Influence of processing on the nutritional value of proteins

The nutritive quality of food proteins can be modified by the processes utilized for the preparation of foods. The effects of the physical and chemical treatments and the interactions between proteins and food components (proteins, sugars, oxygen, polyphenols, solvents, etc.) are discussed in the context of the utilization of new plant proteins for human consumption. Modifications of nitrogen digestibility, decreases in the amino acid availability, metabolic transit of the new compounds formed, and physiological effects are discussed.     

Improvement of the functionality of vegetable proteins by controlled enzymatic hydrolysis

Vegetable proteins are available to the food industry in various forms, such as flours, concentrates, isolates, and TVP (textured vegetable protein). However, the functional properties of these products are not always optimal and need improvement for certain applications. In recent years it has been demonstrated that a limited enzymatic hydrolysis offers a convenient and specific means of improving certain functional properties of vegetable proteins. The hydrolysis reaction is controlled by the degree of hydrolysis (DH) which is defined as the percentage of peptide bonds cleaved. Under neutral or slightly alkaline conditions, DH can be monitored continuously by the pH-stat technique, since the amount of base necessary to maintain a constant pH is proportional to DH. The reaction is terminated at a preset DH-value to obtain the desired properties of the hydrolysate.Protein products from soya bean, faba bean, and potato were hydrolysed to DH 0%, 3% and 5%, and certain functional properties (iso-electric solubility, emulsification capacity, whipping expansion, and foam stability) were evaluated. The general picture observed is an increase, often pronounced, in these four properties with increasing DH — however, there are also distinct differences between the protein sources as well as between the different forms of a particular protein. This work demonstrates that protein sources indigenous to Europe are fully comparable to soya protein with respect to potential functional uses.     

Nutritive value of acetylated and hydrolysed rapeseed proteins in rats

Acetylated, hydrolysed and unmodified rapeseed proteins were compared to casein for nutritive value as determined by net protein ratio (NPR) and nitrogen apparent digestibility coefficient (ADC). The NPR and nitrogen ADC values of rapeseed proteins did not change significantly (P<0.05) after hydrolysis but decreased significantly (P<0.05) after 30% and 70% acetylation. Acetylation (30%) followed by protein hydrolysis decreased significantly (P<0.05) the NPR value but increased significantly (P<0.05) the nitrogen digestibility compared to the control and unmodified rapeseed proteins. Casein gave the highest value (P<0.05) for NPR and nitrogen ADC. Modification of rapeseed proteins significantly (P<0.05) decreased the nutritive value, and the effect was more pronounced with increasing level of acetylation.     

Effect of extrusion treatment on enzymatic hydrolysis of wheat bran

Although, wheat bran is a good source of dietary fibre (DF), it has certain disadvantages due relatively lower levels of soluble DF. Therefore, in the current study, the effect of extrusion treatment on microstructure and enzymatic hydrolysis of wheat bran was investigated. Extrusion treatment increased fibre solubility at all process conditions and the screw speed was found to be the most effective parameter. Physicochemical properties of bran were affected from extrusion treatments. While the water-binding capacities of extruded brans were lower than that of non-extruded wheat bran, their water solubilities were higher. Enzymatic hydrolysis increased the soluble DF content of the bran samples as compared to those of respective samples at the beginning of incubation. The results showed that extrusion treatment can be used to disrupt the wheat bran microstructure and thus to increase the soluble fibre content. Enzymatic hydrolysis can also be used for increasing solubility further. The outcomes of this study can be utilized for improving the technological functionality of cereal fibres to develop high fibre ingredients for food applications.     

