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

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.

Physicochemical and microbiological characteristics of beef treated with high-intensity ultrasound and stored at 4 °C.

BACKGROUND: The application of high-intensity ultrasound causes changes in the physical and chemical properties of biological materials including meat. In this study the physicochemical and microbiological characteristics of beef after the application of high-intensity ultrasound for 60 and 90 min and subsequent storage at 4 °C for 0, 2, 4, 6, 8 and 10 days were evaluated. RESULTS: The ultrasound-treated meat showed higher (P < 0.05) pH and luminosity than the control, with no difference (P > 0.05) between sonication times. The redness of ultrasound-treated meat was initially lower than that of control meat, but no difference (P > 0.05) was observed after day 8 of storage. The 90 min ultrasound-treated meat had higher (P < 0.05) yellowness during the entire storage period. Ultrasound decreased (P < 0.05) coliform, mesophilic and psychrophilic bacteria in the meat throughout the storage period; however, the original microbial loads increased constantly during refrigeration. The 90 min ultrasound-treated meat showed the greatest reduction in microbial load during storage. Coliforms and psychrophilic bacteria were the most affected by ultrasound. CONCLUSION: The application of high-intensity ultrasound to beef semitendinosus muscle stored at 4 °C decreased bacterial growth without affecting the physicochemical quality of meat.

Ultrasound-enhanced mass transfer in Halal compared with non-Halal chicken.

BACKGROUND: Halal foods are often perceived as wholesome products that are specially selected and processed to achieve the highest standards of quality. In this study, dye penetration from an aqueous solution of methylene blue (1 mol L(-1)) was used as a model for the marination process of Halal and non-Halal chicken breast. RESULTS: The effect of dye penetration was evaluated by three techniques: (1) the mass of methylene blue solution in the samples was quantified by mass gain, (2) the amount of dye absorbed was determined by spectroscopy and (3) the penetration distance of dye inside the samples was measured. For non-Halal meat, ultrasound increased the amount of dye inside the samples by 6 and 13% after 15 and 30 min respectively. The effect on Halal meat was much more pronounced, with an increase in dye uptake of over 60% being observed for both time periods. CONCLUSION: Dye penetration is an indication of meat permeability and so can be used as an estimate of marinading of meat. Thus the use of high-power ultrasound has potential in poultry-processing methods, in particular that of Halal chicken marination.

Does ultrasound equally improve the quality of beef? An insight into longissimus lumborum, infraspinatus and cleidooccipitalis.

Quality of bovine longissimus lumborum, infraspinatus and cleidooccipitalis muscles after high-intensity ultrasound (HIU; 40 kHz and a power of 11 W/cm2 for 0, 40, 60, and 80 min) and aging (0, 7 and 14 d) was evaluated. The effects of HIU on pH and color of meat were not considered negative. HIU improved water holding capacity (WHC) of l.lumborum and infraspinatus only after aging. Whereas, the WHC of cleidooccipitalis increased immediately after sonication. The total collagen of HIU treated samples was significantly lower compared to the untreated samples. Ultrasonication for 80 min was the most effective for infraspinatus and cleidooccipitalis. Toughness decreased with HIU, iii nfraspinatus and l.lumborum tenderized more than cleidooccipitalis. HIU application and 7 d aging is an excellent combined treatment to improve tenderness of the three muscles. Infraspinatus was the most tender meat. HIU could help industry to improve the quality of beef as it helps in tenderization and accelerates maduration particularly of l.lumborum.

Ultrasound-mediated DNA transfer for bacteria.

In environmental microbiology, the most commonly used methods of bacterial DNA transfer are conjugation and electroporation. However, conjugation requires physical contact and cell-pilus-cell interactions; electroporation requires low-ionic strength medium and high voltage. These limitations have hampered broad applications of bacterial DNA delivery. We have employed a standard low frequency 40 kHz ultrasound bath to successfully transfer plasmid pBBR1MCS2 into Pseudomonas putida UWC1, Escherichia coli DH5alpha and Pseudomonas fluorescens SBW25 with high efficiency. Under optimal conditions: ultrasound exposure time of 10 s, 50 mM CaCl(2), temperature of 22 degrees C, plasmid concentration of 0.8 ng/microl, P. putida UWC1 cell concentration of 2.5 x 10(9) CFU (colony forming unit)/ml and reaction volume of 500 microl, the efficiency of ultrasound DNA delivery (UDD) was 9.8 +/- 2.3 x 10(-6) transformants per cell, which was nine times more efficient than conjugation, and even four times greater than electroporation. We have also transferred pBBR1MCS2 into E. coli DH5alpha and P. fluorescens SBW25 with efficiencies of 1.16 +/- 0.13 x 10(-6) and 4.33 +/- 0.78 x 10(-6) transformants per cell, respectively. Low frequency UDD can be readily scaled up, allowing for the application of UDD not only in laboratory conditions but also on an industrial scale.

The progressive role of acoustic cavitation for non-invasive therapies, contrast imaging and blood-tumor permeability enhancement.

INTRODUCTION: Drug delivery pertaining to acoustic cavitation generated from ultrasonic (US) irradiation is advantageous for devising smarter and more advanced therapeutics. The aim is to showcase microbubbles as drug carriers and robust theranostic for non-invasive therapies across diverse biomedical disciplines, highlighting recent technologies in this field for overcoming the blood-brain barrier (BBB) to treat cancers and neurological disorders. AREAS COVERED: This article reviews work on the optimized tuning of ultrasonic parameters, sonoporation, transdermal and responsive drug delivery, acoustic cavitation in vasculature and oncology, contrast imaging for real-time magnification of cell-microbubble dynamics and biomolecular targeting. Scholarly literature was sought through database search on key terminology, latest topics, reputable experts and established journals over the last five years. EXPERT OPINION: Cavitation offers immense promise in overcoming current diffusion and convection limitations for treating skull/brain/vascular/tissue injuries and ablating tumors to minimize chronic/acute effects. Since stable cavitation facilitates the restoration of US-opened BBB and the modulation of drug concentration, US equipment with programmable imaging modality and sensitivity are envisaged to create safer miniaturized devices for personalized care. Due to differing biomedical protocols with regard to specific medical conditions, quantitative and qualitative controls are mandatory before translation to real-life clinical applications can be accomplished.