Functional Properties of Rice Bran Protein Isolate at Different pH Levels

Abstract

Cereal Chem. 93(1):58-63The functional properties of proteins from Tarom and Shiroodi cultivars were determined and compared with technological aspects of food and nutraceutical applications. Shiroodi has higher protein content than Tarom, and the yields of protein obtained were 72.88 and 66.36%, respectively. Nitrogen solubilities of rice bran protein of Tarom were more than Shiroodi at all pH levels. In addition, higher solubility was found in acidic or alkaline conditions. Although the rice bran proteins had lower emulsifying properties than bovine serum albumin, they had similar foaming properties in comparison with egg white. Tarom isolates had a significantly higher solubility, emulsifying property, and foaming stability and greater surface properties than Shiroodi isolates. The results showed the surface hydrophobicities of rice bran protein were greater than casein and ovalbumin and lower than other proteins such as bovine serum albumin. Water and oil absorption capacities were 1.03 and 1.66 for Tarom and 87.3 and 75.3 for Shiroodi, respectively. The bulk densities of Tarom and Shiroodi were also 0.55 and 0.53 g/mL, which make them suitable for weaning food and other industrial applications. As a result, these rice bran proteins showed higher hydrophobicity than that of other rice bran protein varieties as well as more functionality. Thus, they have good potential in the food and pharmaceutical industries. † Corresponding

Rice‐Endosperm and Rice‐Bran Proteins: A Review

“…All solubilities of brown rice, white rice, and RBP increased with alkalinity or acidity, around 80% and 20% for all proteins at pH 10 and pH 3, respectively. This was attributed to the hastened denaturation and hydrolysis of the proteins under such conditions and corresponded with the findings of both Esmaeili et al () and Wang et al () (Fig. ).…”

“…The effect of pH on the solubility of rice proteins, approximated based on the data from Cao et al () and Esmaeili et al ()…”

“…Rice proteins and RBP have been investigated for their water‐ and oil‐absorption capacities as they are being used as ingredients in such food products. Proteins’ water‐absorption capacities in the range of 1.49–4.72 g/g are crucial in viscous foods, such as soups and gravies, and they are positively correlated with their nitrogen‐solubility index (Esmaeili et al, ). Also, proteins with high water‐absorption capacity aid in decreasing moisture loss and keeping the freshness and moist mouth feel of baked goods (Chandi and Sogi, ; Esmaeili et al, ).…”

“…Proteins’ water‐absorption capacities in the range of 1.49–4.72 g/g are crucial in viscous foods, such as soups and gravies, and they are positively correlated with their nitrogen‐solubility index (Esmaeili et al, ). Also, proteins with high water‐absorption capacity aid in decreasing moisture loss and keeping the freshness and moist mouth feel of baked goods (Chandi and Sogi, ; Esmaeili et al, ). Water‐absorption capacity of proteins is affected by numerous factors, such as their molecular size, form, steric factors, conformational features, hydrophilic‐hydrophobic balance of their amino acids and their lipid, carbohydrate, and tannin contents, and interactions (Mao and Hua, ).…”

“…Also, proteins’ high oil‐absorption capacity is a very important characteristic when proteins, especially from plant sources, are utilized as meat replacements or extenders as they increase flavor retention, and allegedly enhance mouth feel. Oil‐absorption capacity of a protein is positively correlated with its surface hydrophobicity (Esmaeili et al, ; Mao and Hua, ).…”