Design of Packaging Vents for Cooling Fresh Horticultural Produce

This review focuses on the design of vents in packages used for handling horticulture produce. The studies on vent designs that are conducted to obtain fundamental understanding of the mechanisms by which different parameters affect the rate and homogeneity of the airflow and the cooling process are presented. Ventilated packages should be designed in such a way that they can provide a uniform airflow distribution and consequently uniform produce cooling. Total opening area and opening size and position show a significant effect on pressure drop, air distribution uniformity and cooling efficiency. Recent advances in measurement and mathematical modelling techniques have provided powerful tools to develop detailed investigations of local airflow rate and heat and mass transfer processes within complex packaging structures. The complexity of the physical structure of the packed systems and the biological variability of the produce make both experimental and model-based studies of transport processes challenging. In many of the available mathematical models, the packed structure is assumed as a porous medium; the limitations of the porous media approach are evident during vented package design studies principally when the container-to-produce dimension ratio is below a certain value. The complex and chaotic structure within horticultural produce ventilated packages during a forced-air precooling process complicates the numerical study of energy and mass transfer considering each individual produce. Future research efforts should be directed to detailed models of the vented package, the complex produce stacking within the package, as well as their interaction with adjacent produce, stacks and surrounding environment. For the validation of the numerical models, the development of better experimental techniques taking into account the complex packaging system is also very important.     

Heat Transfer and Moisture Loss of Spherical Fresh Produce

A computerized procedure was developed for simulating the post harvest cooling and moisture loss of produce by using a reliable mathematical model. This model was derived by assuming temperature and time variable respiration heat generation and temperature variable thermophysical property values. The developed procedure was employed to examine influence of five key dimensionless parameters on the cooling rate and moisture loss. These parameters are related to the rates of changes in density and thermal conductivity with changes in produce temperature, surface heat transfer conductance, transpiration rate, and environmental relative humidity. Theoretical results obtained from our examination were verified through heat transfer and moisture loss experiments by using fresh potatoes and tomatoes.     

Model for Fresh Produce Respiration in Modified Atmospheres Based on Principles of Enzyme Kinetics

A respiration model, based on enzyme kinetics, was proposed for predicting respiration rates of fresh produce as a function of O₂ and CO₂ concentrations. In this model, the dependence of respiration on O₂ was assumed to follow a Michaelis-Menten type equation (r = V_m[O₂]/{K_m+ [O₂]}), and the effect of CO₂ on respiration to follow an uncompetitive inhibition model (r = V_m[O₂]/{Km + (1 + [CO₂]/ Ki) [O₂]}). The model predictions agreed well with published data for a variety of commodities and with experimental data for cut broccoli. Fresh produce respiration rates (O₂ consumption or CO₂ evolution) at various O₂ and CO₂ concentrations, as well as transient and equilibrium gas concentrations within permeable packages, could be accurately predicted with the model equations.     

Moisture Sorption Isotherms of Canola Meals, and Applications to Packaging

Moisture sorption isotherms were determined for defatted canola meal at 16, 22, and 34°C. The isotherms were fitted to the Guggenheim-Anderson-deBoer (GAB) sorption equation. This equation was then used to develop a packaging model that predicted the changes of moisture con-tent of canola meal under stated environmental and packaging conditions. The model was tested using Melinex 813 (12 μm) and Propafilm C (28 μm) packaging films at 86% relative humidity and 23°C. The GAB equation provided a good fit to experimental data (<3% RMS). The monolayer moisture content of the meal was 9.5%. The enthalpy of sorption of the monolayer at 22°C was 84.61 KJ/mol. The model predicted the time required by packaged canola to attain a selected moisture content ± 0.5 days.     

Modeling the Lysozyme Release Kinetics from Antimicrobial Films Intended for Food Packaging Applications

ABSTRACT: The aim of this work is to develop a mathematical model to predict the lysozyme release kinetics from crosslinked polyvinylalcohol (PVOH) into an aqueous solution. The model was developed by taking into account both the diffusion of water molecules into the polymeric film and the counter-diffusion of the incorporated antimicrobial agent from the film into the aqueous solution. In particular, it was considered that the lysozyme release from a swelling polymer could be regarded as "anomalous diffusion" with moving boundary conditions. The water sorption kinetics of 4 films, differing for the degree of crosslink, were determined at ambient temperature (25 °C). The results obtained by fitting the model to the experimental data are satisfactory.     

