Biochemical changes and inhibition of sprouting by light quality treatments in sweet potatoes during storage

The objective of this experiment was to study changes in sprouting and quality of three sweet potato roots; 'Tainung 10' (TN10), 'Tainung 57' (TN57) and 'Satusumahikari' (SH), as affected by white-, red- and blue-light treatments during storage for 3 months at 25°C. Three samples of each variety were randomly withdrawn from growth chambers at weekly intervals for quality assessments. We concluded that genotypes treated with various light spectra exhibited specific characteristics of sprouting, weight loss, starch and sugar contents, and β-amylase activity during storage. Compared to white- and blue-light treatments, red-light-treated TN10 roots had a significant lower sprouting rate, sugar content and β-amylase activity. However, in the case of TN57, with blue-light treatment, there was a significantly lower sprouting rate, sugar content and β-amylase activity compared to the other treatments. SH contained a significantly lower starch level and β-amylase activity, and higher sucrose content than in TN10 and TN57 in all treatments. Sprouting of stored roots showed starch hydrolysis accompanied by the accumulation of sugar and β-amylase activity. Although starch was converted into sugars, sprouting from the raw sweet potato was delayed during prolonged storage by the light spectral treatment. To develop a practical technique of manipulating the light spectrum requires experimentation with more cultivars and a wider range of light regions and temperatures.