Minor components in food oils: a critical review of their roles on lipid oxidation chemistry in bulk oils and emulsions

Food oils are primarily composed of triacylglycerols (TAG), but they may also contain a variety of other minor constituents that influence their physical and chemical properties, including diacylglycerols (DAG), monoacylglycerols (MAG), free fatty acids (FFA), phospholipids (PLs), water, and minerals. This article reviews recent research on the impact of these minor components on lipid oxidation in bulk oils and oil-in-water emulsions. In particular, it highlights the origin of these minor components, the influence of oil refining on the type and concentration of minor components present, and potential physicochemical mechanisms by which these minor components impact lipid oxidation in bulk oils and emulsions. This knowledge is crucial for designing food, pharmaceutical, personal care, and other products with improved stability to lipid oxidation.     

Distribution of fatty acids in triacylglycerols and phospholipids from peas (Pisum sativum L.)

BACKGROUND: The fatty acid distribution of triacylglycerols (TAG) and major phospholipids (PL) obtained from four varieties of peas (Pisum sativum) was investigated. The total lipids extracted from the peas were separated by thin layer chromatography into seven fractions. RESULTS: The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while hydrocarbons, steryl esters, free fatty acids and diacylglycerols (sn‐1,3 and sn‐1,2) were also present in minor proportions (5.6–9.2%). The main PL components isolated from the four varieties were phosphatidylcholine (42.3–49.2%), phosphatidylinositol (23.3–25.2%) and phosphatidylethanolamine (17.7–20.5%). Significant differences (P < 0.05) in fatty acid distribution were found for different pea varieties. Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. However, the principal characteristics of the fatty acid distribution in the TAG and three PL were evident among the four varieties: unsaturated fatty acids were predominantly located in the sn‐2 position while saturated fatty acids primarily occupied the sn‐1 or sn‐3 position in the oils of the peas. CONCLUSION: These results should be useful to both producers and consumers for the manufacture of pea foods in Japan. Copyright © 2007 Society of Chemical Industry     

Roasting effects on fatty acid distribution of triacylglycerols and phospholipids in the kernels of pumpkin (Cucurbita spp) seeds

In this study, changes in fatty acid distributions of pumpkin seeds (Cucurbita spp) in the course of the roasting process were investigated. Whole pumpkin seeds were exposed to microwaves for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The kernels were separated from the seeds, and the lipid components and the fatty acid distributions of triacylglycerols (TAGs) and phospholipids (PLs) were analysed by a combination of thin layer chromatography and gas chromatography. Major lipid components were TAGs, free fatty acids (FFAs) and PLs, while steryl esters and diacylglycerols were also present in minor proportions. The greatest PL losses (p < 0.05) were observed in phosphatidyl ethanolamine, followed by phosphatidyl choline or phosphatidyl inositol. With a few exceptions, significant differences (p < 0.05) in fatty acid distributions occurred when the seeds were microwaved for 20 min or more. Nevertheless, the positional characteristics of fatty acid distributions in the TAGs were still retained after 20 min of roasting: unsaturated fatty acids were predominantly concentrated in the sn‐2‐position, and saturated fatty acids primarly occupied the sn‐1‐ or sn‐3‐position. These results suggest that no significant changes in fatty acid distribution of TAGs and PLs would occur within 12 min of microwave roasting, thus ensuring that a good‐quality product would be obtained. Copyright © 2005 Society of Chemical Industry     

Roasting effects on fatty acid distributions of triacylglycerols and phospholipids in sesame (Sesamum indicum) seeds

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. The positional distribution of fatty acids in triacylglycerols (TAGs) and phosphatidylcholine (PC) isolated from total lipids in these seeds was investigated as well as the naturally occurring antioxidants that are present. Major lipid components were TAGs and phospholipids (PLs), while steryl esters (SEs), free fatty acids (FFAs) and sn‐1,3‐ and sn‐1,2‐diacylglycerols (DAGs) were minor ones. Following roasting, a significant increase (P < 0.05) was observed in FFAs and in both forms of DAG (primarily sn‐1,3‐DAG). The greatest PL losses (P < 0.05) were observed in phosphatidylethanolamine (PE), followed by PC and phosphatidylinositol (PI). On the other hand, the amounts of γ‐tocopherol and sesamin remained at over 80 and 90% respectively of the original levels after roasting at 220 °C. The principal characteristics of the positional distribution of fatty acids were still retained after 25 min of roasting: unsaturated fatty acids, especially linoleic and/or oleic, were predominantly concentrated in the sn‐2‐position, and saturated fatty acids, especially stearic and/or palmitic, primarily occupied the sn‐1‐ or sn‐3‐position. The results suggest that unsaturated fatty acids located in the sn‐2‐position are significantly protected from oxidation during roasting at elevated temperatures. © 2001 Society of Chemical Industry     