Effect of steam explosion on enzymatic hydrolysis and baking quality of wheat bran

In this study, the effect of steam explosion (SE) treatment on microstructure, enzymatic hydrolysis and baking quality of wheat bran was investigated. Coarse and fine bran were treated at different steam temperatures (120–160 °C) and residence times (5 or 10 min) and then hydrolysed with carbohydrase enzymes. The SE treatment increased water extractable arabinoxylan (WEAX) content from 0.75 to 2.06% and reducing sugars from 0.92 to 2.41% for fine bran. The effect was more pronounced with increased SE temperature and residence time. The highest carbohydrate solubilisation was observed in fine bran at SE treatment of 160 °C, 5 min. WEAX content increased to 3.13% when this bran was incubated without enzyme, while WEAX content increased to 9.14% with enzyme addition. Microscopic analysis indicated that cell wall structure of wheat bran was disrupted by severe SE conditions. Supplementation of SE treated (150 °C, 10 min) bran at 20% replacement level decreased the baking quality of bread. However SE followed by enzymatic hydrolysis increased specific volume and decreased crumb hardness (on the day of baking and after three days of storage). Phytic acid content of bread supplemented with SE treated bran was lower than the one supplemented with untreated bran.     

Nutritive value of rapeseed proteins and fractions supplemented with methionine and tyrosine in rats

Rapeseed protein concentrate (RPC), rapeseed 2S and 12S fractions, a blend of 2S and 12S fractions, retentate (RET) and precipitate (PRE) proteins obtained during rapeseed fractionation were compared to casein for nutritive value as determined by net protein ratio (NPR) and apparent digestibility coefficient (ADC). Tyrosine concentration in rapeseed 2S fraction was the lowest compared to all other protein sources and methionine was the first limiting amino acid. The NPR and ADC of RPC, RET, and fraction 12S did not change significantly (P<0.05) following supplementation with methionine, but for PRE the NPR was decreased significantly (P<0.05). However, the rapeseed 2S fraction supplemented with tyrosine had a NPR significantly (P<0.05) higher than that of RPC and not significant (P<0.05) different from that of casein. The NPR of the 2S and 12S blend was significantly (P<0.05) higher than that of RET and PRE; however, no significant (P<0.05) difference was observed in NPR and ADC of the blend when supplemented with tyrosine. The nutritive value and digestibility of rapeseed 2S fraction were improved by supplementation with tyrosine and by blending with the 12S fraction.     

Nutritive value of soybean,rapeseed and wheat proteins,and various blends of these vegetable proteins and their fractions in rats

Blends of vegetable proteins were prepared to improve the nutritive value of these proteins. Soybean flour, rapeseed protein concentrate, whole wheat flour, soybean 2S+11S extract, wheat albumin-globulin + glutenin (AG+G) functions, and some of their blends were compared to casein for protein efficiency ratio (PER) and apparent digestibility coefficient (ADC). Autoclaving (1 h) soybean proteins was also studied. Casein and rapeseed protein concentrate gave the highest weight gains and PER. Other protein sources gave lower values for both PER (P<0.05) and weight gain. The digestibility of all vegetable proteins was lower (P<0.05) than that of casein. PER of soybean 2S+11S extract was significantly lower (P<0.05) than that of soybean flour. Autoclaving significantly (P<0.05) improved the PER of both soybean flour and 2S+11S extract. The ADC of autoclaved 2S+11S extract was similar (P<0.05) to that of autoclaved soybean flour and significantly higher (P<0.05) than that of 2S+11S extract. Soybean flour had the lowest (P<0.05) ADC. Heat treatment destroyed antinutritional factors, probably trypsin inhibitors and/or haemagglutinins of soybean. This was accompanied by improvement in the nutritional value of protein. The four blends were chosen on the basis of amino acid composition, chromatography of proteolyzates and nutritive value of each fraction. The PER of wheat albumin-globulin and glutenin (AG+G) blend was similar (P<0.05) to that of wheat flour and lower (P<0.05) than that of all other blends used. Wheat AG+G+rapeseed protein concentrate and wheat AG+G+soybean flour blends gave the highest (P<0.05) PER. Wheat AG+G improved the PER of 2S+11S extract and of soybean flour but decreased the PER of rapeseed protein concentrate. Wheat AG+G and wheat AG+G+rapeseed protein concentrate blends gave an ADC significantly higher (P<0.05) than that of wheat AG+G blend containing soybean flour of 2S+11S extract. However, blending wheat AG+G with either 2S+11S extract of soybean flour improved ADC.     

