A Laboratory Method for the Evaluation of Changes in Protein Quality

Menden, E.; Cremer, H. D.

doi:10.1159/000175141

Cited by 3 publications

(1 citation statement)

References 124 publications

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“…How ever, the amount of papain was increased to 4% [3]. Hydrolysis with pancreatin was carried out by a modification of the procedure of Menden and Cremer [17]. Samples containing 200 mg protein(Nx 6.25)were incubated for 17 h at 37°C with 25 mg pancreatin in 10 ml of buffer at pH 8.2.…”

Section: Methodsmentioning

confidence: 99%

The Nutritional Availability of Tryptophan in Foods

Pongpaew¹,

Guggenheim²

1968

Ann Nutr Metab

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Section: Methodsmentioning

confidence: 99%

The Nutritional Availability of Tryptophan in Foods

Pongpaew¹,

Guggenheim²

1968

Ann Nutr Metab

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Dworschák¹

1980

C R C Critical Reviews in Food Science and Nutrition

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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 threatment 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-HN2 group), (2) other types of basic amino acids, and (3) trypotphan (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 int he 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...

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Comparison of In Situ and In Vitro Techniques for Measuring Ruminal Degradation of Animal By-Product Proteins

England

Broderick

Shaver

et al. 1997

Journal of Dairy Science

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Ruminally undegraded protein (RUP) values of blood meal (n = 2), hydrolyzed feather meal (n = 2), fish meal (n = 2), meat and bone meal, and soybean meal were estimated using an in situ method, an inhibitor in vitro method, and an inhibitor in vitro technique applying Michaelis-Menten saturation kinetics. Degradation rates for in situ and inhibitor in vitro methods were calculated by regression of the natural log of the proportion of crude protein (CP) remaining undegraded versus time. Nonlinear regression analysis of the integrated Michaelis-Menten equation was used to determine maximum velocity, the Michaelis constant, and degradation rate (the ratio of maximum velocity to the Michaelis constant). A ruminal passage rate of 0.06/h was assumed in the calculation of RUP. The in situ and inhibitor in vitro techniques yielded similar estimates of ruminal degradation. Mean RUP estimated for soybean meal, blood meal, hydrolyzed feather meal, fish meal, and meat and bone meal were, respectively, 28.6, 86.0, 77.4, 52.9, and 52.6% of CP by the in situ method and 26.4, 86.1, 76.0, 59.6, and 49.5% of CP by the inhibitor in vitro technique. The Michaelis-Menten inhibitor in vitro technique yielded more rapid CP degradation rates and decreased estimates of RUP. The inhibitor in vitro method required less time and labor than did the other two techniques to estimate the RUP values of animal by-product proteins. Results from in vitro incubations with pepsin.HCl suggested that low postruminal digestibility of hydrolyzed feather meal may impair its value as a source of RUP.

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A Laboratory Method for the Evaluation of Changes in Protein Quality

Cited by 3 publications

References 124 publications

The Nutritional Availability of Tryptophan in Foods

The Nutritional Availability of Tryptophan in Foods

Objectives

Comparison of In Situ and In Vitro Techniques for Measuring Ruminal Degradation of Animal By-Product Proteins

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