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.     

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.     

Nutritive value of protein fractions extracted from soybean,rapeseed and wheat flours in the rat

The nutritive value of various protein fractions was studied. Fractions 2S and 12S from rapeseed, 2S, 7S and 11S from soybean were obtained by dissolution in ammonium sulfate solutions. Albumin-globulin, gluten, glutenin and gliadin fractions from wheat were obtained by dissolution in salted water (albumin-globulin), acetic acid (glutenin) and alcohol (gliadin). Liveweight gains, protein efficiency ratio (PER) and apparent digestibility coefficient (ADC) were used as measures of the nutritive value. The protein fractions had a lower nutritive value than the unfractionated proteins except for the albumin-globulin fraction of wheat which had a nutritive value higher than that of the unfractionated wheat protein. PER obtained with the rapeseed 2S and 12S fractions were 2.49 and 2.21, respectively, as compared to 2.64 for unfractionated rapeseed. With soybean fractions, PER were 0.92 for 2S, — 0.007 for 7S and 1.47 for 11S, as compared to 2.19 for the original protein. The wheat albumin-globulin fraction gave a PER of 2.78, as compared to 1.45 for the unfractionated wheat protein. Gluten, glutenin and gliadin fractions had a lower PER than that of unfractionated wheat protein. ADC of all fractions were higher than those of the original proteins. The difference in liveweight gains and PER observed between protein fractions can be partially explained on the basis of the essential amino acid content.     

Growth,blood chemistry and histology of rats fed zincsupplemented rapeseed protein concentrates

Two rapeseed protein concentrates (RPC) supplemented with zinc oxide were fed to male and female rats at two levels providing approximately half or all of the protein in a purified basal diet containing 20% protein (N×6.25). Control groups were given either a purified basal diet with casein or a laboratory chow diet. After 16 weeks, there were no significant (P<0.05) differences in body weight except the male rats fed the casein control diet had higher body weights than did other male rats. No significant differences were observed in organ weights including thyroids, hematology, bone marrow differential counts, serum glucose, urea nitrogen, total protein, albumin/globulin ratio, cholesterol, transaminases or alkaline phosphatase. The levels of serum vitamins A and E of females fed some of the RPC diets were less than in those fed the caseincontrol diet, but equal to those in females fed laboratory chow diet. Females fed either RPC or casein in the semi-purified diets, which contained zinc oxide, exhibited kidney calcification.Bureau of Nutritional Sciences, No. 112; Food Research Institute, No. 420.     

Relationship between amino acid scores and protein quality indices based on rat growth

Protein efficiency ratio (PER), relative PER (RPER), net protein ratio (NPR) and relative NPR (RNPR) values, and amino acid scores were calculated for 20 food products (casein, casein + Met, beef salami, skim milk, tuna, chicken frankfurters, sausage, heated skim milk, peanut butter, rolled oats, soy isolate, chick peas, pea concentrate, kidney beans, wheat cereal, pinto bean, lentils, rice-wheat gluten cereal, macaroni-cheese, and beef stew). In most cases, PER, RPER, NPR or RNPR ranked the products in the same order and positive correlations among the protein quality methods were highly significant (r=0.98–0.99). Amino acid scores (based on the first limiting amino acid, Lys-Met-Cys, Lys-Met-Cys-Trp or lys-Met-Cys-Trp-Thr) were positively correlated to the PER, RPER, NPR or RNPR data (r=0.61–0.75). Inclusion of the correction for true digestibility of protein improved the correlations between amino acid scores and the indices based on rat growth. The correlations were especially high between Lys-Met-Cys scores (corrected for true digestibility of protein) and PER, RPER, NPR or RNPR (r=0.86–0.91). Inclusion of the correction for true digestibility of individual amino acids did not result in further improvements of the correlations in most cases. It is concluded that adjusting amino acid scores for true digestibility of protein would be sufficient and further correction for digestibility of amino acids would be unnecessary in mixed diets.This paper was presented in part at the 71st annual FASAB meeting, Washington, DC, March 29–April 2, 1987.     

