Search Results (74)

To address the reliability requirements for refrigerated container transport in the cold chain, this study established an experimental platform for phase change cold storage balls. A two-dimensional axisymmetric simplified heat transfer model of the three-dimensional cold storage ball was developed. The reliability of the model was verified through charging experiments. While ensuring a certain level of accuracy (average error less than 10%), the model significantly improved computational efficiency (completing calculations in only 49 s), offering a practical reference value. Based on the established 2D axisymmetric simplified heat transfer model, this study focused on the influence of secondary coolant (ethylene glycol solution) parameters on the charging performance. The results indicate that a smaller diameter of the cold storage ball and a higher flow rate lead to a higher freezing rate of the ball. Under the conditions set in this study, the optimal diameters were determined to be 80 mm and 60 mm, and the optimal inlet flow rate was 3.917 m³/h. This simplified model can provide a reference for the optimal design of phase change cold storage systems in refrigerated containers. Full article

Public concerns about the health risks of synthetic antioxidants have prompted the meat industry to look for natural alternatives rich in phenols with strong antioxidant properties. This study investigates the use of blackcurrant (BCP), lingonberry (LP), and sour cherry (SCP) powders as natural substitutes for synthetic nitrites in reformulating two clean-label salami types, smoked and cooked and smoked and scalded, with a focus on their effects on oxidative stability during processing and refrigerated storage (4 °C). Nitrite-free formulations were prepared with each fruit powder at three inclusion levels to provide total phenolic contents of 90, 200, and 300 mg gallic acid equivalents (GAE)/kg of processed meat. A nitrite-containing control (90 mg/kg) and an additive-free control were included for comparison. The phytochemical profiles of powders were characterized by total phenolic, flavonoid, monomeric anthocyanin contents, and L-ascorbic acid levels. Antioxidant activity was assessed via 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. Salami samples were analyzed for proximate composition, and lipid oxidation was monitored at 0, 15, and 30 days of storage using peroxide value, inhibition of oxidation, p-anisidine value, TOTOX, and thiobarbituric acid value. Fruit powders demonstrated dose- and type-dependent inhibition of primary and secondary lipid oxidation, enhancing oxidative stability during processing and storage. After 30 days of storage, oxidation markers in fruit-enriched salami remained below recommended thresholds, confirming effective control of lipid oxidation. The inhibitory potential followed the order BCP > LP > SCP, consistent with antioxidant profiles as reflected by DPPH and FRAP values. BCP at 300 mg GAE/kg showed a stronger lipid oxidation inhibition than sodium nitrite. Promising improvements in lipid oxidation resistance were also observed with LP at 300 mg GAE/kg and BCP at 200 mg GAE/kg. These findings highlight the potential of fruit-derived antioxidants to support the development of more sustainable, value-added meat products without compromising quality. Full article

Consumer demand for plant-based functional foods, especially probiotic beverages, has increased due to their health benefits and suitability as dairy-free alternatives. This study assessed, through a factorial combination, the stability of plant-based extracts (avocado, ginger, and tropical) individually inoculated with three commercial Lactobacillus strains (L. casei, L. plantarum, L. reuteri) and stored under refrigerated conditions during both primary (PSL) and secondary shelf life (SSL). Product shelf life was defined by probiotic viability, considering the functional threshold (≥6 log CFU/mL), which was maintained across all formulations throughout the storage period. Physicochemical parameters, including pH, titratable acidity, and colour, as well as volatile profile, remained stable, with only minor variations depending on the matrix and bacterial strain. Sensory evaluations (triangle and acceptability tests) confirmed that the probiotic juices were acceptable to consumers. Overall, the results demonstrate the feasibility of producing non-fermented, plant-based probiotic beverages that retain their functional properties and meet consumer sensory expectations, offering a promising alternative for vegan and lactose-intolerant individuals. Full article

