Compuestos antioxidantes

Innovative Food Science and Emerging Technologies 7 (2006) 40 – 48 www.elsevier.com/locate/ifset

Inactivation of plant pectin methylesterase by thermal or high intensity pulsed electric field treatments
Alexandre Espachs-Barroso a, Ann Van Loey b, Marc Hendrickx b, Olga Martın-Belloso a,* ´
a

CeRTA-UTPV, Departamento de Tecnologıa de Alimentos, Universidad de Lleida, Avda. Alcalde RoviraRoure 191, 25198, Lleida, Spain ´ b Laboratory of Food Technology, Department of Food and Microbial Technology, Faculty of Applied Bioscience and Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium Received 24 April 2005; accepted 25 July 2005

Abstract A comparative study between new and traditional food preservation technologies was performed on pectinmethylesterase (PME) inactivation from different plant sources. PME was extracted from carrots, tomatoes, bananas and oranges and was purified by affinity chromatography. Its inactivation was investigated during high intensity pulsed electric fields (HIPEF) and thermal treatments. Thermal treatment was performed at temperatures from 54 -C to 81 -C and up to 120 min treatment time. PME inactivationwas adequately described by a first-order kinetic model for PME from bananas, carrots and tomatoes, whereas a biphasic model described adequately thermal inactivation of orange PME. The thermal stable fraction of orange PME was the least sensible to heat and carrot PME was the most thermally sensitive. HIPEF treatment consisted of 40-As-square-wave pulses applied up to a total treatment time of1.6 ms at 0.5 or 5 Hz and an electric field between 13.2 and 19.1 kV/cm. The higher the electric field, total treatment time or pulse frequency the higher the degree of PME inactivation from all sources. Maximum enzyme inactivation was: 87% for orange and tomato PME, 83% for carrot PME and 45% for banana PME at the most intense conditions. D 2005 Elsevier Ltd. All rights reserved.
Keywords: Pectinmethylesterase; Thermal treatment; Non-thermal processing; Pulsed electric fields

Industrial relevance: Increasing studies show that using high intensity pulsed electric fields technology for fruit juices pasteurisation is feasible in the near future. A critical point on the fruit juice production and preservation is the pectin methyl esterase activity control. Consequently, the effect ofHIPEF on PME activity has a great industrial relevance. This paper shows high inactivation percentages of PME from different plant sources with a HIPEF treatment carried out at moderate temperatures (55-65 -C) and offers an attractive alternative to the traditional heat treatment.

1. Introduction Viscosity, cloud stability, and other food properties are affected by the impact of pectic enzymes,particularly pectin methylesterase (PME; EC 3.1.1.11). PME is a pectic enzyme widely distributed in higher plants and which can also be synthesized by microorganisms such as

* Corresponding author. Tel.: +34 973702593; fax: +34 973702596. E-mail address: omartin@tecal.udl.es (O. Martın-Belloso). ´ 1466-8564/$ - see front matter D 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.ifset.2005.07.002

fungi, bacteria and yeast (Kertesz, 1951). Moreover, PME effectively increases the extraction yield of juices by conventional methods (Anastasakis, Lindamood, Chism, & Hansen, 1987), and it is also used to obtain natural clouding agents from orange peels (Espachs-Barroso, Aguilera-Prim, & Martın Belloso, 2003). In all cases, ´ the reduction of PME activity is required for cloud stability ofcloudy plant juices, since PME catalyses the hydrolysis of the methylester groups from pectin, thereby generating acidic pectin with lower degree of esterification and methanol (Rombouts, Versteeg, Karman, &

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Pilnik, 1982). The interaction of desterified pectin and calcium ions forms...