Food Proteins: Interactions and Functionality

There are many kinds of the chemical scoring methods to estimate the nutritive value of protein in food and diet. Recently, the new chemical scoring method, which is called “Amino Acid Score”, was proposed by the Joint of FAO and WHO Energy and Protein Requirement Committee in 1973.Therefore, the amino acid score of protein consumed by the Japanese people was calculated from the data of the National Nutrition Survey conducted in Japan in 1971.The results are shown as follows:In comparing the amino acid pattern of the Japanese diet with the FAO's new reference pattern of amino acid, sonly threonine was the limiting amino acid among the eight essential amino acids. Thus the amino acid score of the Japanese diet based on the amounts of all essential amino acids was 98 and the most limiting amino acid was found to be threonine. But the score based on the amounts of three amino acids (lysine, tryptophan and the total of sulfur containing amino acids) calculated was 100.

To investigate the amino acid composition and content of common vegetables in Fujian Province, and to evaluate their nutritional value. Selecting 25 kinds of common vegetables from Fujian, composition of amino acid in protein was determined according to GB/T 5009. 124-2016 national food safety standard-determination of amino acid. Evaluating method for nutritional value in food protein: to evaluate nutritional evaluation of vegetable protein by fuzzy recognition, essential amino acid index(EAAI), ratio coefficient(RC) and score ratio coefficient(SRC). Kinds of protein amino acid in vegetables were abundant, including 17 kinds of amino acids. Total amino acid content was from 224. 3 to 16202. 1 mg/100 g edible, the ratio of essential amino acids was from 0. 17 to 0. 44, RC was from 0. 13 to 1. 82, SRC was from 50. 56 to 82. 18, the first limiting amino acids of vegetable protein were methionine and cystine. There are various kinds of protein amino acids in vegetables, including all essential amino acids of human body. There is big difference among different kinds of amino acids.

1. The relationship of the amino acid constitution of a protein, or of the protein component of a food product, to its nutritive value for the growing rat can be best revealed, in the absence of accurate values for the amino acid requirements, by computing for each protein, or protein mojety, the percentage deviations of the contents of each essential eamino acid, expressed per 16 gm. of nitrogen, from the corresponding contents of a protein mixture, such as that of whole egg. thart is almost completely digestible by the rat and utilizable in adolescent metabolism. This has been done for a series of twenty-eight proteins and protein mixtures for which satisfactory analyses have been secured for all of the essential amino acids. 2. From such computations, the essential amino acid limiting the nutritive efficiency of the protein will be revealed as that one whose percentage deficit from that of the standard protein (whole egg) is the greatest, due consideration being given to the limiting amino acids thus indicated agree with those determined in feeding experiments with only one or two exceptions. 3. The proteins of foods may be ranked in the order of decreasing nutritive efficiency on the basis of increasing percentage deficits (as above defined) in their respective limiting essential amino acids. These percentage deficits are highly correlated (r = -0.86) with the corresponding biological values determined by the nitrogen metabolism method. Little or no correlation exists between the chemical ratings of th proteins and their digestibility by the growing rat. 4. The biological value of a protein (y) may be roughly estimated from its maximum percentage deficit in an essential amino acid (x) by the equation: = 102 - 0.634x. 5. However, there are known instances in which the biological value of a protein, or protein mixture, and its chemical rating do not agree, for various reasons discussed in the text. 6. In particular, the nutritive value of cereal proteins may be greatly impaired bt the application of heat with no demonstrated alteration in their content of the essential amino acids. 7. A basis for prediciting the effect of heat on the biological value of a food protein is suggested.

