Date of Award

12-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Food, Nutrition and Packaging Sciences

Committee Member

Paul Dawson

Committee Member

Michelle Parisi

Committee Member

Julie Northcutt

Abstract

Sourdough is the oldest form of leavening which many believe was invented by the Egyptians. Bread leavened with a sourdough culture relies on the metabolism of naturally occurring lactic acid bacteria and wild yeasts. Historically there were many ties between beer brewing and bread baking. In the fourteen and fifteen hundreds, it was discovered that brewers yeast could also be used to leaven bread. Up until the invention of commercial yeast in the nineteenth century, sourdough cultures and brewers yeast where the only bread leavening methods. By 1910, traditional sourdough was much less common because bread made with commercial yeast was much faster and easier, and produced a more consistent product. The positive qualities of sourdough bread were unfortunately overlooked because of the convenience that commercial yeast offered. Phytic acid makes up about 1% of wheat and rye flours, and reduces the bioavailability of calcium, magnesium, and iron by forming complexes with the divalent cations. Phytic acid also inhibits enzymes in the digestive system needed to breakdown starch and protein. This explains why some people experience discomfort from eating whole grain wheat products. Sourdough bacteria breakdown phytic acid and “predigest” the grain during the proofing process which releases easy to digest micronutrients. Specific sourdough lactic acid bacteria breaks down sucrose to form exopolysaccharides that contributes to bread volume, texture, and dietary fiber content. This increase in fiber slows the digestion of the sourdough bread and does not cause rapid blood sugar spikes like a commercial white bread often does. The objective of this study was to gain a better understanding of how fermentation time and temperature affect sourdough production and give insight to why it is sometimes more acceptable than non-fermented breads to the human digestive system. Three identical batches of sourdough bread, 9 samples per batch, were produced and analyzed. Samples 26-2, 26-4, 26-8, and 26-12 were fermented at 26°C and samples 4-14, 4-26, 4-38, and 4-50 were fermented at 4°C to observe the affect of temperature on fermentation. Bread samples were analyzed for moisture, loaf height, and protein content, and parallel dough samples where analyzed for volatiles. This experiment shows evidence of protein hydrolysis with data indicating an increase in alcohol extractable protein as fermentation time increases. It was observed that fermentation temperature, environment (presence or lack of O2), and time/duration all effect the bread qualities.

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