Changes in chemical and selected biochemical components,protein quality,and digestibility of mung bean (Vigna radiata) during gemination and cooking

The effect of germination on the nutritive value of mung beans (Vigna radiata) was studied in raw and cooked samples after 0, 2 and 4 days of germination. Water content increased, but crude protein, lipids, crude fiber, ash and carbohydrates decreased with germination. Trypsin inhibitor activity did not change significantly while hemagglutinins were absent. Essential amino acids (methionine, tyrptophan and lysine) decreased with germination.Net protein ratio (NPR) and protein efficiency ratio (PER) in rats decreased with germination especially in cooked sprouts. True digestibility did not change consistently due to germination or cooking. In conclusion, loss of protein quality in mung beans occurs upon germination and cooking.Publication INCAP/UNU-4.     

Chemical and biological characteristics of a West African weaning food supplemented with compea (Vigna unguiculata)

The effects of cowpea and amino acid supplementation on the protein quality and chemical characteristics of a maize-based West African traditional weaning food were studied. Process optimization for improved nutritive value was also determined. Supplementation of the traditional weaning food with cowpea increased the lysine, tryptophan and threonine content while the sulphur-amino acids decreased with increasing levels of cowpea. Further supplementation of 70:30 maize/cowpea blends with lysine, threonine or methionine did not significantly improve (p>0.05) protein quality in terms of the biological value (BV) and net protein utilization (NPU), although significant increases in the protein scores were noted. However, considerable improvements in the BV and NPU were recorded in blends fortified with either tryptophan alone or a combination of lysine, tryptophan, methionine and threonine. Cooking whole cowpea seeds for 45 min before incorporating in the blend formulation also significantly improved (p<0.05) the protein quality of maize/cowpea blends. The BV and NPU of blends containing 30% pre-cooked cowpea increased from 52 to 76% and 50 to 71% respectively compared to pure maize porridge. The protein content increased from 10 to 14% and the utilizable proteins more than doubled. The weight increase of experimental rats fed with these blends was comparable to that of rats on casein diet. A 30% supplementation of the maize-based weaning food with cowpea therefore greatly enhances the nutritive value especially when the cowpea is pre-cooked for 45 min. Use of chemical scores alone for such blends cannot be a reliable index of blend quality.     

Iodine metabolism and tissue mineral levels in rats fed rapeseed protein concentrates supplemented with zinc

A 16-week feeding test of Tower (Brassica napus) and Span (Brassica campestris) rapeseed protein concentrates (RPC) was carried out on male and female Charles River CD (Sprague-Dawley) weanling rats. The diets contained 10% or 20% protein (N × 6.25) from each RPC and were supplemented with 150 mg zinc/kg. The control groups received a purified diet with casein or a laboratory chow diet. The results of the test diet groups did not reveal any adverse effect due to RPC on thyroid metabolism or the metabolism of zinc iron, copper, manganese, calcium, phosphorus, and magnesium. Nephrocalcinosis was observed in all female rats that were fed the test diets and the casein control diet, and therefore it could not be attributed to dietary RPC.Bureau of Nutritional Sciences, no. 120. Food Research Institute, no. 448.     

The nutritive value of all-vegetable protein diets based on legume,cereal and tuber in weanling rats

Thirty albino weanling male rats (45–55 g) were divided into five groups of six rats each on the basis of body weight and fed combinations of dehulled brown beans (DBB); parboiled rice (R); and cassava meal (G) which provided 10% protein for 35 days. Casein served as the reference protein. Combinations of DBB (50–80%); with R (18–48%); and G (2%) produced varied effects on body weight, nitrogen (N) intake, N digestibility and retention, BV, liver weight and plasma albumin (P<0.05).The DBB:R:G (70:28:2) blend induced decreases in all the parameters tested except for the BV and PER values. The control group produced digested and retained N, protein efficiency ratio (PER), weight gain and liver weight that were significantly higher than for those of the test diets (P<0.05). These results appear to suggest that starchy foods when blended with legumes at low levels produced good quality protein comparable to casein.     

