Bioavailability of lysine in selected foods by rat growth assay

Lysine bioavailabilities in reference protein and 16 test protein diets were estimated using 10 day rat growth assays. A standard growth curve was obtained by feeding 5 diets containing casein, zein and synthetic amino acids ranging in total lysine concentration from 0.3 to 0.7%. Experimental foods were added to the basal diet at the expense of zein and/or synthetic amino acids to provide 2 specific lysine concentrations, i.e., 0.4 and 0.6%. Availabilities were established by comparing growth responses from the test food diets to the regression line of the standard growth data. Availabilities were over 88% for 13 of 16 products. Utilization was poor in pinto beans (73%), rice-wheat gluten cereal (70%), and skim milk powder heated to 100°C for 12 h (66%). Addition of excess lysine (700 mg/100 g diet) to the pinto bean diet did not improve growth response; thus poor digestibility or some unidentified growth inhibitor is indicated.     

Rat bioassays for methionine availability in 16 food sources

Methionine availabilities of 16 test proteins were assessed by comparing ten day rat growth response to the test diets and reference (casein) diets. In a preliminary study, various concentrations of methionine and cystine were fed to determine methionine requirements and effect of excess cystine. Results indicated a methionine requirement of about 550 mg per 100 g diet. Cystine had a sparing affect of 50–55%, i.e., about 300 mg could be used to meet methionine requirements. Further additions of cystine (up to 2.6 times methionine) did not affect rat growth. Methionine availabilities were excellent (88–100%) for 15 of the 16 test foods; only pinto beans (58%) were low, but prior evidence indicates that the poor growth response was due to some factor other than availability.     

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.     

Influence of tryptophan supplementation of soy-based infant formulas on protein quality and on blood and brain tryptophan and brain serotonin in the rat model

A 2-wk feeding study with weanling rats was conducted to investigate theeffects of tryptophan supplementation of soy-based infant formulas on proteinquality and on the levels of blood and brain tryptophan and brain serotoninand 5-HIAA (5-hydroxyindole-3-acetic acid), a metabolite of serotonin. Thepowder and liquid concentrate forms of soy-based infant formulas obtainedfrom four manufacturers were tested. The tryptophan contents of the testsoy-based formulas (10.0–12.3 mg/g protein) were considerably lower comparedto those of human milk (17–19 mg/g protein). The infant formulas were fedas the sole source of protein in diets containing 8% protein, 20% fat, 5%cellulose and adequate amounts of minerals and vitamins. In general, supplementation of the diets containing test formulas with graded levels ofL-tryptophan (0.1 or 0.2%) had no effect on protein quality indices basedon rat growth such as PER (protein efficiency ratio), NPR (net protein ratio)and relative NPR (RNPR), but resulted in significant (p<;0.05) increases inthe concentrations of tryptophan in the plasma and brain, and serotonin and5-HIAA in brain of rats. The increased concentrations of brain tryptophan and5-hydroxyindoles (serotonin + 5-HIAA) in rats fed tryptophan-supplementedformulas compared to those fed unsupplemented formulas support the need forfurther research to investigate the influence of tryptophan supplementationof soy-based infant formulas on tryptophan metabolites and their potentialrelated effects on sleep latency and neurobehavioral developments in infants.     

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.     

Effects of amylose and wheat bran on the levels of blood serum urea nitrogen (BUN), other blood parameters,growth and fecal characteristics in rats

A basal diet (containing 20% soybean protein isolate) was supplemented with limiting amino acids (AA, methionine, threonine and tryptophan); wheat bran (WB, 24.3%); amylose (AM, 10%) or a combination of AA and WB or AM to investigate their effects on the levels of blood serum urea nitrogen (BUN), other blood parameters, growth and fecal characteristics in young rats. After 3 weeks feeding, supplementation of the basal diet with AA or WB resulted in improved growth (gain/food ratio) while the addition of AM had no effect on rat growth. Addition of WB to the basal diet had no effect on BUN while the addition of AA and AM caused about 20 and 12% reduction in BUN values, respectively. Rats fed the AA-AM diet had the lowest BUN values (42% lower than those fed the basal diet). Fresh volume, fresh weight, moisture and dry weight of feces in rats fed the WB diets were about four to five fold higher than in those fed the AM diets. The results suggested that BUN may not be a good predictor of growth and protein quality in diets containing AM or a source of dietary fiber (WB).     

