Food Science and Technology Department


First Advisor

Dr. Devin Rose

Date of this Version



Wensheng Ding, Devin Rose, 2023, Influence of overcooking on food digestibility and in vitro fermentation.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Food Science and Technology, Under the supervision of Professor Devin J. Rose. Lincoln, Nebraska: August 2023

Copyright © 2023 Wensheng Ding


Areas of char or overcooking commonly appear in foods people consume. It has been reported that overcooked food is harmful to human health. However, little research exists on the effect of overcooking on in vitro protein and starch digestibility and gut microbial fermentation. This study aimed to reveal the connection between overcooking and in vitro protein and starch digestibility and gut microbial fermentation. In vitro protein digestibility of an overcooked ground beef patty was almost half that of a standard cooked sample (27 ± 2% versus 48 ± 6%, respectively; p = 0.02). Whole wheat bread protein digestibility was also significantly diminished by overcooking (standard: 56 ± 3% versus overcooked: 43 ± 4%; p = 0.02), while starch digestibility was not influenced by overcooking (standard: 80 ± 1% versus overcooked: 76 ± 2%; p = 0.12). Overcooking decreased acetate, propionate, iso-butyrate, iso-valerate and ammonia production by the gut microbiota during fermentation of the beef sample, and decreased propionate and ammonia production during fermentation of the bread sample. Interestingly, overcooking enhanced butyrate production by the microbiota after 48h of fermentation of the bread sample (4.31 ± 1.26 versus 2.05 ± 0.69 respectively, p = 0.035), while no significant difference was found between overcooked and standard cooked beef samples (7.95 ± 1.34 versus 7.79 ± 1.13 respectively, p = 0.14). Overcooking resulted in reductions in many Pseudomonadota and favored several Bacillota, especially Ruminococcaceae, and Oscillospiraceae, which contain butyrate producers. Overall, overcooking had a strongly reduce in the digestibility and fermentation of proteins. Unexpectedly, overcooking induced several purportedly favorable effects on the gut microbiota due to the decreased protein fermentation, which, in future studies, should be weighed against the previous reports that overcooking is deleterious to human health.

Advisor: Devin J. Rose