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United States Department of Agriculture

Agricultural Research Service


Location: Food Science Research

Title: Susceptibility of sweetpotato (Ipomoea batatas) peel proteins to digestive enzymes

item Maloney, Katherine
item Truong, Van-den
item Allen, Jonathan

Submitted to: Food Science and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2014
Publication Date: 7/1/2014
Publication URL:
Citation: Maloney, K.P., Truong, V., Allen, J.C. 2014. Susceptibility of sweetpotato (Ipomoea batatas) peel proteins to digestive enzymes. Food Science and Nutrition. 2(4):351–360. doi: 10.1002/fsn3.110.

Interpretive Summary: Sweetpotato proteins have inhibitory effects on digestive enzymes such as trypsin and amylase. These inhibitors have shown to respectively possess antioxidant capacity and anti-diabetic activities. This study aimed to determine if these properties are retained after digestion in order to better understand how sweetpotato proteins could have those beneficial effects in the body. The isolated proteins were incubated with gastric enzymes and the protein breakdown was characterized. The results show that trypsin inhibitory activity remained after simulated gastric digestion. However, amylase inhibitory activity was not present in any of the protein isolates after digestion indicating that amylase inhibition was not the mechanism associated with the low glycemic response in consuming sweetpotatoes. Further study is required to provide a better understanding on the anti-diabetic activity of sweetpotato proteins.

Technical Abstract: Sweet potato proteins have been shown to possess antioxidant and antidiabetic properties in vivo. The ability of a protein to exhibit systemic effects is somewhat unusual as proteins are typically susceptible to digestive enzymes. This study was undertaken to better understand how digestive enzymes affect sweet potato proteins. Two fractions of industrially processed sweet potato peel, containing 6.8% and 8.5% protein and 80.5% and 83.3% carbohydrate, were used as a source of protein. Sweet potato proteins were incubated with pepsin, trypsin, and chymotrypsin and protein breakdown was visualized with SDS-PAGE. After pepsin digestion, samples were assayed for amylase inhibitory activity. Sporamin, the major storage protein in sweet potatoes, which functions as a trypsin inhibitor as well, exhibited resistance to pepsin, trypsin, and chymotrypsin. Sporamin from blanched peel of orange sweet potatoes was less resistant to pepsin digestion than sporamin from outer peel and from extract of the white-skinned Caiapo sweet potato. Trypsin inhibitory activity remained after simulated gastric digestion, with the Caiapo potato protein and peel samples exhibiting higher inhibitory activity compared to the blanched peel sample. Amylase and chymotrypsin inhibitory activity was not present in any of the samples after digestion.

Last Modified: 06/28/2017
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