Sourdough Chemistry

Sourdough Chemistry

Slower spoiling of bread

• Sourdough releases lactic acid, acetic acid and other compounds into the air, even after its baked.

• The organic compounds release from and contained in sourdough prevent the bread from spoiling as quickly as regularly risen yeast bread .

Nutritional benefits of sourdough

• This means a longer preservation of the bread's flavor and texture, it wont go stale as quickly ( Plessas 630)

• Because the human digestive tract cannot process phytic acid, it traps many of the trace elements in plant based foods like iron and zinc.

• Sourdough fermentation and breaks these minerals free.

• The fermentation increases the bioavailability of minerals and nutrients in the flour used for the bread (Lopez 524) .

• The glycemic response in the body is lower because of higher resistant starch levels found in sourdough that slow the distribution of the sugar from the starches in in the bread (Scazzina 419)

Yeast's sugar metabolism

Conclusion

• Yeast cannot easily metabolize fructose and usually leaves it behind (Schuster) Which the LAB then will consume (Vrancken 60).

• The unique flavor is a result of lactic acid and other organic compounds produced by the fermentation (Arendt 166).

• Fermentation involves a lactic acid bacteria and a low pH tolerant yeast (Carnevali 151).

• Both organisms use different sugars at different points of the development of the sourdough (Vrancken 60), but, usally avoid using the same sugar for a food source at the same time.

• As the pH decreases the yeast will start to find more maltose left by the LAB to consume (Vrancken 60).

• The organic compounds produced also extend the time that the flavor and texture of the bread lasts without going stale (Plessas 360).

"(Glucose)"

• The fermentation process also breaks down phytic acid allowing greater bioavailability of otherwise unavailable nutrients like Iron, Zinc, and Copper (Lopez 524).

• Sourdough also has a lower glycemic impact (Scazzina 419)

(Schuster)

Work Cited

How does it rise?

Sourdough

• Similar to yeast-only process

• Arendt., Elke K., Ryan, Liam A.M., Dal Bello, Fabio.” Impact of sourdough on the texture of bread” Food Microbiology. Volume 24. Issue 2(2007):165-174. ScienceDirect.Web. 2 Oct. 2014

• Carnevali, P., et al. “ Liquid sourdough fermentation: Industrial application prospectives.” Food Microbiology. Volume 24. Issue 2 (2007): 150-154. ScienceDirect. Web. 2 Oct. 2014

• Lopez, Hubert W., et al.” Making bread with sourdough improves mineral bioavailability from reconstituted whole wheat flour in rats.” Nutrition. Volume 19.issue 6 (2003): 524-530. ScienceDirect.Web. 2 Oct. 2014

• Plessas, Stavros., et al. “Examination of freshness degradation of sourdough bread made with kefir through monitoring the aroma volatile composition during storage” Food Chemistry. Volume 124. Issue 2 (2011): 627-633. ScienceDirect.Web. 2 Oct. 2014

• Scazzina, Francesca., et al. “Sourdough bread: Starch digestibility and postprandial glycemic response” Journal of Cereal Science. Volume 49. Issue 3(2009): 419-421. ScienceDirect.Web. 2 Oct. 2014

• Schuster, Tom,Van Zyl, Rosalie, Coller, Harold. “Effect of different Isomers of sugar on Yeast Respiration” Longitudinal Studies. N.p. 2005. Web. 31 Oct. 2014

• Vrancken,G.,Rimaux,T., De Vuyst, L., Leroy, F. “Kinetic analysis of growth and sugar consumption by Lactobacillus fermentum IMDO 130101 reveals adaptation to the acidic sourdough ecosystem.” International Journal of Food Microbiology. Volume 128. Issue 1 (2008):58-66. ScienceDirect.Web. 2 Oct. 2014

• The yeast and LAB produce biproducts including CO2, mannitol, lactic acid and acetic acid (Vrancken 60).

(Prezi)

• The bread rises mainly because of the yeast (Arendt 166).

How they work together (Continued)

• Yeast won't metabolize the starch whole instead the LAB breaks it down to simpler parts

How they work together

• Nutritional media is plant based (flour)

• Contains starches and proteins

• While the LAB is consuming the its prefered sugars, the yeast starts consuming sucrose and any of the, maltose, sucrose or glucose it can find (Schuster).

• The LAB consumes the available sugars: Maltose, Fructose, and Glucose but cannot metabolize Sucrose (Plessas 630).

• As the pH approaches 3.5 the LAB stops consuming maltose and glucose almost entirely (Vrancken 60)

What is Sourdough?

• A bread with a distinct sour flavor mostly due to lactic acid.

• One of the oldest types of bread

• Cultured from the microorganisms in fresh air

• Rises very slowly (Arendt 166).

Bacteria

Lactobacilli Sanfransicensis

• Lactic acid bacteria (LAB)

• Most common strain in sourdough

• Consumes parts of the starches and proteins (Carnevaeli 151)

• Also found in dairy products like kefir

Why is it different?

• Can aid digestion of dairy products and other foods (Plessas 630)

• Usually traditional breads are risen by yeast alone

• Sourdough is not just yeast fermentation

• A fermentation between two organisms typically: (Lopez 524).

• A yeast Candida Milleri

Yeast

• A bacteria Lactobacilli Sanfransicensis (Carnevali 151).

Candida Milleri

• Consumes sugars

• Produces CO2

• Cannot consume more complex molecules like starches (Schuster)

• This species can withstand low pH (Carnevali 151)