ARTICLE Alternative Proteins Magazine October 2024 23 by-products. This acidification inhibits microbial growth, specifically yeasts, moulds and spoilage bacteria, thereby preventing protein degradation and helping retain amino acid profiles, crucial for the nutritional quality of animal feed. Animal feed producers may incorporate the complete byproduct or extract the protein component depending on their nutritional needs or by-product quality. Regardless of intended use, BSG and DDGS are treated at the production site or at trader facilities. If only the protein component is desired, then the protein extraction process begins. That process may include drying the BSG for efficacy before particle size reduction using mechanical grinders, like hammer or roller mills, occurs. The BSG is mixed with water to adjust the pH to a base level of 9-11, at which point proteins become soluble. As moulds and yeasts can survive in a basic environment, the initial acidification step before processing is vital to prevent the degradation of the extracted proteins. Once the pH is raised using mild alkali, the mixture is stirred for 1-2 hours to allow protein solubilization. Then the slurry is centrifuged or filtered to separate the solid or residual fibre from the liquid containing the solubilized protein. The solubilized protein is then dried to a powder that can be easily stored and incorporated into animal feed. The protein extract can be mixed with other nutritional components like vitamins or minerals depending on the feed requirements of the specific target species. The protein concentrate is typically pelletized into animal feed to ensure uniform distribution and ease of consumption. Other high moisture by-product streams rich in protein are whey (a by-product of cheese making), brewer’s spent yeast (a by-product of beer brewing) and wet corn gluten feed. These by-products are also prone to microbial spoilage and protein degradation if not properly preserved. In unpreserved whey and spent yeast, microbial activity can lead to protein hydrolysis, resulting in the breakdown of proteins into smaller peptides and amino acids, which could reduce their nutritional value and digestibility for animals. Whey typically has a pH around 6.0-6., while brewer’s yeast may have neutral pH at around 7. Acidification to a pH of 3.54.5 creates unsuitable conditions for microbial growth while still being safe for proteins. To optimise the extraction of protein for animal feed, Selko Yeast Inhibition organic acids blends are often used to stabilise and preserve these by-products prior to extraction.
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