1. The relationship of the amino acid constitution of a protein, or of the protein component of a food product, to its nutritive value for the growing rat can be best revealed, in the absence of accurate values for the amino acid requirements, by computing for each protein, or protein mojety, the percentage deviations of the contents of each essential eamino acid, expressed per 16 gm. of nitrogen, from the corresponding contents of a protein mixture, such as that of whole egg. thart is almost completely digestible by the rat and utilizable in adolescent metabolism. This has been done for a series of twenty-eight proteins and protein mixtures for which satisfactory analyses have been secured for all of the essential amino acids. 2. From such computations, the essential amino acid limiting the nutritive efficiency of the protein will be revealed as that one whose percentage deficit from that of the standard protein (whole egg) is the greatest, due consideration being given to the limiting amino acids thus indicated agree with those determined in feeding experiments with only one or two exceptions. 3. The proteins of foods may be ranked in the order of decreasing nutritive efficiency on the basis of increasing percentage deficits (as above defined) in their respective limiting essential amino acids. These percentage deficits are highly correlated (r = -0.86) with the corresponding biological values determined by the nitrogen metabolism method. Little or no correlation exists between the chemical ratings of th proteins and their digestibility by the growing rat. 4. The biological value of a protein (y) may be roughly estimated from its maximum percentage deficit in an essential amino acid (x) by the equation: = 102 - 0.634x. 5. However, there are known instances in which the biological value of a protein, or protein mixture, and its chemical rating do not agree, for various reasons discussed in the text. 6. In particular, the nutritive value of cereal proteins may be greatly impaired bt the application of heat with no demonstrated alteration in their content of the essential amino acids. 7. A basis for prediciting the effect of heat on the biological value of a food protein is suggested.

Contents 17.1 Introduction 287 17.2 Sample Preparation for the Analysis of Seafood Essential Amino Acids 28817.2.1 Sample Preparation for Free Essential Amino Acid Analysis 288 17.2.2 Sample Preparation for Total or Hydrolyzed Essential AminoAcid Analysis 289 17.3 Seafood Essential Amino Acid Analysis 29017.3.1 High-Performance Liquid Chromatographic Methods 291 17.3.1.1 Cation Exchange Chromatography 291 17.3.1.2 Reversed-Phase High-Performance Liquid Chromatography 29217.3.2 Gas Liquid Chromatographic Methods 298 17.3.3 Capillary Zone Electrophoretic Methods 298 17.3.4 Mass Spectrometry 29917.4 Conclusions 300 References 30017.1 Introduction Amino acids are the basic components of the muscle protein structure of seafood. However, not all proteins have the same nutritional value, because protein quality strongly depends on its amino acid composition and digestibility.1 Fish and, in general, seafood proteins are considered as highquality proteins because of their balanced content in amino acids, especially in all the essential amino acids necessary for physical and mental well-being. Amino acids may also be found in free form, which contribute to sh taste and indirectly to aroma 2,3 by generation of volatilecompounds through Maillard reactions and Strecker degradations.4 Branched-chain essential amino acids (valine, isoleucine, and leucine), sulfur-containing amino acids (methionine and cystine/cysteine), and aromatic amino acids (phenylalanine and tyrosine) are the most important from this point of view. Free amino acids initiate important changes at early postmortem and during storage and can be very useful as quality indices of processing and storage.5-10us, the analysis of essential amino acids in seafood is important for the evaluation of both the nutritive value and the sensory quality of seafood.

The impact of protein nutrition upon serine biosynthesis and catabolism in rat liver was investigated by determining the activity of two key enzymes in the pathway of serine metabolism, phosphoglycerate dehydrogenase on the pathway leading from pyruvate to serine, and serine dehydratase on the catabolic way transforming serine to pyruvate.It was found that increasing the protein content of the diet induces serine dehydratase and represses reciprocally phosphoglycerate dehydrogenase. For casein, a protein of high nutritive value, the activities of both enzymes are at equilibrium at the 20% dietary protein level, which is near the optimum casein level for rat growth. With gluten, a protein of low nutritive value, equilibrium is reached at almost the same dietary protein level (22%), although optimal growth is not attained prior to the 50% dietary protein level. In this comparison, there is no correlation between the nutritive value of the proteins (growth measurement) and their regulatory action on the two enzymes tested. Extension of the studies to other proteins, such as egg, showed however that egg, the protein of highest nutritive value, has also the greatest effect on enzyme regulation. The conclusion is that a certain relationship between nutritive value and enzyme‐regulatory action exists, but that the determining factors (amino acids) are partly different. The role of individual dietary amino acids upon serine metabolism was therefore investigated. It was first shown that only the essential amino acids as a group were responsible for the reciprocal induction and repression of the two enzymes. By feeding amino acid mixtures lacking one essential amino acid at a time to the animals, we established subsequently that four essential amino acids only, i.e. methionine, tryptophan, threonine and valine are active in regulating the two enzymes. Cystine influences only phosphoglycerate dehydrogenase. The enzyme‐regulating action of proteins can thus be expressed in terms of their content in “active” amino acids, whereas their nutritive value depends on the presence of all essential amino acids. The similar behaviour of casein and gluten in enzyme regulation in spite of the great difference in nutritive value is thus fully explained, since the deficient amino acid in gluten, i.e. lysine, is not active in the regulation of the two enzymes studied.Finally a coherent theory for the reciprocal serine dehydratase repression and phosphoglycerate dehydrogenase induction in rat liver by lack of an “active” amino acid is proposed.It is based on the presence of a posttranscriptional represser which both inhibits messenger translation and promotes messenger degradation, and on the fact that the translation of small proteins is less impeded by amino acid deficiency than that of bigger polypeptide chains.

