Masters Theses

Date of Award

12-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

Marjorie Penfield

Committee Members

David Golden, John Mount

Abstract

While interest in and consumption of sourdough bread has increased in the United States, research on sourdough starters and bread in this country has not kept pace. The objective of this study was to evaluate the effects of storage temperature (4°C or 30°C) and starter age (over 38 days) on properties of sourdough starter, dough and bread. The starters (S4, S30) and dough (D4, D30) were evaluated for pH, acid value (AV) and populations of lactic acid bacteria (LAB) and yeast. Bread was baked on Days 8, 22 and 36 (Weeks 1, 3 and 5, respectively). Bread (B4, B30) was evaluated using sensory evaluation, as well as instrumental texture profile analysis (TPA), index to volume, moisture, pH and AV. No differences were found between starters for pH, AV or LAB population: however, the pH decreased and the AV increased from Day 0 to 1 to 7. Neither pH nor AV differed between D4 and D30 or due to starter age. The LAB population did not differ between starters. The LAB population of the starters reached log 8.6 CFU/g by Day 7; this level did not differ from the LAB content of the starters on subsequent days throughout the 5 weeks. There were no differences in LAB populations between doughs or across weeks. As for yeast, differences were found between starters; S30 had a higher yeast population than S4 on corresponding days from Day 21 to 36 (Weeks 3 to 5). Similarly, D30 had a higher yeast population at Weeks 3 and 5 than for D30 at Week 1 and for all weeks of D4. For pH and AV, B4 and B30 did not differ from each other or due to starter age. While there were no differences between breads (B4 and B30) for index to volume, the index to volume of the bread at Week 5 was higher than at Week 1. Overall, sensory evaluation indicated few differences; both B4 and B30 were rated to be less moist and have less fresh aroma than the "ideal" sourdough bread. There were no differences between B4 and B30 for instrumental texture profile analysis; however, springiness increased and gumminess decreased between Weeks 1 and 5. While not statistically significant, a trend was seen of higher index to volume and less hardness (instrumental TPA) across weeks in B30 versus B4. This is noted because such a trend may be important in consumer acceptance of the product.

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