Feed & Additive Magazine Issue 47 December 2024

ISSUE FOCUS FEED & ADDITIVE MAGAZINE December 2024 33 after thermal processing steps, ensuring the microbial safety of the fats is paramount. It can be a source of microbial contamination in pet food.6,7 When assessing contamination risk, the quality of the fat is crucial. Higher levels of impurities and moisture increase the risk. Purifying fat is essential, but some rendering processes can introduce microbial recontamination. To mitigate this, some rendering companies use heat treatment before loading the bulk fat. However, this doesn’t eliminate the possibility of contamination in two key steps: 1. During bulk loading: If the bulk contains unwashed residues with water, contamination can occur. Although bulk cleaning usually follows strict procedures, exceptions exist. 2. During unloading at the pet food manufacturer’s site: Reception tanks can be contaminated by residues, water, or external factors like dust and human contact. Wet cleaning in this dry processing environment is increasing the possibility of contamination and should be avoided if possible.8 Pulling that together, we begin to understand the complexity of this threat and the difficulty in solving it. Additionally, application of some acidifiers to bulk fat have been reported to potentially help in Salmonella reduction but may also increase lipid oxidation in fat and eventually cause the appearance of brown or black deposits.9,10 They are therefore only a partial answer to Salmonella contamination. Finally, it is good to keep in mind, while trying to avoid Salmonella contamination, that there are also regulations and market constraints. We tend to limit the use of some acids in pet food. The pet food manufacturers are also seeking for “clean” label, easy to read and natural claim. A SOLUTION TO PROTECT THE RENDERED FAT AGAINST SALMONELLA Avoiding Salmonella, keeping the oxidation under control, not adding “stress” on the production process, following the guidelines in terms of organic acid use and finally, if possible, still answering to the clean label/natural claim, those are the constraints faced by renderers and pet food manufacturers. Among the solutions to prevent Salmonella, many organic acids have demonstrated positive effects. This makes them a promising option for treating fats. Additionally, they can be naturally sourced, addressing another important requirement. Organic acids exist in two forms: dissociated and undissociated. Only the undissociated form is effective against bacteria. The more acidic the solution, the higher the concentration of the undissociated form. The pKa of an organic acid is the pH at which both forms are present in equal amounts. Lower pH levels increase the presence of the undissociated form, enhancing the acid’s effectiveness. To address the initial Salmonella issue, a solution should include an acidifier along with organic acid to adjust the pH of the aqueous portion of the fat. However, organic acids can accelerate product oxidation, so adding an antioxidant is necessary to tackle both microbial growth and oxidation. An optimized blend of natural acidifier and antioxidant offers dual benefits: protection against Salmonella risk and control of oxidation. One major challenge is the distinct lipid and aqueous phases in the fat, requiring an emulsion system for precise delivery in both phases. Kemin managed to combine these elements and has found a potential solution to prevent Salmonella in fat at destination of the pet food. This one now needs to be tested. MEASURING THE EFFICACY11 As previously discussed, acidifying rendered fat is a key step in stabilizing the pet food supply chain. Monitoring the pH changes based on fat treatment is crucial. At Kemin, this is done by creating a fat/ water emulsion. Comparing untreated fat with treated fat at various dosages shows a decrease in the pH of the aqueous phase: from an initial pH

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