ISOLATION AND CHARACTERIZATION OF AMARANTIN, THE 11S AMARANTH SEED GLOBULIN

The 11S globulin of seed storage protein of Amaranthus hypochondriacus, termed amarantin, was isolated. This fraction was evaluated for its purity by chromatographic techniques and ultracentrifugation. The 11S globulin was analyzed by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) without and with prior reduction of disulfide bonds, and by nondenaturing-PAGE. It exhibited an electrophoretic behavior similar to that of 11S-like proteins in other materials. Its apparent relative molecular weight was estimated to be 389 kDa by gel filtration chromatography at low ionic strength. Ultracentrifugation of the freeze-dried extract gave a sedimentation coefficient of 11S.     

MUSCADINE GRAPE SEED OILS

Dichloromethane-soluble constituents of seeds from ‘Welder’, ‘Regale’ and ‘Carlos’ muscadine grape cultivars were analyzed with a combined gas chromatograph-mass spectrometer. Five components of the extracts, which constituted 10-13% of the seed weights were separated. Stearic acid, glyceryl monostyrate and a stearic acid derivative were identified as the constituents of four of the separated peaks. Glyceryl monostyrate content of the extracted oils for ‘Carlos’, ‘Regale’ and ‘Welder’ cultivars were 94.1%, 89.4% and 72.7%, respectively, while their stearic acid contents ranged from 5.6% in ‘Carlos’ to 8.9% in ‘Regale’. Qualitative and quantitative differences between muscadine grape seed oils and those of nonmuscadine cultivars are also discussed.     

ISOLATION AND CHARACTERIZATION OF THE 11S GLOBULIN FROM AMARANTH SEEDS

Globulins of Amaranthus hypochondriacus were extracted with two different buffer systems which varied in ionic strength. SDS-PAGE analysis demonstrated that subunit patterns were different between the two extracting systems. Amarantin, the native 11S globulin of amaranth, and its subunits were purified by gel filtration chromatography and preparative electrophoresis. The native amarantin exhibited two heterogeneous forms of MW 330 and 400 kDa, which yielded the same subunit composition after reduction. SDS-PAGE analysis showed that prior to reduction, the 50–52 kDa subunit was the major band, and that after reduction, two new bands of 32–34 kDa and 22–24 kDa appeared. This is a typical characteristic of 11S proteins whose subunits consist of an acidic polypeptide (27–37 kDa) and a basic polypeptide (20–24 kDa) linked by a disulfide bond. Ultracentrification analysis showed that amarantin has a 11.9S sedimentation coefficient whereas DSC demonstrated that the denaturation temperatures in the presence of H₂O, Tris-HCl and K₂HPO₄-KH₂PO₄ are 99C, 99.8C and 103C, respectively.     

CHARACTERIZATION OF PHYTASE ACTIVITY IN LUPIN SEED

Lupin phytase (myo-inositol hexaphosphate phosphohydrolase) and the degradation of its substrate phytic acid were studied during seed germination. Phytase and acid phosphatase activities were detected in nongerminated seeds and increased from days 1 to 8 of germination, while the concentration of phytic acid decreased during the same period. Phytase was extracted with 2% CaCl₂ solution and partially purified by ammonium sulfate fractionation and HPLC-gel permeation chromatography. Substrate specificites were determined using pnitrophenylphosphate or phytic acid. The pH and temperature optima for the fraction obtained by gel permeation were 5.0 and 50C respectively, while the Km and V _max values were 0.33 mM and 0.13 μmol·mL^?1·min^?1, respectively. It was not possible to separate phytase from phosphatase by use of gel permeation chromatography due to similarities in apparent molecular mass, however resolution of the two enzymes was achieved by DEAE-cellulose chromatography.     

溶剂提取葡萄籽油工艺的研究

葡萄籽出油率为指标，石油醚（60℃～90℃）为脱脂溶剂，通过几种不同溶剂提取方法对葡萄籽制油比较。确定了最佳的提取方法及条件：采用索氏提取，提取温度85℃、回流时间4h、固液比1：7（g/mL）的条件下出油率高，油质清亮，出油率为25．56％。     

SEPARATION OF STEROLS AND TRITERPENE ALCOHOLS FROM UNSAPONIFIABLE FRACTIONS OF THREE PLANT SEED OILS

Preparative HPLC was used to separate sterols and triterpene alcohols from the unsaponifiable matters in plant oils from Camellia weiningensis L., Brassica juncea L. and Microula sikkimensis . The isolated sterols and triterpene alcohols were acetylated and further purified by AgNO₃ impregnated silica gel preparative thin layer chromatography (TLC). The isolated acetyl derivatives of sterols and triterpene alcohols were identified by melting point, specific rotation, infrared and mass spectrometry. The sterols were brassicasterol, campesterol, stigmasterol, β-sitosterol and Θ⁵-avenasterol, Θ⁷-avenasterol, Θ⁷-stigmastenol and α-spinasterol. The triterpene alcohols were cycloartanol, cycloartenol, 24-methylenecycloartanol, cyclobranol, dammaradienol, tirucalla-7,24-dienol, butyrospermol, β-amyrin, germanicol, α-4-taraxasterol and lupeol.     

