R. S. Farag

ANTIOXIDANT ACTIVITY OF SOME SPICE ESSENTIAL OILS ON LINOLEIC ACID OXIDATION IN AQUEOUS MEDIA

Some spice essential oils (caraway, clove, cumin, rosemary, sage and thyme) and their major constituents were added to emulsified linoleic acid in aqueous media to examine their antioxidant activity. The methods used for measuring linoleic acid oxidation were coupled oxidation ofβ-carotene, conjugated diene formation and thiobarbituric acid test. The essential oils under study possess an antioxidant effect and this phenomenon was increased by increasing their concentration. Generally, the effectiveness of the various essential oils on linoleic acid oxidation was in the following descending order: caraway >sage>cumin>rosemary>thyme>clove. It appears that there was a relationship between the antioxidant effect and the chemical composition of the oils.

INFLUENCE OF THYME AND CLOVE ESSENTIAL OILS ON COTTONSEED OIL OXIDATION

Simple model systems composed of refined cottonseed oil and thyme oil or clove oil, without additives, were designed to approximate conditions in natural oils in order to study their oxidation behavior. Three methods were used to follow cottonseed oil oxidation, i.e., coupled oxidation withβ-carotene, the TBA test and hydroperoxide number. The results illustrate that clove and thyme oils at various concentrations exhibit antioxidant activity and this phenomenon for clove oil is superior to that of thyme oil. Sensory evaluation tests indicate that the addition of thyme oil or clove oil to cottonseed oil at concentrations ranging from 50 to 1200 ppm do not affect the odor note of cottonseed oil. Therefore, thyme and clove essential oils are recommended for use as natural antioxidants to suppress lipid oxidation.

Use of some essential oils as natural preservatives for butter

Thyme and cumin essential oils were used in the present study in an attempt to prevent butter deterioration during storage at room temperature. Butter oxidation and lipolysis were followed by measuring the acid, peroxide and TBA values. Lipolytic activity and total microbial and lipolytic bacterial counts were also measured. During butter storage, very little change in the peroxide and TBA values were found while a gradual increase in the acid value was noticed. The addition of cumin and thyme oils at 200 ppm to butter caused very little increase in the acid value. The data for lipolytic bacterial counts were in general agreement with the acid values. Thyme and cumin essential oils showed a greater anti-hydrolytic effect and act as superior preservatives compared to BHT.

Fractional crystallization and gas chromatographie analysis of fatty acids as a means of detecting butterfat adulteration

A method has been devised which gives the distribution of saturated and unsaturated fatty acids of pure and adulterated cow and buffalo ghee with lard or margarine. It involves fractionation of pure and adulterated butterfat into fractions by fractional crystallization. The composition of the fatty acids liberated by the hydrolysis of each of the fractions was determined by gas chromatography. Adulteration of cow and buffalo ghee with various levels of lard or margarine caused significant changes in certain fatty acids, i.e., 22:0, 18:1, 18:0 and 16:0. It is possible to determine the extent of admixture of lard or margarine to either cow or buffalo ghee by applying a simple regression equation for certain fatty acids. This technique provides a basis for the detection of lipid adulteration.

Use of unsaponifiable matter for detection of ghee adulteration with other fats

Gas liquid chromatography (GLC) was used for the detection of lard and margarine added to buffalo and cow ghee. The chromatograms of the unsaponifiable matter could be divided into two parts representing hydrocarbons and sterols. Hydrocarbons were fractionated by GLC into 3–6 different compounds depending on the lipid origin. The sterols were cholesterol and β-sitosterol. The content of cholesterol in lipid samples was in the following decreasing order: cow > buffalo > lard > margarine. With β-sitosterol, the concentration order was: margarine > buffalo > cow > lard. The ratios of total hydrocarbons to total sterols in the unsaponifiable matter for margarine and lard were the most different for the various lipids. Adulteration of cow and buffalo ghee with various levels of lard or margarine caused significant changes in the unsaponifiable compounds. It is possible to determine the extent of admixture of lard or margarine to either cow or buffalo ghee by applying a simple regression equation for each unsaponifiable component. Hence, an examination of unsaponifiable matter appears to provide a rapid and simple laboratory method for the detection of ghee adulteration.

