Poultry Processed Animal Proteins (PAP) and fat are mainly used in pet food recipes for their nutritional value. However, their high linoleic acid content makes them particularly vulnerable to oxidation. To counteract this, the rendering industry applies antioxidant solutions both before and after the cooking and separation phases, at multiple points throughout the process. This is the only way to achieve 3, 6, or even 12 months PAP shelf life as required by the pet food industry to accommodate long storage periods or overseas shipments.
Principal Technical Service Manager
Kemin Nutrisurance Europe
The pet food industry is providing more sophisticated end products to our pets with more complex formulations containing many sensitive ingredients which support different stressful processes.
To ensure healthy and palatable pet food products, manufacturers must use safe and non-oxidized ingredients. Even a single oxidized or poorly stabilized ingredient will generate fat pro-oxidation chain rapidly affecting the quality and stability of the final product.1 The pet food industry is significantly using high amounts of Processed Animal Proteins (PAP) and fats which can represent 20% to more than 50% of total formulations. However, these raw materials are highly susceptible to fat oxidation due to their fatty acids profile and the pro-oxidation stress of the rendering processes.
The rendering industry transforms slaughterhouse by-products into high quality PAPs and fats, each with a distinctive fatty acid profile depending on the animal species. Animal by-products with higher levels of unsaturated fatty acids, such as those from poultry or fish, are more susceptible to oxidation.2 This is because unsaturated fatty acids, especially polyunsaturated ones, have double bonds that are more reactive, leading to faster degradation and rancidity. Fat oxidation degrades nutritional value, reduces palatability3 shortens shelf life and can generate diseases in pets.4
Poultry PAP and fat are mainly used in pet food recipes for their nutritional value. However, their high linoleic acid content makes them particularly vulnerable to oxidation. To counteract this, the rendering industry applies antioxidant solutions both before and after the cooking and separation phases, at multiple points throughout the process. This is the only way to achieve 3, 6, or even 12 months PAP shelf life as required by the pet food industry to accommodate long storage periods or overseas shipments. Until now, the rendering industry in the EU has primarily used synthetic antioxidant molecules applied both before and after the cooking process. Occasionally, synthetic antioxidants are applied pre-cooking, while natural origin antioxidants are used post-cooking for cost-effectiveness.
As pet food manufacturers increasingly highlight natural claims on their packaging, the use of ingredients stabilized with synthetic molecules appears inconsistent and illogical. The biggest pet food manufacturers have requested Kemin Nutrisurance to develop efficient cost-effective natural origin antioxidant solutions for all ingredient stabilizations.
THE CHALLENGES
Trials’ Capabilities
The poultry rendering industry is engaging in the processing of huge crude raw materials through continuous or batch dry rendering processes from 10 to more than 300t/day.
Antioxidant molecules used before the cooking phase are mainly oil soluble. During the cooking phase, some of these molecules migrate into the extracted poultry fat. In certain processes, this fat —now containing synthetic molecules— is reused in the cooker to speed up the cooking process. As a result of this carryover effect, synthetic antioxidant molecules can contaminate subsequent batches of poultry PAP and fat.
The two main rendering technologies are based on dry rendering (with protein and fat separation after water removal) and wet rendering (with water removal after protein and fat separation). The dry rendering process is more stressful for PAP and fat.
To enable testing of multiple antioxidant molecules—individually, in combination, at various dose rates, in duplicate or triplicate, and across both dry and wet rendering processes while avoiding cross-contamination – Kemin Nutrisurance developed its own pilot rendering facility. Final selected solutions were tested afterward under dry rendering industrial conditions. Over the last 4 years, we conducted 203 cooking trials, tested 50 different molecules, treated more than 15 tons of crude raw materials, and carried out more than 17,500 wet chemical analyses.
Cost in Use
As mentioned, it’s crucial to protect the fat before it undergoes thermal stress. Applying antioxidants to crude raw materials significantly impacts cost-in-use due to the effect on protein yield, which typically ranges from 18% to 20%. For instance, if we don’t consider antioxidant migration into fat part, the cost factor for crude raw materials can range from 5 to 5.5, compared to a meal cost factor of just 1 when antioxidants are applied to dry PAP. The target is to reduce the stabilization cost of poultry crude raw materials by using the most cost-effective solution of natural origin.
