Investigating the Effects of Table Grape Package Components and Stacking on Airflow, Heat and Mass Transfer Using 3-D CFD Modelling

The flow phenomenon during cooling and handling of packed table grapes was studied using a computational fluid dynamic (CFD) model and validated using experimental results. The effects of the packaging components (bunch carry bag and plastic liners) and box stacking on airflow, heat and mass transfer were analysed. The carton box was explicitly modelled, grape bunch with the carry bag was treated as a porous medium and perforated plastic liners were taken as a porous jump. Pressure loss coefficients of grape bunch with the carry bag and perforated plastic liners were determined using wind tunnel experiments. Compared with the cooling of bulk grape bunch, the presence of the carry bag increased the half and seven eighth cooling time by 61.09 and 97.34 %, respectively. The addition of plastic liners over the bunch carry bag increased the half and seven eighth cooling time by up to 168.90 and 185.22 %, respectively. Non-perforated liners were most effective in preventing moisture loss but also generated the highest condensation of water vapour inside the package. For perforated plastic liners, cooling with a high relative humidity (RH) air minimised fruit moisture loss. Partial cooling of the grape bunch inside the carry bag before covering it with a non-perforated plastic liner maintained the required high RH inside the package without condensation. The stacking of packages over the pallet affected the airflow pattern, the cooling rate and moisture transfer. There was a good agreement between measured and predicted results. The result demonstrated clearly the applicability of CFD models to determine optimum table grape packaging and cooling procedures.     

QUALITY OF APPLE FRUIT IN RIGID FILM CONTAINERS

The storage quality of‘Delicious’ apples individually packaged in rigid film containers was investigated. Objective quality attributes (internal and external color, firmness, soluble solids and titratable acidity) were measured as a function of storage time with and without packaging in a rigid container. Overall firmness, acidity and soluble solids content decreased over a 70-day storage period. Significant effects of rigid film packaging and storage included: superior skin color, decreased weight loss, slight decrease in soluble solids content and increased firmness loss during ripening when compared to control fruit. Upon examination of the atmosphere surrounding individual fruit in these containers, increased levels of carbon dioxide and ethylene were found. Conversely, packaged fruit contained significantly less internal carbon dioxide than control samples. It was concluded that the atmosphere modified by the rigid film container hastened ripening of‘Delicious’ apples, thus deteriorating eating quality. An adequately ventilated packaged would probably alleviate this condition.     

Polyethylene Film Packaging of Citrus Fruit: Containment of Decaying Fruit

Decaying grapefruit (Citrus paradisi Macf.) stored under nonventilated conditions caused a substantial reduction in the oxygen and an increase in the carbon dioxide concentrations in the atmosphere. A comparable increase in the internal carbon dioxide concentration of sound fruit in the same container was also observed. Low oxygen caused an increase in the ethanol concentration in the juice of the sound fruit and the development of an undesirable stale flavor. Containment of the decaying fruit in polyethylene film limited the oxygen depletion. Thus, flavor quality of sound fruit from the containers with PE film-sealed decaying fruit was comparable to that of sound fruit stored in the absence of decaying fruit.     

MECHANICAL PROPERTIES OF SATSUMA ORANGE AS RELATED TO THE DESIGN OF A CONTAINER FOR BULK TRANSPORTATION1

The mechanical properties of Satsuma oranges were studied under static, quasi-static and impact loading in order to determine conditions leading to minimum fruit injury in containerized shipping. The results indicated that the use of containers is safe for a 70h transport provided the stacking height does not exceed 70 cm. The static load at the bottom of the container should not exceed 2 kg per fruit if permanent deformation is to be avoided; the fruit ruptures when the load exceeds 4.2 kg per fruit. The time-deformation curve under static load was explained with a Burgers model modified with a sliding element. Bruising energy by impact was 3 times and that by quasi-static loading 1.4 times as great as that by static loading. The relationship between impact acceleration and dropping height of single fruits agreed well with the Hertz’ theory of colliding spheres for dropping heights up to 15 cm.     

