Comparison of Methods for Separating Polar Lipids from Oat Oil

Polar lipids of crude oat oil were investigated. Oat oil was separated from oats by extraction with isopropanol. Polar lipids were fractionated from crude oil by supercritical CO₂-extraction, by ultrafiltration in hexane and by water degumming. The polar fraction from CO₂-extraction had the highest phospholipid and lowest tocopherol content. The polar fractions made by different methods possessed similar antioxidative properties. However, the polar lipids from oats were more powerful antioxidants than those made from soybean or rapeseed oil.     

Antioxidant Activity of Oat Malt Extracts in Accelerated Corn Oil Oxidation

Oat cultivar AC Vermont was malted to concentrate antioxidants, milled to fractionate only the endosperm portion and extracted with methanol to isolate the crude antioxidants. The oat malt antioxidant fraction was assessed as a natural antioxidant based upon enhancing the stability of corn oil against oxidation and compared to the synthetic antioxidant butylated hydroxytoluene (BHT). The induction time (time required for the formation of 10 meq hydroperoxide per kilogram corn oil thermally oxidized) was used to measure antioxidant activity of oat antioxidant or BHT. The protection factor achieved by crude oat malt antioxidant extract concentrate at 0.26% (2,600 μg/g) was comparable to BHT (75 μg/g). The antioxidant activity of the oat and barley malt extract concentrates was not significantly different. However, the extract concentrate of oat malt had 44% less color compared to that of barley malt at equal concentrations showing its potential as a natural food antioxidant.     

The Identification of Mono-, Di-, Tri-, and Tetragalactosyl-diacylglycerols and their Natural Estolides in Oat Kernels

Oat kernels were extracted with methanol, and glycolipid-enriched fractions were prepared using silica solid phase extraction. Using direct infusion electrospray ionization (ESI) tandem mass spectrometry (MS), high performance liquid chromatography (HPLC)-ESI-MS, and HPLC-atmospheric pressure chemical ionization (APCI)-MS, we confirmed previous reports that digalactosyldiacylglycerol (DGDG) was the most abundant glycolipid in oat kernels and confirmed a previous report of the presence of a DGDG mono-estolide in oat kernels. In the current study we also identified several additional natural galactolipid estolides: two new DGDG estolides (di- and tri-estolides), two trigalactosyldiacylglycerol (TriGDG) estolides (mono- and di-estolides), and one tetragalactosyldiacylglycerol (TetraGDG) estolide (mono-estolide). The levels of total galactolipid estolides in oat kernels were estimated to be about 29% of the total glycolipid fraction. To our knowledge, this report is the first evidence of natural di- and tri-estolides of polar lipids.     

Oat lipids

Oats are a significant world crop. While nutritional interest in food oats has concentrated on oats as a source of dietary fiber, the lipid component has both nutritional and technological potential. Thus, the lipid fraction of the oat grain determines in large measure its energy content and has a significant impact on nutritional quality. The oat lipids mediate the pasting properties of oat starch and hence influence functionality. Lipids are also implicated in the flavor/off-flavor attributes of oats. These aspects of oat lipids are reviewed together with analytical methods for assessing the lipid content of oats.     

Oat Oil: Refining and stability

Oil obtained by petroleum ether extraction of Dal oats was refined by conventional methods. Degumming loss was reduced to 15% by degumming in hexane solution and partially neutralizing the oil with sodium hydroxide. The free fatty acid was 6~8%, and alkali refining losses were 25~30%. Oat oil was bleached successfully with charcoal and deodorized. Stability of the refined oil was compared with soybean oil at 25 and 55 C by peroxide values and organoleptic tests. Stability of oat oil was increased by the addition of citric acid and was significantly greater than that of soybean oil, especially at 25 C. Oat oil contained significant amounts of α-tocopherol, but ferulic and caffeic acids, antioxidants important in whole oats, were not extracted by hexane. Paper No. J-8657 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA, Project No. 2143.     

