Fermentation modifies protein/protein and protein/starch interactions in sorghum dough

A study was made on the molecular and structural changes occurring in the protein and starch components of sorghum flour when fermented to prepare typical non-malted Sudanese foods. Protein solubility and SDS-PAGE studies indicated that water-soluble proteins are the main target of hydrolysis during fermentation. Proteolysis products are taken up for bacterial growth. Kafirins are among the proteins left intact by proteolytic events in the fermentation step. Upon cooking in boiling water kafirins are converted into protein aggregates almost insoluble even in the presence of 8 M urea and of disulphide-reducing agents. Viscoamylographic and microstructural studies indicate that fermentation leads to the release of starch granules from very compact structures in the original sorghum flour, in which proteolysis-sensitive, water-soluble proteins form an essential part of the outermost shell of large structures, where starch granules are embedded into a kafirin-rich protein matrix that is not affected by proteolytic events during fermentation.     

Labile protein reserves and protein turnover.

The concept of a labile protein reserve is based on the relatively slow establishment of a new equilibrium in the rate of nitrogen excretion after an abrupt change in dietary supply. The evidence reviewed shows that a majority of this nitrogen is derived from or deposited in skeletal muscle proteins. The rates of synthesis and degradation of total body protein are rapid in large animals (man and swine) and are correlated with heat production. The rate of protein synthesis in skeletal muscle greatly exceeds the rate of growth and is sensitive to nutritional status. The rate exceeds the rate of degradation in response to the ingestion of an adequate diet so that tissue proteins are accumulated, but it decreases below the rate of degradation under conditions of deprivation. In this latter state, proteins of skeletal muscle supply amino acids for energy or for the synthesis of other more essential proteins, e.g., milk proteins during lactation. Thus, we conclude that the labile protein reserve is a product of the normal, dynamic metabolism of protein.     

肌原纤维蛋白双蛋白乳饮料的研制

介绍了肌原纤维蛋白双蛋白乳饮料生产所需的材料、设备、工艺流程、操作要点、质量指标,确定了产品所需肌原纤维蛋白的种类、甜味剂的种类、乳化稳定剂的添加量,通过正交试验和极差分析得出肌原纤维蛋白双蛋白乳饮料的较优配方为:全脂乳粉3.5%、肌原纤维蛋白0.3%、复合甜味剂(以蔗糖计)9%、酸含量(以柠檬酸计)0.4%、复合乳化稳定剂0.40%、柠檬酸钠0.1%、食用香精0.03%。     

Perspectives of lupine wholemeal protein and protein isolates biodegradation

Lupine (Lupinus angustifolius L.) protein (in wholemeal and protein isolates) was biodegraded using Pediococcus acidilactici in submerged and solid-state fermentation conditions. The changes in the molecular weight of lupine protein fractions, amino acid (AA) profile, biogenic amine formation, antimicrobial and antioxidant properties, and protein digestibility in vitro and in vivo (in Wistar rats) were evaluated. After biotreatment, lower molecular weight peptides (from 10 to 20 kDa) were established, and the free AA content increased. Biodegradation improved the antioxidant properties, modulated the antimicrobial properties, and led to higher in vitro and in vivo digestibility and functionality of the lupine in treated rats (significant increase in body weight of Wistar rats, and increased acetic acid concentration and lowered Escherichia coli count in the caecum). Overall, the biodegradation of lupine protein can transform the plant protein, producing enhanced functionality and bioavailable products.     

