Search Results (154)

Ready-to-eat (RTE) fresh salads are widely consumed for their convenience and nutritional value, but they could represent a relevant food safety concern, as they do not undergo a lethal heat treatment before consumption, and furthermore, they may support the growth of Listeria monocytogenes during refrigerated storage. In this study, the growth potential of L. monocytogenes was evaluated by standardised challenge tests in five commercially available RTE salads: crispy lettuce, baby lettuce, a baby lettuce–spicy mustard mix, and two mâche products from different producers. Three different batches for each product were inoculated with a three-strain cocktail of L. monocytogenes at a target level of approximately 2–3 log CFU/g and stored under conditions simulating reasonably foreseeable refrigerated storage (7 °C for approximately two-thirds of their shelf life, followed by 10 °C for the remaining one-third), in accordance with ISO 20976-1 and EURL L. monocytogenes guidelines. The growth potential (Δ) was calculated as the difference between the highest mean L. monocytogenes concentration observed during storage and the mean of the initial concentration at time zero, both in three replicate samples; Δmax was defined as the highest Δ value among the tested batches. Crispy lettuce, baby lettuce, and the mixed salad supported the growth of L. monocytogenes, with Δmax values of 2.33, 2.60, and 3.65 log CFU/g, respectively. In contrast, both mâche products showed Δmax values ≤ 0.5 log CFU/g, indicating an inability to support pathogen growth under the tested conditions. These results demonstrate that the growth potential of L. monocytogenes in RTE salads is strongly product-specific and likely influenced by intrinsic characteristics and background microbiota, as well as by storage temperature. The findings underline the importance of strict temperature control and product-specific risk assessment to ensure compliance with microbiological criteria throughout shelf life and to mitigate the risk of listeriosis associated with RTE salads. Full article

Efficient heat recuperation is one of the most critical factors influencing the performance of mixed-refrigerant Joule–Thomson (MR JT) cryocoolers. This becomes even more significant in precooled systems, which enhance overall performance but simultaneously intensify the challenges associated with recuperation effectiveness. Modeling the recuperation process is inherently complex because it involves gaseous, liquid, and two-phase flow regimes. Furthermore, the use of mixed refrigerants introduces additional complexity in predicting thermo-hydraulic properties. Experimental validation of modeling results is also highly demanding, particularly with respect to determining the mixed-refrigerant composition, which may differ substantially from the initially charged proportions during operation. This paper presents a comprehensive modeling approach for the complete two-phase recuperative heat transfer process. In total, 96 combinations of heat transfer correlations were evaluated. The modeling results were compared with experimental data obtained using a novel, validated, noninvasive, continuous method for determining refrigerant composition. Such an approach, including analysis of the impact of MR composition uncertainty on the results, has not been performed in previous, similar studies. The optimal set of correlations was identified, yielding a mean average error of 20.16K without composition correction (when applying a composition correction of 13.67K). The validated modeling approach provides valuable insight into heat transfer phenomena occurring in the recuperation section of MR JT cryocoolers and other mixed-refrigerant-based systems. Full article

Energy management systems operating under dynamic electricity pricing require fast and cost-optimal control strategies for flexible loads. Mixed-integer linear programming (MILP) can compute theoretically optimal control trajectories but is computationally expensive and typically relies on accurate load forecasts, limiting its practical real-time applicability. This paper proposes a supervised imitation learning (IL) framework that learns optimal setpoint trajectories for a conventional proportional (P) controller directly from electricity price signals and temporal features, thereby eliminating the need for explicit load forecasting. The learned model predicts setpoint trajectories in an open-loop manner, while a lower-level P controller ensures stable closed-loop operation within a two-stage control architecture. The approach is validated in an industrial case study involving load shifting of a refrigeration system under dynamic electricity pricing and benchmarked against MILP optimization, reinforcement learning (RL), heuristic strategies, and various machine learning models. The MILP solution achieves a cost reduction of 21.07% and represents a theoretical upper bound under perfect information. The proposed Transformer model closely approximates this optimum, achieving 19.33% cost reduction while enabling real-time inference. Overall, the results demonstrate that the proposed supervised IL approach can achieve near-optimal control performance with substantially reduced computational effort for real-time energy management applications. Full article

