Browsing by Author "Jodkowska, Monika"

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    Are microbubbles magic or just small? a direct comparison of hydroxyl radical generation between microbubble and conventional bubble ozonation under typical operational conditions
    (Elsevier, 2022-01-24) John, Alexander; Carra, Irene; Jefferson, Bruce; Jodkowska, Monika; Brookes, Adam; Jarvis, Peter
    The application of microbubbles for water treatment is an emerging technology which has been shown to significantly enhance gas–liquid contacting processes. When applied to ozonation, microbubble technology has been shown to enhance mass transfer and the speed and extent of compound removal compared with conventional bubbling techniques. One explanation as to why microbubble systems outperform conventional systems is that microbubbles shrink, collapse and spontaneously generate hydroxyl radicals which is thought to enhance the speed of compound removal. This study compared microbubble (mean diameter 37 μm) and conventional bubble (mean diameter 5.4 mm) ozonation systems under identical conditions. The experiments were normalised for effective ozone dose to determine whether microbubble ozonation generated significantly more hydroxyl radicals than conventional bubble ozonation. 4-chlorobenzoic was used as the hydroxyl radical probe and the proportion of hydroxyl radicals generated for a given effective ozone dose was quantified. The •OH-exposure to O3-exposure (the ) was used to compare the systems. The ratio of the mean to mean was 0.73, 0.84 and 1.12 at pH 6, 7 and 8 respectively. Statistical assessment of the showed that there was no significant difference between the bubble systems. No evidence was found to support the hypothesis that microbubble systems generate more •OH. Instead, the level of •OH-exposure is linked to the effective dose and pH of the system and future designs should focus on those factors to deliver •OH based benefits.
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    Mapping variability of mycotoxins in individual oat kernels from batch samples: implications for sampling and food safety
    (MDPI, 2025-01-11) Teixido-Orries, Irene; Molino, Francisco; Castro-Criado, Bianca; Jodkowska, Monika; Medina, Angel; Marín, Sonia; Verheecke-Vaessen, Carol
    Oats are susceptible to contamination by Fusarium mycotoxins, including deoxynivalenol (DON), zearalenone (ZEN), and T-2/HT-2 toxins, posing food safety risks. This study analyses the variation in levels of 14 mycotoxins in 200 individual oat kernels from two DON-contaminated batch samples (mean = 3498 µg/kg) using LC-MS/MS. The samples also contained deoxynivalenol-3-glucoside (DON-3G), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and ZEN. Contamination levels varied notably among individual kernels, with DON detected in 70% of them, followed by DON-3G (24.5%) and 3-ADON (20.5%). Importantly, 8% of kernels exceeded the EU legal limit for DON (1750 µg/kg), and some occasionally surpassed limits for ZEN and T-2/HT-2. Correlation analyses revealed strong associations between DON and its derivatives but weaker correlations with other toxins. Mycotoxin ratios varied widely, indicating that although they often co-occur, their concentrations differ between kernels. Contamination did not significantly impact kernel weight, though a slight trend toward lower weights in contaminated kernels was noted. Additionally, sampling statistics showed that as the percentage of selected kernels increased, the probability of batch sample rejection for DON contamination rose significantly. The study highlights the heterogeneity of mycotoxin contamination in oat batches, emphasising the importance of accurate detection and regulatory compliance to ensure safer oat-based products.
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    Removal of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) by coagulation: influence of coagulant and dosing conditions
    (Elsevier, 2025-03-01) Wang, Pin; An, Guangyu; Carra, Irene; Hassard, Francis; Campo Moreno, Pablo; Sakar, Hacer; Jodkowska, Monika; Wang, Dongsheng; Jefferson, Bruce; Chu, Wenhai; Jarvis, Peter
    Per- and polyfluoroalkyl substances (PFAS) pose significant risks to the environment and human health. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are two of the most frequently detected PFAS in the environment. In most surface water drinking water treatment works (WTW), coagulation is the first processes exposed to a range of contaminants, including PFAS. While not designed to be a process for removal of micropollutants, it is important to understand the fate of PFAS in coagulation processes, intended or otherwise, to determine whether water treatment sludge can be a significant sink for this group of micropollutants. This work advances understanding of PFAS removal in coagulation processes by comparing the removal of PFOA and PFOS by four metal coagulants (Zr, Zn, Fe, and Al) from real water matrices. The coagulant performance followed the order Al > Fe > Zr > Zn. Al was taken forward for further evaluation, with significant removal of PFAS (>15 % for PFOA and > 30 % for PFOS) being observed when the pH<5.5 and the dose was > 5 mg Al·L-1. The adsorption of PFOA and PFOS onto flocs through hydrophobic interaction was the primary removal route. The impacts of background matrix on the mechanisms of coagulation for PFAS were explored using five organic compounds. Macromolecular organic compounds contributed to an increase in removal due to the sorption of PFAS and subsequent removal of the organic-PFAS aggregate during coagulation. Low molecular weight organic matter inhibited the removal of PFAS due to the ineffective removal of these compounds during coagulation.
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    Understanding the mechanisms responsible for postharvest tip breakdown in asparagus: a biochemical approach
    (International Society for Horticultural Science, 2023-10-09) Collings, Emma; Landahl, Sandra; Jodkowska, Monika; Nayakoti, Swapna; Chinn, John; Rogers, Hilary; Terry, Leon A; Alamar, M. Carmen
    The UK asparagus season is relatively short (from April to June), resulting in large quantities of spears being imported to provide year-round supply. Currently, asparagus quality can only be maintained for one week, plus seven days shelf-life, using cold storage alone. A limiting factor, which contributes significantly towards commercial losses, is the development of the postharvest physiological disorder tip breakdown (also known as tip rot). The disorder is characterised by darkening tips followed by the presence of water-soaked bracts at the tip of the spear and a foul odour. However, the underlying causes of tip breakdown have not yet been fully elucidated. We hypothesise that fast growth, slow rate of sugar transport and localised cell death may be key components of the mechanism. To gain more insight into tip breakdown development, two asparagus cultivars with low and high susceptibility to tip breakdown (‘Early California’ and ‘Aspalim’, respectively) were grown under controlled conditions and subjected to warm (28/14 °C) and cold (18/8 °C) day/ night temperatures. Harvested spears were subjected to shelf-life storage, 14 days at 7 °C, to subjectively assess early symptoms and further development of tip breakdown. Spears were snap frozen for subsequent biochemical analysis (viz. non-structural carbohydrates and plant growth regulators [PGRs]). Results showed that ‘Aspalim’ spears grown at warmer temperatures had higher incidence of tip breakdown than ‘Early California’. The relationship between incidence and severity of asparagus tip breakdown and the role of PGRs and sugar content during the season, as affected by genotype and growing conditions, are also discussed. The fundamental mechanistic understanding of asparagus tip breakdown will aid to implement optimum postharvest storage strategies to reduce food loss and the associated carbon footprint.