Protein recovery from whisky by-products: a study of using ion exchange chromatography for the recovery of proteins from pot ale

Abstract

Liquid and solid by-products samples from malt whisky (MW), grain whisky (GW) and brewing (B) origin across several Scottish distilleries and breweries were collected and analysed for physical, chemical and nutritional properties. Nutritional properties assessed included protein quantification. Among the by-products analysed, the focus in this work was placed on pot ale, the liquid by-product from MW processing. Approximately, 2-3 million tonnes of pot ale are generated in Scotland annually, with a protein content of ~1% protein (w/v) or 40% (w/w) on dry matter basis. Current technologies for the recovery of the protein from pot ale, i.e. evaporation, are expensive, require large amounts of energy and produce a low value product called pot ale syrup. A less energy intensive method with the potential to create a higher value product from pot ale was developed in this work using an ion exchange chromatography (IEC) technique that exploits protein electric charge. Pot ale proteins were found to be positively charged (due to low pH) and cation exchangers were used to bind pot ale proteins. The method was tested and up-scaled from 50 ml to 1400 ml of pot ale at flow rates from 1 ml/min to 30ml/ min. An economic analysis included in this work showed that using IEC for protein recovery from pot ale can be applied at commercial scale and the protein product used in higher value markets such as aquaculture.