Comparison of acid and enzymatic hydrolyses of oat bran ¦Â-glucan at low water content

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• 作者：Juhani Sibakov ; ^{Juhani.Sibakov@vtt.fi} ; Olavi Myllymä ; ki ; Tapani Suortti ; Anu Kaukovirta-Norja ; Pekka Lehtinen¹ ; Kaisa Poutanen
• 关键词：DP ; degree of polymerisation ; Mw ; weight average molecular weight ; Mn ; number average molecular weight ; HMw ; high molecular weight ; LMw ; low molecular weight ; SDF ; soluble dietary fibre
• 刊名：Food Research International
• 出版年：2013
• 出版时间：June, 2013
• 年：2013
• 卷：52
• 期：1
• 页码：99-108
• 全文大小：1930 K

文摘

The effect of acid- or enzyme-catalysed hydrolysis on partial depolymerisation of ¦Â-glucan in oat bran was studied. Hydrolyses were performed at relatively low water content (50 % dry matter) using high shear mixing in a twin-screw extruder. The hydrolysed oat brans were extracted with hot water and centrifuged to obtain a water-soluble phase and an insoluble residue. The time-dependent gelling of the water-soluble phase was monitored for 14 weeks at 5 ¡ãC. Acid-hydrolysis required a short reaction time (3 min) to depolymerise the ¦Â-glucan molecules from their original average M_w of 780,000 to 34,000 g/mol. After acid-hydrolysis, ¦Â-glucan had low polydispersity (4.0-6.7). Longer incubation time (3-4 h) was needed for enzymatic depolymerisation of the ¦Â-glucan molecules down to 71,000-49,000 g/mol. Enzymatic hydrolysis resulted in high polydispersity (19.0-24.2). The concentration and M_w of ¦Â-glucan significantly affected the gelling of hot water extracts. At 1.4-2.0 % ¦Â-glucan concentration, solutions of ¦Â-glucan molecules with M_w > 50,000 g/mol agglomerated rapidly, whereas solutions of smaller molecules (34,000-49,000 g/mol) remained as stable dispersions for longer. Gelling was strongly concentration-dependent and at 1.4 to 1.6 % beta-glucan concentration gelling occurred after 7 to 12 weeks of storage, whereas at 1.8 to 1.9 % concentration gelling occurred already after 2 weeks of storage.