LIPID AND AROMA COMPOSITION OF BLACK CUMIN (NIGELLA SATIVA L.) SEEDS FROM TUNISIA

The chemical composition of Tunisian Nigella sativa L. seeds was investigated. The results showed that linoleic acid (C18:2) was the major fatty acid with 65.1% of total fatty acids (TFAs) followed by oleic acid (C18:1) with 12.7% of TFAs. Neutral lipids (NLs) were mainly composed of triacylglycerols with 98.4% of total NLs. Polar lipids were mainly composed of phosphatidylcholine as the major phospholipid subclass, whereas digalactosyldiacylglycerol was the major galactolipid. Total sterols (TSs) represented 2.2% of the fixed oil and were composed of (-sitosterol as the major sterol representing 60.2% of the TSs. The results indicated that the sterols were mainly present in the esterified and in the free forms with 51.2 and 36.1%, respectively, of TS content. Finally, the aroma composition of the volatile oil from oleoresin exhibited the presence of many bioactive compounds such as p-cymene as the major component followed by ocimene, α -thujene, octen-3-ol with appreciable rates of 1,8-cineole and thymol.

PRACTICAL APPLICATIONS

The results obtained showed that Nigella sativa L. seeds were a good source of polyunsaturated fatty acids (PUFAs), phytosterols (PSs) and phospholipids (PhLs) for the human diet. These seeds could be used by the food industry for formulating functional foods enriched with PUFAs and PSs. For pharmaceutical applications, N. sativa L. conjugated sterols could be used as precursors for the hemisynthesis of many hydrosoluble steroids. Also, N. sativa L. seeds are a good source of PhLs and aroma compounds, and therefore, they could be utilized in biscuit manufacturing and in food flavoring. The presence of many bioactive compounds in N. sativa L. essential oil (p-cymene, limonene, α-pinene, linalool and thymol), known for their powerful antimicrobial function, could support the utilization of the essential oil bactericidal agents.     

CHEMICAL COMPOSITION OF OIL FROM COULA EDULIS (Bail.) NUTS

Coula edulis (Bail.) nuts are generally used as food components in the littoral and southern part of Cameroon. The physicochemical characteristics, the fatty acids and the triacylglycerols (TGs) of Coula edulis (Bail.) nut oil from two different agroclimatical zones of Cameroon were studied. The oil content varied according to the zone (33.50 – 36.65%). The iodine value (90 – 95), saponification value (180 – 185) and the nitrogen (2.16 – 2.40%), and ash (2.5 to 2.7%) contents were similar for the two types of nuts studied. The main fatty acid of the oil was oleic acid (95.5 – 97.4%), as determined by capillary gas chromatographic analysis. The triacylglycerol profile obtained by reversed phase liquid     

COMPARISON OF CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY OF GLYCOSIDICALLY BOUND AND FREE VOLATILES FROM CLOVE (EUGENIA CARYOPHYLLATA THUNB.)

The present article reports on the chemical composition and antioxidant activity of clove glycosidically bound volatile compounds in comparison with their essential oil. The comparison of chemical composition of volatile aglycones with the chemical composition of essential oil revealed only eugenol as identical. To measure the antioxidative activity of the clove enzymatically released aglycones and its essential oil, two different assays were performed: the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging method and the ferric reducing/antioxidant power (FRAP) assay. Both methods showed that the clove volatile aglycones possess lower antioxidant properties than its essential oil. The volatile aglycones radical-scavenging activity measured by DPPH method was lower than butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) activity. The reducing capacity measured by FRAP method for volatile aglycones was lower than BHA capacity and higher than BHT capacity. Some differences in activity obtained by two methods could be explained with different solvent polarity.

PRACTICAL APPLICATIONS

Many secondary metabolites are glycosylated and accumulate as nonvolatile glycosides. Since the glycosides are able to release their aglycones by enzymatic hydrolysis, these compounds could be considered as possible precursors of antioxidant substances in plant. They may contribute to the total antioxidant activity of plant and could be used as natural antioxidants.     