Digestibility of protein and amino acids in selected foods as determined by a rat balance method

Values (%) for true digestibility of crude protein and individual amino acids in 20 selected foods were determined by the rat balance (fecal) method. The products were fed as the sole source of protein in diets containing 8% crude protein (N × 6.25). Lowest true protein digestibility values (79–84) were obtained for pinto beans, kidney beans and lentils; intermediate values (89–92) were obtained for chick peas, beef stew, skim milk (over heated), rolled oats, whole wheat cereal, and pea protein concentrate; and highest values (94–100) were obtained for sausage, macaroni-cheese, rice-wheat gluten cereal, skim milk, tuna, soy isolate, peanut butter, chicken frankfurters, beef salami, casein and casein + methionine. In animal foods, peanut butter and soy isolate, the differences between true digestibility of crude protein and most individual amino acids were less than 5%. However, the values for true digestibility of methionine and cystine were up to 44% lower than those of crude protein in pinto beans, kidney beans, lentils, chick peas and pea concentrate. In these legumes, digestibility of crude protein was not a good predictor of digestibility of the limiting amino acids.     

The nutritive quality of maize-soybean (70:30) tempe flour

The nutritive quality of maize-soybean (70:30) tempe flour manufactured by fermentation withRhizopus oligosporus: Rhizopus orysae (1:1) was determined using weanling rats. Mould fermentation of maize-soybean mixture did not significantly affect its proximate composition. It increased the content of reducing sugars, total acids and aminonitrogen by about 43, 195 and 482 percent, respectively, and decreased phytate content by 46 percent. In vitro iron absorption for maize flour and maize-soybean tempe flour was 2.46 and 5.51 percent, respectively. Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR) for maize-soybean tempe flour and skim-milk diets were 2.71 and 2.96, respectively, for PER, and 3.31 and 3.51, respectively, for NPR. In vivo protein digestibility of the two products was 95.0 and 98.0 percent, respectively.     

Improvement of rapeseed protein nutritional value

Although the efficiency ratio (PER) of vegetable proteins can be improved by supplementation with the limiting free amino acids, the digestibility of these proteins remains lower than that of animal proteins. The digestibility of a rapeseed protein concentrate measured in rats was improved from a value of 81 to 87% by water solubilization and ammonium sulfate precipitation. 2S and 12S fractions were also prepared from a rapeseed protein concentrate by a method based on differences of solubility in ammonium sulfate solutions. Protein digestibility of the rapeseed protein concentrate was found to be 82%, as compared to 87% and 89% for 2S and 12S fractions. A reduction of protein efficiency ratio was also recorded and was found to result from losses in amino acids.     

Growth rate,muscle protein composition,intestinal absorption of D-galactose and L-leucine and nitrogen balance in rats fed the raw legumeChamaecytisus proliferus L.

Growth rate, nitrogen balance, skeletal muscle nitrogen fractions and in vivo intestinal absorption of D-galactose (2 mM) and L-leucine (20 mM) have been measured in male growing rats (90–100 g initial body weight) fed 12% protein diets containing either casein (control) or the raw leafy legumeChamaecytisus proliferus L. (Western Canary Islands). As compared to control casein-fed rats, those fed the raw legume diet exhibited a significant reduction (P<0.01) in the rate of growth, nitrogen balance parameters, sarcoplasmic nitrogenous fraction of skeletal musculature and in vivo intestinal absorption of galactose and leucine; however, the non-protein nitrogenous fraction has been found significantly higher (P<0.01) than that of control animals, whereas the myofibrillar nitrogenous fraction remained unchanged. The possible nature of these findings is discussed.     

Apparent digestibility and nitrogen utilization of diets based on maize silage harvested at three stages of maturity and fed to steers