Damage to nutritional value of plant proteins by chemical reactions during storage and processing

The nutritive function of proteins for monogastric animals may be simply to supply the body with amino acids. However, the complexities of digestion, absorption and metabolism imply that amino acid composition, determined chemically after hydrolysis, can only be a very rough guide (usually setting upper limits) to the nutritional value of proteins. Chemical reactions which may affect nutritional values of proteins are discussed at length. Chemical tests, for determining the extent to which these reactions have occurred, are increasing, both in number and usefulness. However, to derive practical benefits from chemical tests, frequent parallel nutritional assessments must be conducted using animals.     

Amaranth seed proteins: Effect of defatting on extraction yield and on electrophoretic patterns

Acetone and hexane were used to know the effect of defatting amaranth flour on the extraction yield of protein fractions and on the electrophoretic patterns. It was found that albumins (33%) and globulins (20%) did not present yield changes when using these two solvents, but it was noted that with hexane compared to acetone, prolamins extraction was reduced by half (3.0 to 1.6%) whereas glutelins increased from 26.5 to 30%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of prolamins extracted with acetone and hexane showed one band of low molecular weight (22 KDa) and five bands between 52 to 22 KDa, respectively. No electrophoretic changes were observed in the remaining fractions.     

Improvement on functional properties of wheat gluten by enzymatic hydrolysis and ultrafiltration

Four fractions (100-, 50-, 20-K and permeate) from a proteolytic hydrolysate (DH=2.8%) of wheat gluten were separated using size fractionation on ultrafiltration membranes with molecular weight cut-offs of 100, 50 and 20 kDa and their functional properties evaluated. Proteolysis led to a significant (P<0.05) increase in solubility of gluten fractions at pHs between 2–10 and a shift of the pI value from 6–7 to 5. The solubilities of 100-K, 50-K, 20-K and permeate fractions were significantly (P<0.05) improved compared with the untreated control and the hydrolysate. The 50-K fraction was superior to other three fractions for emulsion activity index between pH 2 and 10. The most stable foam was given by the 100-K fraction which showed 65.8% of initial foam while the control sample gave only 23% of foam, after 60 min resting. Foam stability decreased as the molecular mass of hydrolysate fractions decreased. Furthermore, after proteolysis, the surface hydrophobicity (H₀) of gluten increased significantly (P<0.05) compared with the control except for the permeate fraction. The highest value of H₀ was given by the 100-K fraction, followed by the 50-K, 20-K and permeate fractions. In addition, proteolysis resulted in a decrease in the storage modulus of gels.     

Effects of enzymatic hydrolysis on molecular structure and antioxidant activity of barley hordein

Hordein, the major storage protein of barley (Hordeum vulgare L.), was hydrolysed by three selected proteases, including alcalase, flavourzyme and pepsin. The effects of protease type and hydrolysis time on hordein molecular weight, surface hydrophobicity, secondary structure and antioxidant activity were investigated. Flavourzyme hydrolysis of hordein was relatively more extensive and rapid, resulting in the formation of medium- and small-sized peptides with a broad distribution within 30 min. Alcalase and pepsin more gradually and less extensively hydrolysed hordein into medium- and larger-sized peptides, respectively. Protein surface hydrophobicity decreased with an increasing degree of hydrolysis. The flavourzyme and alcalase hydrolysates had superior DPPH (1,1-diphenyl-2-picryl hydrazyl) free radical scavenging activity (44-70 and 48-58%, respectively, at 0.5 mg/mL), Fe²⁺-chelating ability (21-64% and 39-73%, respectively, at 1 mg/mL), and superoxide radical scavenging capacity. It is proposed that the large- and medium-size hydrolysate fractions were most likely responsible for the antioxidant activities of hordein hydrolysates, and could be used as antioxidant peptides in food and nutraceutical applications.     