Oil globule microstructure of protein/polysaccharide or protein/protein bilayer emulsions at various pH

The microstructure of oil droplets of bi-layer emulsions was studied as a function of pH (i.e. 7, 5, and 3) using scanning electron microscopy. The bi-layer emulsions consisted of a primary emulsion: 5 wt% soybean oil (SBO) in a 1% protein (nonfat dry milk) aqueous solution. The secondary layer was ι-carrageenan, high- (HMp), low (LMp)-methoxyl pectin, or gelatin. The secondary emulsions consisted of 2.5% SBO, 0.5% protein, and 0.2% polysaccharide or protein. Gelatin secondary emulsions were stable at pH 7 with defined droplets and became unstable at pH 5 and 3. The destabilization mechanisms for these emulsions at pH 5 and 3 were different as observed with the SEM: at pH 5 there is complete aggregation of protein due to their proximity to the isoelectric point; and at pH 3 the droplets are perfectly separated, suggesting that at this pH, when the net charge is positive, the destabilization is mainly due to depletion flocculation. HMp secondary emulsions shift from being stable (individual droplets) at pH 3 to being unstable at pH 7 where an extensive webbing is observed between the droplets at this pH value. The ι-carrageenan secondary emulsions are stable at each pH and the individual droplet microstructure is minimally altered as the pH changes. LMp secondary emulsions shift from being stable at pH 7 with individual droplets observed in the SEM micrographs to being unstable at pH 3 where extensive webbing is observed in the SEM micrographs.     

Nutritive value of a new protein product--dry protein mixture

A dry protein mixture (DPM) consists of dry slaughtered animal blood clarified by means of the peroxide-catalase system and dry skim milk at a ratio of 1:1. A study was made of organoleptic properties of the DPM, the composition of nutrients and biological efficacy in experiments on animals. The DPM is light yellow powder without specific taste and odor of blood, contains 58.4% of protein, 1.36% of fat, 26.71% of carbohydrates (lactose), and 8.19% of mineral substances. DPM proteins contain all the essential amino acids. As regards their biological efficacy they are not inferior to that of casein. The DPM is rich in calcium (606 mg/100 ml), phosphorus (645 mg/100 ml) and particularly in iron (106 mg/100 ml). Digestibility of iron examined on rats appeared to be high (31.2%). The new product is recommended for rational and dietetic nutrition.     

一种再生蛋白纤维--大豆蛋白纤维

主要介绍了大豆蛋白纤维的发展概况、生产工艺与设备、产品及其织物特点,从而为大豆纤维在纺织工业的应用提供技术和理论指导,同时也为纺织产品的创新开辟新的途径.     

大豆分离蛋白中蛋白质含量的快速测定

采用基于经典凯氏定氮法原理设计的KDN-08A半自动定氮仪对大豆分离蛋白中蛋白质含量进行快速测定.结果经t检验,与经典凯氏定氮法测得结果无显著性差异,且回收率在99.53%～100.19%之间.表明该方法测定结果准确可靠、操作简单快速,适用于大豆分离蛋白中蛋白质含量的测定.     

富锌豆蛋白中锌结合态含量的研究

富锌豆蛋白是一种用特殊科学方法得到的高含量锌添加剂。本文利用植物生化分离和分析方法,研究了富锌豆蛋白中锌与不同蛋白结合状态下的含量。分析结果显示,游离锌为150.7μg/g,结合于蛋白中的锌为1055.0μg/g。可以认为锌主要以有机蛋白锌的形式存在。     

Solubility of commercial milk protein concentrates and milk protein isolates

High-protein milk protein concentrate (MPC) and milk protein isolate (MPI) powders may have lower solubility than low-protein MPC powders, but information is limited on MPC solubility. Our objectives in this study were to (1) characterize the solubility of commercially available powder types with differing protein contents such as MPC40, MPC80, and MPI obtained from various manufacturers (sources), and (2) determine if such differences could be associated with differences in mineral, protein composition, and conformational changes of the powders. To examine possible predictors of solubility as measured by percent suspension stability (%SS), mineral analysis, Fourier transform infrared (FTIR) spectroscopy, and quantitative protein analysis by HPLC was performed. After accounting for overall differences between powder types, %SS was found to be strongly associated with the calcium, magnesium, phosphorus, and sodium content of the powders. The FTIR score plots were in agreement with %SS results. A principal component analysis of FTIR spectra clustered the highly soluble MPC40 separately from the rest of samples. Furthermore, 2 highly soluble MPI samples were clustered separately from the rest of the MPC80 and MPI samples. We found that the 900 to 1,200 cm⁻¹ region exhibited the highest discriminating power, with dominant bands at 1,173 and 968 cm⁻¹, associated with phosphate vibrations. The 2 highly soluble MPI powders were observed to have lower κ-casein and α-_S1-casein contents and slightly higher whey protein contents than the other powders. The differences in the solubility of MPC and MPI were associated with a difference in mineral composition, which may be attributed to differences in processing conditions. Additional studies on the role of minerals composition on MPC80 solubility are warranted. Such a study would provide a greater understanding of factors associated with differences in solubility and can provide insight on methods to improve solubility of high-protein milk protein concentrates.     