Amino Acids, Survey

The interaction between glucose and essential amino acids at 100 degrees C at pH values ranging from 4.0 to 12.0 was investigated by monitoring the disappearance of glucose and amino acids as well as the appearance of brown color. Lysine was the most strongly destroyed amino acid, followed by threonine which induced very little additional browning as compared with that undergone by glucose. Around neutrality, the nonenzymatic browning followed pseudo-zero-order kinetics after a lag time, while the glucose and amino acid losses did not follow first-order kinetics at any of the pH values tested. Glucose was more strongly destroyed than all of the essential amino acids, the losses of which are really small at pH values lower than 9.0. However, glucose was less susceptible to thermal degradation in the presence of amino acids, especially at pH 8.0 with threonine and at pH 10.0 with lysine. The contribution of the caramelization reaction to the overall nonenzymatic browning above neutrality should lead to an overestimation of the Maillard reaction in foods.

The article presents the results of determining the amino acid composition of pork with quality defects, such as PSE, DFD, RSE, RFN and PFN. Meat is one of the traditional sources of high-grade protein, the nutritional and biological value of which depends on the ratio of essential and non-essential amino acids that make up these proteins. The nutritional value and amino acid composition of meat proteins are influenced by various factors, such as the type of animal and breed, gender and age, feeding, storage conditions and others. As part of the implementation of the Food Security Doctrine of the Russian Federation, much attention is paid to improving the quality and rational use of meat and other slaughter products, including those with quality defects such as PSE and DFD. In addition to defects PSE (pale, soft, exudative) and DFD (dark, hard, dry) for pork, there are three more categories: PFN — pale, hard, non-exudative (pH 5.58); RSE — red, soft, exudative (pH 5.67); RFN — red, hard, nonexudative (pH 5.71). The purpose of the research was to evaluate the amino acid composition of pork with quality defects. The research was carried out in the conditions of the educational and research center for the examination of food and animal feed of the St. Petersburg State University of Veterinary Medicine in the period 2021-2022. The materials for the study were 66 samples of pork of various quality categories (11 samples of each category). For the tests, point samples were taken from different muscle groups, then a combined sample was made and sample preparation was carried out according to the M method-04-94-2021 "Determination of amino acids in food products". The amino acid composition of the studied samples was determined according to the M method-04-94-2021 "Determination of amino acids in food products" on the device "Kapel-105M" (GC "LUMEX"), with an autosampler and an automatically switched polarity. As a result of the conducted research, it was found that the content of interchangeable and essential amino acids in pork of different quality categories depended on the type of amino acids and the quality category of pork. It should be noted that information about the amino acid composition of pork with quality defects should be taken into account in the production of meat products at processing plants.

