In vitro digestibility of protein and amino acids in protein mixtures

Six protein sources, casein, field peas, peanut meal, wheat flour, rapeseed and soya bean concentrate and their blends (ratio 1:1) were subjected to in vitro enzymic digestion. Wheat flour had the lowest in vitro digestibility (30% in 6 h) while the other sources had similar digestibilities (40%). Basic and aromatic amino acids were the most readily liberated from these protein sources. Some protein combinations, such as a rapeseed/field pea blend, gave in vitro digestibilities higher than calculated from individual proteins. The type of response observed could not be predicted from either nitrogen digestibility or amino acid composition of the individual sources. The digestibility of some amino acids was modified and this could be due to varying affinity of digestive enzymes for the protein.     

Amino acid digestibility of protein concentrates given separately or together with cereal grains

In experiments with rats the amino acid digestibility of three protein concntrates (soya bean meal, herring meal, horse bean meal) was measured when these protein sources were given separately and together with cereal grains (barley, maize, oats or wheat). True digestibility of the individual amino acid components was in general close to the digestibility of the corresponding protein source. Furthermore it was found that the true digestibility of amino acids in a feed mixture is directly related to the amino acid digestibility of the individual protein components in the diets.     

In vitro digestibility of processed and fermented soya bean,cowpea and maize

Tropical legumes, ie soya bean and cowpea, were pre‐treated and subsequently fermented using pure cultures of Rhizopus spp. Impact of soaking, cooking and fermentation of the legumes on their digestibility was determined using an in vitro digestion method. Processing of white maize included, amongst others, natural lactic acid fermentation, cooking and saccharification using barley malt. An in vitro method was standardised to carry out comparative determinations of the dry matter digestibility of cereal and legume food samples as a function of processing conditions, without attempting to exactly mimic gastrointestinal digestion. Using this method based on upper digestive tract digestion, it was observed that digestibility of the legumes increased during cooking and fermentation. Cooking improved the total digestibility of both soya bean and cowpea from 36.5 to 44.8% and from 15.4 to 40.9% respectively. Subsequent fungal fermentation increased total digestibility only by about 3% for both soya bean and cowpea. Digestibility was also influenced by fungal strain and fermentation time. Cooking and subsequent saccharification using malt almost tripled total digestibility of white maize from 25.5 to 63.6%, whereas lactic fermentation of maize had no effect on in vitro dry matter digestibility. Although total digestibility of cooked legumes was only slightly improved by mould fermentation (3% for both soya bean and cowpea), the level of water‐soluble dry matter of food samples increased during fermentation with Rhizopus oryzae from 7.0 up to 27.3% for soya bean and from 4.3 up to 24.1% for cowpea. These fermented products could therefore play a role as sources of easily available nutrients for individuals suffering from digestive disorders. © 2000 Society of Chemical Industry     

The effect of leaf protein concentrate from red clover on plasma cholesterol level in rats

The effect of native and defatted leaf protein concentrate (LPC) from red clover on plasma cholesterol level in rats was studied. Fat-free casein was used as a control protein. The native LPC contained 212 g kg^?1 of ether extract and oleic acid (C_{18: 1}) was its main fatty acid. LPC protein was relatively poor in sulphur-containing amino acids. Each protein studied was given to rats with or without soya bean oil. It was found that total cholesterol level in plasma of rats fed with the oil-containing diets was higher than that of rats fed with the oil-free diets. Original fat present in the native LPC though rich in unsaturated fatty acids had no hypocholesterolaemic effect. LPC was hypocholesterolaemic compared with casein in diets not containing added soya bean oil, although the difference did not reach statistical significance.     

Effect of Lectins and the Mixing of Proteins on Rate of Protein Digestibility

The rate of digestibility of protein in raw bean extract (RBE), heat-treated bean extract (HBE), casein and bovine serum albumin (BSA) was determined. The pepsin and/or pancreatin hydrolysis of RBE which contains lectins or hemagglutinins was less than that of other proteins. Addition of lectins at the same concentration present in RBE decreased the rate of digestion of HBE, casein and BSA to levels close to that of RBE. In comparison with the respective single proteins, mixtures of RBE or HBE with casein have lower digestibilities while a mixture of casein and BSA, higher digestibilities. The results suggest that lectins can affect the activity of digestive enzymes and that mixing of proteins has an effect on digestibility which is unpredicted by amino acid composition.     

