Effect of enzymatic treatment of extracted sunflower proteins on solubility, amino acid composition, and surface activity

Industrial proteins from agriculture of either animal or vegetable origin, including their peptide derivatives, are of great importance, from the qualitative and quantitative point of view, in food formulations (emulsions and foams). A fundamental understanding of the physical, chemical, and functional properties of these proteins is essential if the performance of proteins in foods is to be improved and if underutilized proteins, such as plant proteins (and their hydrolysates and peptides derivatives), are to be increasingly used in traditional and new processed food products (safe, high-quality, health foods with good nutritional value). In this contribution we have determined the main physicochemical characteristics (solubility, composition, and analysis of amino acids) of a sunflower protein isolate (SPI) and its hydrolysates with low (5.62%), medium (23.5%), and high (46.3%) degrees of hydrolysis. The hydrolysates were obtained by enzymatic treatment with Alcalase 2.4 L for DH 5.62 and 23.5% and with Alcalase 2.4 L and Flavorzyme 1000 MG sequentially for DH 46.3%. The protein concentration dependence on surface pressure (surface pressure isotherm), a measure of the surface activity of the products (SPI and its hydrolysates), was obtained by tensiometry. We have observed that the degree of hydrolysis has an effect on solubility, composition, and content of the amino acids of the SPI and its hydrolysates. The superficial activity and the adsorption efficiency were also affected by the degree of hydrolysis.     

高压处理对牛乳清蛋白体外消化性的影响

为了评价牛乳清蛋白(WPI)加压凝胶的消化性,使用未加压WPI及加压(200～600MPa)WPI凝胶进行了体外模拟胃蛋白酶-胰蛋白酶消化率的测定,并用十二烷基磺酸钠-聚丙烯酰胺(SDS-PAGE)电泳的方法分析了不同压力对WPI构成蛋白消化性的影响。结果表明,经过胃蛋白酶和胰蛋白酶的消化后,加压WPI凝胶消化率显著高于未加压WPI,分别为72.59%和61.02%;400MPa以上加压处理后,加压WPI凝胶消化率未见有明显的变化(p<0.05)。尽管未加压WPI中β-乳球蛋白不易被胃蛋白酶消化,400MPa加压WPI凝胶中的β-乳球蛋白则能被胃蛋白酶部分消化,而600MPa加压后β-乳球蛋白几乎被完全消化。此外,在胃蛋白酶消化阶段,有3500～6500u范围的多肽产物生成。     

Barley grain constituents, starch composition, and structure affect starch in vitro enzymatic hydrolysis

The relationship between starch physical properties and enzymatic hydrolysis was determined using ten different hulless barley genotypes with variable carbohydrate composition. The ten barley genotypes included one normal starch (CDC McGwire), three increased amylose starches (SH99250, SH99073, and SB94893), and six waxy starches (CDC Alamo, CDC Fibar, CDC Candle, Waxy Betzes, CDC Rattan, and SB94912). Total starch concentration positively influenced thousand grain weight (TGW) (r(2) = 0.70, p < 0.05). Increase in grain protein concentration was not only related to total starch concentration (r(2) = -0.80, p < 0.01) but also affected enzymatic hydrolysis of pure starch (r(2) = -0.67, p < 0.01). However, an increase in amylopectin unit chain length between DP 12-18 (F-II) was detrimental to starch concentration (r(2) = 0.46, p < 0.01). Amylose concentration influenced granule size distribution with increased amylose genotypes showing highly reduced volume percentage of very small C-granules (<5 μm diameter) and significantly increased (r(2) = 0.83, p < 0.01) medium sized B granules (5-15 μm diameter). Amylose affected smaller (F-I) and larger (F-III) amylopectin chains in opposite ways. Increased amylose concentration positively influenced the F-III (DP 19-36) fraction of longer DP amylopectin chains (DP 19-36) which was associated with resistant starch (RS) in meal and pure starch samples. The rate of starch hydrolysis was high in pure starch samples as compared to meal samples. Enzymatic hydrolysis rate both in meal and pure starch samples followed the order waxy > normal > increased amylose. Rapidly digestible starch (RDS) increased with a decrease in amylose concentration. Atomic force microscopy (AFM) analysis revealed a higher polydispersity index of amylose in CDC McGwire and increased amylose genotypes which could contribute to their reduced enzymatic hydrolysis, compared to waxy starch genotypes. Increased β-glucan and dietary fiber concentration also reduced the enzymatic hydrolysis of meal samples. An average linkage cluster analysis dendrogram revealed that variation in amylose concentration significantly (p < 0.01) influenced resistant starch concentration in meal and pure starch samples. RS is also associated with B-type granules (5-15 μm) and the amylopectin F-III (19-36 DP) fraction. In conclusion, the results suggest that barley genotype SH99250 with less decrease in grain weight in comparison to that of other increased amylose genotypes (SH99073 and SH94893) could be a promising genotype to develop cultivars with increased amylose grain starch without compromising grain weight and yield.     

