外源抗氧化剂α-生育酚在河蟹肌肉脂肪-蛋白质氧化体系中的作用

为了考察添加α-生育酚对河蟹肌肉中氧化脂肪-蛋白质体系的影响,以采集的河蟹肉为研究对象,通过测定蟹肉肌原纤维蛋白中巯基含量、表面疏水性、二级结构变化以及蛋白电泳情况,研究常温贮藏条件下氧化脂肪-蛋白质模拟体系中肌原纤维蛋白的变化。结果显示,蟹油经过12、24?h氧化后,脂肪酸组成发生变化,不饱和脂肪酸相对含量明显下降。添加24?h氧化蟹油的河蟹肌肉中,活性巯基含量的减少和表面疏水性的增加较为显著,氧化程度越高,α-螺旋、β-折叠相对含量越少,β-转角则越多;添加α-生育酚的处理组与相应的对照组相比,活性巯基含量的减少、表面疏水性的增加显著减缓,α-螺旋、β-折叠相对含量较多,β-转角较少,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）结果显示,抗氧化剂的添加对肌原纤维蛋白降解有一定的抑制效果,条带光密度分析显示仅有个别组间条带有显著差异,SDS-PAGE用于检测蛋白质氧化程度不及活性巯基和表面疏水性指标灵敏。研究表明氧化蟹油能够加速蛋白质的变性,且氧化程度越高,效果越显著;α-生育酚对氧化脂肪诱导的蛋白质变性具有显著的抑制作用。     

Slow triplet β-gliadin from cappelle-desprez

The third and slowest member of a triplet of β-gliadins seen in the electrophoretic pattern of Cappelle-Desprez gliadin has been isolated. It appears to be a single-chain protein that is free from carbohydrate and SH groups and has a molecular weight of 41000. The amino acid analysis is typical of many gliadins, with high contents of Glx and Pro, 93% of the side-chain COOH amidated, and 23 (Tyr + Phe) per molecule. Microheterogeneity may be present.     

Mechanism for formation of ovalbumin–fatty acid salt mixed gels

In this study, changes in the secondary structure of ovalbumin (OVA) during sodium caprate-induced gel formation were analyzed by FT-IR to help clarify mechanisms of protein gelation. Due to aggregation, there was an increase in intermolecular β-sheet bands and a decrease in α-helix and intramolecular β-sheet content during sodium caprate-induced gel formation. Furthermore, heat treatment of the gel caused a further enhancement in the content of intermolecular β-sheet bands. These results suggest that, similar to β-lactoglobulin gels, sodium caprate-induced OVA gels and heat-induced OVA gels form by similar mechanisms, although the sodium caprate-induced gel formation is accompanied by less marked changes in protein conformation.     

A fast-moving beta-gliadin from Cappelle-Desprez

A Cappelle-Desprez gliadin, in the fast β-region, has been isolated. The amino acid analysis is typical of gliadins in general. The protein has a single polypeptide chain of molecular weight 42 000 and appears to be free from carbohydrate and SH groups. The fact that its electrophoretic mobility is higher than that of a β-gliadin of lower mol. wt. is attributed to the presence of 2 His and 1 Arg extra.     

冷冻酸奶

近年来冷冻酸奶在冷冻甜食市场中增长迅速，它别于酸味冰淇淋，其主要特点是不仅具有冰淇淋（低酸度）的感官特征及风味，而且有酸奶（低脂肪，乳酸菌发酵）的特殊营养价值，按其成分可称之为酸奶冰淇淋。     

α-D-Polyglucane-Iodine Complexes

The temperature-dependent dyeability of oligoglucanes and polyglucanes with I₂/KI solution is based on the interaction between iodine and the C-atoms of glucosidic bonds (Vetter and Thorn [1, 2]). Only when the helix is compressed, the expansion of the lumen that is necessary for the attachment of iodine bands is achieved as suggested by Freudenberg et al. in 1939 [3]. The development of colour starts with the maltododecaosis (just over two spirals) within a temperature range of 20 to 25°C adsorbing one pentaiodide and bringing about a pale shade of pink. The rich blue tone is achieved with pure amyloses forming a maximum of about 610 to 620 nm. Unramified polysaccharides which had been synthesised by our team from 30 glucoside residues, still showed a purple colour with a maximum of 510 nm at temperatures from 20 to 25°C. Defined polysaccharides from 40 residues are bluish-purple (just 7 spirals of a tension-free helix) with a maximum absorption of about 550 nm. According to our knowledge, the rich blue tone requires at least 50 glucoside residues linked in an unramified chain [1, 2]. Amylopectin from potatoes has a maximum of 575 to 580 nm which shifts to 555 to 560 nm after partial break-down into β-dextrin by β-amylase (EC 3.2.1.2) and does a long-wave re-shift to 570 nm after splitting off of the side-chain stumps in the basic structure by pullulanase (EC 3.2.1.41). In the case of maize, the maximum is 535 nm for amylopectin, 520 nm for β-dextrin, and 555 nm for the basic structure. This means that in amylopectin from potatoes the helical sections available for the adsorption of iodine bands are longer than those in amylopectin from maize [4]. In glycogen iodine accumulates in a diffuse manner without forming any long bands. For this reason, an absorption shoulder of merely 400 to 500 nm is found by photometry [4]. A treatment with β-amylase makes the situation even worse; only when the side-chain stumps are separated by pullulanase does the formation of iodine bands in the basic structure of the glycogen improve to a maximum of 500 nm. This maximum corresponds to unramified sections of less than 30 glucoside residues [4, 2, 6].     

