Changes in the carotenoids and sterol fractions during the prolonged storage of wheat flour

Changes in the carotenoid and sterol fractions of three wheat flours have been studied during storage. Total carotenoid decreased throughout the storage period; the relative rates of loss in each flour were the same as the relative rates of oxidation of polyenoic acids previously found to occur in these flours. Hexane-extractable total sterol content remained unchanged during storage. Esterification of free sterol was demonstrated and esterification of free lutein was also indicated.     

Über die Extraktstoffe des Stammaterials der Kletterpalme Korthalsia rigida Blume

The extractives from the stems ofKorthalsia rigida Blume were isolated by successive extractions with solvents of increasing polarity. The lipophilic extractives mainly consist of free fatty acids, glycerides and sterol esters besides of free sterols. Principal components of the acids (free and esterified) are palmitic, linolenic, and linolic acid. Furthermore, very small amounts of dehydroabietic acid and three other diterpene acids have been identified as free acids. In the mixture of the free acids from the ether extract a fairly high amount of p-hydroxy benzoic acid is present. The bulk of the extraneous components is present in the polar extract fractions which contain besides of simple sugars mainly condensed tannins and related natural pholobaphenes.     

Lipid Composition of Field Pea (Pisum sativum cv Trapper) Seed and Starch

The total lipids in field pea seeds and refined starch were extracted by five aqueous/organic solvent systems and the greatest yield of total. neutral and polar lipids was obtained with hot n-propanol-water (3:1 v/v). Lipids extracted from field pea seeds represented 2.9% of the seed weight and consisted of 43.2% neutral lipids, 3.2% glycolipids and 53.6% phospholipids. The major components of the three fractions were 70% triacylglycerol in neutral lipid, 28% esterified sterol glycoside in glycolipid and 55% phosphatidylcholine in phospholipid. The purified starch fraction contained 0.22% surface lipids and 0.09% internal lipids. The surface lipids were primarily sterol esters and free fatty acids while only free fatty acids were found in the internal lipids. The ability of lysophospholipids and fatty acids to complex with field pea starch was demonstrated by differential scanning calorimetry and X-ray diffraction, respectively.     

Lipid content and fatty acid composition of green algae Scenedesmus obliquus grown in a constant cell density apparatus

The lipids of alga Scenedesmus obliquus grown under controlled conditions were separated and fractionated by column and thin-layer chromatography, and fatty acid composition of each lipid component was studied by gas-liquid chromatography (GLC). Total lipids were 11.17%, and neutral lipid, glycolipid and phospholipid fractions were 7.24%, 2.45% and 1.48% on a dry weight basis, respectively. The major neutral lipids were diglycerides, triglycerides, free sterols, hydrocarbons and sterol esters. The glycolipids were: monogalactosyl diglyceride, digalactosyl diglyceride, esterified sterol glycoside, and sterol glycoside. The phospholipids included: phosphatidyl choline, phosphatidyl glycerol and phosphatidyl ethanolamine. Fourteen fatty acids were identified in the four lipid fractions by GLC. The main fatty acids were C18:2, C16:0, C18:3(alpha), C18:1, C16:3, C16:1, and C16:4. Total unsaturated fatty acid and essential fatty acid compositions of the total algal lipids were 80% and 38%, respectively.     

Study on the Chemical Nature of Sterols contained in Bulgarian Sunflower Oil

The free sterols, the sterol esters and the sterol glycosides of the crude sunflower oil as well as those of the technical lecithin, the pitch and the deodorizer distillate of the latter oil were isolated by preparative TLC. The nature of sterols contained in the isolated sterol derivatives was elucidated by GLC and combined GLC-MS. Major sterols of all examined sterol fractions are sitosterol, campesterol and stigmasterol, the amount of sitosterol being prevalent. Unknown sterol with a molecular weight of 4²⁸ is present in sterols of the crude oil and the deodorizer distillate. Sterols of the deodorizer distillate contain an unknown sterol with a molecular weight of 430. Stigmasterol is present in the sterol fraction of the deodorizer distillate in high amounts. It was established that Δ⁷-sterols of the crude oil occur only in esterified form. The hydrolysis of the sterol derivatives in acid medium leads to dehydration products known as steroid dienes and disteroid ethers. Hydrolysis without dehydration was achieved by enzyme preparations. Some sterols of the crude oil were esterified with the same higher fatty acids contained in the glycerides of the sunflower oil.     