蒸汽爆破处理对麦麸的酚酸组成及其抗氧化活性的影响

该试验旨在研究蒸汽爆破处理对小麦麸皮的酚酸组成及抗氧化活性的影响.将麦麸在不同处理压力(0.5,1.5,2.5 MPa)和不同处理时间(30,90 s)条件下进行蒸汽爆破预处理.通过水解和碱提的方法,将得到的麦麸进行提取,得到游离酚酸和结合酚酸2部分,对其中的几种主要酚酸,如香草酸、丁香酸,4-香豆酸,阿魏酸进行研究.结果表明,4种主要酚酸的含量在蒸汽爆破处理后均有所提高,其中阿魏酸的含量最高,结合酚酸中由未处理时的57.232μg/g提高到了1454.092 μg/g.该试验还进行了总酚测定,抗氧化活性的测定.通过总酚的测定可以看出,蒸汽爆破处理后,总酚的含量高于未处理麦麸,且随着处理强度的增加,呈现先增加后减少的趋势,在处理条件为2.5 MPa,30 s,总酚含量最高,约为未处理时的9倍.抗氧化试验得到的变化趋势与总酚呈现相似的规律,与未进行蒸汽爆破预处理的麦麸相比,处理后的麦麸表现出了更高的1,1-二苯基-2-三硝基苯肼(DPPH)和2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(ABTS)自由基清除率,以及在亚油酸体系中的抗氧化活性和还原能力.当处理条件为2.5 MPa,30 s时,抗氧化活性表现最高.由此可得到,2.5 MPa 30s是蒸汽爆破处理麦麸的最佳条件,此时麦麸中酚酸含量和抗氧化活性均较优,为以后麦麸中酚类物质的深度开发利用提供理论支持.     

Effect of a new thermal treatment in combination with saprobic fungal incubation on the phytotoxicity level of alperujo

Byproducts generated from food industries, such as olive oil mills, have been studied to decrease harmful pollution and their environmental consequences. In this work, a new thermal pretreatment and saprobic fungal incubation to detoxify alperujo (two-phase olive mill waste) have been evaluated in view of its use as fertilizer in agriculture. The sequential use of both methods simplifies the thermal conditions and incubation times of the fungal treatment. Optimization of the thermal treatment from 150 to 170 °C for 45 and 15 min, respectively, reduced the incubation time with Coriolpsis rigida from 20 to 10 weeks needed to reduce phytotoxic effects on tomato plants. Therefore, the combination of thermal and biological treatments will allow the development of the potential benefits of alperujo to improve nutrients in agricultural soil.     

Chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses by dogs to select corn fibers

The objective was to examine the chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses of fiber-rich corn coproducts resulting from corn wet milling. Native corn fibers, native corn fibers with fines, hydrolyzed corn fibers, and hydrolyzed extracted corn fibers were analyzed chemically and their capacity to produce short-chain fatty acids determined. Ash content was low (<1.2%), crude protein content varied little, but fat and fiber concentrations varied widely. Most fiber was in the insoluble form, with glucose being predominant followed by xylose. Total short-chain fatty acid production ranged from 211.6 to 699.52 micromol/g of dry matter, whereas branched-chain fatty acid production was low. Four corn fibers (native and processed) were included in a canine diet matrix at the 7% inclusion level. Nutrient digestibility, food intake, and fecal characteristics were not affected by corn fiber inclusion in canine diets, suggesting that they should be considered as potential dietary fiber sources in dog foods.     

Effect of oxidation on in vitro digestibility of skeletal muscle myofibrillar proteins

The objective of this study was to investigate the effect of chemical oxidation on myofibrillar protein digestibility. Myofibrils were prepared from pig M. longissimus dorsi and oxidized by a hydroxyl radical generating system. Oxidative modifications of proteins were assessed by the carbonyl content, surface hydrophobicity, electrophoresis, and immunoblotting. Oxidized or nonoxidized myofibrillar proteins were then exposed to proteases of the digestive tract (pepsin, trypsin, and alpha-chymotrypsin). Results showed a direct and quantitative relationship between protein damages by hydroxyl radical and loss of protein digestibility.     

乙醇-磷酸预处理对稻草酶解糖化的影响

为了提高制生物质酒精时稻草酶解糖化率,该文采用常温常压乙醇-磷酸预处理稻草。研究了预处理温度、乙醇体积分数、预处理时间对稻草糖化率的影响以及最优条件下的回用乙醇-磷酸预处理稻草糖化效果。结果表明,在50℃、乙醇体积分数50%、处理时间60?min条件下,稻草酶解糖化率从10.03%提高到57.75%。回用乙醇-磷酸预处理后稻草糖化率达到56.89%,与乙醇-磷酸预处理后糖化率相接紧,可减少蒸馏回收乙醇次数,降低能量消耗,节省运行费用。对比预处理前后稻草物理和化学性质的变化表明,乙醇-磷酸预处理使稻草的晶状结构遭到破坏、孔隙度增加、比表面增大,易于被微生物或酶酶解。乙醇-磷酸预处理后的过滤液容易通过蒸馏、离心、过滤等方式分离得出乙醇、木质素、磷酸等有用原料。该研究提供了一种温和条件下可运用于循环生产的稻草预处理方法。     

Effect of meat cooking on physicochemical state and in vitro digestibility of myofibrillar proteins

The effect of meat cooking was measured on myofibrillar proteins from bovine M. Rectus abdominis. The heating treatment involved two temperatures (100 degrees C during 5, 15, 30, and 45 min and 270 degrees C during 1 min). Protein oxidation induced by cooking was evaluated by the level of carbonyl and free thiol groups. Structural modifications of proteins were assessed by the measurement of their surface hydrophobicity and by their aggregation state. With the aim of evaluating the impact of heat treatment on the digestive process, myofibrillar proteins were then exposed to proteases of the digestive tract (pepsin, trypsin, and alpha-chymotrypsin) in conditions of pH and temperature that simulate stomach and duodenal digestion. Meat cooking affected myofibrillar protein susceptibility to proteases, with increased or decreased rates, depending on the nature of the protease and the time/temperature parameters. Results showed a direct and quantitative relationship between protein carbonylation (p<0.01) and aggregation (p<0.05) induced by cooking and proteolytic susceptibility to pepsin. However, no such correlations have been observed with trypsin and alpha-chymotrypsin.     

