STSM2 Report Aoife McCarthy

Phenolic extracts and protein hydrolysates from Brewers’ Spent Grain

Aoife McCarthy visited Prof. Monika Schreiner in Germany (15 days in April 2012).

Brewers’ Spent Grain (BSG) is a solid by-product of the brewing industry, produced in vast quantities. My research is focused on phenolic extracts and protein hydrolysates from Brewers’ Spent Grain (BSG) and their potential bioactivity. Current research has investigated the in vitro anti-oxidant activity of BSG phenolic extracts, with extracts (particularly from black BSG ) exhibiting anti-oxidant effects. There also appears to be a correlation between TPC and anti-oxidant potential, however it is unknown exactly what compounds are present in these phenolic extracts and hence it is unclear what is responsible for the anti-oxidant activity.

Since flavonoids have anti-oxidant potential, measuring the flavonoid aglycones present in the BSG phenolic extracts may explain the anti-oxidant potential exhibited by these compounds. The flavonoid aglycones and hydroxycinnamic acids were extracted and quantified using high performance liquid chromatography (HPLC) and mass spectrophotometry (MS). By measuring the compounds present in whole ground barley (raw material) and whole BSG, an overview of the change, if any, in flavonoid aglycone content of the barley grain through the processing steps from barley to BSG to phenolic extract could be seen.

In brief, the results of this work show that the brewing process (to give BSG) decreases the amount of hydroxycinnamic acids present. In addition, it has been shown that the roasting of the barley grain (as is the case for black BSG) causes a greater decrease in hydroxycinnamic acid content, with the pale BSG and pale extracts having higher quantities than corresponding black BSG and black extracts. It was found that aqueous phenolic extraction releases caffeic acid derivatives, whereas alkaline extraction releases different compounds; namely ferulic acid and p-coumaric acid and their derivatives. There were no flavonoid aglycones detected in the samples.

A joint publication of the acquired data will be prepared, and the results will also be included in my PhD thesis. I would like to thank the COST Action UV4Growth (FA0906) for giving me the opportunity to carry out this STSM and allowing me to visit Leibniz-Institute of Vegetable and Ornamental Crops.