Postharvest respiration, moisture loss, sensory analysis and compositional changes in jicama (Pachyrhizus erosus) roots.
Bergsma, K. A.; Brecht, J. K.;
Acta Horticulturae Year: 1992 Issue: No. 318 Pages: 325-332 Ref: 7 ref.
1992
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The effects on P. erosus roots of storage temperatures of 5, 10, 15 or 20 deg C and of wrapping with PVC film and coating with paraffin and carnauba wax were investigated. Root respiration rates were very low, initially ranging from 5 ml CO2 kg-1 hr-1 at 5 deg to just under 30 ml CO2 kg-1 hr-1 at 20 deg . Rates declined to 10 ml CO2 kg-1 hr-1 during 13 days at 20 deg , but rose slightly at 10 deg during the same period, while remaining constant at 5 and 15 deg . The DM content of individual roots ranged from 9.5 to 12.5% and changed little during 19 days of storage. Initial soluble solids content was about 6% FW and increased at all temperatures up to 19 days of storage. Total soluble sugars contents (which correlated well with soluble solids contents) were about 45% of the initial DW and increased during the first 7 days of storage at all temperatures, but declined at 20 deg between 7 and 19 days while continuing to increase at 5, 10 or 15 deg . Starch content was about 22% of the initial DW, decreased during the first 7 days of storage at all temperatures, continued to decrease between 7 and 19 days of storage at 5, 10 or 15 deg , but increased at 20 deg during the same period. The FW loss rate was nearly linear for up to 17 days at all storage temperatures, but was greater at 15 and 20 deg than at 5 and 10 deg . Some roots lost as much as 35% of their initial FW during 17 days at 20 deg . Chilling injury symptoms occurred after 7 days at 1, 5 or 10 deg with an additional 2 days at 20 deg to allow symptoms to develop, but were not evident for up to 49 days at 15 deg . Roots stored for 8 days at 15, 25 or 30 deg and 100% RH showed no evidence of periderm formation when compared with control roots held at 20 deg and ambient RH or when compared with initial samples. Paraffin wax was the most effective treatment in reducing moisture loss but resulted in the highest losses due to decay; roots coated with carnauba wax lost nearly as much moisture as controls. Wrapping with PVC film reduced moisture loss by nearly 50% compared with the control without any losses due to decay. Sensory evaluations by an untrained panel indicated no difference between the PVC film-wrapped and paraffin-coated roots in terms of crunchiness and juiciness, but the PVC film-wrapped roots were judged to be crunchier and juicier than the controls and sweeter, with a more typical flavour and aroma than paraffin-coated roots.