Corn and barley protein concentrates: effects of fractionation and micronization on the chemical, functional, and thermal properties

The present study intends to investigate the impact of fractionation and micronization on the compositional, functional, and thermal characteristics of two protein concentrates derived from corn and barley. Fractionation of protein concentrates (by sieving) resulted in three fractions, i.e., fine (< 100 mu m), medium (100-300 mu m), and coarse (> 300 mu m), while micronization resulted in an average particle size of 30 mu m. No specific pattern was observed between particle size and chemical composition of corn and barley protein concentrates due to the complex interplay between particle size, surface area, structural changes, and botanical origin. Protein solubility varied depending on the pH and particle size, showing that the coarse fraction exhibited higher solubility than the fine fraction. For both corn/barley protein concentrates, coarse fraction had higher water-/oil-holding capacity. The barley fine fraction showed high foaming capacity, while all proteins lacked emulsification ability. Across all samples, a trend of increasing enthalpy with decreased particle size was observed, except for micronized barley, where enthalpy decreased, indicating possible protein structural changes. Thus, variations in properties among fractions highlight the importance of particle size in determining the proteins' functionality for potential applications in food systems.