Experimental and Numerical Investigation of Airflow Inside Refrigerated Shipping Containers

During transportation of fruits and vegetables, factors such as temperature, air exchange, humidity levels, packaging design and stacking arrangements in the reefer (refrigerated shipping container) are extremely important to maintain the cold chain. In this study, the airflow distribution inside two types of refrigerated shipping containers (T-bar floor and flat floor) used for transporting fresh fruit handling were investigated. Computational fluid dynamics (CFD) model of airflow was developed and experimentally validated. Measurements of air velocities were taken from 222 sample positions inside a full-size reefer. The validated model was then implemented to study the effects of container designs and operational conditions on airflow pattern and distribution. High and low evaporator speed scenarios of the two reefer designs (T-bar floor and flat floor) were investigated. The result showed that airflow distribution in the two container designs were markedly different. Good agreement was found between measured and predicted values of air velocities. The air exchange rate in the rear part of the reefers for the two designs were compared. For the flat floor reefer, the air exchange was 0.2 m³ h^?1 while for the T-bar floor, it was 0.6 m³ h^?1. Also, in the primary recirculation region, (between 3 and 8 m from the inlet side) the average vertical air velocity was higher in the T-bar floor reefer (0.04 m s^?1) than in the flat floor reefer (0.01 m s^?1). As a result, reefer with T-bar floor design exhibited a noticeable reduction of air recirculation zone and enhanced uniform vertical air movement compared to the reefer with flat floor design.     

真空绝热板覆盖率对冷藏厢体内部温度场特性的影响

采用嵌套真空绝热板结构制作隔热壁板的冷藏厢体具有绝热性能优越、热导率低和节能效果明显的特点。考虑到嵌入不同覆盖率嵌套的真空绝热板,对冷藏厢体内部温度场特性的影响,利用计算流体力学方法,对试验冷藏厢体内部的温度场进行数值模拟,分析了VIPs不同覆盖率厢体保温效果和内部温度场均匀性的变化规律,并进行了试验验证。结果表明:冷藏厢体壁板嵌入真空隔热材料可以提高厢体绝热保温效果,改善内部温度场的均匀性。在相同制冷量的情况下,随VIPs覆盖率的增加,厢内平均温差最高下降40%,厢内平均温降可增加43%。当覆盖率增加到大于66%时,厢体内温度场的均匀性趋于稳定。     

基于浸入边界法的流水线烘房非稳态流动传热模拟研究

运用浸入边界流动计算方法结合实验验证,模拟仿真集装箱烘干流水作业中隧道式烘房内的非稳态气体流速场和温度场.在计算中将运动的集装箱体设置为浸没体,烘房内空气近似为不可压流体.模拟计算与实测温度随时间变化趋势基本吻合,计算与实测值相对误差在7％以内,表明所采用的计算方法,对模拟计算隧道式流水作业烘房内的气流与传热非稳态问题是切实可行的.     

Effect of temperature and relative humidity during transportation on green coffee bean moisture content and ochratoxin A production

Changes in temperature, relative humidity, and moisture content of green coffee beans were monitored during transportation of coffee from Brazil to Italy. Six containers (three conventional and three prototype) were stowed in three different places (hold, first floor, and deck) on the ship. Each prototype was located next to a conventional container. The moisture content of the coffee in the container located on the first floor was less affected by environmental variations (0.7%) than that in the hold and on the deck. Coffee located in the hold showed the highest variation in moisture content (3%); in addition, the container showed visible condensation. Coffee transported on the deck showed an intermediary variation in moisture (2%), and there was no visible condensation. The variation in coffee moisture content of the prototype containers was similar to that of the conventional ones, especially in the top layers of coffee bags (2 to 3%), while the increase in water activity was 0.70. This suggests that diffusion of moisture occurs very slowly inside the cargo and that there are thus sufficient time and conditions for fungal growth. The regions of the container near the wall and ceiling are susceptible to condensation since they are close to the headspace with its high relative humidity. Ochratoxin A production occurred in coffee located at the top of the container on the deck and in the wet bags from the hold (those found to be wet on opening the containers at the final destination).     

