Degree

Candidate in Philosophy

Department

School of Nutrition and Food Science

Document Type

Dissertation

Abstract

Cocoa powder contains polyphenolic compounds, which can provide potential health benefits to humans. The human gastroinestinal tract hosts diverse microorganisms which are called the human gut microbiota. These microbes can utilize carbohydrates through fermentation resulting in the production of short chain fatty acids (SCFAs), which cause a reduction of pH in gastroinestinal tract. The cocoa processing can change the composition of the carbohydrates, which can affect the fermentation patterns.

In this study we established an in vitro model system which simulated gastric digestion and colon fermentation. Five different processed cocoa samples (alkalized cocoa samples: D-11-B and D-11-S; non-alkalized cocoa samples: natural cocoa, Lavado, shell) were digested, then they were fermented by the colonic bacteria from mixed pool fecal slurry under anaerobic conditions. The pH, SCFAs, procyanidin distribution, and polyphenolic compounds were measured. Then the Lavado was fermented with fecal slurries from six individuals. Changes in the pH, polyphenolic compounds, and SCFAs were determined.

The results of cocoa samples fermented with pooled fecal slurry demonstrated that pH of five cocoa samples significantly decreased after 24h of fermentation; meanwhile SCFAs concentration increased. Fermentation of the shell sample resulted in the highest production of SCFAs and the greatest reduction in pH. Polyphenolic compounds release was expressed both as gallic acid equivalent (GAE) and catechin equivalent (CE). Increases in both values were observed in all cocoa samples. The final GAE of alkalized cocoa samples were higher than non-alkalized cocoa samples; while final CE of the shell sample was the highest among five cocoa samples. The pH and SCFAs results indicated that cocoa samples can be fermented by gut microbiota. The polyphenolic compounds results showed that polyphenol content of cocoa powder increased during fermentation.

The pH decrease, polyphenols increase, and SCFAs increase were observed in individual fecal fermentation groups. However, the change patterns of pH, polyphenols, and SCFAs in each treatment group were different. The cocoa fermentation by colonic bacteria led to an increase of phenolic compounds. The variations of human gut microbiota among individuals affected fermentation pattern, subsequently affected pH change pattern and polyphenols profile during fermentation.

Date

1-16-2018

Committee Chair

Finley, John

Included in

Food Science Commons

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