Phosphorus in foods

Increasing both dietary Ca and P causes a decrease in PTH-mediated bone resorption polyphosphates and phosphorus in food cause greater reductions than does inorganic orthophosphate, as these sources are slowly released in digestion. 

Technicon Instruments Corp. (1977) Digestion and Sample Preparation for the Analysis of Total Kjeldahl Nitrogen and/or Total Phosphorus in Food and Agricultural Products using the Technicon BD-20/40 Block Digestor, Technicon Industrial Method No.369-75A, Technicon Instruments Corporation, New York, USA. 

About 70 percent of the phosphorus in foods is assimilated into our bodies, unlike calcium, of which only 20 to 30 percent is absorbed from food in the small intestine. Excess phosphorus and magnesium in the blood hinder absorption of calcium from food. (Calcium, in turn, hinders absorption of iron.) If the intake of calcium, phosphorus, or vitamin D is too low, bones don t grow properly. 

C.C. Oliveira, E.A.G. Zagatto, A.N. Araujo, J.L.F.C. Lima, Sample preparation in sequential injection analysis. Spectrophotometric determination of total phosphorus in food samples, Anal. Chim. Acta 371 (1998) 57. 

The distribution of phosphorus in foods is widespread (Tables 11.11 and 11.12) and human dietary needs of about 1.3 g/day are easily met. In western diets about one-third of this is supplied by milk and dairy products and most of the remainder by meat and grain products. 

Whereas the phosphorus in foods may be associated with all the nutrient classes (11.1) through (11.5), in the case of nitrogen, nearly all of it is present as protein. 

Since much of the phosphorus in foods occurs as a phosphate compound, the first step (prior to absorption) is the splitting off of phosphorus for absorption as the free mineral. The phosphorus is then absorbed as inorganic salts. 

Universal and selective detectors, linked to GC or LC systems, have remained the predominant choice of analysts for the past two decades for the determination of pesticide residues in food. Although the introduction of bench-top mass spectrometers has enabled analysts to produce more unequivocal residue data for most pesticides, in many laboratories the use of selective detection methods, such as flame photometric detection (FPD), electron capture detection (BCD) and alkali flame ionization detection (AFID) or nitrogen-phosphorus detection (NPD), continues. Many of the new technologies associated with the on-going development of instrumental methods are discussed. However, the main objective of this section is to describe modern techniques that have been demonstrated to be of use to the pesticide residue analyst. 

The most important acid containing phosphorus is orthophosphoric acid, H3P04. This is the acid usually indicated when the name phosphoric acid is used in most contexts. Approximately 30 billion pounds of this acid are produced annually. The commercial form of the acid is usually a solution containing 85% acid. The process used to produce phosphoric acid is related to the intended use of the acid. If the acid is intended for use in foods, it is prepared by burning phosphorus and dissolving the product in water. 

Meat and such high protein plant foods as soy are excellent sources of phosphorus as well as protein. The phosphorus in meat is readily absorbed from the gastrointestinal tract however, much of the phosphorus in plant products is in a bound form which may inhibit the absorption of calcium as well as phosphorus. This study was designed to determine the effect of different levels of calcium and phosphorus with plant protein or animal protein on bone breaking strength and calcium and phosphorus utilization of weanling mice. 

The manufacture of phosphorus-derived chemicals is almost entirely based on the production of elemental phosphorus from mined phosphate rock. Ferrophosphorus, widely used in the metallurgical industries, is a direct byproduct of the phosphorus production process. In the United States, over 85% of elemental phosphorus production is used to manufacture high-grade phosphoric acid by the furnace or dry process as opposed to the wet process that converts phosphate rock directly into low-grade phosphoric acid. The remainder of the elemental phosphorus is either marketed directly or converted into phosphoms chemicals. The furnace-grade phosphoric acid is marketed directly, mostly to the food and fertilizer industries. Finally, phosphoric acid is employed to manufacture sodium tripolyphosphate, which is used in detergents and for water treatment, and calcium phosphate, which is used in foods and animal feeds. 

Jane, J., Kasemsuwan, E, Chen, J. F., Juliano, B. O. (1996). Phosphorus in rice and other starches. Cereal Foods World, 41, 827-832. 

Cereals and meats are the major sources of phosphorus in human diets. Phosphorus deficiencies in most regions have not been a serious problem in human nutrition. Insofar as food is concerned, the primary value of phosphorus fertilizers is that they generally increase the total food production not die content of phosphorus in the food per se,... 