Effect of amino acid supplementation on protein quality of soy-based infant formulas fed to rats

The powder forms of soy-based infant formulas obtained from four manufacturers were fed to weanling rats for two weeks, as the sole source of protein in diets containing 8% protein, 20% fat, and adequate amounts of minerals and vitamins. The relative protein efficiency ratio (RPER) and the relative net protein ratio (RNPR) values (casein + methionine=100) of diets containing unsupplemented formulas were 71–81 and 78–85, respectively. Supplementation of the formula diets with lysine (0.2%), methionine (0.2%), threonine (0.1%) or tryptophan (0.05%) increased the level of the supplemental amino acid in rat serum but generally failed to improve the RPER or RNPR values. Addition of all four essential amino acids to the formula diets, however, caused a marked improvement in their protein quality (RPER or RNPR values=100). The data suggested that proteins in soy-based formulas could be marginally co-limiting in several indispensable amino acids.Presented in part at the 202nd annual meeting of the American Chemical Society, New York City, 25–30 August 1991.     

Limitations of corn (Zea mays) and common bean (Phaseolus vulgaris) diets as protein and calorie sources

Mixtures of 70:30 and 87:13 of corn and beans with or without vitamins, minerals, limiting amino acids and calories were fed to 5-week-old pigs to determine performance and efficiency of utilization. After 12 weeks it was shown that increasing the ratio from 87:13 to 70:30 (corn:beans) was a desirable measure as was the simultaneous supplementation with the other nutrients; individual groups of nutrients resulted in partial improvement in animal performance. None of the diets used was capable of inducing growth similar to the control groups fed a corn:soya diet. Results confirm the importance of total nutrients to obtain increased efficiency of protein utilization; furthermore, diets, such as the corn:bean diets studied, need to be improved in relation to both quality and quantity of protein.INCAP Publication I-1144     

Antinutritional factors in anasazi and other pinto beans (Phaseolus vulgaris L.)

Antinutritional factors of anasazi bean were compared to traditional pinto bean (Phaseolus vulgaris L.). Anasazi beans contained less (p<0.001) soluble and bound condensed tannins compared to pinto beans. No differences (p>0.05) in stachyose and raffinose content were found between the two bean types; verbascose was not detected at all. Significant (p<0.05) differences in lectin content were observed between anasazi and pinto bean. The lectins of anasazi beans were classified as non toxic and those of the pinto beans as toxic types. No differences (p>0.05) in inhibitor activity against human and bovine trypsin and chymotrypsin were found between the two bean types.     

Nutritional evaluation of the supplementary value of low-cost and locally available foods to a poor rice or ragi diet: IV. Calcium utilisation of five ragi-based combinations

The biological availability of calcium from six ragi-based diets was studied in comparison with skim milk and calcium lactate diets. The rats on skim milk and calcium lactate diets had higher absorption values and retention values when compared with the other test diets.Of the six ragi diets tested, the basal diet with the highest cereal content also had the highest level of calcium (215 mg Ca/100 g). Diet 5 was the next best, containing 201.6 mg/100 g. Positive correlations were observed between the calcium content of the diet, and mg calcium absorbed (r=+0.80,P<0.05), mg calcium retained (r=+0.87,P<0.05) or percentage calcium retained (r=0.86,P<0.05). Among the five supplemented ragi-based diets, however, diet 5 was found to result in the highest calcium retention levels when fed to rats. This may have been due to its higher quality protein compared with the other diets. The components of this combination were, in addition to the basal ragi diet, sweet potato, field beans, sesame, drumstick leaves, ground-nut flour, and cotton-seed flour.     