Antioxidative Effects of Oat Oil and its Fractions

The antioxidative properties of oat oil and its fractions were studied using the Rancimat method and lard, tallow and soybean oil as substrates. Oat oil extracted with isopropanol increased the induction time of oxidation of lard and tallow from 2 to 8-fold compared with the corresponding times without antioxidants, when applied at 1.0 to 5% concentrations. The same increase in stability was achieved with 0.25 to 1.5% concentrations of the separated fractions. The most effective fraction was the lecithin fraction isolated by supercritical CO₂ extraction. Almost equal results were achieved with a single-step ultrafiltration. Effects on the stability of soybean oil were similar but weaker.     

No evidence of differential effects of SFA,MUFA or PUFA on post-ingestive satiety and energy intake: a randomised trial of fatty acid saturation

Background  

High fat diets have long been associated with weight gain and obesity, and the weak satiety response elicited in response to dietary lipids is likely to play a role. Suppression of appetite and food intake has consistently been shown to be diminished with high fat relative to either high protein or carbohydrate meals. There is however some evidence that the satiating capacity of lipids may be modulated when physicochemical properties are altered, but studies investigating the effect of lipid saturation on appetite have generated inconsistent findings. This study investigated the effects of changes in fatty acid saturation on post-ingestive satiety and energy intake.     

Extraction of Oat Lipids and Phospholipids Using Subcritical Propane and Dimethyl Ether: Experimental Data and Modeling

Effects of subcritical solvents (propane, dimethyl ether (DME), and their 1:1 mixed solvents) and extraction temperatures (30 to 60 °C) on oat lipids and phospholipid extraction are investigated using the Patricelli kinetic model and thermodynamic analysis. The mass-transfer coefficient (k₁) of the washing stage is approximately ten times higher than the diffusion stage under different solvents and temperature conditions. Compared with the subcritical propane and mixed solvents, the maximum equilibrium yield of oat lipids and phospholipids are obtained using subcritical DME. With increased extraction temperature from 30 to 60 °C, the equilibrium yield of phospholipids increases, whereas the equilibrium yield of lipids increases to 5.30% at 40 °C and then decreases. The enthalpy and entropy changes for phospholipid extraction are higher than those for lipid extraction. The Gibbs free energy for phospholipid extraction rapidly decreases with increased extraction temperature. A loose endosperm of oat grain is observed, and the concentration of lipids in the bran layer is higher than in the endosperm. In conclusion, kinetic and thermodynamic analyses statistically prove that DME is more effective than propane and mixes solvents for extracting lipids and phospholipids from oat flakes, and that phospholipid extraction strongly depends on temperature. Practical Application: The removal of lipids and phospholipids benefits oat-product processing and storage. However, traditional industrial n-hexane extraction usually requires a high-temperature process for solute–solvent separation, which may result in low quality of the meal. Subcritical-fluid extraction is a rising technology for lipid and phospholipid extraction. The yields of lipids and phospholipids using subcritical dimethyl ether (DME) is higher than those propane and its mixed solvents. The temperature dependence of phospholipid extraction is more active than that of lipid extraction. Thus, use of subcritical DME is a promising lipid-extraction technique to obtain solvent­free oat oil and high-quality defatted oat flour with potential application in the oat-processing industry.     

