Physical, physiochemical and electrochemical responses of ‘Galaxy’ apples to mild bruising

Abstract

Minor mechanical injuries such as shocks, vibrations, compressions cause tissue damages and eventually quality losses of fruits. Bruising one of type of the minor mechanical injuries is usually neglected and might result serious postharvest losses. The study was set out to evaluate physical, physiochemical and electrochemical quality parameters of ‘Gal-axy’ apples bruised with a 50- or 70-N compressive force followed by storage at 15°C for 20 days. The degree of bruising on fruit skin and in mesocarp tissue was subjectively and instrumentally measured. The 70-N force caused more bruising than the 50-N force, as expected. Darkening and reddening were found to be the most significant coloring symptom of bruised tissues. Showing a steady rate over time, neither weight nor firmness loss was affected by bruising. Bruising also did not have a significant effect on soluble solids, titratable acidity or vitamin C contents, all of which slightly decreased in the course of the storage. Expressing a decline with storage duration, electrochemical parameters redox potential, pH, P-value and resistivity quantified by Bioelectric Vincent method were not significantly affected by bruising as well. The rate of decline in P-value and resistivity of apples was however sharper than in redox potential and pH, irrespective of bruising treatment. The Bioelectric Vincent method was found to be insufficient to detect mild bruising on ‘Galaxy’ apples. Instrumental colorimeter, however, detected the bruising very effectively. © ISHS 2017.