Sourdough bread cultures are mixtures of wild yeasts and Lactobacillus bacteria living in flour and water, where they form an interesting symbiosis that makes the culture quite stable. The presence of lactic acid bacteria (LAB) in sourdough bread cultures increases the shelf life of the sourdough bread and other sweet baked goods made with these cultures, due to the inhibitory effect of organic acids on spoilage molds. In addition, it has been found that when sourdough LAB are cultivated they produce antifungal substances, such as organic acids (in particular, lactic acid and acetic acid), carbon dioxide, ethanol, and hydrogen peroxide, and other, as yet unidentified inhibitory substances, that prevent mold growth. The inhibitory effect of four American sourdough cultures were tested for antifungal activity against the common spoilage molds, Aspergillus flavus, Aspergillus niger, Penicillium expansum, Penicullium roqueforti, and Cladosporium cladosporioides. In these experiments, actively growing sourdough cultures were inoculated into modified deMan Rogosa and Sharpe (mMRS) broth and incubated. After incubation, the cultures were centrifuged and filtered through 0.2µm membrane filters, the supernatants were collected and mixed with Potato Dextrose Agar (PDA). This mixture was used as culture medium for the growth of the spoilage molds. The growth rates of molds growing in the presence of the sourdough culture supernatants were compared with controls, where the molds were cultivated only in PDA. The results showed that Aspergillus flavus and Cladosporium cladosporioides were inhibited the most by the sourdough cultures. Therefore, the use of sourdough cultures shows promise for preserving food products from spoilage, as they could be a source of natural antimicrobial and antimycotic agents for use in the food industry.
Kam, Pei Ven; Bianchini, Andreia; and Bullerman, Lloyd B.
"Inhibition of Mold Growth by Sourdough Bread Cultures,"
RURALS: Review of Undergraduate Research in Agricultural and Life Sciences: Vol. 2
, Article 5.
Available at: http://digitalcommons.unl.edu/rurals/vol2/iss1/5