SPECIAL STORY 56 FEED & ADDITIVE MAGAZINE December 2023 Although we can find both active ingredients in olive leaf and fruit, olive leaves are rich in oleuropein while olive fruits main ingredient is hydroxytyrosol. Oleuropein has shown an important antimicrobial effect as well as some endogenous antioxidant activity.5 Nowadays there are a number of supplements in the market for human but also for petfood claiming immune system boost thanks to the properties of oleuropein (just type on your web browser pet food supplement with oleuropein and you will find several companies offering such products). Unfortunately, as technological additive to control oxidation of fats and oils, oleuropein as such has shown a poor antioxidant activity in comparison with hydroxytyrosol and other known antioxidants.6 On the contrary, hydroxytyrosol has been demonstrated to be an ideal candidate to be considered as exogenous antioxidant to prevent the oxidation of feed and pet food relevant matrices.7,8 A few studies have proposed the mode of action of hydroxytyrosol, mainly by using radical scavenging reaction mechanism in which the hydroxytyrosol molecule can neutralized lipid radicals (ROO°). See figure 4. Kemin internal results have shown that the antioxidant activity of olive fruit extract can be enhanced by combination with known natural antioxidant molecules and that contrary to rosemary extract and carnosic acid, higher amounts of hydroxytyrosol in an olive extract do not necessarily mean better antioxidant activity.9 Several studies have shown that olive fruit extract containing hydroxytyrosol but not only shows antioxidant activity comparable to that of pure hydroxytyrosol, perhaps due to the presence of active derivatives of hydroxytyrosol and other phenolic compounds which promote synergistic effects in the extract that are not available when using the pure molecule. Further research is needed to elucidate the mode of action of the antioxidants present in the olive extract. References: 1https://ec.europa.eu/food/food-feed-portal/screen/ feed-additives/search accessed on 11th November 2023 2T. Masuda, Y. Inaba, Y. Takeda, J. Agric. Food Chem, 2001,49,5560-5565;; S. L. Richheimer, M. W. Bernart, G. A. King, M. C. Kent, D. T. Bailey, J. Am. Oil. Chem. Soc. 1996, 73, 507-514; 3M. Loussouarn, L. Krieger-Liszkay, A. Bily, S. Birtić, M. Havaux, Plant Physiol. 2017 Nov;175(3):1381-1394 4M. Fiorini, V. Crognaletti, O. Sabry, P. Fattori, Processes 2021, 9, 433. 5D. Borjan, M. Leitgeb, Molecules 2020, 25, 5946 6M.H. Gordon, F. Paiva-Martins, M. Almeida, J. Agric. Food Chem., 2001, 49, 2480-2485 7A.Y. V. Theah, T. O. Akanbi, Antioxidants 2023, 12, 929 8Martínez-Zamora, R. Peñalver, G. Ros, G. Nieto, Foods. 2021 Oct 28;10(11):2611 9Kemin R&D internal results About Dr. Cristina Murcia García Dr. Cristina Murcia García gained her PhD in Chemistry with focus on red-ox reactions from the University of Bonn (Germany). Since then, she has specialized in managing oxidation in rendering and pet food products. She works as Technical Service Manager for Kemin Nutrisurance Europe where she provides solutions to improve raw materials and pet food safety and shelf-life. Besides, she develops tailor-made trials and protocols for customers and holds customer specific trainings on topics like oxidation, freshness, and food safety. Figure 4. Proposed radical scavenging mechanism of hydroxytyrosol
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