Personalizing protein nourishment

Proteins are not equally digestible—their proteolytic susceptibility varies by their source and processing method. Incomplete digestion increases colonic microbial protein fermentation (putrefaction), which produces toxic metabolites that can induce inflammation in vitro and have been associated with inflammation in vivo. Individual humans differ in protein digestive capacity based on phenotypes, particularly disease states. To avoid putrefaction-induced intestinal inflammation, protein sources, and processing methods must be tailored to the consumer's digestive capacity. This review explores how food processing techniques alter protein digestibility and examines how physiological conditions alter digestive capacity. Possible solutions to improving digestive function or matching low digestive capacity with more digestible protein sources are explored. Beyond the ileal digestibility measurements of protein digestibility, less invasive, quicker and cheaper techniques for monitoring the extent of protein digestion and fermentation are needed to personalize protein nourishment. Biomarkers of protein digestive capacity and efficiency can be identified with the toolsets of peptidomics, metabolomics, microbial sequencing and multiplexed protein analysis of fecal and urine samples. By monitoring individual protein digestive function, the protein component of diets can be tailored via protein source and processing selection to match individual needs to minimize colonic putrefaction and, thus, optimize gut health.     

Polysaccharide protein interactions

The interaction between proteins and polysaccharides, as can be observed in food related systems, is systematically discussed by separating biopolymer interactions into respectively enthalpy- and entropy-dominated types. We present examples of typically enthalpy driven phase separations, such as biopolymer incompatibility, described by the classical Flory-Huggins theory. This behavior is for instance observed for the system gelatin–dextran. In mixed systems where excluded volume or depletion interaction plays an important role the phase separation is mainly driven by entropy. Here the interaction of (random coil) polysaccharides and protein (covered) particles such as casein micelles and emulsion droplets in dairy systems may lead to phase separation as well.     

Mechanism for maintaining blood protein composition with various protein regimens

The study of the blood plasma protein content, turnover constant and half-life of albumin, fibrinogen and the total fraction of IgG + transferrin, was conducted in 70 male Wistar rats which received rations containing 4, 8, 12, 18 and 36% protein (casein), during a month. The total serum protein content and the proteins assayed in the blood plasma were not reliably changed in relation to the protein level in the animals' ration. It was found that the half-life of the proteins studied increased with the lowering of the protein content in the ration. It is suggested that the increase of the blood plasma protein half-life is one of the mechanisms of maintaining stable blood plasma protein composition in case of insufficient protein content in the food ration.     

