Composition and Nutritional Value of Acid Oils and Fatty Acid Distillates Used in Animal Feeding

Abstract

Acid oils (AO) and fatty acid distillates (FAD) are oil refining by-products rich in free fatty acids. The objective of this study is their characterization and the identification of their sources of variability so that they can be standardized to improve their use as feed ingredients. Samples (n=92) were collected from the Spanish market and the MIU value (sum of moisture, insoluble impurities, and unsaponifiable matter), lipid classes, fatty acid composition, and tocol content were analyzed. Their composition was highly variable even between batches from the same producer. As FAD originated from a distillation step, they showed higher free fatty acid amounts (82.5 vs 57.0 g/100 g, median values), whereas AO maintained higher proportions of moisture, polymers, tri-, di-, and monoacylglycerols. Overall, the MIU value was higher in AO (2.60–18.50 g/100 g in AO vs 0.63-10.44 g/100 g in FAD), with most of the contents of insoluble impurities being higher than those in the guidelines. Tocol and fatty acid composition were influenced by the crude oil’s botanical origin. The calculated dietary energy values were, in general, higher for AO and decreased when a MIU correction factor was applied. The analytical control and standardization of these by-products is of the outmost importance to revalorize them as feed ingredients.

Oxidative Quality of Acid Oils and Fatty Acid Distillates Used in Animal Feeding

“…The presence of corn and palm AO in SP and SCP blends was also reflected in their γ-T3 content. In addition, as discussed in Varona et al [1], the two samples in the SU group with extremely high T contents could agree with the addition of tocol-rich products, such as deodistillates obtained from the deodorization step in chemical refining.…”

“…As a result of the usual availability of these products in the market, only 43 samples came from a single fat or oil, while most of the samples were blends obtained from the refining of different edible fats and oils (Table 1). 1 See the "Group" and "Botanical origin" columns for the definition of abbreviations. 2 For some blends the proportions were unknown.…”

Methods to determine the quality of acid oils and fatty acid distillates used in animal feeding

“…Of course, these selective methods will provide additional information, but they have not yet been applied to determine lipid classes in lauric fats and oils. This complex analytical problem should be addressed in the future since the relative quantity of triacylglycerols, diacylglycerols, monoacylglycerols and FFA affects the digestibility of fats in different animal species and therefore the dietary energy provided by these by-products, which is a crucial information to formulate feeds [5] .

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“…In the quality control of the fatty ingredients of feeds is very important to determine the amount of compounds that can dilute their energy content, such as moisture (M), insoluble impurities (I) and unsaponifiable matter (U) (globally known as MIU value) or the non-elutable material that includes MIU plus oxidized and polymerized fatty acids and acylglycerols [4] . In addition, it is important to determine the FFA content and the U/S ratio (the ratio unsaturated fatty acids to saturated fatty acids) because it is widely recognized that these parameters affect the digestible and apparent metabolizable energy of the fatty ingredients [ 4 , 5 ] However, the fatty ingredients also provide liposoluble vitamins, such as vitamin E, and other essential lipid nutrients, such as linoleic and linolenic acids that can be easily oxidized.…”

“…These methods were applied to 92 samples, 79 AO and 13 FAD, coming from the refining of vegetable fats and oils and intended for animal feeding ( Table 1 ). As these samples were very heterogeneous [5] , the application of these methods presented several drawbacks that were overcome to obtain reliable results for all types of samples. This article summarizes the drawbacks that were found during the setup of the analytical methods ( Table 2 ) and how were they overcome by adapting the methods.…”