Preparation and characterisation of soya milk enriched with isoflavone aglycone fermented by lactic acid bacteria combined with hydrothermal cooking pretreatment

A fermented soya milk (FSM) enriched with isoflavone aglycone (FSM‐SPIA) was prepared from heated soya protein isolate (SPI)‐isoflavone complex. After 48 h of fermentation, FSM‐SPIA contained higher contents of living bacteria, free amino acids and aglycone compared with the FSM of SPI (FSM‐SPI) and the FSM of SPI‐isoflavone complex (FSM‐Mix). In the in‐vitro digestion experiment, FSM‐SPIA showed higher antioxidant capacity and isoflavones (ISO) bioavailability than FSM‐SPI and FSM‐Mix. This was likely due to the soya milk containing a higher level of amino acid, peptides and the presence of soya bean isoflavone. The improved protein digestibility, the interaction and binding ability between proteins and ISO may affect the properties of the protein and the fermented products. The FSM enriched with isoflavone aglycone can be used as a functional fermented drink, as well as an auxiliary food for menopausal women during a specific pathological period.     

Pork quality from pigs fed on low glucosinate rapeseed meal: Influence of level in the diet,sex and ultimate pH

The appearance and eating quality of pork M. longissimus lumbrum from gilt and castrate pigs fed on diets containing a low glucosinate/low erucic acid rapeseed meal (cv. Tower) were assessed and compared with pork from pigs fed diets containing soya bean meal. At 90 kg liveweight, higher levels of either protein supplement, and therefore higher levels of dietary protein, gave slightly leaner meat. Meat from pigs fed rapeseed meal had more haem pigment and was slightly darker and redder than that from soya bean fed pigs. Differences in the quality of pork from the low glucosinate rapeseed meal and soya bean diets were small. Ratings for texture, juiciness and flavour of the lean varied little between the treatment groups. Suggestions that rapeseed meal as a protein supplement in diets might lead to inferior quality meat were not substantiated. The ultimate pH varied from 5.3 to 7.1 independently of the treatments and provided, for the first time, definitive relationships between pH and eating quality. Toughness and flavour were maximum and juiciness was a minimum after roasting meat of about pH 5.9. The ultimate pH had a larger effect on organoleptic quality than either sex or level of dietary inclusion of rapeseed or soya bean meals.     

Endogenous lysine flow at the distal ileum of the protein-fed rat: Investigation of the effect of protein source using radioactively labelled acetylated lysine or lysine transformed to homoarginine

The study aimed to determine if the source of purified dietary protein influenced endogenous lysine flow at the terminal ileum of the growing rat. Partially guanidinated gelatin and isolated soya bean protein based diets, containing chromic oxide as an indigestible marker, were given to 225-g liveweight rats. The endogenous flow of lysine at the terminal ileum was then determined indirectly, based on the absorption of homoarginine, after sampling of ileal contents at slaughter. Endogenous lysine flow was also determined by reference to chromium levels in sampled ileal digesta, after feeding rats either gelatin or isolated soya bean protein or casein based diets in which some of the lysine had been acetylated with [¹⁴C]-acetic anhydride. The [¹⁴C] acetylated lysine was used to distinguish between lysine of dietary and endogenous origin. Mean endogenous ileal lysine flows were 426 and 442 μ g^?1 dietary freeze dry matter intake for the guanidinated gelatin (n=6) and soya bean (n = 6) treatments, respectively, and there was no significant (P>0.05) effect of protein source on endogenous flow. Nor did there appear to be any effect of dietary protein source on endogenous ileal lysine flow when measurement was based on the radio-actively labelled acetylated lysine. The data, considered together, indicate no effect of the source of dietary protein per se on endogenous ileal lysine flow in the rat when purified proteins were given over a short (8-h) time period. The mean true ileal digestibility coefficients for dietary lysine (0.897, 0.904, 0.926, 0.971, 0.916; acetylated gelatin, guanidinated gelatin, guanidinated soya bean, acetylated soya bean, acetylated casein, respectively) indicated a high degree of absorption of lysine before the end of the ileum in the growing rat.     

速熟黑豆理化性质的研究

为研究速熟黑豆的理化性质,考察其与原料黑豆之间的差异,分析了黑豆的营养成分、氨基酸组成及体外消化性,同时利用扫描电子显微镜、傅里叶红外光谱扫描及差示扫描量热分析方法研究了黑豆的理化性质。结果表明,速熟黑豆与原料黑豆相比,淀粉含量增加9.13%,粗蛋白、粗脂肪含量稍有减少,氨基酸总量略有减少,蛋白溶解性变差,而消化性明显提高;速熟黑豆粉微颗粒间聚集成块状,尺寸变大;与原料黑豆相比成分变化不大,但速熟黑豆蛋白分子聚集,其蛋白溶解性变差;热分析过程中,速熟黑豆的蛋白没有吸热峰出现,表明速熟黑豆蛋白热变性完全。      

