion of methyl esters to mono- and diglycerides was decreased. Furthermore, the ratio of mono- to diglycerides was also higher at lower concentrations of methyl esters. The conversion of triglycerides in the two-step process with crude glycerol was similar to a one-step fat glycerolysis with pure glycerol. The composition of different components and the ratio of mono- to diglycerides were also comparable.     

Synthesis of structured triglycerides from peanut oil with immobilized lipase

Structured triglycerides (ST) that contain medium- and long-chain fatty acids were synthesized by lipase-catalyzed interesterification between tricaprylin and peanut oil. To select appropriate enzymes, we investigated nine commercial lipase preparations for their ability to hydrolyze pure triglycerides as well as natural oils. Three microbial lipases from Rhizomucor miehei (RML), Candida sp. (CSL), and Chromobacterium viscosum (CVL) gave good results, and immobilized preparations were used in the interesterification. RML gave the highest yields of ST (73%, 40°C), although its hydrolytic activity toward triolein was low. As the temperature was raised to 50°C, the yield of ST increased to 79%. After 120 h reaction time, remaining activities were high for CSL (71%), moderate for CVL (48%), and low for RML (20%). Parts of this paper were presented as a poster at the Biochemical Engineering Conference IX, May 1995, Davos, Switzerland.