Forage nutrient composition in the wet season in Benue state,Nigeria. I. Macrominerals and in vitro organic matter digestibility

Abstract

Seventy‐one forage samples were analyzed for their macromineral composition and forage in vitro organic matter digestibility (IVOMD) in three agricultural zones of Benue State, Nigeria. The zones consisted of Northern, Eastern, and Central zones, each of which were made up of four Local Government Areas. In each Local Government Area, grazing animals were monitored and forages corresponding to those consumed were collected during the peak of the wet season (June) and analyzed for their macromineral composition and IVOMD. Fewer number of forage samples were harvested from Northern and Eastern zones due to greater agricultural activities and infra‐structural land use which limited land space for grazing animals. Forage IVOMD ranged from 32% to 78.3% across all classes of forage and from 43.5% to 62.8% in the Local Government Areas. About 18% of total samples, exclusively from the Northern zone, showed forage IVOMD concentrations below 20%, probably resulting from grazing pressures and agricultural activities in the zone. Forages from the Northern zone were deficient in phosphorus (P), potassium (K), and sodium (Na) based on their criteria of adequacy. No deficiency levels were indicated in forage calcium (Ca) or magnesium (Mg). Northern and Eastern zones were in greatest need of mineral supplementation programs.     

Effect of in vitro enzymatic digestion on antioxidant activity of coffee melanoidins and fractions

Traditionally antioxidant activity of melanoidins has only been evaluated in food for implication in shelf life but gastrointestinal digestion is necessary to study their potential bioactivity. In addition, the biological fate of melanoidins has been stressed during the past decade since they did not behave as inert substances. In the present paper a soluble coffee melanoidin isolated from brewed coffee after ultrafiltration with a 10 kDa cutoff membrane was treated ionically and enzymatically collecting the respective high and low molecular weight fractions. Antioxidant activity of these fractions was evaluated with five well-described assays (DPPH, ABTS, ORAC, HOSC, and FRAP) that were previously setup in a plate reader based automatized analysis. Low molecular weight compounds released from melanoidin after gastrointestinal digestion exerted the highest antioxidant activity, even higher than compounds bound ionically to melanoidins. Gastrointestinal digestion is able to modify coffee melanoidins to some extent, as hypothesized from their absolute antioxidant activities. Two options are plausible: by modifying/releasing the ionically bound compounds and/or by genesis of new more active structures from the melanoidin skeleton after enzymatic treatment.     

Electrophoretic pattern, thermal denaturation, and in vitro digestibility of oxidized myosin

Physicochemical changes and in vitro digestibility of chicken breast myosin oxidized with a nonenzymic free-radical-generating system (FeCl(3)/H(2)O(2)/ascorbate) were studied by SDS-PAGE, differential scanning calorimetry, and o-phthaldialdehyde assay. Oxidation caused fragmentation and polymerization of myosin. Myosin polymers were cross-linked mainly through disulfide bonds. Hydroxyl radicals destabilized myosin, lowering its denaturation temperature by up to 4 degrees C. Oxidized myosin also produced a new thermal transition in the 60-80 degrees C temperature range, which could be attributed to the formation of disulfide-stabilized polymers. The proteolytic susceptibility of myosin to pepsin, trypsin, and chymotrypsin was increased by oxidation. Under nonreducing conditions, however, oxidized myosin showed decreased digestibility. The results may help explain variations in the functionality and nutritional quality of muscle foods in meat processing in which oxidation is involved.     

Effect of steam pressure treatment on the physicochemical properties of Dioscorea starches

Dioscorea alata and Dioscorea rotundata starches were subjected to steam pressure treatments (0.35, 0.7, and 1.05 kg cm(-)(2)) for different periods. The total amylose content in the treated starches was not significantly affected, but the soluble amylose content decreased 3-5-fold. Reducing values and lambda(max) of the iodine complexes were unaffected. Viscosity of the starch paste was reduced by the treatments, and at higher pressures and longer time of treatments, the peak viscosity values were reduced to very low values. Pasting temperatures were enhanced considerably. Swelling volumes underwent reduction, but no change in solubility occurred. Clarity and paste stability were markedly lowered. The results suggest that starch granules are compressed by the steam pressure treatment, leading to vast changes in physicochemical properties.     

