azam azimi mahalleh

The current study was carried out with the purpose of investigating the antimicrobial properties of free and microencapsulated extract of Nepeta Binaludensis. For this purpose, the Nepeta extract was extracted by assisting pulse electric field process (6000 v and pulse number 60). Then the effect of free extract (0.2 and 0.6 %) and encapsulated extract with 4 different types of wall material (wall contain mixture of maltodextrin 7 (26.97%) with Arabic gum (29.36%) and maltodextrin 20 (43.69%), wall contain mixture of 1% sodium alginate and 1% chitosan, wall contain mixture of 1% sodium alginate and 1% Inulin and wall contain mixture of 2% sodium alginate) at two concentrates (1 and 3 %) in comparison with synthetic potassium sorbate preservative (0.1%) on sensory, total phenolic content and microbial properties of doogh during 28 days storage at refrigerator temperature was evaluated. Results demonstrated that free and microencapsulated extract was able to control the growth of mold and yeast with preservation of sensory and phenolic properties in the doogh. The lowest growth rate of mold and yeast after 28 days of refrigeration was respectively observed in the sample containing 1% sodium alginate, 1% inulin at 1 and 3% concentration and 2% sodium alginate at 3% concentration and there was no statistically significant difference with the the sample containing 0.1% potassium sorbate (P>0.0.5). The results of sensory analyze showed that doogh samples containing encapsulated extract with 4 types of wall compositions mentioned were not statistically significant in terms of sensory characteristics with doogh samples containing potassium sorbate (P>0.0.5). Also, doogh samples containing microcapsules with wall composition (1% Sodium alginate and 1% inulin) and (1% sodium alginate with 1% chitosan) and 2% sodium alginate with a concentration of 3% after 28 days of storage had more phenolic compounds.

In this study, the effect of adding Bahar narang (Citrus aurantium) (400 ppm) and encapsulated Bahar narang extract (2000 ppm) and storage time (0, 7, 14, 21 and 28 days) on chemical properties (pH, acidity, and dry matter) and total phenolic compounds, microbial and sensory properties (flavor and overall acceptance) of doogh were evaluated. The results showed that the amount of free and encapsulated Bahar narang extract had a significant effect on pH, acidity, phenolic compounds and the total count of mold and yeast (P< 0.05). As the increased the amount of free and encapsulated Bahar narang extract, the pH and phenolic compounds increased and the amount of acidity, mold and yeast decreased significantly (P> 0.05). Storage time also had a significant effect on all measurement factors (P< 0.05). Over time, the amount of phenolic compounds in the control sample and the sample containing free extract decreased and the count of mold and yeast in the control sample and treatment containing free extract increased, but in the sample of doogh containing encapsulated extract no mold and yeast were observed until the 21 day of storage. Phenolic compounds were also preserved until the last day of storage. The results of statistical analysis of sensory evaluation of doogh samples also showed that with the addition of Bahar narang extract, the flavor score and overall acceptance increased (P <0.05). The results indicate that the addition of Bahar narang extract increases the shelf life of doogh and improves its sensory properties.

In this study, the effect of adding ginger (Zingiber officinale) essential oil (500 ppm and 1000 ppm) and storage time (1, 7, 14, and 21 days) on the physicochemical, microbial and sensory properties of yogurt was investigated. The results showed that the amount of ginger essential oil had a significant effect on acidity, synersis and the total population of mold and yeast (p < 0.05). As the amount of ginger essential oil increased, the synersis and the amount of mold and yeast decreased significantly, but the amount of ginger essential oil did not have a significant effect on the dry matter (p < 0.05). Storage time also had a significant effect on all measurement factors except acidity (p < 0.05). Over time, the amount of synersis and mold and yeast population in the control sample and treatment containing 500 ppm of essential oil increased and the pH decreased, but in the sample of yogurt containing 1000 ppm of ginger essential oil, no mold and yeast was observed until the last day of storage also pH remained constant during storage. The results of statistical analysis of sensory evaluation of yogurt samples also showed that with increasing the amount of ginger essential oil, the tissue score did not change significantly, but with increasing the amount of essential oil, the flavor and overall acceptance index increased (p < 0.05).The results show that adding ginger essential oil increases the shelf life of yogurt and improves yogurt sensory properties.