Analysis of the correlation between mesocarp biomechanics and its cell turgor pressure: A combined FEM-DEM investigation for irrigation-caused tomato cracking.

Fruit mesocarp cracking caused by improper irrigation during development manifests at the macroscale but is ultimately the result of increasing cell turgor pressure at the microscale. Hence, a cell finite element (FE) model including shape, protoplast turgor pressure, and ripening information and a mesocarp tissue block discrete element (DE) model including the features of cell shape and number, were developed to predict the biomechanical correlation between mesocarp and its cell. The validated cell FE model with an internal turgor pressure of 12.9 kPa could reproduce the experimental force-deformation behavior of a single cell in compression up to 11% deformation with an average relative error of 5.8%. The validated mesocarp tissue block DE model could reproduce the experimental force-deformation behavior of a mesocarp block in compression up to 20% deformation with an average relative error of 9.5%. Sensitivity and regression analysis showed that turgor pressure was the most important factor affecting cell biomechanics, followed by cell shape and wall elastic modulus. Similarly, the apparent elastic modulus of the cells has the most significant effect on the mesocarp tissue biomechanics, followed by the number and shape of cells. Finally, a mathematical model was obtained to quantitatively describe the relationship between the elastic modulus of the mesocarp and its cell turgor pressure. This study contributes to a better understanding of the biomechanical mechanisms of irrigation-caused tomato fruit cracking at the cellular level and the development of strategies to prevent fruit cracking through a combination of gene breeding and irrigation management.

Changes in Volatile Composition of Cape Hake Fillets under Modified Atmosphere Packaging Systems during Cold Storage.

Fresh ready-to-cook fish fillets are susceptible to loss of freshness and accumulation of off-odour due to accelerated microbial spoilage. Suboptimal storage temperature and packaging conditions accelerate this process, limiting the economic potential. This study investigated the effects of modified atmosphere packaging (MAP) and storage temperature (0 °C and 4 °C) on the volatile compounds (VOCs) of Cape hake (Merluccius capensis) fish fillets as a predictor of shelf life and quality. Fresh Cape hake fillets were packaged under active modified atmosphere (40% CO2 + 30% O2 + 30% N2) and passive modified atmosphere (0.039% CO2 + 20.95% O2 + 78% N2) with or without an absorbent pad and stored at 0 °C and 4 °C for 12 d. The results obtained demonstrated that changes in VOCs and concentration were significantly (p < 0.05) influenced by MAP conditions, storage temperature and duration. A total of 16 volatiles were identified in the packaged Cape hake fillets: 4 primary VOCs and 12 secondary VOCs. The spoilage VOCs identified include tri-methylamine (TMA) (ammonia-like), esters (sickeningly sweet) and sulphur group (putrid). The concentration of secondary VOCs increased continuously during storage. Active-MA-packaged fillets performed better and had lower TMA values of 0.31% at 0 °C on day 12 in comparison to 7.22% at 0 °C under passive on day 6. Ethyl acetate was detected in passive-MA-packaged fillets stored at 0 °C on day 3, and the levels increased to 3.26% on day 6, while active-MA-packaged fillets maintained freshness. This study showed that in conjunction with TMA, VOCs such as esters and sulphur-related compounds could be used as spoilage markers for Cape hake fish fillets.

Textural thermo-mechanical properties of sweet cherry for postharvest damage analysis.

In this study, the textural thermo-mechanical properties of three sweet cherry varieties were systematically investigated by the puncture test of whole fruit, uniaxial tension of the exocarp, and uniaxial compression test of mesocarp. It was found that the puncture test can not only reflect the shear mechanics of the exocarp in vivo at the tissue level, but it can also characterize the resistance level of fruit to puncture damage at the macroscopic level, particularly when the puncture failure stress is used. The environmental temperature had negative and positive significant effects on the puncture failure stress and the puncture failure deformation of the sweet cherry (p < .05), respectively. The environmental temperature showed a negative significant effect on the failure stress and elastic modulus of the sweet cherry exocarp under tension and mesocarp under compression (p < .05). As the environmental temperature increased from 5 to 40°C, the elastic modulus of the Black pearl, Summit, and Tieton sweet cherry exocarp ranged from 2.28 to 1.72, 2.57 to 1.47, and 1.98 to 1.24 MPa, respectively; and that of mesocarp ranged from 0.33 to 0.21, 0.27 to 0.19, and 0.43 to 0.23 MPa, respectively. The obtained exponential function relationships between environmental temperature and each mechanical parameter are useful for predicting the thermo-mechanical properties of sweet cherry across a 5-40°C continuous temperature range. This study provided systematical thermo-mechanical data for predicting the mechanical damage of sweet cherry in postharvest handling using the thermo-mechanical coupling numerical simulation.

