Mapping dry matter and sugars in potato tubers for prediction of whole tuber process quality

Abstract

Processing quality parameters within different sections of potato (Solanum tuberosum L.) tubers grown in Manitoba were measured to determine variability within tubers and to determine if whole tuber quality could be predicted from a specific section. The section that provided the best prediction of overall tuber quality parameters was determined. Changes in specific gravity (SG) and sugars in the outside and the inside of tubers during several months of storage were also measured. Dry matter (DM) of potato cvs. Russet Burbank and Shepody was generally higher at the apical and stem ends than in the middle section and was significantly higher in the outside than in the inside of the tuber. Sucrose concentration generally decreased from the stem end to the apical end of the tuber in Russet Burbank but increased from the stem end to the apical end in Shepody. Sucrose, glucose, and fructose were generally greater, though not always significantly, in the inside of the tuber compared with the outside with the exception of sucrose in Shepody where it was somewhat higher in the outside section. Glucose and fructose generally decreased from stem end to apical end although the difference between the two ends was significant only in Shepody. There was more variability in DM and the three sugars within Shepody tubers than those of Russet Burbank. The outer section of the tuber at the centre of the longitudinal axis (CO) was, overall, most highly correlated to the DM (r2 > 0.91) of the entire tuber for both cultivars and would be the most appropriate single location for estimating the DM of the entire tuber. Sugar concentrations of whole tubers could not consistently be estimated from that of any particular tuber location although the CO section had the highest correlations overall. During 6 mo storage SG did not change while sucrose decreased and glucose and fructose generally increased in both the outside (CO) and inside (CI) of the tuber. Linear regressions relating DM, SG, and sugars of the CO section to the whole tuber, and relating DM to SG were developed. Key words: Solanum tuberosum L., specific gravity, storage, processing, product quality