Effects of pH and temperature on inactivation ofSalmonella typhimuriumDT104 in liquid whole egg by 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.

Combined Pulsed Electric Field with Antimicrobial Caps for Extending Shelf Life of Orange Juice

The purpose of this study was to investigate the effectiveness of combined pulsed electric fields (PEF) and antimicrobial packaging treatment in maintaining the quality and stability of orange juice stored at 10 °C. Orange juice was treated by PEF and stored in glass jars with antimicrobial caps coated with 10 µL of carvacrol essential oil (AP). Microbial reductions and physiochemical properties of juice samples were determined after treatments and during storage at 10 °C. Orange juice samples subjected to the combined treatment (PEF+AP) had the lowest yeast and mold populations after 14 day-storage at 10 °C. There were no significant differences in pH, acidity, color, total soluble solid contents, total phenol compounds, and Vitamin C among all samples after treatments. Storage studies showed that PEF, AP, and PEF+AP treatments maintained the quality and stability of orange juice stored at 10 °C for 5 weeks but lost Vitamin C. This study provides valuable information to juice processors for consideration and design of nonthermal pasteurization with antimicrobial packaging of juice products.

Inactivation of Escherichia coli K-12 in Liquid Egg White By a Flow-through Pulsed Uv Light Treatment System

ABSTRACT

Unpasteurized liquid egg can be contaminated with pathogenic microorganisms and may cause foodborne outbreaks. Thus, it is essential to decontaminate the liquid egg to ensure food safety. Pulsed UV light is one of the emerging technologies for food decontamination in recent years. This static treatment system has been studied previously in our laboratory. However, continuous processing using a flow-through treatment system needs to be evaluated for potential commercial applications. Therefore, in this study, a flow-through treatment system of pulsed UV light was evaluated and optimized for inactivation of Escherichia coli K12NSR for liquid egg white decontamination. Treatment factors including flow rate (40 to 80 mL/min), number of passes (one to three passes), and distance from the sample to the pulsed UV light strobe (5 to 13 cm) were optimized using response surface methodology. This methodology suggested three passes with 40 mL/min flow rate and a 5-cm distance as the optimum conditions. The model was then validated for the maximum reduction of E. coli K12NSR, which was measured as 1.57 log CFU/mL at the optimal conditions. The energy doses of the pulsed UV light and temperature changes of the liquid egg white during the treatment were measured. Furthermore, several quality parameters were assessed at the optimum treatment conditions to determine the impact of the flow-through pulsed UV processing on the quality of liquid egg white. The results showed significant differences in pH, lipid oxidation, turbidity, and color between control and pulsed UV light-treated samples (P < 0.05). However, there was no significant difference in foaming ability or foam stability between pulsed UV light-treated samples and the control. Overall, this study demonstrated the potential of flow-through pulsed UV light to decontaminate liquid egg white, but further research is needed for optimal enhancement.

HIGHLIGHTS

Modifying the Functional Properties of Egg Proteins Using Novel Processing Techniques: A Review

Egg proteins can be used in a wide range of food products, owing to their excellent foaming, emulsifying, and gelling properties. Another important functional property is the susceptibility of egg proteins to enzymatic hydrolysis, as protein digestion is closely related to its nutritional value. These functional properties of egg proteins are likely to be changed during food processing. Conventional thermal processing can easily induce protein denaturation and aggregation and consequently reduce the functionality of egg proteins due to the presence of heat-labile proteins. Accordingly, there is interest from the food industry in seeking novel nonthermal or low-thermal techniques that sustain protein functionality. To understand how novel processing techniques, including high hydrostatic pressure, pulsed electric fields, ionizing radiation, ultraviolet light, pulsed light, ultrasound, ozone, and high pressure homogenization, affect protein functionality, this review introduces the mechanisms involved in protein structure modification and describes the structure-functionality relationships. Novel techniques differ in their mechanisms of protein structure modification and some have been shown to improve protein functionality for particular treatment conditions and product forms. Although there is considerable industrial potential for the use of novel techniques, further studies are required to make them a practical reality, as the processing of egg proteins often involves other influencing factors, such as different pH and the presence of other food additives (for example, salts, sugar, and polysaccharides).

Aggregation of egg white proteins with pulsed electric fields and thermal processes

BACKGROUND

Pulsed electric field (PEF) processing is progressing towards application for liquid egg to ensure microbial safety. However, it usually causes protein aggregation, and the mechanism is still unclear. In this study, egg white protein was applied to investigate the changes in protein structure and mechanism of aggregates formation and a comparison was made with thermal treatment.

RESULTS

Soluble protein content decreased with the increase of turbidity after both treatments. Fluorescence intensity and free sulfhydryl content were increased after being treated at 70 °C for 4 min. Less-remarkable changes of hydrophobicity were observed after PEF treatments (30 kV cm(-1) , 800 µs). Soluble and insoluble aggregates were observed by thermal treatment, and disulfide bonds were the main binding forces. The main components of insoluble aggregates formed by thermal treatment were ovotransferrin (30.58%), lysozyme (18.47%) and ovalbumin (14.20%). While only insoluble aggregates were detected during PEF processes, which consists of ovotransferrin (11.86%), lysozyme (21.11%) and ovalbumin (31.07%). Electrostatic interaction played a very important role in the aggregates formation.

CONCLUSION

PEF had a minor impact on the structure of egg white protein. PEF had insignificant influence on heat-sensitive protein, indicating that PEF has potential in processing food with high biological activity and heat sensitive properties. © 2015 Society of Chemical Industry.

Combination of pulsed electric fields, mild heat and essential oils as an alternative to the ultrapasteurization of liquid whole egg

The production of microbiologically safe liquid whole egg (LWE) by industrial ultrapasteurization is restricted by the high thermal sensitivity of LWE components. This research proposes an alternative treatment based on the application of pulsed electric fields (PEF) and mild heat, in the presence of natural essential oils (EOs) or their individual components (ICs). The obtained results indicate that the successive application of PEF (25kV/ and 100kJ/kg) followed by heat (60°C during 3.5') to LWE added with 200μL/L of lemon EO would reach 4log10cycles of inactivation of Salmonella Senftenberg 775W and Listeria monocytogenes, when any of these barriers acting alone inactivated less than 1.5log10cycles of either bacteria. Therefore, the synergism between lemon EO and the successive application of PEF and heat would provide a safety level similar to that of ultrapasteurization treatment for Salmonella Senftenberg 775W and L. monocytogenes, but at a lower temperature. To a lesser extent, synergism with the successive application of PEF and heat was also observed in the presence of 200μL/L of carvacrol, citral, (+)-limonene, or mandarin EO, reaching about 3.5log10cycles of inactivation in Salmonella Senftenberg and 3.0log10cycles in L. monocytogenes, respectively. A sensory test on LWE containing 200μL/L of each additive in the form of omelets and sponge cakes revealed that this concentration of mandarin EO, lemon EO, or (+)-limonene did not decrease the sensory acceptability of the LWE-containing products, and lemon EO and mandarin EO even increased the hedonic acceptability of sponge cakes. In conclusion, this process could be applied in the food industry to obtain microbiologically safe LWE, which could be used to produce egg-based products without decreasing (and even increasing) their sensory appeal.