CHANGE OF FAT CONTENT AND FATTY ACID COMPOSITION OF TURKISH HAZELNUTS (CORYLUS AVELLANA L.) DURING STORAGE

Hazelnuts (Corylus avellana L.) were collected from three different cultivars (Tombul, Palaz and Kal?nkara) at the harvest season of 1996. The dried nuts were stored shelled and unshelled in polyethylene bags at 21C and 60–65% relative humidity for 12 months. During storage, the total fat content increased, the palmitic and oleic acid content of the oil increased, linoleic acid, ranged from 12.41 to 10.35%. No significant differences were found for other fatty acids during storage. The effect of storage of shelled and unshelled hazelnuts on the total fat content was significant.     

COMPARISON OF PEROXIDASES FROM BARLEY KERNEL (Hordeum vulgare L.) AND WHEAT GERM (Triticum aestivum L.): ISOLATION AND PRELIMINARY CHARACTERIZATION

Peroxidases (POD) of crude extracts from barley and wheat germ were separated, partially purified using salt fractionation, ion-exchange and hydrophobic interaction chromatographies and their properties examined. Barley and wheat germ POD contained basic, neutral and anionic isoforms as confirmed by isoelectric focusing. Toyopearl-Butyl 650 M chromatography resolved POD into four cationic fractions. Chromatography of wheat germ extract on CM-Sepharose isolated an anionic and a neutral fraction. Following chromatography on Concanavalin-A Sepharose, enzymes from both cereals showed differences in their elution properties. Optimum pH ranges were 4.0 to 5.5 (barley) and 5.3 to > 6.3 (wheat germ) and POD reacted differently under acidic or basic conditions. Their catalytic behavior in the presence of calcium also differed. Kinetics of POD were of Michaelian type with a ping-pong mechanism and Michaelis constants of guaiacol oxidation in the presence of hydrogen peroxide varied from one enzymatic group to another.     

HEAT TREATMENT AND INACTIVATION OF TRYPSIN-CHYMOTRYPSIN INHIBITORS AND LECTINS FROM BEANS (Phaseolus vulgaris L.)

This work investigates some factors affecting the inactivation of common bean trypsin inhibitor and phytohemagglutin. Trypsin inhibitor activity was totally stable to heat treatment (30 min, 97C) in the total protein extract, albumin or globulin fraction. Heat treatment of the whole beans easily inactivated the inhibitor. Heat resistance of trypsin inhibitor was intermediate in the bean flour which received the same heat treatment. Independent of sample, the inhibitor was very stable to heat treatment at neutral and acidic pH and labile under strong alkaline conditions. Heating for 30 min in boiling water at pH 12 resulted in complete inactivation of the trypsin inhibitor. Autoclaving (121C) soaked whole beans and flour for 5 min inactivated 55% of the trypsin inhibitor activity in the soaked flour and 75% in the whole beans. After autoclaving 20 min, inactivation of trypsin inhibitor was about 65% in the flour and 80% in the whole beans. The phytohemagglutinin (lectin) activity was totally destroyed in the autoclaved beans after 5 min and in the flour after 15 min.     

ISOLATION AND IDENTIFICATION OF ANTIOXIDATIVE FLAVONOID GLYCOSIDES FROM THYME (THYMUS VULGARIS L.)

Five flavonoid glycosides were isolated from the butanol-soluble fraction of thyme extracts. Their structures were determined by spectral analyses (NMR, MS). Their antioxidant activity was evaluated in two models (DPPH radical scavenging and Trolox equivalent antioxidant activity). The most active compounds were found to be eriodictyol-7-rutinoside and luteolin-7-O-β-glucopyranoside.     

