Pasteurization of apple juice by pulsed electric fields and effects on quality properties

Apple juice samples were processed by pulsed electric fields (PEF), and processing parameters were determined by central composite design in this thesis. According to the experimental design apple juice samples were processed under different electric field strength (kV/cm), frequency (Hz), treatment time (µs) and energy (J) values, and changes on pH, Brix, titratable acidity, conductivity, color (L, a and b), hue, chroma, total color difference (TCD), antioxidant capacity, total phenolic substance content, organic acids (tartaric, quinic, oxalic, malic, citric, fumaric and ascorbic acids), phenolic compounds (cholorogenic acid, caffeic acid, (-)epicatechin, p-cumaric acid, ferrulic acid, sihapic acid, quercetin, gallic acid and catechin), hydroxyl methly furfural (HMF) and furfural were measured. It was measured that compare to control samples changes on chroma, hue and TRD were significant (p≤0.05). Even though no significant changes were reported on organic acids, HMF, furfural and most of the phenolic compounds (p>0.05); significant difference was detected on phenolic compounds of (-) epicatechin, ferrulic acid and gallic acid (p≤0.05). It is revealed that PEF can successfully be applied processing of apple juice without significantly changing important quality parameters. Keywords: Pulsed electric fields (PEF), apple juice, phenolic compounds, organic acids, quality characteristics.