Limiting amino acids in raw and processed amaranth grain protein from biological tests

Amino acid supplementation studies with young rats were carried out using raw and processed amaranth grain (A. cruentus) of dark- and cream- or light-colored seeds. The results of various studies repeatedly indicated that threonine is the most limiting amino acid in raw and processed, dark and cream-colored grain. Protein quality as measured either as NPR or PER was improved by threonine addition alone or with other amino acids and decreased liver fat to values similar to those measured with casein. This finding contradicts the reports that state that leucine, determined by chemical score, is the most limiting amino acid. Leucine addition alone or with other amino acids did not improve protein quality. The study confirmed cream-colored grain to be nutritionally superior to dark grain and that properly processed grain, light- or dark-colored, has higher protein quality than raw grain.INCAP Publication I-1525     

Protein content and amino acid profile of some wild leguminous seeds

Seeds of 28 wild growing legumes of India were analysed for their protein content and amino acid compositions. A wide variation was observed in protein contents (18.3 to 50.9%). The amino acid composition and protein content of some of these seeds were in close proximity to that of soybean; however, some legumes registered a higher level of certain amino acids and protein as compared to the latter.     

Amino acid profiles of some under-utilised seeds

Twenty-three seeds of different botanical families growing in India were analysed for their protein content and amino acid compositions. They showed a wide variation in their total protein (8.0 to 42.7%). Some of them were comparable and some were even better than popular food legumes such as kidney bean and chick-pea in protein levels and amino acid compositions.     

Protein and amino acid composition of some wild leguminous seeds

The seeds of five different species ofAcacia, twoAlbizzia, twoErythrina and two species ofMucuna were analysed for their protein and amino acid composition. Some of these seeds are comparable to a popular food legume,Cicer arietinum, in protein and amino acid composition.     

Distribution of seed protein fractions and amino acids in different anatomical parts of chickpea (Cicer arietinum L.) and pigeonpea (Cajanus cajan L.)

Studies on protein fractionation in seed coat, embryo, cotyledons and whole seed were made to observe the differences, if any, between chickpea and pigeonpea. Results indicated that globulin was the major fraction of embryo and cotyledons of these legumes. Seed-coat nitrogen was observed to be mostly comprised of nonprotein nitrogen and glutelin fractions and thus differed from other components in both chickpea and pigeonpea. The albumin fraction of cotyledons of both crops had the highest concentration of sulphur amino acids, methionine and cystine. Glutelin contained a considerably higher concentration of methionine and cystine than did globulin in chickpea and pigeonpea. This suggests that lines with higher glutelin should be identified to improve their protein quality. The amino acid compositions of different seed components did not show large differences between these two pulse crops.Submitted as JA no. 180 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).     

Irradiation and germination effects on phytate,protein and amino acids of soybean

Influence of irradiation (0.05–0.20 kGy) and germination (24–120 hours) in distilled and tap water on phytate, protein and amino acids of soybean, was studied. Phytate values significantly decreased with increasing germination period and irradiation dose (P<0.01). Irradiation independently decreased the original phytate (212.0 mg/100 g) to a range value of 205.0–190.0 mg/100 g depending upon dose level. Germination of unirradiated seeds for 120 hours in distilled and tap water lowered the phytate to 55.0 and 94.9 mg/100 g (74.1 and 55.2% reduction) respectively. Maximum destruction of phytate to levels of 20.5 and 50.9 mg/100 g (90.3 and 76.0% reduction) occurred during germination of 0.20 kGy samples for 120 hours in distilled and tap water respectively. Total protein content significantly increased during germination (P<0.05) and the increase was more in tap than distilled water. Germination for 120 hours of untreated seeds in tap water increased the essential and decreased non-essential amino acids while in the 0.10 kGy sample, increases in both cases were observed.     

