Modelling the kinetics of the application process of 1-Methylcyclopropene (1-MCP) as a food preservation method for fruit

Abstract Maintaining quality and delaying over-ripening and senescence are the main goals in handling and storage of fruits and vegetables. Conventionally, control of temperature and humidity and selective use of controlled or modified atmospheres have helped to obtain these goals. Nowadays new methods for delaying postharvest senescence and deterioration of perishable fruits, vegetables, potted plants, and cut flowers are emerging. These include the molecular modification of ripening physiology and the use of compounds that specifically target and inhibit ethylene responsiveness. One of these compounds, 1-methylcyclopropene (1-MCP), has been shown to suppress ethylene responses and extend the postharvest shelf life and quality of numerous fruits and vegetables. Modeling the diffusion and transport of 1-MCP gas in storage rooms for fruits and vegetables may be a potential tool to investigate several situations. Developing such model require knowledge about diffusion and reaction coefficients of 1-MCP gas in the various materials, including the fruit, present in storage rooms. A model governing the diffusion and adsorption behavior of 1-MCP gas in fruits and non target materials found in apple fruit storage rooms is presented. The model is used to estimate kinetics parameters using time-dependent profiles obtained from jar tests on the depletion of 1-MCP gas by samples of wet and dry solid materials. Materials included in the investigation were: Golden delicious apple and bin construction materials [high density polyethylene (HDPE), slightly weathered oak, Poplar wood and cardboard]. The 1-MCP gas diffusion parameters for dry and wet materials were successfully estimated. The model will be used to compute the distribution of 1-MCP in storage rooms and assess the uniformity and dosing of application for different configurations.status: accepte

Model-based design and development of horticultural produce crate from bamboo

AbstractThis study proposes a model-based design and development of ventilated horticultural product crate from bamboo using a validated computational fluid dynamics and finite element analysis models. The models were used to predict the airflow, pressure and temperature distributions, and mechanical integrity of the crate. The model results were validated using experimental results. Results of the newly developed crate were compared to the commonly used conventional wooden crate. The optimal vent area, vent number, and cooling air velocity were found to be 8%, nine vents, and 1.38 m s−1, respectively. Compared to the conventional crate, the improvement in cooling rate, pressure drop, and flow uniformity was 60%, 98%, and 37.9%, respectively. The maximum deformation in the conventional wooden and newly developed crates was 28.483 mm and 0.329 mm, respectively. The results indicate that the newly developed bamboo-based crate has good air ventilation, good cooling, and best in mechanical integrity. We conclude that the improved bamboo crate is a viable alternative to the present post-harvest packaging constraints

Mathematical modelling of blanch-assisted drying of pomegranate (Punica granatum) arils in a hot-air drier

CITATION: Adetoro, A. O., et al. 2020. Mathematical modelling of blanch-assisted drying of pomegranate (Punica granatum) arils in a hot-air drier. Processes, 8(5):611, doi:10.3390/pr8050611.The original publication is available at https://www.mdpi.comPublication of this article was funded by the Stellenbosch University Open Access FundThe effect of blanching conditions on the hot-air drying kinetics of three pomegranates (cvs. “Acco”, “Herskawitz” and “Wonderful”) were assessed. Water blanching conditions considered were 90 °C for 30 s, 90 °C for 60 s, 100 °C for 30 s and 100 °C for 60 s. The drying experiments were carried out at 60 °C, 19.6% relative humidity and at a constant air velocity of 1.0 m s−1. The experimental curves were fitted to seven different drying models. For the Acco cultivar, the drying behaviour was best predicted by the Logarithmic and Page model for blanched (R2 ranging between 0.9966 and 0.9989) and unblanched (R2 = 0.9918) samples, respectively. Furthermore, for the Herskawitz cultivar, Logarithm, Page and Midili models were most suitable for predicting drying behaviour of both blanched and unblanched samples. Also, for the Wonderful cultivar, Logarithm and Midili models were most accurate for predicting the drying behaviour for both blanched and unblanched samples amongst other models. The blanched samples dried faster with shorter drying times: “Acco” (7 h), “Herskawitz” (8 h), and “Wonderful” (7 h), compared to the unblanched samples, which dried after 15, 20 and 11 h, respectively. Effective diffusion coefficient of moisture in pomegranate arils ranged from 4.81 × 10−9 and 1.11 × 10−8 m2 s−1 for the Acco cultivar, for the Herskawitz cultivar; 3.29 × 10−9 and 1.01 × 10−8 m2 s−1 and for the Wonderful cultivar; 5.83 × 10−9 and 1.09 × 10−8 m2 s−1. Overall, blanching resulted in low energy consumption during drying of pomegranate arils. In addition, the Logarithmic model generally showed an appropriate model for blanched samples regardless of cultivar. For unblanched samples, the Page model was more appropriate for “Acco” and “Herskawitz”, while the Midili model was appropriate for “Wonderful”. Therefore, this study provided science-based and practical drying conditions for the investigated pomegranate cultivars.https://www.mdpi.com/2227-9717/8/5/611Publisher's versio

