Combined Effect of Protease and Phytase on the Solubility of Modified Soy Protein

Abstract

Soy protein isolate (SPI) was subjected to enzymatic hydrolysis with protease and phytase, and the solubilities of the modified SPIs (MSPIs) were characterized and compared with those of a commercial modified protein (SUPRO 670 IP from the Solae Company, St. Louis, MO). The solubilities of MSPIs showed a typical pH‐dependent curve, shifting upward with an increase of hydrolysis time and enzyme dose. In particular, the solubility at pH 4.5 of the MSPI with degree of hydrolysis of 9.8% increased 9.7‐fold more than SPI. Furthermore, the combined enzymatic treatment (protease and phytase) led to a significantly increased solubility of SPI at pH 4.5, which improved by 11.5‐fold and 1.8‐fold more than SPI and SUPRO 670 IP, respectively. In conclusion, the use of hydrolytic enzymes to synergistically improve solubility in the acidic range of pH may provide a positive impact on the MSPIs as a multifunctional food ingredient. Practical Applications Even though soy protein isolates (SPIs) are used in food industry because of their beneficial health effects as well as specific functional properties, the applications of SPIs to processed foods under acidic conditions are very limited. In this study, SPIs were modified by each or combined enzymatic treatments and their solubilities were compared in a wide range of pH. The solubility of the modified SPI (MSPI) was significantly improved compared with the commercial product. Therefore, the MSPI with enhanced solubility at acidic pH could be used in an extended range of processed foods.

Protein-rich beverage developed using non-GM soybean (R08-4004) and evaluated for sensory acceptance and shelf-life

“…The differences in solubility between SPI and SPH can be explained by the hydrolysis process which exposed SPH hydrophobic portions of the protein structure to a larger extent. The solubility profiles of soy protein has been reported in several studies (Ruíz-Henestrosa et al 2008;Bae et al 2012). As the pH changed, the hydrophobic amino acids were exposed at the isoelectric point which allowed the protein particles to dissociate from water (Boye et al 2010).…”

The effect of feed enzymes phytase, protease and xylanase on pelleting of microalgal biomass

“…Mixing phytase and protease did not significantly decrease p max . This contrasts with Bae et al. (2013) .…”

“…This was evident as during compaction lowered p max values. Such changes are directly influenced by catalysing the hydrolysis of the bonds between fibre and peptidoglycans from the cell walls ( Bae et al., 2013 ). However, there was no indication that mixtures of xylanase, protease and phytase, in different dosages, influenced p max when compared to control.…”

“…When all three enzymes were added together as the double dosage, most likely, xylanase helped hydrolysing the complex chain of polysaccharides and thus, increased hydrogen bonding between the molecules. When such a structure was formed, the double dosage of protease and phytase may have improved protein solubility, as explained by Bae et al. (2013) .…”

“…Reducing use of inorganic phosphorous in feeds, achieved by treating the feed ingredients with phytase ( Robinson et al., 2002 ), can reduce the feed cost. Adding of phytase, combined with protease, has shown to cause improved protein solubility ( Bae et al., 2013 ). Enzymes are used to reduce the energy dilution of the feed by carbohydrates or fibres, derived from vegetable protein concentrates ( Hardy, 2000 ).…”