Pulsed Electric Field Processing of Orange Juice: A Review on Microbial, Enzymatic, Nutritional, and Sensory Quality and Stability

Abstract

During the last decades pulsed electric field (PEF) processing received considerable attention due to its potential to enhance food products or create alternatives to conventional methods in food processing. It is generally acknowledged that PEF processing can deliver safe and chill-stable fruit juices with fresh-like sensory and nutritional properties. Relatively low-processing temperature and short residence times can achieve highly effective inactivation of microorganisms while retaining product quality. A first commercial application of PEF for preservation of fruit juices was launched in 2006 in the United States. Since then, industrial-scale processing equipment for liquid and solid products were developed and, in Europe in 2009, an industrial juice preservation line was installed using 20 kV/cm pulses at 40 to 50• C to extend the chill-stability of fruit juices, including citrus juices and smoothies, from 6 to 21 d. The related PEF processing costs are in the range of US $0.02 to 0.03 per liter and are justified due to access to new markets and reduced return of spoiled product. However, despite its commercial success there are still many unknown factors associated with PEF processing of fruit and citrus juices and many conflicting reports in the literature. This literature review, therefore, aims to provide a comprehensive overview of the current scientific knowledge of PEF effects on microbial, enzymatic, nutritional, and sensory quality and stability of orange juices.

Impact of the Pulsed Electric Field Treatment on Bioactive Food Compounds: Bioaccessibility and Bioavailability

“…Killing of vegetative bacteria and yeasts by PEF processing is probably not due to the products of electrolysis or temperature increase alone, but rather by the applied electrical field strength and the processing time [32][33][34]. There are a few theories on the mechanisms involved in the disruption of the cell membrane when subjected to electric fields.…”

“…There are a few theories on the mechanisms involved in the disruption of the cell membrane when subjected to electric fields. Two hypotheses, electrical breakdown and osmotic disproportion, are widely approved and are supported on the same principles [34]. The theory of electrical breakdown considers the cell membrane as a condenser loaded with a dielectric medium [34,35].…”

“…Two hypotheses, electrical breakdown and osmotic disproportion, are widely approved and are supported on the same principles [34]. The theory of electrical breakdown considers the cell membrane as a condenser loaded with a dielectric medium [34,35]. Accumulation of free charges at the internal and outer surface of the cell membrane forms a Transmembrane Potential (TMP) of approximately 10 mV [34,36].…”

“…The theory of electrical breakdown considers the cell membrane as a condenser loaded with a dielectric medium [34,35]. Accumulation of free charges at the internal and outer surface of the cell membrane forms a Transmembrane Potential (TMP) of approximately 10 mV [34,36]. When an external electrical field is applied; ions inside and outside of the cell move along with the electric field until they are restrained and accumulated at the membrane causing a rise in the TMP.…”

“…Further application of electric fields causes more stress on cell membrane and reduction in its thickness ends up with pore formation when applied electric field strength is above the critical electric field potential of the cell membrane. If the application of electric field continues, the pores become irreversible and cells cannot reseal themselves leaking of intracellular materials, and thus, cell death occurs [34,37]. The principle of osmotic irrationality, on the other hand, defines the imbalance of cell membrane components through the formation of hydrophilic pores in the membrane and the opening of the protein channels.…”