Effect of Agitation, Sampling Location and Protective Films on Light-Induced Riboflavin Loss in Skim Milk

Photodegradation of riboflavin in skim milk as influenced by continuous agitation, location within the container and protective films was studied. High performance liquid chromatography was used to monitor the riboflavin concentration in the milk. Retention of riboflavin in light-exposed, continuously agitated milk samples was significantly lower than in unagitated samples. Sampling positions within blow-molded polyethylene milk containers also had a significant effect on light-induced riboflavin loss. After 5 days of light exposure, riboflavin retention at the top of the unagitated milk containers averaged 58% compared to 92% retention for milk located at the bottom of the containers. Metallized-oriented, polyethylene-terephthalate films used as overwraps decreased penetration of visible light into milk samples and decreased the riboflavin photodegradation.     

Modelling Cooling of Packaged Fruit Using 3D Shape Models

This study presents a novel methodology to model the cooling processes of horticultural produce using realistic product shapes rather than commonly used simplified 3D shapes, such as spheres. Variable 3D apple and pear models were created by means of a validated geometric model generator based on X-ray computed tomography images. The fruit were randomly stacked into a geometrical model of a corrugated fibreboard box using the Discrete Element Method. A forced-air cooling process was simulated for three such apple filling patterns using CFD and the results were compared to those obtained with fruit represented by equivalent spheres. No significant difference in average aerodynamic resistance between the real apple shape and its spherical representation was found. The main contributor to the overall pressure drop was the package design rather than product shape. However, large differences in local air velocity and convective heat transfer coefficients were found between the two representations. The degree of cooling uniformity between individual fruit was overestimated when using simplified product shapes: real apple fruit shapes cooled less uniform. This difference between real and simplified product shapes was even larger for a box filled with pear fruit that are more different from a spherical shape. These results demonstrate that improved computer-aided design approaches help in simulating more accurate convective cooling processes. In a next step, such simulations will be used for multi-objective optimization of packaging in terms of cold chain efficiency and cooling uniformity.     

荔枝的冷却方式选择

通过比较真空预冷、水冷和强制通风对荔枝的冷却效果,选择出它的最佳冷却方式。结果表明,真空预冷、水冷却和强制通风都适用于荔枝;而用冷水对荔枝冷却时,在指定时间内的终温最低,能满足正常商业需求,因此,水冷应为荔枝的最佳冷却方式。     

Computational modelling of the impact of polystyrene containers on radio frequency heating uniformity improvement for dried soybeans

Radio frequency (RF) heating has been explored as a new method for postharvest pasteurization and disinfestations, but the non-uniform heating problem needs to be solved. In this study, an experimentally validated simulation model was developed to investigate effects of applying a surrounding polystyrene container on RF heating uniformity improvement in dried soybeans. The computer model was built for soybeans with both low and high moisture contents placed in the rectangular shaped polypropylene and polystyrene containers and heated in a parallel plate RF system. Results showed that the temperature uniformity was greatly improved by placing soybean samples in the polystyrene container other than the polypropylene one. The maximum temperature difference and uniformity index (UI) were reduced. The inner corner radius of 8 cm combined with container thickness of 8 cm could provide the best heating uniformity for soybeans. This newly developed technique can be easily implemented to improve the RF heating uniformity of other low-moisture legumes for industrial applications.Industrial relevanceRadio frequency (RF) heating has been explored as a new method for postharvest pasteurization and disinfestations of low-moisture granular legumes, but the non-uniform heating problem needs to be solved before being applied in industry. A validated simulation model was used to demonstrate the better container material and design for ensuring good temperature distributions in practical RF treatments. The optimal parameters from computer simulation may save time and reduce the cost to facilitate the design and scaling-up of the RF treatment protocols.     

