Comparative studies on protein fractions and amino acid composition from sorghum and pearl millet

A defatted flour sample of sorghum and pearl millet were separated into three fractions. These procedures involve extracting the defatted flour with aqueous sodium hydroxide (pH 11.9) followed by precipitation with diluted HCl acid (pH 4.8). The two protein fractions I (soluble at pH 4.8) and II (insoluble at pH 4.8) along with the remaining residues (fraction III) were lyophilized separately. The amino acid composition of the original flour and the three fractions were determined. Lysine seems to be the most deficient amino acid in the original flour and the remaining residues. Fraction I and II, in which the lysine accumulated, have essentially better amino acid profile and consequently nutritionally better quality than the protein of the original defatted flour. The recovered protein-rich fractions I and II should be useful as a protein ingredient in foods. The remaining residues can be extruded into convenience foods.     

子营养成分及功能利用研究进展

穇子是一种非常重要的作物,含有丰富的营养物质及较高的膳食纤维、多酚、矿物质和含硫氨基酸。穇子有抗氧化与抗衰老、抗癌、预防糖尿病、保护心脏和抗高血脂等生理功能。在国外,穇子除了被加工成穇子粉、穇子饼、穇子球等传统食品外,还被制成穇子麦芽和发酵食品等。然而,我国对穇子的研究非常少,关于穇子的产品也不多,严重制约我国穇子产业的发展。本文将从穇子的营养成分、生理功能及加工利用这三个方面进行综述,以期待给我国穇子的加工者和研究者提供一定的借鉴。      

谷子油的理化性质及脂肪酸组成分析

对谷子的基本组成和谷子油的理化性质及脂肪酸组成进行了分析。结果表明,谷子中粗蛋白质、粗脂肪、总糖和淀粉含量分别为13.9%、5.6%、66.5%和63.7%。谷子油的酸值(KOH)为11.9 mg/g,碘值(I)为132.9 g/100 g,过氧化值为30.9 mmol/kg,皂化值(KOH)为194.4 mg/g,不皂化物含量为2.73%。谷子油主要由10种脂肪酸组成,其中饱和脂肪酸含量占16.81%,主要为棕榈酸(7.87%)、硬脂酸(6.17%)和花生酸(2.03%);不饱和脂肪酸含量达83.26%,其中以亚油酸含量(65.30%)最高,其次为油酸(14.20%)和亚麻酸(2.93%)。因此,谷子油是一种极具开发价值的营养保健油脂。     

Changes in carbohydrates, proteins and lipids of finger millet after hydrothermal processing

Finger millet was soaked, steamed and dried to prepare hydrothermally processed millet, followed by decortication to prepare decorticated millet. The physicochemical properties and carbohydrate, protein and lipid profiles of control and processed millet were determined. The carbohydrates were fractionated to amlypectin and amylose equivalent fractions using gel permeation chromatography. The non-starch polysaccharides were isolated and their alditol acetyl derivatives were characterized by gas chromatography (GC). The proteins were extracted using different solvents and the total proteins were fractionated using SDS-PAGE. The ether extractable lipids were esterified and fractionated through GC. Hydrothermal processing decreased the amylopectin fraction and increased the amylose equivalent portion of the starch. Decortication further lowered the first fraction and increased the second fraction. A decrease in cold, hot water soluble and hemicellulose-B fractions and an increase in pectic polysaccharides, hemicellulose-A and cellulosic fractions were observed as a result of hydrothermal processing. Decortication significantly reduced the total non-starch polysaccharides specifically the cellulose fraction. Hydrothermal processing decreased the overall extractability of proteins by 50% but decortication increased it to 80%. It was observed that hydrothermal treatment did not change the gross nutrients composition of finger millet but for their profile. Decortication of hydrothermally processed millet caused significant changes in the nutrient contents and also in their profiles.     

Fractional and amino acid composition of krill proteins and the potential for obtaining protein preparations

Studies of the fractional composition of krill proteins demonstrated that the content of protein fractions changes depending on the time of krill catch. The highest amount of water-soluble proteins is contained by krill caught in December (64%), of salt-soluble by krill caught in June (12%), base-soluble by krill caught in May, September and February (34%). Krill protein contains from 50 to 60% of water- and salt-soluble fractions. Analysis of the amino acid composition of krill proteins showed that it does not differ essentially from that of adequate food proteins.     