新鲜猪肉气调保鲜包装技术

本文介绍新鲜猪肉气调保鲜包装混合气体的组成,鲜肉色泽的保持和防腐效果。通过新鲜猪肉的气调包装和真空包装保鲜效果试验得出:在0～6℃温度贮藏14天后,两种包装的防腐效果和保持色泽相比较,气调包装新鲜猪肉的细菌总数低于真空包装,血色素指标是真空包装的三倍。两种包装新鲜猪肉的pH、TVBN值都符合卫生指标要求。     

Intelligent Packaging: Concepts and Applications

ABSTRACT: Intelligent packaging is an emerging technology that uses the communication function of the package to facilitate decision making to achieve the benefits of enhanced food quality and safety. In this paper, the term intelligent packaging is defined based on a proposed model of packaging functions, which is consistent with the historical development of food packaging. A conceptual framework is also developed to provide more precise meaning to the definition and to elucidate the anatomy of the intelligent packaging system. The latest advances in smart package devices including barcode labels, radio frequency identification tags, time-temperature indicators, gas indicators, and biosensors are reviewed. The applications of the conceptual framework to Hazard Analysis Critical Control Points and microwave ovens are illustrated. A research roadmap for intelligent packaging is also suggested.     

Active Packaging Applications for Food

The traditional role of food packaging is continuing to evolve in response to changing market needs. Current drivers such as consumer's demand for safer, “healthier,” and higher‐quality foods, ideally with a long shelf‐life; the demand for convenient and transparent packaging, and the preference for more sustainable packaging materials, have led to the development of new packaging technologies, such as active packaging (AP). As defined in the European regulation (EC) No 450/2009, AP systems are designed to “deliberately incorporate components that would release or absorb substances into or from the packaged food or the environment surrounding the food.” Active packaging materials are thereby “intended to extend the shelf‐life or to maintain or improve the condition of packaged food.” Although extensive research on AP technologies is being undertaken, many of these technologies have not yet been implemented successfully in commercial food packaging systems. Broad communication of their benefits in food product applications will facilitate the successful development and market introduction. In this review, an overview of AP technologies, such as antimicrobial, antioxidant or carbon dioxide‐releasing systems, and systems absorbing oxygen, moisture or ethylene, is provided, and, in particular, scientific publications illustrating the benefits of such technologies for specific food products are reviewed. Furthermore, the challenges in applying such AP technologies to food systems and the anticipated direction of future developments are discussed. This review will provide food and packaging scientists with a thorough understanding of the benefits of AP technologies when applied to specific foods and hence can assist in accelerating commercial adoption.     

Ultrasonication and Fresh Produce (Cos lettuce) Preservation

Washing Cos lettuce in various sanitizers at different concentrations with and without ultrasonication (40 KHz) reduced the microbiological counts by 1 to 2.5 log colony‐forming units (CFU)/g immediately after washing. Ultrasonication of Cos lettuce in water, chlorinated water, peracetic acid, hydrogen peroxide, and their combinations at various temperatures (4 °C, 20 °C, 35 °C, 47 °C, and 50 °C) had no significant effects (P > 0.05) on the total or the psychrophilic counts during storage at 10 °C. The total count in Cos lettuce reached 9.74 ± 0.035 log CFU/g after ultrasonication (2 min at 50 °C) in chlorinated water (100 mg/L) and storage for 6 d at 10 °C. Extending the ultrasonication (40 kHz) of Cos lettuce for up to 20 min did not improve the bactericidal effect of ultrasonication. However, long‐time ultrasonication (20 min) caused significant (P < 0.05) damage to the quality of Cos lettuce tissues.     

蜂王浆萃取物保湿性能评价

本实验考察了蜂王浆萃取物和萃取残渣在8种相对湿度下的吸湿、保湿率以及随时间的变化情况.结果表明,蜂王浆萃取物具有一定程度的吸湿性和较持久的保湿性,尤其在较干燥环境下,保湿性能持久,无明显下降.因此,蜂王浆萃取物作为保湿剂有一定的应用前景.     