Application of gum arabic and methyl cellulose coatings enriched with thyme oil to maintain quality and extend shelf life of “Acco” pomegranate arils

CITATION: Kawhena, T. G. et al. 2020. Application of gum arabic and methyl cellulose coatings enriched with thyme oil to maintain quality and extend shelf life of “Acco” pomegranate arils. Plants, 9(12):1690, doi:10.3390/plants9121690.The original publication is available at https://www.mdpi.comThe effects of gum arabic (GA; 1.5% w/v) and methyl cellulose (MC; 1% w/v) enriched with thyme oil (TO; 0.25 and 0.5% v/v) on the quality of “Acco” pomegranate arils were studied. Coating treatments, namely, MC, MC + TO0.5%, MC + TO0.25%, GA, GA + TO0.5% and GA + TO0.25% were applied on arils by dipping, and evaluations were made on physicochemical and microbiological quality, phytochemicals and antioxidant capacity of arils stored (5 ± 1 ◦C, 95 ± 2% RH) for 16 days. Dipping arils in GA or MC, both containing TO (0.5% v/v) significantly (p < 0.0001) reduced weight loss and enhanced antioxidant activity (FRAP) (p = 0.0014). However, dipping arils in GA combined with TO (0.25% v/v) had the highest influence on reducing aril respiration rate compared with other treatments. Overall, results showed that application of coatings (GA + TO0.5% and GA + TO0.25%) reduced total yeast and mould and total plate counts and maintained quality up to 8 days of storage. These findings suggest that either GA + TO0.5% or GA + TO0.25% coatings have the capability to extend storage life of “Acco” pomegranate arils.Pomegranate Association of South Africa (POMASA)https://www.mdpi.com/2223-7747/9/12/1690Publisher's versio

Pomegranate Quality Evaluation Using Non-Destructive Approaches: A Review

Pomegranate (Punica granatum L.) is one of the most healthful and popular fruits in the world. The increasing demand for pomegranate has resulted in it being processed into different food products and food supplements. Researchers over the years have shown interest in exploring non-destructive techniques as alternative approaches for quality assessment of the harvest at the on-farm point to the retail level. The approaches of non-destructive techniques are more efficient, inexpensive, faster and yield more accurate results. This paper provides a comprehensive review of recent applications of non-destructive technology for the quality evaluation of pomegranate fruit. Future trends and challenges of using non-destructive techniques for quality evaluation are highlighted in this review paper. Some of the highlighted techniques include computer vision, imaging-based approaches, spectroscopy-based approaches, the electronic nose and the hyperspectral imaging technique. Our findings show that most of the applications are focused on the grading of pomegranate fruit using machine vision systems and the electronic nose. Measurements of total soluble solids (TSS), titratable acidity (TA) and pH as well as other phytochemical quality attributes have also been reported. Value-added products of pomegranate fruit such as fresh-cut and dried arils, pomegranate juice and pomegranate seed oil have been non-destructively investigated for their numerous quality attributes. This information is expected to be useful not only for those in the grower/processing industries but also for other agro-food commodities

Porous medium modeling and parameter sensitivity analysis of 1-MCP distribution in boxes with apple fruit

1-methylcyclopropene (1-MCP) is a gas used commercially in cold storage rooms to delay ripening of fruit. It is currently not known how the gas distributes in the bins and is taken up by the fruit. Here a porous-medium model is developed based on volume averaging of the transport equations of momentum and 1-MCP in the air and product. The proposed model was compared with experimental data and validated direct-CFD model. The velocity field in and around the stack were well reproduced by the porous medium model. Concentration predictions were in average 4% and maximally 7% over the average measured values. The porous medium model also agrees well with the direct-CFD model. Influential model parameters were identified through parameter sensitivity study. Porosity, skin mass transfer coefficient and specific surface area strongly affect the simulation. Accordingly model simplifications were suggested and recommended for commercial cold storage rooms.publisher: Elsevier articletitle: Porous medium modeling and parameter sensitivity analysis of 1-MCP distribution in boxes with apple fruit journaltitle: Journal of Food Engineering articlelink: http://dx.doi.org/10.1016/j.jfoodeng.2013.05.007 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved.status: publishe

Modeling of diffusion-adsorption kinetics of 1-methylcyclopropene (1-mcp) in apple fruit and non-target materials in storage rooms

