Inactivation of yeast and bacteria using combinations of radio frequency electric fields and ultraviolet light

Enhancing waste sludge solubilization through radio frequency treatment perforating bacterial cells

Sludge solubilization is known as a rate-limiting step of anaerobic digestion. Although radio frequency (RF) has been applied for sludge pretreatment due to its similar thermal effect as microwave, the potential non-thermal effects of RF treatment remain controversial. In this study, we demonstrate that RF pretreatment enhances the solubilization and lysis of sludge by 8.02%-19.69% through both thermal and non-thermal mechanisms with less energy input. Scanning electron microscope images provide direct evidence that RF-induced microcurrents penetrated bacterial cells, leading to the release of intracellular substances through formed pores. Additionally, the non-thermal effect of RF treatment which could weaken the cell protection and accelerate the lysis rate involves the disruption of binding forces between extracellular polymeric substances and microbial cells. On average, the utilization of RF at a frequency of 27.12 MHz demonstrates its efficacy as a sludge pretreatment technique, as evidenced by a 13.39% reduction in energy consumption and a 16.9% improvement in treatment performance compared to conductive heating (CH). The findings of this study elucidate the possible mechanism of RF treatment of sludge and could establish a theoretical basis for the practical application of RF treatment in sludge management.

Nostoc sphaeroides Cyanobacteria: a review of its nutritional characteristics and processing technologies

Nostoc sphaeroides is an edible Cyanobacterium which has high nutritional value and is widely used in dietary supplements and therapeutic products. N. sphaeroides contains protein, fatty acid, minerals and vitamins. Its polysaccharides, phycobilin, phycobiliproteins and some lipids are highly bioactive. Thus, N. sphaeroides possesses anti-oxidation, anti-inflammation and cholesterol reducing functions. This paper reviews and evaluates the literature on nutritionally and functionally important compounds of N. sphaeroides. It also reviews and evaluates the processing of technologies used to process N. sphaeroides from fresh harvest to dry particulates including pretreatment, sterilization and drying, including their impact on sensorial and nutritional values. This review shows that a suitable combination of ultrasound, radio frequency and pulse spouted microwave with traditional sterilization and drying technologies greatly improves the sensorial and nutritive quality of processed N. sphaeroides and improves their shelf life; however, further research is needed to evaluate these hybrid technologies. Once suitably processed, N. sphaeroides can be used in food, cosmetics and pharmaceutical drugs as an ingredient.

Effect of UVC Light-Emitting Diodes on Pathogenic Bacteria and Quality Attributes of Chicken Breast

ABSTRACT

This study was conducted to investigate the inactivation of foodborne pathogens and the quality characteristics of fresh chicken breasts after UVC light-emitting diode (UVC-LED) treatment. Fresh chicken breasts were separately inoculated with Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes at initial populations of 6.01, 5.80, and 6.22 log CFU/cm2, respectively, and then treated with UVC-LED irradiation at 1,000 to 4,000 mJ/cm2. UVC-LED irradiation inactivated the test bacteria in a dose-dependent manner. After UVC-LED treatment at 4,000 mJ/cm2, the populations of Salmonella Typhimurium, E. coli O157:H7, and L. monocytogenes on chicken breasts were decreased by 1.90, 2.25, and 2.18 log CFU/cm2, respectively. No significant changes (P > 0.05) were found in color, pH, texture, and thiobarbituric acid-reactive substances of chicken breasts following UVC-LED irradiation at doses ≤4,000 mJ/cm2. These results indicate that UVC-LED radiation is a promising technology for reducing the level of microorganisms while maintaining the physicochemical characteristics of poultry meat.

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