Influence of heat pretreatments of oat grain on the viscosity of flour slurries

• Published in: Journal of the science of food and agriculture 1997-05, Vol.74 (1), p.125-131
• Main Authors: Doehlert, D.C, Zhang, D, Moore, W.R
• Format: Article
• Language: English
• Subjects: (1→3), (1→4)‐β‐D‐glucan; (1→4)-β-D-glucan; 1→3; beta-glucanase; beta-glucans; Biological and medical sciences; carbohydrates; Cereal and baking product industries; chemical composition; extracts; flour; Food industries; Fundamental and applied biological sciences. Psychology; heat treatment; hydrolysis; molecular weight; oat; oats; pretreatment; roasting; slurries; steaming; viscosity; β-glucanase
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/(SICI)1097-0010(199705)74:1<125::AID-JSFA782>3.0.CO;2-S

Heat treatment of oat grain had significant effects on the viscosity of flour slurries. Steamed oats produced highly viscous flour slurries, whose viscosity increased with time, whereas the viscosity of flour slurries produced from raw or roasted (104 degrees C for 120 min) oats was much lower and degraded rapidly. Slurry viscosity was correlated with (1 leads to 3), (1 leads to 4)-beta-D-glucan concentration in the flours and treatment of slurries with lichinase lowered viscosity significantly. Effects of steaming were partially reversed by roasting treatment and vice versa. Mixtures of equal amounts of raw and steamed flour resulted in slurries more viscous than either flour alone, but that viscosity degraded after 3 h to less than the mean viscosity of the steamed and raw controls. Water-soluble extracts from steamed flour had about twice the viscosity of raw or roasted flour extracts, but contained only 80% of the (1 leads to 3), (1 leads to 4)-beta-D-glucan present in those extracts. Molecular weight analysis of soluble carbohydrates from raw, roasted and steamed soluble extracts indicated the molecular weight of beta-glucans in these extracts was similar. However, if extracts were made from slurries that had incubated for 3 h, extensive degradation of beta-glucans was evident in raw and roasted samples. It is likely that enzymic degradation of (1 leads to 3),(1 leads to 4)-beta-D-glucans is responsible for much of the decreased raw and roasted flour slurry viscosity over extended time periods, but different heat treatments appear to also affect (1 leads to 3), (1 leads to 4)-beta-D-glucan polymer interaction.