Advancing maize crop maturity is associated with changes in ear‐to‐stover ratio which may have consequences for the digestibility of the ensiled crop. The apparent digestibility and nitrogen retention of three diets (Early, Mid and Late) containing maize silages made from maize of advancing harvest date [dry matter (DM) contents of the maize silages were 273, 314 and 367 g kg^?1 for the silages in the Early, Mid and Late diets respectively], together with a protein supplement offered in sufficient quantities to make the diets isonitrogenous, were measured in six Holstein–Friesian steers in an incomplete Latin square design with four periods. Dry‐matter intake of maize silage tended to be least for the Early diet and greatest for the Medium diet (P = 0·182). Apparent digestibility of DM and organic matter did not differ between diets. Apparent digestibility of energy was lowest in the Late diet (P = 0·057) and the metabolizable energy concentrations of the three silages were calculated as 11·0, 11·1 and 10·6 MJ kg^?1 DM for the Early, Medium and Late diets respectively (P = 0·068). No differences were detected between diets in starch digestibility but the number of undamaged grains present in the faeces of animals fed the Late diet was significantly higher than with the Early and Mid diets (P = 0·006). The apparent digestibility of neutral‐detergent fibre of the diets reduced significantly as silage DM content increased (P = 0·012) with a similar trend for the apparent digestibility of acid‐detergent fibre (P = 0·078). Apparent digestibility of nitrogen (N) was similar for the Early and Mid diets, both being greater than the Late diet (P = 0·035). Nitrogen retention did not differ between diets. It was concluded that delaying harvest until the DM content is above 300 g kg^?1 can negatively affect the nutritive value of maize silage in the UK.     

Inclusion of alfalfa improves nutritive value and in vitro digestibility of various straw–grass mixed silages in Tibet

To enlarge the feed resources and enhance the utilization efficiency of straws as ruminant feed in Tibet, four kinds of local crop straws with tall fescue (Festuca arundinacea Schreb.) based on the ratio of 40/60 (fresh weight) were ensiled with four levels (0, 10%, 20% and 30% of fresh weight) of alfalfa (Medicago sativa L.), respectively. The laboratory silos (1L) were opened after 45 days of ensiling, and the fermentation characteristics, nutritive value and in vitro digestibility of the mixed silages were analysed. The silages including alfalfa had significantly (p < 0.05) or numerically (p > 0.05) higher lactic acid and crude protein contents, lactic acid bacteria counts, in vitro digestibility of dry matter, neutral detergent fibre (NDF) and acid detergent fibre (ADF), and lower NDF and ADF contents than controls. The results suggest that inclusion of alfalfa to mixtures of straws and tall fescue had favourable effects on fermentation quality and obviously improved the nutritive value and in vitro digestibility of mixed silages. This effect was most evident when the inclusion proportion of alfalfa was 30% in oat straw mixed silage.     

Effect of processing on some chemical and nutritional characteristics of pre-cooked and dehydrated legumes

The effect of processing on chemical composition and protein quality of three legumes was studied. The species analyzed were beans (Phaseolus vulgaris), Tórtola and Coscorrón varieties; lentils (Lens esculenta), Laird variety; and chick peas (Cicer arietinum), California-INIA variety. The legumes were soaked in a solution of Na₂ EDTA at 0.03% for 16 h and cooked for a predetermined period for each species. They were dried in a tray drier with cross currents of air flowing at a speed of 10 m/min until the residual mositure content was 8%. The water activity in the resulting products ranged from 0.574 to 0.587, thus completely assurring no microbial activity. No important changes were observed in the legumes protein, fat, or fibre contents after processing. The soaking solution was effective in reducing the phytic acid content from 2.99 to 1.64 mg/100 g in the Tórtola beans, which had the highest acid value prior processing. In all the species the heat treatment reduced the activity of the trypsin inhibitors by at least 50%. Cooking and drying significantly increased protein digestibility in all the legumes studied, with chick peas showing the most dramatic increase: from 54.7% pre-processing to 94.9% post-processing. With regard to Net Protein Ratio (NPR), chick peas had a value of 4.03, followed by Tórtola beans (3.29), Coscorrón (3.09) and lentils (2.61). The NPR value for the casein diet was 4.20.     

