Zoe Bumanis | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Zoe Bumanis. This seminar is open to the general public to attend.

MSc with Dr. Michael Gaenzle

Thesis Topic: The Impact of Different Fermentations on the Antifungal Activity of Sourdough Bread

Abstract:

Sourdough is often used in bread production to improve flavor, texture, and to provide leavening. However, bread’s shelf life is limited by its neutral pH and high water activity, both of which make it vulnerable to spoilage by fungi like Penicillium spp. This is a problem which costs the commercial baking industry millions each year and contributes significantly to global food waste. Common methods of chemical preservation like calcium propionate and sorbic acid are falling out of favor with ingredient-conscious consumers, leaving a hole in the market for a preservative-free or reduced-preservative sourdough bread.

In this work the antifungal impact of 12 strains of lactobacilli incorporated into 10% sourdough breads were compared to one another and revealed to be largely equivalent when inoculated with the highly-resistant spoilage organism Penicillium roqueforti. However, altered fermentation and proofing protocols resulted in an increase in shelf life which matched that of bread containing 0.3% calcium propionate, even in a ‘worst-case’ exposure scenario. It was also determined that a combination of 0.1% calcium propionate and sourdough was similarly effective in delaying fungal spoilage. The inclusion of buckwheat in sourdough fermentations and the subsequent impact on shelf life was also recorded for the first time, while the benefits of isomerized ɑ-acids sourced from hops were further supported by the findings of this study.

This research posits that a three-pronged approach utilizing the products of sourdough fermentation, antifungal adjuncts, and a clean processing area can not only reduce instances of fungal contamination but also lead to improved resistance and extended shelf life when contamination does occur in preservative-free or reduced-preservative bread, providing a benefit that cannot be achieved by any one of these factors alone.