Anthocyanin Distribution and Sampling Method in Colored Potato Tubers

In order to investigate the difference of anthocyanin distribution in potato tuber and explore the most applicable method for sampling economically and scientifically, three colored potato materials, ‘Heijingang (variety)’, ‘21-1 (line)’ and ‘Jianchuanhong (variety)’ with various pigment accumulation were selected for the analysis of the tuber anthocyanin content depend on the size (large, middle and small) and length (longitudinal and the lateral) of the tuber, as well as the angle (transversely, vertically and diagonally) from where the tuber was cut for sampling. The results showed that the distribution of the potato anthocyanins in the same species was significantly different due to the material and size differences (P<0.05). In the same tuber, the allocation of anthocyanins was of significant difference along the horizontal area, which was significantly higher in the potato flesh (P<0.05). Specifically, the anthocyanins level in the skin of ‘Jianchuanhong’ was about 7-fold higher than the flesh, while it was 2.5-fold and 1.5-fold higher in ‘Heijingang’ and ‘21-1’ respectively. By comparison, in the longitudinal distribution, anthocyanins contents in the top and umbilical regions of the ‘Heijingang’ and ‘21-1’ were both significantly higher than the middle part, whereas the top of the ‘Jianchuanhong’ was significantly higher than the middle and the umbilical area (P<0.05). Relatively, the three methods utilized to cut the tubers from three angles did not reflect significant differences in terms of the anthocyanin quantification (P˃0.05), showing that sample lesser amount of the tuber through the diagonal cut might be a much more efficient and economical way for the potato pigment analysis. Lastly, this study also compared the analytical effects between tuber grinding and pulping, demonstrating that the pulping method could cause the anthocyanin loss drastically (P<0.05), which was not an appropriate way for the potato tuber pigment quantification. Thus, cutting the potato tuber from a morphologically diagonal angle with lesser amount would be a quite favorable approach for the lab detection of potato tuber anthocyanins.