The nutritive value of refined rapeseed oils: A review

Recent findings on the nutritive value of rapeseed oil (RSO) with high erucic acid content have been compared to those of canbra oil (CO), an oil extracted from newly bred Canadian rapeseed with no erucic acid. Erucic acid in diets retards animal growth even if food consumption is not altered. Growth performances of CO are as good as olive or peanut oil. The unbalanced ratio of palmitic acid to monoethylenic acids of CO does not affect rat growth rate. Because of its glyceride structure and high content of erucic acid, RSO has a lower digestibility (81%) than CO (96%) in the rat. Unabsorbed erucic acid is not preferentially excreted as calcium soaps. Interesterification of RSO which converts 31.7% of the erucic chains to the 2 position improves digestibility of erucic acid. 2-Monoerucin is more efficiently absorbed than the free acid. In vivo metabolic conversion of erucic to oleic acid has been proved in the rat. β-oxidation of injected 14-¹⁴C labeled erucic acid proceeded at the same rate as oleic acid but the over-all yield of the reaction was lower. Fatty acid composition of tissues in animals fed RSO or CO is influenced on one hand by erucic and gadoleic (C_20∶1) acids of RSO, and on the other hand by the unbalanced ratio of palmitic-monoethylenic acids and the linolenic acid content of both oils. Nonnegligible amounts of erucic acid are deposited in the body fats of rats, chickens, turkeys, lambs and found in the milk of female rats fed RSO. Almost no erucic acid is incorporated in liver and testicles in the rat and it is not recovered in chicken egg yolk. The effect of RSO on rat reproduction has been re-examined. Dietary lipid and vitamin levels are of great importance in the results obtained. RSO induces myocarditis in several animal species. Similar lesions, although less frequent and severe, have been observed also with CO in the rat. Some authors have reported that erucic acid of RSO was responsible for the effect on heart muscle. Common fatty acid patterns to both RSO and CO have to be further investigated to explain the persisting effect of CO. One of 9 papers presented at the Symposium, “Cruciferous Oil-seeds,” ISF-AOCS World Congress, Chicago, September 1970.     

Genetics,characteristics, and utilization of oil in caryopses of oat species

For oats to be an economically feasible oilseed crop in Iowa, the oil percentage would have to be increased to ca. 16%. A survey of the oil percentage in 445 oat cultivars and collections gave a range of 2.0–11.0%. The oil percentage was only slightly affected by growing oats in 5 different locations in Iowa. Inheritance studies indicated that oil percentage was inherited polygenically, and there was a tendency for high oil percentage to be partially dominant. Analysis of 64 cultivars and collections showed a wide variation of fatty acid composition: palmitic, 14–23%; stearic, <1–4%; oleic, 29–53%; linoleic, 24–48%; linolenic, < 1–5%. The oil percentage was positively correlated with oleic acid and negatively correlated with linoleic and linolenic acids. Oats contained a lipase that made extraction of oil with low acid values difficult. The lipase was strongly affected by moisture and was most active in oat doughs containing 25–50% moisture. There was at least a 20-fold variation in lipase activity in oat cultivars and collections. Whole oats may be kept in dry storage for several years without significant lipolysis, but in broken or crushed caryopses, lipolysis occurs even at low moisture levels. The lipase may be inactivated by heat or 95% ethanol treatments.     

Recent developments and prospects in the extraction,composition, stability,food applications,and in vitro digestion of plant oil bodies

Oil bodies (OBs) are micron- or submicron-sized sub-organelles widely found in plants seeds and nuts. The structure of OBs is composed of a core of neutral lipids covered by a phospholipid-protein layer, which ensures the stability of OBs under extreme environmental conditions and further protects core lipids as energy reserves. As naturally pre-emulsified oil-in-water emulsions, OBs have been gradually applied to replace synthetically engineered oil droplets. In this paper, the recent research on the extraction, composition, stability, food applications, in vitro digestion, and future perspectives of plant OBs were reviewed. Recent studies have focused on the large-scale extraction techniques and OBs surface protein identification and function. Electrostatic deposition and viscosity effect of polysaccharides significantly improve the stability of OBs emulsions. OBs have broad application prospects in replacing milk fat droplets, as fat replacers and delivery vehicles, and fabricating emulsion-gels, oleogels or edible films. Notably, oleosins present a potential allergen risk. OBs are digested slowly, resulting in increased satiety and effectively helping to reduce calorie intake, but this can negatively affect the bioaccessibility of nutritional compounds in OBs. When OB as a delivery vehicle, its natural structure may be disrupted, whereas OBs-based delivery system facilitates the bioaccessibility of hydrophobic active compounds.     

