Interrelations of α‐ and β‐amylase activity with starch, sugars, and culinary and nutritional quality attributes in sweetpotato storage roots

BACKGROUND Little information is available on α‐ and β‐amylase activity and their associations with starch, sugars and other culinary qualities in sweetpotato. The present study aimed to assess sweetpotato storage root α‐ and β‐amylase activity in relation to starch, sugars, β‐carotene content and storage root flesh color. RESULTS α‐ and β‐amylase activity (α‐AA and β‐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 α‐AA and β‐AA, respectively. Storage root dry matter, starch, glucose, fructose, sucrose and β‐carotene content were predicted using near infrared reflectance spectroscopy. There was little relationship (r2 = 0.02–0.08, P ≤ 0.05 in 2016 and r2 = 0.05–0.11, P ≤ 0.05 in 2017) between α‐AA and β‐AA. We observed negative linear associations between α‐AA and dry matter content and generally no correlations between β‐AA and dry matter content. β‐AA and sugars were weakly positively correlated. β‐AA and β‐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 α‐ and β‐amylase activity are inter‐associated with several culinary quality attributes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.