Influence of high solid concentrations on enzymatic wheat gluten hydrolysis and resulting functional properties

Enzymatic hydrolysis at increased solid concentrations is beneficial with regard to energy and water consumption. This study examines the influence of the solid concentration on the enzymatic hydrolysis of wheat gluten and the resulting functional properties of the hydrolysate. Wheat gluten was mildly hydrolyzed at a solid concentration varying from 10% to 60% to degrees of hydrolysis (DH%) ranging from 3.2% to 10.2%. The gluten was susceptible to hydrolysis at all solid concentrations but the hydrolysis rate was influenced by increasing solid concentrations. Size-exclusion high-performance liquid chromatography revealed an increase in the ratio of peptides with a molecular mass >25 kDa for solid concentrations of 40% and 60%. The water solubility increased on hydrolysis and was independent of the solid concentration during proteolysis. The foam stability was not influenced by the solid concentration at low DH%. At DH% higher than 8%, high solid concentrations increased the foam stability, which might be related to the presence of more peptides with a molecular mass >25 kDa. In addition, we found increased reactor productivity. The results show the potential of hydrolyzing wheat gluten at high solid concentrations, which could lead to large savings for water and energy when applied industrially.     

大豆酶解制油蛋白酶的筛选及工艺条件的研究

在以大豆乳液为水解底物进行酶水解来提取大豆油的工艺中,应用蛋白酶水解细胞壁中的蛋白成分使得脂蛋白复合体中的油脂得以释放,从而提高油脂的得油率,通过研究选出破壁能力较强的蛋白酶并优化其水解条件,最后得到最佳水解工艺。     

Effect of sesame seed proteins supplementation on the nutritional,physical, chemical and sensory properties of wheat flour bread

Sesame products (sesame meal, roasted and autoclaved sesame meal, sesame protein isolate and concentrate) were added to Red wheat flour to produce blends at protein levels of 14, 16, 18 and 20 percent. Dough properties were studied using a Brabender Farinograph. Loaves were prepared from the various blends using the straight dough procedure and then evaluated for volume, crust and crumb colour, crumb texture, flavour and overall quality. The water absorption, development time and dough weakening were increased (p<0.05) as the protein level increased in all blends; however, dough stability decreased. Sesame products could be added to wheat flour up to 18 percent protein level (sesame protein isolate) and up to 16 percent protein level (other sesame products) without any observed detrimental effect on bread sensory properties. No significant differences (p>0.05) were recorded in loaf volume between control and breads containing sesame protein isolate (up to 18 percent protein level) and either autoclaved sesame meal or sesame protein concentrate (up to 14 percent protein level). Addition of sesame products increased the content not only of protein but also minerals and total essential amino acids, especially lysine. The addition also improved in-vitro protein digestibility.     

敌草快对成熟期油菜脱水和种子质量的影响

为适应机械化收获对种子成熟的要求,研究化学催熟剂敌草快对油菜角果脱水和种子质量的影响,选用甘蓝型油菜品种阳光2009在油菜成熟期进行田间喷施敌草快试验,测定菜籽含水量、发芽率、千粒重、品质和敌草快残留。结果表明:于油菜角果黄熟期主花序角果转色时用1.8L/hm2的敌草快水剂喷施处理6d,与自然成熟(喷施等量清水)的对照组和人工割晒组相比,油菜脱水效果显著,角果和籽粒含水量分别为7.8%和10.49%;与对照组相比,角果和籽粒含水量分别下降52.66%和24.84%。该浓度处理下对油菜发芽率、千粒重及品质均未产生显著影响,其中发芽率达99%,贮藏2周的油菜种子中敌草快残留量为0.13mg/kg,符合中国和英国的安全标准;贮藏3周未检测到敌草快残留。建议加快敌草快在油菜催枯用途方面的农药登记,推进我国油菜全程机械化技术的应用。     