LIPID CLASSES, FATTY ACID COMPOSITIONS AND TRIACYLGLYCEROL MOLECULAR SPECIES FROM ADZUKI BEANS (VIGNA ANGULARIS)

The lipids extracted from adzuki beans grown in Japan were classified by thin-layer chromatography (TLC) into eight fractions. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from the total lipids in the beans were determined from a combination of argentation-TLC and gas chromatography. The major lipid components were phospholipids (PL; 63.5%) and TAG (21.2%), while hydrocarbons (5.1%), steryl esters (7.5%), free fatty acids (0.9%), diacylglycerols (1.3%) and monoacylglycerols (0.5%) were also present in minor proportions. Both major samples had high amounts of total unsaturated fatty acids, representing 62.1% for TAG and 65.9% for PL. Seventeen different molecular species were detected. The major TAG components were SMD (5.0%), S₂T (19.3%), SD₂ (13.8%), SMT (9.3%), MD₂ (4.5%), SDT (7.0%), D₃ (8.8%) and ST₂ (15.9%), where S, M, D and T denote a saturated fatty acid, a monoene, a diene and a triene, respectively.

PRACTICAL APPLICATIONS

This article describes the characteristics of lipid components, fatty acid compositions as well as the profiles of triacylglycerol (TAG) molecular species of adzuki beans. α-Linolenic (18:3 n -3) acid was detected as 24.8, 21.2 and 15.2% in the TAG, total lipids and phospholipids, respectively. The oil from legumes, except the profitable fatty acid content, could be a potential source of tocopherols. The data obtained in this study would be useful to both consumers and producers for manufacturing traditional adzuki confectionaries ( wagashi ) in Japan and elsewhere.     

Influence of Processing and Storage Time on the Lipidic Fraction of Taralli

ABSTRACT:  An experimental investigation was carried out to evaluate the influence of processing and storage time on the lipidic fraction of  taralli . The data obtained pointed out that the kneading phase caused a significant increase of the oxidized triacylglycerols and triacylglycerol oligopolymers, primary and secondary oxidation compounds, respectively, accompanied by a significant decrease of the content of polyunsaturated fatty acids. The successive baking step caused the degradation of a part of the oxidized compounds to volatile substances, as confirmed by the  p -Anisidine values, whereas the storage time determined a further significant increase of the level of oxidized triacylglycerols. Finally, the level of diacylglycerols, monoacylglycerols, and free fatty acids, indicative of hydrolytic degradation, did not show significant changes. The principal component analysis allowed one to clearly distinguish among samples obtained through processing conditions.     

Fatty acid distribution in triacylglycerols and phospholipids of broad beans (Vicia faba)

Fatty acid distribution of triacylglycerols (TAG) and phospholipids (PL) obtained from the four cultivars of broad beans (Vicia faba) was investigated. Total lipids extracted from the beans were separated by thin-layer chromatography into eight fractions. The major lipid components were TAG (47.7–50.1%) and PL (47.5–50.5%), while hydrocarbons, steryl esters, free fatty acids, diacylglycerols (1,3-DAG and 1,2-DAG) and monoacylglycerols were present in minor proportions (1.8–2.4%). The major PL components were phosphatidylcholine (56.4–58.4%), phosphatidylethanolamine (20.3–21.7%) and phosphatidylinositol (16.6–18.6%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. No significant differences (P > 0.05) in fatty acid distribution existed when the different cultivars were compared. The fatty acid distributions in the TAG were evident among the four cultivars: unsaturated fatty acids were predominantly concentrated in the sn−2 position, and saturated fatty acids primarily occupied the sn−1 or sn−3 position in the oils. These results could be useful to both consumers and producers for manufacture of traditional foods in Japan and elsewhere.     

