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Browsing by Subject "Oat β-glucan"

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  • Oat β-glucan emulsion properties 
    Chu, Wai (2021)
    Oat beta-glucan, β-glucan, is a soluble dietary fibre located in the endosperm and aleurone cell walls. It is a polysaccharide that has an ability to form viscous gel in aqueous solutions due to its high water binding capacity. The objective of this study was to determine the physical characteristics of commercial oat β-glucan with different purity in solution. Four commercial oat beta-glucan powders with varying β-glucan content were provided for this study. Solubility, water binding capacity, viscosity, suspension and emulsion stability, droplet particle size, particle distribution and zeta potential were determined from the samples. There were two phases in the experimentation part in which the first phase focused on suspensions and the second phase focused on emulsions. There were four different homogenising treatments used to solubilize the samples into water during the first phase of the experiment, which were stirring in room temperature, 80 ˚C, Ultra-Turrax and microfluidization. Megazyme exhibited highest solubility in water with a solubility rate of 100 % regardless of the treatment used. OatWell had the highest water binding capacity (11.7 g/g) after heat treatment. Heat treated OatWell had the highest viscosity (590 mPas). Megazyme emulsions had the highest emulsion stability (TSI ranging from 0.6 to 3.6) as it did not experience phase separation until fifth day of measurement. Megazyme emulsions also had the lowest particle sizes ranging from 0.4 μm to 1.5 μm. The results of this study highlight that the content of β-glucan has notable effect on its solubility and the homogenisation treatment used has an increasing effect on solubility and decreasing effect on water binding capacity and viscosity. Purity of the oat β-glucan also has an effect on emulsion stability as high purity oat β-glucan are able to stabilise emulsion system after homogenisation.
  • Role of phytate in oat beta-glucan extracts in starch hydrolysis 
    Yang, Lingxi (2018)
    Oat β-glucans are water soluble non-starch polysaccharides. The health benefits of β-glucan including reduction of post-prandial glycemic response are correlated to its ability of forming viscous solutions. Phytate has also been reported to reduce starch digestion due to its potential of binding starch-digestion-related enzymes such as α-amylase or enzyme co-factors. The previous study showed that a significant amount of phytate was found in both oat β-glucan extract and highly purified β-glucan. The aim of this research was to study the role of residual phytate in the oat β-glucan extracts in starch hydrolysis. Oat β-glucan (OBG) was extracted from oat bran concentrate. OBG with phytate-removal treatment (OBG-PR) was prepared with ion-exchange resin and dialysis. The content of β-glucan, phytate and starch in OBG and OBG-PR were determined with Megazyme kits. The protein and calcium content was also measured. Before adding into the gelatinized wheat starch solution, the β-glucan solutions or phytic acid solution were pre-incubated with porcine pancreatic α-amylase. The starch hydrolysis was induced at physiological pH 6.9 and 37°C. Aliquots were collected at 20 min and 120 min digestion time. Digested starch was calculated based on the released glucoses. Both OBG and OBG-PR inhibited the starch hydrolysis. OBG contained a higher amount of phytate. And it had a stronger inhibitory effect (46%) than that of OBG-PR (34%). Pure phytic acid showed a comparable inhibitory effect on the starch hydrolysis as the OBG intrinsic phytic acid did, when the pure phytic acid was used at the same level as the concentration of intrinsic phytic acid in OBG. The decrease of intrinsic calcium in OBG-PR was found due to the ion-exchange and dialysis process. Consequently, the same amount of calcium was added to OBG-PR. The inhibitory effect of phytic acid on starch hydrolysis was completely reversed by the addition of calcium. Moreover, degradation of β-glucan by lichenase increased starch hydrolysis rate, which confirmed the role of β-glucan viscosity in the reduction of starch hydrolysis. In summary, the residual phytic acid of oat β-glucan, in addition to viscosity, reduced starch hydrolysis, while calcium contributed to promote starch hydrolysis.

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