Chemical composition of solid waste and effect of enzymatic oil extraction on the microstructure of soybean (Glycine max)

The solid wastes were obtained from enzymatic extraction of soybean oil using four enzyme systems (Alcalase/Celluclast or Alcalase/Viscozyme L) each with two pH conditions: controlled or not controlled. This last option gave a better oil extraction, regardless of the enzymes used. The ash levels were higher for the enzyme systems subjected to controlled pH, depending on the buffer solutions used. The others constituents presented similar values between each other. The monosaccharides with highest concentrations were galactose, followed by glucose and arabinose. The physical analysis showed that the waste residues had good oil binding capacity. The SEM and epifluorescence microscopy revealed the microstructure of the beans and raw materials, as well as the changes caused by the extraction procedures.     

Effects of washing, milling and loading enzymes on the enzymatic hydrolysis of a steam pretreated sugarcane bagasse

Enzymatic hydrolysis of steam pretreated sugarcane bagasse was performed to investigate the production of glucose and xylose. A blend of industrial enzymes (Novozymes) was used. The enzymes were used either without having been washed or having been washed with water or 1% aqueous NaOH solution. The influence of the size of sugarcane bagasse and the proportion of the enzymatic cocktail, which was composed of endoglucanases/cellobiohydrolases (Celluclast 1.5L) and β-glucosidase (Novozym 188) cellulases mixtures, was investigated. The tests were performed at a temperature of 50 °C and at a pH of 4.8 during a period of 72 h. The assays that were conducted with a pretreated sugarcane bagasse that was washed with a 1% aqueous NaOH solution without milling led to the largest amounts of glucose after 72 h, which was independent of the proportions of enzymes used in experiments with the smallest amounts of enzymes. The largest amount of xylose was obtained with a pretreated sugarcane bagasse that was not washed.     

棉田免耕套栽油菜施肥效果及肥料适宜用量研究

在棉田免耕套栽条件下,研究了油菜氮磷钾（NPK）肥施用效果及肥料适宜用量。结果表明,合理施用氮磷钾肥促进了油菜的营养生长和生殖生长,从而显著提高了油菜的产量和经济效益,N、P、K三要素增产效果依次为：N＞P＞K。通过对肥料效应模型的筛选,得出在试验条件下,油菜氮（N）、磷（P2O5）、钾（K2O）的适宜推荐用量分别为205kg/hm2、76kg/hm2、35kg/hm2。     

The nutritional value of diets based on starchy foods and common beans

Feeding trials were carried out to determine the minimum amount of common beans, with and without methionine supplementation, needed to obtain positive weight gains of rats fed cassava, sweet potato, plantain and potato flours. The protein content of these materials was 1.4, 3.8, 3.1 and 9.5% on a dry weight basis as compared to 22.8% in common beans. The amount of beans added varied from 0 to 40.0% without and with 0.3% methionine. Without methionine addition, the amount of beans required to maintain body weight was 24.8% for plantain, 19.3% for cornstarch, 20.0% for cassava and 40.1% for sweet potatoes. With just potato flour in the diet, the animals gained weight. With methionine addition, the amount of beans required for body weight maintenance was: 20.1% for plantain, 10.1% for cornstarch, 14.5% for cassava, 14.6% for potato and 29.3% for sweet potatoes. Mixtures of potatoes with as little as 10% beans with methionine gave excellent protein quality values. The results confirm previous findings on sulfur amino acid contents of beans. It is of interest to point out that factors other than a low level of protein in the starchy food tested are influencing the level of beans needed in the presence or absence of methionine supplementation.INCAP Publication I-1355.