Fate of Phytic Acid in Producing Soy Protein Ingredients

Abstract

Phytic acid (myo-inositol hexaphosphate) is present in soybeans and soy protein products at 1-2% dry matter. Phytate causes poor absorption of essential electrolytes and minerals, and binds to proteins and co-precipitates with isoelectric soy protein isolates. We determined how phytic acid partitioned during different procedures to prepare soy protein ingredients. Procedure and soybean variety significantly affected phytic acid content and recovery. High-sucrose/low-stachyose (HS/LS) soybeans contained significantly (P < 0.05) less phytate than did a typical variety of commodity soybeans (IA2020). In addition, phytate was more readily extracted from the commodity soybeans than from HS/LS soybeans. Among all procedures studied, ethanol-washed soy protein concentrate had the highest phytate contents and yields in the protein products for both soybean varieties (~80 mg/g and 99%, respectively). When protein extraction was carried out at room temperature the protein products had significantly lower phytate yields (60-78%) than when extraction was at 60°C (80-99%). The protein products obtained from normal soybeans had significantly higher phytate contents than the same products made from HS/LS soybeans. When fractionating soy proteins, the glycininrich fraction contained significantly less phytate than the b-conglycinin fraction except for the fractionation procedure performed at room temperature instead of 4°C.

Protein–phytate interactions in pig and poultry nutrition: a reappraisal

“…For this reason, the preparation of soya protein isolates and concentrates with reduced phytate contents to avoid Zn deficiencies in human infants has been a goal for decades (53) . As discussed by Erdman (54) , protein concentrates with reduced phytate contents can be prepared by exploiting the capacity of phytate to bind protein, which has been demonstrated in soya (55) and rapeseed (56) , and the fate of phytate following the preparation of soya protein concentrates/isolates has been reviewed (57) . In relation to ternary complexes and protein availability, Champagne et al (58) suggested that the protein moiety of ternary complexes is comprised of either amino acids or small peptides and it then follows that the amount of protein bound in ternary complexes in the small intestine may not be sufficient to compromise amino acid digestibility (9) .…”

Alterações químicas em grãos de soja com a germinação

“…de cálcio, de ferro e de zinco, os quais não são prontamente absorvidos. Devido a sua ação quelante, o ácido fítico é considerado fator antinutricional, afetando a biodisponibilidade dos minerais e contribuindo para sua deficiência (DEAK; JOHNSON, 2007;LAZZARI, 2006;AL-WAHSH et al, 2005;SANDBERG, 2002). Estudos sugerem que o fitato tem ação anticarcinogênica em vários tipos de câncer.…”

“…O ácido fítico é encontrado em alimentos altamente carregados negativamente e formam complexos ou ligações com moléculas de cargas positivas, tais como cátions metálicos e proteínas (DEAK; JOHNSON, 2007). Ocorrem diferentes mecanismos para a interação do fitato com a proteína, que depende dos diversos pHs (pH < 5, pH 5 -7 e pH > 7).…”

“…Em pH intermediário, ambos possuem cargas negativas, e o complexo proteína-fitato permanece estável. Em pH elevado, cátions multivalentes, como o cálcio, são essenciais para a formação do complexo proteína-fitato (DEAK; JOHNSON, 2007).…”

“…Alguns compostos fenólicos podem reduzir a digestibilidade da proteína e a biodisponibilidade de minerais (DÍAZ-BATALLA et al, 2006). O fitato, fator antinutricional presente nos grãos de soja, é também denominado mioinositol -1, 2, 3, 4, 5, 6 hexa-dihidrogênio fosfato, componente abundante, com teor variando entre 1% e 1,5% da composição do grão (DEAK; JOHNSON, 2007;KUMAR et al, 2005). Representa a principal forma de armazenamento de fósforo (P) (de 50 a 70% do P total) e é acumulado durante a maturação e mobilizado para a germinação e crescimento da planta (LAZZARI, 2006).…”