β-环糊精包合法分离亚麻油中α-亚麻酸工艺研究

从亚麻油中分离高纯度α-亚麻酸。采用β-环糊精包合法从亚麻油中分离α-亚麻酸,利用响应面分析法对β-环糊精包合法分离α-亚麻酸的提取工艺进行了优化。最佳工艺条件为:(混合脂肪酸+无水乙醇):β-环糊精=1:7,包合温度59℃,包合时间为2.7h,冷冻时间为14.26h。在此条件下,α-亚麻酸的含量由3.84%提高到70.01%。该生产工艺产量高、成本低、简便、易行,具有良好的工业化前景。     

Influence of pasture or grain-based diets supplemented with vitamin E on antioxidant/oxidative balance of Argentine beef

Argentine meat has been traditionally produced on pasture. However, to comply with some market requirements, grain finishing is becoming more common among producers. The main goal of the present work was to study lipid oxidation in fresh meat from animals fed different diets in relationship with their antioxidant vitamin status. Attributes were evaluated in beef from pasture or grain-fed animals with (PE and GE) or without supplementation (P and G) with vitamin E (500 UI/head/day). Fresh meat produced on grain (G and GE) had higher fat (4.0±1.6 and 4.7±1.4 g/100 g) and cholesterol content (51.0±3.0 and 52.0±4.0 mg/100 g) than meat from pasture (P and PE) fed animals (2.7±1.2 to 2.9±1.1 g/100 g and 48.0±5.0 to 49.0±4.0 mg/100 g of intramuscular fat and cholesterol respectively). Fatty acid composition was clearly affected by diet. Beef from pasture-fed cattle had higher percentage of linolenic acid, less linoleic acid and, overall, higher percentage of polyunsaturated fatty acids than beef from grain-fed animals (P<0.05). Thiobarbituric acid reactive substances number and volatile levels of hexanal, pentanal, heptanal, octanal and 3-methylbutanal were higher in grain than in pasture samples (P<0.05). P+PE meat had higher content of antioxidant vitamins than G+GE samples (P<0.001). Values ranged from: 15.92±3.48 (G) to 17.39±4.29 (GE) and 25.3±10.0 (P) to 21.98±5.11 (PE) μg/g of ascorbic acid; from 1.05±0.73 (G) to 1.76±0.97 (GE) and 3.08±0.45 to 3.91±0.74 μg/g of α-tocopherol; and from 0.06±0.03 (G) to 0.05±0.01 (GE) and 0.45±0.21 (P) to 0.63±0.27 (PE) μg/g of β-carotene. In addition, principal component analysis clearly separated grain from pasture samples regardless of their supplementation with vitamin E. This level of supplementation did not improve the antioxidant status of fresh meat (P>0.05). We conclude that pasture diet contributes natural antioxidants in sufficient amounts and is an efficient way to prevent lipid oxidation in fresh beef.     

Antioxidant Capacity and Antioxidant Content in Roots of 4 Sweetpotato Varieties

Abstract: The antioxidant contents (β-carotene, chlorogenic acid, and vitamin C) as well as the antioxidant capacity (ORAC, FRAP, and ABTS) of 4 sweetpotato varieties were measured in this study. The sweetpotato varieties were cultivated under different water regimes and also subjected to thermal processing. The results show that the 2 orange-fleshed varieties (Resisto and W-119) contain significant more β-carotene, chlorogenic acid, and vitamin C than the 2 cream-fleshed varieties (Bosbok and Ndou). Thermal processing decreased the carotenoid and vitamin C content of all the varieties but increased the chlorogenic acid content and antioxidant capacity. Drought stress appears to increase the β-carotene, vitamin C, and chlorogenic acid contents as well as the antioxidant capacity of some of the sweetpotato varieties, especially W-119.     

