Protein nutritional effects

Eleven controlled diet and environment experiments have been designed in a way that can be used to investigate the effects of protein nutrition and heat and/or water stress on diet-tissue A N. Laboratory rats were raised on purified, pelletized diets in which the isotopic composition of proteins, lipids and carbohydrates were well characterized and their proportions accurately and precisely measured (Ambrose and Norr 1993). Four experiments involved manipulation of temperature and/or water availability. Of these four experiments, one used a diet with high (70%) protein concentrations and heat/water stress (36°C) and three used normal (20%) protein concentrations. Seven experiments were conducted at normal temperature (21°C) with water ad libitum. Of these seven experiments, two used diets formulated with veiy low protein (5%), three with normal protein and two with high protein concentrations. 

Kahn, L. P., Kyriazakis, I., Jackson, F. and Coop, R. L. (2000). Temporal effects of protein nutrition on the growth and immunity of lambs infected with Trichostrongylus colubriformis . International Journal for Parasitology, 30, 193-205. 

Complete removal of procyanidin is not necessary to overcome anti-nutritional effects. Removal of most procyanidin or addition of sufficient protein will overcome anti-nutritional effects of procyanidins. Small concentrations of procyanidin can be easily overcome by adding protein. 

Dworschak, E. 1980. Nonenzymatic browning and its effect on protein nutrition. CRC Crit. Rev. Food Sci. Nutr. 12, 1-40. 

Nutritional Effects Due to the Blockage of Lysine. The most important Maillard reaction in food proteins occurs with the c-amino group of lysine. Since lysine is an essential amino acid, nutritional consequences can be expected. These depend on the chemical structure of the lysine derivatives formed. 

This leads to a decrease in the biological value of the protein. Milk is a good model to study the nutritional effects of the Maillard reaction because of its high levels of lysine and lactose. In processed milks, unavailable lysine is present only as e-deoxylactulosyllysine (9,24) its level which depends on the type of treatment can be measured by the furosine method (24,31). 

Nutritional Effects Due to the Presence of the Maillard Products. Many physiological or antinutritional effects have been attributed to the Maillard products. Specific effects have been attributed to the Amadori products deoxyfructosylphenylalanine (a model substance not likely to be present in large quantities in foods) appears to depress the rate of protein synthesis in chicks (32) and to partially inhibit in vitro and in vivo the absorption of tryptophan in rats (33). The compound e-deoxyfructosyllysine inhibits the intestinal absorption of threonine, proline, and glycine and induces cytomegaly of the tubular cells of the rat kidneys (34) as does lysinoalanine. In parenteral nutrition the infusion of the various Amadori compounds formed during sterilization of the amino acid mixture with glucose is associated with milk dehydration in infants and excessive excretion of zinc and other trace metals in both infants and adults (35,36,37). 

Nutrition Effect of Protein-Bound Methionine Sulfoxide. There is some discrepancy in the results concerning the biological availability of protein-bound methionine sulfoxide. Ellinger and Palmer (71) found that oxidized casein had a lower NPU (Net Protein Utilization) than normal casein. Slump and Schreuder (72) concluded that there was a positive biological availability of peptide-bound methionine sulfoxide. 

The chemical modifications of the tryptophan residues lead to a decrease in the nutritive value of proteins as observed in autoclaved soja meals (124), heated meats (125), heated casein (126), and heated skim milk (122) this last reference is probably the most reliable work published in this field. The nutritional effects and the metabolic transit of heat-treated and oxidized tripeptide (gly-try—gly) have been investigated (123,132,137) recently only the metabolic transit study is related here. 

More details of the chemical modification of casein and other food proteins with carboxyl-amino acid anhydrides will be published elsewhere. Depending on the distribution and length of copolymers of methionine covalently linked to proteins, distinct effects on functional and nutritional properties of the modified proteins are expected. 

Table V. Comparison of the Effects of Heating Methods on Protein Nutritive Value of Soy Meal (20) ...

Woodard, C.J., Short, D.D., Alvarez, M.R. and Reyniers, J. (1975). Biological effects of N-e-(DL-2-amino-2-carboxyethyl)-L-lysine, lysinoalanine. In "Protein Nutritional Quality of Foods and Feeds", M.Friedman, Ed., Marcel Dekker, New York,... 

Interactions between tannins and proteins have been extensively studied (Hager-man 1989 Haslam and Lilley 1988 Haslam et al. 1992), owing to their role in haze formation, astringency perception, and nutritional and anti-nutritional effects resulting from inhibition of various enzymes and reduction of dietary protein digestion. Other effects include reduced adsorption of /3-casein at the air-liquid interface in the presence of epigallocatechin gallate with potential consequences on foam properties (Sausse et al. 2003). 

Effect on Nutritional Value The beneficial nutritional effects of extrusion vary with species, age, and type of ration being fed, but, in general, these benefits can be expected of the protein, energy, and fiber content of the ration by the following factors. 

DWORSCHAK J D (1980) Nonenzyme browning and its effect on protein nutrition. 

Szulc et al. (2005) reported that skeletal muscle mass was correlated positively with bone mineral content and bone mineral density in the Mediterranean Intensive Oxidant Study (MINOS). MINOS was a prospective study of osteoporosis and its determinants that showed that men with the least skeletal mass also had increased risks of falls due to impaired static and dynamic balance. The relative importance of muscle compared with hormonal and other nutritional effects on bone health may be argued in the MINOS study because factors such as dietary protein, insulin growth factor, and testosterone also affect bone directly, but chronically low muscle mass may provide a visible indicator of bone mass and bone density risk. Osteopenia and osteoporosis are seen as problems in elderly people. In countries with shortened life spans, bone health issues may go unnoticed. 

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