吸湿排汗织物的开发和应用

介绍COOLPLUS吸湿排汗纤维与棉混纺织物的开发过程,关键技术和主要工艺参数的优选,织物的性能分析,以及产品的最终应用。     

新鲜猪肉气调保鲜包装技术与设备

本文介绍鲜猪肉气调保鲜包装混合气体的组成、保持鲜肉色泽与防腐保鲜效果和GM型气体比例混合器的结构与性能。通过鲜猪肉的气调包装和真空包装保鲜效果试验得出：在0～6℃温度贮藏14天后，两种包装的保鲜和保持色泽的效果相比较，气调包装鲜猪肉的细菌总数低于真空包装，血色素的指标是真空包装的三倍。研制的GM型气体比例混合器，可使二种气体（O2与CO2或CO2与N2）或三种气体（O2、CO2、N2）任意体积比例混合，气体比例混合的精度（±1％，其标准流量在0．1MPa压力下为2．4m3／h）GM型气体比例混合器的供气量可满足热成型真空充气包装机或其他机型的气调包装操作要求。     

生湿面的气调包装一辐照协同保鲜

为延长生湿面贮藏期,研究了单一气调包装和气调-辐照协同技术对生湿面品质及保鲜效果的影响。采用不同的气体条件(100%CO_2、70%CO_2+30%N_2、50%CO_2+50%N_2)对生湿面进行包装,以空气包装为对照,测定生湿面在28℃贮藏过程中菌落总数、水分含量、蒸煮特性等指标的变化。结果表明70%CO_2+30%N_2气调包装的保鲜效果较好,能将生湿面贮藏期由2 d延长至3 d。随后采用不同辐照剂量(1、3、5 kGy)下的气调-辐照协同技术对生湿面进行保鲜处理,以单一70%CO_2+30%N_2气调包装为对照。结果表明不同剂量辐照均表现出显著的保鲜效果,其中1～3 kGy分别可延长生湿面货架期5～8 d,5 kGy可延长至11 d,但5 kGy对生湿面其他品质指标如蒸煮特性、质构特性和感官品质有显著影响,因此推荐1～3k Gy低剂量辐照下的气调-辐照协同技术对生湿面进行保鲜贮藏,该方法可改善生湿面食用品质并有效延长了贮藏期。     

浅谈鲜鸡蛋的保鲜包装加工一体化工艺

分析了包装加工一体化技术在鲜鸡蛋保鲜中的应用,对实现鲜鸡蛋包装加工一体化的设备和工艺进行了详细的论述,对实现生鲜鸡蛋的保存尤其是对夏季高温的保存有一定的实际意义。     

Microbiology of Fresh Produce: Route of Contamination,Detection Methods,and Remedy

Fresh fruits and vegetables are an important part of a healthful diet. They provide vitamins, minerals and fiber to help keep our body healthy. Occasionally, fresh fruits and vegetables can become contaminated with harmful bacteria or viruses, which are also known as pathogens. The major family of pathogen associated with food are members of Enterobacteriaceae which commonly form a part of microbiological criteria and their presence is traditionally related to hygiene and safety of foods. Organic fertilizers, irrigation water quality and soil are major source of contamination. For removal of pathogens, various decontamination procedures are also followed to reduce microbial load on the fruits. These are chemical preservatives and irradiation. Microbiological study of fresh produce can be done by various phenotypic, biochemical and molecular techniques so that pathogen can properly be identified. The World Health Organization (WHO) developed global risk communication message and training materials to assist countries in strengthening their food educating programs. There is a need for improved surveillance systems on food-borne pathogens, on food products and on outbreaks so that comparable data are available from a wider range of countries.     

抗菌包装技术及其在肉类保鲜中的应用

本文主要从抗菌机理、抗菌剂种类、抗菌包装体系设计、抗菌剂迁移和抗菌包装保鲜技术等多方面阐述了食品中抗菌包装技术的研究内容和现状,同时也论述了抗菌包装技术在肉类保鲜中的应用进展,最后提出了发展前景。     

Modified Atmosphere and Modified Humidity Packaging of Fresh Mushrooms

Sorbitol and sodium chloride were used to modify the in-package relative humidity (IPRH) of fresh mushrooms (water irrigated and CaCl₂ irrigated) stored in a modified atmosphere package (MAP) at 12°C. No differences were observed for maturity index and microbial population between mushrooms stored in modified atmosphere package (MAP) with or without moisture absorbers. Lower IPRH was observed in packages containing water irrigated (normally grown) mushrooms with sodium chloride, but resulted in over-drying of mushrooms and did not improve color. Normally grown mushrooms with 10 and 15g sorbitol had the best color. IPRH of 87–90%, within 9 days storage was considered optimum. No improvements in quality were found with moisture absorbers with normally grown mushrooms. However, a small amount of sorbitol helped to avoid condensation with CaCl₂ irrigated mushrooms.