The role of mushroom polyphenols on enzyme inhibition : A Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

Shiitake mushroom (Lentinula edodes), black ear mushroom (Auricularia auricula) and silver ear mushroom (Tremella fuciformis) are a common type of mushrooms. Recent year, bioactivity phenolic compound isolated from them has been attended and investigated by researchers and further focusing on their inhibition of starch digestion as well as the improvement of quality of starch in the food industry. Therefore, we hypothesize that the pasting properties and hydrolysis of red sorghum flour may affect by bioactivity phenolic compounds inhibiting the digested enzyme, such as α‐amylase and intestinal α‐glucosidase, derived from the mushroom. The objective of this study was to investigate the extract bioactive polyphenolic compounds from three different species of edible mushrooms, namely shiitake mushroom, black ear mushroom and silver ear mushroom as ingredients. The results of this study suggest that water extraction at 50°C for 3 hours in neutral pH could obtain optimal extraction condition for a great TPC and antioxidant activity. Shiitake mushroom water extract was the highest TPC and antioxidant activity among all mushroom extract, followed by shiitake mushroom 50% ethanol extracts. Besides, addition with each mushroom extracts all reduced the pasting properties of red sorghum paste, in particular, peak viscosity and final viscosity. Shiitake water extract has a significant (p<0.05) high comparing with others. Moreover, the TPC, antioxidant activity and protein digestibility were observed an increasing trend during in vitro digestion of all red sorghum paste incorporated in each mushroom extracts, while the reducing sugar and AUC were significant (p<0.05) decrease. Shiitake mushroom water extracts remain to present the greatest TPC and antioxidant activity during in vitro digestion of red sorghum paste, followed by shiitake ethanol mushroom extracts. Our preliminary result supported that mushroom extract, ie. shiitake mushroom, black ear mushroom and silver ear mushroom could be used as a functional ingredient of red sorghum food products development, which provides bioactivity phenolic compounds and enhances antioxidant activity. What is more, it may display as a modification agent by decrease the hydrolysis of starch during digestion for further reducing sugar release as well as raising protein digestibility of red sorghum flour products.