The nonenzyme browning involves the thermal decomposition of sugars, the caramelization, the decomposition of oxi‐acids, the so called “Maillard reaction” between amino acids and carbohydrates, the reaction between oxidized fats and proteins, and those alterations which take place by the alkaline treatment of proteins. The Maillard reaction is of secondary importance in the case of foodstuffs and fodders with low carbohydrate contents (meats, meat meal, fish meal). By the heat treatment, the sulphur‐containing amino acids of proteins (cystine, methionine) are damaged primarily because of oxidation, but the decrease in the amount of threonine, serine, tryptophan, and lysine is observable too. According to the formation of enzyme resistant cross‐links, the in vitro and in vivo digestibility of protein decreases after the heat treatment and the communication with oxidized fats. Besides the amino acids mentioned, the possibility of enzymatic break‐off of leucine and isoleucine is reduced too. In the course of the heating of proteins the occurance of racemization has to be considered too (formation of alloisoleucine). The basic mechanism of the reaction between sugars and simple amino acids is already essentially explained: amino‐acids break off after the formation glycosilamines and Amadori products but they are linked irreversibly to some, partly unsaturated decomposition products of sugars, types of 6 and 3 carbon atoms. The decrease in the biological usability of amino acids starts already with the Amadori products. The reactivity of the single amino acids depends on the number of carbon atoms, on the basicity, and on the polarity of the amino acid molecule. The especially highly reactive amino acids of proteins are (1) the essential lysine (because of its 6‐NH2 group), (2) other types of basic amino acids, and (3) tryptophan (because of the lability of the indole ring), methionine, cystine and threonine. In the Maillard reaction of tryptophan the —NH— group of the indole ring is involved too. The Maillard reaction is highly influenced by the pH of foodstuffs or other agents. The reduction of pH which may be performed by the increase of fermentation in the baking industry, lessens the decomposition of lysine and tryptophan in proteins. The raise of pH in basic domain enhances the Maillard reaction up to a maximal value but a decrease may be observed when the pH is raised further on. In foodstuffs and in other solid protein‐carbohydrate systems the increase of the moisture content generally enhances the Maillard reaction, the sensibility of the single amino acids to the changes in the moisture content is different. In the case of the alkaline treatment of proteins, we must reckon not only with the decomposition of single amino acids, first of all that of cystine by beta‐elimination, but with the formation of some amino acid derivatives as lysinoalanine, lanthionine, and in ornithinoalanine too. Presently lysinoalanine is of toxicological importance as proved by experiences on rats. The isomerization of essential amino acids may appear too during the alkaline treatment of proteins and this bears a reducing effect on the nutritive’ value.

Effects of Severe Alkali Treatment of Proteins on Amino Acid Composition and Nutritive Value

The uptake of thirteen essential amino acids by mouse LS cells in suspension culture was determined by bacteriological assay methods. Chemostat continuous-flow cultures were used to determine the effect of different cell growth rates on the quantitative amino acid requirements for growth. The growth yields of the cells ( Y = g cell dry weight produced/g amino acid utilized) were calculated for each of the essential amino acids. A mixture of the non-essential amino acids, serine, alanine and glycine increased the cell yield from the essential amino acids. The growth yields from nearly all the essential amino acids in batch culture were increased when glutamic acid was substituted for the glutamine in the medium. The growth yields from the amino acids in batch culture were much less at the beginning than at the end of the culture. The highest efficiencies of conversion of amino acids to cell material were obtained by chemostat culture. When glutamic acid largely replaced the glutamine in the medium the conversion of amino acid nitrogen to cell nitrogen was 100 % efficient (that is, the theoretical yield was obtained) at the optimum growth rate (cell doubling time, 43 h). The maximum population density a given amino acid mixture will support can be calculated from the data. It is concluded that in several routinely used tissue culture media the cell growth is limited by the amino acid supply. In batch culture glutamine was wasted by (1) its spontaneous decomposition to pyrrolidone carboxylic acid and ammonia, and (2) its enzymic breakdown to glutamic acid and ammonia, but also glutamine was used less efficiently than glutamic acid. Study of the influence of cell growth rate on amino acid uptake rates per unit mass of cells indicated that a marked change in amino acid metabolism occurred at a specific growth rate of 0.4 day -1 (cell doubling time, 43 h). With decrease in specific growth rate below 0.4 day -1 there was a marked stimulation of amino acid uptake rate per cell and essential amino acids were consumed increasingly for functions other than synthesis of cell material.