Nucleic acid and protein metabolism in undernutrition and protein deficiency

This review discusses the metabolism of nucleic acids and proteins in various models of undernutrition in female rats and their neonatal and 21-day-old progeny. Based on the observations noted in our laboratories and those of other investigators, it is concluded that body and organ weights as well as various parameters of cellular growth (DNA, RNA, proteins, amino acids and total nucleotides) fail to increase normally in dietary-insulted animals. Protein and RNA synthesis demonstrate variable responses, leading to the speculation that modulation of mRNA metabolism and of protein synthesis occurs in dietary-restricted rats. These findings are also confirmed by the organ weight to DNA ratios. It is further noted that, despite the increases in protein and RNA synthesis in certain organs, protein and RNA register below-normal values, indicating that their degradation is much faster than their formation. This postulate is supported: by the enhanced activities of acid cathepsin (a protein-degrading enzyme) and of RNAse A (a RNA-degrading enzyme); by the elevated concentrations of circulating amino acids and total nucleotides; as well as by the accelerated excretion of nitrogenous compounds in the urine and feces of dietary-restricted animals. Modifications of RNA turnover are also evident in the tRNA and soluble RNA fractions of the liver of dietary-insulted rats. Studies on brain mRNA translatability have revealed: that food deprivation elicits a shorter species of pre-mRNA via a reduced polynucleotide elongation rate; that not all poly A+ RNA sequences present in control rats occur in dietary-restricted animals; and that the translatability of polymerase II is far lower in dietary-insulted rats. Other investigations on the translatability of liver, brain, kidney, spleen and thymus mRNA have demonstrated changes in mRNA via altered protein synthesis in various organs of dietary-restricted rats. Generation studies have shown that adaptation prevails in the first, second and third generation offspring of dietary-insulted rats, after which all parameters decline in fourth and fifth generation offspring. By reducing the litter size and exchanging the pups of control and dietary-restricted rats during the lactation period, partial restoration of the cellular growth of different organs is effected with the exception of the brain, in which damage is irreversible.     

双缩脲法检测大豆分离蛋白中蛋白质的研究

采用双缩脲法检测大豆分离蛋白中蛋白质的含量,当蛋白质含量在0～12.0mg范围内时,线性关系比较好,变异系数小,重复性好.与凯氏定氮法比较,二者差异不显著.双缩脲法操作简单,对环境无污染,是一种非常有前途的测定大豆蛋白质的方法.     

罗汉果蛋白酶水解大豆蛋白研究

研究了采用罗汉果蛋白酶水解大豆分离蛋白制备大豆肽的水解工艺;分析了温度、pH、底物浓度、酶与底物比(质量百分比)和时间对酶水解的影响;得到了罗汉果蛋白酶水解大豆分离蛋白的最佳水解工艺为温度60℃、pH9.0、底物浓度5.0%、酶与底物比5.0%、水解时间1h。     

营养健康的植物蛋白饮料

<正> 目前,以豆奶为主的植物蛋白饮料,因其营养丰富、风味优良、销售饮用方便等特点,已在现代化饮料工业中成为一支独秀。尤其在日本、东南亚等地发展更为迅速。近年来,我国植物蛋白饮料发展也很快,而且在这方面我国的资源相当丰富,因此,重点发展植物蛋白饮料是符合我国国情的多快好省之举。 植物蛋白饮料的营养效用 植物蛋白饮料的主要原料为植物核果类及油料植物的种籽。这些籽仁含有大量脂肪、蛋白质、维生素、矿物质     

Effect of protein concentration and protein source on the degradability of dry matter and protein in situ

Degradability of DM and CP was determined in situ for barley, canola meal, corn gluten meal, barley silage, and four concentrate mixtures. Crude protein percent of concentrate mixtures 1 to 4, respectively, were barley plus canola 1, 15.1; barley plus canola 2, 21.0; barley plus corn gluten 1, 17.1; and barley plus corn gluten 2, 19.6. Degradability of each feedstuff was measured on each of four basal diets consisting of barley silage and one of the above concentrate mixtures fed in the proportion 40:60 (DM). The resulting CP percent of diets containing concentrates 1 to 4 were 12.3, 16.1, 13.8, and 16.4. Effective degradability for DM and CP, assuming a rumen outflow rate of .08 h-1, were: barley 77.7 and 79.8; canola meal 60.9 and 66.6; corn gluten meal 18.9 and 11.0; barley silage 47.0 and 81.1; barley plus canola 1, 76.4 and 77.4; barley plus canola 2, 72.5 and 71.8; barley plus corn gluten 1, 72.8 and 55.8; barley plus corn gluten 2, 70.2 and 47.4. With two exceptions (DM degradability of concentrate 4 and CP degradability of concentrate 2), basal diet had no significant effect on effective CP or effective DM degradability. Crude protein degradability of concentrate mixtures 1 to 4, respectively, as measured (77.4, 71.8, 55.8, and 47.4) was similar to degradability estimated on the basis of their ingredient content (75.7, 72.1, 49.6, and 43.0).