EFFECT OF FERTILIZERS ON THE YIELD, PROTEIN CONTENT AND AMINO ACID COMPOSITION OF WINTER CEREALS

The effect of different fertilizers (nitrogen, phosphorus, potassium) and their combinations on the yield, raw protein content and amino acid composition were studied in field experiments. The levels of treatment were 200 kg/ha for nitrogen, 500-1000 kg/ha for phosphorus and potassium. Winter rye, triticale and wheat cultivar were grown in two subsequent years. Nitrogen fertilization in all cases increased the yield of grains and the raw protein content. The increase reached about 50% in average comparing with control samples grown without adding nitrogen fertilizers. Although there are significant differences between the different cereals studied, it can be generally stated that the increase in protein content is connected with a decrease in the essential to non-essential amino acid ratio. The decrease is higher if only nitrogen fertilizer is used and moderate if a combined treatment with nitrogen, phosphorus and potassium fertilizer is applied

INVESTIGATION OF SOME FUNCTIONAL AND NUTRITIVE PROPERTIES OF CEREAL GERM PROTEINS

Proteins, protein concentrates and isolates were prepared frolll wheat, rye, barley, rice and maize germs. after defatting with hexane or supercritical carbon dioxide, by alkaline extraction (NaOH, pH=10) and acid precipitation (0.1 mol/l HCI). The chemical composition, amino acid composition and functional properties (emulsifying properties, foam activity and stability, water , and oil absorption, solubility) were determined. The digestibility and biological value of protein preparations were also calculated. Protein isolates had a high protein content (75.8 - 94.3%). The oil content was low, except in maize germ protein isolates, obtained after defatting with supercritical carbon dioxide. High digestibility (83 - 90%) and moderate biological value (63 - 7,5 FAO/WHO index) was characteristic of all isolates. Methionine and cysteine were the limiting amino acids. Ivlaize germ protein isolates showed the best functional properties, being comparable with those of soy protein isolates. Other germ protein isolates also had acceptable properties. No significant. differences were observed bet ween the functional properties of isolates prepared after defatting with hexane or supercritical carbon dioxide, except the foaming properties. The latter were adversely affected by supercritical fluid extraction

Dietary Proteins as Determinants of Metabolic and Physiologic Functions of the Gastrointestinal Tract

Dietary proteins elicit a wide range of nutritional and biological functions. Beyond their nutritional role as the source of amino acids for protein synthesis, they are instrumental in the regulation of food intake, glucose and lipid metabolism, blood pressure, bone metabolism and immune function. The interaction of dietary proteins and their products of digestion with the regulatory functions of the gastrointestinal (GI) tract plays a dominant role in determining the physiological properties of proteins. The site of interaction is widespread, from the oral cavity to the colon. The characteristics of proteins that influence their interaction with the GI tract in a source-dependent manner include their physico-chemical properties, their amino acid composition and sequence, their bioactive peptides, their digestion kinetics and also the non-protein bioactive components conjugated with them. Within the GI tract, these products affect several regulatory functions by interacting with receptors releasing hormones, affecting stomach emptying and GI transport and absorption, transmitting neural signals to the brain, and modifying the microflora. This review discusses the interaction of dietary proteins during digestion and absorption with the physiological and metabolic functions of the GI tract, and illustrates the importance of this interaction in the regulation of amino acid, glucose, lipid metabolism, and food intake