Background and objective: Presence of oxygen during production and rehydration of freeze-dried starters and probiotics can decrease viability of the bacteria. Indeed, removal of water from cells during freeze-drying can promote dysfunction in anti-oxidative mechanisms, resulting in oxidative stress by accumulation of reactive oxygen species. The aim of this study was to show how atmospheric or less oxidative gaseous conditions affect bacterial survival to freeze-drying and rehydration of two strains, including Lactobacillus casei, a widely used bacteria in biotechnology, and Escherichia coli, a laboratory model bacteria.

Material and methods: Lactobacillus casei ATCC 334 and Escherichia coli K12 were freeze dried for 24h in 5% sucrose (m v^-1). Two gaseous conditions (an oxygen-free gas and atmospheric air) were used during various steps of the process, including bacterial cultivation, mixing of the bacteria with the protectant and rehydration. Oxygen-free gas condition was obtained with an oxygen-free gas, composed of nitrogen, hydrogen and carbon dioxide (N₂H₂CO₂)and an anaerobic chamber.

Results and conclusion: Gaseous conditions included significant effects on bacterial survival rates (P<0.001 for Lactobacillus casei and Escherichia coli). Interestingly, for both bacteria, the optimal combination was atmospheric air during mixing of the bacteria with the lyoprotectant (P<0.001 for Lactobacillus casei and Escherichia coli) and N₂H₂CO₂ during rehydration (P<0.001 for Lactobacillus casei and P<0.05 for Escherichia coli). Management of gaseous conditions during a freeze-drying process and rehydration (atmospheric air during mixing of the bacteria with lyoprotectant and oxygen-free gas during rehydration) enhances survival of the bacteria by preserving them from oxidative stress.

Conflict of interest: The authors declare no conflict of interest.

Background and objective: Flaxseed oil, as a potential source of polyunsaturated fatty acids, is susceptible to oxidation. Yeast cells of Saccharomyces cerevisiae and β-glucan can be used as biocompatible and biodegradable matrices for the protection of this nutritious oil from oxidation in foods enriched with omega-3 fatty acids. The aim of this study was to investigate quality properties of breads containing encapsulated and free flaxseed oils.

Materials and methods: Flaxseed oil was encapsulated in either yeast cells or β-glucan. Functional wheat bread samples were prepared using unencapsulated and encapsulated flaxseed oils. These were compared with control samples in terms of dough rheological and bread quality parameters.

Results and conclusion: Encapsulation significantly increased dough rheological properties (G′ and G″ values), firmness and density and decreased lightness, compared to control samples. Breads, containing flaxseed oil encapsulated in yeast cells, showed a lower peroxide index and a higher α-linolenic acid value, compared to two other samples containing oil samples. This showed a better protection of unsaturated fatty acids against deleterious oxidation reactions. Results of this study indicate that addition of microencapsulated flaxseed oil into breads helps preserve sensory properties of the control sample, compared to breads fortified with free flaxseed oil.

Conflict of interest: The authors declare no conflict of interest.

Background and objective: Consumer interests in probiotic foods have increased in recent decades. Food industries respond to these growing interests by developing innovative products and guaranteeing high production efficiency. Cereals, due to their prebiotic nature, are good fermentable substrates; from which, potentially functional foods could be achieved. The aim of this study was to verify effects of D-glucose addition on fermentation of rice, oat and wheat flours.

Material and methods: Suspensions of 15% of cereals flours (rice, oat and wheat) in distilled water added with increasing glucose concentrations (2, 5, 7 and 10% w v^-1) were fermented by Lactobacillus paracasei CBA L74 for 24 h. Then, pH, microbial growth and lactic acid production were assessed.

Results and conclusion: Rice fermentation was not affected by glucose addition. For oat and wheat, addition of D-glucose increased bacterial concentration, as well as lactic acid production. In particular, the best growth was achieved by the addition of 2 and 5% of glucose. Furthermore, lactic acid concentration increased with increased glucose concentration. In conclusion, D-glucose addition seems to be unnecessary for the improvement of rice fermentation. On the contrary, oat and wheat fermentations need further available carbon sources for a better Lactobacillus growth and a higher lactic acid production.