A Research Note Lipid Composition of Cumin (Cuminum cyminum L.) Seeds

Total lipids extracted from Cumin (Cuminum cyminum L., Umbelliferae) amounted to 14.5% of the dry seeds. The total lipids consisted of 84.8% neutral lipids, 10.1% glycolipids, and 5.1% phospholipids. Neutral lipids consisted mostly of triacylglycerols (89.4%) and small amounts of diacylglycerols, free fatty acids, sterols, sterolesters, and hydrocarbons. At least five glycolipids and five phospholipids were identified. Acylmonogalactosyldiacylglycerol and acylatedsterylglucoside were the major glycolipids, while monogalactosyldiacylglycerol, monogalactosylmonoaclycerol, and digalactosyldiacylglycerol were present in small quantities. Phosphatidylethanolamine and phosphatidylcholine were the major phospholipids, while phosphatidylinositol, lysophosphatidylethanolamine, and phosphatidylglycerol were present in small amounts. The fatty acid composition of these different neutral lipids, glycolipids, and phospholipids was determined     

Natural lecithins and phosphorylated acylglycerols as inhibitors of autoxidation of fats and oils

Both natural phospholipids (soybean or rapeseed lecithin) and phosphorylated acylglycerols (produced by treatment of diacylglycerols with phosphorus pentoxide or metaphosphoric acid) inhibit the oxidation of polyunsaturated fatty acid esters in rapeseed, sunflower seed or soybean oils, but only higher phospholipid additions (more than 0.2%) have pronounced effect on the stability under storage conditions. Partially hydrogenated oils are stabilized similarly as original liquid oils. The inhibitory activity of synthetic phospholipids is particularly high in presence of trace metal compounds, such as copper, iron or manganese. The chelating activity is nearly the same in the case of phosphatidic acids, their ammonium salts, phosphatidylcholine or phosphatidylethanolamine. The hydroperoxide decomposing activity is, however, much higher in nitrogen-containing phospholipids than in the corresponding phosphatidic acids. The content of oxidized fatty acids is lower in phospholipids than in triacylglycerols.     

Lipolysis in muscles during refrigerated storage as related to the metabolic type of the fibres in the rabbit

The relation between lipolysis and the metabolic fibre type was investigated during refrigerated storage of rabbit muscles. Free fatty acid, monoacylglycerol and diacylglycerol contents and free fatty acid composition were compared in five muscles immediately after slaughter and after a 7-day-storage at 4°C. The results showed that. (1) The amount of free fatty acids sharply increased during the refrigerated storage (from 2-10 to 11-32 mg/100 g of muscle), especially that of long chain polyunsaturated fatty acids (from less than 0.1 to 1.4-3.3 mg/100 g of muscle). (2) The glycolytic muscles contained 1.5 times less free fatty acids than the oxidative ones. However, the rates of phospholipid and triacylglycerol hydrolysis were not related to the metabolic type of the fibres. (3) The contribution of phospholipids to free fatty acid fraction was twice that of triacylglycerols in the glycolytic muscles whereas it was similar or lower to that of triacylglycerols in the oxidative muscles.     

The relation of lipid peroxidation processes with atherogenesis: a new theory on atherogenesis

The extremely high sensitivity of polyunsaturated fatty acids (PUFAs) to oxygen is apparently used by nature to induce stepwise appropriate cell responses. It is hypothesized that any alteration in the cell membrane structure induces influx of Ca2+ ions. Ca2+ ions are required to activate degrading enzymes, such as phospholipases and lipoxygenases (LOX) that transform PUFAs bound to membrane phospholipids to lipidhydroperoxides (LOOHs). Enzymatic reduction products of LOOHs seem to serve as ligands of proteins, which induce gene activation to initiate a physiological response. Increasing external impact on cells is connected with deactivation of LOX, liberation of the iron ion in its active center followed by cleavage of LOOH molecules to LO * radicals. LO * radicals induce a second set of responses leading to generation of unsaturated aldehydic phospholipids and unsaturated epoxyhydroxy acids that contribute to induction of apoptosis. Finally peroxyl radicals are generated by attack of LO * radicals on phospholipids. The latter attack nearly all types of cell constituents: Amino- and hydroxyl groups are oxidized to carbonyl functions, sugars and proteins are cleaved, molecules containing double bonds such as unsaturated fatty acids or cholesterol suffer epoxidation. LOOH molecules and iron ions at the cell wall of an injured cell are in tight contact with phospholipids of neighboring cells and transfer to these reactive radicals. Thus, the damaging processes proceed and cause finally necrosis except the chain reaction is stopped by scavengers, such as glutathione. Consequently, PUFAs incorporated into phospholipids of the cell wall are apparently equally important for the fate of a single organism as the DNA in the nucleus for conservation of the species. This review intends to demonstrate the connection of cell alteration reactions with induction of lipid peroxidation (LPO) processes and their relation to inflammatory diseases, especially atherosclerosis and a possible involvement of food. Previously it was deduced that food rich in cholesterol and saturated fatty acids is atherogenic, while food rich in n-3 PUFAs was recognized to be protective against vascular diseases. These deductions are in contradiction to the fact that saturated fatty acids withstand oxidation while n-3 PUFAs are subjected to LPO like all other PUFAs. Considering the influence of minor food constituents a new theory about atherogenesis and the influence of n-3 PUFAs is represented that might resolve the contradictory results of feeding experiments and chemical experiences. Cholesterol-PUFA esters are minor constituents of mammalian derived food, but main components of low density lipoprotein (LDL). The PUFA part of these esters occasionally suffers oxidation by heating or storage of mammalian derived food. There are indications that these oxidized cholesterol esters are directly incorporated into lipoproteins and transferred via the LDL into endothelial cells where they induce damage and start the sequence of events outlined above. The deduction that consumption of n-3 PUFAs protects against vascular diseases is based on the observation that people living on a fish diet have a low incidence to be affected by vascular diseases. Fish are rich in n-3 PUFAs; thus, it was deduced that the protective properties of a fish diet are due to n-3 PUFAs. Fish, fish oils, and vegetables contain besides n-3 PUFAs as minor constituents furan fatty acids (F-acids). These are radical scavengers and are incorporated after consumption of these nutrients into human phospholipids, leading to the assumption that not n-3 PUFAs, but F-acids are responsible for the beneficial efficiency of a fish diet.     