Freezing has been widely used to preserve the freshness and quality of crayfish (Procambarus clarkii). However, temperature fluctuations during transportation and storage inevitably affect the quality attributes of crayfish. In this study, the effect of liquid nitrogen freezing (LNF) on crayfish myofibrillar protein (MP) was investigated under freeze–thaw (FT) cycles. The small ice crystals formed by LNF could reduce the conversion of sulfhydryl groups to disulfide bonds, preventing the exposure of hydrophobic groups, thereby maintaining the functional properties of MP. LNF could prevent the degradation and oxidation of MP and maintain its compact and smooth microstructure. Compared to refrigerator freezing (RF), LNF showed a stronger protective effect on the secondary and tertiary structures of MP, alleviating their conformational changes. Therefore, LNF could be an alternative freezing method to preserve crayfish quality against FT cycles during transportation and storage. Full article

The thermally driven ejector refrigeration system is generally used to recover industrial waste heat to improve the energy efficiency of industrial processes. However, for conventional single-stage ejector refrigeration systems (ERSs), the higher-pressure steam derived from high-temperature waste heat elevates the primary fluid pressure, resulting in significant pressure mismatch with the secondary fluid, which consequently leads to large irreversible losses and substantial degradation in system performance. To address this issue, a novel hybrid ejector refrigeration system (NHERS) is proposed and analyzed under design and off-design conditions using thermodynamics. The results indicate that under design conditions, compared to the conventional single-stage ejector refrigeration system, the proposed hybrid ejector refrigeration system can achieve increases of about 20.6% in the entrainment ratio, around 15.2% in the coefficient of performance (COP), and about 21.4% in exergetic efficiency. Analyzing its performance under off-design conditions to provide technical solutions for the flexible operation of the hybrid ejector refrigeration system proposed in this paper can broaden its application scenarios. Consequently, the proposed NHERS demonstrates remarkable superiority in energy conversion and transfer processes, showing certain application prospects in the field of medium- to high-temperature industrial waste heat recovery. Full article

A new evaporative condensation refrigerant pump heat pipe air-conditioning unit based on a microchannel heat pipe heat exchanger is proposed. Performance experiments were conducted on the unit, and the experimental results show that the cooling capacity of the unit in the dry, wet, and mixed modes can reach 112.1, 105.8, and 115.4 kW, respectively, the optimal airflow ratio of the secondary/primary airflow is 2.2, 1.8, and 1.8, respectively, and the EER decreases with increasing airflow ratio. With increasing dry- and wet-bulb temperatures of the secondary-side inlet air, the cooling capacity and energy efficiency ratio of the unit decrease, and the energy efficiency ratio in the wet mode is higher than that in the dry mode, which can prolong the operating hours of the wet mode within the operating temperature range of the dry mode and improve the energy efficiency of the unit. A new calculation method for the refrigerant charge is proposed, and the optimal refrigerant charge is 32 kg based on the experimental results, which agrees with the theoretical calculation results. Full article

Background: Red macroalgal flour resulting from commercial phycocolloid extraction has been shown to include valuable preservative compounds. Methods: This study focused on the preservative effect of a gelatin-based packaging system including Gelidium sp. flour during refrigerated storage of Trachurus trachurus fillets. Different microbial and chemical indices related to quality loss were determined in fish muscle during a 6-day storage period at 4 °C. Results: Compared with gelatin-packaged control samples, those packaged in the system including the algal flour presented significantly lower microbial development (aerobic bacteria, psychrotrophic bacteria, and proteolytic bacteria) and significantly lower chemical indices related to microbial development (pH and trimethylamine). With respect to lipid oxidation, there was significantly greater retention of peroxides and significantly lower formation of secondary oxidation products in the samples packaged with the algal flour. Additionally, the algal flour group presented significantly less lipid hydrolysis. Conclusions: A preservative effect was derived from the addition of Gelidium flour to a gelatin-based packaging system during refrigerated storage of T. trachurus. This study supports the practical and valuable use of Gelidium sp. flour and addresses the current global interest in natural sources of preservative compounds and the use of marine byproducts. Full article

