Tuber Discoloration Intensity as Detection Method of Irradiated Potatoes

The study was to distinguish between irradiated and unirradiated potatoes, using two different colorimetric methods; (1) color measurement on potatoes slices by the Color Difference Meter (L. a, b, values) and (2) Specrtophotometric measurement at 440nm of the potatoe extract. To potatoes varieties (c.v. Spunta-as table potatoes and Hurmeze-as processing potatoes) were irradiated with 0.1, 0.2, 0.3, 0.5, and 1.0 KGy. Intensity of discoloration of the tubers was measured immediately after irradiation or after 3 and 6 months of storage at room temperature (22-25 C). No difference in L-values was found between irradiated and unirradiated Hurmeze tubers until the last 3 months of storage when values sharply increased at all doses. Such changes were much less in Spunta. Irradiation seemed not to have an effect on L-values for both varieties. In Humeze, the a-values increased with increasing dose immediately after irradiation treatment and during the first 3 months of storage. However, such values diminished for all samples by the end of storage time. The increase in a-values in Spunta was immediately after the treatment, fallowed by sharp decease during the storage. The a-values were more likely to correctly classify irradiated and unirradiated potatoes than were the L-values. However, the increase in a-values and the decease in b-values were effective to detect irradiated tubers of both varieties immediately after treatment and in case of Humeze, values remained low with slight increase or decrease during storage, whereas in Spunta higher values were found only in tubers irradiated at 0.3 KGy or more only during the first 3 months of storage, then dropped again to where they were before storage. In spit of the slight decrease in absorbance of extract of irradiated tubers at 0.2 and 0.3 KGy for both varieties, the spectrophotometric method did not seem to correlate with the fact that irradiation increases discoloration of potatoes