Transglutaminase and tyrosinase as potential cross-linking tools for the improvement of rheological properties of gluten-free amadumbe dough

Gluten-free bread remains of poor quality despite efforts to amend gluten-free flours with ingredients such as hydrocolloids and proteins. Enzymatic modification of the proteins in dough may result in polymers that mimic gluten. This research investigated the effects of transglutaminase and tyrosinase on the rheological properties of amadumbe dough. Tyrosinase oxidation resulted in a 7.7–39.4% decrease in dough-free amine, and a 16.8–46.3% decrease in the dough thiol content as activity was increased from 0 to 80 U g⁻¹ flour. Transglutaminase treatment decreased the dough-free amino groups by 10–38.1% as activity was increased from 0 to 2 U g⁻¹ flour. Evidence of tyrosinase and transglutaminase-mediated cross-linking was provided by relevant model reactions monitored by mass spectrometry. An increase in dough G′ and G″ showed that both transglutaminase and tyrosinase improved dough viscoelasticity. The increase in the viscoelasticity of the dough potentially improves carbon dioxide retention during proofing.     

Laccase-generated tetramethoxy azobismethylene quinone (TMAMQ) as a tool for antioxidant activity measurement

The potential of laccase-generated tetramethoxy azobismethylene quinone (TMAMQ) for measuring antioxidant activity of a wide range of structurally diverse molecules present in food and humans was investigated for the first time. All the tested antioxidants including simple phenolics, polyphenols and vitamins quenched TMAMQ. The antioxidant activity of phenolics and polyphenolics depended on the position and number of hydroxyl groups on the benzene ring. Equally interesting was the ability of amino acids like cysteine, tryptophan and methionine as well as peptides (glutathione) and proteins (albumin) to quench TMAMQ, demonstrating the great potential of TMAMQ for analysis of antioxidant activity of serum samples. Further, TMAMQ is promising is a more reliable tool for measuring antioxidant activity of amino acids when considering conflicting reports on antioxidant activity of some of the amino acids. The extracts from various food samples showed varying antioxidant activity with highest for spinach (4.36 mg methanol extract/mmol TMAMQ) followed by kiwi (13.95 mg methanol extract/mmol TMAMQ) and lettuce (40 mg methanol extract/mmol TMAMQ). The use of the laccase generated TMAMQ can be exploited for the development of laccase based biosensors for complex and coloured samples thereby facilitating online monitoring of antioxidants in food, cosmetic and health industries.