Tianbo Wang (College of Food Science and Engineering, Shan Dong Agricultural University, Tai’an 271018, China), Qungguo Wang (College of Food Science and Engineering, Shan Dong Agricultural University, Tai’an 271018, China), Francis Pupin (Mann Lab, Dept. Plant Sciences, University of California, Davis CA 95616) and Marita Cantwell (Mann Lab, Dept. Plant Sciences, University of California, Davis CA 95616)
Sunchokes (Helianthus tuberosus L.) are inulin accumulating tubers native to North America that are edible raw or cooked, and have good potential as a fresh-cut product. Sunchokes perform well as fresh-cut slices except for the development of a reddish discoloration on the cut surface. Dip treatments with ethanol (5%) provided effective control of discoloration. Untreated or ethanol-treated sliced tubers were stored in air at 0 degrees C and 5 degrees C, with best quality of untreated slices (visual, color values) maintained at 0 degrees C, but ethanol treatments retarded discoloration at both temperatures. Ethanol treatment suppressed respiration rates, and reduced wound-induced PAL activity and phenolic concentrations. Controlled atmospheres of 3% O2 with 6 or 12% CO2 at 5 degrees C were less effective than ethanol dips to retard discoloration, although high CO2 atmospheres also retarded PAL activity and synthesis of phenolics. Techniques tested for increasing endogenous ethanol concentrations included holding tubers in a nitrogen atmosphere for up to 12 days at 10 degrees C, and using a static system after nitrogen flushing to allow accumulation of CO2 (up to 20%). These treatments were only partially effective to control slice discoloration. Another approach to retard discoloration was using preprocessing treatments including hot water dips plus a delay at 20 degrees C before cutting, and curing treatments (storage at 20 degrees C for 7 and 14 days). These treatments were effective to reduce discoloration on the fresh-cut slices.