With a prolonged refrigeration time, dough becomes syruped and the gluten strength is weakened, which negatively affects the texture of the dough. At the same time, differences in the growth and metabolism of different yeasts lead to large differences in the physicochemical properties of the dough and the final quality of the product. Therefore, in this study, suitable additives and non-Saccharomyces cerevisiae were selected to minimize the effects of long-term refrigeration on the physicochemical properties and microstructure of fermented doughs. Compared to the control group without mixed yeast strains and additives, the fermentation properties, textural properties, dynamic rheology, starch crystallinity, protein structure, water distribution, and microstructure were investigated by mixed yeast strains and additives for 14 days of long-term refrigeration. The results showed that using mixed yeast strains (Saccharomyces cerevisiae: Metschnikowia pulcherrima; Wickerhamomyces anomalous = 0.46:0.27:0.27), α-amylase, diacetyl tartaric acid ester of mono(di)glycerides and polydextrose can avoid the excessive fermentation of refrigerated dough. In addition, mixed yeast strains and additives could maintain the orderliness of the secondary structure of gluten proteins, stabilize the microstructure of starch and gluten proteins, and reduce the migration and loss of water in the dough. This study clarified that mixed yeast strains and additives are conducive to prolonging the long-term refrigeration of dough, and could better maintain the quality of dough during long-term refrigeration. These results provide a theoretical basis for further research on the large-scale production of refrigerated fermented dough. Full article

In the production of meat products, animal fats, which are rich mainly in saturated fatty acids, are used as a recipe ingredient. To improve the quality and fatty acid profile of meat products, it is possible to partially replace animal fat with vegetable oils. This approach aims to achieve a more favorable PUFA/SFA ratio and n-6:n-3 PUFA ratio, bringing them closer to the values recommended by nutritional organizations. Therefore, the aim of this study was to determine the impact of replacing 20% and 40% of animal fat with selected plant fats on the change in the fat fraction composition of liver pâté-type processed meat and its oxidative stability. Fatty acid content was analyzed in the oils purchased from retailers and in experimental samples. During refrigerated storage of the experimental sausages, changes in the content of primary (peroxide value (PV)) and secondary oxidation products (TBARS), as well as changes in sensory quality, were evaluated. The analysis included cross-sectional color, aroma, texture, saltiness, and taste. The study showed that replacing 20% of animal fat with vegetable oils resulted in products with high sensory attractiveness and oxidative stability, outperforming those with 40% replacement. Among the tested vegetable oils, samples with rapeseed oil demonstrated the highest oxidative stability and the most favorable, nutrition-recommendation-approaching n-6 to n-3 fatty acid ratio, compared with samples with flaxseed, corn, sunflower, and soybean oils. Full article

Under the background of dual carbon, the retrofitting of the equipment operation system of a refrigeration station and the optimization combination of its control system are significant for its efficient operation and energy saving. The single-direction variable flow technology is often used in the chilled water system in refrigeration stations nowadays. However, the single-direction variable flow technology cannot achieve both thermal balance and flow balance for the chiller system, which is unfavorable for improving energy efficiency and reliability. To improve the reliability and energy efficiency of the refrigeration station equipment, the bidirectional variable flow technology of primary and secondary chilled water pumps was presented. Meanwhile, the feasibility of fuzzy neural networks in bidirectional variable flow systems and their energy-saving effect were studied. Before the energy saving retrofit, the refrigeration station used traditional PID (proportional-integral-derivative) controllers, and the chilled water system used single-direction variable flow technology; After the energy-saving retrofit, the refrigeration station adopted a fuzzy neural network control algorithm to optimize the PID controller parameters, and at the same time, the chilled water system used bidirectional variable flow technology. Through a large number of trial calculations of the established neural network model, it was found that 2 hidden layers and 25 hidden layer nodes can achieve higher accuracy. Specifically, the controller of the central refrigeration station consists of a training neural network and a predictive neural network working in parallel. The task of training neural networks is to learn the relationship between different input parameters and the whole energy consumption. Then it serves as the excitation function of the prediction network. The function of the predictive neural network is to find the control parameters that minimize energy consumption. The application results showed that before and after the retrofit annual power consumption and energy-saving effects were very Significant. After the energy-saving retrofit of the refrigeration station, the energy saving is 422,775 KWh every year, the energy-saving rate is 11.67%, and the annual saving cost is about 0.3382 million yuan. The results demonstrated that bidirectional variable flow technology and its control methods were feasible, reasonable, and worthy of promotion. Full article

