Abstract

The use of spent brewer's yeast (SBY) for yeast extract production is limited by the bitterness of iso-alpha-acids remaining from the brewing process. The adsorption of iso-alpha-acids onto macroporous resins was studied for the first time to develop a simple and sustainable process for debittering yeast extract from SBY. Four different resins (XAD-4, XAD-7HP, XAD-16N, SP-850) were evaluated for the debittering of yeast extract at two different temperatures. Adsorption kinetics were suitably fitted to a pseudo-second order model, assuming that solute adsorption is proportional to the available sites on the adsorbent. Resin SP-850 and a temperature of 25 degrees C were selected obtaining the highest equilibrium adsorption capacity of the resin (4.1 mg/g). The influence of pH and resin dosage were evaluated by the static adsorption method, selecting pH 6 and a resin dosage of 5 g/L. Resin regeneration with 60 % (v/v) ethanol solution allowed the removal of more than 90 % of the adsorbed iso alpha-acids. Three resin reuse cycles in yeast extract debittering showed effective regeneration, with iso-alpha-acid adsorption consistently over 80 %. A sensory test showed that enzymatic hydrolysis of debittered yeast extract enhances the umami intensity, highlighting its potential as a flavor enhancer and adding value to a brewing industry by-product.