مجله میکروبیولوژی کاربردی در صنایع غذایی
سال چهارم شماره 4 (زمستان 1397)

Mastineh is one of the traditional nomadic dairy products of Iran. This product is made from heated dough. Then the dry shevid, persian shallot, cucumalonga and other vegetables were added and mixed well. Although this product is rich in fiber, no probiotic product has been made so far, one of the reasons is that probiotic bacteria are susceptible to hot filling packaging. Therefore, in this study, Bacillus coagulans spore in the concentration of 10 log cfu/g was added to mastineh. The results of the tests showed that this bacterium reduced the acidity at the end of the storage period but did not affect the pH. Bacillus coagulans count decreased during the storage period, but Bc survival was higher than the recommended minimum limit of 6 log cfu/g during 28-day storage. Investigation of L* parameter in probiotic mastineh showed that this parameter decreased during storage time, but it was constant in control one. The a* parameter did not have a significant change in both types of mastinah during the storage period. Also, there was no significant difference between the control probiotic mastineh in the b* parameter. There were no significant differences were showed between the two samples in sensory evaluation and rheological parameters. The evaluation of free fatty acid profile also showed that the highest amount of fatty acids was related to palmitic acid, myristic acid, stearic acid and valeric acid. According to the results, the Bacillus coagulans can be used as a suitable probiotic in the mastineh.

In this study, the chemical compositions, total phenolic content, antioxidant power and the antimicrobial effect of Heracleum lasiopetalum essential oil on Enterobacter aerogenes, Pseudomonas aeruginosa, Staphylococcus aureus, Listeria innocua and Candida albicans were determined. The essential oil was extracted by hydrodistillation. Its chemical composition was determined through gas chromatography-mass spectrometry in comparison with standard mass spectra. Total phenolic content and antioxidant activity were measured using the Folin-Ciocalteu and DPPH scavenging methods. The essential oil antimicrobial activity was quantified by disk diffusion, well diffusion agar, minimum inhibitory concentration and minimum bactericidal/fungicidal concentration methods. Eucalyptol was the major constituent of the essential oil with a percentage of 30.75. The total phenolic content and antioxidant power of the essential oil were 35/44±0.95 mg GAE/g and 24.20±1.60 mg/ml respectively. The antimicrobial activity based on disk diffusion and agar well showed that Candida albicans was the most sensitive species to the essential oil. The minimum inhibitory concentration of the essential oil was equal to 16, 16, 4, 8 and 4 mg/ml for Pseudomonas aeruginosa, Enterobacter aerogenes, Staphylococcus aureus, Listeria innocua and Candida albicans respectively. The results of the bactericidal and fungicidal concentrations were totally equal to or higher than those of the minimum inhibitory concentration. The results revealed that Heracleum Lasiopetalum essential oil has appropriate antioxidant power and is able to control the growth of foodborne pathogens and can be utilized as a natural preservative in food industry.

In the current study the effect of probiotic bacteria type (Lactobacillus plantarum, Lactobacillus acidophilus and equal ratio of their combination), and honey addition (5% w/w) on qualitative and nutritional characteristics (proximate analysis) including total solids, ash, water soluble solids (Brix), lipid, protein, total carbohydrate contents, total phenols and sensory properties of rice–based functional beverage were evaluated. Furthermore, viability of the probiotic bacteria during 15 days of storage at a refrigerated temperature were investigated using first order, Gompertz, Logistic, Richards, Stanard, Schnout modified and proposed models. The results showed that using equal ratio of bacterial combination and honey leads to the production of probiotic functional beverage with suitable qualitative, nutritional, and sensory characteristics. Among the used models, viability of bacteria follows the modified Schnute and proposed models. Estimation of viability by these models showed that, until the 25th day (10 days after the end of the storage period), viability of bacteria was in the acceptable range for the probiotic products (Log 6 cfu/ml).

