Soluble protein isolate from brewing by‐product (trub) using the Box‐Behnken design

Abstract

Brewing by-products, as trub, can be exploited as new nutrients sources, especially proteins. The objective of this study was to optimize the protein extraction from trub using the Box-Behnken design and response surface methodology to obtain a protein isolate and verify its antioxidants properties and phenolic compounds. Optimal extraction condition was at a pH of 12.31, concentration of 5.37 g/L, with 51.78 min of extraction at 80℃ (fixed temperature). Under these conditions, a protein isolate from trub was obtained (94.56% protein; 19.89% yield), its presented high water solubility (63.09 to 93.22%) over a wide pH range (6 to 12), high free radical scavenging capacity (63.03 and 186.07 TEAC μmol/100 g for DPPH and ABTS, respectively) and 35.36 mg gallic acid equivalents (GAE)/g of phenolic compounds. These results brings new information about a vegetable protein from a by-product enabling its extraction and applicability in different food matrices. Novelty impact statement Alkaline solution was efficient to extract the proteins from the trub, a beer production by-product that has been little reused. Vegetable protein isolate showed phenolic compounds, antioxidant activity and solubility in water over a wide pH range; and can be used as new protein source.