Inactivation kinetics of pectin methylesterase in orange juice as a function of pH and temperature/time process conditions

Abstract

Pasteurisation of orange juice (OJ) is necessary to prevent spoilage due to microorganisms and enzymes, mainly pectin methylesterase (PME). PME has a higher thermal resistance than the bacteria and yeasts existing in OJ and therefore its inactivation is used as a parameter to define the time/temperature combination of the thermal process. The enzyme has isoforms with different activities and thermal resistances. A three-parameter model can be used to describe the kinetics of PME inactivation, where the more and less thermally resistant fractions are represented. In this study the thermal inactivation kinetics was evaluated at six pH values (3.6, 3.7, 3.8, 3.9, 4.0 and 4.1), three minimal temperatures (82.5, 85.0 and 87.5 • C) and at least six holding times for each condition. It was found that the thermolabile PME fraction (a) was influenced by pH and processing temperature. A slower reaction rate constant (k 1 ) was found for juices with pH values of 3.8 and 3.9 at the studied temperatures. The highest inactivation levels were obtained in juices with pH values of 3.6 and 3.7.

Inactivación Térmica de Pectinmetilesterasa en Jugo de Uchuva (Physalis peruviana L.)

“…4. Con un valor P>0,05, para los cuatro atributos del jugo de uchuva, se puede inferir que no existe una diferencia estadísticamente significativa para cada atributo comparado entre el jugo sin tratamiento y los jugos pasteurizados a 70 °C, 80 °C y 90 °C durante 10 s, en resumen el jugo sin tratamiento frente a los jugos pasteurizados no se diferencia estadísticamente, autores como Hirsch et al (2011) encontraron que incluso despues de aplicar una pasteurizacion a 85 °C durante 10 s en jugo de naranja se logró mantener las cualidades organolépticas de un jugo fresco, de igual modo, los tratamientos aplicados al jugo de uchuva no afectan las propiedades organolépticas, sin embargo, hay que tener especial cuidado al aplicar una pasteurización severa, ya que es importante la conservación de las cualidades organolépticas y nutricionales del jugo las cuales se pueden ver afectadas por procesos térmicos prolongados (Sila et al, 2006;Tribess y Tadini, 2006).…”

“…La presencia de PME provoca que en las bebidas de estos frutos se formen dos fases, una de ellas clara en la parte superior y otra turbia en la parte inferior dejando un aspecto visible indeseado en el producto final; sin embargo, para reducir la actividad PME en alimentos con alto contenido de pectina una alternativa es la pasteurización (Cinquanta et al, 2010;Anthon et al, 2002), con la cual, se logra reducir a niveles aceptables  10% la actividad enzimática residual, factor problema en la calidad de jugos (Osorio et al, 2008;Carbonell et al, 2006), sin embargo los jugos comerciales conservados por pasteurización sometidos a temperaturas altas y tiempos prolongados, reducen también componentes deseables como nutrientes, color, aroma y textura que se destruyen en diferentes porcentajes, resultando en pérdidas significativas de calidad (Tribess y Tadini, 2006;Raviyan et al, 2005), de ahí la importancia de optimizar el tratamiento térmico aplicado mediante la aplicación de diseños experimentales, que permitan conservar al máximo los atributos de calidad del jugo (Montgomery y Runger, 2003). Aspectos técnicos que aún no han sido abordados en la Uchuva y que de alguna manera potencializarían la posible industrialización de este importante fruto de las zonas andinas, donde el fruto se produce.…”

Impacto del tratamiento por pulsos eléctricos de alta intensidad y altas presiones hidrostáticas sobre la calidad y seguridad microbiológica de un alimento mezcla de zumo de naranja y leche

“…Pectin Methyl Esterase (PME) is an important enzyme in orange juice based products and PME spoilage effects in orange juice are well known as cloud loss or gelification of juice concentrates (Tribess and Tadini, 2006). Thermal preservation treatments (88-95 ºC, 15-30 s) are based on the PME inactivation level achieved (>90%) due to its higher thermotolerance than those of majority of microorganisms found naturally in these products (Irwe and Olson, 1994).…”

“…After HHP treatment the average loss was between -14.2 to 7.5% at an initial temperature of 30 ºC depending on the pressure levels and 22.9 to 42.3% at 50 ºC. The results showed the potential of the nonthermal technologies in providing food with a higher standard of quality compared to thermal processing.Effect of PEF, HHP and thermal on PME and aroma Pectin Methyl Esterase (PME) is an important enzyme in orange juice based products and PME spoilage effects in orange juice are well known as cloud loss or gelification of juice concentrates (Tribess and Tadini, 2006). Thermal preservation treatments (88-95 ºC, 15-30 s) are based on the PME inactivation level achieved (>90%) due to its higher thermotolerance than those of majority of microorganisms found naturally in these products (Irwe and Olson, 1994).…”

“…This comparison can be done using a microbiological index (inactivation of a selected microorganism or microbial flora) or enzymatic index (inactivation of a selected enzyme). In our study the conditions to obtain the same degree of PME inactivation by thermal and PEF treatment were selected from a previous work (Sampedro et al, 2008).Pectin methyl esterase (PME) is an important enzyme in orange juice based products and thermal preservation treatments are based on the PME inactivation level of >90 % because its thermotolerance is higher than the majority of microorganisms found naturally in this type of product, causing the cloud loss or gelification of juice concentrates (Tribess et al, 2006). Severe conditions (90 ºC, 1 min or 95 ºC, 30 s) are necessary to inactivate orange PME (Cameron et al, 1994, Do Amaral et al, 2005.…”