The purpose of this study is to compare the effect of non-essential amino acids and essential amino acids on in vitro maturation and development of reconstructed embryos of porcine oocytes. The oocytes were divided into four groups, the IVM medium of porcine were added 1% the essential amino acids, 1% non-essential amino acids, both 1%essential and nonessential amino acids, And non amino acids as control. The oocytes were cultured for 44h, and statistics maturation rate. Embryo culture medium (NCSU-23) were added 1% the essential amino acids, 1% non-essential amino acids, both 1%essential and nonessential amino acids, And free amino acids as control. The reconstructed embryos were cultured to 7d, and statistics blastocysts rate. Each experiment was repeated three times. The results show that added any kind of amino acids in IVM medium will improve the oocytes maturation rate (P<;0.05), and the oocytes maturation rate of non-essential amino acid group was significantly higher than other groups (P<;0.05); The non-essential amino acids in NCSU-23 can significantly improve the reconstructed embryonic blastocysts rate (P<;0.05), while the essential amino acids or both essential and non essential amino acids in NCSU-23 leads blastocysts rate decreased (P<;0.05). The studies have shown that there are some different of the effect of essential and non essential amino acids on porcine oocytes IVM and reconstructed embryos development.

A promising growth vector of food protein production in the context of the Russian Federation's food sovereignty security is the use of microbial synthesis. Taking into consideration the proven promising use of biotechnological processes in the production of alternative protein sources, modern scientific research is focused, among other issues, on improving the technology of obtaining food microbial protein using a variety of substrates and strains-producers, as well as evaluating the consumer properties, food, biological value and safety of such products. The purpose of the research was to study and comparatively evaluate protein concentrate (PC) from bacteria Methylococcus capsulatus and basic food of animal and plant origin within the development of the technology of optimal in nutritional and biological value PC production. Material and methods. Analysis of the nutritional and biological value of PC obtained from denucleinized and purified from cell walls biomass of methanoxidizing bacteria Methylococcus capsulatus (strain GSB-15) was carried out on 46 indicators, including estimation of protein content and amino acid composition, fat content and fatty acid composition, ash and moisture. Biological studies based on measuring of net protein ratio / net protein utilization were performed on 28 growing (between 25-50 days of life) male Wistar rats. Rats in the control group (n=14) received a semi-synthetic casein diet with a protein content of ~12% in calories, the test group (n=14) received a diet including an equivalent amount of PC protein. Body weight, feed intake, and fecal and urine nitrogen losses were measured during the experiment. The biological value and digestibility of protein were judged by coefficients of protein efficiency ratio, net protein ratio, true protein digestibility, true protein biological value, true net protein utilization. Results. The nutritional value study of PC showed high protein content - 69.0%, the share of fat, moisture and ash, accounted for 0.17, 9.5 and 14.4%, respectively. The carbohydrate content was 7.0% (of which mono- and disaccharides were <0.1%). The results of a comparative assessment of Methylococcus capsulatus protein amino acid profile and basic food of animal and plant origin showed a balanced content of the most amino acids, the level of which is comparable with the protein of chicken egg, which is traditionally a standard of quality of complete protein. At the same time, the content of the essential amino acid tryptophan in PC was an order of magnitude lower than in chicken egg protein; the content of this amino acid in PC is comparable with incomplete plant proteins (sunflower, flax, rapeseed). The results of the biological value evaluation of the Methylococcus capsulatus protein in the experiment on rats indicate a relatively low biological value of the microbial synthesis protein, that is caused, most likely, by tryptophan deficiency. Rats of the test group had a significant decrease in body weight gain, feed/protein intake, coefficient of protein efficiency ratio, coefficient of net protein ratio, true protein biological value, true net protein utilization. Conclusion. The results of a comparative evaluation of PC from methanotrophic bacteria Methylococcus capsulatus denucleinized biomass and basic food of animal and plant origin indicate its relatively high nutritional value. However, the characteristics of this PC sample were not optimal in regard of protein biological value by reason of tryptophan deficiency. A single amino acid deficiency is not a valid argument for not using microbially synthesized protein in human nutrition, considering the capabilities of the modern food industry, including ways to enrich foodstuffs with missing components. In addition, there is every cause to believe that adjusting the hydrolysis technology used in the production of PC will allow to eliminate the essential amino acid loss, thereby increasing the biological value of this product.

Muscle Kinetics and Exercise: Any Advantages of Dietary Proteins