NUTRIENT COMPOSITION OF BEACH PEA (LATHYRUS MARITIMUS L.) SEEDS AND POD SHELLS AT VARIOUS STAGES OF MATURITY

The biochemical composition of seeds and pod shells of beach pea was determined during growth and maturation. The content of crude and soluble protein, soluble sugars and phenolics was high in the fresh green seeds and pod shells, but these decreased rapidly during seed maturation. Meanwhile, the corresponding content of starch increased in seeds and decreased in pod shells. Glutamic acid was the predominant amino acid in seeds and aspartic acid was dominant in pod shells. Levels of arginine, alanine and threonine were highest in fresh green seeds. Methionine and cysteine content increased during seed maturation, but declined in pod shells. Free amino acid content decreased rapidly during latter stages of seed maturation. Potassium, calcium, sodium and phosphorus were the predominant minerals in fresh green seeds and pod shells, but iron content was highest in mature pod shells relative to that of other stages of maturation. Major changes in color (pigment interchanges) also occurred during maturation. Based on its biochemical composition, beach pea may become of special importance for widespread cultivation.     

PURIFICATION AND PROPERTIES OF TWO ACID PEROXIDASES FROM BRUSSELS SPROUTS (Brassica oleraceae L.)

An acid peroxidase isoenzyme (A1) from Brussels sprouts (Brassica oleraceae L.) has been purified while another isoenzyme (A2) has been partially purified. Studies of their properties leading to a potential application in immunoassays as an alternative to horseradish peroxidase were conducted. Isoenzyme A1 was purified 503 fold, through ammonium sulfate and acetone fractionation, and successive chromatography on DEAE-cellulose, Sephadex G-100 and Mono-S (FPLC system) columns. Isoenzyme A1 had a pI of 4.0, a molecular weight of 90 kDa, and contained two identical molecular weight subunits. Preliminary studies indicated a pI of 4.7 for isoenzyme A2. ABTS [2,2'-azino-di-(3-ethyl-benzthiazoline-6-sulfonic acid)] K_m values (0.2 mM) for both isoenzymes are 20 times lower than those reported for commercial horseradish peroxidase anionic isoenzymes. Optimum pH for activity of isoenzymes A1 and A2 were 4.3 and 4.5, respectively. Optimum temperature for isoenzyme A1 was 57C, with an activation energy for inactivation of 148.8 kJ/mol.     

SELECTION AND BIOCHEMICAL CHARACTERISATION OF SACCHAROMYCES CEREVISIAE AND KLOECKERA APICULATA STRAINS ISOLATED FROM SPANISH CIDER

The behaviour of different strains of Saccharomyces cerevisiae and Kloeckera apiculata in apple juice fermentation was studied. Ethanol production was higher for Saccharomyces strains while residual sugars and ethyl acetate content was higher for Kloeckera strains. Kl. apiculata fermented products showed the lowest amount of higher alcohols and the lowest content in organic acids with the exception of acetic acid, so this yeast produced an increment in volatile acidity. On the basis of ethyl acetate, hydrogen sulfide, and acetic acid production, fermentative ability, potassium metabisulfite resistance and sporulation percentage, one strain from Sacch. cerevisiae could be employed as starter for making cider.     

海蜇头糖蛋白基本组成及结构

对海蜇头糖蛋白的基本组成和结构进行研究探讨.采用多步分离纯化方法获得电泳纯的海蜇头糖蛋白JGP-Ⅲ.经化学分析方法测定,JGP-Ⅲ中含有12.61%总糖,74.34%总蛋白,8.47%氨基糖,0.84%糖醛酸,1.06%硫酸根、0.92%唾液酸.JGP-Ⅲ的单糖组成主要有氨基葡萄糖,氨基半乳糖,葡萄糖,甘露糖,岩藻糖和鼠李糖.氨基酸组成中甘氨酸含量最高,其次为缬氨酸、谷氨酸、丙氨酸、脯氨酸、天门冬氨酸等,缺乏色氨酸和组氨酸.JGP-Ⅲ经消除反应前后紫外吸收和氨基酸组成的变化以及糖肽酶F作用后分子量的变化,表明JGP-Ⅲ中即有O-连接糖肽键的存在又有N-连接糖肽键的存在.通过红外光谱分析,发现JGP-Ⅲ具有糖蛋白的典型结构.