Quantitative and qualitative investigation of phenolic compounds in Gala apple peel

Quantitative and qualitative study of phenolic compounds (phenolic acids, flavanols and anthocyanins) in peel of Gala apple were implemented using analytical HPLC, fluorescence microscopy and epi-illumination light microscopy at three different growing stages [1- fruit early growing stage 2- mid-stage of fruit development (80 days after full bloom) 3- during commercial harvest time]. The results showed qualitative and quantitative differences between diverse growing stages regarding the content and accumulation of phenolic compounds. HPLC and microscopic studies showed that anthocyanin content of peel increased progressively during season. Microscopic data revealed that the highest anthocyanin accumulation occurred at the commercial harvest time. Our results showed that phenolic acids content decreased till mid-season but then, after their content had increasing pattern until commercial harvest time. Microscopic pictures verified this claim as well. Simultaneous comparison of HPLC and microscopy of derived data showed that flavanol content of peel increased towards mid season. In contrast, a drastic decline was recorded for flavanols during commercial harvest time. Comparative survey of microscopic and chromatographic data indicated that the great potential of fluorescence microscopy for study of phenolic compounds in apple peels. In brief, integrated study of phenolic compounds by means microscopic and chromatographic techniques is fast and easy methods for identification and quantification of phenolic compounds leading to accurate conclusion regarding elevation of apple fruit quality criteria.