A review of lecithin chemistry and glandless cottonseed as a potential commercial source

Industrial lecithin can be fractionated as phospholipids and glycolipids after neutral lipids and protein-containing contaminants are removed. The polar lipids are very reactive and are difficult to extract and purify from oilseeds. Their purity and special properties can be improved by a number of methods including solvent fractionation, hydrogenation, sulfonation, and ethoxylation. Studies are determining the role of the polar lipids of lecithin in (a) the synthesis of triglycerides in maturing seeds, (b) the structure of biological membranes, and (c) the molecular basis of the functionality of food ingredients. Lecithin, having both polar and nonpolar groups, has high surface activity and is reactive with both oil and protein, making it an excellent emulsifying agent in food systems; lecithin also slows autoxidation and enzyme hydrolysis of fats. Cottonseed lecithin is low in linolenic acid, prevents flavor deterioration of soybean oil and can be used to stabilize sunflower oil against color change during high temperature use. Gossypol binds to lecithin in oil from glanded cottonseed economically negating it as a commercial source of this product. New cultivars producing glandless, or gossypol-free cottonseed, may have potential as commercial sources of edible lecithin.     

Phytosterols in cereal by-products

Phytosterols are hypocholesterolemic. Like corn fiber oil, the lipid extracts of certain cereal by-products may be rich sources of these health-promoting compounds. The objective of this research was to examine the phytosterol content and composition of various cereal by-products. Total lipids in rice bran, wheat bran, wheat germ, durum wheat (bran and germ mixture), oat bran, oat hull, and corn fine fiber were extracted, and the sterol profiles of the extracted lipids were analyzed by GC. Rice bran contained the most lipids (22.2%), followed by wheat germ, durum wheat, oat bran, wheat bran, and oat hull; corn fine fiber contained the least amount of lipids (1.7%). Sitosterol, campesterol, and stigmasterol were the major phytosterols in these lipid extracts, whereas brassicasterol was detected only in wheat samples. Rice bran oil contained considerable amounts of cycloartenol and 24-methylenecycloartanol, which were unique to these samples. Total sterol concentrations in extracted lipids were similar for rice bran, wheat bran, wheat germ, and durum wheat (21.3–15.1 mg/g), but they were very low in oat bran lipids and oat hull lipids (3.4 and 8.2 mg/g, respectively). Corn fine fiber lipids contained the highest amount of sterols (48.3 mg/g). Rice bran appears to be the best source of phytosterols, with the highest oil content and high concentration of sterols.     

Thermal dehydrochlorination of PVC in the presence of rubber seed oil

Dehydrochlorination rates of PVC in nitrogen atmosphere were determined in the presence of rubber seed oil (RSO), epoxidized rubber seed oil (ERSO), barium soap of rubber seed oil fatty acids and barium soap of epoxidized fatty acid of rubber seed oil. The initial rates of dehydrochlorination and the time required for the degradation to attain 1% conversion showed that the rubber seed oil derivatives exert a stabilizing effect on the degradation of PVC. The order of the stabilizing effect was found to be metal soaps of ERSO < metal soaps of RSO < ERSO < RSO.     