This study evaluated Salmonella behavior during Sardinian fermented sausage (SFS) production through a challenge test on experimentally inoculated raw meat. The objectives were to (i) determine the survival and reduction kinetics of Salmonella during fermentation and ripening and (ii) evaluate the relationship between pathogen behavior and the evolution of key chemical-physical parameters (pH, water activity). Three batches of SFS were produced, and the meat mixture was inoculated with a three-strain Salmonella cocktail (reference and field strains) to 10² CFU/g. After 20 days of ripening, sausages were vacuum-packed and stored under refrigerated conditions (+4 ± 2 °C). For each batch, triplicate samples were collected and analyzed at different production stages (mixing, after overnight rest, and 24 h after stuffing) and during shelf life (days 6, 21, 30, and 40). Analyses included Salmonella detection and enumeration by direct plating, aerobic colony count, Enterobacteriaceae, staphylococci, lactic acid bacteria, molds and yeasts, as well as pH, water activity, and gross composition. Salmonella counts increased by approximately one log unit after stuffing, before the onset of acidification. During fermentation and ripening, pathogen levels declined but remained detectable, even after prolonged refrigerated storage. These findings indicate that although ripening, and particularly fermentation, significantly (p < 0.05) reduce Salmonella levels, complete inactivation is not achieved. The study highlights the importance of controlling initial contamination levels, validating fermentation and ripening conditions, and the application of additional post-process hurdles to ensure product safety. Full article

Variable geometry ejectors (VGEs) offer passive, compact, and energy-efficient solutions for fluid transport and thermal management in applications such as refrigeration, hydrogen fuel cells, and solar-driven desalination. By adjusting internal geometries, VGEs maintain high performance under off-design and transient conditions, overcoming limitations of fixed-geometry ejectors. This systematic review synthesizes experimental, numerical, and hybrid research on VGEs published between 30 June 1995 and 1 July 2025. Peer-reviewed journal and conference papers were identified through structured searches of Scopus, Web of Science, and Google Scholar, followed by PRISMA-guided screening. Forty-eight studies were qualitatively synthesized with respect to modulation mechanisms, actuation and control strategies, working fluids, modeling approaches, validation practices, performance metrics, and Technology Readiness Levels (TRLs). Risk of bias was assessed using the Mixed Methods Appraisal Tool (MMAT), complemented by an engineering-specific extension for experimental and numerical studies. Results indicate a strong reliance on numerical modeling, predominantly 2D axisymmetric CFD, with limited high-fidelity experimental validation. Adjustable nozzle throats dominate current designs, while multi-variable geometries and real-time closed-loop control remain underexplored. Most studies cluster at TRLs 2–4, with only two demonstrating full system-level integration. Overall, VGEs show strong potential for energy-efficient operation, but progress toward deployment requires integrated geometry–control co-design, standardized benchmarking, uncertainty-aware validation, and scalable experimental demonstration. This review was not registered. Full article

Vapour-compression refrigeration and cooling systems represent a significant share of global electricity consumption, being estimated to account for approximately 10% to 20% of the worldwide electricity demand, which highlights their critical impact on energy efficiency and sustainability. In this context, improving the thermodynamic and exergoeconomic performance of refrigeration cycles, as well as the appropriate selection of the refrigerant, has become a key research priority. Therefore, this work aims to comparatively evaluate the energy, exergy, exergy cost, and exergoeconomic performance of three vapour-compression refrigeration cycle configurations: a simple cycle, a two-stage cycle with a flash tank, and a two-stage cycle with a flash tank and a mixing chamber. Six refrigerants (R134a, R600a, R290, R1234yf, R1234ze (E), and R717) were analysed under evaporation temperatures of 228–238 K and condensation temperatures of 298–308 K. The performance evaluation was carried out using the Fuel–Product–Residue (FPR) methodology, considering the coefficient of performance (COP), exergy efficiency, system irreversibilities, and exergy and exergoeconomic costs. The results indicate that the incorporation of the mixing chamber increases the COP by up to 7% and the exergy efficiency by up to 6% compared to the simple cycle, while reducing exergoeconomic costs by up to 10% for the most favourable refrigerants. Among the working fluids analysed, R600a exhibits the best overall performance (COP up to 4.3 and an exergy efficiency of 33%), followed by R290 and R717, whereas R1234yf shows the lowest efficiencies (COP ≈ 3.7 and exergy efficiency ≈ 28%) and the highest exergoeconomic costs. These findings demonstrate that the design of vapour-compression refrigeration systems should involve the joint selection of the cycle configuration and the refrigerant based on integrated energy, exergy, and exergoeconomic criteria. Overall, the results highlight that both the refrigerant and the cycle configuration must be selected simultaneously, considering energy, exergy, and exergoeconomic criteria, to achieve more efficient and sustainable industrial applications. Full article

