Phytin® (Phytic acid) Isolation and Identification

Phytin is a white amorphous powder, odorless and tasteless, almost insoluble in water, soluble in dilute mineral acids and in some organic acids. One part Phytin dissolves in 10 parts of 1 n hydrochloric acid and forms a clear solution. According to some authors, Phytin contains 36% organically bound phosphoric acid. Upon heating with dilute acids, alkali and water, Phytin hydrolyzes to give ortho-phosphoric acid and the cyclitol myo-inositol as end products. These are obtained together with some other products of semi-degradation.

The first patents for Phytin isolation were filed by S. Posternak and date back to 1902 and 1903 (DRP 147968, 147969, 159749, 160470). In his extensive studies S. Posternak (1921) established that the salts (magnesium, calcium, manganese, etc.) of phytic acid he obtained were likely to lose 3 molecules of water upon vacuum drying and suggested the following gross formula for phytic acid.

C16H18O24P.3H20

The structural identification of phytic acid and, consequently, Phytin structure remained questionable for long time. The following two tentative structures were commented: Neuberg's (1908) asymmetric tri-pyrophosphate structure and Anderson's (1914) symmetric hexa-orthophosphate structure.

Structural identification of phytic acid

Different arguments have been proposed for each structure.Smith and Clark (1951) confirmed the heterogeneity of phytic acid by ion-exchange methods. Cosgrove (1966) identified it as a complex mixture of polyphosphates, including esters of inositol and myo-inositol. Tate (1968) studied phytic acid by electrophoresis and nuclear magnetic resonance and verified its structure as myo-inositol-hexa-phosphoric acid.

Synthesis (Courtois, J. et al. 1951); Diemair and Becker, 1955) and modern chromatographic and spectrographic techniques (Johnson, L.F. et al. 1969) have ascertained that the gross formula of phytic acid is C6H6[OPO(OH)2]6, whereas its structural formula is recognized as:

Structural identification of phytic acid

The raw material for Phytin production is rice bran and cereal grains bran, as well as oil plant cakes obtained as by-products of the food processing and oil-producing industries.

When processing the raw plant material, it should be known that many plant seeds (especially of the bean species) contain the enzyme phytase together with Phytin. In aqueous solutions phytase causes partial or complete hydrolysis of Phytin to intermediary products, such as inositol-mono-, inositol-di-, and inositol-tri-ortho-phosphates.

Different technological processes are available for industrial Phytin isolation. They can be classified in two groups, according to the extracting medium used. Most methods include extraction of the plant material with acidulated water, using some organic acids (formic, trichloroacetic, lactic, oxalic, citric, etc.) (Sarma, 1942) or dilute mineral acids (hydrochloric, nitric) (Schormoeller, J. et al., 1956); Pavlov L., S. Stanev, V. Kamedulski, 1969; Zakharov V. P. 1993).

The aqueous -acid extracts, in addition to the main product, yield also protein substances, inorganic salts, sugars, etc. some of the proteins precipitate with time and can be further separated by filtration. Phytin itself falls as a white amorphous precipitate after neutralization and mild alkalization with alkaline base, lime water, ammonia, basic carbonate or acetate, etc. The precipitated crude product is filtered, washed, and purified by subsequent dissolution and precipitation, boiling with activated charcoal and intermediary treatments to remove specific admixtures (Posternak, 1903, Pavlov et al., 1969).

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