Study of emulsifying properties of soluble proteins obtained from
defatted rice bran concentrate
Abstract
Rice (Oryza sativa) is one of the most frequently produced cereals in
the world. Rice bran (RB) is obtained as a by-product in the rice
milling process. A part of the RB is used for oil extraction, obtaining
defatted rice bran (DRB) as a second by-product. The aim of this work
was to analyze the emulsifying properties of soluble proteins fraction
present in defatted rice bran concentrate (DRBC) in acidic and neutral
conditions. Fine emulsions (prepared by high-speed and ultrasound
homogenization) stabilized with soluble proteins obtained from DRBC
showed a mean particle size lower than coarse emulsions (prepared by
only high-speed homogenization) and a significantly lower degree of
overall destabilization. Coarse emulsions showed sigmoidal
destabilization profiles at pH 4.5 and 7.0, related to the existence of
two populations with different particle sizes. In fine emulsions, both
pH provided lower particle sizes and greater stability. After 24 h of
quiescent storage, the coarse emulsions showed an increase of particle
size that was not observed in fine emulsions. Both types of emulsions
showed a Newtonian-type behavior. Fine emulsions showed higher viscosity
values and higher lightness than coarse emulsions, consistent with the
reduction of particle size and increase in the number of particles. The
soluble proteins obtained from a waste of the rice industry can be used
to obtain stable fine oil-in-water emulsions in acidic and neutral
conditions. This result is of interest since it could be used as a food
ingredient, increasing the added value of this important by-product.