Food Protection Trends - March 2009 - 158

FIGURE 1. Survival and growth of Salmonella in BHI broth at 37°C for 24 h with different concentrations of chive extract (readings are average of three replications). the analysis of data, with use of Duncan’s multiple range to determine significant differences (P < 0.05). At least three replications of each experiment were conducted, with two samples per treatment at each sampling time. RESULTS AND DISCUSSION Table 1 shows the MIV, MLV and zone of inhibition for each strain. The average MIV and MLC were 235 µl/ml and 747 µl/ml, respectively. The minimum MIV was 180 µl/ml for Salmonella Tyhimurium ED404, and the maximum was 300 µl/ml for Salmonella Montevideo ED238. The lowest MLV concentration was 650 µl/l, found for both Salmonella ED430 and Salmonella sp. The highest MLV, 900 µl/ l, was associated with Salmonella Heidelberg ED377 and Salmonella Montevideo ED238. The largest zone of inhibition (5.35 mm) was observed with Salmonella Arizonae ED11, Salmonella sp., and Salmonella Tennessee ED178. The smallest zone, 4.01 mm, occurred with Salmonella Typhimurium ED405. Figure 1 shows the survival and growth of the Salmonella mixture strains in the presence of different concentrations of chive extract in BHI broth over 48 h at 37ºC. When Salmonella strains were grown in BHI broth samples without chive extract, populations reached the stationary phase within 12 h. Turbidity readings reached absorbance of 1.0–1.2 (610 nm). Addition of chive extract to BHI broth caused significant growth inhibition within 12 h (P < 0.05). Growth inhibition ranged from 50 to 100% within 8 h of incubation at 37ºC. After 24 h, the growth of Salmonella continued, but at a significantly lower rate than for the control samples (P 5%) enhanced growth inhibition, but not to values significantly greater than those associated with 5% chive extract. These findings clearly showed that the chive extract had strong antibacterial activity against all 38 strains of Salmonella. Evidence of this activity is indicated by the achieved inhibition levels; the average MIV was 235 µl and the average MLV was 747 µl. Assessment of inhibition over time showed that a minimum of 500 µl was required to cause total growth inhibition within 24 h. Table 1 shows the survival and growth of Salmonella in chicken and beef broth samples during incubation at 37°C for 48 h. In chicken broth, the population of Salmonella increased from 3.11 log CFU/ml to 7.4 log CFU/ml (P < 0.05) for the control sample and decreased from 3.10 log CFU/ml to 1.78 log CFU/ ml for the sample treated with chive extract. This indicates that chive extract caused significant growth inhibition of Salmonella (P < 0.001). Similar results were obtained with beef broth samples, in which the population of Salmonella increased from 3.19 log CFU/ml to 8.67 log CFU/ml (P < 0.05) for the control sample and decreased from 3.21 log CFU/ ml to 2.10 log CFU/ml for the sample treated with chive extract. This shows that all treatments reduced populations of Salmonella compared to the control. Chicken and beef broth were selected as food models because both products are high in nutrients required for the growth of bacteria, including Salmonella. However, we observed a higher population of Salmonella in beef broth samples than in chicken broth samples (P < 0.05). This could be due to the presence of extra nutrients in the beef extract that support 158 FOOD PROTECTION TRENDS | MARCH 2009

Food Protection Trends - March 2009

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