The increase in food production is accompanied by an increase in waste, particularly agricultural by-products from cultivation and processing. These residues are referred to as agricultural by-products. To address this issue, biotechnological processes can be used to create new applications for these by-products. This study explored the use of LAB strains (Lactiplantibacillus plantarum, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Limosilactobacillus fermentum) on by-products such as white grape pomace, cocoa bean shells, apple pomace, and defatted roasted hazelnut to develop yoghurt-style fruit beverages. Microbial load and pH changes were monitored during a 24 h fermentation and 14-day shelf life at 5 °C. Concentrations of sugars, organic acids, and volatile organic compounds were also analyzed using HPLC and GC-qMS. The results showed that optimizing the matrix led to significant bacterial growth, with viable microbes remaining under refrigeration. In particular, the strain of L. plantarum tested on the cocoa bean shell yielded the most promising results. After 24 h of fermentation, the strain reached a charge of 9.3 Log CFU/mL, acidifying the substrate to 3.9 and producing 19.00 g/100 g of lactic acid. Aromatic compounds were produced in all trials, without off-flavours, and characteristic fermented food flavours developed. Additionally, secondary metabolites produced by lactic acid bacteria may enhance the health benefits of these beverages. Full article

The study presents the results of an experimental investigation aimed at evaluating the performance of a water-to-water heat pump utilising R1234ze(E) and R515B in a drop-in application. Several operating conditions are tested, varying the mass flow rates and temperatures of the secondary fluids that pass through the heat exchangers while maintaining the compressor shaft rotational frequency and the vapour superheating at the evaporator outlet constant. Overall, when compared to R1234ze(E), the utilisation of R515B results in capacity and COP variations within −6.81% to +2.46% and −2.41% to +6.29%, respectively. Regarding the performance of the compressor, R515B exhibits comparable volumetric and overall efficiency, while a slightly lower refrigerant temperature at the compressor discharge is found, with differences ranging from −3.1 °C to −0.5 °C. Overall, R515B appears to be more suitable than R1234ze(E) for applications in the high-temperature range. Full article

Individuals with spinal cord injury (SCI) experience an increased risk for obesity and cardiometabolic disease. Recommendations to prevent and treat obesity for those with SCI follow those of the US Department of Agriculture to adopt a healthy eating pattern that includes eating a variety of fruits, vegetables, grains, dairy, and protein, plus limiting added sugars, saturated fats, and sodium. Yet, people with SCI eat too many calories, fat, and carbohydrates and too few fruits, vegetables, and whole grains. The study is based on secondary analyses of SCI participants (n = 122) who enrolled in a weight loss study to determine how SCI may impact their ability to prepare food at home. We hypothesize those with higher-level spinal injuries (specifically, those with cervical versus those with thoracic or lumbar/sacral injuries) experience significantly greater difficulty and are more likely to rely on others’ assistance to perform meal preparation tasks. Physiologic (weight, BMI, blood pressure, hemoglobin A1c) and self-reported data (demographic plus responses to the Life Habits Short Survey and meal prep items) were collected at baseline and qualitative data were obtained from a subsample after the intervention during phone interviews. Participants’ average age was 50 ± 14.7 years old, they lived with SCI for an average of 13.0 ± 13.1 years, and their average BMI was 32.0 ± 6.5. Participants were predominantly white (76.1%) men (54.1%) who had some college education (76.3%), though only 28.8% worked. A substantial proportion of respondents (30% to 68%) reported difficulty across the 13 tasks related to purchasing and preparing meals, with a proxy reported as the most common assistance type used across all tasks (17% to 42%). Forty-nine percent reported difficulty preparing simple meals, with 29% reporting a proxy does the task. More than half reported difficulty using the oven and stove, though between 60% to 70% reported no difficulty using other kitchen appliances (e.g., coffee machine, food processor, can opener), the refrigerator, or microwave. There was a significant difference in kitchen function by injury level. Those living with cervical-level injuries had significantly greater limitations than those with thoracic-level injuries. Spouses, other family members, and caregivers were most likely to serve as proxies and these individuals exerted both positive and negative influences on respondents’ dietary intake, based on qualitative data obtained during interviews. The results suggest that many people living with SCI experience functional and environmental barriers that impact their ability to prepare food and use kitchen appliances. Future research should examine how SCI-related functional limitations, transportation access, accessibility of the kitchen, ability to use appliances, availability of financial resources, and assistance by others to prepare foods impact people’s ability to follow a healthy eating pattern. Full article

