Browsing by Author "Popovich DG"

Now showing 1 - 4 of 4
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    An improved MTT colorimetric method for rapid viable bacteria counting
    (Elsevier BV, 2023-11) Xu W; Shi D; Chen K; Palmer J; Popovich DG
    The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay has been employed in the analysis of bacterial growth. In comparison to experiments conducted on mammalian cells, the MTT bacterial assay encounters a greater number of interfering factors and obstacles that impact the accuracy of results. In this study, we have elucidated an improved MTT assay protocol and put forth an equation that establishes a correlation between colony-forming units (CFU) and the amount of formazan converted by the bacteria, drawing upon the fundamental principle of the MTT assay. This equation is represented as CFU=kF. Furthermore, we have explicated a methodology to determine the scale factor "k" by employing S. aureus and E. coli as illustrative examples. The findings indicate that S. aureus and E. coli reduce MTT by a cyclic process, from which the optimal reduction time at room temperature was determined to be approximately 30 mins. Furthermore, individual E. coli exhibits an MTT reduction capacity approximately four times greater than that of S. aureus. HPLC analysis proves to be the most accurate method for mitigating interferences during the dissolution and quantification of formazan. Additionally, this study has identified a new constraint related to the narrow linear range (0-125 μg/mL) of formazan concentration-absorbance and has presented strategies to circumvent this limitation.
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    Phenolic compounds from macadamia husk: An updated focused review of extraction methodologies and antioxidant activities
    (Elsevier Ltd on behalf of the Institution of Chemical Engineers, 2024-12) Ahmed MF; Popovich DG; Whitby CP; Rashidinejad A
    This review explores the potential of agri-food waste materials, with a particular focus on macadamia nut by-products. Industrial processing of macadamia nuts yields a significant volume of by-products, including green husk and woody shell. Recent research has highlighted these by-products as readily available, cost-effective rich sources of phenolic compounds, renowned for their potent antioxidant and antibacterial properties. This paper emphasizes the importance of selecting an optimal extraction method to fully harness the bioactive potential of these phenolic compounds. In this work, we provide a comprehensive overview of conventional and advanced extraction techniques that are used to extract phenolic compounds from macadamia by-products, with a particular focus on the methods applied to macadamia green husk. Among the various techniques, it appears that ultrasound-assisted extraction, especially when combined with aqueous organic solvents, is more efficient than other methods for this purpose. This review also addresses the challenges in phenolic compound recovery, primarily due to the lack of a standardized extraction process. This often results in the extensive use of extraction solvents to achieve an extract that is rich in phenolic compounds. Overall, this research offers a valuable understanding of the most effective methods for the extraction and recovery of phenolic compounds from macadamia by-products and discusses the potential for scaling up these extraction processes. Hence, it can serve as a useful resource for researchers and industry professionals interested in sustainable and efficient utilization of by-products of the nut industry.
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    Recent advances in encapsulation techniques for cinnamon bioactive compounds: A review on stability, effectiveness, and potential applications
    (Elsevier Ltd, 2024-02) Culas MS; Popovich DG; Rashidinejad A
    Cinnamon is renowned worldwide for its beneficial health-promoting properties. However, its application in the food industry faces significant challenges due to chemical instability, leading to the degradation of its bioactive compounds, as well as the development of undesirable sensory characteristics caused by the precipitation of salivary proteins by the bioactives. To address these issues, encapsulation methods (both micro and nano) have been developed and studied extensively. This review focuses on recent advances in such encapsulation techniques used to safeguard and deliver cinnamon bioactives, with special emphasis on the spray drying method. The methods employed to evaluate the physicochemical, rheological, and sensorial properties of nano and microparticles are also comprehensively reviewed. The review addresses the challenges associated with encapsulation, including encapsulation efficiency, long-term stability, and release kinetics, and proposes potential strategies to overcome these challenges. Furthermore, the paper presents future perspectives and research directions in cinnamon encapsulation, shedding light on novel materials, advanced characterization techniques, and hybrid encapsulation systems. Overall, encapsulation demonstrates the potential to preserve and harness the therapeutic benefits of cinnamon's bioactive compounds for a wide array of food, pharmaceutical, and nutraceutical applications. With ongoing research and advancements in encapsulation techniques, cinnamon bioactives can be effectively utilized to develop functional and health-enhancing products, catering to the diverse needs of consumers worldwide.
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    Reduction of the attachment, survival and growth of L. monocytogenes on lettuce leaves by UV-C stress
    (Elsevier Ltd, 2021-06) Kyere EO; Popovich DG; Palmer J; Wargent JJ; Fletcher GC; Flint S
    Mild stress of leafy greens by UV-C radiation has been reported to stimulate plant defences capable of reducing pathogens on produce surfaces. In this study, the attachment, survival and growth of Listeria monocytogenes was investigated on lettuces stressed with mild UV-C radiation (1.3 and 2.6 kJm−2). Attachment of L. monocytogenes to UV-C stressed (1.3 kJm−2) lettuce leaves after 1 h was significantly (p < 0.05) reduced by 1.4–1.5 log cfu/cm2. UV-C stress also reduced the survival of L. monocytogenes on lettuce by 1.8–1.9 log cfu/g 96 h after inoculation, however a higher dosage of UV-C stress (2.6 kJm−2) did not inhibit the survival of L. monocytogenes. The total phenolic compounds in lettuce significantly increased following UV-C stress (1.3 kJm−2) indicating the accumulation of polyphenols might have contributed to the inhibition of L. monocytogenes attachment and growth. Appropriate dosage of mild UV-C stress of lettuce can reduce the attachment, survival and growth of L. monocytogenes in lettuce and can therefore be explored further for application in fresh produce safety.