Conflict of interest: The authors declare no conflict of interest.

Background and objective: Fermented dairy products are considerably known due to several benefits including high nutritional values, immunity stimulations, antimicrobial and cancer suppressing effects. Kefir is a fermented dairy product with acidic-alcoholic flavors made from various sources of milk with various characteristics. The aim of this study was to investigate impact of soluble soybean polysaccharides on properties of kefir produced from cow and buffalo milk.

Materials and methods: Soluble soybean polysaccharides at concentrations of 0 (control), 0.5, 1 and 1.5% (w v^-1) were added to kefir samples produced from cow and buffalo milks and the physicochemical, sensory and microbiological characteristics as well as fatty acid profile analysis of the kefir samples were compared during one month of cold storage.

Results and conclusion: Results showed that soluble soybean polysaccharides (P≤0.05) had significant effects on kefir properties. By increasing concentration of soluble soybean polysaccharides and storage time of the kefir, some properties including acidity, viscosity, sensory score and counts of the lactic acid bacteria and yeasts were increased. The fatty acid analysis revealed that unsaturated fatty acids of cow and buffalo kefirs were more than cow and buffalo milks while these were reverse for saturated fatty acids. The best microbial and sensory properties of kefir were observed by adding 0.5 to 2% (w v^-1) soluble soybean polysaccharides on day 30 of storage.

Conflict of interest: The authors declare no conflict of interest.

Background and objective: L-Sorbose, as a precursor of ascorbic acid, can be biologically produced using Gluconobacter oxydans. The aim of this study was to optimize production of L-Sorbose by controlling concentration of the substrates and starter cultures.

Material and methods: In this study, effects of three various fermentation parameters on the concentration of L-sorbose were assessed using fermenter (28°C, 1.4 vvm) and response surface methodology. These parameters included quantities of D-sorbitol (120-180 g l_Dw^-1) (Deionized water) and yeast extract (6-18 g l_Dw^-1) and inoculum/substrate ratios (5-10%).

Results and conclusion: Results showed that the fitted model with high values of R² (0.9594) and R²-adjusted (0.9228) could effectively predict the concentration of L-sorbose within the highlighted ranges for the variables. Furthermore, results demonstrated that the maximum concentration of L-sorbose was achieved at 42.26 g l_DW^-1 using D-sorbitol, yeast extract and inoculum/substrate ratio values of 153.42 g l_DW^-1, 12.64 g l_DW^-1 and 9.88%, respectively. These results have revealed appropriately of response surface methodology for the prediction of L-sorbose product quantity and optimization of the variables in this aerobic fermentation process.

Conflict of interest: The authors confirm that they have no conflict of interest.

Background and objective: Phytate is an anti-nutritional agent in cereal foods, making nutritional and health problems in human. The gene responsible for the degradation of phytate has been identified in many bacterial species but not in lactic acid bacteria. The objective of this study was to isolate and characterize phy gene in lactic acid bacteria isolated from Ogi and Kunun-zaki.

Materials and methods: Lactic acid bacteria from Ogi and Kunun-zaki were phenotypically screened for phytase production. The phytate-degrading lactic acid bacteria isolates were identified using 16S rRNA gene sequencing. Amplification of phytase (phy) gene was carried out using polymerase chain reaction. Furthermore, phylogenetic analyses were carried out. Soluble proteins of three selected isolates were extracted and analyzed using sodium dodecyl sulphate polyacrylamide agarose gel electrophoresis.

Results and conclusion: Totally, 16 isolates of phytate-degrading lactic acid bacteria were identified as Lactobacillus brevis, Lactobacillus plantarum subsp. plantarum, Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus paraplantarum. The phy gene with an amplicon size of 2.0 kb was amplified and sequenced. Sequence similarities between the phy genes of lactic acid bacteria and that of Bacillus in GenBank included 97-99% with a phylogenetic relationship of less than 40%. The SDS-PAGE electrophoresis analysis revealed a 50-kDa molecular weight of the phytase in the three isolates. This study has shown that phy gene of the lactic acid bacteria presents in fermented foods, suggesting its potential product use as starter to produce fermented foods with improved nutritional qualities.

Conflict of interest: The authors declare no conflict of interest.