In this study, a synbiotic drinking dessert containing lactic cheese whey was prepared using Lactobacillus paracasei and Lactobacillus rhamnosus GG as low-lactose non-fermented and fermented forms. The results showed that the fermentation process of these two bacteria is too slow, compared with other probiotic bacteria. After about 24 hours of incubation, the pH of samples containing L. paracaei was 5.2 and L. rhamnosus GG was 5.6. The results of pH and acidity analysis showedsucrose in both samples and glucose produced by enzymatic hydrolysis in non-fermented samples caused acid production and consequently reduction of pH of samples during cold storage. The most reduction in pH of both fermented and non-fermented samples was related to samples containing L. paracasei. As pH decreased, acidity increased, indicating that the drinking dessert compounds had no buffering properties. The reduction of the probiotic population in non-fermented samples after 7 days of storage in the refrigerator was not significant (p>0.05). In fermented samples, the probiotic count was almost constant in the refrigerator after 21 days of storage. In both fermented and non-fermented samples, the probiotic count was higher than108CFU/ml, indicating that the composition and nature of drinking dessert which had high viscosity, could support the survival of probiotic bacteria. The sensory evaluation also showed in both fermented and non-fermented groups, the sample containing L. rhamnosus GG had a higher overall acceptability and the overall acceptability of non-fermented samples was higher than overall acceptably of fermented form.

Encapsulation of probiotic cells is a novel method for enhancing the viability of probiotics in food and simulated gastrointestinal environment. Probiotics and thymus vulgaris l. exctract (TVE) have numerous potential health benefits. TVE had also positive effects on the survival of some probiotic bacteria in food products or during exposure to gastrointestinal conditions. In this study, Lactobacillus acidophilus cells and TVE in different concentrations (500, 1000 and 1500 μg/ml) were co-encapsulated in chitosan coated alginate beads, and their ability to protect cells under high temperature (80 and 90 °C), stomach environmental condition (pepsin, pH=1/5) and intesine (pancreatin and bile salts, pH= 8) were investigated. Small spherical microparticles having antioxidant activities and high bacterial cells.The coating of these microparticles with chitosan along with TVE was an efficient way to protect cells from conditions encountered in the upper part of the gastrointestinal tract and high temperature and increased the survival of encapsulated bacteria in simulated gastrontestinal conditions compared with free and encapsulated bacteria without extracts (p < 0.05).The co-encapsulation of bacteria with 500 and 1000 μg/ml TVE provided an additional protection to the cells in gastric conditions (p < 0.05). This study indicates that chitosan-alginate beads could be a new carrier for the combined delivery of viable probiotic cells and TVE to the lower part of the gastrointestinal tract.

In this study, alfalfa at 55 percent dry matter content was inoculated with Lactobacillus buchneri and Pediococcus acidilactici and ensiled in four tons' capacity silo. The effect of replacing alfalfa hay with the provided silage on growth performance of Shal lambs was then evaluated for 84-day experimental period. Fourthy eigth male Shal lambs (28±2 kg live weight) were divided randomly into 4 treatments. The forage: concentrate ratio was 40: 60 in all experimental rations. The forage part of the ration (alfalfa hay) was replaced by alfalfa silage at the levels of 0, 33, 67, and 100 percent for each treatment groups. Dry matter intake (DMI), live weight and daily weight gain were recorded and the feed conversion ratios (FCR) were calculated for each treatment at 28 day intervals periods. Ensilage of alfalfa with the bacterial inoculant resulted in a decrease of water soluble carbohydrates and NDF content of alfalfa (p<0.05). Live weight and DMI was not affected by replacing alfalfa hay with alfalfa silage in the ration but daily gain and FCR was improved as the level of silage was increased in the rations during the first 28 days of experimental period (p<0.05). At the second and third 28 day periods, DMI was significantly increased in lambs fed only alfalfa silage (p<0.05). In this group, the DMI was also significantly higher than that of other treatments (p<0.05) for whole experimental period. Daily gain and FCR was also numerically improved in this group. It can be concluded that the use of bacterial inoculants may improve the fermentation process of alfalfa during ensilage and have a positive effect on performance of lambs by feeding this silage.