عنوان مقاله [English]
Introduction: One of the most critical factors affecting the health of any individual is nutrition. Patterns of food consumption play an important role in causing or preventing diseases. Functional Foods refer to products that, in addition to nutritional content, affect their consumers' health. Probiotic foods are considered to be viable products that contain sufficient quantities of probiotic microorganisms. Probiotics are live microorganisms (bacteria or yeast), which should be metabolically stable and remain active in the product; along the pathway before the digestion process, a large number of survivors reach the intestinal epithelial cells, colonize and leave beneficial effects on the host intestine, all of which can lead to increased host life. One of the types of probiotic bacteria is lactic acid bacteria. These bacteria can produce organic acids and bacteriocins and have antimicrobial activity (Tsai et al., 2010; Bonatsou et al., 2017). These microorganisms are easily adapted to fermentation conditions and can grow in high acid and salt conditions. These bacteria are non-pathogenic and capable of lowering pH through metabolic activities (Bonatsou et al., 2015). These lactic acid bacteria also reduce phenolic compounds and create a pleasing odor in the final product by creating volatile compounds (George-John &Nychas, 2017(. The selection of starter cultures depends on several aspects, such as type of studied medium, growth potential, acidifying capacity, salt and pH tolerance, probiotic potential, metabolic capacity.
The microbial debittering property of the selected starter is fundamental, and this route could be an alternative to chemical debittering. Lactobacillus plantarum is one of the most common bacteria of the genus Lactobacillus. This gram-positive bacterium can hydrolyze gelatin and grow well at 15° C but cannot grow at 45 °C. Production of antimicrobial agents by Lactobacillus plantarum helps the species survive in the plant. Today, the use of these bacteria in various foods is remarkable because of their prominent properties. One of these critical food products is olive. Therefore, in this study, we investigated the effect of Lactobacillus plantarum lactate starter, salt concentration, and acetic acid percentage on chemical and microbial properties of olives over 90 days at 28 ° C.
Material and methods: To carry out this study, 1 kg of olive pots were filled with two treatments (8% Nacl+ 0.1% acetic acid) and (6% NaCl +0.3% acetic acid). Then, on the fifth day of the test, the Lactobacillus Plantarum was inoculated. Bacteria-free containers were used as controls. Chemical tests, including acidity, pH, salinity, and peroxide measurements, were performed by the national standard of Iran. Microbial tests, including yeast and mold measurements using Sabourod Dextrose chloramphenicol agar medium, lactic acid bacteria measurement using MRS agar medium, and Thermophilus Bacteria, were performed using Thermosidorescent Agar medium, and Mesophilic Bacteria was measured using Orange Broth Serum. All treatments had three replications. One-way and two-way ANOVA and T-test tests were used to determine the mean and level of significant differences between treatments and controls in SPSS 23 software.
Results and discussion: The results showed that the burden of bacteria in Lactobacillus plantarum and control were significantly increased with increasing maintenance time (p < 0.05). In all two treatments, the decrease in NaCl level was 6% and increased acetic acid to 0.3% higher growth of lactic acid bacteria and mesophilic (p < 0.05). However, changes in NaCl and acetic acid levels did not cause a significant difference in the levels of thermophilic bacteria and yeast and fungi(p>0.05). The lowest growth of thermophilic bacteria and the highest growth of mesophilic and yeast and fungi were measured in the control treatment (p < 0.05). The highest growth of lactic acid and mesophilic bacteria and the lowest fungi and yeast were measured in Lactobacillus plantarum bacterial treatment. The results showed that none of the treatments were allowed to pass through the specified bacterial limit. The sensory and pH characteristics of olives were not affected by acidity and NaCl in all two Lactobacillus plantarum and control (p < 0.05). Comparison between treatments showed that the control treatment had the lowest sensory specificity, and Lactobacillus plantarum had the highest sensory score of olive (p < 0.05). Lactobacillus plantarum had the lowest pH level in similar NaCl and acetic acid levels, and control treatment had the highest level of this parameter. Acidity influenced the acetic acid level from the day 45 maintenance between the two NaCl treatments of 8% + Acetic acid 0.1% and NaCl 6% + Acetic acid 0.3% had a significant difference, and the treatment of olive with Lactobacillus bacteria had the highest level, and control treatment had the lowest acidity. The highest salinity level was observed in the control treatment, and the lowest was in Lactobacillus plantarum. According to the Iranian National Standard, the salinity of processed olives was 5% by weight, which exceeded the permissible limit for NaCl 8% + Acetic acid 0.1% bacterial Lactobacillus plantarum and control. The amount of peroxide as the primary oxidation index in NaCl treatments was 6% + Acetic acid 0.3% higher than 8% + Acetic acid 0.1%. The maximum number of olive peroxide is 20 mm Eq /kg, and none of the treatments were passed from the designated range.
Conclusion: Based on the findings of this study, it can be concluded that the use of lactic acid bacteria in the production of various types of food can help improve its nutritional and health characteristics. Lactobacillus plantarum is a probiotic bacterium in olive resulted in reduced microbial load and increased storage time in olive.