Effect of gum Arabic and ethanol pretreatments on drying kinetics and quality attributes of dried carrot slices.

Carrot is an important root vegetable to the food industry and consumers due to its nutritional and health benefits. Given the high moisture content and low shelf life of fresh carrots, preserving this highly demanded vegetable is vital. This current research modelled the drying kinetics and evaluated the quality of ultrasonic-assisted gum Arabic and ethanol pretreated and oven-dried carrot slices. Fresh carrots were processed into thin slices and immersed in 3% gum Arabic (GA), ethanol (99.9%), and distilled water (control), followed by ultrasonication (frequency: 50 Hz, power: 500 W, temperature: 25 °C) for 10 min and drying in a hot air oven at 50 °C. The loss of moisture from the carrots was periodically recorded, converted to moisture ratio before fitted to eleven semi-theoretical thin layer drying mathematical models. The effects of the pretreatments on the retention of bioactive compounds and carrots' physical and chemical properties were also evaluated. From the tested models, the Diffusion, Modified Henderson and Pabis, and Two-term models showed the best fitting (R2 = 0.9944-0.9985; RSME = 0.0103-0.0227) to the experimental data from 3% GA and ethanol pretreated carrots, while control samples followed the Aghbasho model (R2 = 0.9999; RMSE = 0.0033). Overall, the 3% GA pretreated carrot slices exhibited better colour (yellowness: 25.82-34.50; total colour differences: 8.12-13.06), water activity (0.37-0.44), total phenolic content (1.34-2.99 mg GAE/100 g DM), ß-carotene (7.63-13.07 mg/100 g DM), and DPPH radical scavenging activity (5.67-8.02 mM AAE/100 g DM) than ethanol pretreated carrot slices and control samples. At the same time, 3 % GA pretreatment did not affect the drying rate of the carrot slices. The total soluble solids/titratable acidity ratio, rehydration capacity, and shrinkage ratio did not significantly (p > 0.05) vary among the treatments. The findings of this study can be used to develop an optimal drying protocol for pretreated carrot slices and to produce shelf-stable carrot products that can be used dried, rehydrated, or in combination with other products.

Thermo-Mechanical Analysis in the Fresh Fruit Cold Chain: A Review on Recent Advances.

In agro-food research and industry, mathematical models are being used to develop and optimize preharvest and postharvest operations, and their use has grown exponentially over the last decade. Generally, transport phenomena (such as airflow, heat, and mass transfer) during the cooling of horticultural products are complex; therefore, the use of computational modeling techniques is a valid alternative to expensive and difficult experiments because computers continuously become more powerful and less expensive, the software is readily available, and once a model is validated, it is a versatile tool to evaluate the effects of the operating and design parameters involved. In this review, thermo-mechanical modeling studies during postharvest handling are overviewed regarding the experimental, analytical, and computational approaches. The airflow, cooling kinetics, cooling uniformity, and the material and mechanical safety behavior of fresh fruit packaging boxes will be analyzed. Current concerns, challenges, and opportunities are discussed.

Finite Element Method for Freezing and Thawing Industrial Food Processes.

Freezing is a well-established preservation method used to maintain the freshness of perishable food products during storage, transportation and retail distribution; however, food freezing is a complex process involving simultaneous heat and mass transfer and a progression of physical and chemical changes. This could affect the quality of the frozen product and increase the percentage of drip loss (loss in flavor and sensory properties) during thawing. Numerical modeling can be used to monitor and control quality changes during the freezing and thawing processes. This technique provides accurate predictions and visual information that could greatly improve quality control and be used to develop advanced cold storage and transport technologies. Finite element modeling (FEM) has become a widely applied numerical tool in industrial food applications, particularly in freezing and thawing processes. We review the recent studies on applying FEM in the food industry, emphasizing the freezing and thawing processes. Challenges and problems in these two main parts of the food industry are also discussed. To control ice crystallization and avoid cellular structure damage during freezing, including physicochemical and microbiological changes occurring during thawing, both traditional and novel technologies applied to freezing and thawing need to be optimized. Mere experimental designs cannot elucidate the optimum freezing, frozen storage, and thawing conditions. Moreover, these experimental procedures can be expensive and time-consuming. This review demonstrates that the FEM technique helps solve mass and heat transfer equations for any geometry and boundary conditions. This study offers promising insight into the use of FEM for the accurate prediction of key information pertaining to food processes.