New Kinetic Approach to the Evolution of Polygalacturonase (EC 3.2.1.15) Activity in a Commercial Enzyme Preparation Under Pulsed Electric Fields

Advances in pulsed electric stimuli as a physical method for treating liquid foods

There is a need for alternative technologies that can deliver safe and nutritious foods at lower costs as compared to conventional processes. Pulsed electric field (PEF) technology has been utilised for a plethora of different applications in the life and physical sciences, such as gene/drug delivery in medicine and extraction of bioactive compounds in food science and technology. PEF technology for treating liquid foods involves engineering principles to develop the equipment, and quantitative biochemistry and microbiology techniques to validate the process. There are numerous challenges to address for its application in liquid foods such as the 5-log pathogen reduction target in food safety, maintaining the food quality, and scale up of this physical approach for industrial integration. Here, we present the engineering principles associated with pulsed electric fields, related inactivation models of microorganisms, electroporation and electropermeabilization theory, to increase the quality and safety of liquid foods; including water, milk, beer, wine, fruit juices, cider, and liquid eggs. Ultimately, we discuss the outlook of the field and emphasise research gaps.

A novel kinetic model for a cocoa waste fermentation to ethanol reaction and its experimental validation

A non-segregated kinetic model is proposed to describe a fermentation process of agro-industrial residues derived via cocoa (mucilage juice) by Pichia kudriavzevii. The novel proposed hybrid model is based on a multiple coupling reaction mechanisms (structured) to describe the kinetics of substrate consumption, biomass, carbon dioxide, and ethanol, coupled to an unstructured model for the activity enzyme. The parameters of the kinetic model are estimated by non-linear least-squares curve fitting using the Marquardt-Levenberg algorithm. In addition, numerical simulations were compared with the experimental data via residual graphs. The effectiveness of the model was statistically evaluated using dimensionless efficiency coefficients under different initial conditions. A global sensitivity analysis was applied (Fisher's information matrix). The experimental results of the batch reactor showed a maximum ethanol concentration of 29 g/L, with a yield of 0.48 g-ethanol/g-glucose and a productivity of 0.30 g/L h. The method determined that the cell formation coefficient and the specific substrate consumption rate (θ1 and θ2) directly influence most of the states of our system. The proposed scheme is particularly suitable to assist in the rational design of cell factory properties or fermentation processes because it can represent the complex biochemistry in more detail and under different initial experimental conditions; the above reveals that the generated model is robust and can be considered for control and optimization purposes.

Quality-related enzymes in plant-based products: effects of novel food processing technologies part 2: pulsed electric field processing

Pulsed electric field (PEF) processing is an effective technique for the preservation of pumpable food products as it inactivates vegetative microbial cells at ambient to moderate temperature without significantly affecting the nutritional and sensorial quality of the product. However, conflicting views are expressed about the effect of PEF on enzymes. In this review, which is part 2 of a series of reviews dealing with the effectiveness of novel food preservation technologies for controlling enzymes, the scientific literature over the last decade on the effect of PEF on plant enzymes is critically reviewed to shed more light on the issue. The existing evidence indicates that PEF can result in substantial inactivation of most enzymes, although a much more intense process is required compared to microbial inactivation. Depending on the processing condition and the origin of the enzyme, up to 97% inactivation of pectin methylesterase, polyphenol oxidase, and peroxidase as well as no inactivation have been reported following PEF treatment. Both electrochemical effects and Ohmic heating appear to contribute to the observed inactivation, although the relative contribution depends on a number of factors including the origin of the enzyme, the design of the PEF treatment chamber, the processing condition, and the composition of the medium.