Effect of selected Egyptian cooking methods on faba bean nutritive value and dietary protein utilization 2: Ability of faba bean products to support hemoglobin response in rats

To evaluate the dietary protein utilization and iron deficiency anemia as affected by the faba bean nutrient intake, a bioassay with rats was carried out with different experimental diets containing four faba bean products (stewed beans ‘Medammis’, deep fried dough ‘Falafel’, boiled germinated beans ‘Nabet Soup’ and poured paste ‘Bissara’) widely consumed in the Middle East. Amino acid composition of all faba bean products was determined and compared to raw beans. Severe heat-processing markedly decreased some essential amino acids, especially phenylalanine, cystine, methionine and tryptophan. Protein scores were 24.6, 19.5, 29.2, 28.2 and 35.6 for raw faba beans, ‘Medammis’, ‘Falafel’, ‘Nabet Soup’ and ‘Bissara’, respectively. ‘Bissara’ possessed the highest nutritional value, since it had the lowest GDR value [Grams consumed of product to cover the daily requirements for adult man in protein (63 g) and in energy (2900 kcal)] for the limiting amino acids (L A A). As indicated by P S/150 values [Satisfaction of the daily requirements of the adult man when 150 g (one can content) are consumed of product] for L A A, i.e. methionine+cystine (lowest P S/150 value), the above-mentioned faba bean products cover about 53, 77, 77 and 97% of the daily requirements of adult man in L A A, respectively. Fecal nitrogen excretion increased and true nitrogen digestibility decreased significantly (p<0.01) with the inclusion of ‘Medammis’ in the diet. ‘Nabet Soup’ exhibited the highest true nitrogen digestibility. In contrast, the biological value of nitrogen was apparently unaffected. Highest blood hemoglobin level was found in rats fed diets containing ‘Bissara’, ‘Falafel’ and ‘Nabet Soup’, whereas the addition of ‘Medammis’ in the diet induced a significant (p<0.05) reduction in blood hemoglobin level of fed rats.     

Influence of dietary soybean trypsin inhibitors and DL-ethionine on sulfur amino acid adequacy of diets for young rats

Weanling male Wistar rats were fed 20% protein diets based on casein or either of two combinations of soy protein isolate and ground raw soy providing three levels of soybean trypsin inhibitors (SBTI; 0,448 and 808 mg of trypsin inhibited per 100g of diet respectively). DL-ethionine was included at three levels (0,0.05% and 0.10%) with each level of SBTI. After 4, 8 and 12 weeks ofad libitum feeding, diets containing SBTI without DL-ethionine were associated with decreases in weight gain, feed efficiency, serum cholesterol and serum urea nitrogen. Higher levels of triglycerides, glutamate pyruvate transaminase (SGPT) and altered serum free amino acid levels were also found. Increased dietary levels of DL-ethionine also resulted in deficits in growth and feed efficiency, decreased serum cholesterol, increased SGPT and similar alterations in serum free amino acids. Combination of dietary SBTI with DL-ethionine resulted in even greater growth deficits and serum cholesterol decreases as well as increases in SGPT and serum triglycerides and changes in serum free amino acid levels. Methionine deficiency in the young rats fed SBTI and DL-ethionine was indicated by the changes in serum amino acids and growth deficits. Moderation of some effects over the 12 week test period suggested decreased methionine requirements in the older rats.     

Quick-cooking beans (Phaseolus vulgaris L.): I. Investigations on quality

Soaking three beans cultivars (Phaseolus vulgaris L.: Great Northern, kidney, and pinto) in mixed salt solution (sodium chloride 2.5% + sodium bicarbonate 1.5% + sodium tripolyphosphate 1.0% + sodium carbonate 0.5%) resulted in 80%–85% reduction in cooking time over corresponding controls. Irradiation (-rays) at 500 krads of soaked and dehydrated beans caused a reduction of nearly 50% in cooking time. Water uptake and leaching losses for each treatment during soaking at 22°, 37°, and 45°C were investigated. High temperature (37° and 45°C) and pH (9.0) caused greater water imbibition and total solid loss than at room temperature (22°C). Organoleptic evaluation revealed that quick-cooking Great Northern beans appear to be more acceptable than kidney and pinto beans. Quick-cooking cooked beans had better in vitro protein digestibility than conventionally cooked beans. Phenolic content was found to be inversely related to in vitro digestibility.Utah Agricultural Experiment Station Journal article no. 2481.     

