Enhancement of gluten quality combined with reduced lipid content through a new salt-washing process

A salt-washing process to produce gluten with improved rheological properties having reduced lipid content was developed, initially using sodium chloride and subsequently with ammonium chloride. In laboratory experiments, the lipid content in gluten was reduced from 6.6% in the gluten control (washed out from flour with water only) to 5.7%, 3.6% and 2.7% in gluten salt-washed with increasing concentrations of NaCl from 0.5%, 1% to 2%, respectively. This was accompanied by the increase in the maximum creep strain of the salt-washed gluten (i.e. better gluten quality) with the increase in NaCl concentration. The new salt-washing process also improved gluten colour with reductions in b values (yellowness) and increases in L values (whiteness). Salt-washed gluten using 0.5% NH4Cl was comparable to gluten washed with 2% NaCl in lipid content and maximum creep strain. Extensograph tests showed increased dough extensibility for salt-washed gluten with 0.5% NH4Cl compared to water-washed gluten (the control). The improvements in gluten rheological properties and reduced lipid content using the salt-washing process were observed for flours with very different protein content and quality. The advantages of the laboratory-based process were retained when the process was scaled-up to a pilot batch process. The new gluten washing process offers several advantages for the industry including increased gluten yield, ease of gluten washing, superior rheological properties, and improved colour, with no extra capital costs being needed to alter conventional processing equipment. The advantage in using an ammonium salt over a sodium salt is that the volatility of the ammonium salt offers potential for its removal during gluten drying, leading to the virtual absence of salt in the final gluten. Starch quality was also improved by the process.