Jamel S. Hamada

Preparative separation of value-added peptides from rice bran proteins by high-performance liquid chromatography

Abstract Peptides from rice bran protein were investigated because of their potential usefulness in industrial food uses. Peptides were generated from defatted rice bran by treatment with a commercial protease to 7.6% peptide bond hydrolysis. Protein hydrolysates were separated into 20 peaks by quaternary methylamine anion-exchange HPLC on a 25 mm×30 cm column with 96% recovery. Out of 12 peptide fractions, the first four contained 37 and 57% of the total protein and amide in the hydrolysate, respectively. Since glutamic acid in peptides is a potent flavor enhancer, these peptides can serve as an excellent source of flavor enhancing ingredients after further deamidation. An HPLC method was developed for the potential commercial scale-up preparation of these functional peptides for food use leading to new value-added products from the under-utilized rice bran.

Isolation and identification of the multiple forms of soybean phytases

Sequential precipitation with polyethylene glycol (PEG) and KCl followed by preparative anion exchange high-performance liquid chromatography was used to isolated acid phosphatases (APases) from germinating soybean seeds. KCl inhibited the PEG precipitation of APases. Thus individual APases can be isolated directly from crude extracts by controlling PEG and KCl concentrations. Four of the isolated APases were phytases. APases 3 and 5 exhibited optimal activity at pH 4.5 and and 5.8. Phytase activity was at its peak at 40°C for APase 4 and at 60°C for APases 3, 5, and 6. This isolation method can be used to identify endogenous and/or exogenous phytases that are suitable for phytic acid hydrolysis in many food and feed systems, especially during the processing. of oilseeds and cereal-based ingredients.

Peptidoglutaminase deamidation of proteins and protein hydrolysates for improved food use.

The limited deamidating ability of peptidoglutaminase (PGase) toward intact food proteins (0- 6% deamidation) can be significantly enhanced by prior protein hydrolysis and altering protein conformation by such means as moist heat. PGase deamidation increases protein solubility and improves emulsifying and other physical properties under mildly acidic conditions. A batch reactor method was developed for the large- scale PGase deamidation of food proteins. Michaelis- Menten kinetics for industrial reactions (mixed zero- and first- order) were used for predicting the behavior of the reactor and for calculating enzyme dosage required to completely deamidate a given quantity of protein. Using such a reactor in the deamidation of food proteins or protein hydrolysates can lead to new food proteins with superior functional properties from less functional starting materials.

Deamidation and Phosphorylation to Improve Protein Functionality in Foods

Many proteins utilized for human consumption require structural modification to achieve the proper functional properties for use as food ingredients. Food protein modification is normally accomplished by either chemical or enzymatic methods. Chemical hydrolysis with acid or base and enzymatic proteolysis have been popular and useful modification techniques used by the food processing industry. However, existing commercial modification procedures are limited in number and usefulness. Other chemical and enzymatic modification methods must be developed and made available to the food processor, particularly methods that do not significantly decrease the nutritional value of the protein.