Probiotics are live microorganisms that provide health benefits to the host when ingested in adequate amounts. The strains most frequently used as probiotics include lactic acid bacteria and bifidobacteria. Probiotics have demonstrated significant potential as therapeutic options for a variety of diseases, but the mechanisms responsible for these effects have not been fully elucidated yet. Several important mechanisms underlying the antagonistic effects of probiotics on various microorganisms include the following: modification of the gut microbiota, competitive adherence to the mucosa and epithelium, strengthening of the gut epithelial barrier and modulation of the immune system to convey an advantage to the host. Accumulating evidence demonstrates that probiotics communicate with the host by pattern recognition receptors, such as toll-like receptors and nucleotide-binding oligomerization domain-containing protein-like receptors, which modulate key signaling pathways, such as nuclear factor-ĸB and mitogen-activated protein kinase, to enhance or suppress activation and influence downstream pathways. This recognition is crucial for eliciting measured antimicrobial responses with minimal inflammatory tissue damage. A clear understanding of these mechanisms will allow for appropriate probiotic strain selection for specific applications and may uncover novel probiotic functions. The goal of this systematic review was to explore probiotic modes of action focusing on how gut microbes influence the host.

/pdf/probiotic-mechanisms-of-action-2jyemfk5rm.pdf

Probiotic Mechanisms of Action

Impact of sourdough on the texture of bread.

Rheology and the breadmaking process

https://sites.evergreen.edu/townhalls/wp-content/uploads/sites/28/2015/02/Food-Microbiology_Nutritional-Perspective.pdf

Sourdough and cereal fermentation in a nutritional perspective.

Improvement of the quality and shelf life of wheat bread by fermentation with the antifungal strain Lactobacillus plantarum FST 1.7

Investigations were made to test the effect of two different sourdough starter culture types on wheat dough and bread quality. Two single-strain starter cultures consisting of well-defined strains of lactic acid bacteria (Lactobacillus plantarum, L. brevis) and a traditional mixed-strain sourdough culture (containing L. crispatus, L. pontis, and Saccharomyces cerevisiae) were evaluated for their effects on the rheological characteristics of wheat dough using both fundamental rheological and standard baking tests. Two other doughs were also evaluated, one which was chemically acidified to a comparable pH value by the addition of lactic acid, and a control which was not acidified. Dynamic oscillation tests were performed using a controlled stress rheometer. The phase angle and the absolute value of the complex dynamic modulus were measured for all doughs at frequencies of 0.1–10 Hz. The addition of sourdough prepared using single-strain or mixed-strain cultures significantly increased the phase ang...

Effect of single strain and traditional mixed strain starter cultures on rheological properties of wheat dough and on bread quality

Texture and crumb grain characteristics are two major quality attributes of bread products. Instrumental methods for measuring textural properties are widely used as tools for the objective measurement of texture properties. Digital image analysis is a relatively new, non-destructive technique that can be used for the evaluation of crumb grain structure. During this study the effects of sourdough on texture and crumb grain characteristics of wheat bread were determined; the effects of storage on these characteristics were measured and possible relationships between texture and structural characteristics were investigated. Sourdough wheat breads with 20 or 40% sourdough were produced according to a standard procedure. Bread with no added sourdough was used as a standard. Crumb texture profile analysis and crust penetration were performed 4, 26, 50 and 74 h after baking. The crumb grain characteristics of the breads were evaluated using an in-house digital image analysis system. Wheat bread with 20% sourdough showed reduced crumb firmness and slower firming over time. Digital image analysis revealed increased crumb shrinkage in both sourdough breads. Possible relationships between crumb shrinkage and crumb firmness, chewiness and resilience were established.

The effect of storage time on textural and crumb grain characteristics of sourdough wheat bread

The fundamental rheological characteristics of a biologically acidified, a chemically acidified, and a neutral preferment (sourdough) were monitored over the course of a 24-hr fermentation period using a split-plot design. Three doughs were subsequently prepared in which 20% of the flour was in the form of the respective preferment. A control dough containing no fermented material was also prepared. The fundamental rheological properties of both the dough and its isolated wet gluten were determined. Laser-scanning confocal microscopy was used to capture images of selected preferments and doughs. Results from the preferment showed that there was a decrease in elasticity (phase angle data from oscillatory measurements and relative recovery values from creep tests) and viscosity with fermentation time for all three preferments, all of which reached similar end values for these parameters. The microscopy images illustrated that the gluten strands were dissolved to a more amorphous structure during th...

Wheat sourdough fermentation: effects of time and acidification on fundamental rheological properties

Publisher Summary This chapter reviews the application of sourdough technology to wheat breads. The use of the sourdough process as a form of leavening is one of the oldest biotechnological processes in food production. To facilitate continuous production, a portion of ripe sourdough dough can be saved to seed subsequent doughs. In addition to the yeasts naturally present on the cereal grains, brewers' yeast is added to enhance the fermentation process, but the sourdough procedure predominated in bread making until specially prepared baker's yeast became available. Sourdough is dough made of cereal products, liquids, and microorganisms in an active state. Acidification (fermentation) produced by these substances is a continuous process. The activity of the microorganisms is never interrupted. There is considerable consensus regarding the positive effects conferred on bread products by the use of sourdough. The use of sourdough confers a natural image on the product. Lactic acid bacteria have a long history of use in food and are regarded as safe organisms. The rheology of wheat doughs and the resulting loaf volume are determined by gluten proteins, any changes associated with proteolytic degradation during sourdough fermentation will have an impact on the nature of the bread dough when pre-fermented material is incorporated.

Charmaine I. Clarke

Papers

Improvement of the quality and shelf life of wheat bread by fermentation with the antifungal strain Lactobacillus plantarum FST 1.7

Effect of single strain and traditional mixed strain starter cultures on rheological properties of wheat dough and on bread quality

The effect of storage time on textural and crumb grain characteristics of sourdough wheat bread

Wheat sourdough fermentation: effects of time and acidification on fundamental rheological properties

A review of the application of sourdough technology to wheat breads.