CHARACTERIZATION OF PHYTOCHELATIN-LIKE COMPLEXES FROM FLAX (LINUM USITATISSIMUM) SEED

Proteins were extracted from dehulled and delipidated powder of flaxseed (cv. NorMan), and fractionated by DEAE‐Sephacel onion exchange chromatography. Ultraviolet absorbance scans of ion exchange fractions eluting in buffers at pH 8.6 containing 0.45 M and 0.50M NaCl revealed A₂₅₅ >A₂₈₀. Furthermore, the A₂₅₅ was reduced upon acidification and restored by adjusting to the original pH, confirming spectral characteristics typical of metal‐thiolate complexes. Characteristic circular dichroism spectra and reversible aggregation‐dissociation behavior under low and high salt conditions observed for these fractions are also typical of metal binding phytochelatins reported for other plants, while the presence of aromatic amino acids indicated by fluorescence spectra suggests some similarity to nonmetallothionein proteins. Further work is underway to investigate the prevalence of these and other complexes as well as the distribution of metals in different protein fractions of flaxseed, as a function of cultivar and geographical location.     

PURIFICATION AND CHARACTERIZATION OF CANOLA SEED (BRASSICA sp.) PHYTASE

Germinated Altex and Westar (Brassica napus) and Candle and Tobin (B. campestris) cultivars of Canola were screened for phytase activity. On the basis of this preliminary screening, 7-day germinated Altex seedlings were selected as a source for isolation and characterization of phytase. Partial purification of a crude extract (FI) by acetone precipitation resulted in an 8-fold increase in phytase activity. Ion-exchange chromatography of the partially purified preparation (FII) yielded two fractions (FIIIA and FIIIB) both of which demonstrated phytase and phosphatase activities. Further purification by gel filtration chromatography resulted in two fractions (FIVA1 and FIVA2) from fraction FIIIA and two fractions (FIVB1 and FIVB2) from fraction FIIIB. Fraction FIVB1 demonstrated both phytase and phosphatase activities, FIVA2 and FIVB2 demonstrated phosphatase activity but no phytase activity and FIVA1 showed phytase but no phosphatase activity. Fraction FIVB1, which showed highest phytase activity (5.3 IU/mg protein), had the following characteristics: temperature optimum of 50°C, pH optimum of 5.2, K_m of 0.36 mM and relative activity for pyrophosphate 232 times higher than for phytate.     

超临界CO2提取栝楼籽油的工艺研究

利用正交实验法对栝楼籽油的超临界CO2提取工艺进行了优化.以栝楼籽油的得率为指标,考察萃取压力、温度、时间和粉碎度对栝楼籽油得率的影响,得到最佳工艺条件为:萃取时间5h、原料粉碎度0.42mm、萃取温度45℃和萃取压力30MPa,栝楼籽油提取率可高达56.38%,且栝楼籽油暗红透明,香气纯正.     

CHEMICAL CHANGES IN STORED TOASTED CRUDE CANOLA AND SESAME SEED OILS

'Alto'canola seed and sesame seed were toasted at 180, 200, 220, 240, and 260C, for 8 min or 10 min. As temperature increased, minor changes in fatty acid composition were observed. Darkness and blueness in canola oil increased with toasting temperatures up to 240C, and then decreased. The darkness, greenness and yellowness of sesame seed oil increased with increasing toasting temperature. The overall color of canola oil was significantly darker than that of sesame seed oil (α 0.05). 2-Thiobarbituric acid (TBA) numbers for both oils increased as toasting temperature increased. TBA numbers of the canola oil increased with extended storage time up to 4 weeks and then decreased. For sesame seed oil, TBA numbers also were influenced by storage time, but less change was observed than for canola oil. 2-Thiobarbituric acid reactive substances (TBARS) content of canola oil was significantly higher than that for sesame seed oil when TBA numbers were compared to the same treatment.     

EXTRACTION OF VICTORIA AND RED GLOBE GRAPE SEED OILS USING SUPERCRITICAL CARBON DIOXIDE WITH AND WITHOUT ETHANOL

SFE of the oils of two varieties of grape seeds (Victoria and Red Globe) was performed in a flow apparatus at 40C and 250 bar. The effect of the solvent on the extraction yield was studied using CO₂ and CO₂ modified with ethanol, and the yield of extraction was compared with conventional extraction methods (Bligh and Dyer and Soxhlet using hexane). SC CO₂  +  ethanol extracted higher lipid amounts from both varieties, compared with SC CO₂ extraction. The comparison between SFE and conventional extraction methods showed that the highest extraction yield was obtained with SC CO₂  +  ethanol (10%, w/w) (14.7 and 11.8% for Red Globe and Victoria grape seeds, respectively), while pure SC CO₂ afforded the lowest lipid yields. The fatty acid compositions of the oils obtained by SFE were analyzed. Fractions containing higher proportions of PUFAs were obtained at lower solvent/dry grape seed ratios, while fractions richer in SFAs and MUFAs were obtained at higher solvent/dry grape seed ratios.