老腊肉加工过程中脂质水解及氧化的变化研究

以重庆城口改进型老腊肉为研究对象,分别提取腌制前、腌制后、电热烘烤、烟熏5 d、10 d、15 d共6个阶段的试样,通过测定酸价、过氧化值、TBA、脂肪酶活力及脂肪酸组成等指标,分析其在加工过程中脂质水解及氧化的变化。结果表明:酸价在腌制后显著上升,在其他工艺阶段变化缓慢,TBA和过氧化值均在电热烘烤后显著上升,但过氧化值在烟熏阶段呈下降趋势而TBA变化不显著;脂肪水解酶的活力在腌制后显著上升,经电热烘烤阶段后不断下降;受脂肪酶水解酶活性的影响,磷脂和游离脂肪酸的组成成分在烟熏前期变化显著,其中磷脂和游离脂肪酸的含量及两者脂肪酸组成的变化尤其是多不饱和脂肪酸的变化趋势相反,而甘油酯的含量及其脂肪酸组成的相对含量保持稳定,说明磷脂在腊肉加工过程中水解作用显著,游离脂肪酸主要来源于磷脂的水解。     

Changes in lipid composition,fatty acid profile and lipid oxidative stability during Cantonese sausage processing

Lipid composition, fatty acid profile and lipid oxidative stability were evaluated during Cantonese sausage processing. Free fatty acids increased with concomitant decrease of phospholipids. Total content of free fatty acids at 72 h in muscle and adipose tissue was 7.341 mg/g and 3.067 mg/g, respectively. Total amount of saturated, monounsaturated and polyunsaturated fatty acids (SFA, MUFA, and PUFA) in neutral lipid exhibited a little change during processing, while the proportion of PUFA significantly decreased in the PL fraction. The main triacylglycerols were POO + SLO + OOO, PSO (P = palmitic acid, O = oleic acid, L = linoleic acid, S = stearic acid), and a preferential hydrolysis of palmitic, oleic and linoleic acid was observed. Phosphatidylcholines (PC) and phosphatidylethanolamines (PE) were the main components of phospholipids and PE exhibited the most significant degradation during processing. Thiobarbituric acid values (TBARS) increased while peroxide values and hexanal contents varied during processing.     

甘二酯制备的研究进展

甘二酯因其独特的代谢途径而具有多种生理功能,它在天然油料中含量较少,所以利用甘三酯制备生产甘二酯尤显重要。概述了甘二酯制备的国内外研究现状,介绍并比较了甘油脂肪酸酯化和油脂甘油解制备甘二酯的两种方法,展望了甘二酯的发展前景。     

Selective Increase in Conjugated Linoleic Acid in Milk Fat by Crystallization

The objective of this work was to obtain concentrated natural conjugated linoleic acid (CLA) from milk fat by urea complexation. Milk fat was hydrolyzed to provide free fatty acids, followed by crystallization with different ratios of urea. The profiles of fatty acids achieved by urea complexation showed different fatty acid compositions. Long-chain unsaturated fatty acids, including CLA, were concentrated after crystallization. The highest amount of CLA was achieved by the first crystallization with a 2:1 urea/fatty acid ratio. CLA was elevated 2.5-fold. The C18:1/C18:0 fatty acid ratio was increased from 2 to 51, and stearic acid (C18:0) was decreased 17-fold.     

