Pulsed electric field and mild heating for milk processing: a review on recent advances.

Pulsed electric field (PEF) treatment consists of exposing food to electrical fields between electrodes within a treatment chamber, which can improve the preservation of fresh-like products such as milk. Although several studies support the use of PEF technology to process milk at low temperature, these studies reported microbial reductions of around 3 log10 cycles and also indicated a limited impact of PEF on some endogenous and microbial enzymes. This scenario indicates that increasing the impact of PEF on both enzymes and microorganisms remains a major challenge for this technology in milk processing. More recently, combining PEF with mild heating (below pasteurization condition) has been explored as an alternative processing technology to enhance the safety and to preserve the quality of fresh milk and milk products. Mild heating with PEF enhanced the safety of milk and derived products (3 log10 -6 log10 cycles reduction on microbial load and drastic impact on the activity enzymes related to quality decay). Moreover, with this approach, there was minimal impact on enzymes of technological and safety relevance, proteins, milk fat globules, and nutrients (particularly for vitamins) and improvements in the shelf-life of milk and selected derived products were obtained. Finally, further experiments should consider the use of milk processed by PEF with mild heating on cheese-making. The combined approach of PEF with mild heating to process milk and derived products is very promising. The characteristics of current PEF systems (which is being used at an industrial level in several countries) and their use in the liquid food industry, particularly for milk and some milk products, could advance towards this strategy. © 2019 Society of Chemical Industry.

Impact of the soy protein replacement by legumes and algae based proteins on the quality of chicken rotti.

The addition of different protein sources (soy, bean, lentil, broad bean, Spirulina, and Chlorella) on nutritional, physicochemical and sensory properties of chicken rotti was evaluated. Significant changes were observed in physicochemical composition, textural properties and amino acid content of chicken rotti after adding the proteins from different sources, thus influencing the sensory acceptance and preference. Spirulina and Chlorella rotti presented a slight increase of pH and seaweed caused a decrease in some colour parameters. The highest lipids contents were found in chicken rotti added of with Spirulina and lentil proteins. Chicken rotti prepared with lentil protein also showed the highest values for ash content. Chicken rotti enriched with seaweed protein presented the highest total amino acid content. Principal component analysis showed that broad beans and lentils proteins as interesting ingredients to replace soy protein in chicken rotti.

Effect of non-thermal hurdles in extending shelf life of cut apples.

Pulsed electric fields (PEF), high pressure processing (HPP) and conventional method of heating (90 °C, 60s) were evaluated as blanching methods for fresh cut apples. The settings employed for PEF and HPP were 1.5 kV/cm, 100 pulses, 4 Hz and 600 MPa for 2 min respectively. The blanched samples were soaked in sucrose solution (60°Brix, 60 min) containing ascorbic acid, citric acid, sodium benzoate, and potassium sorbate. The treated samples were packed and pasteurized using either hot water (90 °C, 15 min) or HPP (600 MPa, 10 min). These samples were analyzed for physicochemical and microbiological attributes immediately after treatment and after 2 months of cold storage. The combination of different hurdles in all groups completely inhibited microbial growth. However, in terms of color values and texture retention, the apple cuts treated with PEF followed by hot water pasteurization were of a better quality when compared to HPP pasteurized ones (P < 0.05).

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

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.

Bio-refinery of Chlorella sorokiniana with pulsed electric field pre-treatment.

The aim of this work was to investigate the potential of PEF technology for green extraction of microalgal pigments and lipids from fresh Chlorella sorokiniana suspensions. Efficiencies of PEF treatment and different solvent systems application to C.sorokiniana were compared to efficiencies of untreated biomass extraction. Differences in chlorophyll extraction of untreated and PEF treated C.sorokiniana were only seen at short extraction times. Beneficial PEF-effect was minimised for long-time extractions of larger algae quantities where yields aligned. Extraction attempts on C. sorokiniana lipids did not show increased extractability after PEF treatment, which underlined the statement of PEF representing a rather ineffective disruption method for microalgae holding rigid cell walls.

Effect of electrohydraulic shockwave treatment on tenderness, muscle cathepsin and peptidase activities and microstructure of beef loin steaks from Holstein young bulls.

Hydrodynamic pressure processing (HDP) or shockwave treatment improved tenderness (18% reduction in Warner-Bratzler shear force (WBSF) of beef loin steaks. Endogenous muscle proteolyic activities (cathepsins and peptidases) and protein fragmentation of sarcoplasmic and myofibrillar proteins detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were not influenced by HDP. However, microstructure changes were clearly detected using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Specifically a disruption of the structure at the muscle fiber bundles and an increased endomysium space were observed. The present paper supports the evidence of physical disruption of the muscle fibers as a cause behind the tenderness improvement. The paper discusses the possible mechanisms responsible for the meat tenderisation induced by HDP treatment.