Effects of fumarate on ruminal ammonia accumulation and fiber digestion in vitro and nutrient utilization in dairy does

The objective of this study was to evaluate effects of fumarate on ruminal ammonia accumulation and fiber digestion in vitro and on feed intake and nutrient utilization in dairy does. Batch cultures of mixed rumen microorganisms were used to study effects of different concentrations of fumarate on fermentation with various N sources (ammonia as ammonium bicarbonate, casein amino acids, casein peptides, gelatin peptides) and feeds (bermudagrass hay, mixed diet of 60% bermudagrass hay plus 40% concentrate) for 6 and 24 h, respectively. Substrates were grouped into pairs for separate incubations. Monosodium fumarate was added to incubation tubes to achieve final concentrations of 0, 5, and 10 mM fumarate. More ammonia accumulated at the end of incubation with added ammonium bicarbonate. Ammonia concentration was higher for peptide compared with amino acid incubation, and for casein peptide compared with gelatin peptide. Addition of fumarate linearly decreased ammonia for all N sources and for feed substrates. For all substrate types, fumarate treatment increased acetate, propionate, and total volatile fatty acids (VFA), decreased acetate to propionate ratio, and tended to reduce branched-chain VFA. Digestion of feed neutral detergent fiber (NDF) by rumen microorganisms was improved by fumarate along with elevated endoglucanase and xylanase activities. In an animal metabolism experiment, 8 dairy does (4 per treatment) were used in a completely randomized design for 21 d. Does were fed a hay plus concentrate diet without (control) or with fumarate (6 g/head per day) supplementation to determine feed intake, whole-tract nutrient digestibility, and N utilization. Fumarate treatment did not affect weight change or feed intake but increased whole-tract digestion of gross energy, crude protein, and cellulose. Digested N was increased by fumarate supplementation; however, N retention was unaffected. Plasma glucose concentration was elevated with fumarate but urea N concentration remained unchanged. Fumarate addition had significant effects on rumen microbial fermentation by decreasing ammonia and branched-chain VFA, and by increasing acetate and propionate, and NDF digestion. These effects were reflected in the improvement in whole-tract gross energy, crude protein, and cellulose digestion and elevated plasma glucose concentration when dairy does were supplemented with fumarate.     

Determination of D-Amino Acids in Some Processed Foods and Effect of Racemization on In Vitro Digestibility of Casein

Several processed foods and controls were analyzed by gas chromatography for the presence of D-amino acids. The concentration of each of the D-amino acids detected in the processed foods was approximately the same as that in the controls except that D-aspartic acid was significantly higher in dark toast surface and extruded soy flour. In vitro digestibility of casein which was alkali-treated to cause racemization, but without lysinoalanine (LAL) formation, was essentially the same as that of racemized casein containing LAL, but was lower than that of nonracemized control casein.     

Influence of polyethylene glycol on the excretion and digestibility of amino acids in casein and tannic acid‐fed broilers

Using the precision feeding technique, an experiment was conducted to evaluate the influence of tannic acid (TA) and polyethylene glycol (PEG) on the excretion of amino acids and the apparent and true digestibilities of casein protein in broilers. Seventy‐two 9‐week‐old broiler cockerels grouped in nine treatments of eight replicates were fed warm water (50 mL, control birds), casein alone (12 or 18 g) or casein (12 or 18 g) with TA solution (4.5 g per 10 mL) or/and PEG solution (2 g per 10 mL). Total excreta were collected for 48 h and freeze‐dried. The amino acid content of casein and excreta was determined by reverse phase high‐performance liquid chromatography. In the absence of TA the digestibility of casein was almost complete. TA increased the excretion of amino acids to a varying extent (P < 0.01). Although the digestibility of all essential and non‐essential amino acids was adversely affected by the presence of TA, raising the amount of casein from 12 to 18 g improved significantly (P < 0.05) the apparent and true digestibilities of all amino acids. PEG reduced significantly (P < 0.01) the excretion of amino acids and improved significantly (P < 0.01) the amino acid digestibility of casein in TA‐dosed birds. However, the improvement was greater when the lower level of casein (12 g) was fed. Thus PEG might play an important role in inactivating dietary tannins in the gastrointestinal tract of birds and improving protein digestibility and utilisation, particularly when the diet is low or intermediate in protein. Copyright © 2007 Society of Chemical Industry     

The influence of dietary fibre sources on growth,feed efficiency and digestibilities of dry matter and protein in rats

