Humidity-Regulating Trays: Moisture Absorption Kinetics and Applications for Fresh Produce Packaging

For packaged fresh produce, inappropriate high relative humidity (RH) levels and condensation of water vapour cause premature spoilage. Humidity-regulating trays were developed to solve this issue. They were made from a thermoformed multilayer structure: polyethylene (outside)/foamed hygroscopic ionomer (active layer) with 0 or 12 wt% NaCl/hygroscopic ionomer (sealing layer, inside). Moisture absorption kinetics of the humidity-regulating trays with 0 and 12 wt% NaCl (T-0 and T-12, respectively) was investigated under different RH conditions (76, 86, 96 and 100 %) at 13 °C for 16 days. Additional trays containing 7 g of distilled water were closed with a high barrier lidding film, and the headspace RH was continuously monitored as a function of time. As control, a polypropylene (control-PP) tray was used. Strawberries and tomatoes were used to test capability of the trays to regulate in-package RH. The amount of water absorbed by the T-0 and T-12 trays was 7.6 and 13.2 g, respectively. Active hygroscopic ionomer layer was effective in water vapour absorption, and the integration of NaCl into this active layer increased the water vapour absorption capacity of the tray. The Weibull model adequately described the moisture sorption kinetics of the individual packaging trays as a function of time. The headspace RH of trays covered with a lidding film was found to be 89.8, 99.6 and 100 % in the T-12, T-0 and control-PP trays, respectively. The T-12 trays containing fresh produce best regulated the in-package RH below 97 % and maintained overall quality, but at the expense of slightly higher product weight loss (2–3 wt% for strawberry, 1 wt% for tomatoes) compared to the control-PP trays (0.3–0.6 wt%).     

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。     

Method for Determining the Respiration Rate of Horticultural Produce Under Hyperbaric Treatment

A method was developed to determine the metabolic respiration rate (RR_m) of fresh produce during the transient period at the beginning of a hyperbaric treatment. This method allowed for the correction in the apparent respiration rate (RR_ap) by considering the dilution effect of flushing the system and the error associated with gas solubilisation as the gas partial pressure varied. The dilution process was simulated by using the general equation for exhaust ventilation, thus allowing for the elimination of the dilution effect during the calculation of the net respiration rate (RR_N). The error associated with the CO₂ solubilisation in the flesh of the produce was solved by measuring the CO₂ solubility in the tissues of tomato at various CO₂ partial pressures and using this value to generate a mass balance of CO₂ within the system. The RR_m was estimated by incorporating the initial respiration rate (RR_i) of untreated fruits with the respiration rate at equilibrium (RR_e). The kinetic of the RR_m was proposed to follow a negative exponential equation. The constant value (k) of the RR_m model was found to decrease exponentially with the partial pressure of CO₂ at equilibrium which affected the amount of gas solubilised and the time to reach equilibrium. The developed method should be validated for the RR_m of other produce during the transient period at the beginning of a hyperbaric treatment.     

化妆品纸盒包装新面孔

在高档化妆品包装领域,塑料包装长期以来一直占据着主导地位。然而随着人们环保意识的不断增强,越来越多的化妆品生产商开始寻求更加低碳环保的可持续包装,纸盒包装凭借其成本低、加工方式灵活、绿色环保等优势赢得了众多化妆品生产商的青睐。目前一些国外化妆品品牌开始相继采用纸盒包装,这不仅符合当前低碳环保的理念,更形成了化妆品包装市场的一道靓丽的风景线。     

新鲜采摘草莓的气调包装研究

使用自行研制的气调包装膜.对新鲜草莓进行气调包装研究。结果表明:在室温下,A-9保鲜膜的保鲜效果最好,可长达4 d,在保鲜柜中,A-5保鲜膜的保鲜效果最好,货架寿命可达20 d以上。     

Modified Atmosphere Packaging of Fresh Beansprouts

Freshly harvested beansprouts displayed a respiration rate of about 1 mmol O₂ kg⁻¹ h⁻¹ at 10°C which was strongly dependent on temperature, a 10-fold increase being observed every 16·5°C (z=16·5°C, ie Q₁₀=4·4). This commodity is also characterised by a high initial microbial load (about 10⁷ cells g⁻¹). During storage at various temperatures from 1 to 20°C, oxygen uptake rates dramatically increased with time and this phenomenon was well correlated with the development of aerobic microorganisms which reached 10⁹ cells g⁻¹ after 2 days at 20°C or 9 days at 1°C. Beansprouts were packaged in films, with permeabilities ranging from 950 to 200000 ml O₂ m⁻² day⁻¹ atm⁻¹, and stored at 8°C. Due to plant and microbial metabolism, oxygen concentrations decreased steadily within all packs until the onset of plant tissue decay. The latter occurred after 5–6 days with the least permeable films but did not occur within when the film permeability was over 100000 ml O₂ m⁻² day⁻¹ atm⁻¹. However, such films favoured brown discolouration, exudation texture and breakdown. The orientated polypropylene film (OPP) induced anoxic condition within 2 days and favoured anaerobic metabolism and necrosis of the sprouts. In all packages there was a rapid development of aerobic microorganisms and lactic acid bacteria that resulted in the accumulation of acetate and lactate and a decrease in pH. Thus, it clearly appeared that tissue decay was enhanced by microbial activity. At 8°C, 0·24 m² of film per kg of sprouts provided the optimal atmosphere composition (ie 5% oxygen and 15% carbon dioxide) when a film permeability of 50000 ml O₂ m⁻² day⁻¹ atm⁻¹ was used. These conditions allowed a shelf-life of 4–5 days.     