THE USE OF INFRA RED REFLECTANCE FOR THE RAPID ESTIMATION OF THE SOLUBLE β-GLUCAN CONTENT OF BARLEY

It has previously been reported that the malting quality of barley is related to the amount of β-glucan dissolved at low pH under defined conditions. An infra red reflectance instrument, the ‘InfraAlyzer’, can be used to estimate this ‘acid-soluble’ β-glucan content of barley. This is a rapid test (approximately one min/sample) and is therefore suitable when screening for low soluble β-glucan in the early generations of malting quality breeding programmes. The relationship between predicted and measured values for soluble β-glucan differs from comparisons made for other quality components in forages, in that it is curvilinear rather than linear. A logarithmic transformation of the soluble β-glucan values, however, allows the current ‘InfraAlyzer’, which produces linear regressions only, to predict values for soluble β-glucan that correlate well (r = 0.87) with the measured results.     

Analysis and comparison of key proteins in Maiwa yak and bovine milk using high-performance liquid chromatography mass spectrometry

Yak milk is an essential and predominant food resource for Tibetan people for subsistence purposes and to combat altitude-induced challenges. Due to its unique qualities, yak milk has recently been gaining broader attention from consumers across China as well in other parts of the world. One of the key characteristics of yak milk is the protein content, which is about 40 to 60% higher than that of native bovine milk. In this work, a sensitive and reproducible high-throughput analytical method was developed employing both ultra high-performance liquid chromatography Orbitrap (Thermo Fisher Scientific) high-resolution accurate mass spectroscopy (UHPLC-HRAM-MS) and UHPLC coupled with triple quadrupole tandem MS (UHPLC-QqQ-MS) to simultaneously analyze 8 milk proteins. A total of 15 Maiwa yak milk samples and 15 bovine milk samples were qualitatively and quantitatively analyzed using targeted proteomics and compared for α-lactalbumin, β-lactoglobulin, α_S1-casein, α_S2-casein, β-casein, κ-casein, lactoferrin, and osteopontin. Peptides of β-lactoglobulin were used to specifically distinguish yak and bovine milk. The results showed that this novel detection method could quantitatively detect these major and minor milk proteins with >0.99 linear correlation coefficient and a recovery rate between 90 and 120%, with relative standard deviations typically less than 10%. The data revealed that yak milk not only had higher overall milk protein content than bovine milk but higher lactoferrin and osteopontin contents as well. The lactoferrin content of yak milk was about 30% higher than that of bovine milk, and the osteopontin content of yak milk was nearly twice that of bovine milk. The application of this method demonstrates that UHPLC-HRAM-MS and UHPLC-QqQ-MS are suitable for high-throughput qualitative and quantitative analysis of major and minor proteins of yak and bovine milk.     

Relationship between total N, total S and the S-containing amino acids in extracted leaf protein.

The total S:total N ratio in both unfractionated and fractionated proteins extracted from the leaves of lucerne and lupin has been determined. The results were similar to those found with 80% ethanol-insoluble residues from leaves of lucerne and some other species. Methionine-S accounted for 38–43% of the total S. If methionine-S is deducted from the total S content, and the difference expressed as cystine, it appears that all preparations contained from 2.1–2.8 (as % of protein content)—more than had been previously supposed. When compared with the FAO reference protein none of the preparations are deficient in total S-containing amino acids, although the problems associated with unavailability remain. Calculating cystine by this method is not suggested as a substitute for direct determination, where this is practicable, but may be a useful approach when cyst(e)ine is present only in small amounts in a complex protein concentrate and is liable to be destroyed during acid hydrolysis.     

A Cappelle-Desprez gliadin of high mobility.

The fastest major electrophoretic component of the gliadin proteins of Cappelle–Desprez wheat has been purified sufficiently to be characterised. It appears to be a single-chain, carbohydrate-free protein, containing no SH groups and having a molecular weight of 37 000. The amino acid composition, with a preponderance of glutamine and proline, is generally typical of the gliadin class. The protein associates appreciably at acid pH.     

Isolation of a Cappelle-Desprez gliadin.

A Cappelle-Desprez gliadin, previously unreported, has been isolated. It appears to be a single-chain protein with a molecular weight of only 18 000, considerably lower than that of any other gliadin so far isolated. Its amino acid composition, though broadly typical of the class, has surprising characteristics, such as 7 Met, 7 CySSCy, but less Gln and Pro and no Lys or His. Although at acid pH the mobility is less than that of the γ-gliadin group, at pH 8.9 the molecule is still positively charged. The high isoelectric point implies that almost all the carboxyl side-chains are amidated. The gliadan contains no SH groups and does not appear to be a glycoprotein. The amino acid analysis suggests that microheterogeneity is present.     