Nutritive value of soybean protein supplemented with purified amino acids and bread

The nutritive value of soybean alone, supplemented with methionine+tryptophan or with bread was investigated. The results showed high Net Protein Utilization (N.P.U.) values for the autoclaved soybean diet (61.5) compared with that of raw soybean supplemented with methionine+tryptophan (57.7). It was found that rats fed the diets of raw soybean supplemented with methionine and tryptophan survived and the growth was improved to some extent.The N.P.U. values of the autoclaved soybean supplemented with methionine and tryptophan (67.4) was in close for that of casein (70.6).The effectiveness of soybean as a supplement to bread at a protein level of 50% was elucidated. The N.P.U. values of the autoclaved soybean supplemented with bread (65.8) was higher than that of either soybean or bread alone which showed the values of 61.5 and 47.0 respectively.     

Nutrient composition and biological evaluation of mesta (Hibiscus sabdariffa) seeds

Two varieties of mesta (Hibiscus sabdariffa) seeds were analysed for their proximate composition. Their protein (18.8–22.3%), fat (19.1–22.8%) and dietary fiber (39.5–42.6%) contents were found to be high. The seeds were found to be a good source of minerals like phosphorus, magnesium and calcium. Their lysine and tryptophan contents were also high. Sulphur containing amino acids were limiting in this seed protein and the chemical score of mesta seed protein was 40 and 57 for AMV-2 and Bhimili-1 varieties respectively. Mesta seed oil is rich in unsaturated fatty acids (70%), of which linoleic acid constituted 44%. Weanling rats were fed with 10% mesta seed protein before and after cooking for 4 weeks. Food intake of animals receiving raw mesta seed diets was significantly lower than those receiving cooked mesta seed diets as well as the casein control diet. Protein and dry matter digestibilities of raw and cooked mesta seed diets were lower than that of casein control diet. Cooking improved the food intake, gain in body weight, dry matter and protein digestibility of mesta seed diets. PER and NPU of cooked mesta seed diets were significantly higher than the corresponding raw diets. These results indicate that cooked mesta seed protein is of relatively good quality.     

Effects of Soybean Fortification on Protein Quality of Tortilla-Based Diets Produced from Regular and Quality Protein Maize

The physiological development of laboratory rats fed with a typical indigenous tortilla diet was studied for two generations. The experiment compared casein control diet and five different types of diets: (1) a diet of tortillas obtained from fresh masa (FM); (2) regular tortillas produced from enriched dry masa flour containing vitamins B₁, B₂, niacin, folic acid, and the microminerals iron and zinc (REDMF); (3) tortillas produced from enriched dry masa flour fortified with 6% defatted soybean meal (FEDMF); (4) tortillas produced from enriched quality protein maize flour (EQPM); and (5) and, tortillas produced from enriched quality protein maize flour fortified with 3% defatted soybean meal (FEQPM). The growth of rats fed FEDMF and FEQPM diets was significantly higher (P<0.05) in both generations than their counterparts fed EQPM, REDMF, or FM diet. Animals fed quality protein maize (QPM) tortilla had the highest protein digestibility, but the FEQPM and FEDMF diets had the highest biological value (BV), net protein utilization (NPU), and protein-digestibility-corrected EAA scores (PDCEAAS). The difference among treatments was more evident in the second-generation rats. The pregnancy rate, number of newborns/litter, litter weight, and newborn survival rate was also higher for rats fed FEDMF, EQPM, and FEQPM diets than their counterparts fed REDMF and FM.     

Protein quality of some Nigerian traditional diets based on the African yambean (Sphenostylis stenocarpa) and pigeon pea (Cajanus cajan)

The protein quality of Nigerian traditional diets based on the African yambean (AYB) and pigeon pea (PP) were performed by in vivo and in vitro bioassays. The individual foods were processed, cooked, dried and mixed to resemble the traditional diets. Weanling male Wistar rats (45–55 g) were used for the bioassay. The rats were fed ad libitum for 35 days of which 28 days were for growth and 7 days for N-balance. All the eleven diets including casein (control) provided 1.6 g N/100 g diet. The parameters tested include PER, growth, N-balance, BV, NPU and apparent digestibility (AD). The rats fed the AYB diets, except AYB: Agidi (Ag), showed superiority in most of the parameters tested. There were significant positive correlations between PER and NPU (r=0.925;p<0.001); PER and AD (r=0.908;p<0.001); PER and body weight gain (r=0.969;p<0.001). The in vitro protein digestibility of the diets was significantly correlated (r=0.80;p<0.01) with the in vivo apparent digestibility. These parameters were used to rank the various diets. Crayfish protein was a better supplement to legume/cereal or legume starchy staple mixtures than leguminous oil seed. However, supplementation of PP: steamed corn (SC) diet with crayfish did not prove beneficial. The result showed that diets based on the African yambean, an under-exploited legume, are nutritious. The need for its reintroduction into the fare of the populace through increased production and appropriate processing technology is stressed. The results of this study can form a base for the standardization of Nigerian diets based on these legumes.     

