Analytical Protocols for Quality Assessment of Acid Oils and Fatty Acid Distillates in Animal FeedIf you are interested in products related to the research phase in this field, please contact for further inquiries.
In the intricate web of animal nutrition, fat by-products play a pivotal role. Among these, acid oils (AO) and fatty acid distillates (FAD) stand out due to their high free fatty acid (FFA) content, derived from the refining processes of edible oils and fats. AO originates from the acidification of soapstocks during chemical refining, while FAD is a product of the deodorization step in physical refining. These by-products are not only economical but also serve as valuable energy sources in animal diets, enhancing the overall nutritional profile of feeds.
Fig 1. Quality assessment of acid oils and fatty acid distillates in animal feed. (Varona E., et al., 2021)
The variability in the composition of AO and FAD poses significant challenges in maintaining consistent productive parameters in animals. This variability underscores the necessity for stringent quality control measures. Without proper quality control, the inclusion of these by-products in animal feeds could lead to unpredictable outcomes, affecting animal health and productivity. Hence, the development and implementation of reliable analytical methods are crucial for ensuring the safe and effective use of AO and FAD in animal nutrition.
One of the primary aspects of quality control involves determining the fatty acid composition of AO and FAD. This is typically achieved through a double methylation process in a methanolic medium, followed by separation and identification using gas chromatography with a flame ionization detector. The method ensures complete methylation of FFAs, allowing for accurate quantification of fatty acid methyl esters (FAME). This data is vital for assessing the nutritional value of the by-products, as different fatty acids have varying impacts on animal health and metabolism.
Another critical parameter is the content of tocopherols (T) and tocotrienols (T3), which are essential liposoluble vitamins with antioxidant properties. These compounds are determined using high-performance liquid chromatography (HPLC) equipped with a fluorescence detector. Prior to injection, the sample undergoes saponification, and the unsaponifiable matter is extracted and analyzed. Quantification is achieved through external standard calibration, providing insights into the antioxidant capacity of the by-products, which is crucial for preventing oxidative damage in animal tissues.
The moisture and volatile matter content in AO and FAD significantly affect their stability and shelf life. The vacuum oven method, based on the AOCS official method Ca2d-25, is commonly employed. However, this method requires modifications when applied to AO and FAD due to their unique properties. For instance, lauric FAD, rich in medium-chain FFAs, can exhibit volatilization under vacuum conditions, leading to overestimation of moisture content. To mitigate this, adjustments in drying times and the use of alternative methods like the Karl Fischer titration are necessary.
Insoluble impurities, such as dirt and foreign substances, can adversely affect the quality of AO and FAD. These are determined by dissolving the dried sample in light petroleum ether and filtering the solution. The residue is then dried and weighed to calculate the percentage of insoluble impurities. Similarly, unsaponifiable matter, which includes sterols, hydrocarbons, and other non-saponifiable components, is quantified through saponification and extraction with diethyl ether. These parameters are essential for evaluating the purity and overall quality of the by-products.
The acidity, or FFA content, and the peroxide value are key indicators of the oxidative state of AO and FAD. Acidity is determined through volumetric titration with an ethanolic solution of potassium hydroxide, while the peroxide value measures the quantity of peroxides present in the sample. Both methods require careful optimization to account for the high FFA content and potential interference from other components in the by-products. Accurate determination of these parameters is crucial for preventing rancidity and ensuring the stability of the feeds.
The lipid classes in AO and FAD, including polymeric compounds, triacylglycerols, diacylglycerols, monoacylglycerols, and FFAs, are separated using size exclusion chromatography. This method allows for the quantification of each lipid class, providing insights into the digestibility and energy content of the by-products. Additionally, the oxidative stability of AO and FAD is assessed using the Rancimat instrument, which measures the induction time until rapid oxidation occurs. This data is vital for predicting the shelf life and storage conditions of the by-products.
The p-anisidine value (p-AnV) is a measure of the aldehyde content, primarily 2-alkenals and 2,4-dienals, in AO and FAD. These compounds are by-products of lipid oxidation and can adversely affect animal health. The p-AnV is determined spectrophotometrically, and modifications to the standard method are necessary to account for the presence of suspended particles in AO samples. Accurate determination of the p-AnV is crucial for assessing the oxidative quality of the by-products and preventing potential health risks in animals.
The application of analytical methods to AO and FAD presents several challenges due to their unique properties. Modifications to existing methods for crude and refined fats and oils are often required to obtain reliable results. For instance, the determination of moisture and volatile matter in lauric FAD necessitates adjustments in drying times to prevent volatilization of medium-chain FFAs. Similarly, the separation of lipid classes in lauric FAD requires highly selective methods like high-temperature gas chromatography-mass spectrometry. These adaptations ensure the accuracy and reliability of the analytical data, supporting the safe and effective use of AO and FAD in animal nutrition.
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This article is for research use only and cannot be used for any clinical purposes.