双真空液体定量灌装原理及其应用特点

本技术是采用负压式灌装原理，将液体先一次灌装到标准容器内，这是事先调整好的计量容量，然后再灌装到所装容器内，这样大大提高了计量的精度，解决了玻璃瓶或者其他容器大小不一的矛盾。由于采用了两次灌装，对于瓶的形状、直径大小、壁厚、高低没有多大的限制，因此，在同一台机器中可同时使用不同规格的瓶子，还可广泛适用于不透明的容器，如瓷瓶，铝制瓶和塑料瓶的液体灌装。     

Effect of box materials on the distribution of 1-MCP gas during cold storage: A CFD study

1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to delay ripening of fruits. The substance is applied in gas form (as a fumigant) in the storage room. In long term postharvest cold storage, fruit are placed in boxes (usually plastic or wooden bins) and stacked in a specific pattern. The top of the boxes are frequently covered with a thin plastic sheet for the purpose of reducing fruit moisture loss. Wooden boxes, card linings and other plant based porous materials used in bins have 1-MCP adsorption capacity. Plastic covers affect the airflow and with that the 1-MCP transport. In this paper, the influence of box materials and plastic cover on the distribution of 1-MCP in cold storage was studied using validated CFD models. Reynolds Average Navier–Stokes equations with the SST k–ω turbulence model were used to calculate the airflow. Diffusion, convection and adsorption of 1MCP were modeled to obtain 3D spatial and temporal distributions of 1-MCP inside a storage container, boxes and fruit. Time dependent profiles of calculated 1-MCP concentrations in the air in the container agreed well with measurement data. The plastic cover imposed no effect on the adsorption of 1-MCP. Wooden boxes notably adsorbed 1-MCP from the treatment atmosphere and may reduce the efficacy and uniformity of the treatment.     

Sea transport of bananas in containers – Parameter identification for a temperature model

Losses of product quality during the sea transport of bananas in containers are related to the emergence of hot spots. In order to analyze critical conditions, a spatial temperature profile was recorded ashore in a container loaded with banana pallets. The identification of a structured system model showed that it is possible to reduce the information on the measured temperature curves to a set of only two index values. These can be interpreted as factors for coupling to the air stream and for the amount of heat generated by biological processes per banana box. The width of gaps between pallets was identified as the major influence on the spatial temperature profile. Boxes from which the unwanted banana ripening heat cannot be channeled away by the cooling unit can be detected by the quotient of the index values.     

两种木质容器醇化处理对雪茄烟支挥发性成分的影响

为提升雪茄烟支品质及风格特征,研究了木质容器醇化处理对雪茄烟支挥发性成分和感官品质的影响。采用顶空-固相微萃取-气相色谱-质谱（HS-SPME-GC-MS）法分别检测了杉木、香柏木醇化处理前后雪茄烟支的挥发性成分,分析了醇化处理对雪茄烟支中挥发性成分种类、质量分数以及感官品质的影响。结果表明：(1)从雪茄烟支样品中共检测出55种挥发性成分,以烯烃类为主,其次为含氮化合物。杉木和香柏木醇化处理均能够明显增加雪茄烟支中挥发性成分的种类,增加的挥发性成分以烯烃类为主,其中,香柏木醇化处理增加的挥发性成分的种类更多。(2)与原料烟支相比,杉木醇化处理烟支中主要筛选到25种质量分数差异的挥发性成分,其中,23种成分的质量分数显著上调（FC>2、P<0.05）;香柏木醇化处理烟支中主要筛选到35种质量分数差异的挥发性成分,其中,34种成分的质量分数显著上调（FC>2、P<0.05）。(3)杉木和香柏木醇化处理均能够在一定程度上提升雪茄烟支的香味、杂气、刺激性、余味等感官品质得分,其中,香柏木醇化处理的效果好于杉木。通过杉木和香柏木两种木质容器醇化处理均能提升雪茄烟支的品质和...     

