Defined co-cultures of yeast and bacteria modify the aroma, crumb and sensory properties of bread.

Yeast and bacterial communities inhabit a sourdough starter to make artisanal bread. This study shows whether the interactions of micro-organisms derived from Australian sourdough starters provide some of the positive flavour, and aroma properties to bread by using defined sourdough cultures as the sole leaven in bread production. An investigation of Australian sourdough starters found that they contained Saccharomyces cerevisiae and Kazachstania exigua yeasts. When these yeasts were inoculated alone to ferment wheat flour in an extended fermentation, the bread had a heterogeneous crumb structure, a deeper colour and a distinctive chemical aroma profile than those made with commercial baker's yeast. When bread was made combining these yeasts individually and in combinations with lactic acid bacteria also isolated from these sourdough starters, including Lactobacillus plantarum, L. brevis, L. rossiae, L. casei, the bread aroma profiles and crumb structure were more distinctive, with compounds associated with sour aromas produced, and preferred by sensory panels. The use of defined mixed cultures as the leaven in bread making, by exploiting the microbial diversity of artisanal Australian starters, can produce bread with distinctive and attractive aromas. Understanding and identifying the community ecosystems found in sourdough cultures and using them as the sole leaven in bread production provide novel insights into microbial interactions and how they affect food quality by removing the effects of commercial yeast strains.

Winters M ，Panayotides D ，Bayrak M ，Rémont G ，Viejo CG ，Liu D ，Le B ，Liu Y ，Luo J ，Zhang P ，Howell K ... -  《-》

Pro-technological and functional characterization of lactic acid bacteria to be used as starters for hemp (Cannabis sativa L.) sourdough fermentation and wheat bread fortification.

Lactic acid bacteria were isolated from hemp (Cannabis sativa L.) flour, spontaneously fermented dough, and type I sourdough. Isolates were identified and further selected based on pro-technological, nutritional and functional properties. Lactobacillus plantarum/s5, Pediococcus acidilactici/s5, and Leuconostoc mesenteroides/s1 were used as mixed starter to produce hemp sourdough. Significant decreases of the concentration of phytic acid, condensed tannins, and total saponins were observed during fermentation. The in vitro protein digestibility increased up to 90%. Experimental wheat breads were made adding 5% to 15% (w/w) hemp sourdough to the formula, characterized, and compared to baker's yeast wheat bread manufactured without hemp sourdough. The use of hemp sourdough improved the textural features of wheat bread, without adversely affect the sensory profile. Proportionally to the fortification with hemp sourdough, protein digestibility of the breads increased, while the predicted glycemic index significantly decreased (87 vs 100%). This work demonstrated that the fermentation with selected starters improved nutritional functionality of hemp flour, allowing its large-scale use in different food applications, meeting the consumers and producers request for novel fermented baked goods with a well-balanced nutritional profile.

Nionelli L ，Montemurro M ，Pontonio E ，Verni M ，Gobbetti M ，Rizzello CG ... -  《-》

Identification of lactic acid bacteria and yeasts, and characterization of food components of sourdoughs used in Japanese bakeries.

Sourdough is a low-pH, fermented product prepared using lactic acid bacteria and yeast mixed with rye flour, wheat flour, and water. It is used and backslopped in bakeries because it enhances texture, flavor, and dough expansion of bread. Various lactic acid bacteria and yeasts have been identified in sourdough, especially in the West. However, microbial and physical characteristics of sourdough from Japan have not been investigated. Here, we characterized the microbial composition and food component characteristics of sourdough from four bakeries in Kansai region, Japan, and performed sensory and quality evaluation of baguettes enriched with 10% sourdough. We detected different species of lactic acid bacteria such as Lactobacillus brevis, Lactobacillus alimentarius, Lactobacillus pentosus, Lactobacillus vaccinostercus, Lactobacillus sanfranciscensis, and Lactobacillus sakei. The identified yeasts primarily included Saccharomyces cerevisiae, with Candida humilis detected in some samples. Components such as amino acids, lactic acid, acetic acid, ethanol, 3-methyl-1-butanol, ethyl acetate, and phenethyl alcohol differed among samples and distinctively affected flavor, quality, and aroma of sourdough-enriched baguettes. The different species of lactic acid bacteria and the ratio of lactic acid bacteria to yeasts possibly affected food components such as free amino acids, sugars, and organic acids via the Maillard reaction, which influences the savory aromas of bread. Future investigation of the effect of lactic acid bacteria will help to improve the overall quality of bread.