Effect of interfacial protein cross-linking on the in vitro digestibility of emulsified corn oil by pancreatic lipase

The objective of this study was to investigate the influence of globular protein interfacial cross-linking on the in vitro digestibility of emulsified lipids by pancreatic lipase. 3% (wt/wt) corn oil-in-water emulsions stabilized by either lecithin or beta-lactoglobulin were prepared (pH 7). A portion of the beta-lactoglobulin stabilized emulsions was subjected to a heat treatment known to cross-link the adsorbed globular proteins (85 degrees C, 20 min). Pancreatic lipase and bile extract were then added to each emulsion at 37 degrees C (pH 7) and the evolution of the particle charge, particle size, appearance and free fatty acids released were measured over a period of 2 h. The rate and extent of lipid digestion did not differ greatly between lecithin and beta-lactoglobulin stabilized emulsions, nor did it differ greatly for unheated (BLG-U) or heated (BLG-H) beta-lactoglobulin stabilized emulsions. For example, the initial rate of lipid digestion was found to be 3.1, 3.4, and 2.3 mM fatty acids s(-1) m(-2) of lipid surface for droplets stabilized by BLG-U, BLG-H, and lecithin, respectively. Pancreatic lipase was able to adsorb to the droplet surfaces and access the emulsified lipids, regardless of the initial interfacial composition and the fact that some of the original emulsifier appeared to remain at the oil-water interface during digestion. These results help to explain why the human body is so efficient at digesting dietary triacylglycerols.     

Study on furundu, a traditional Sudanese fermented roselle (Hibiscus sabdariffa L.) seed: effect on in vitro protein digestibility, chemical composition, and functional properties of the total proteins

Furundu, a meat substitute, is traditionally prepared by cooking the karkade (Hibiscus sabdariffa L.) seed and then fermenting it for 9 days. Physicochemical and functional properties of raw and cooked seed and of furundu ferments were analyzed. Furundu preparation resulted in significant changes in karkade seed major nutrients. Total polyphenols and phytic acid were also reduced. The increase in total acidity and fat acidity coupled with a decrease in pH indicates microbial hydrolysis of the major nutrients; proteins, carbohydrates, and fats. In vitro digestibility of the seed proteins reached the maximum value (82.7%) at the sixth day of fermentation, but thereafter it significantly decreased. The effect of furundu preparation on N solubility profiles and functional properties, such as emulsification and foaming properties and other related parameters, is investigated in water and in 1 M NaCl extracts from defatted flour samples. The results show that cooking followed by fermentation affects proteins solubility in water and 1 M NaCl. The foaming capacity (FC) from the flour of raw seed decreased as a result of cooking. Fermentation for 9 days significantly increased the FC of the cooked seed, restoring the inherent value. Foam from fermented samples collapsed more rapidly during a period of 120 min as compared to the foam from raw and cooked karkade seeds; stability in 1 M NaCl was lower as compared to those in water. In water, the emulsion stability (ES) from the fermented samples was significantly higher than that of the raw seed flour. Addition of 1 M NaCl significantly decreased the ES of the fermented samples.     

鸡肉蛋白热处理与酶解特性的关系研究

为阐明酶解前热处理对鸡肉蛋白酶解性质的影响,采用差示扫描量热法分析鸡肉蛋白的热性质,研究热处理温度对鸡肉蛋白巯基(SH)、二硫键(S-S)含量以及碱性蛋白酶(Alcalase)、木瓜蛋白酶(Papain)酶解过程中氨基酸、肽释放的影响。结果表明：鸡肉蛋白有4个吸热峰,对应温度为63.7℃、67.6℃、74.3℃和 77.9℃;热处理温度增加,鸡肉蛋白中SH含量逐渐降低,而S-S含量逐渐增加,游离SH与S-S还原折算的SH量之和在80℃前无明显变化,80℃后下降;酶解前热处理不利于鸡肉蛋白酶解过程中游离氨基酸、小分子量肽的释放和可溶性氮的回收,但有利于大分子量肽的生成,因此可根据酶解产物的应用目的选择热处理参数。