Ensuring product integrity across Malaysia’s East Malaysian states (Sabah and Sarawak) requires a cold chain that is resilient to tropical heat, long multimodal routes, intermittent power, and dispersed rural populations. This paper proposes a sustainability-first architecture for vaccine and blood component logistics that combines World Health Organization and the United Nations International Children’s Emergency Fund Effective Vaccine Management (EVM 2.0) criteria with energy-aware transport planning, solar-hybrid edge refrigeration, phase-change materials, and digital temperature monitoring compliant with ISO 23412 for temperature-controlled delivery services. In this study, a mixed-methods methodology was employed, including (1) route and mode optimization under temperature risk and carbon intensity constraints; (2) equipment right-sizing using duty-cycle energy models and IEC 60068 environmental tests as design baselines; (3) governance with real-time earned value management (EVM) and key performance indicators (KPIs); and (4) scenario analysis for riverine, road, air, and drone last-mile segments relevant to remote East Malaysian communities. Results from realistic logistic scenarios indicate a 45–65% reduction in dose-weighted temperature-excursion minutes, 28–41% reduction in CO₂e per successful dose delivered, and 35–52% reduction in product loss compared with status quo planning. For blood components, solar-hybrid storage and mixed-mode routing reduced breach risk by 37% while maintaining red cells (2–6 °C), platelets (20–24 °C, continuous agitation surrogate), and fresh frozen plasma (≤−18 °C) requirements aligned with WHO guidance and Malaysia’s national transfusion policies. We provide a reference architecture, implementation bill of materials, and an EVM-aligned KPI dashboard to guide scale-up. Full article

With rising customer demands for the timeliness and quality of refrigerated goods, the efficiency and fluidity of cold chain logistics remain inadequate, resulting in a notable imbalance between supply and demand in the cold chain market. To reduce the damage of fresh produce and lower logistics costs, this paper introduces multimodal transportation into the cold chain market and performs an analysis of optimizing multimodal transportation routes for refrigerated goods. This study constructs a mixed-integer programming model for cold chain multimodal transportation, aiming to minimize total costs while considering carbon emissions and uncertain demand. An improved adaptive large neighborhood search (ALNS) algorithm is developed to solve the mathematical model, featuring improved adaptive scoring and operator selection mechanisms. The algorithm’s performance is validated through a real-world multimodal transportation network in China. Furthermore, a sensitivity analysis is performed on rail freight rates, confidence levels, and ambient temperature, from which we derive managerial insights with practical significance. Full article

Background/Objectives: Cold-smoked salmon (CSS) is a ready-to-eat product with minimal preservation hurdles and a microbiota shaped by raw-material contamination and processing environments. Short breaks in refrigeration commonly occur during shopping and transport, yet their microbiological impact remains unclear. Here, we used ASV-resolved 16S rRNA gene metataxonomics to characterize storage-driven microbiota dynamics in CSS—quantifying ASV-level genetic diversity and phylogeny-aware (UniFrac) community structure—and to evaluate the effect of a brief, consumer-mimicking 2 h room-temperature cold-chain disruption. Methods: Three CSS types (organic, conventional Norwegian, and conventional Scottish) were stored at 5 °C for 35 days. On day 16, half of each batch was exposed to 2 h at room temperature (RT) before analysis; paired controls remained refrigerated. Culture-based counts (total mesophiles, lactic acid bacteria, Photobacterium spp.; indicator/pathogen screens) were performed per ISO methods. Community profiling used 16S rRNA (V3–V4) amplicon sequencing with QIIME 2/DADA2 and SILVA taxonomy. Linear mixed effects modelled alpha diversity; beta diversity by PERMANOVA on UniFrac distances; differential abundance by ANCOM-BC. Results: ASV-resolved 16S rRNA gene profiles of CSS were dominated by Pseudomonadota and Bacillota, with storage-driven shifts and taxon-specific trajectories (e.g., increasing Latilactobacillus). Both time and product type significantly explained phylogeny-aware community structure (unweighted and weighted UniFrac), consistent with storage-driven phylogenetic convergence across products. At day 16, ASV-level genetic diversity (Shannon/Observed features) and genus-level composition did not differ between RT-disrupted and continuously refrigerated samples. Culture-dependent counts increased from baseline to day 16 and largely plateaued by day 35, with lactic acid bacteria in Norwegian CSS continuing to rise; no systematic effect of the 2 h RT exposure was observed in culture-based comparisons. Indicator/pathogen screens detected no unexpected pathogenic species throughout the study period. Conclusions: Refrigerated storage drives pronounced, phylogeny-aware microbiota shifts and cross-product convergence in cold-smoked salmon, whereas a single 2 h RT interruption at mid-storage did not measurably alter ASV-level genetic diversity or community structure under the tested conditions. Integrating culture-based enumeration with ASV-resolved 16S rRNA gene metataxonomics provides complementary insights for shelf-life evaluation and risk assessment in ready-to-eat seafood. Full article

