N.N. Misra

In-package atmospheric pressure cold plasma treatment of cherry tomatoes

Cold plasma is increasingly under research for decontamination of foods, especially fresh fruits and vegetables. The effect of cold plasma on food quality, however, remains under researched. This study investigates the effects of cold plasma generated within a sealed package from a dielectric barrier discharge on the physical quality parameters and respiration rates of cherry tomatoes. Respiration rates and weight loss were monitored continuously, while other parameters are reported at the end of storage period. Differences among weight loss, pH and firmness for control and treated cherry tomatoes were insignificant towards the end of storage life. Changes in respiration rates and colour of tomatoes were recorded as a function of treatment, which were not drastic. The results implicate that cold plasma could be employed as a means for decontamination of cherry tomatoes while retaining product quality.

In-package nonthermal plasma degradation of pesticides on fresh produce.

In-package nonthermal plasma (NTP) technology is a novel technology for the decontamination of foods and biological materials. This study presents the first report on the potential of the technology for the degradation of pesticide residues on fresh produce. A cocktail of pesticides, namely azoxystrobin, cyprodinil, fludioxonil and pyriproxyfen was tested on strawberries. The concentrations of these pesticides were monitored in priori and post-plasma treatment using GC-MS/MS. An applied voltage and time dependent degradation of the pesticides was observed for treatment voltages of 60, 70 and 80 kV and treatment durations ranging from 1 to 5 min, followed by 24h in-pack storage. The electrical characterisation revealed the operation of the discharge in a stable filamentary regime. The discharge was found to generate reactive oxygen and excited nitrogen species as observed by optical emission spectroscopy.

Landmarks in the historical development of twenty first century food processing technologies

Over a course of centuries, various food processing technologies have been explored and implemented to provide safe, fresher-tasting and nutritive food products. Among these technologies, application of emerging food processes (e.g., cold plasma, pressurized fluids, pulsed electric fields, ohmic heating, radiofrequency electric fields, ultrasonics and megasonics, high hydrostatic pressure, high pressure homogenization, hyperbaric storage, and negative pressure cavitation extraction) have attracted much attention in the past decades. This is because, compared to their conventional counterparts, novel food processes allow a significant reduction in the overall processing times with savings in energy consumption, while ensuring food safety, and ample benefits for the industry. Noteworthily, industry and university teams have made extensive efforts for the development of novel technologies, with sound scientific knowledge of their effects on different food materials. The main objective of this review is to provide a historical account of the extensive efforts and inventions in the field of emerging food processing technologies since their inception to present day.

Ultrasound assisted hydration of navy beans (Phaseolus vulgaris)

The use of ultrasound to enhance the transport phenomena in food processes has been well recognised in recent times. The objective of this study was to evaluate the effect of sonication on hydration rate and pasting profile of navy beans. The hydration kinetics for control and ultrasound assisted soaking was mathematically described using mechanistic (Fickian diffusion) and empirical (Pelegs equation, Weibull model and First Order equation) models. Ultrasound enhanced the rate of hydration which was evident from the plot of kinetic data and model parameters. The effective diffusivities for water transport without and with ultrasound application were estimated to be 1.36×10(-10) m(2)/s and 2.19×10(-10) m(2)/s respectively, considering Fickian diffusion. The Weibull model was concluded to best predict the hydration kinetics of navy beans in an ultrasonic field. Significant increase in peak viscosity of sonicated bean powder was observed compared to control.

Ultrasound for Improved Crystallisation in Food Processing

Within the food industry, controlling crystallisation is a key factor governing food structure, texture and consumer appeal, with some foods requiring the promotion of crystallisation in a controlled manner (e.g. chocolate) and others a check (e.g. honey). Sonocrystallisation is the application of ultrasound energy to control the nucleation of a crystallisation process. The use of power ultrasound provides a useful approach to producing crystals with desired properties. Sonocrystallisation facilitates process control by modulating crystal size distribution and morphology. This paper details the governing mechanisms of sonocrystallisation. Proven and potential applications of the process in foods are reviewed including chocolate, honey, fats and frozen foods. Challenges of process adoption such as scale-up are discussed.

Surface, Thermal and Antimicrobial Release Properties of Plasma-Treated Zein Films

The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an active ingredient were evaluated. The plasma discharge was optically characterized to identify the reactive species. A significant increase in the film roughness (p 0.05) was observed for the thermal properties of the antimicrobial films after DBD plasma treatment.