This study investigates the growth characteristics of Salmonella enteritidis (S. enteritidis) in liquid whole egg under both isothermal and non-isothermal storage conditions to understand the risks associated with inadequate temperature management in the egg industry. Using controlled laboratory simulations, liquid whole egg samples inoculated with S. enteritidis were stored under various isothermal (5, 15, 25, 35, and 45 °C) and non-isothermal conditions (5–10, 15–20, 25–30, 35–40, and 45–50 °C). The growth behavior of the S. enteritidis was analyzed using a two-step predictive modeling approach. First, growth kinetic parameters were estimated using a primary model, and then the effects of temperature on the estimated specific growth rate and lag time were described using a secondary model. Independent growth data under both isothermal and non-isothermal conditions were used to evaluate the models. The results showed that S. enteritidis exhibits different growth characteristics depending on temperature conditions, emphasizing the need for strict temperature control to prevent foodborne illnesses. To address this, a predictive growth model tailored for non-isothermal conditions was developed and validated using experimental data, demonstrating its reliability in predicting S. enteritidis behavior under dynamic temperature scenarios. Additionally, temperature management technologies were proposed and tested to improve food safety during refrigerated storage. This study provides a scientific basis for improving food safety protocols in the egg industry, thereby protecting public health and maintaining consumer confidence amid temperature fluctuations. Full article

Although the R404A indirect refrigeration system (IRS) with an internal heat exchanger (IHX) and R744 as the secondary fluid has potential applications in supermarkets and hypermarkets, the exergy characteristics of this IRS have not been extensively investigated. In this study, the factors affecting the R744 exergy characteristics (degree of subcooling (DSB) and degree of superheating (DSP) of the R404A cycle, DSP of the R744 cycle, condensation temperature (CT) and cascade evaporation temperature (CET), and IHX efficiency) were experimentally evaluated to obtain basic data for the design of R404A IRS with R744 as the optimal secondary fluid. The main results can be summarized as follows: (1) Under given conditions, the smallest change in the system exergy destruction rate (EDR) according to the change in each parameter is the DSP of the R744 cycle (0.3–1%), followed by the DSB of the R404A cycle (6.1–8.8%), the IHX efficiency of the R404A cycle (3.8–14.3%), the DSP of the R404A cycle (11.7–15.9%), the CET (29.4–41.9%), and the CT (35–47%). (2) Also, in terms of the exergy efficiency of system (EES), the largest value was obtained for the DSP of the R404A cycle (2.4–12.7%), followed by the IHX efficiency of the R404A cycle (3–10.2%), the CET (2.2–8.7%), the CT (4–6.9%), the DSB of the R404A cycle (2.7–6.2%), and the DSP of the R744 cycle (0.04–1.2%). (3) In order to lower the system EDR, DSP, DSB, and IHX efficiency of the R404A cycle, the CET must be increased to the maximum, and to lower the DSP of the R744 cycle, the CT must be reduced to the minimum. Full article