Microencapsulation of probiotic cells within emulsion is an efficient method to enhance the viability of probiotic bacteria. In the present study, free and encapsulated probiotic cells (Lactobacillus rhamnosus and Lactobacillus plantarum) in simple and multilayer emulsions were used to produce a set of probiotic yogurts. In all samples, an increasing trend in syneresis and acidity values and a decreasing trend in pH and viability of probiotic cells were observed during the storage time. However, the changes in these parameters were more significant for free-loaded probiotic samples. Moreover, the free cells showed poor survival in the yogurt samples by decreasing the viable cell count of probiotics from 7.71–7.59 logs CFU/mL to 6.93–6.82 log CFU/mL during storage, while encapsulation in the multilayer emulsion showed an insignificant reduction from 7.65–7.59 logs CFU/mL to 7.55–7.45 log CFU/mL at the end of storage. The obtained results showed that the type of probiotic bacteria had no significant effects on the physicochemical and structural properties of samples. However, encapsulating probiotics in multilayer emulsion led to a more homogenous structure in yogurt. The sensorial properties were also not affected by the probiotic type and the encapsulation method. Consequently, the multilayer emulsion can provide an ideal delivery carrier for encapsulating probiotic bacteria in dairy products.
Lactobacillus is a genus of gram-positive bacteria of high probiotic value. The bacteria of this genus are responsible for maintaining and promoting the microbial balance of the human gut, where they along with promoting better digestion and absorption, also help in suppressing many infectious diseases. Iranian traditional yogurt (Mast) is a rich source of Lactobacillus microorganisms and their identification can be explored for their use in industrial probiotics. This study is aimed at isolation and identification of different Lactobacillus strains present in the Mast. Forty samples of Mast from eight different regions of the Iran were cultured in De Man, Rogosa and Sharpe agar (MRS) media for isolation. The isolated strains were identified by morphological and biochemical methods using gram staining, catalase, oxidase, motility and indole tests. For biochemical identification, the isolates were subjected to carbohydrate fermentation test using phenol red broth base. Overall eight strains were majorly identified based on biochemical and morphological screening which were further confirmed using 16S rDNA-based identification. Two strain of Lactobacillus acidophilus, two strains of Lactobacillus bulgaricus, two strains of Lactobacillus delbrueckii and two strains of Lactobacillus casei were identified. Lactobacillus delbrueckii subsp. Bulgaricus isolated from Bushkan showed higher bile salt resistant activities (18.92, 13.56 and 10.22%) than that of the available Lactobacillus bulgaricus strain (3.08, 1.87 and 1.44%) in 0.3, 0.5 and 1.0% bile salt. This study thus provides insights into probiotic potential of Mast which could be explored in industrial yogurt and cheese production. HIGHLIGHTS Insight into Lactic Acid Bacteria profile of traditional yogurt of Iran. The Lactic Acid Bacteria profile varies from region to region. Proposes possible probiotics for commercial yogurt production from traditional yogurt of Iran.
Rice is one of the most highly consumed foodstuffs in the world. In keeping with this, produced rice of many regions of the world contains high lead content. The present research was done to study the effects of the pre-cooking process of rice with acetic acid and citric acid on the concentration of lead. Rice samples were divided into 5 different pre-cooking treatment groups of soaking in acetic acid 1% and soaking in citric acid 1% (2 hrs), boiling with acetic acid 1% and boiling with citric acid 1% (20 min) and finally 6 times rinsing with deionized water. Then, measurement of lead remains was done using an atomic absorption optical spectrometer equipped with a detector of graphite furnace with deuterium lamp. The mean concentration of lead in primary rice samples without any processing operation was 87±4.8 ppb. The mean concentration of lead in rice samples processed with soaking in acetic acid, soaking in citric acid, boiling with citric acid, boiling in acetic acid and finally 6 times rinsing with deionized water were 55±3.8, 14±1.6, 32±2.4, 14±1.1 and 30±0.5 ppb, respectively. The highest reeducation percent of lead in rice samples was obtained in both soaking with citric acid and boiling with citric acid (84%). In keeping with the high concentrations of lead in studied rice samples, obtained concentrations were lower than the allowed limit of lead announced with the international standard organization of Iran (150 ppb). Boiling and soaking of rice samples with citric acid 1% can be a convenient and fast way to reduce the concentration of lead in rice samples.
Viability of probiotics in the foods and human bodies is important, because a certain minimum count of bacteria is necessary to impose health promoting effects. In the present work, we encapsulated Lactobacillus reuteri within whey protein isolate (WPI), soy protein isolate (SPI), WPI + inulin (WPI4I), and SPI + inulin (SPI4I) through spray drying method and investigated the efficiency of the microcapsules on the protection of the cells under different conditions (heat, salt, bile salt, penicillin, pH, simulated gastrointestinal condition, and storage). The particle size of the samples was in the range of 195.2–358.1 nm. The sensitivity of unencapsulated bacteria to heat was considerably higher than that to the encapsulated bacteria, so that, at 80°C, no growth (of unencapsulated type) was observed. At 60°C and 40°C, the cell count of free bacteria decreased to 5.81 and 8.04 log CFU/mL, respectively. The bacteria encapsulated within SPI4I showed the highest viability at these temperatures. A comparison between the effects of different pH values showed pH 1.5 more lethal than 2.5 and 7. The effect of NaCl at 4% concentration on decreasing the bacterial count was more notable than 2%. However, the used wall materials in all conditions resulted in higher viability of the cells compared to the free cells. Among different types of wall materials, it was observed that WPI4I imposed the best protective effect. The higher viability of cells within WPI4I wall material was also observed during the storage time. The viability of encapsulated cells decreased from 10.35 to 10.40 log CFU/g in the first week and to 8.93–9.23 log CFU/g in the last week of storage.
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