Essential Amino Acid Pattern Research Articles

Enzymatic Modification of Proteins in Foodstuffs

Soy protein (hydrochloric acid-precipitated fraction) was hydrolyzed with pepsin until the 10% trichloroacetic acid insoluble fraction in the resulting hydrolyzate reached 20% by weight. The hydrolyzate was incubated with a microbial protease (Bioprase) to obtain soy plastein. The soy plastein contained 13.22% nitrogen on dry basis and its constituent amino acid composition was similar to that of the original soy protein. Based on the essential amino acid (EAA) pattern in the soy plastein, its chemical scores were obtained as follows: protein score, 76 (S-containing amino acid); milk score, 67 (leucine); and egg score, 60 (S-containing amino acid). Pepsin and trypsin digestibilities in vitro of the soy plastein were 84.8% and 76.5%, respectively, which were almost the same with those of the denatured soy protein. The bio-utility evaluation in rats fed on the soy plastein diet showed the following results: true digestibility, 90.3%; biological value, 66.8; and average weight gain, 27.4g/20 days which increased to 68.8g/20 days by supplementing amino acids according to the EAA pattern in casein. These values in the soy plastein were also similar to those in the soy protein.

Effect of Level and Pattern of Essential Amino Acids on Nitrogen Retention of Adult Man

Two studies were conducted to determine the effect on nitrogen retention of increasing the dietary intake of essential and semiessential amino acids, patterned as in the poorly balanced protein of corn, when total nitrogen was held constant. Men were fed diets containing approximately 6.00 g nitrogen daily of which crystalline amino acids and diammonium citrate provided 5.50 g and ordinary foods, the remainder. During five experimental periods of study 1, the eight essential and four semiessential amino acids patterned as in corn protein provided 1.10, 2.20, 3.30, 4.40 and 5.50 g nitrogen daily. During the sixth experimental period, 2.20 g nitrogen was also provided by the essential and semiessential amino acids, but the level of isoleucine was increased to that in the FAO provisional pattern. Each increase in the intake of essential and semiessential amino acids was accompanied by an increase in nitrogen retention. Increasing the level of isoleucine to that in the FAO pattern had no effect on nitrogen retention. In the second study, nitrogen balance responses of men fed the corn and egg pattern were compared; equivalent amounts of nitrogen, 2.20, 3.30, or 5.50 g, were supplied by the essential and semiessential amino acids of the two patterns. When the essential nitrogen provided 3.30 or 5.50 g, more highly positive nitrogen balances were obtained when subjects were fed the egg pattern than when they were fed the corn pattern of amino acids.

Pattern of Essential Amino Acid Requirement for Growing Rats Fed on a Low Amino Acid Diet

Requirement pattern of essential amino acids for growing rats was investigated at low dietary level of nitrogen (0.62% of nitrogen) for the basic knowledge of amino acid supplementation to low protein diets. The basal diet contained 3% of essential amino acid mixture and 2% of non-essential amino acid mixture with appropriate amount of the other nutrients. The present pattern indicated relatively lower requirement for lysine and rather higher requirement for phenylalanine, valine and arginine as compared with those of several workers obtained for maximum growth of rats with diet containing sufficient amount of nitrogen. Application of dose response curves of each amino acid for the estimation of the order of the limiting amino acids was suggested.

Isolation and characterization of a cellulose-utilizing bacterium.

A cellulose-decomposing aerobic and mesophilic bacterium has been isolated from soils of sugar cane fields. The terminal dilution method was adapted to isolate a single clone of cellulolytic organism from closely related contaminants. The cultural and physiological characteristics of the isolate were studied, and the organism was identified as a member of the genus Cellulomonas. The isolate excreted cellulase into the menstruum, and it hydrolyzed various cellulosic materials producing cellobiose as the final breakdown product in the menstruum. When sugar cane bagasse was properly treated with alkali and heat, the organism could decompose up to 90% of the initial substrate within 5 days. Amino acid analysis of the cell crop revealed a high content of lysine, and the essential amino acid pattern compared favorably with that of Food and Agricultural Organization reference protein.