Non-covalent binding of proteins to polyphenols correlates with their amino acid sequence

The present paper describes the assessment of non-covalent binding (NCB) between milk proteins and polyphenols and its correlation with the physicochemical parameters of proteins. A method based on ultrafiltration and liquid chromatography-tandem mass spectrometry was used to analyse free and non-covalently bound polyphenols (ligands) in mixtures with major milk proteins. Binding strength values of individual polyphenols were normalised to those obtained with quercitrin (quercetin-3-O-rhamnoside), used as a reference compound. NCB data acquired by experiments at pH 6.6 without any preliminary protein denaturation were correlated with the physicochemical parameters of ligands and proteins. Unsupervised multivariate analysis revealed that NCB of proteins clustered according to their family (caseins separated from albumins). Based on this model, a predictive relationship was observed between protein-polyphenol binding strength and primary/secondary structure parameters of the proteins e.g. number of charges, proline residues and extended strand. These results confirm that, under the investigated experimental conditions, the NCB between polyphenols and protein mixtures can be predicted and optimised based on the molecular structures.     

大豆7S和11S蛋白中氨基酸组成与表面疏水性的相关性研究

以6个具有代表性的大豆品种为实验材料提取7S和11S蛋白,经Superdex 200凝胶柱层析纯化制得纯品7S和11S蛋白,用SDS-PAGE和蛋白质纯化仪凝胶柱层析两种方法验证其纯度在90%以上。研究了7S和11S蛋白中氨基酸组成与表面疏水性的相关性。结果表明:7S和11S蛋白的表面疏水性与甘氨酸、脯氨酸、胱氨酸/半胱氨酸、丙氨酸、缬氨酸、蛋氨酸、酪氨酸、天冬氨酸、苏氨酸、组氨酸的含量呈正相关;与异亮氨酸、亮氨酸、苯丙氨酸、丝氨酸、赖氨酸的含量呈负相关;与谷氨酸和精氨酸的含量不相关。疏水性氨基酸总量与7S和11S蛋白的表面疏水性呈正相关,亲水性氨基酸总量与其表面疏水性不相关。     

Relationships between amino acid composition and nitrogen of foxtail (Italian) millet (Setaria italica) grain of different varieties

The amino acid composition of 13 samples of foxtail millet (Setaria italica L) from six Chinese and one French varieties was determined as a function of their N content (N), which ranged from 1·82 to 3·65 g per 100 g of grain DM. The levels of amino acids in grain DM increased linearly with N with correlation coefficients close to 1 for most of them regardless of foxtail millet genotype or phenotype. Thus simply knowing N enables one to predict the amino acid composition of any foxtail millet grain sample. Amino acids in crude protein of grain (g 16 g^?1N)changed as quadratic functions of N, which decreased for glycine, cysteine, tysine, histidine and arginine, remained nearly constant for valine, threonine, tyrosine, methionine and aspartate plus asparagine, and increased for other amino acids. Foxtail millet appeared as the only cereal in which lysine is the only limiting essential amino acid. However, the lysine score was low and intermediate between that of maize and sorghum, falling from 48 to 31 % when N increased from 1·82 to 3·65 g per WO g DM. The N-to-protein conversion factor strongly increased with N and was the highest of all cereals within the N range studied. The results also showed that the composition of storage proteins accumulated in grains remained constant, with a prolamin to glutelin ratio close to three and independent of grain protein content.     

12个品种小米氨基酸含量测定及品质综合评价

目的:为小米的种质资源鉴定与筛选、品质育种及综合加工利用提供依据。方法:以12个小米品种为研究对象,测定小米中的氨基酸含量,并以小米中所含的17种氨基酸含量作为评价指标,进行主成分分析和品质综合评价,同时对小米品种进行聚类分析。结果:小米品种对17种氨基酸含量的影响顺序为Ser>Lys>Arg>His>Met>Ile>Thr>Gly>Pro>Tyr>Phe>Asp>Cys>Glu>Leu>Val>Ala。主成分分析可提取出2个主成分,累计方差贡献率达到88.329%,Glu、Pro、Leu、Phe、Ile、Lys、Thr、His和Tyr可以作为小米品种的综合评价指标。通过隶属函数法评价出了12个小米品种的品质优劣顺序,聚类分析可以将12个小米品种划分为三大类。结论:晋谷61的综合品质最好,张杂谷13品质最差。     

Mode of inhibition of finger millet malt amylases by the millet phenolics

The effect of millet polyphenols on starch hydrolysis catalyzed by amylases developed during malting were investigated. The enzyme kinetic studies using Michaelis–Menten and Lineweaver–Burk equations showed the K_m remained constant (0.625%) but the maximum velocity (V_max) decreased in the presence of a crude extract of millet polyphenols, indicating mixed non-competitive inhibition. On the other hand, gallic acid, vanillic acid, quercetin and trans-cinnamic acid isolated from the polyphenol extract of the millet showed uncompetitive inhibition. Kinetic studies of amylase inhibition by phenolic compounds indicated the presence of secondary binding sites in malted finger millet amylases similar to other cereal amylases.     