Chemical constituents of some mushrooms

The free amino acids, fatty acids and sterol contents of five Basidiomycetes were determined. The most abundant free amino acids were alanine, proline, serine and valine. The mushrooms examined also contained high levels of linoleic and palmitic acid. The most abundant sterol was ergosterol accompanied by its closely related sterols.     

Sterol composition of Bulgarian soya and corn oils

The free sterols, the sterol esters and the sterol glycosides of the raw soya and corn oils as well as those of the technical lecithin and the deodorizer distillated of the latter oils were isolated by preparative TLC. The composition of each of the isolated sterol derivatives was determined by GLC and MS. Sitosterol, campesterol, stigmasterol and an unknown sterol with a molecular weight of 428 are contained in almost all of the examined fractions of the soya oil and its refinement byproducts. Dehydrocampesterol is present in the free sterols of the raw soya oil and the soya lecithin. Stigmasterol is contained in the soya deodorizer distillate in high amounts. It was established that cholesterol was present in the sterol esters of the raw soya oil high amounts. Delta7-stigmastenol occurs only in the sterol esters of the latter oil. Sitosterol, campesterol and stimgasterol are the main components of all sterol fractions of the corn oil and its refinement products. Dehydrocampesterol and unknown sterols with molecular weights of 428 are present in the free sterols of the raw corn oil. Some sterol glycosides of the soya and corn lecithin are esterified with the same major fatty acid components of the glycerides, palmitic acid being the main one. The fatty acid compositon of sterol esters of the raw soya and corn oil roughly corresponds to the fatty acid composition of oils.     

Lipid composition of the liver oil of the ray, Himantura bleekeri

If rays are traditionally fished for their caudal fins, the rest of the body is wasted, except part of the skin that can be transformed into leather. Liver oil of the ray, Himantura bleekeri, was characterized in terms of lipid class composition and fatty acid profile. Liver oil content was high and represented 54% of the liver weight (w/w). Neutral lipids were predominant (92%), major components being triacylglycerols (63%). Other neutral lipids identified were hydrocarbons, sterol esters, mono- and di-acylglycerols, free fatty acids, sterols and glyceryl ethers. Polyunsaturated fatty acids of the n−3 series, namely eicosapentaenoic and docosahexaenoic acids, were high (4% and 16%, respectively). Cholesterol was the major component in the sterol fractions (free or esterified). Hydrocarbons were up to 30 carbons and squalene was present at the level of 22%. Thus, this liver oil proved to be an adequate source of n−3 fatty acids and other valuable lipidic compounds.     

Supercritical fluid extraction and characterization of lipids from algae Scenedesmus obliquus

Supercritical carbon dioxide (SC-CO2) extractions (with and without ethanol as an entrainer) were carried out to remove lipids and pigments from protein concentrate of green algae (Scenedesmus obliquus) cultivated under controlled conditions. The content and fatty acid composition of algal lipids using column, thin-layer (TLC) and gas-liquid chromatography (GLC) were determined. Absorption spectra of extracted fractions showed the predominance of chlorophyll A (lambda max at 410 nm). Single step supercritical carbon dioxide (SC-CO2) extraction resulted mostly in removal of neutral lipids and a part of glycolipids, but phospholipids were not extracted. Addition of ethanol to SC-CO2 increased the amount of glycolipids and phospholipids in the extract. TLC pattern of algal lipids showed that the main part of neutral lipids consisted of diglycerides, triglycerides, hydrocarbons, free sterols, and sterol esters. The glycolipids were mostly monogalactosyl diglyceride, digalactosyl diglyceride, esterified sterol glycoside, and sterol glycoside. In phospholipids, phosphatidyl choline, phosphatidyl glycerol, and phosphatidyl ethanolamine were the main compounds. Fatty acid composition patterns indicated the main fatty acids to be 16:0, 16:1, 16:2, 16:3, 16:4, 18:1, 18:2, and 18:3(a). Relatively high recovery of polyunsaturated fatty acids and essential fatty acids in supercritical fluid extracted algal lipids and proteins isolates were observed.     

