The use of essential oils (EOs) has attracted interest in the food industry due to their wide range of beneficial properties. In this study, a new functional yogurt was developed using 2 essential oils [Marjoram (M) and Geranium (G)], at 3 different concentrations (0.2%, 0.4%, and 0.6% vol/vol). The physicochemical properties (syneresis, viscosity, pH, and chemical composition), bioactivities (antioxidant activity, anticancer and antibacterial effects, total phenolic content (TPC), and total flavonoid content (TFC)), and sensory characteristics of the developed yogurt were evaluated. The findings indicated that the yogurts fortified with 0.6% M or G exhibited higher viscosity and lower syneresis compared with other treatments. The yogurt supplemented with 0.6% M displayed significant antibacterial activity against Listeria monocytogenes, Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli. In addition, the yogurt enriched with Geranium and Marjoram oils at a concentration of 0.6% had notably significant (P < 0.05) higher TFC levels compared with the control sample and other concentrations. In the same context, in terms of TPC, yogurt supplemented with 0.6% Marjoram oil displayed significantly (P < 0.05) elevated levels in comparison to the other samples tested. Yogurt enriched with Marjoram oil exhibited noteworthy antioxidant activity, followed by Geranium oil compared with the control samples. The yogurt supplemented with 0.6% M demonstrated strong radical scavenging activity, while the yogurt fortified with 0.6% G showed higher anticancer activity against HepG2 human liver carcinoma cells and oxidative stress enzyme activities. Among the various concentrations of EOs tested, the yogurts fortified with 0.6% M or G EOs exhibited the most favorable outcomes, followed by 0.4% M or G. To summarize, G and M EOs can be used as a potential nutritious ingredient and as a natural preservative for milk and related products.
Keywords: Functional yogurt; Marjoram and Geranium essential oils; antibacterial activity; anticancer activity; antioxidant activity.
The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).