The effect of dietary fatty acid balance on myocardial lesions in male rats

Three hundred (experiment I) and 350 (experiment II) weanling, 3-week-old male Sprague-Dawley rats weighing between 40–50 g were randomly assigned two per cage and 50 per dietary treatment to study the effect of dietary fatty acid balance on myocardial lesions. The following oils were tested: Experiment I.Brassica napus var. Tower rapeseed oil [Tower RSO, 1974 cultivar and 1975 cultivar, each containing 0.3% erucic (22∶1) acid];B. napus var. Zephyr RSO containing 0.9% 22∶1; corn oil; olive oil; and soybean oil. Experiment II.B. napus var. Tower RSO (1974 cultivar), olive oil, soybean oil, and the following oils to which was added the indicated level of free 22∶1; Tower +0.5% 22∶1; Tower +5.6% 22∶1; olive oil +4.4% 22∶1; soybean oil +5.7% 22∶1. In each case the oils were incorporated in a semisynthetic diet at a level of 20% by weight. Heart and heart lipid weights of rats fed the different oils did not differ statistically from each other. Fatty acid analyses of heart lipids revealed that the fatty acid composition of the cardiac lipids reflected that of the diet fed. In experiment I, there was a definite but significantly lower incidence (P<0.01) and severity (P<0.01) of heart lesions in rats fed control oils (corn, olive, soybean) than in rats fed rapeseed oils. Also, in experiment II, a definite but lower incidence and severity of heart lesions occurred in rats fed control oils (soybean, olive) compared to rats fed Tower RSO or this oil with added free 22∶1. Adding 22∶1 to an oil naturally high in 18∶3 (soybean) did not alter the incidence of heart lesions, whereas adding 22∶1 to an oil naturally high in 18∶1 (olive) increased significantly (P<0.01) both the incidence and severity of heart lesions. Thus, it appears that the background incidence of heart lesions that are found in the rat in any case, and which are increased by rapeseed oil feeding, is caused by the imbalanced fatty acid composition of the oil for the growing rat, i.e. high monoenes (18∶1, 20∶1, and 22∶1) and high 18∶3 and is not only due to the presence of excess 18∶3. Contribution No. 706, Animal Research Institute.     

Novel strategy for the demulsification of isolated sesame oil bodies by endogenous proteases

This study aimed to develop a novel method to demulsify the isolated sesame oil bodies (OB) to recover oil by directly using the endogenous proteases in the isolated OB. In this study, it was found that the isolated sesame OB contained OB intrinsic proteins as well as extrinsic proteins. The OB intrinsic proteins at least included one 41 kDa steroleosin, two 39 kDa steroleosins, two 27 kDa caleosins, four 27 kDa oil body-associated proteins, three 17 kDa oleosins, and four 15 kDa oleosins. As for the OB extrinsic proteins, the predominant ones were 11S globulins, followed by 2S albumins and 7S globulins. In addition, the OB extrinsic proteins contained sesame endogenous proteases, predominantly including aspartic endopeptidases, subtilisin-like proteases, serine carboxypeptidases, and metalloendopeptidase. The results revealed that the combined activity of these endogenous proteases was optimal at pH 4–5 and 50–60°C. The oleosins were the most easily hydrolyzed by these proteases, followed by 11S and 7S globulins, and the 2S albumins had strong resistance to these proteases. By incubation at pH 5 and 60°C for 2 h, approximately 97% of total lipids in isolated sesame OB (78% of total lipids in sesame seeds) could be recovered as oil by centrifugation, whereas no oil could be obtained when the incubation time was 0 h. These results indicated that the endogenous protease-induced degradation of oleosins was the key point for the efficient demulsification of isolated sesame OB.     

燕麦产品的红外分析与鉴定

采用傅立叶变换红外光谱法(FTIR)获得了6种燕麦的红外光谱及其二阶导数谱图.燕麦中的脂肪(1 747 cm-1、2 855 cm-1、2 927 cm-1)、蛋白质(1 658 cm-1、1 540 cm-1)和糖(1 200～900 cm-1)等主要营养成分具有明显的红外特征峰.不同厂家同一配方的燕麦谱图差异较小,但其二阶导数谱图具有明显的指纹特征,该方法可简便、快速地鉴别燕麦.     

