Changes in sorghum starch digestibility, phytochemical composition, and cell bioactivity of sorghum flour during heat and high moisture pH treatments

Authors: Smolensky, Dmitriy; Peterson, Jaymi; SANTANA, ADINA - Kansas State University; PERUMAL, RAMASAMY - Kansas State University; Bean, Scott; Wu, Xiaorong; WANG, WEIGUN (GEORGE) - Kansas State University; Perez-Fajardo, Mayra; COX, SARAH - US Department Of Agriculture (USDA); COVARRUBIAS, JOSE - US Department Of Agriculture (USDA)

Submitted to: Frontiers in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2024
Publication Date: 8/8/2024
Citation: Smolensky, D., Peterson, J.M., Santana, A., Perumal, R., Bean, S.R., Wu, X., Wang, W., Perez-Fajardo, M.A., Cox, S., Covarrubias, J. 2024. Changes in sorghum starch digestibility, phytochemical composition, and cell bioactivity of sorghum flour during heat and high moisture pH treatments. Frontiers in Nutrition. 11. Article 1428542. https://doi.org/10.3389/fnut.2024.1428542.
DOI: https://doi.org/10.3389/fnut.2024.1428542

Interpretive Summary: Sorghum has a high degree of genetic diversity with some varieties containing health promoting compounds called polyphenols. Sorghum phenolics have shown anticancer properties in laboratory studies. However, the presence of polyphenols may decrease nutritional factors like digestible starch. The objective of this study was to determine the effects of pH and high moisture cooking on starch digestibility, phenolic profile, and anticancer activity in sorghum. Sorghum was combined with buffer solutions (pH 3, 4, 5, 7, and 8) and cooked for 0, 10, 30, 60, or 120 mins. Starch digestibility was determined and changes in phenolic composition were measured. Total starch digestibility of samples significantly increased after heating. Overall, heating samples for 10 mins did not significantly reduce TPC of samples. Heating time decreased total polyphenols and their bioactivity. Heating samples for 10 minutes had minimal effects on anticancer activity while longer heating times reduced the anticancer activity of the extracts. Higher pH levels significantly decreased anticancer activity independent of heating time. Heating sorghum for 10 mins improved starch digestibility with minimal negative effects on the potential health benefits. This shows potential for high polyphenol containing sorghum varieties to be used for functional food formulations.

Technical Abstract: Sorghum has a high degree of genetic diversity with some varieties containing health promoting compounds called polyphenols. Sorghum phenolics have shown anticancer properties in laboratory studies. However, the presence of polyphenols may decrease nutritional factors like digestible starch. The objective of this study was to determine the effects of pH and high moisture cooking on starch digestibility, phenolic profile, and anticancer activity in sorghum. Sorghum was combined with buffer solutions (pH 3, 4, 5, 7, and 8) and cooked for 0, 10, 30, 60, or 120 mins. Starch digestibility was determined using the K-DSTRS kit from Megazyme. Changes in phenolic composition were measured using total polyphenol (TPC) and condensed tannin content (CTC) assays coupled with reversed phase high performance liquid chromatography (RP-HPLC) analysis. Anticancer potential against human colorectal cancer (HCT116 and SW480) cells were determined using cell viability assay. Total starch digestibility of samples significantly increased (p<0.0001) after heating. Overall, heating samples for 10 mins did not significantly reduce TPC of samples. Heat time significantly (p<0.05) decreased CTC while pH did not significantly affect CTC. All measured 3-deoxyanthocyanidins saw a significant (p<0.0001) decrease while some flavonoids increased significantly (p<0.05) after heating for 30 mins or longer. Heating samples for 10 minutes had minimal effects on anticancer activity while longer heat times reduced the anticancer activity of the extracts. Higher pH levels significantly decreased anticancer activity independent of heating time. Heating sorghum for 10 mins improved starch digestibility with minimal negative effects on the potential health benefits. This shows potential for high polyphenol containing sorghum varieties to be used for functional food formulations.