Interrelations of a- and ß-amylase activity with starch, sugars, and culinary and nutritional quality attributes in sweetpotato storage roots

Authors: AMANKWAAH, V.A. - North Carolina State University; WILLIAMSON, S. - North Carolina State University; OLUKOLU, B. - University Of Tennessee; TRUONG, VAN DEN - Retired ARS Employee; CAREY, E. - International Potato Center; SSALI, R. - International Potato Center; YENCHO, G. CRAIG - North Carolina State University

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2023
Publication Date: 6/1/2024
Citation: Amankwaah, V., Williamson, S., Olukolu, B., Truong, V.-D., Carey, E., Ssali, R., Yencho, G. 2024. Interrelations of a- and ß-amylase activity with starch, sugars, and culinary and nutritional quality attributes in sweetpotato storage roots. Journal of the Science of Food and Agriculture. 104(8):4662-4670. https://doi.org/10.1002/jsfa.12832.
DOI: https://doi.org/10.1002/jsfa.12832

Interpretive Summary: This study aimed to support the sweetpotato breeding programs by providing the information on a- and ß-amylase activity (a-AA and ß-AA, respectively) and how these enzymes relate to nutritional and culinary quality attributes in sweetpotatoes. Sweetpotato roots of a Tanzania x Beauregard genetic mapping population were harvested, cured and stored for about 11 weeks. Samples were analyzed for amylase activity, dry matter, starch, sugar, ß-carotene and culinary quality attributes. The results showed negative linear associations between a-AA and dry matter content and no correlations between ß-AA and dry matter content. However, ß-AA were weakly positively correlated with sugars and positively correlated with ß-carotene content. The correlation coefficient for amylase enzyme activity and sugar components of storage roots at harvest increased after curing and during post-harvest storage. This study is a major step forward in sweetpotato breeding by providing a better understanding on the inter-association of amylase activity in sweetpotato genotypes with culinary quality attributes leading to development of new varieties with improved culinary and/or industrial characteristics.

Technical Abstract: BACKGROUND Little information is available on a- and ß-amylase activity and their associations with starch, sugars and other culinary qualities in sweetpotato. The present study aimed to assess sweetpotato storage root a- and ß-amylase activity in relation to starch, sugars, ß-carotene content and storage root flesh color. RESULTS a- and ß-amylase activity (a-AA and ß-AA) were assayed from a Tanzania (T) × Beauregard (B) genetic mapping population in their uncured (raw), cured and stored (approximately 11'weeks) forms during 2016 and 2017. Ceralpha and Betamyl methods, with modifications to suit a high-throughput microplate assay format, were used to quantify a-AA and ß-AA, respectively. Storage root dry matter, starch, glucose, fructose, sucrose and ß-carotene content were predicted using near infrared reflectance spectroscopy. There was little relationship (r^2 = 0.02–0.08, P = 0.05 in 2016 and r^2 = 0.05–0.11, P = 0.05 in 2017) between a-AA and ß-AA. We observed negative linear associations between a-AA and dry matter content and generally no correlations between ß-AA and dry matter content. ß-AA and sugars were weakly positively correlated. ß-AA and ß-carotene content were positively correlated (r = 0.3–0.4 in 2016 and 0.3–0.5 in 2017). CONCLUSION Generally, the correlation coefficient for amylase enzyme activity and sugar components of storage roots at harvest increased after curing and during post-harvest storage. The present study is a major step forward in sweetpotato breeding in terms of providing a better understanding of how a- and ß-amylase activity are inter-associated with several culinary quality attributes.