西门塔尔牛乳成分及氨基酸组成分析

选用长春地区的西门塔尔奶牛36头、通辽地区的西门塔尔牛27头和松原地区的西门塔尔奶牛17为研究对象,测定其常规乳成分及乳蛋白中的氨基酸组成,并对不同泌乳期、不同季节、不同胎次等条件下的常规乳成分及氨基酸组成进行了分析。结果表明,胎次、泌乳期、饲养方式和季节因素对西门塔尔牛的常规乳成分和氨基酸组成都有不同程度影响。     

Effect of fluorescent light on amino acid composition of serum proteins from homogenized milk.

The serum proteins isolated from homegenized milk by centrifugation and exposed to 2152lx of fluorescent light for 72 h were fractionated into the major protein components by gel filtration chromatography. Amino acid composition of the major serum proteins, beta-lactoglobulin and alpha-lactalbumin which accounted for 80% of the total serum protein, did not change substantially following light exposure. Changes in amino acid composition associated with fluorescent light exposure occurred primarily in the high molecular weight fraction of serum proteins. This fraction amounts to at most 10% of the serum proteins.     

凤窝酒曲酵母菌多样性及其分离株发酵红枣酒氨基酸组成分析

采用野生蓝靛果（Lonicera caerulea）纯化得到花青素,以生长曲线、抑菌圈直径、最小抑菌浓度为评价指标,研究其对嗜热链球菌（Streptococcus thermophilus）、保加利亚乳杆菌（Lactobacillus bulgaricus）生长的影响,分析其抑菌效果、抑菌机理及保质期21 d内酸度、pH值、还原糖的变化。结果表明,添加花青素组能抑制菌株生长;花青素对两种乳酸菌及其混合菌有一定的抑制作用,对嗜热链球菌、混合菌（1∶1）及保加利亚乳杆菌的最小抑菌浓度分别为62.5 μg/mL、62.5 μg/mL、31.25 μg/mL;加热预处理、培养基pH以及糖浓度对花青素的抑菌作用产生影响。花青素对乳酸菌的抑菌作用机理是其改变细胞膜通透性、损伤菌体蛋白引起菌体蛋白的泄露。0.32%花青素添加量可抑制酸奶后酸化作用。     

Gross and true ileal digestible amino acid contents of several animal body proteins and their hydrolysates

Amino acid compositions of ovine muscle, ovine myofibrillar protein, ovine spleen, ovine liver, bovine blood plasma, bovine blood globulins and bovine serum albumin and the amino acid compositions and in vivo (laboratory rat) true ileal amino acid digestibilities of hydrolysates (sequential hydrolysis with Neutrase, Alcalase and Flavourzyme) of these protein sources were determined. True ileal amino acid digestibility differed (P < 0.05) among the seven protein hydrolysates. The ovine myofibrillar protein and liver hydrolysates were the most digestible, with a mean true ileal digestibility across all amino acids of 99%. The least digestible protein hydrolysate was bovine serum albumin with a comparable mean true ileal digestibility of 93%. When the digestible amino acid contents were expressed as proportions relative to lysine, considerable differences, across the diverse protein sources, were found in the pattern of predicted absorbed amino acids.     

Gross composition,amino acid,phytic acid and trace element contents of thirteen cowpea cultivars and their nutritional significance

Thirteen cultivars of cowpea (Vigna unguiculata (L) Walp) were analysed for their proximate composition, amino acid, trace element and phytic acid contents. Crude protein values ranged from 206·8 to 283·8 g kg^?1 DM. The mean contents (g kg^?1) of other major nutrients were ether extract, 18·6; ash, 38·8; total dietary fibre, 121·8 and carbohydrates, 573·4. When compared with the provisional amino acid scoring pattern of FAO, all cultivars were low in methionine and high in lysine, isoleucine, leucine and phenylalanine plus tyrosine. Values for threonine and valine were variable compared with the pattern. The range of values for the chemical score was 0·61–0·74. Phytic acid values ranged from 5·10 to 10·27 g kg^?1, and the phytate: zinc molar ratios were all higher than that (15:1) above which zinc deficiency can be induced. Most of the trace elements showed wide variation in their occurrence among the cultivars. The values for zinc and iron showed less variation. The toxic elements mercury and selenium were present in varying amounts in more than half of the cultivars while tin was found in only one variety.     

Molecular weight and amino acid composition of glycinin subunits

Glycinin, the major soyabean globulin, is composed of subunits having molecular weights of about 22,300, and 37,200. On the basis of amino acid analysis, the six submits of glycinin isolated by isoelectric focusing are all different. The ‘acidic’ subunits have higher content of glutamic acid and proline, whereas the ‘basic’ subunits are higher in the hydrophobic amino acids leucine, tyrosine, phenylalanine, valine and alanine.