Storage induced changes of potato properties as detected by DMA

Dynamic mechanical analysis (DMA) was applied to the potato tissues ('cortex', 'pith', and 'side' surface) of two long stored (more than five months) cultivars: waxy 'Nicola' and more mealy 'Saturna' in the temperature range 30-90 °C and constant air relative humidity of 90%. The results were compared with those obtained for the same cultivars and their parts about one month after harvest. The DMA scans showed the differences of the two cultivars and the effect of storage mainly for the “starch” peak. The “starch” peak was shifted due to storage to lower and higher temperatures for 'Nicola' and 'Saturna', respectively. The “starch” peaks are asymmetric. High and stable (not influenced by storage) asymmetry was observed in 'Saturna'. The asymmetry indicates long-time internal cellular stresses that could lead to the potato sloughing. On the other hand, the “starch” peak asymmetry was much lower in 'Nicola'. During storage, this asymmetry was reduced or changed into the opposite asymmetry characterized by a quick module decrease after reaching the peak.

► Asymmetry of DMA 'starch' peaks characterize sensitivity of potato to sloughing. ► The 'starch' peaks moves during storage to lower ('Nicola') and higher ('Saturna') temperatures. ► After storing the biggest changes in loss tangent were observed at appr. 50 °C. ► High asymmetry of 'starch' peak was observed in 'Saturna'.