Effects of PEF and heat pasteurization on PME activity in orange juice with regard to a new inactivation kinetic model

PubMedID: 25038650The inactivation kinetics of pectin methyl esterase (PME) during the shelf life (4 °C-180 days) of freshly squeezed orange juice samples processed by both pulsed electric fields (PEF) and heat pasteurization (HP) was evaluated in the study. The PME inactivation level after the PEF (25.26 kV/cm-1206.2 µs) and HP (90°C-20 s) treatments were 93.8% and 95.2%, respectively. The PME activity of PEF-processed samples decreased or did not change, while that of HP samples increased during storage (p < 0.01). A kinetic model was developed expressing PME inactivation as a function of the PEF treatment conditions, and this enabled the estimation of the reaction rate constant (587.8-2375.4 s -1), and the time required for a 90% reduction (De, 3917.7-969.5 s). Quantification of the increase in PEF energy to ensure a ten-fold reduction in De (ze, 63.7 J), activation electric fields (-921.2 kV cm-1mol-1), and electrical activation energy (12.9 kJ mol-1) was also carried out. Consequently, PEF processing was very effective for the inactivation of PME and for providing stability of orange juice during storage. © 2014 Published by Elsevier Ltd.DPT 2009K 120 410 ZF2010BAP4, ZF2009YL87 104 O 585The authors would like to thank the State Planning Organization (Project No: DPT 2009K 120 410), TUBITAK (Project No: 104 O 585) and Cukurova University (Project No: ZF2010BAP4 and ZF2009YL87) for financial supports

Comparison of phenolic compounds of orange juice processed by pulsed electric fields (PEF) and conventional thermal pasteurisation

Processing of orange juice by pulsed electric fields (PEF) and thermal pasteurisation was carried out to compare changes in total phenolic concentration, hydroxybenzoic acid, hydroxycinnamic acids, flavonols, flavones and flavonones before and after being stored at 4 °C for 180 days. Changes in the initial total phenolic concentration of the samples varied depending on the applied electric field intensity and thermal pasteurisation. Hesperidin and chlorogenic acids were detected as the most abounded flavonoid and phenolic acids in the orange juice, respectively. Except for syringic acid and neoeriocitrin, the concentration of the phenolic compounds indentified in the orange juice samples enhanced after the PEF or thermal pasteurisation. The samples treated with PEF had more stable flavonoids and phenolic acids than those treated with the thermal pasteurisation. The PEF-treated samples had higher sensory scores than the heat-treated samples. © 2013 Elsevier Ltd. All rights reserved.DPT 2009 K 120 410 ZF2010BAP4 104 O 585The authors would like to thank the Ministry of Development State Planning Organisation ( Project No. DPT 2009 K 120 410 ), TUBITAK ( Project No. 104 O 585 ) and Cukurova University ( Project No: ZF2010BAP4 ) for financial supports