The role of gastric lipolysis on fat absorption and bile acid metabolism in the rat

In vivo studies were carried out in young Sprague-Dawley rats to examine the role of gastric lipolysis on fat absorption and bile acid metabolism. When fed by gastric perfusion 5 times (corn oil, 4 g/day) their usual dietary intake of fat, rats deprived of lingual lipase by the creation of an esophageal fistula had a significant degree of fat and bile acid malabsorption as well as a shortened bile acid halflife when compared to animals with a gastrostomy. The % fat absorption, bile acid loss and bile acid pool were normal in 2 groups of esophageal fistula rats fed the same quantity of corn oil or twice (8 g/day) that amount as a fine emulsion. In view of a negligible gastric lipase activity in animals with an esophageal fistula and of decreased hydrolysis of a triglyceride test meal, these data suggest that gastric lipolysis is of physiological importance in situations where lipolytic mechanisms are stressed by a large fat intake. Its principal role is to potentiate intestinal lipolysis by facilitating the emulsification of dietary lipids through its formed products and, therefore, the contact of pancreatic lipase with its substrates.     

Improving the Frying Performance and Oxidative Stability of Refined Soybean Oil by Tocotrienol‐Rich Unsaponifiable Matters of Kolkhoung (Pistacia khinjuk) Hull Oil

Increasing consumer awareness for all natural products has quickly led to growing research on new resources of potent and profitable natural antioxidants. In this context, for the first time, the Kolkhoung hull oil (KHO) (Pistacia khinjuk)‐unsaponifiable matters (USM) (UHO) (100, 200, and 400 mg kg^?1) were incorporated into refined soybean oil (RSO) and the oxidative stability of prepared oils was measured during 32 hours of frying. Then, the obtained results (oxidative stability) were compared to the samples containing tert‐butyl hydroquinone (TBHQ) (100 mg kg^?1) as a common synthetic antioxidant. According to the results of oxidative stability assays of acid values, conjugated diene values and carbonyl values, and total polar compounds, the incorporation of UHO, particularly at a concentration of 200 mg kg^?1, was more efficient in improving the oxidative stability compared to TBHQ. The tocol content of KHO (2043.4 mg kg^?1) was higher than the reported amounts of other conventional edible oils. Furthermore, by incorporation of UHO into RSO, as compared with TBHQ, a better protection of naturally occurring antioxidants (tocopherols and sterols) was found after adding UHO to RSO. This fact was mainly attributed to the UHO's tocotrienol fraction. Hence, the USM of KHO can be used as a potent antioxidant to improve the oxidative stability of frying oils.     

Physicochemical Properties and Stabilities of Crude and Purified Oil Bodies Extracted from High Oleic Peanuts

Physicochemical properties and emulsion stabilities of two types of oil bodies—crude oil bodies (COB) and purified oil bodies (OB)—recovered from high oleic peanuts via an aqueous enzymatic extraction process are investigated. RGB color analysis and flavor volatiles identification reveal that both COB and OB present desirable color and acceptable flavor. OB tends to have stronger antioxidant capacity and higher nutritional value compared to COB according to results from fatty acids, amino acids, and tocopherol analyses. The emulsification of oil bodies shows a slightly lower level than lecithin, but excellent thermal stability and storage stability (especially for OB), which relates greatly to small particle size, high zeta‐potential, and high content of hydrophobic amino acids. The freeze–thaw stability of OB is poorer than that of COB, which may relate to the presence of impurities in oil bodies. Thus, the peanut oil bodies, especially purified oil bodies, are proven to be advantageous emulsifying agents and additional valuable sources of antioxidants. Practical Applications: The results in this work clarify the differences in physiochemical composition and the fundamental emulsifying properties between COB and OB, and demonstrate the possibility of replacing traditional emulsifiers by natural green emulsifiers (e.g., oil bodies) in the food industry. Moreover, oil bodies extracted from high oleic peanuts, which contain plenty of unsaturated fatty acids and tocopherols, are a potential source for food supplements. In the long term, this work will increase the industrial conversion rate of oil bodies, enhance the processing and utilization level of high oleic peanuts, and promote the development of new foods based on peanut resources.