Hulls from Tower canola (TCH), Regent canola (RCH) and soya beans (SBH) were included at 10 or 20% in soya bean meal based diets for rats, to compare the effects of these fibre sources on growth, feed consumption, feed efficiency and dry matter and protein digestibilities. A soya bean meal based control diet and another diet containing a purified fibre source (Alphafloc) at a 10% level, were included for a further comparison. Each of the diets was fed to six rats in a 4-week feeding trial. The diets gave similar weight gain, feed consumption and feed efficiency values. The control diet had the highest mean coefficient of dry matter digestibility (80.8%) and the 20% SBH and Alphafloc diets had the lowest (72.4 and 72.2%). The canola hull and 10% SBH and Alphafloc diets had intermediate values (73.2–75.0%). There was a highly significant negative correlation between the dietary fibre content and the dry matter digestibility of the diets. The control and Alphafloc diets showed the highest and similar apparent (81.4 and 79.9%) and true (86.8 and 85.3%) digestibility values for dietary protein. The 20% canola and soya bean hull diets showed the lowest apparent (71.4–73.7%) and true (76.9–79.4%) digestibility coefficients. The 10% canola and soya bean hull diets had intermediate apparent and true protein digestibility values (73.2-75.3 and 78.4–80.6%, respectively). The chemical analysis of the fibre sources showed that Alphafloc had the highest cellulose content (88%) and the lowest lignin content (0.6%), while canola hulls had the lowest cellulose content (25.4–28.4%) and the highest lignin content (26.6–28.9%). Soya bean hulls had intermediate cellulose (50%) and low lignin (1.3%) contents. The results suggest that cellulose did not have a detrimental effect on the dietary protein digestibility but lignin and/or some other undetermined factors in the hulls had an adverse effect on protein digestibility.     

Nutritional quality evaluation of commercial protein supplements

Protein supplements have received increasing attention by consumers over the last few decades. However, hundreds of them have recently exhibited irregularities including lower quantities of proteins than disclosed values. This study aimed to evaluate the nutritional quality of six commercial protein supplement powders (calcium caseinate, milk protein concentrate, egg white, pea protein isolate, whey protein concentrate and soy protein isolate). The chemical composition, amino acid content and in vitro digestibility were examined. Thus, calculate the amino acid scores corrected for amino acid and protein digestibility. In vitro digestion was also conducted and protein hydrolysis was monitored by SDS-page. Calcium caseinate powder and whey protein concentrate were only composed of proteinogenic amino acids and exhibited the highest essential amino acid content. As regards in vitro digestibility, these two supplements perfectly meet the quality expectations of the Food and Agricultural Organization (FAO). Conversely, the other four supplements exhibited a lower quality than the FAO reference protein. This was due to low digestibility (for egg white and milk concentrate) and/or lack of a specific essential amino acid (for milk concentrate and pea isolate).     

In vitro digestibility of bacillus fermented soya bean

Bacillus fermented legume products include among others dawadawa and soumbala made from African locust bean, and natto and kinema made from soya bean. Bacillus subtilis is the dominant species involved in the fermentation. During Bacillus fermentation for 48 h of autoclaved soya bean the quantity of soluble and dialyzable matter increased from 22% and 6% up to 65% and 40%, respectively. Protein and carbohydrate degradation during fermentation of soya bean with several Bacillus spp. was investigated and appeared to be substantial during the first 18 h of fermentation resulting in the release of high levels of peptides and oligosaccharides. In vitro digestibility was increased from 29% up to 33–43% after Bacillus fermentation for 48 h. It was shown that Bacillus spp. were able to degrade soya bean macromolecules to a large extent resulting in water-soluble low molecular weight compounds. In vitro digestion of Bacillus fermented soya bean using gastrointestinal enzymes only slightly increased the amount of dialyzable matter, which clearly demonstrated the beneficial effect of Bacillus fermentation on food nutrient availability.     

Nutritional evaluation of soya beans (glycine max): Nitrogen balance and fractionation studies

The poor nutritional performance of rats fed raw soya-bean-containing diets appeared to be due to reduced apparent digestion and absorption of dietary protein, coupled to changes in systemic metabolism leading to a poor overall nitrogen balance. Aqueous heat treatment greatly reduced but did not eliminate the antinutritional effect. Heat treatment with aqueous ethanol was more effective. The whey protein (pH 4.8 soluble extract) fraction contained the bulk of the trypsin inhibitor and haemagglutination activity and gave the poorest net protein utilisation value. However, an eight-fold increase in trypsin inhibitor content did not significantly effect apparent nitrogen digestibility. Therefore inhibition of gut proteolytic enzyme activity in vivo by soya bean trypsin inhibitors did not account fully for the poor nutritional performance. The problems elicited by soya bean are not transitory and thus there was a cumulative deterioration in overall performance for 16 weeks as a result of continuous exposure to soya bean.     