New developments in shockwave technology intended for meat tenderization: Opportunities and challenges. A review.

Meat tenderness is an important quality parameter determining consumer acceptance and price. Meat tenderness is difficult to ensure in the global meat chain because the production systems are not always aiming at this purpose (ex.: cattle derived from milk production) and by the existence within the carcass of "tough" primals. Different methods can be used by the meat industry to improve meat tenderness each with its advantages and drawbacks. The application of hydrodynamic pressure or shockwaves has showed outstanding improvements by reducing the Warner Bratzler Shear Force by 25% or more. However, the technology has not penetrated into the market as first systems were based on the use of explosives and further developments seemed to lack the robustness to fulfill industrial requirements. The present paper describes the main challenges to construct a prototype for the continuous treatment of meat by shockwaves based on electrical discharges under water. Finally, improvements on the tenderness of meat by using the novel prototype are presented.

High hydrostatic pressure/temperature modeling of frankfurter batters.

The impact of high pressure/temperature treatment on structure modification and functional sensory properties of frankfurter batter was investigated. The degree of solubilization of meat proteins, particularly of myosin, was identified as a key process with significant effect on the batter's structural properties. The maximal solubilization level was at 200 MPa/40 °C IT for all formulations which was found to be treatment time dependent. The impact of the pressurizing gradient - PG=40 MPa/s and PG=2.5 MPa/s was investigated and estimated to have a significant effect on the protein network and functional properties, respectively. These were improved at low PG (2.5 MPa/s) as a phenomenon of secondary network formation parallel to the main matrix. Batter secondary-structure characteristics were found to be ionic-strength dependent. According to SDS-PAGE analysis, the major role in the solubilization, aggregation and gelation processes occurring in the aqueous phase was due to the myosin S-1 and S-2, N-terminal, C-terminals, the MLC and actin during the high pressure/temperature treatment.

Molecular effects of high-pressure processing on food studied by resonance Raman.

Pressurization may cause unwanted side effects including color or texture changes of fish and meat. The color changes of poultry, pork, and smoked salmon were studied by CIE L*, a*, b* system, and resonance Raman (RR). High-pressure processing (HPP) of pork and chicken meat resulted in significant color modification at pressures higher than 270 and 280 MPa, respectively. RR spectra were taken after a high-pressure treatment of pork meat. According to the RR-data, deoxymyoglobin is the dominating myoglobin species in pork meat. High-pressure treatment causes conformational changes resulting in a stabile nonnative ferrous myoglobin species while the ferrous myoglobin state is maintained. High-pressure treatment causes a decrease of the relative RR intensities of astaxanthin by salmon as probed with 514 nm. RR spectra excited at 413 nm revealed a heterogeneous broadening of astaxanthin bands accompanied by the formation of deoxymyoglobin or deoxyhemoglobin. The broadening is interpreted as the degradation products of astaxanthin. Obviously, the high-pressure treatment of smoked salmon triggers redox processes of astaxanthin and the heme protein.

Comparative study of pulsed electric field and thermal processing of apple juice with particular consideration of juice quality and enzyme deactivation.

As an alternative to thermal pasteurization, pulsed electric fields (PEF) were applied to apple juices on laboratory and pilot plant scale, investigating the effects on juice quality. PEF application still falls under the EU Novel Food Regulation. Consequently, extensive investigation of quality parameters is a prerequisite to prove substantial equivalence of juices resulting from the novel process and conventional production, respectively. Juice composition was not affected by PEF treatment. However, browning of the juices provided evidence of residual enzyme activities. On laboratory scale, complete deactivation of peroxidase (POD) and polyphenoloxidase (PPO) was achieved when PEF treatment and preheating of the juices to 60 degrees C were combined. Under these conditions, a synergistic effect of heat and PEF was observed. On pilot plant scale, maximum PPO deactivation of 48% was achieved when the juices were preheated to 40 degrees C and PEF-treated at 30 kV/cm (100 kJ/kg). Thus, minimally processed juices resulted from PEF processing, when applied without additional conventional thermal preservation. Since this product type was characterized by residual native enzyme activities and nondetectable levels of 5-hydroxymethylfurfural, also when preheating up to 40 degrees C was included, it ranged between fresh and pasteurized juices regarding consumers' expectation of freshness and shelf life. Consistent with comparable iron contents among all juice samples, no electrode corrosion was observed under the PEF conditions applied.