Fujimoto A ，Ito K ，Narushima N ，Miyamoto T ... -  《-》

Sourdough starter culture microbiomes influence physical and chemical properties of wheat bread.

Sourdough fermentation is an ancient leavening method that uses wild yeasts to produce carbon dioxide, contributing to bread rise, and bacteria which produce organic acids. Sourdough starter cultures are known to be diverse in terms of the microorganisms they comprise and while specific genera and species of microorganisms have been identified from starters and associated with specific attributes, overarching relationships between sourdough starter culture microbiomes and bread quality are not well understood. The objective of this study was to characterize differences in the physical and chemical properties of breads produced with sourdough starter cultures with unique microbiomes. Sourdough starter cultures (n = 20) of known microbial populations were used to produce wheat-based dough and bread, which were analyzed for chemical and physical properties then compared to their microbial populations in order to identify relationships between microbial profiles and dough/bread qualities. All samples were also compared to bread produced only with Saccharomyces cerevisiae (baker's yeast). Significant differences among pH, titratable acidity, loaf volume, crumb firmness, crust color, free amino acids, and organic acids were observed when comparing sourdough breads to the yeast-only control (p ≤ 0.05). Furthermore, bacterial diversity of sourdough starter cultures was correlated with lactic acid and free amino acid in the dough and loaf volume and crumb firmness of baked breads. No significant correlations were found between fungal diversity and measured outcomes. These data demonstrate the importance of considering sourdough starter microbiomes as an ingredient in baked goods and they contribute to quality and safety outcomes in bread production. PRACTICAL APPLICATION: Sourdough starter cultures have diverse and dynamic populations of bacteria and yeasts, which contribute to the production of bread products. These populations can influence the physical and chemical properties of sourdough fermentation and final breads. Understanding of the relationship between sourdough starter microbiomes and bread quality parameters can lead to targeted development of sourdough bread products with specific physical and chemical properties.

Clark CS ，Ohstrom A ，Rolon ML ，Smith M ，Wolfe BE ，Wee J ，Van Buiten CB ... -  《-》

The rise of the sourdough: Genome-scale metabolic modeling-based approach to design sourdough starter communities with tailored-made properties.

Sourdough starters harbor microbial consortia that benefit the final product's aroma and volume. The complex nature of these spontaneously developed communities raises challenges in predicting the fermentation phenotypes. Herein, we demonstrated for the first time in this field the potential of genome-scale metabolic modeling (GEMs) in the study of sourdough microbial communities. Broad in-silico modeling of microbial growth was applied on communities composed of yeast (Saccharomyces cerevisiae) and different Lactic Acid Bacteria (LAB) species, which mainly predominate in sourdough starters. Simulations of model-represented communities associated specific bacterial compositions with sourdough phenotypes. Based on ranking the phenotypic performances of different combinations, Pediococcus spp. - Lb. sakei group members were predicted to have an optimal effect considering the increase in S. cerevisiae growth abilities and overall CO2 secretion rates. Flux Balance Analysis (FBA) revealed mutual relationships between the Pediococcus spp. - Lb. sakei group members and S. cerevisiae through bidirectional nutrient dependencies, and further underlined that these bacteria compete with the yeast over nutrients to a lesser extent than the rest LAB species. Volatile compounds (VOCs) production was further modeled, identifying species-specific and community-related VOCs production profiles. The in-silico models' predictions were validated by experimentally building synthetic sourdough communities and assessing the fermentation phenotypes. The Pediococcus spp. - Lb. sakei group was indeed associated with increased yeast cell counts and fermentation rates, demonstrating a 25 % increase in the average leavening rates during the first 10 fermentation hours compared to communities with a lower representation of these group members. Overall, these results provide a possible novel strategy towards the de-novo design of sourdough starter communities with tailored-made characterizations, including a shortened leavening period.

Sabach O ，Buhnik-Rosenblau K ，Kesten I ，Freilich S ，Freilich S ，Kashi Y ... -  《-》