The use of mixed cow–goat milk in yogurt production allows for balancing fermentation performance, textural properties and sensory attributes of the products. This study evaluated the fermentation behavior and physicochemical, microbiological, textural, and color properties of yogurts produced from cow milk (A), goat milk (E), and mixed cow–goat milk at volume ratios (v/v) of 75:25 (B), 50:50 (C), and 25:75 (D). Volatile organic compounds (VOCs) were analyzed in milk before fermentation and in yogurts after production and during two weeks of refrigerated storage. Sensory attributes were assessed after two weeks of storage. An increase in the proportion of goat milk in the milk blend shortened the fermentation time, whereas a higher proportion of cow milk enhanced the survival of lactic acid bacteria (LAB), improved water-holding capacity (WHC), strengthened textural properties, and reduced syneresis. Yogurts with higher proportions of goat milk exhibited increased lightness and whiteness. Milk type influenced chemical composition, with higher fat content and lower lactose content observed in goat milk yogurts. A higher proportion of goat milk in the milk blend promoted the formation of methyl ketones and aldehydes associated with a characteristic fatty aroma. Among the mixed-milk yogurts, the sample containing 25% goat milk (D) achieved the highest sensory acceptance. The study demonstrated that cow–goat mixed-milk yogurts represented a balanced compromise between textural stability, microbial viability, and sensory acceptance. Full article

Mead is a fermented alcoholic beverage obtained through a diluted honey solution and the action of yeasts. Although a potentially probiotic mead obtained by mixed fermentation of Saccharomyces cerevisiae var. boulardii with kombucha has already been proposed in the scientific literature, aspects regarding the shelf life and sensory properties of this product must be evaluated in order to provide further knowledge for its potential market introduction. The present study aimed to evaluate the shelf life and sensory profile of potentially probiotic mead produced by mixed fermentation of S. boulardii and kombucha. The main results showed that the microorganisms in the mead exhibited fermentative metabolic activity, albeit reduced, under refrigerated storage conditions, with a decrease in soluble solids and an increase in alcohol content observed during storage. Mead with S. boulardii and kombucha maintained microbial viability above 6 log CFU/mL for both yeasts and lactic acid bacteria up to 60 days of storage, meeting the minimum recommended count for probiotic foods. For the sensory analysis, mead with S. boulardii and kombucha showed higher acceptance and purchase intention, being characterized by sensory attributes such as carbonated, effervescent, flavorful, honey taste, sweeter, refreshing, and less alcoholic. In conclusion, potentially probiotic mead produced with S. boulardii and kombucha presents a shelf life of 60 days and high sensory acceptability. Full article

Cis-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)) is a highly promising alternative refrigerant, particularly in heat pumps with large temperature lifts. To meet the superheat requirement of R1336mzz(Z), the heat pump system typically requires the installation of an internal heat exchanger, which renders system performance more sensitive to the solubility of the refrigerant in lubricant. Dipentaerythritol ester (DiPEC) is one of the main components of POE lubricants. In this study, the solubilities of R1336mzz(Z) in two DiPECs, dipentaerythritol hexaheptanoate (DiPEC7) and dipentaerythritol isononanoate (DiPEiC9), were measured in the temperature range of 293.15 K–343.15 K. The solubility data were correlated using the non-random two-liquid (NRTL) model; the average absolute relative deviation between this work and values from NRTL model is lower than 2%. In addition, the Henry’s constants of R1336mzz(Z) in DiPEC7 and DiPEiC9 were calculated, and the dissolution potential was compared. Moreover, the mixing thermodynamic properties (such as mixing enthalpy change, mixing entropy change, and mixing Gibbs free energy change) of R1336mzz(Z) dissolving in DiPECs were analyzed. Full article