Thermodynamics, transport phenomena, and electrochemistry of external field-assisted nonthermal food technologies

ABSTRACT Interest in the development and adoption of nonthermal technologies is burgeoning within the food and bioprocess industry, the associated research community, and among the consumers. This is evident from not only the success of some innovative nonthermal technologies at industrial scale, but also from the increasing number of publications dealing with these topics, a growing demand for foods processed by nonthermal technologies and use of natural ingredients. A notable feature of the nonthermal technologies such as cold plasma, electrohydrodynamic processing, pulsed electric fields, and ultrasound is the involvement of external fields, either electric or sound. Therefore, it merits to study the fundamentals of these technologies and the associated phenomenon with a unified approach. In this review, we revisit the fundamental physical and chemical phenomena governing the selected technologies, highlight similarities, and contrasts, describe few successful applications, and finally, identify the gaps in research.

Inducing a Dielectric Barrier Discharge Plasma Within a Package

Cold atmospheric plasma offers significant potential as a nonthermal decontamination tool for food and medical applications. We present results of a dielectric barrier discharge (DBD) plasma induced in a gas confined by a polymer package. The resultant discharge and contained afterglow are found to have a strong antimicrobial effect.

Characterization of a Novel Cold Atmospheric Air Plasma System for Treatment of Packaged Liquid Food Products

The technology of atmospheric plasma (ionized gas), widely used in material processing, offers one of the most significant breakthroughs in food processing and safety. The technology allows the generation of bactericidal molecules very efficiently with low power requirements. Non-thermal atmospheric plasma has been used to effectively decontaminate surfaces, but has received limited investigation for in-package decontamination. This study demonstrates the potential for in-package plasma treatment of food products in sealed packages. The advantage of in-package cold plasma treatment is that the bactericidal molecules are generated and contained in the package allowing extended exposure to bacteria while reverting back to the original package gas within 24 hr storage. The study treated liquid food surrogates containing bacteria and oxidation sensitive dye (methylene blue) inside sealed packages. The surrogates were placed in 96 well plates and were packaged in air and exposed directly and indirectly to the plasma field in a 2.2 cm high, 23 cm x 31 cm sealed polypropylene container for up to five minutes of treatment. Treatments were carried out using a prototype Dielectric Barrier Discharge (DBD) operating at a voltage of 40 kV, and frequency of 50 Hz. The UV-Vis emission spectra of plasma were collected and analyzed. The spectra showed emission bands for nitrogen and oxygen species including strong emission lines for excited states of the atomic species O, O+, N and N+. The results from the evaluation of methylene blue suggest that direct exposure to the plasma ionization field produces a greater oxidative effect compared to indirect exposure. For five minutes treatment, direct exposure of methylene blue resulted in a 90% reduction in absorbance and indirect exposure of methylene blue resulted in a 75% reduction in absorbance. These reductions may result from conversion of ozone into hydroxyl radicals which reduces the methylene blue from dark blue color to clear. This process appears to be non-reversible. Additionally, bacterial studies examining treatment of E. coli ATCC 25922 suspended in maximum recovery diluent inside of 96 well plates found a 7 log reduction after 50 s treatment and 24 hours storage for both direct and indirect plasma exposure. Ozone concentrations measured immediately after five minutes of ionization were approximately 1600 ppm. The goal of this research is to maximize bacterial reductions and minimize quality (oxidative) loss for liquid food products inside a sealed package.

Microbial inactivation and evaluation of furan formation in high hydrostatic pressure (HHP) treated vegetable-based infant food

The inactivation of pathogenic and spoilage bacteria as well as the formation of food processing contaminants (e.g. acrylamide, furan, etc.) in infant foods is of utmost importance for industry, consumers as well as regulatory bodies. In this study, the potential of high hydrostatic pressure (HHP) for microorganism inactivation including total mesophilic aerobic bacteria (TMA) and total yeasts and molds (TYM) at equivalent processing conditions, as well as its effects on furan formation in vegetable-based infant food was evaluated. The process parameters evaluated were combinations of pressures (200, 300, and 400MPa), temperatures (25, 35, and 45°C), and treatment times (5, 10, and 15min). Pressure, time and temperature had a significant influence on both TMA and TYM inactivation of vegetable-based infant foods, observing a significant reduction in both microbial populations when all the factors were increased, although the extent of reduction was clearly influenced by the type of microorganism. A synergism between pressure, time and temperature was observed for the reduction of both TMA and TYM populations and it was found that HHP at 400MPa resulted in a complete inactivation of TMA as well as TYM after 15min of treatment at 45°C. The furan content in all HHP treated samples was found to be below the limit of detection. Thus, HHP treatment could be considered as a potential alternative to thermal processing of vegetable-based infant foods.