THE DEVELOPMENTS
Pilot Trials
The first phase was dedicated to the mixed raw material validation, targeting standard poultry PAP (3.5 % Moisture, 64.8% Protein, 14.6 % Fat, 17.5% Ashes) before standardizing the dry rendering process in Figure 1.
For fat oxidation follow-up we systematically analyzed:
• Peroxide Value (PV) using AOCS method which measures the primary compounds of the auto-oxidation reaction, PV target <10 meqO2/Kg of fat till the end of shelf-life,
• Hexanal, as a marker for secondary compounds of fat oxidation deriving from different linoleic acid pathways, hexanal target <10ppm till the end of shelf-life,
• The recoveries of antioxidant molecules like Tocopherols and Carnosic acid from rosemary extract.
During the development of antioxidant blends, each molecule was tested individually and in combination to optimize the ideal ratio. The evaluation focused on identifying any lack of synergistic effects or potential pro-oxidative interactions, while minimizing cost-in-use.
Another part of the research was dedicated to enhancing the activity of antioxidant molecules in the different phases such as the emulsion and final meal. In the last part of the pilot evaluation, we studied the impact of the overstress during the different rendering pilot phases such as the cooking phase and the press effect. It supported the final formulation and especially the antioxidant molecule balance in the Verafyt™ LR-35 Liquid formula.
Industrial Trials’ Validation
To confirm the pilot trials’ results shown in Figure 2, we scheduled industrial trials using a discontinuous dry rendering process. First, the process was cleaned with Verafyt LR-35 Liquid to avoid synthetic molecules cross-contamination like BHA, BHT and Propyl gallate in the fat and the cooker.
Antioxidants were applied as per Figure 2: AOX 1 in crude raw materials and AOX 2 in PAP.
We treated the crude raw materials with 700 ppm of Verafyt LR-35 Liquid. The PAP were either treated or left untreated with different Verafyt LR-35 Liquid dosages as in Table 1.
We monitored the primary and secondary compounds of oxidation in PAP over 12 months at ambient temperature with no UV exposure. The peroxide values shown in Figure 2 remain under control after a 12 -month stability study in both samples (M-B and M-C) which were treated in poultry crude raw materials and PAP. Sample (M-A) with only crude raw materials treatment achieved almost 4 months of stability when PV curb crossed the 10 meq O2/kg fat max limit.
Complementary antioxidant treatment in the PAP at the AOX 2 application point increase drastically the PAP shelf life which confirms the absolute needs of the PAP treatment at the end of the dry rendering process. PAP complementary treatment by Verafyt LR 35 Liquid in the meal multiply more than 3 times the final meal shelf-life versus the PAP only treated on crude ABP.
Very low secondary compounds of oxidation like hexanal molecules resulting from linoleic acid oxidation and degradation were recovered as shown by Table 2. Above 10 ppm Hexanal Pet food manufacturer considers the fat oxidized:
CONCLUSION
The Verafyt LR 35 Liquid formulation, with its specific balance of active molecules and carrier enhancement effects, can protect sensitive poultry crude raw materials during the stressful heating dry rendering processes phases. It provides more than 3 months of poultry PAP stability when only the crude raw materials are treated and more than 12 months of PAP stability when combined with PAP treatment at the end of the process.
This is the first time in dry rendering history we have achieved similar efficacy than synthetic antioxidants molecules at so low cost in use.
The pet food industry can fully and safely stabilize their end pet food products with natural origin molecules now.
References
1Krabbe, E. “Quality of raw materials” AMVEA Peru, 2013
2E.N. Frankel, Lipid oxidation 2nd edition. The oily Press, Bridgewater, England, 2005
3Petfood Technology, Watt publishing, 2003
4Dr. Turek, Purdue University, USA, The Journal of Nutritional Biochemistry
5Kemin Nutrisurance CLS KN 23124 _23137
6Kemin Nutrisurance SD-25-28111
About Frank Clement
Based in France, Frank Clement is a Principal Technical Service Manager (TSM) and the Kemin Application Solutions (KAS) Manager of Kemin Nutrisurance Europe. He coordinates EU antioxidant, preservatives, and palatability TSM team projects. During the past 11 years, he’s spent lot of time in slaughterhouses and rendering plants to evaluate the best strategy to preserve the freshness of raw materials and guaranty safe end pet food products. He has been at Kemin for 16 years, mainly focusing on antioxidation subject and especially on EU Natural Antioxidant transition. As a biochemist, he’s spent more than 34 years at the pet food industry and especially on the analytical part at the beginning of his career.