The increased consumption of ready-to-eat fruits highlights the need for better control of microbial growth during their shelf life. Among bacteria, Staphylococcus aureus and Bacillus cereus are proposed as target species for testing alternative preservative methods. This study aimed to evaluate the antimicrobial effect of the cell-free supernatant (CFS) from LAB strains previously isolated from ready-to-eat fruits, used as a mixed solution, against both reference and native S. aureus and B. cereus, which were isolated from commercial ready-to-eat fruits. A specific challenge test was conducted on minimally processed orange slices, assessing the effect of CFS on the intentionally inoculated target bacteria using a culturing and quantitative PCR (qPCR) approach. Microbiological counts varied widely among samples, indicating an initial microbiota below legislative limits, mainly comprising total mesophilic and psychrophilic bacteria, which increased significantly after 8 days of storage. Additionally, our results demonstrated the food matrix’s capacity to support the growth of both target species, with the tested CFS mainly effective in reducing the growth of reference strains. The results of the physicochemical analyses showed that during refrigerated storage, the orange slices underwent changes in pH, color, and texture, mostly in S. aureus strain-inoculated samples, negatively affecting texture at mid-storage time. The study also underscored the importance of combining plate counting with qPCR methods to detect B. cereus, as it can be risky even at low levels. Full article

Due to the increase in global energy demand, as well as environmental concerns, hydrogen presents itself as a promising energy source. Liquid hydrogen is more suited for long-distance transportation, but hydrogen liquefaction is an energy-intensive process, and many studies have been published proposing more efficient liquefaction cycles. In this study, simple hydrogen liquefaction cycles like Claude, pre-cooled Linde–Hampson (PLH), single mixed refrigerant (SMR), and dual mixed refrigerant (DMR) were assessed regarding the influence of the cycle’s high pressure on energy efficiency, exergy destruction, and its distribution along the equipment. Among the main results, Claude presented the best specific energy consumption (SEC) of 16.47 kWh/kg_LH, followed by DMR with an SEC of 17.30 kWh/kg_LH, SMR with 17.58 kWh/kg_LH, and finally PLH, with an SEC of 45.07 kWh/kg_LH. The exergy efficiency followed the same pattern as the SEC, with Claude having the lowest exergy destruction, followed by DMR and SMR with close exergy destruction, and finally PLH. Nonetheless, although cycles were not optimized in evaluating the effect of increasing the high pressure, which constrains the direct applicability of the result found, especially in the pre-cooled cycles, the analysis provides valuable insights into the sensitivity of cycle performance. The method and its findings provide the basis for further studies, including optimization steps. Full article

Ready-to-eat products, such as mixed-cut leafy vegetables, require packaging that provides adequate mechanical protection, a barrier against UV radiation, gases, and water vapor, as well as microbiological safety. In this study, thin films made of polybutylene succinate (PBS) and poly (butylene succinate-dilinoleic succinate) (PBS-DLS) copolyester were prepared by casting a film-forming solution onto a glass plate and spreading it with a roller. These films were compared to commercial thin films made of oriented polypropylene (OPP). OPP films exhibited ten times higher tensile strength than PBS films (104.36 ± 10.03 MPa for OPP, 10.96 ± 0.68 MPa for PBS, and 6.36 ± 0.62 MPa for PBS-DLS). Incorporation of co-monomeric units of dilinoleic succinate (DLS) into PBS structure significantly improved elongation at break, increasing from 38.16% ± 12.36% for PBS to 132.30% ± 25.08% for PBS-DLS. However, commercial OPP had the highest elongation at break, reaching 231.84% ± 20.30%. OPP films exhibited the highest transparency in the visible light range but also in the UV range. In contrast, PBS and PBS-DLS films provided better UV radiation blocking. The films were used to create sachets by heat sealing, into which freshly cut chicory leaves were placed. The packaged product was stored under refrigerated conditions for 48 h and 120 h. While OPP and PBS-DLS films provided good protection against moisture loss in chicory, leaves packed in PBS sachets lost significant weight during storage. The packaged product contained considerable microbial contamination, but the type of packaging did not influence its reduction or increase. Ultimately, the PBS-DLS copolymer exhibited higher elongation at break and greater water vapor barrier properties than PBS. Protection against moisture loss in packaged chicory for PBS-DLS packaging was similar to that for commercial OPP. Despite their weaker mechanical properties, PBS-DLS films appear to be a promising alternative to OPP films for packaging fresh food products. Full article