Biological and Agricultural Engineering

BAE Exit Seminar: Mass Transport and Structural Changes of Sweet Potatoes during in Vitro Gastric Digestion as Influenced by Cooking Method

Wednesday, November 25, 2015
2:10 PM

2045 Bainer Hall

Mass Transport and Structural Changes of Sweet Potatoes during in Vitro Gastric Digestion as Influenced by Cooking Method

Yamile Mennah Govela, M.S. Candidate, Biological Systems Engineering

Knowledge of mass transport processes during digestion is important to understand the mechanisms of food digestion, but there is limited knowledge of this subject in the literature. Acid and enzymes penetrating into the ingested food from gastrointestinal secretions may cause structural modifications in the food matrix. The objectives of this study were to estimate the effective diffusivity of acid and water through sweet potatoes of varying cooking treatments, determine the influence of cooking on the mass transport processes, and elucidate the structural changes that occur as a result of these mass transport processes during simulated gastric digestion of sweet potatoes. Two studies were conducted using sweet potatoes as a test food. In the first study, sweet potatoes were cooked in four different ways (boiled, steamed, microwave steamed, and fried), and in the second study, sweet potatoes were boiled and steamed for different times resulting in mild or severe heat treatments. Sweet potatoes were cut into cubes, cooked, and were subjected to simulated oral and gastric digestion. Sweet potato cubes were removed from simulated gastric fluids at different time points to be analyzed. Acidity and moisture content were measured, and effective diffusivity was modeled using the experimental acidity and moisture content values. Hardness was measured by single compression of the cubes using a Texture Analyzer. Microstructure was examined via light microscopy before and after 240 min of digestion. In both studies it was found that the effective diffusivity of gastric acid into sweet potato matrices was different than water, and that mass transport was significantly influenced by both cooking method and cooking severity. Textural softening was observed after 240 min of digestion in both studies. Cell wall disruption and starch degradation was observed in boiled, steamed, and microwave steamed samples as a result of cooking and/or digestion. Fried sweet potatoes did not show cell wall breakdown, possibly due to the oil content in the sample. In study two, both boiled and steamed, mildly cooked sweet potatoes showed relatively uniform cell shapes before in vitro digestion.  Overall, it was observed that the cooking method and severity influences how the acid and moisture reacts with the food structure, resulting in structural changes in the sweet potato matrix.  Knowledge of the structural changes in sweet potatoes due to enzymatic and acid hydrolysis during simulated digestion is important to help understand the mechanisms of the food breakdown during digestion. Food breakdown will ultimately influence nutrient release and absorption. In order to optimize food nutritional properties, the relationship between food processing/cooking and food breakdown must be understood

2045 Bainer Hall University of California Davis

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