Plastic film mulching reduces net greenhouse gas emissions in a rice–rapeseed rotation field

With the aim of assessing differentiation of greenhouse gas emissions as manipulated by plastic film mulching (PFM) from paddy field from a year-round perspective, we determined net ecosystem CO₂ exchange (NEE, CO₂ flux), CH₄ and N₂O fluxes from a rice–rapeseed rotation field. PFM and non-mulching (NM) treatments were set from 2014 to 2017 (May 2014 to April 2015, May 2015 to April 2016 and May 2016 to April 2017 were set as Annual 1, Annual 2 and Annual 3, respectively) in Southwest China. Compared with NM, CH₄ emissions were increased by 60.00% (P?<?0.05), 111.54% (P?<?0.05) and 62.07% (P?<?0.05) under PFM in Annual 1, 2 and 3, respectively. Additionally, PFM delayed the peaks of CH₄ fluxes by 5–10 days during rice season. However, PFM did not affect N₂O emissions on the annual basis. PFM reduced the net carbon loss from soil during rice season while had insignificant influence on soil carbon sequestration capacity during fallow and rapeseed seasons. Overall, the mean annual net ecosystem greenhouse gas exchange among three annuals was 32.11% lower under PFM than under NM. Moreover, PFM slightly increased crop yields of both rice and rapeseed. Accordingly, PFM recommended the suitable agricultural management in the rice–rapeseed rotation field for simultaneously alleviating global warming and maintaining crop yields.

     

Protein efficiency ratios and net protein ratios of selected protein foods

As a part of a cooperative study initiated to assess bothin vitro andin vivo protein quality methods, the protein efficiency ratio (PER) and net protein ratios (NPR) of 15 different protein sources were determined. Male weanling Sprague-Dawley rats were fed a 10% protein diet. Fourteen-day NPR and relative NPR (RNPR) values and 14- and 28-day PER and relative PER (RPER) values were calculated for each protein source. When protein quality values were expressed relative to ANRC casein, the 14- and 28-day PER data ranked the protein sources essentially in the same order. RPER values of nonfat dried skim milk (unheated) and tuna were more than 100% that of casein; nonfat dried skim milk (heated), chickpeas, and breakfast sausage were between 50 and 70% of that of casein; and pinto beans and rice-wheat gluten cereal did not support substantial growth of the rat. The NPR method did not always rank the protein sources in the same order as the PER method. For the poor quality proteins, RNPR values were much higher than the RPER values; however, the RNPR and RPER values agreed closely for high quality protein sources.A preliminary report of this work was given at the Annual Meeting of the Federation of American Societies for Experimental Biology, Washington, D.C., March 29–April 2, 1987. Fed. Proc. 1987; 46: 889.     

In vitro amino acid digestibility of food proteins as measured by the digestion cell technique

The digestibility of proteins and individual amino acids of nineteen selected foods was determined by anin vitro assay. Samples were hydrolysed with pepsin for 30 minutes in an acidic medium; the pH was then raised to 7.5 and the mixture poured into the dialysis bag (molecular weight cut-off 1000) of a digestion cell with pancreatin. Digestion products, mixtures of free amino acids and low molecular weight peptides which pass through the dialysis membrane, were collected for 6 hours by sodium phosphate buffer circulation. All proteins from animal sources displayed a digestibility similar to casein, except for breakfast sausage. Vegetable proteins showed intermediate digestibility, except for cereals (lower) or peanut butter (higher). Target amino acids of enzymes were generally more readily hydrolysed. However, compared to other animal proteins, glycine in milk products, valine, isoleucine, methionine and lysine in breakfast sausage and hot dog, and histidine in tuna were more easily released. Overheating of non-fat dried milk not only reduced the lysine digestibility, but also that of methionine, phenylalanine, histidine and cystine. Among vegetable proteins, wheat products were characterized by a relatively greater release of threonine, isoleucine and histidine, and peas by a lower digestibility of methionine and lysine. Proline of soy isolate and isoleucine of pinto bean were resistant to hydrolysis while arginine of pinto beans and of rice-wheat-gluten was easily released.     

Rabadi fermentation of wheat: Changes in phytic acid content andin vitro digestibility

Fermentation of raw as well as autoclaved wheat flour with buttermilk at 30, 35 and 40°C for 6, 12, 18, 24 ad 48h significantly decreased the level of phytic acid; maximum decrease was observed at 40°C for 48h. Starch as well as protein digestibility (in vitro) improved with an increase in temperature and period of fermentation. Phytic acid had a significant (P<0.05) negative correlation with digestibility (in vitro) of both starch and protein ofrabadi.