Effect of a Bangladeshi home-cooking procedure on the amino acid content,trypsin inhibitor activity and in vitro digestibility of some legume seeds

Raw and cooked samples of cultivars ofLens esculenta (Lentils),Pisum sativum (peas),Phaseolus vulgaris (beans),Phaseolus aureus (navy beans)Cicer arietnum (gram), andLathyrus sativus (dhal) as well as precooked commercial products were analysed for amino acids, trypsin inhibitor activity and in vitro protein digestibility. Of the fifteen samples used in the study one lentil sample, one pea sample, two gram samples and one sample of khesari dhal were from Bangladesh, one gram sample was from Sri Lanka. The other samples were obtained either in shops in Norway or from an industrial firm. The latter were also obtained precooked and dried. The two samples obtained in shops were used with hull and dehulled.Neither cooking by a Bangladeshi household procedure nor industrial precooking and drying had any effect on the amino acid contents of the samples.Cooking and precooking reduced the trypsin inhibitor activity of the raw samples more when the original activity was high then when it was low. The inhibitor activity was similar between samples after cooking.Cooking and precooking and drying increased the in vitro protein digestibility in all samples except in the lentils in which the digestibility was reduced.In the raw samples protein digestibility was negatively correlated with the trypsin inhibitor activity.     

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.     

Nutritional evaluation of some commercial wheat varieties grown in Pakistan

The nutritive value of some commercial wheat varieties grown in Pakistan was measured chemically, including amino acid analysis, and biologically in N-balance experiments with growing rats. The protein content ranged from 13.2% in Punjab-83 to 16% in Barani-83. Lysine per 100g protein varied between 2.46 and 2.75%. The available carbohydrate ranged from 67.3 to 74.7%. Iron content was highest in Sonalika while the concentration of zinc and manganese was highest in Sarhad-82. The protein digestibility (TD), biological value (BV) and net protein utilisation (NPU) varied between 92–95%, 56–68% and 53–65% respectively. Level of wheat protein was negatively correlated with available carbohydrate (r=–0.93), lysine per unit protein (r=–0.67) and BV (r=–0.76). The lysine content (g/16gN) of commercial wheat varieties showed a positive correlation (r=+0.95) with the BV. The protein quality was lowered in varieties having higher content of protein.     

The use ofEscherichia coli mutants to measure the bioavailability of essential amino acids in foods

The -galactosidase-based assay for lysine developed by Tuffnell & Payne was used to measure the bioavailabilities of cyst(e)ine, methionine, threonine and tryptophan in pronase digests of 17 foods. The digests were assayed by estimating the -galactosidase synthesis responses of fiveEscherichia coli mutants, each requiring one of the respective amino acids for protein synthesis. Deletion mutants were used whenever possible in order to ensure strain stability. Single digests of each food were assayed with 3 or 4 separate cultures of each mutant and the results were compared with those from the corresponding chemical assay. Omitting the anomalously low values for one food, the rank correlation coefficients of the bio- and chemo-assay values were 0.61 (cysteine), 0.91 (lysine), 0.95 (methionine), 0.64 (threonine) and 0.85 (tryptophan). Mean (± S.D.) relative amino acid bioavailabilities (casein = 100%) for the 17 foods were: cysteine, 53±23; lysine, 90±10; methionine, 95±18; threonine, 89±13; and tryptophan, 89±25. The cysteine mutant appeared to give unusually low bioavailability values except for the milk products. These amino acid mutants afford a rapid method for assaying the bioavailabilities of at least four of the five amino acids studied.     

Changes in carbohydrate and nitrogenous components and amylase activities during germination of grain amaranth

Grain amaranth (Amaranthus hypochondriacus), Yercaud local variety, was soaked overnight and germinated for 192 h taking the soaked grains as the zero time (0 h) sample. The changes in the activities of - and -amylases, starch, sugar, protein and lysine contents during germination are reported. Activity of -amylase was high in the 0 h soaked grains, while -amylase activity was high in 72 h germinated grains. The joint action of the amylases resulted in a decrease of starch content from 0 to 192 h in germinated grains and an increase in total sugars during the initial period of germination.Protein nitrogen was found to decrease from 48 h to 192 h accompanied by an increase in free amino acid and non-protein nitrogen contents. Total lysine content was found to be increased by 31% in 24 h germinated grain amaranth. Protein fractionation of raw, soaked and 24 h germinated grain amaranth showed that the distribution of different types of proteins varied during germination of the grains. An increase of water soluble protein content was noticed in 24 h germinated grains.