Amylase and invertase activity and substrate affinity in 'Danshaku' potato tubers (Solanum tuberosum L.) during cold storage

Activity of α-amylase, β-amylase, and invertase was observed during storage of 'Danshaku' potato tubers at 0°C and 10°C for evidence of association with sugar accumulation at low temperature. Significant sugar accumulation was observed in tubers stored at 0°C; minimal accumulation was observed in tubers stored at 10°C. No differences were observed in a-amylase activity between treatments during storage. β-amylase activity during 0°C storage was twice the activity at 10°C after 60 days in storage, while invertase activity after storage was three times higher in tubers stored at 0°C compared to 10°C. A positive (r>0.729) but nonsignificant (p > 0.05) correlation was observed between invertase activity at 0°C and sugar levels. No significant relationship was observed for α-amylase activity and sugar levels in tubers stored at 0°C. β-amylase activity at 0°C was positively (r > 0.994) and significantly (p < 0.05) correlated with sugar levels. In tubers stored at 10°C, enzyme activity was generally not correlated with sugar levels. Based on activity during cold storage, β-amylase and invertase could contribute to LTS in 'Danshaku' potato tubers by breaking down starch and hydrolyzing sucrose into reducing sugars, respectively.