Ekstrahowano kwasy jabłkowy i fumarowy przy użyciu wielkocząsteczkowych amin (trójoktyloaminy, Amberlite LA-1 i LA-2) rozpuszczonych w ksylenie oraz nitrobenzenie. Wykazano znaczący wpływ rodzaju rozcieńczalnika na wartości stałych równowagi tworzonych kompleksów kwas-amina. Ustalono występowanie kompleksów kwas-amina w szerokim zakresie proporcji od 1:1 do 3:2. Na podstawie uzyskanych wyników stwierdzono, że najbardziej odpowiednim układem do selektywnej ekstrakcji kwasu jabłkowego jest anionit Amberlite LA-2 rozpuszczony w nitrobenzenie.
In 2006 a ban on the use of in-feed antibiotic growth promoters was introduced. Since then the research focus has shifted to substances that can be used as effective alternatives to antibiotic growth promoters. Experience has shown that organic acids are the most reliable among non-antibiotic growth promoters available in Europe, which can also be used safely and effectively with other additives. Performance-promoting effects of organic acids and their salts can be observed in the feed, the intestinal tract, and metabolism. The effect of organic acids in animal breeding is related to feed preservation and to the reduction of the acid-binding capacity of feed ingredients. The effect in the intestinal tract is two-fold. The organic acids reduce pH in the stomach and the small intestine, stimulating the secretion of the digestive enzyme and promoting the growth and recovery of intestinal morphology. Furthermore, acid dissociation in bacterial cells and the accumulation of salt anions inhibit microbial growth. The effect on metabolism is revealed through the production of a certain amount of energy, and short-chain organic acids can be used for ATP generation in the citric cycle. Organic acids are commonly fed to swine, especially young pigs in the weaning period, and to poultry, however, they are increasingly popular as feed additives for other animals.