PRACTICAL APPLICATIONS

SFE could fractionate grape seed oil and afford various grades of oil containing different proportions of fatty acids. The highest grape seed lipid yield obtained was with SC CO₂ + ethanol, making this solvent a promising and powerful one for grape seed oil extraction, showing a great advantage compared with conventional extraction methods.     

GUAVA SEED PROTEIN ISOLATE: FUNCTIONAL AND NUTRITIONAL CHARACTERIZATION

A protein isolate from the guava seed meal (Psidium guajava) was obtained by use of isoelectric precipitation, with 78% extraction yield (extracted protein to that in raw material) and 96.7% protein content of the product. Protein solubilization was done at pH 11.5 and 40C for 30 min, followed by precipitation at its isoelectric point (pH 5). Solubility of the isolate was minimal at pH 4 to 6, and increased below pH 4 and above pH 6. Emulsifying capacity and stability of the emulsion was maximum at pH 8. However, the water and oil absorption capacity, as well as the foaming capacity and foam stability, were relatively low. The essential amino acid profile of the guava seed protein isolate, except for lysine content, is above that proposed in the FAO/WHO pattern for adults. The isolate is also an important source of tryptophan. Its in‐vitro protein digestibility was higher than for soybean isolate.     

PURIFICATION AND CHARACTERIZATION OF LIPOXYGENASE ISOZYMES FROM CANOLA (Brassica napus cv, WESTAR) SEED

Four isozymes, I', II'a, II'b and III’ of lipoxygenase (EC 1.13.11.12) from Canola (Brassica napus, cv Westar) seed were purified by successive chromatography on ion-exchange and size-exclusion columns using a Fast Protein Liquid Chromatograph (FPLC). The homogeneity of each isozyme was demonstrated by a single protein band on SDS-polyacrylamide gel electrophoresis. The molecular weights of isozymes I', II'a, II'b and III’ were 72, 000, 106, 000, 78, 000 and 62, 000, respectively. The optimum pH for lipoxygenase activity was 6.5 for isozyme I’ and 6.0 for isozymes II'b, II'b and III'. Apparent K_m value for isozymes I', II'a, II'b and III’ were 5.5 × 10^?4 M, 3.4 × 10^?4 M, 4.0 × 10^?4 M and 3.8 × 10^?4 M, respectively. Isozyme I’ displayed preferential activity towards monolinoleate and dilinoleate, while isozyme II'a demonstrated preferential activity towards dilinoleate followed by mono- and trilinoleate. No enzymatic activity was observed with both isozymes I’ and II'a toward free linoleic acid. Isozyme II'b showed activity towards free linoleate as well as mono-, di- and trilinoleate. Isozyme III’ showed preferential activity towards free linoleate. The activity of isozymes I’ and II'a was inhibited completely by the addition of 10 mM and 4 mM KCN, respectively, while the addition of 3 mM and 10 mM KCN to isozymes II'b and III', respectively, increased activity by approximately 20%.     

ISOLATION, PURIFICATION AND CHARACTERIZATION OF THE SEED STORAGE GLOBULIN AND ITS POLYMERIZED FORM FROM TRITICUM AESTIVUM

The salt-soluble globulin and its polymerized counterpart from wheat (Triticum aestivum) seed were isolated and purified to homogeneity employing both gel filtration and anion exchange chromatography. The two globulins were purified free of any purothionin (an oxidation-reduction protein) contamination. Some of the physico-chemical properties of purothionin are also reported. Both globulins were found to be oligomers composed of two polypeptide chains, i.e., 35,000 and 49,000 Da, with no apparent evidence of any covalent inter-chain disulfide linkages between these major subunits. The molecular weights for the globulin and its polymerized (i.e., polymerized via interchain disulfide bonds between various subunits of differing molecular weights, excluding any interchain disulfide bonds between the 35,000 and 49,000 Da subunits) counterpart were determined to be 474,000 and 567,000 Da, respectively, by gel chromatography. Surface charge profiles of fractions 2 and 3 were determined using electrophoretic isoelectric focusing, electrophoretic titration and zeta potential analysis and indicated pIs of 6.90 and 6.55, respectively. The nonpolymerized globulin was found to be more positively charged below its isoelectric point and less negatively charged above it than its polymerized counterpart. Microcalorimetric studies indicated that the two globulins had similar T_m values.     

苋菜籽和昆诺阿藜籽的营养和利用

介绍了欧洲人在食用谷物时产生的过敏反应的背景及针对谷物过敏症进行的无面筋食品原料资源—假谷物的开发情况,特别是苋菜籽和昆诺阿藜籽的营养价值和性质。