The USDA trypsin inhibitor study. IV. The chronic effects of soy flour and soy protein isolate on the pancreas in rats after two years

In two year feeding trials, histologic changes in the pancreas of the Wistar rat were evaluated after chronic dietary exposure to raw and heated, dehulled, defatted soy flour and soy protein isolates which provided a range of trypsin inhibitor (TI) concentrations from 93 to 1271 mg/100 g diet. Also investigated was the nutritional interaction of level of dietary protein with the development of pancreatic pathology. Graded levels of TI were achieved from mixtures of raw and heated soy flour or protein isolate. Dietary protein levels were 10%, 20%, and 30%; the two higher levels obtained in some diets through casein supplementation. A total of 26 diets, including casein controls, were fed to groups of 40 male rats. Growth rates with these diets were commensurate with protein quality and level. Mortality rates tended to be slightly greater in the higher protein diets, and rats fed only raw soy as a source of protein survived well.Two lesions, nodular hyperplasia (NH) and acinar adenoma (AA) constituted the major pathological findings in the pancreas, and the incidence rates of both were positively associated with the concentration of dietary TI. The incidences of pancreatic NH and AA compared to those of the corresponding casein control were significantly elevated in rats fed heated soy flour supplying 10% protein and the lowest level of TI investigated (93 mg/100 g diet). At low levels of TI (215 mg/100 g diet), supplementation by casein to raise the concentration of protein from 10% to 20% and 30% reduced the frequency of NH and AA. When the dose-response data for NH and AA was linearized by plotting the probit of percent incidence against log of TI concentration per gram of dietary protein, the response to soy flour and soy protein isolate was not significantly different. Numerous lesions commonly found in the aging rat were diagnosed, and modulation of their rate of occurrence by nutritional factors associated with the diets was apparent in some instances.Reference to a company and/or product named by the Department is only for purposes of information and does not imply approval or recommendation of the product to the exclusion of others which may also be suitable.     

Cassava-soy weaning food: Biological evaluation and effects on rat organs

Weaning food was formulated using a cassava product, `Tapioca' (TAP), supplemented with roasted – sproutedsoybeans (SS), with and without additional (10%)malted sorghum flour (MS). Biological evaluation wascarried out on the formulations using 4–5 week oldweanling albino rats, with Cerelac (a commercialmaize-milk weaning food) as the control diet. Therewere increases in growth rate of rats fed with boththe test and control diets. There were no significant(p > 0.05) differences between the test diets andcontrol diet in true digestibility values. Thebiological value (BV) and net protein utilization(NPU) values for the formulated diets were above therecommended minimum values. The weight of organs(small intestine, pancreas, liver and heart) of ratsfed TAP + SS and TAP + SS + MS based diets were nothigher than those of organs of rats fed Cerelac. Itwas concluded that cassava products could potentiallybe employed successfully in the preparation of weaningfoods of comparable quality to available commercialbrands.     

Evaluation of the protein quality of rice supplemented with bean or crayfish in rats

Weanling male rats (45–60 g) were used to compare the supplemental effects to rice protein of bean or crayfish protein. Rats were fed various combinations of rice plus bean (B) or crayfish (C) to provide 1.6 g N/100 g of the daily diet for 28-day growth studies and a 7-day N balance period. Five different diets were fed. Six rats were assigned to each diet on the basis of body weight. Combinations of R:B of 80:20 and of R:C of 80:20 produced food intake, weight gain, PER, N intake, digested and retained N; and liver weight values that were comparable. However, increasing C to 30% of the dietary protein led to reduced value for food intake, weight gain, PER, N intake, digested and retained N, BV, NPU, and liver weight when compared with values obtained when B was increased to 30% (P<0.05). The results appear to indicate that, above a certain level of supplementation, brown bean protein is superior to crayfish as a supplement to rice protein.