新鲜鲢鱼片的保鲜包装研究

为了延长在低温条件下鲢鱼的保鲜期,利用浸泡保鲜的方式筛选出3种理想的抗菌剂分别是:纳米TiO_2、茴香精油和山梨酸钾按照既定的浓度添加到低密度聚乙烯树脂中,经过高温造粒、流延、复合得到具有抗菌效果的复合薄膜。使用纳米TiO_2抗菌薄膜、茴香精油抗菌薄膜、山梨酸钾抗菌薄膜和普通复合薄膜(PE/PET)4种薄膜对新鲜鲢鱼肉包装并在低温条件保存,通过对比分析,研究几种薄膜对鲢鱼肉的保鲜效果。发现相比于普通复合薄膜,抗菌薄膜确实可以延长鲢鱼的保鲜期,其中纳米TiO_2抗菌薄膜对鱼肉的保鲜效果最佳,可以广泛推广为鲢鱼的包装材料,延长鲢鱼货架期。     

生物保鲜技术的研究进展

生物保鲜材料因为无毒、无副作用、可降解等特点已成为人们关注的热点。文中简述生物保鲜的特点 ,分类介绍了 6种生物保鲜技术 ,并对人们用于开发生物保鲜技术的微生物种类进行归纳 ,以及对生物保鲜的一般机理和应用前景进行了介绍。     

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.     

Evaluation of Zein Films as Modified Atmosphere Packaging for Fresh Broccoli

ABSTRACT: Modified atmosphere packaging (MAP) is increasingly used with minimally processed produce. Increased MAP usage coupled with negative environmental views associated with nondegradable synthetic packaging materials creates a need for biodegradable films. Zein films plasticized with oleic acid had been proposed for biodegradable packaging applications. Conversion treatments including lamination and coating films with tung oil were reported to improve water vapor and gas barrier properties of films. In this work, the ability of treated and untreated zein films to perform as MAP for fresh broccoli florets was investigated. Florets were packaged in glass jars sealed with zein films and stored under refrigeration for 6 d. Headspace oxygen and carbon dioxide concentrations were monitored during storage. Tested films allowed the development of modified atmospheres inside the packages. Broccoli florets packaged in the test films maintained their original firmness and color.     

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.     

超市生鲜猪肉高氧MAP气调保鲜包装研究

采用高氧MAP对超市生鲜猪肉进行气调保鲜包装,通过CO_2抑菌、O_2保色、NaCl、乳酸等栅栏抑菌保鲜正交试验,研究不同栅栏因子对超市生鲜冷却猪肉pH值、卫生指标和肉色货架期等生鲜品质的影响。结果表明:高氧MAP生鲜猪肉在3±2℃贮藏48h,其pH值、细菌总数、大肠杆菌有显著降低(p<0.01)、处在最新鲜的状态,随后缓慢地提高,5d能达到二级生鲜猪肉标准水平,与感官评定结果有良好的一致性;回归试验因素相关分析结果表明O_2、CO_2和NaCl与pH值、细菌总数、大肠杆菌MPN呈显著负相关,说明高氧、高CO_2MAP和2%NaCl适量调理的抑菌保鲜效果显著;正交试验优化结果为:70%O2～30%CO2～2%NaCl处理组合。     

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。     

国内新鲜食品气调包装技术研究现状

气调包装是一种重要的食品保鲜方法,可以有效延长产品的货架期。使用气调包装技术保鲜食品时,影响保鲜效果的因素主要有三个,一是包装气体的初始组分,二是保鲜过程中包装气体的变化,三是保鲜的温湿度条件。总结目前常用的两种果蔬呼吸模型,并分析其适用范围。总结出保鲜新鲜果蔬、鲜切蔬菜和肉类产品的初始气体组分。介绍不同包装膜对包装内外气体交换的影响。概述气调包装温湿度的相关研究。最后,对气调包装技术研究提出建议。     

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。     

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.     

新鲜度指示型包装技术在生鲜食品的应用进展

新鲜度是生鲜食品在贮藏、运输和销售过程中一个重要的品质评价指标,普通食品包装无法满足消费者对食品新鲜度的监测要求,而智能包装技术的出现让新鲜度的监测成为可能.智能包装技术通过利用指示剂和传感器来监测食品在贮藏中发生的物理、化学、生物变化,以反映运输和存储过程中包装食品或环境的状况.从指示剂和传感器两大类技术介绍智能包装...