1 Antimicrobial Effect of Cinnamon and Clove on Staphylococcus aureus in Milk and Yogurt Ahmed M. Hammad Department of Food Hygiene and Control, Faculty of Veterinary Medicine, University of Sadat City, Sadat City, Egypt. Key words ABSTRACT: Cinnamon, clove, S. aureus, antimicrobial effect As consumers have showed a concern for the reduction of chemical preservatives in food, the interest for natural compounds with antimicrobial properties has been investigated. In this study the acid potency and the antimicrobial effect of cinnamon and clove and their water extracts were tested in water and milk. Additionally, survival of S. aureus in yogurt inoculated with cinnamon and clove (0.3% conc.) during three days of storage was monitored. Clove and cinnamon showed strong acid potency in water as 2.5% concentration from both herbs dropped the PH of water to 5.4 and 6, respectively. However, the same concentration of both herbs had a slight effect on PH of milk as they lowered it to 6.5. Interestingly, 10% concentration of clove and cinnamon in water made zones of inhibition of 18 mm and 15mm, respectively. But, at the same concentration in milk only clove made zone of inhibition of 14mm. No zone of inhibition was observed at concentration equal to or below 5% of clove and cinnamon in milk. On the other hand, the mean counts of S. aureus in yogurt were similar in both control samples and samples treated with cinnamon and clove. The P value during three days of storage was above 0.05, indicating non-significant differences between the treated and control samples. In conclusion, the buffering capacity of milk and yogurt neutralize the acidity of cinnamon and clove and make them ineffective on S. aureus. Therefore, cinnamon and clove may improve the sensory quality of milk and yogurt but not provide any degree of safety against S. aureus in these products. *Corresponding Author : Ahmed M. Hammad; : hammad@vet.usc.edu.eg 1. INTRODUCTION The dairy industry is improving processing techniques to prolong the shelf life of milk and provide consumer with attracting sensorial characteristics of fluid milk and dairy products. In recent years, essential oils of plants are used to improve the flavor of drinks and food. Additionally, they are being used for their antimicrobial and antioxidant properties (Davidson and Naidu, 2000). Milk drinks flavored with cinnamon, clove, and other spices became popular in some countries as Spain and Latin American countries (Cava et al., 2007). However, in Egypt there is a trend to add these flavoring agents to milk intended for manufacturing of different types of dairy products. Staphylococcus aureus is found in the nose, and on the skin of warm-blooded animals. Up to 50% of the human population are carriers and animals act as reservoirs, especially cows with subclinical mastitis (Fitzgerald et al., 2001). Additionally, air, dust, and food contact surfaces can also serve as vehicles in the transmission of S. aureus to foods. S. aureus can grow in a wide range of pH, ranging from 4 to 10, with an optimum of 6 to 7 (ICMSF, 1996); temperatures between 7° to 48.5°C with an optimum of 30 to 37°C (Schmitt et al., 1990); and sodium chloride concentrations up to 25% (ICMSF, 1996). These criteria enable S. aureus to grow in many types of food and if the environmental conditions during food storage and preparation allow its growth, staphylococcal enterotoxins could be produced, being harmful for consumers (Todd et al., 2008; El-Leboudy et al., 2014). Nevertheless, it remains a leading cause of food poisoning. The growth characteristics of S. aureus beside its ubiquitous nature can explain its high incidence in foodstuffs that require manipulation during processing, including fermented food products, such as yogurt and cheeses. Consequently, several methods were used for controlling the growth of S. aureus in food including addition of natural herbs such as cinnamon and clove (Dorman and Deans, 2000; Prabuseenivasan et al., 2006; Sofia et al., 2007). Alexandria Journal of Veterinary Sciences 2016, Jan. 48 (1): 1-6 ISSN 1110-2047, www.alexjvs.com DOI: 10.5455/ajvs.203629