SOME ASPECTS OF THE STRUCTURE AND FUNCTION OF THE YEAST PLASMA MEMBRANE

The permeation of many compounds into the yeast cell is largely regulated by the plasma membrane according to their lipid solubility and degree of dissociation. Thus the permeation rate of the fatty acids and α-keto acids is proportional to their relative lipid solubility. The highly dissociated and poorly lipid-soluble di- and tri-carboxylic acids and halogenated acetic acids permeate only very slowly; the impermeable α-ketoglutaric acid becomes easily permeable when made lipid-soluble by esterification. The lipid composition of the plasma membrane can thus be of decisive importance in regulating the movement of different compounds into and out of the yeast cell. Lipid analyses revealed that anaerobiosis clearly affected the neutral lipid composition of the plasma membrane. The aerobic membrane contained more unsaturated fatty acids, mainly palmitoleic and oleic acids, more total sterol, much more ergosterol and much less squalene. The principal sterol in the aerobic membrane, ergosterol, was mainly in the free form, whereas zymosterol and other minor sterols were predominantly esterified. In contrast, the anaerobic membrane contained small amounts of biosynthetic sterol precursors of ergosterol, and was clearly richer in saturated fatty acids having a greater variation in chain length. Both plasma membranes contained a considerable amount of triacylglycerols.     

制取高不饱和脂肪酸大豆油脂方法的研究

利用结晶、温度回调结晶,将大豆油脂分成富含不饱和脂肪酸的油脂与低不饱和脂肪酸的油脂。通过单因素实验与正交实验,对影响分离效果的主要因素进行了研究,最佳工艺参数为:降温速度5℃.h-1,结晶温度-15℃,结晶时间24h,搅拌速度15r/min。利用温度回调至-5℃的方法,使富含不饱和脂肪酸的油脂产品碘值达到150.2gI2/100g。     

Lipid Composition and Hydration Characteristics of Lung Protein Isolates Defatted by Several Solvents

Different portions of a protein isolate from bovine lungs were exhaustively defatted by solvents of varying polarities. Phospholipids, cholesterol and cholesterol esters, free fatty acids, mono-, di- and triacylglycerols were quantitatively determined in the extracts. Their amount was dependant on the polarity of the solvent employed. Neutral lipids were quantitatively removed by all solvents whereas the amount of phospholipids extracted increased with solvent polarity. The water monolayer capacity of the defatted protein (obtained by the BET equation) showed an increase up to the maximum with the increase of the residual lipid content (determined by Folch wash). The results indicated that more protein polar sites were exposed when the lipid fraction (mainly phospholipids) was present.     

THE INFLUENCE OF LIPIDS DERIVED FROM MALT SPENT GRAINS ON YEAST METABOLISM AND FERMENTATION

The addition to wort of lipids derived from malt spent grains had a pronounced effect on yeast metabolism. The lipids allowed the fermentation of de-oxygenated wort and also stimulated yeast growth and the corresponding rate and extent of fermentation of air-saturated wort by yeast strains having a high oxygen requirement. The lipids increased the fusel alcohols content of beer and decreased the content of esters and medium chain-length fatty acids. The yeast incorporated sitosterol and unsaturated fatty acids from the spent grain lipids and the unsaturated fatty acids changed the pattern of fatty acids and sterols synthesized by the yeast. The fatty acids were present in the spent grain lipids mainly as triglycerides, free fatty acids and phospholipids. Using pure lipid compounds it was shown that the triglycerides were inactive and that the spent grain lipids exerted their effect on fermentation through the synergistic action of free unsaturated fatty acids, sitosterol and phospholipid. Phospholipid could be replaced by the detergent, Triton X-100. The effect of the lipids on the synthesis of esters, fusel alcohols and medium chain fatty acids could be explained solely by their content of unsaturated fatty acids.     

The Effect of Minor Components on Milk Fat Microstructure and Mechanical Properties

ABSTRACT: Although minor polar components affected the kinetics of milk fat crystallization, its structure and mechanical properties remained unchanged. At 5 °C, a granular microstructure was observed, while at 20 °C, a combination of granular and spherulitic microstructures were observed. By 27.5 °C, only spherulites were present after 24 h. There were no differences observed in the fractal dimension (D) determined by microscopy or rheology for anhydrous milk fat, milk fat triacylglycerols and MF‐TAGs with added diacylglycerols at 5 °C. There was, however, a strong temperature effect on D, increasing from 1.87 at 5 °C to 1.98 at 22.5 °C. The yield force and storage modulus were unaffected by removal of minor components.