EFFECT OF POSTMORTEM AGING ON CHICKEN MUSCLE LIPIDS

Neutral lipids of fresh chicken breast muscles are shown to be triglycerides, sterols and sterol esters with only traces of mono- and diglycerides and free fatty acids. Phospholipids include measurable quantities of phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl serine, sphingomyelin, diphosphatidyl glycerol, lysophosphatidyl choline and lysophosphatidyl ethanolamine. Fatty acid analyses of several of the lipid fractions are also included. Decreases in phosphatidyl choline and phosphatidyl ethanolamine coupled with increases in lysophosphatidyl choline, lysophosphatidyl ethanolamine and free fatty acids after 48 hr postmortem in the cold indicate phospholipase A activity concurrent with other postmortem changes. The significance of the results is discussed.     

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

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.     

Chemical constituents of some basidiomycetes

The sterol, fatty acid and free amino acid (FAA) contents of some Basidiomycetes were determined. The overall sterol distribution was similar to that of other mushrooms, with ergosterol as the predominant sterol accompanied by the other closely related sterols. The mushrooms examined also contained high levels of fatty acids of which linoleic is the most prominent. Glutamic acid, valine and proline were the dominant FAA.     

Effect of moisture on the lipid content and composition of two strains of Tenebrio molitor L. (Coleoptera, Tenebrionidae)

Tenebrio molitor larvae reared on dry wheat shorts grew faster and accumu-lated larger lipid reserves when water was available on a free-choice basis than when it was not. Triglycerides, the largest lipid fraction, increased most in response to water, free fatty acids and phospholipids increased less and hydrocarbons, sterols, sterol esters, mono and diglycerides did not change. The fatty acid composition of the triglycerides and free fatty acids also did not vary in response to water. The faster growing strain of mealworms, under both moist and dry conditions, also had larger fat reserves at pupation than did the slow growing strain, mostly because of increased triglyceride accumulation. The fatty acid composition of the triglyceride and free fatty acid fractions showed only minor quantitative differences between strains. The natural preference of T. molitor larvae for moist situations would result in larger lipid reserves for metamorphosis and early adult metabolism as well as more rapid larval development.     

Supercritical fluid extraction and characterization of lipids from algae scenedesmus obliquus

Supercritical carbon dioxide (SC‐CO₂) extractions (with and without ethanol as an entrainer) were carried out to remove lipids and pigments from protein concentrate of green algae (Scenedesmus obliquus) cultivated under controlled conditions. The content and fatty acid composition of algal lipids using column, thin‐layer (TLC) and gas‐liquid chromatography (GLC) were determined. Absorption spectra of extracted fractions showed the predominance of chlorophyll A (λ_max at 410nm). Single step supercritical carbon dioxide (SC‐CO₂) extraction resulted mostly in removal of neutral lipids and a part of glycolipids, but phospholipids were not extracted. Addition of ethanol to SC‐CO₂ increased the amount of glycolipids and phospholipids in the extract. TLC pattern of algal lipids showed that the main part of neutral lipids consisted of diglycerides, triglycerides, hydrocarbons, free sterols, and sterol esters. The glycolipids were mostly monogalactosyl diglyceride, digalactosyl diglyceride, esterified sterol glycoside, and sterol glycoside. In phospholipids, phosphatidyl choline, phosphatidyl glycerol, and phosphatidyl ethanolamine were the main compounds. Fatty acid composition patterns indicated the main fatty acids to be 16:0, 16:1, 16:2, 16:3, 16:4, 18:1, 18:2 and 18:3(a). Relatively high recovery of polyunsaturated fatty acids and essential fatty acids in supercritical fluid extracted algal lipids and protein isolates were observed.     

Lipids in cereals. 1. Pennisetum typhoideum

Two improved strains of Pennisetum typhoideum (‘bajra’) were found to have a free lipid content of about 5.0% and bound lipid content of about 0.5%. In the non-polar fraction, sterol esters and hydrocarbons, triglycerides, free fatty acids, free sterols and partial glycerides were present with triglycerides as the principal constituents. Polar lipids were separated by two-dimensional thin-layer chromatography and lecithin was found to be the major component. Sterol-containing glycolipids (sterol glycosides and esterified sterol glycosides) were present in appreciable amounts. Phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl inositol, lysophosphatidyl ethanolamine, lysolecithin, phosphatidic acid, poly-glycerophosphatide, mono- and di-galactosyl glycerides and cerebrosides have also been tentatively identified.     

