Extractable oat β-D-glucans (βG) provide functional and nutritional benefits in (semi-)liquid foods, like oat-based dairy alternatives. However, oat βG extract characteristics are likely influenced by both extraction conditions and the industrial heat treatment typically applied to oat groats. This study systematically investigated the impact of industrial heat treatment, extraction pH (3.0–9.0) and calcium ions (Ca2+) in the extraction medium (0.01–2.00 mM CaCl2) on oat βG recovery, weight average molecular weight (Mw) and extract viscosity. Independent of the extraction medium, extracts from industrially heat-treated oat groats contained lower amounts of βG (21–25% recovery) with higher Mw (1,065–1,788 kDa), and were more viscous (3.1–4.1 mPa.s) than extracts from non-heat-treated oat groats (44–62% recovery, 42–100 kDa, 1.2–1.3 mPa.s viscosity). This was partially ascribed to low β-glucanase activity during extraction in heat-treated oat groats. For non-heat-treated oat groats, β-glucanase activity was lowest at pH 3.0 (0.3 U/g dm) and highest at pH 6.5 (2.7–2.8 U/g dm) and pH 9.0 (2.4 U/g dm). Notably, Ca2+ could cross-link low molecular weight βG extracted from non-heat-treated oat groats, likely by interacting with negatively charged phosphate groups. To conclude, the industrial heat treatment significantly alters oat βG recovery, Mw and extract viscosity. This very likely will influence functional and nutritional contributions of oat βG in foods. This, however, requires further study, as do the mechanisms behind the here observed effects.
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