Correlations of Color Changes Encountered Throughout Storage with Polyphenol Oxidase Enzyme Activity, Sugar Content and Total Phenolics of Hazelnuts

In this study, relationships of color changes encountered throughout the storage period (12 months, uncontrolled storage conditions) with polyphenol oxidase (PPO) enzyme activity, total sugar, reducing sugar, non-reducing sugar and total phenolics of the ‘Tombul’, ‘Palaz’, ‘Çakıldak’ and ‘Kalınkara’ hazelnut cultivars were investigated. In all hazelnut cultivars, L* values decreased and a* values increased throughout the storage period. The present findings revealed that cultivar factor influenced color changes. It could be stated that an increase in sugar contents of the ‘Tombul’, ‘Palaz’ and ‘Çakıldak’ cultivars and total phenolics of the ‘Kalınkara’ cultivar increased color darkening. PPO activity did not have color darkening effects. Varying color changes of the cultivars indicated that cultivar separation should be performed before storage. Sugar reactions should be taken into consideration while identifying storage temperature and relative humidity since there were significant correlations between sugar contents and color change. Increasing total phenolics increased color darkening. Such effects of total phenolics on color darkening were similar in all cultivars.