Modelling and optimization of inactivation of Lactobacillus plantarum by pulsed electric field treatment

Abstract

Aims: The effect of critical pulsed electric field (PEF) process parameters, such as electric field strength, pulse length and number of pulses, on inactivation of Lactobacillus plantarum was investigated. Methods and Results: Experiments were performed in a pH 4Á5 sodium phosphate buffer having a conductivity of 0Á1 S m À1 , using a laboratory-scale continuous PEF apparatus with a co-linear treatment chamber. An inactivation model was developed as a function of field strength, pulse length and number of pulses. Based on this inactivation model, the conditions for a PEF treatment were optimized with respect to the minimum energy required to obtain a certain level of inactivation. It was shown that the least efficient process parameter in the range investigated was the number of pulses. The most efficient way to optimize inactivation of Lact. plantarum was to increase the field strength up to 25Á7 kV cm À1 , at the shortest pulse length investigated, 0Á85 ls, and using a minimum number of pulses. The highest inactivation of Lact. plantarum at the lowest energy costs is obtained by using the equation: E ¼ 26Á7s 0Á23 , in which E is the field strength and s the pulse length. An optimum is reached by substituting s with 5Á1. Conclusions: This study demonstrates that the correct choice of parameters, as predicted by the model described here, can considerably improve the PEF process. Significance and Impact of the Study: The knowledge gained in this study improves the understanding of the limitations and opportunities of the PEF process. Consequently, the advantage of the PEF process as a new option for non-thermal decontamination can be better utilized.

Comparative analyses of prediction models for inactivation of Escherichia coli in carrot juice by means of pulsed electric fields

“…Recently many non-thermal preservation technologies have been proposed. Among all emerging non-thermal technologies, high intensity PEF processes the food without compromising on taste and flavor (Lado and Yousef 2002;Abram et al 2003). For example, the PEF treatment to carrot juice assured insignificant diminution in pH, electric conductivity, color, brix and titratable acidity along with log reduction of 4.3 and 3.4 D for mold and yeast respectively while keeping the mineral element persevered (Akin and Evrendilek 2009).…”

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

“…Nevertheless, some authors concluded that applying the same quantity of energy, the inactivation achieved was greater at higher pulse width. increased the pulse duration from 2 to 4 μs for the same treatment time, they found that the inactivation was greater with 4 μs but the differences were greater at high electric field intensities and Abram et al, (2003) also found that when they increased the pulse width over 1 μs, with E=25 kV/cm and the same energy input, the inactivation increased with the pulse width. The effect of pulse width is not clear and seems to vary depending on the conditions applied such as electric field.…”

“…However, several studies conclude that a pulse width increase produces higher microbial inactivation Abram et al, 2003Abram et al, , Élez et al, 2005, but only under low field intensities (25-28 kV/cm). In the enzyme inactivation by PEF, Giner et al, (2001) and Élez et al, (2006 b) observed a greater POD and PPO inactivation by increasing pulse width.…”

“…The inactivation mechanism of PME against thermal and high pressure differs and more studies are needed to understand it. In studies on inactivation of microorganisms by PEF, some works were focused on analyzing the influence of process variables on the inactivation, using buffers or foods with a simple composition as a suspension medium such as skim milk (Martín et al, 1997), phosphate buffer (Wouters et al, 1999), NaCl and peptone solution , sodium phosphate buffer (Abram et al, 2003), citrate phosphate McIlvaine buffer (Álvarez et al, 2003) and apple juice from concentrate (Heinz et al, 2003). Some of these studies (Wouters et al, 1999;Abram et al, 2003;Heinz et al, 2003) are accompanied by a calculation of the energy applied, which makes it possible to assess their possible applicability in the industry by comparison with the energy cost of traditional heat treatments, and it can also be useful for comparing PEF inactivation treatments of microorganisms in various conditions.…”

“…It has been proved that a value close to 2 μs obtains a greater microbial reduction within a lesser energy consumption. A pulse width increase does not produce in many cases any significant effect on the inactivation degree.However, several studies conclude that a pulse width increase produces higher microbial inactivation Abram et al, 2003 Abram et al, , Élez et al, 2005, but only under low field intensities (25-28 kV/cm). In the enzyme inactivation by PEF, Giner et al, (2001) and Élez et al, (2006 b) observed a greater POD and PPO inactivation by increasing pulse width.…”