Pure phosphoric acid is a low-melting, colorless, crystalline solid (mp 42°C), but the commercially available phosphoric acid used in the laboratory is a syrupy, aqueous solution containing about 82% H3P04 by mass. The method used to manufacture phosphoric acid depends on its intended application. For use as a food additive—for example, as the tart ingredient in various soft drinks—pure phosphoric acid is made by burning molten phosphorus in a mixture of air and steam ... 

White phosphorus is used mainly for producing phosphoric acid and other chemicals. These chemicals are used to make fertilizers, additives in foods and drinks, cleaning compounds, and other products. Small amounts of white phosphorus have been used as rat and roach poisons and in fireworks. In the past, white phosphorus was used to make matches, but another chemical with fewer harmful health effects has since replaced it. 

White phosphorus can enter your body when you breathe air containing white phosphorus. We do not know if white phosphorus in your lungs will enter the blood. White phosphorus can also enter your body when you eat food or drink water containing white phosphorus or when you are burned by it. We do not know if white phosphorus can enter your body through skin that has not been cut or burned. If it enters your body when you eat, drink, or are burned, white phosphorus enters the blood rapidly. We do not know if it changes into other compounds in the blood. 

The recommended ratio of phosphorus to calcium is 1 1, except in infants it is 2 1. For older infants, the recommended intake of phosphorus is increased to 80% of the calcium requirement, so that the ratio is similar to cow s milk (Harper 1969). Both phosphorus and calcium are distributed similarly in foods, hence a sufficient intake of calcium ensures a sufficient intake of phosphorus. The exception is cows milk, which contains more phosphorus than calcium (Harper 1969). The adult daily requirement for phosphorus is about 700 mg. A balanced diet provides sufficient amounts of phosphorus because it is commonly found in foods (phosphoproteins and phospholipids, inorganic phosphate), especially milk and milk products, wheat, meats and fish (Latner 1975). In the body, normal serum (inorganic) phosphorus levels are 4-7 mg/100 mL in children and 3-4.5 mg/100 mL in adults and the elderly. In body fluids and tissues, normal serum phosphorus levels found are 40, 170-250, 360, and 22,600 mg/100 mL in blood, muscle, nerve, and both bones and teeth, respectively (Harper 1969 Tietz 1970). 

Bohn HL, Johnson GV, Cliff JH. 1970. Detoxification of white phosphorus in soil. J Agric Food Chem 18 1172-1173. 

Concentrating phosphoric acid leads to polyphosphoric acid, a mixture of several polymeric species, a good catalyst and dehydrating agent. Polyphosphate salts are used as water softeners in detergents or as buffers in food. Small quantities of elemental phosphorus are used to make matches, and phosphorus halides to prepare specialty chemicals for the pharmaceutical and agrochemical industries. 

Monophosphorylation pastes made from starch monophosphates also have greater clarity, viscosity and stability than unmodified starches,64 but are sensitive to salts, especially polyvalent cations.65 Variability in residual ash can lead to variability in the viscosity of monophosphorylated starches. Monophosphate substitution also lowers the gelatinization temperature at 0.07 DS, a value much greater than is found in food starches, the gelatinization temperature is below room temperature. Native potato starch contains 0.07 to 0.09% bound phosphorus and wheat starch contains 0.055% phosphoms, primarily as phosphoglycerides in the latter case. The FDA allows up to 0.4% phosphate as phosphoms.58 Monophosphates were used commercially in the US until about 1970. 

It should be taken into account that the abundance of PolyPs in food may have some unstudied effect on health. For example, if rats were fed with a high-phosphorus diet, they developed nephrocalcinosis. This was more severe in rats fed on PolyP3 than in those fed on pyrophosphate (Matsuzaki et al., 2001). Thus, the influence of PolyPs in food on human health needs further investigations, especially in view of those diseases associated with phosphate metabolism. 

The ash content of soybeans is relatively high, close to 5 percent. The ash and major mineral levels in soybeans are listed in Table 5-7. Potassium and phosphorus are the elements present in greatest abundance. About 70 to 80 percent of the phosphorus in soybeans is present in the form of phytic acid, the phosphoric acid ester of inositol (Figure 5-5). Phytin is the calcium-magnesium-potassium salt of inositol hexaphosphoric acid or phytic acid. The phytates are important because of their effect on protein solubility and because they may interfere with absorption of calcium from the diet. Phytic acid is present in many foods of plant origin. 

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