DIMENSIONLESS CORRELATION FOR ESTIMATING INTERNAL PRESSURE IN THIN-WALLED ALUMINUM CONTAINERS DURING THERMAL PROCESSING

The need for creating container initial pressure, overpressure requirements and maintenance during thermal processing of thin‐walled aluminum containers is briefly discussed. the initial pressure within containers was achieved by injecting liquid nitrogen (LN₂) into the container headspace (0.5, 0.75 and 1 in.) prior to seaming. Experiments were conducted using a computer‐controlled retort with water‐immersion as heating medium, and temperatures ranging from 241 to 261F. Product initial temperature varied from approximately 45 to 135F. Container internal time‐pressure history during processing was monitored using a remote pressure sensor mounted within the container. Using water as model food, a dimensionless correlation that related the maximum cortainer pressure to product headspace, initial temperature and pressure was developed. Increasing retort temperature increased the maximum container internal pressure, while increasing product initial temperature decreased the maximum internal pressure developed within the container processing. the effect of product initial temperature on the maximum internal pressure was attributed to the amount/level of entrapped gasses present. Developed correlation using water predicted the internal pressure for 5% bentonite suspension with marginal errors (2 to 7%). However, the model failed to predict the maximum pressure for oil‐filled containers.     

Application of RFID technologies in the temperature mapping of the pineapple supply chain

Current temperature tracking systems lack the convenience and accuracy demanded by the real conditions of a fast-paced produce supply chain. In recent years RFID technology has been suggested to be an enhanced method for temperature tracking because of its many benefits, such as using little instrumentation, offering the quick readings necessary for real-time decision making, and allowing the capture of long-duration temperature profiles. However its limitation lies in that probeless systems fail to provide accurate temperature readings in some of the critical points of the pallet and the load. The objective of this work was to study the use of RFID in temperature monitoring by comparing the performance of RFID temperature tags versus conventional temperature tracking methods, as well as RFID temperature tags with probe versus RFID temperature tags without probes and their utilization along the supply chain. Therefore, the temperature mapping of a shipping trial comprising pallets of crownless pineapples instrumented using different RFID temperature dataloggers and traditional temperature dataloggers and packed in two kinds of packages (corrugated boxes and reusable plastic containers) inside a container was performed. The results showed that RFID temperature tags are analogous with regards to accuracy to the conventional methods, but have a superior performance because they allow quick instrumentation and data recovery, and the possibility of accessing the sensor program and data at any point of the supply chain without line of sight. In addition, the use of RFID tags with probe was justified by its role in determining the efficiency of the pre-cooling operations and low temperature abuse tracking during transportation and refrigerated storage; while the RFID tags without probe proved useful for high temperature abuse monitoring during transportation and refrigerated storage. The creation of a RFID sensor with a probe, able to record both ambient and pulp temperatures simultaneously is suggested. Presented at Food Processing Automation Conference, American Society of Agricultural and Biological Engineering (ASABE), Providence, RI, USA, June 28–29 2008.     

基于视觉自主移动叉车货盘识别方法研究

讨论了几种常见的货盘识别算法并对其适用情况和性能进行了分析,提出了一种基于货盘颜色和货盘底边角点特征的算法.算法采用由粗到细的检测策略:提取货盘颜色,对货盘候选区域进行预检测,提取最长的货盘底边,利用角点确定货盘位姿.指出了基于视觉的货盘识别方法未来的研究重点:鲁棒性的视觉识别技术和快速识别方法.     

Location of the Slowest Heating Zone for Natural-Convection-Heating Fluids in Metal Containers

Studies were conducted to locate the slowest heating zone (SHZ) along the vertical axis of vertically positioned containers for 16 liquids of different physical properties in 211 × 400 metal containers and for water in 13 sizes of metal container, and to assess significance of the findings for the design of thermal processes. For conditions tested, SHZ was found near the container bottom. The SHZ for natural-convection-heating products is usually located no higher than 25% of the container height above the container bottom. The SHZ's location is most critical in thermal process design for liquids of high initial viscosity in small containers where there is a large difference in temperature between heating medium and SHZ at the end of heating.