Optimization of the enzyme-catalyzed synthesis of amino acid-based surfactants from palm oil fractions

The feasibility of using palm oil fractions as cheap and abundant sources of raw material for the synthesis of amino acid surfactants was investigated. Of a number of enzymes screened, the best results were obtained with the immobilized enzyme, Lipozyme. The effects of temperature, solvent, incubation period, fatty substrate/amino acid molar ratio, enzyme amount, and water removal on the reactions were analyzed and compared to those on reactions with free fatty acids and pure triglycerides as fatty substrates. All reactions were most efficient when carried out at high temperatures (70-80 degrees C) in hexane as a solvent. However, while reactions with free fatty acids proceeded better when a slight excess of the free fatty acids over the amino acids was used, reactions with triglycerides and palm oil fractions were best performed at equimolar ratios. Also, the addition of molecular sieves slightly enhanced reactions with free fatty acids but adversely affected reactions with triglycerides and palm oil fractions. Although reactions with palm oil fractions took longer (6 d) to reach equilibrium compared to reactions with free fatty acids (4 d) and pure triglycerides (4 d), better yields were obtained. Such lipase-catalyzed transacylation of palm oil fractions with amino acids is potentially useful in the production of mixed medium- to long-chain surfactants for specific applications.     

Chemical changes during the ripening of Domiati cheese made from dried milk

The ripening of Domiati cheese made from fresh and dried milk was investigated. Nitrogen fractions were determined, the proteinaceous fraction of cheese was analysed on Sephadex G-100 and the free fatty acids were determined by gas-liquid chromatography. The nitrogen fractions from fresh milk cheese had higher nitrogen concentrations than those from cheese made from dried milk. The elution pattern of the proteinaceous fractions and the pattern of free fatty acids of fresh and dried milk cheese were similar. However, the small molecular weight N fractions and the concentration of free fatty acids were higher in the former cheese than the latter.     

The in vitro lipolysis and biohydrogenation of monogalactosyldiglyceride by whole rumen contents and its fractions

The contribution of bacterial, protozoal, participate and cell-free fractions of rumen fluid to the lipolysis of monogalactolipid and the hydrogenation of its acyl constituents has been examined. Each of these fractions hydrolysed monogalactolipid and free fatty acids were the major acyl products. Almost all the radioactivity added as monogalactolipid to rumen fluid was distributed between the particulate and bacterial fractions and half to two-thirds of the radioactivity in each of the four fractions was recovered as free fatty acids. Both 16:3 and 18:3, after release from monogalactolipids, were hydrogenated to 16:2 and 18:2 at short incubation times. As incubation was continued there was a rapid decline in dienoic fatty acids and an increase in saturated and monoenoic fatty acids. There was a greater accumulation of trans-18: 1 than cis-18:1. Only the particulate fraction of rumen fluid gave patterns of hydrogenation similar to that obtained with rumen fluid. Bacteria in free suspension had little ability to hydrogenate trienoic fatty acids beyond the dienoic stage and neither protozoa nor the cell-free supernatant gave significant biohydrogenation of trienoic fatty acids. On the other hand, the presence of monoenoic and dienoic fatty acids in the bacterial, protozoal and cell-free fractions isolated from total rumen fluid after incubation with monogalactolipid indicated their transfer to these fractions after biohydrogenation in the particulate fraction.     

Refining of high oleic safflower oil: Effect on the sterols and tocopherols content

The purpose of this work was to study the influence of the industrial process steps on free fatty acids, peroxide value (PV), p-anisidine value (PAV), trans fatty acids, tocopherols and sterols (free, esterified and total) in high oleic safflower oil. Degumming, bleaching and deodorization steps removed 91.4% of free fatty acids, 96.31% of oxidation primary products (PV), and 54.57% of oxidation secondary products (PAV), from crude high oleic safflower oil. Degumming neither affected the content of sterified sterols nor its proportion with respect to the crude oil. A significant increment (p<0.05) in the content of free sterols was observed during degumming and bleaching due to the acid-catalyzed hydrolysis of steryl esters. A significant reduction (p<0.05) in the content of total sterols during bleaching was observed, which is attributed to a reduction in the sterified sterol fraction. During deodorization, free sterols were distilled from oil, with a gradual reduction in the total sterol content as a function of the deodorization temperature. α- and γ-tocopherols represented 93.3% of the total tocopherols in high oleic safflower crude oil. The refining process removed 28.5% of the tocopherols. Deodorization was the main step which increased the level of trans fatty acids as an effect of temperature and heating time.     

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.