VTT's scientists have developed new technologies to enhance the dispersion stability of water-soluble oat β-glucan. It is difficult to make beverages which contain over 0.5 % concentrations of untreated β-glucan, because it has a high water-binding and viscosity thickening capacity. Juhani Sibakov and his co-workers showed that extrusion-based acid or enzymatic hydrolysis resulted in a controlled depolymerisation of oat bran β-glucan. The depolymerisation allowed adding β-glucan at up to 1.6 % (w/v) concentration into liquid-solutions without gelling-problems when stored for 12 weeks.
Sibakov et al. performed the acid or enzyme catalysed hydrolysis at low water content. The low water content was chosen to avoid the cleavage of β-glucan into short oligosaccharides, i.e. to preserve β-glucan's characteristics as a dietary fibre.
The hydrolysis was based on a thermo-mechanical treatment in a twin-screw extruder. The acid catalysed reaction was controlled by regulating the temperature (from 100 to 130 °C) during a fast extrusion treatment. The enzyme hydrolysis needed an "out-of-extruder incubation" at 50 °C and the reaction time was much longer (up to 4 hours).
The acid hydrolysed oat bran β-glucan had an average molecular weight (Mw) between 110,000 and 34,000 g/mol and the enzyme hydrolysed β-glucan between 93,000 and 49,000 g/mol. At 1.4–1.6 % β-glucan concentrations in a water solution, the acid hydrolysed molecules started to form gel-like structures after 5–7 weeks of storage. On the contrary, the enzyme hydrolysed molecules stayed longer in the solution without an increase in the viscosity. For example, a 1.6 % water-dispersion of enzyme hydrolysed β-glucan was stable for 12 weeks.
The enhanced dispersion stability enables the utilisation of higher β-glucan concentrations in food products with high moisture, such as fruit juices, soft drinks, smoothies, jellies and puddings. VTT has two patent applications related to the developed process, and we are looking for partners to utilise them commercially. If you are interested in this technology, please contact: Juhani.Sibakov@vtt.fi.
J. Sibakov, O. Myllymäki, T. Suortti, A. Kaukovirta-Norja, P. Lehtinen, K. Poutanen, Comparison of acid and enzymatic hydrolyses of oat bran β-glucan at low water content. Food Research International 52 (2013) 99–108. DOI 10.1016/j.foodres.2013.02.037.