Browsing by Subject "Fenton oxidation"

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  • Zhan, Ruzhen (Helsingin yliopisto, 2017)
    Cereal β-glucans are soluble non-starch polysaccharides. Both the health benefits and industrial applications of β-glucan have been correlated to its capability of forming viscous solutions. Oxidative degradation has been demonstrated to be the critical factor that causes the viscosity drop of β-glucan solutions. In oats and barley, more than 90% of the phytate was found in the soluble fiber fraction, most of which is β-glucan. Phytate has chelating ability to form phytate-mineral complexes. Therefore, phytate has the potential to suppress iron-catalyzed oxidative reactions and is hypothesized to protect β-glucan from oxidative degradation. The aim of this research was to study the role of both intrinsic and added phytate in the oxidative degradation kinetics of β-glucan. Fenton reaction was used to induce oxidation in both oat β-glucan (OBG) and barley β-glucan (BBG) solutions. Degradation of OBG and BBG was indicated by the decrease in molecular weight and viscosity. When the concentration of hydrogen peroxide kept constant, the extent of OBG degradation was found to be greater with increased iron concentration. Most degradation occurred in the beginning of the oxidation and OBG degradation in the initial 3 hours fitted well in the second order kinetics. The reaction rate constant (k) which stands for the degradation rate demonstrated a positive relationship with the iron concentration. Intrinsic phytate in OBG had a protective effect on β-glucan degradation induced by Fenton reaction. After phytate removal by ion exchange resin, degradation of OBG solution became faster with the same amount of oxidative reagents. As to the degradation kinetics, under the same oxidative condition, the k value increased after phytate removal. Added phytic acid also had a protective effect on the degradation of BBG solution, but the effect was not as strong as the intrinsic phytate in OBG. Furthermore, the strength of the protection was related to the PA/iron ratio. When the PA/ iron ratio was 2:5 , there was no protective effect of added phytic acid observed on the degradation of BBG. When the PA/ iron ratio was 2, the added phytic acid had protective effect. When PA/ iron ratio was 1:5, the added phytic acid had a more profound protective effect. In summary, our results demonstrated that both intrinsic phytate and additional phytic acid had a protective effect against the oxidative degradation of β-glucan. Addition of phytic acid in a proper ratio is of importance to maintain the stability of products containing β-glucan. Phytate or phytic acid is commonly considered as an antinutrient related to the mineral bioavailability in food intake. This study however showed an anti-oxidant effect of phytate in β-glucan solutions which suggests that it may have a beneficial effect in physicological conditions.