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Author: search.filters.author.Laguerre, OnraweeSubject: search.filters.subject.Temperature control

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    Thermal performance evaluation of water-based gel packs and insulating covers: A case study on raw milk preservation for local transport
    (2025-12-01)
    Chaomuang, Nattawut
    ;
    Laguerre, Onrawee
    ;
    Flick, Denis
    ;
    Duret, Steven
    Maintaining the quality and safety of raw milk during transportation to collection centers poses significant challenges for small-scale producers, especially in regions with limited access to advanced refrigeration systems. This study proposes a cost-effective cooling system utilizing water-based phase change material (PCM) gel packs and UV-reflective covers. The thermal performance was evaluated using a tank filled with water, both with and without PCM, under constant and variable ambient temperature conditions. Results demonstrated that the tanks with PCM achieved a temperature reduction of 10–13 °C within an hour. Comparative analysis revealed similar thermal behaviors for milk and water, enabling the extrapolation of results. A simplified heat transfer model based on energy balance was developed to predict product temperature changes under different operational conditions. Some input parameters were adjusted using experimental data, and the model was subsequently validated against separate experimental datasets, showing reasonable accuracy (RMSE < 3.0 °C). The model could be used for application under comparable conditions. Furthermore, milk quality preservation was assessed through the enumeration of Escherichia coli and total coliforms in milk stored in tanks with and without PCM, as well as through predictive microbiological modeling. Both measured and predicted results suggested a moderate reduction in E. coli growth rates (1.1–1.3 times slower) in the tank with PCM, depending on initial microbial load. Based on these findings, the proposed system offers an effective and economical solution for small milk producers, enhancing cold-chain management and reducing spoilage.
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    Storage conditions, energy consumption, and food safety implications of domestic refrigerators in Bangkok
    (2025-12-01)
    Chaomuang, Nattawut
    ;
    Potisuwan, Cheeraphat
    ;
    Duret, Steven
    ;
    Derens-Bertheau, Evelyne
    ;
    Paviet-Salomon, Yvanne
    Domestic refrigeration plays a critical role in food preservation and safety by maintaining optimal storage conditions for perishable items. This study investigated the temperature and humidity conditions, as well as the energy consumption, of domestic refrigerators in Bangkok. Data were collected through on-site investigations of 123 refrigerators using data loggers to record temperature, humidity, and electrical consumption over a five-day period. In addition, a predictive microbiological model was used to assess the potential for microbial growth under the investigated storage conditions, specifically of Listeria monocytogenes and lactic acid bacteria (LAB). Results indicated that although the overall mean temperatures of chilling compartments (5.0 ± 2.5 °C) were within the recommended range for domestic refrigeration, only about 30–40 % of individual refrigerators consistently maintained temperatures at or below 5 °C on the top and middle shelves throughout the five-day monitoring period, where fresh and ready-to-eat products are typically stored. Electrical consumption analysis revealed significant differences across refrigerator types; appliances with two doors and bottom freezers exhibited the highest annual electrical consumption, while single door refrigerators recorded the lowest. However, the specific energy consumption (SEC) did not differ significantly among refrigerator types. The microbial exposure assessment based on a test product highlighted that for over 50 % of refrigerators, L. monocytogenes load exceeds the regulation safety limits (> 10<sup>2</sup> CFU/g) within five days. These findings emphasize the need for improved temperature control, appliance design, and consumer education to ensure food safety and energy efficiency in domestic refrigeration.