Document Type : Complete scientific research article
Authors
1
MS student of Food Science and Technology, Faculty of Biological Sciences, North Tehran Branch, Islamic Azad University, Tehran, Iran
2
instructor/Department of Food Science and Technology, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
3
Department of Analytical Chemistry, Faculty of Chemistry, North Tehran Branch, Islamic Azad University, Tehran, Iran
10.22069/fppj.2025.23145.1853
Abstract
Background and objectives: Inulin is a natural prebiotic found in various plants, including leeks, and is known for its health benefits, particularlyespecially in promoting gut health. Inulin can be extracted from plant sources by using various physical and chemical methods, and ultrasound-assisted extraction is considered a desirable technique due owing to its high efficiency. Combining inulin extracted from leek with foods such as yogurt can increase its nutritional properties while also providing prebiotic benefits. The aim of this paper study is was to investigate the effect of ultrasound-assisted inulin extracted from leek and to evaluate its effect on the physicochemical properties and viability of Lactobacillus plantarum in synbiotic yogurt.
Materials and methods: In this study, after preparing leek powder by the maceration method and using different solvents (water, methanol, ethanol and water/ethanol (v/v 50/50)), inulin extraction was performed using ultrasound treatment. Then, the total sugar content, reducing sugar, inulin content, degree of polymerization, and production efficiency of the extracted inulin samples were evaluated. To produce yogurt, cow's milk (1.5% fat), inulin powder (0, 1% and 2%) and probiotic bacterium Lactobacillus plantarum were used and the physicochemical properties and viability of Lactobacillus plantarum in synbiotic yogurt were evaluated during 14 days of storage.
Results: According to the results, the type of solvent (water, ethanol, water/ethanol and methanol), the type of sample (root and stem) and the treatment (without ultrasound and with ultrasound) had a significant effect on the total sugar (%), reducing sugar (%),inulin (%) and the efficiency of the extracted samples (p<0.05). The samples extracted with water had the highest percentage of total sugar (12/08%) and reducing sugar (28/8%), and the samples extracted with methanol had the highest percentage of inulin (36/5%). According to the degree of polymerization, the extracted samples were only affected by the type of solvent and type of sample, and ultrasound treatment did not have a significant effect on the degree of polymerization (p<0.05). Although the addition of up to 1% inulin up to 1% did not have a significant effect on the decrease in pH, increase in acidity, and survival of Lactobacillus plantarum in yogurt samples, increasing the concentration of inulin up to 2% caused a significant decrease in pH, a significant increase in acidity, and a significant increase in the survival of Lactobacillus plantarum (From 7.59 Log cfu/g in the control sample to 7.76 Log cfu/g in the 2% inulin treated sample) in yogurt samples (p<0.05).
Conclusion: The results showed that the sample extracted with methanol from leek root and ultrasonically treated had the highest percentage of inulin, degree of polymerization, and extraction efficiency. Although the use of 2% inulin in yogurt samples did not have a positive effect on reducing syneresis, it improved the viability of Lactobacillus plantarum in yogurt samples.
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