Effect of elevated accumulation of iron in ferritin on the antioxidants content in soybean sprouts

Cultivation of soybean sprouts in abiotic stress conditions, resulted from the presence of 5–25?mM FeSO₄ in the culture media, causes a strong overexpression of ferritin. Accumulation of ferritin iron in sprouted seeds germinated in the 20?mM solution of FeSO₄ was 67 times higher than in sprouts germinated in distilled water. The cultivation conditions also influence on another antioxidant content—mainly β-carotene content, which increased 28 times (in sprouts cultured in 10?mM FeSO₄ solution) in comparison to the content in dry seeds. Obtained in stress conditions sprouted seeds contain less tocochromanoles than raw seeds. However, their total tocochromanol content was higher than in sprouted seeds cultured in distilled water in every examined concentration of Fe²⁺. A total antioxidant activity is increased only during culturing in 0–10?mM media, and it is positively correlated to the total phenolic compounds content (r?=?0.8498). We concluded that germination in high abiotic stress also causes the increase in different antioxidants content, not only in ferritin, which is directly involved in the process of iron detoxification.     

Thermodynamic approach to the selection of polyuronide sequestrants for the protection of the human body from toxic metal ions. Interactions of polyuronides with strontium and calcium ions

Selectivity of polyuronide sequestrants (pectate, alginates of various uronide composition) in respect to Sr2+ and Ca2+ ions has been evaluated in terms of thermodynamic affinity. It is suggested that there is no point in the use of pectate as a Sr(2+)-binding agent because at initial stages of reaction it reveals higher affinity to Ca2+ ions in comparison to Sr2+ ions. Contrary to pectate, alginates under similar conditions have higher affinity to Sr2+ ions. It is shown that these ions are bound only by blocks of L-guluronic acid residues in alginate macromolecules. The results obtained lend support to the advisability of the use of alginate preparations with the high content of L-guluronic acid residues for the excretion of Sr2+ ions from human body.     

Orthogonal-field-alternation gel electrophoresis banding patterns of DNA from yeasts

Chromosomal DNAs from various yeast species were separated by orthogonal-field-alternation gel electrophoresis (OFAGE). To this end we developed a spheroplasting and lysis method to obtain intact DNA from both ascomycetous and basidiomycetous yeasts. The OFAGE banding patterns of 22 ascomycetous and four basidiomycetous yeast strains were compared. The strains represented species from the genera: Brettanomyces, Candida, Cryptococcus, Filobasidiella, Geotrichum, Hansenula, Kluyveromyces, Pachysolen, Pichia, Rhodosporidium, Rhodotorula, Saccharomyces, Saccharomycodes, Saccharomycopsis, Schizosaccharomyces and Zygosaccharomyces. Variations occurred in the number of bands and their positions in the gel, not only among strains of different genera but also among species from the same genus and even between varieties of the same species. The ascomycetous yeasts, with the exception of Saccharomyces cerevisiae, only showed one to five bands of DNA larger than 1000 kilobase pairs (kb) in general none smaller. The patterns of the four basidiomycetous yeasts revealed also a few large DNA bands but in addition one to six bands ranging in size from 500 to 1000 kb, with the exception of a single smaller chromosome in Rhodotorula mucilaginosa. From the OFAGE banding patterns of strains studied here it appears that in Sacch. cerevisiae the partitioning of DNA over chromosomes is unique. But rather than the large number of chromosomes, the presence of four chromosomes with less than 500 kb of DNA is characteristic for Sacch. cerevisiae.     

A cappelle-desprez β-gliadin

A β-gliadin from Cappelle-Desprez wheat has been purified sufficiently to be analysed. Its amino acid composition is typical of the gliadin class. The molecule appears to be a single polypeptide chain with no carbohydrate or SH groups and a molecular weight of 38 000.     

苯酚-硫酸法测定β-葡聚糖含量研究

分别以β-葡聚糖和葡萄糖为标准品测定青稞提取物中β-葡聚糖含量。以β-葡聚糖为标准品时,线性浓度范围在6～13μg/mL,回归方程为y=0.0445X-0.0071,回归系数为R2=0.9568,青稞中提取β-葡聚糖粗提物纯度为22.3%(脱脂)和10.7%(未脱脂);以葡萄糖为标准品时,线性浓度范围在0-21μg/mL,回归方程为y=0.0588X+0.0326,回归系数为R2=0.9934,青稞中提取出β-葡聚糖粗提物纯度为12.5%(脱脂)和4%(未脱脂),二者之间测定结果有78.4%左右误差。在β-葡聚糖含量测定过程中不能用葡萄糖代替β-葡聚糖作标准品,用β-葡聚糖作标准品时苯酚-硫酸法工作曲线线性回归性不强,直接用苯酚-硫酸法测定β-葡聚糖方法不可取。