Evaluation of amounts and pattern of essential amino acids in plant seeds

Evaluation of amounts and pattern of essential amino acids in plant seeds

Isolation and Characterization of a Cellulose-utilizing Bacterium

A cellulose-decomposing aerobic and mesophilic bacterium has been isolated from soils of sugar cane fields. The terminal dilution method was adapted to isolate a single clone of cellulolytic organism from closely related contaminants. The cultural and physiological characteristics of the isolate were studied, and the organism was identified as a member of the genus Cellulomonas. The isolate excreted cellulase into the menstruum, and it hydrolyzed various cellulosic materials producing cellobiose as the final breakdown product in the menstruum. When sugar cane bagasse was properly treated with alkali and heat, the organism could decompose up to 90% of the initial substrate within 5 days. Amino acid analysis of the cell crop revealed a high content of lysine, and the essential amino acid pattern compared favorably with that of Food and Agricultural Organization reference protein.

Development of a Food Mixture for Infants and Young Children in Brazil

SUMMARY‐The development of food mixtures containing vegetable protein concentrates, minerals, and vitamins represents an important approach to the problem of protein‐calorie malnutrition of preschool children in many parts of the world. In Brazil, soy flour is the most readily available good‐quality protein for this purpose. Protein efficiency‐ratio studies in rats demonstrated that soy flour with a PER value of 1.99 was available in large quantities. Accordingly, a formula containing 19.50% soy flour, 4.50% nonfat milk powder, 32.28% corn starch, 39.00% sucrose, and 4.72% vitamins and minerals was thoroughly tested as an infant food. The PER value of the protein in rats was 2.31. Amino acid assay demonstrated that the protein compared favorably with the essential amino acid pattern of the FAO/WHO reference protein (FAO/WHO, 196.5) except for methionine‐cystine, The formula was well accepted and tolerated by children and adults. Average nitrogen absorption and retention of the formula as the sole food of malnourished children were 72.68 and 23.82%; values for milk protein were 80.17 and 30.13%. Average nitrogen absorption and retention were 63.4 and 22.0% when the formula provided one‐half (15 g) of the daily protein for normal children consuming a typical diet of the region, comparing favorably with values of 69.3 and 21.3% for milk protein.

Supplementation of diets with proteins and amino acids.

WAIE ARE all familiar with the terms high-quality and low-quality as applied to proteins. For the purposes of this presentation, the terms and will be substituted, because these are much more descriptive of the true nutritional differences between these classes of proteins. A high-efficiency protein is simply one that gives, when fed to an animal or a human being, a relatively high yield of tissue protein as measured by growth or nitrogen retention. Examples are the proteins of meat, fish, milk, and eggs. Per unit weight, these proteins consistently show an efficiency two or three times greater, in terms of standard animal growth measurements, than the proteins in most vegetable foods such as the cereal grains.4 The efficiency of a protein is governed primarily by its pattern of essential amino acids, that is, the proportions of these nutrients relative to one another. The nonessential amino acids can be synthesized from metabolic intermediates if they are not present in the right proportions in the dietary protein, but we must take the essential amino acids as we find them in our food. Figure 1 shows the difference in amino acid proportions between a high-efficiency protein (egg) and a low-efficiency protein (wheat protein in white flour). The white flour protein has an inefficient amino acid pattern because the proportion of lysine is too low. Other highefficiency proteins have patterns quite similar to that of egg. Low-efficiency proteins are typically low in one or sometimes two or three essential amino acids.

Biological evaluation of proteins.

Publisher Summary Dietary proteins, through digestion in the gastrointestinal tract, furnish amino acids and polypeptides, which are the raw materials needed to build the body proteins of animals. These body proteins essentially form the matrix of the living system; the centers around which the dynamic equilibria of life develop. This chapter focuses on the biological evaluation of these proteins. The biological value of a protein refers to the amount of nitrogen retained in the body of an animal. A new phase of research on the nutritive value of proteins includes mixtures of amino acids replacing proteins. The pattern of essential amino acids varies with the physiological state of the animal and with the species. The retention of nitrogen in the animal is a function of this pattern. The simplest method used to evaluate nitrogen retention in an animal is to determine the difference between nitrogen intake and nitrogen excreted. This difference, called nitrogen balance, shows whether an animal is maintaining, losing, or gaining nitrogen. Correlations between the nutritive value of a protein and the amino acid composition can be excellent, when the composition represents the pattern of amino acids, which are absorbed into the animal. Along with the evaluation through nitrogen balance, evaluation of proteins through growth and tissue regeneration is also presented.