Solid-state characteristics and redispersible properties of powders formed by spray-drying and freeze-drying cereal dispersions of varying (1→3,1→4)-β-glucan content

• Published in: Journal of cereal science 2004-09, Vol.40 (2), p.183-193
• Main Authors: Chronakis, Ioannis S., Öste Triantafyllou, Angeliki, Öste, Rickard
• Format: Article
• Language: English
• Subjects: (1→3,1→4)-β-glucan; beta-glucans; Biological and medical sciences; Cereal and baking product industries; electrostatic interactions; Food engineering; Food industries; Freeze-drying; Fundamental and applied biological sciences. Psychology; General aspects; isoelectric point; Morphology; oats; particle size; particle size distribution; Particles; powders; Spray-drying; Surface activity; suspensions; Zeta potential
• ISSN: 0733-5210; 1095-9963
• DOI: 10.1016/j.jcs.2004.03.004

Cereal powders containing 33, 18 and 4% (w/w) (1→3,1→4)-β-glucan, prepared from cereal suspensions, had distinct differences in surface morphology as observed by scanning electron microscopy, depending both on the drying process (spray- or freeze-drying) and the dietary fibre level. Freeze-drying produced powders with a ‘flake-like’ matrix, without particle formation and similar matrix morphology independent of the (1→3,1→4)-β-glucan content, in contrast to spray-drying, which gave powders with morphologies that were (1→3,1→4)-β-glucan-dependent and consisted of aggregated particles and microspheres. Choosing the concentration of (1→3,1→4)-β-glucans permits control of the particle size and particle size distribution of the spray-dried cereal powders. pH-dependent zeta ( ζ) potential measurements of re-dissolved powders indicated that the isoelectric point was in the pH range of 3.8–4.8 and that it increased at higher pH as the (1→3,1→4)-β-glucan content of the powders was decreased from 33 to 4% (w/w). The absolute value of the zeta ( ζ) potential fell with increasing pH and was largest for the powder dispersion with the lower (1→3,1→4)-β-glucan content, leading to the greatest dispersion stability. The importance of particle size, net surface charge and (1→3,1→4)-β-glucan and protein content in controlling the surface activity at the air–water interface of cereal powder dispersions is also discussed.