The purpose of this research was to model the kinetics of adsorption of 1-Methylcyclopropene (1-MCP) in apple fruit and ‘non-target’ solid materials found in apple storage rooms. A distinction is made between diffusion into the material and the adsorption. The process was therefore described by Fick’s second law of diffusion of the gas through the pores of the material coupled with adsorption of the gas on the material’s binding sites. A finite element formulation of the model, describing the diffusion and adsorption mechanisms separately, was first developed. The values of the relevant parameters were estimated based on head space measurements of the decrease of 1-MCP in dedicated jars with the different materials. The diffusion coefficient, adsorption coefficient and concentration of active site in the various solids were determined and were in the order of 10-9m2/s, 101 m3 mol-1s-1 and 10-4 mol m-3 respectively. The model was validated with separate experimental data.The financial support of the Agency for Innovation by Science and Technology (projects IWT 050633 and IWT 060720) is kindly appreciated. These projects received co-funding of the Belgian Fruit and Vegetable Auctions.status: publishe

A CFD study of adapting on-off cooling cycles in apple cold stores for energy saving

Cooling during long-term storage of apples is a costly endeavour where electricity costs contribute up to 60% of the total variable costs at the end of storage. Here, the effect of controlling on-off cooling cycles on temperature and quality change uniformity and energy consumption is investigated with transient CFD models. The quality change of apples during the storage season as a function of position in the room is calculated with a firmness model using the FRISBEE tool. The on-off cooling cycle is regulated based on three different cooling differentials (0.4, 0.5 and 0.7°C). Temperature fluctuations were large near the edges of the stack. A larger cooling differential led to larger fluctuations in the middle of the stack compared to the smaller differentials. Although off-cooling cycles were longer with larger differential, overall this strategy consumed more energy. Differences in apple firmness changes between the three cooling differentials are found insignificant. The smaller cooling differential resulted in a better overall performance.status: publishe

CFD modelling of the 3D spatial and temporal distribution of 1-methylcyclopropene in a fruit storage container

In this paper, a direct model based on explicit geometry of stacked products in boxes was developed and used to study the diffusion, convection and adsorption of 1-methylcyclopropene (1-MCP) gas in cool stores for apple fruit. The discrete element method was employed to generate random stacking of spherical products in a box. A three-dimensional finite volume-based computational fluid dynamics model was developed, verified and used to study the distribution and partitioning of the 1-MCP gas inside loaded container. The study addressed the gas distribution in a 500 L container with or without air circulation. For each case, 80 kg Jonagold apples at 1 °C and a 1-MCP dose of 1 μL L−1 was used to collect validation data. In the presence of air circulation, diffusion–convection in air and diffusion adsorption in the product was applied. Simulations were performed with an unstructured tetrahedral mesh using the software ANSYS-CFX, a Reynolds-averaged Navier–Stokes solver. The case without air circulation was modelled as a diffusion problem in air and diffusion coupled with adsorption inside the product. Convection–diffusion–adsorption model parameters that were previously developed and validated were applied. The estimated equilibrium distribution of the 1-MCP gas equals 11, 34 and 55 % as unbounded in fruit, bonded in fruit and remaining in container, respectively. Profiles of free (unbounded) and adsorbed (bounded) 1-MCP concentrations inside fruit were estimated for reduced dosages: 0.5, 0.3, 0.1 and 0.02 μL L−1.The financial support of the Institute for the Promotion of Innovation by Science and Technology in Flanders (project IWT 060720) is kindly appreciated. These projects received co-funding of the Belgian Fruit and Vegetable Auctions. SmartFresh™ was kindly supplied for the experimental trials by AgroFresh Inc.status: publishe

Forced-convective cooling of citrus fruit: package design

Optimisation of package design for citrus fruit is required to increase the throughput, by reducing the precooling time, and to enhance fruit quality by providing fast and uniform cooling without inducing chilling injury. The cooling performance of an existing container and of two new containers (Supervent and Ecopack), as stacked on a pallet, was evaluated experimentally and numerically with computational fluid dynamics (CFD). The accuracy of the CFD simulations was confirmed by a good agreement with experiments. The best cooling performance was found for Ecopack, but removing airflow short circuits in this container may enhance the cooling performance even more. Also with respect to uniformity of cooling of the fruit and the magnitude of the convective heat transfer coefficients, in a specific container and between different containers on the pallet, the Ecopack container performed best, followed by the Supervent and the standard container. The new container designs thus clearly showed significant improvements in cooling performance.publisher: Elsevier articletitle: Forced-convective cooling of citrus fruit: Package design journaltitle: Journal of Food Engineering articlelink: http://dx.doi.org/10.1016/j.jfoodeng.2013.03.026 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved.status: publishe