Use of gases to improve survival of Bifidobacterium bifidum by modifying redox potential in fermented milk

International audienceThe aim of this work was to study the effect of the oxidoreduction potential, modified using gas, on the growth and survival of a probiotic strain, Bifidobacterium bifidum, and 2 yogurt strains, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. Three fermented milks were manufactured with an initial oxidoreduction potential value adjusted to +440 mV (control milk), +350 mV (milk gassed with N2), and −300 mV [milk gassed with N2 plus 4% (vol/vol) H2 (N2-H2)]. Acidification profiles, growth during milk fermentation and survival during storage at 4°C for 28 d were determined. This study showed that fermented probiotic dairy products made from milk gassed with N2 and, more particularly, those made from milk gassed with N2H2 were characterized by a significant increase in B. bifidum survival during storage without affecting the fermentation kinetics and the survival of Strep. thermophilus and L. delbrueckii ssp. bulgaricus

A way to follow the viability of encapsulated Bifidobacterium bifidum subjected to a freeze-drying process in order to target the colon: Interest of flow cytometry

International audienceThe aim of this work was to apply flow cytometry in order to assess and compare the viability of freeze-dried entrapped bacteria with an usual technique by quantification by plate count techniques. It also aimed at studying the effect of various cryoprotectants on the viability of an entrapped Bifidobacterium bifidum subjected to freeze-drying to check their ability to be delivered all along the gastro-intestinal tract. The alginate–pectinate beads were chosen as the encapsulation matrix added with different protectants. The beads were characterized by scanning electron microscopy and the viability was checked by both methods. The best combination to improve viability of entrapped bacteria subjected to freeze-drying is made of glycerol 20% (one cryoprotectant) and sodium ascorbate 10% (one anti-oxidative compound). This study also demonstrates that flow cytometry allows assessment of entrapped bacteria viability. Indeed we showed that viability evaluated by plate method is correlated to that obtained by flow cytometry. So, flow cytometry is a rapid method to determine cell viability after encapsulation and freeze-drying. Finally, these beads seem to be a promising probiotic delivery system to target the colon

Green strategies to control redox potential in the fermented food industry

International audienceLactic acid bacteria (LAB) are important microorganisms in the food industry as functional starters for the manufacture of fermented food products and as probiotics. Redox potential (Eh) is a parameter of the physicochemical environment of foods that influences key oxidation-reduction reactions involved in process performances and product quality. Eh can be modified by different methods, using redox molecules, catalytic activity of enzymes or LAB themselves, technological treatments like electroreduction or heating, and finally gases. Nowadays new applications for food manufacture must undertake green process innovation. This paper presents the strategies for Eh modification in a sustainable manner for production of LAB biomass (starters, probiotics) and fermented food products (fermented milks, cheeses and others). While the use of chemical or enzymes may be subject to controversy, the use of gases offers new opportunities, in combination with LAB. Protection against food-borne microorganisms, an increasing growth and viability of LAB, and a positive impact on food flavour are expected