ARTICLE 24 Alternative Proteins Magazine October 2024 BREWER’S SPENT YEAST PROTEIN EXTRACTION Live yeast cells that are used for alcohol production have a thick cell wall, so physical, mechanical, or enzymatic disruption is often required to break the cells and release proteins. These steps may include heating, centrifuging or treatment with specialised enzymes, but some extraction methods are more expensive than others. The industry’s preferred method is direct steam application or heating live yeast to 80°C, which can produce protein degradation. Selko Revalet offers a cheaper solution for yeast inactivation and protein preservation and avoids damaging heat treatments and additional energy consumption. In a research trial comparing the protein content found in brewery spent yeast that was untreated, heat treated or treated with a blend of organic acids, the acidified content maintained 6.48% protein content - almost the initial 6.6% content – for 7 days, while the heat-treated product fell to 3.8% during that period (Figure 1). However, Selko Revalet not only inactivates live yeast cells, once the cell is destroyed, proteins are released in yeast extract and will remain in the same concentration. Additionally, adding the organic acid blend prevents microbial proliferation during transportation and storage of the yeast extract. When an enzymatic treatment is added to create cell disruption and provide proper preservation of the yeast extract, it also helps maintain the proteins for solubilization using the process as described earlier in this article. Since the yeast has been preserved with Revalet the proteins are more likely to remain intact, which improves the efficiency of the extraction process. IN CONCLUSION The treatment of high-moisture by-products with Selko Yeast Inhibition solutions plays a crucial role in preventing microbial proliferation and preserving the integrity of proteins for subsequent extraction. Lowering the pH of these by-products creates an environment that inhibits the growth of bacteria, moulds and yeasts. By controlling microbial spoilage, these solutions prevent the breakdown of proteins by microbial enzymes, ensuring that the proteins remain intact for efficient extraction and use in animal feed. Once stabilised, the protein extraction process can proceed with minimal degradation, leading to higher protein yields and improved quality. These proteins can then be incorporated into animal feed formulations, providing a nutritionally rich, affordable, Protein content (wet basis), % 6.6% 4.6% 0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% BSY BSY + 0.4% RS BSY + 0.5% RS BSY-Heat treatment HT + 0.4% RS HT + 0.5% RS t=0 t=3 days t=7 days Figure 1. Brewery spent yeast treated with Revalet Super (RS) and Heat (HT). A decreased protein content is noticed when yeast is treated with heat from 6.0% to 4.60% with moisture content of 80%. Revalet reduce protein loses vs heat treatment.
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