ABSTRACT
The growing interest in substitution of chemical food preservative with natural ones has fostered researches on plant essential oils and extracts. The purpose of the current study was to evaluate the effect of Zataria multiflora Boiss. essential oil on growth respose, the percent of growth inhibitory and morphology of Penicellium citrinum. Different concentrations of the essential oil [0, 50, 100, 200, 400, 600 ad 1000 ppm] were used in agar dilution method to evaluate growth and spore production parameters. The cultured mold were studied by scanning electron microscope. Values among groups were compared using 1-way ANOVA. It was found that the effect of different concentrations of essential oil on radial growth and sporulation was statistically significant [p<0.05]. The minimum inhibitory concentration [MIC] and minimum fungicidal concentration [MFC] both were 400ppm. According to scaning electron microscopy the treatment with the oil led to alterations in hyphal morphology. Our results suggest that Zataria multiflora Boiss. essential oil can be used as a natural preservative against Pencillium citrinum in foods
Subject(s)
Penicillium/drug effects , Growth , Oils, Volatile , Microbial Sensitivity TestsABSTRACT
Currently, due to their beneficial effects, there is interest in adding prebiotics to food products. This study investigated the effect of the addition of inulin [1% and 2%] on microbial and physico-chemical properties of probiotic low fat yogurt manufactured with Lactobacillus acidophilus. Six experimental preparations of yogurt were produced. Homogenized, standardized and pasteurized low fat milk were divided into six portions. Four portions were fortified with 1% and 2% inulin and two portions were used without inulin. All of the preparations were heated up to 85 [degree sign] C and fermented at 43 [degree sign] C until a pH of 4.6 was reached. Titratable acidity and pH were determined using the incubation period of the samples and a storage time up to 14 days. Syneresis, color, sensory evaluation and bacterial counts were determined during the storage time. The results showed that inulin did not significantly affect the titratable acidity and pH of the yogurts after 4 h of fermentation at 40 [degree sign] C. There were no significant differences between pH, titratable acidity, syneresis, color and sensory evaluation of all treatments on days 1, 7 and 14 of storage. The counts of L. acidophilus and L. delbrueckii ssp. bulgaricus declined over time, but the addition of inulin to the milk increased the viability of these bacteria during the storage of symbiotic yogurt. In conclusion, inulin can be used to manufacture low fat symbiotic yogurt with additional nutritional benefits without affecting the physic-chemical properties of yogurt