Quality changes and respiration rates of fresh-cut sunchoke tubers (Helianthus tuberosus L.)
Changes in quality attributes (discoloration, surface dehydration, translucency, color values, texture), respiration, phenolics and phenylalanine ammonia lyase (PAL) and polyphenol oxidase activities of sunchoke tuber slices were studied at 0, 5 and 10C. Cleanly cut smooth surfaces had less wound-induced discoloration and surface drying than rougher cut surfaces. The main quality defect was red discoloration, and a* and hue color values were highly correlated to this defect. The time course of discoloration was related to wound-induced respiration and PAL activity but not polyphenol oxidase activity or concentrations of soluble phenolics. Respiration rates of slices at 0, 5 and 10C averaged 5, 14 and 26 μL CO2/g-h, respectively, during 7 days. No decay was observed under any condition. Storage at 0 and 5C effectively retarded surface discoloration, but 0C was clearly better. A shelf life of 9–12 and 6–8 days was obtained with sunchoke slices at 0 and 5C, respectively, while shelf life was 3 days at 10C.
Sunchoke tubers contain indigestible inulins and have potential as a fresh-cut product or a component in fresh-cut mixtures to be consumed raw or cooked. Sliced tubers retain quality when held at 0–5C, but discoloration, the main defect limiting shelf life, will occur more rapidly at 5C. The rate and severity of discoloration was related to storage temperature and to wound-induced increases in respiration and PAL activity. With this information, strategies to effectively control discoloration can be implemented.