Chemical evaluation of nutritive value of soya paps and porridges,the Nigerian weaning foods

The nutritive value of paps and porridges prepared using millet, guinea corn and maize was assessed by chemical analysis before and after supplementation with soya bean milk or flour. Millet porridge fortified with soya bean milk had the highest amounts of protein and essential amino acids.The nutrient status of the fortified paps and porridges was comparable with that of a commercial weaning food, cerelac. The value of the soya bean paps and porridges as weaning foods for Nigerian children is discussed.     

Quantitative comparison of casein and rapeseed proteolysis by pancreatin

The problem of quantitative comparison of kinetic curves was solved for casein and rapeseed pancreatin hydrolysis in a membrane reactor, which ensured the measurement of proteolysis kinetics for the products with a molecular weight of less than 1000. Coordinates were derived which provided good linearization of kinetic curves and the determination of relative rate constants irrespective of reagent concentrations. E₀/S₀ ratio and time intervals of kinetic measurements. When the relative rate constants of the release of the individual amino acid residues in the low-weight proteolysis products were compared, trypsin-dependent constants (for Lys and Arg residues) were found to be two times less for rapeseed than for casein, and chymotrypsin-dependent constants (for Tyr and Phe residues) were approximately 1.3 times higher for rapeseed than for casein. Statistical analysis demonstrated that the distribution of constants was narrower for rapeseed than for casein. Differences between target (Arg, Lys, Tyr and Phe) and non-target constants of release in the form of peptides and free amino acids, or in the form of free amino acids only, were attributed to the differences in the peptide bond masking for casein and rapeseed proteins. Computer simulation of proteolysis kinetics was performed by PROTEOLYSIS program package to confirm the dependence of rate constant distribution on the state of masking.     

超声和酶处理对乳化猪油体外消化特性的影响

本研究以猪油为原料,超声诱导脂肪晶体发生重排,采用谷氨酰胺转氨酶（transglutaminase,TG）交联 浓缩乳清蛋白作为乳化剂,制备改性乳化猪油,进而探讨乳化猪油未吸附蛋白含量的变化,并在体外消化模型中以 平均粒径、Zeta电位、游离脂肪酸释放量以及脂肪颗粒微观结构作为评价指标,对改性乳化猪油体外消化特性进行 研究。结果表明,超声和TG处理分别对乳化猪油产生不同的作用,超声处理后乳化猪油未吸附蛋白含量低于未处 理样品,乳化稳定性降低,而TG处理则提高了乳化猪油的乳化稳定性。超声处理后的乳化猪油在体外消化过程中 的游离脂肪酸的释放量、平均粒径显著高于未处理样品（P＜0.05）,Zeta电位明显低于未处理样品。而TG交联浓 缩乳清蛋白促使乳化猪油颗粒更加细小,在体外消化过程中游离脂肪酸的释放量显著降低（P＜0.05）。超声处理 的乳化猪油更易于消化,TG处理则减缓了乳化猪油的消化速率。     

Comparison of effects of prickly pear (Opuntia ficus indica sp) fruit,arabic gum,carrageenan, alginic acid,locust bean gum and citrus pectin on viscosity and in vitro digestibility of casein

The consumption of high levels of fibres can induce a decrease in both food digestibility and nutrient availability. Prickly pear is a pectin‐rich fruit and it is possible to use it to decrease plasma cholesterol levels. Its effect on food digestibility deserves attention. This effect was determined by using a mixture of a constant quantity of casein and an increasing quantity (10, 20, 25% of the casein) of prickly pear pulp, skin and seed. In parallel, the effect of similar mixtures of carrageenan, gum arabic, locust bean gum, alginic acid and citrus pectin with casein was also studied. The flow behaviour of the different mixtures was determined and their digestibilities were measured using an in vitro digestion cell device. The apparent viscosities of the mixtures with prickly pear components and gum arabic were similar. The nature and level of fibres in the diet modified nitrogen release in the in vitro digestion cell model. The pulp of the prickly pear decreased the digestibility of the casein‐based diet to a greater extent than the other soluble fibres, whatever the percentage used. The results suggest that the decrease in N release in the digestion cell model is due to the interaction of the fibres with the enzymes or casein rather than to the apparent viscosity of the mixtures. © 2000 Society of Chemical Industry