title: Comparative study of pulsed electric field and thermal processing of apple juice with particular consideration of juice quality and enzyme deactivation.
abstract: As an alternative to thermal pasteurization, pulsed electric fields (PEF) were applied to apple juices on laboratory and pilot plant scale, investigating the effects on juice quality. PEF application still falls under the EU Novel Food Regulation. Consequently, extensive investigation of quality parameters is a prerequisite to prove substantial equivalence of juices resulting from the novel process and conventional production, respectively. Juice composition was not affected by PEF treatment. However, browning of the juices provided evidence of residual enzyme activities. On laboratory scale, complete deactivation of peroxidase (POD) and polyphenoloxidase (PPO) was achieved when PEF treatment and preheating of the juices to 60 degrees C were combined. Under these conditions, a synergistic effect of heat and PEF was observed. On pilot plant scale, maximum PPO deactivation of 48% was achieved when the juices were preheated to 40 degrees C and PEF-treated at 30 kV/cm (100 kJ/kg). Thus, minimally processed juices resulted from PEF processing, when applied without additional conventional thermal preservation. Since this product type was characterized by residual native enzyme activities and nondetectable levels of 5-hydroxymethylfurfural, also when preheating up to 40 degrees C was included, it ranged between fresh and pasteurized juices regarding consumers' expectation of freshness and shelf life. Consistent with comparable iron contents among all juice samples, no electrode corrosion was observed under the PEF conditions applied.
authors.affiliation: Institute of Food Science and Biotechnology, Chair of Plant Foodstuff Technology, Hohenheim University, August-von-Hartmann-Strasse 3, 70599 Stuttgart, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Schilling
authors.forename: Sandra
authors.initials: S
authors.lastname: Schmid
authors.forename: Henry
authors.initials: H
authors.lastname: Jäger
authors.forename: Michael
authors.initials: M
authors.lastname: Ludwig
authors.forename: Helmut
authors.initials: H
authors.lastname: Dietrich
authors.forename: Stefan
authors.initials: S
authors.lastname: Toepfl
authors.forename: Dietrich
authors.initials: D
authors.lastname: Knorr
authors.forename: Sybille
authors.initials: S
authors.lastname: Neidhart
authors.forename: Andreas
authors.initials: A
authors.lastname: Schieber
authors.forename: Reinhold
authors.initials: R
authors.lastname: Carle
mesh_terms: D000975:Antioxidants / Q000032:analysis; D001628:Beverages / Q000032:analysis*; D004156:Catechol Oxidase / Q000378:metabolism; D004560:Electricity; D005419:Flavonoids / Q000032:analysis; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000201:enzymology*; D006358:Hot Temperature; D015416:Maillard Reaction; D027845:Malus / Q000201:enzymology*; D009195:Peroxidase / Q000378:metabolism; D010636:Phenols / Q000032:analysis; D059808:Polyphenols
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols; D004156:Catechol Oxidase; D009195:Peroxidase