Protein nutritional availability

Many pharmaceutical compounds are weak acids or bases that can be analyzed by an aqueous or nonaqueous acid-base titration examples include salicylic acid, phenobarbital, caffeine, and sulfanilamide. Amino acids and proteins can be analyzed in glacial acetic acid, using HCIO4 as the titrant. For example, a procedure for determining the amount of nutritionally available protein has been developed that is based on an acid-base titration of lysine residues. ... 

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. 

Prolonged heating of protein-rich foods in alkaline conditions may decrease the nutritional availability of proteins by loss of essential amino... 

While the determination of total lysine is rather straightforward, the determination of free or available lysine is more problematic. In this situation, the term free is meant to imply that the e-amine of the lysine side chain has not reacted with various components of the sample matrix (most commonly carbohydrates via Maillard browning). This is important because reaction of the e-amine can render lysine nutritionally unavailable and the nutritive value for that protein is then diminished if lysine is the limiting amino acid (which is often the situation with soy proteins). While enzymatic digestion in the human gut may not release the modified lysine in a nutritionally available state, often these lysine adducts are labile to the standard acid hydrolysis in 6N HC1 at 110°C. This results in total lysine values that overestimate the amount of nutritionally available lysine. 

Nutritional Availability of Acylated Lysine and Proteins. The successful use of chemically derivatized proteins as food ingredients requires that they be digestible and nontoxic, and that the modified amino acid residues should be available nutritionally. Nutritional studies using modified food proteins are limited. The nutritional availability of several acylated lysines were studied by Bjarnason and Carpenter (105) and Mauron (106) and the results are summarized in Table III. The bioavailability of the acylated lysine varied significantly with the type of the acyl groups (see Table III). In addition acylated proteins (acetylated and succinylated) gave lower responses to the growth activity for the rats than equivalent supplements of unmodified proteins... 

Acidic pH conditions caused the removal of dtraconyl groups from the citraconylated yeast proteins, so the environmental conditions of the stomach, i.e., pH and temperature, may cause the deacylation to occur following consumption of citraconylated proteins. This then would make lysine nutritionally available. The peptic digestibility of the citraconylated and decitraconylated yeast proteins was determined soy proteins and egg albumin were studied also for comparison. In a typical experi-... 

Furosine, a marker of the Maillard reaction product, is a valuable indicator of food protein quality. It is a marker for thermal treatment in foodstuffs and is directly related to the loss of lysine availability. IPC was employed to determine furosine content in beverages based on soy milk and cow milk supplemented with soy isoflavones [39]. Furosine was also analyzed in 60 commercial breakfast cereals to assess their protein nutritional values. The higher the protein content in the formulation, the higher the furosine levels [40]. A simple IPC technique that uses 1-octanesulfonic acid as the IPR allowed the selective determination of histamine levels in fermented food [41]. 

Sources. Niacin and substances that are convertible to niacin are found naturally in meat (especially red meat), poultry, fish, legumes, and yeast. In addition to preformed niacin, some L-tryptophan found in the proteins of these foods is metabolized to niacin. Niacin is also present in cereal grains, such as corn and wheat. However, consumption of corn-rich diets has resulted in niacin deficiency in certain populations. The reason for this is that niacin exists in cereal grains in bound forms, such as the glycoside niacytin, which exhibit little or no nutritional availability. Interestingly, niacin deficiency is not common in Mexico and Central America even though the diets of those in these countries are based on com. Alkaline treatment, such as soaking corn in a lime solution—the process used by the populations of Mexico and Central America in the production of com tortillas—yields release of bound niacin and increased availability of the vitamin. 

The term fat can refer to a wide array of substances—oil, tallow, lard, fatty acids, all the glycerides (tri-, di-, and mono-), etc. All of these are nutritionally available, and all contain the same high level of energy, of about 9cal/g, while carbohydrates and protein only contain 4cal/g. 

Faure, G.C. Dynamics of the main immunologically and nutritionally available proteins of human milk during lacta- 40. 

Oxidation of methionine residues of food proteins and nutritional availability of methionine sulphoxide. Food Chem. 3 85... 

The nutrient sparing effect of antibiotics may result from reduction or elimination of bacteria competing for consumed and available nutrients. It is also recognized that certain bacteria synthesize vitamins (qv), amino acids (qv), or proteins that may be utilized by the host animal. Support of this mode of action is found in the observed nutritional interactions with subtherapeutic use of antibiotics in animal feeds. Protein concentration and digestibiHty, and amino acid composition of consumed proteins may all influence the magnitude of response to feeding antibiotics. Positive effects appear to be largest... 

AH of the protein amino acids are currentiy available commercially and their uses are growing. Amino acids and their analogues have their own characteristic effects in flavoring, nutrition, and pharmacology. 

Nutrition. Zinc is essential to the proper functioning of plants and animals and, as zinc sulfate and oxide, it is used as a feed supplement (49—51) (see Mineral nutrients Feedsand feed additives). Most crops use less than a kilogram of zinc per 1000 m per year, so that zinc salts added at 1.3—4.5 kg/ha gradually build up the zinc reserve (52). Animals, including humans, store relatively Htde available zinc and, thus, require a constant supply in the diet. For instance, beef cattle require 10—30 mg/kg dry feed, dairy cattle 40 mg/kg, and breeding hens 65 mg/kg. Zinc from plants is considered less available to monogastric aminals than zinc from animal protein. 

The aim of this work is the determination of several nutritional parameters, such as Energetic Value, Protein, Fat, and Carbohydrates content, in commercially available yoghurt samples by using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FT-IR) spectrometry and a partial least square approach. 

The use of foods by organisms is termed nutrition. The ability of an organism to use a particular food material depends upon its chemical composition and upon the metabolic pathways available to the organism. In addition to essential fiber, food includes the macronutrients—protein, carbohydrate, and lipid—and the micronutrients—including vitamins and minerals. 

Amino acids promote the production of proteins, enhance tissue repair and wound healing, and reduce the rate of protein breakdown. Amino acids are used in certain disease states, such as severe kidney and liver disease, as well as in TPN solutions. (See the last section of this chapter for a more detailed discussion of TPN.) TPN may be used in patients with conditions such as impairment of gastrointestinal absorption of protein, in patients with an increased requirement for protein, as seen in those with extensive bums or infections, and in patients with no available oral route for nutritional intake ... 

Most sweeteners are forms of sugar, since sugar is very cheap and easily available. But for health reasons, more and more people are getting their sweeteners in non-nutritive form, or in the form of short proteins that are so sweet that the number of calories needed to sweeten the food is negligible. 

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