Showing 3 results for Lactic Acid Bacteria
Sh. Darvishi, H. Lamea, F. Akbari Nakhjavani, F. Darvish,
Volume 8, Issue 2 (7-2004)
Abstract
The effects of growth of two strains of lactic acid bacteria on microbial flora of ground beef after packaging in air permeable packs were studied under workshop conditions. The strains isolated from dairy products were added to ground beef at a density of 104 CFU/g after identification and antibiosis test against indicator bacteria (Escherichia coli and Staphylococcus aureus). The two strains were Lactobacillus casei subsp. casei 102, and Lactococcus lactis subsp. lactis var. diacetylactis 202. Inoculated and control samples were stored for up to five days under aerobic conditions in cold storage facilities with a temperature fluctuation between of –1°C to 5°C). Enumeration of different bacterial groups (total aerobic microorganisms, lactic acid bacteria, Pseudomonas spp., coliforms, Staphylococcus aureus, fungi) and detection of Escherichia coli were carried-out during storage period. The number of lactic acid bacteria in samples inoculated with lactobacillus casei subsp. casei 102 (treatment 1) increased during storage period, whereas total number of aerobic microorganisms, Pseudomonas spp., coliforms, and yeasts reduced. In samples inoculated with Lactococcus lactis subsp. lactis var. diacetylactis 202 (treatment 2), the number of yeasts decreased considerablely. As a result, Lactobacillus casei subsp. casei 102 can be used as a suitable antagonist of spoilage and pathogenic bacteria in ground beef under aerobic Conditions in cold storage facilities with a temperature variation between –1°C to 5°C.
A Kochaki, A Sadeghi, F Shahidi, A Mortazavi, M Nasiri,
Volume 13, Issue 47 (4-2009)
Abstract
This study was intended to use the sourdough LAB containing specific starter cultures for Barbari bread production and reduction of its staling. For sourdough preparation, fresh microbial cells were collected by centrifugation from LAB cultures. Then 1.5% of flour (w/w) from these washed cells with the same amounts of wheat flour and tap water and 0.25% (w/w) active dry yeast extract, containing Saccharomyces cerevisiae were mixed. The effects of fermentation time (8, 16 and 24 hours), fermentation temperature (28, 32 and 36 ºC) and type of starter culture (Lactobacillus sanfransicencis, Lactobacillus plantarum and a mixture of both LAB) were analyzed in a completely randomized design with factorial experiment with 4 replications. Bread staling was determined by its measuring crumb hardness and specific volume in 1, 24, 48 and 72 hours after baking. Correlation between variables was obtained by multivariate regression, and regression models were exhibited. The results showed that sourdough had significant effect (p≤0.05) on reduction of Barbari bread staling at 1, 24, 48 and 72 hours after baking in comparison with control sample. Moreover, the sample prepared with Lactobacillus plantarum (24 h fermentation time and 32 ºC fermentation temperature) had the maximum specific volume and the least staling, 72 hours after baking.
M Sh.zeinodin, M Tadyoni, Sh Dokhani, S Soleymanian Zad,
Volume 13, Issue 48 (7-2009)
Abstract
Exo-polysaccharide (EPS) production by some lactic acid bacteria (starter) during fermentation could affect the physical properties of yoghurt. In this study, at first EPS content and its effects on physical properties of three traditional (S1, S2 and G) and one industrial (I) yoghurt samples were studied. The results showed that there was significant differences in fat content, solid non-fat content, pH, EPS content, viscosity, elasticity and sensitivity to syneresis among samples. Statistical analysis based on a completely randomized design revealed that a significant correlation exists between EPS content and viscosity as well as resistance to syneresis of the samples. Fat content and solid non-fat content of the samples showed no correlation with physical properties of the samples. In the second phase of the study, to remove effects of raw milk composition and to be able to attribute the results to the EPS producing activity of the starter, skim milk was used to produce yoghurt samples using yoghurt samples tested in the first stage only as sources of starter. In these yoghurt samples, there were significant differences between amount of EPS and physical properties of yoghurts. There was also a significant correlation between EPS content and physical properties of each sample.