Linoleic acid oxidation catalyzed by various amino acids and cupric ions in freeze-dried model systems

The present investigation into the effect of amino acids on linoleic acid oxidation in freeze-dried model system illustrates the existence of an autocatalytic chain reaction, in which all amino acids, except cysteine, exhibited minor antioxidant behavior. The antioxidant effect might be attributed to the absence of protonated amino nitrogen. Linoleic acid alone had an induction period of 15 hr, and on the addition of various α-amino acids, the systems had induction periods ranging from 16-19 hr. This increase did not exhibit any specific function for the studied amino acids. Cysteine exhibited an exceptional prooxidant effect due to the role of the HS-group. The addition of copper at concentrations of 10-5M and 10-3M to the model systems composed of linoleic acid and various a-amino acids exhibited minor and highly prooxidant effects, respectively, The prooxidant effect of these amino acids in the presence of copper might be due to amino acids-copper complexes.

Effects of various carbon and nitrogen sources on fungal lipid production

The efficiency of lipid production byTolyposporium ehrenbergii andSpacelotheca reiliana (family Ustilaginaceae) cultivated on a fat-free medium was evaluated. The fungi were artificially cultured on media containing various monoor disaccharides and urea or peptone as basic sources for carbon and nitrogen, respectively. Some natural and industrial byproducts (glycerol, glucose syrup, potato hydrolysate and molasses hydrolysate) were also used as principal carbon sources for fungal growth. Media containing fructose/peptone or glucose/peptone were the most efficient for fungal fat production during one week of incubation. After a two-week incubation period, highest phospholipid concentrations were found in S.reiliana andT. ehrenbergii mycelia obtained from media containing molasses hydrolysate/peptone and glycerol/urea, respectively. Fatty acid analysis of the fungal growth indicated the presence of a wide range of fatty acids, i.e., odd-and even-carbon numbered acids, both saturated and unsaturated. The results demon-strated that the variability in the fatty acid composition largely depends on the type of sugar and nitrogen sources and the age of the culture.

The lipids of various fungi grown on an artificial medium

The lipids extracted from various fungi belonging to the generaAspergillus, Fusarium andPenicillium cultivated on Davis medium were studied. The fatty acids from fungal lipids were fractionated by gas liquid chromatography (GLC) and the main fatty acids were palmitoleic, oleic, stearic, linoleic and arachidic. The results demonstrated that the fatty acid composition of various fungi could be used as criteria for fungal taxonomy. The unsaponifiable matter of the fungi could be divided into two fractions, i.e., hydrocarbons and sterols. The hydrocarbon fraction constitutes an important part because its amount ranged from 30.14 to 80.97% according to the fungal species. The sterol fraction of the unsaponifiable part of fungal lipids was much simpler in composition. Analysis by GLC indicated that sterol composition could be used to differentiate among fungi belonging to different genera as well as among species belonging to one genus.

Chemical studies on corn embryos infected by various fungi

The occurrence of various fungi in corn kernels obtained from eight localities in Egypt in two successive years was studied. Values for refractive index, color, acid value, saponification value, iodine value, peroxide value and unsaponifiable matter content of oils extracted from corn embryos that were deliberately infected by various fungi were compared to those for oil extracted from healthy embryos. Spectrometric analyses (UV, visible and IR) were done to deduce differences in the functional groups of the oils. Corn oil extracted from embryos infected with various fungi contained the same lipid classes as the oil extracted from healthy embryos. Contents of mono- and diglycerides and free fatty acids were much smaller for the oil extracted from healthy embryos. The fatty acid and unsaponifiable compositions of oils were studied by gas liquid chromatography. The fatty acid composition of corn oil extracted from infected embryos showed that some new and short-chain fatty acids had appeared and that some of the 18:2 was converted to 18:0. Analysis of the hydrocarbon fraction of the unsaponifiables showed also that some new compounds had appeared and others disappeared. The sterols were greatly influenced by the fungi and the ratio between different sterols might be used to characterize the effect of fungi. Aflatoxin B1 content of oil extracted from corn embryos infected byA. flavus was 300 µg/kg.

Effects of varied substrates on aflatoxin production byA. parasiticus

Sterilized and nonsterilized wheat kernels, soybean seeds, sesame seeds, peanut and faba bean were infected byA. parasiticus. The chemical composition, aflatoxin content and fatty acid patterns of the seeds were determined. The aflatoxins B1, B2, G1 and G2 were detected, and the amounts of the unsaturated toxins (B1 and G1) were greater than the respective dihydro derivatives (B2 and G2). Sterilized seeds infected by the fungus contained greater amounts of aflatoxins than those infected without previous sterilization. the highest and lowest toxicity indices were recorded for sterilized wheat and soybeans, respectively. Sesame, peanut and soybean exhibited intermediate toxicity indices. The toxicity of the aflatoxins produced was related significantly in every instance to the carbohydrate and lipid:protein ratio, and not to the polyunsaturated fatty acids of the seeds.