固定化糖化酶型时间-温度指示器在酸奶质量检测上的应用

研究了固定化糖化酶型时间-温度指示器(TTI)的动力学性能和反应终点,并求得了TTI的活化能;同时研究了酸奶的活化能和货架期寿命。根据TTI与食品的活化能以及反应终点的匹配原则,在恒温及变温条件下进行匹配实验。结果表明,在恒温和变温2种条件下,1#TTI的活化能都满足与酸奶的匹配要求,并且反应终点误差在15%以内,能够比较准确地监测酸奶品质变化,从而预测酸奶的寿命。     

固态酶型时间温度指示器性能研究

目的以糖化酶、淀粉为主要原料,研制一种激活方便的固态酶型时间-温度指示器。方法对糖化酶进行微胶囊化处理,以糖化酶反应体系为基础,研究不同因素对指示器色差值的影响,确定在4℃条件下,时间在5~6 d的指示器配比。结果确定了固态酶型TTI的反应配方,通过测定其在不同温度下的反应速率,得到了7组TTI体系的活化能,其活化能值分别为106.68,98.47,87.66,89.73,106.74,97.51和87.99 k J/mol。结论得到可用于4℃条件下的时间温度指示器的7组配方,根据其活化能的不同,可用于指示不同产品的货架期。     

基于嗜酸乳杆菌的时间温度指示器的制备及其性能表征

目的 为了监测食品贮藏和运输期间的品质,制备微生物时间-温度指示器(TTI)。方法 选择嗜酸乳杆菌作为时间-温度指示器的微生物,对配制成的9种混合pH指示剂溶液进行筛选,用合适的混合pH指示剂溶液制备TTI,加入不同浓度的嗜酸乳杆菌,在不同等温条件下(5、15、25℃)贮藏检测其指标,以合适的指标参数为响应值探究其动力学与温度依赖性。结果 9种混合pH指示剂溶液中有5种颜色变化较明显,用其中一种制备TTI,以色差值(?E)为响应参数得出其活化能(E_a)为84.9 kJ/mol。结论 5种颜色变化较明显的混合pH指示剂溶液可以作为TTI的指示剂,制备的微生物型TTI有潜力应用于活化能59.9 kJ/mol≤E_a≤109.9 kJ/mol的食品品质指标的货架期预测中。     

没食子酸时间温度指示器的制备及性能研究

目的 基于没食子酸(Gallic Acid,GA)的特性,制备可以通过调节pH值改变活化能的时间温度指示器(Time Temperature Indicator,TTI),以期为新型TTI的开发提供参考。方法 制备不同GA浓度、pH值的GA TTI,在恒温条件下储藏,探究GA浓度和pH值对TTI颜色变化的影响。测定制备TTI的吸光度值,构建TTI颜色响应的温度动力学模型,并确定其动力学参数和活化能。结果 GA浓度为0.02 mol/L时TTI对温度最为敏感,故制备出GA浓度为0.02 mol/L,pH值为6.5、7.0、7.5、8.0的4种TTI。pH值为6.5时,TTI从无色变为黄褐色;pH值为7.0时,TTI从无色变为草绿色;pH值为7.5和8.0时,TTI从无色变为蓝绿色。利用吸光度计算出的4种TTI的活化能分别为85.99、44.93、29.57、25.03 kJ/mol。结论 不同pH值的GA TTI颜色变化明显,且GA TTI活化能有一个较大的范围,适用食品类型广泛,有潜力作为一种新型TTI。     

胶态金纳米型时间-温度指示器性能研究

目的 探究基于金纳米颗粒的时间温度指示器（Time-temperature indicator, TTI）的变色机理及不同制备参数对其动力学参数的影响,为其在食品上的实际应用提供参考依据。方法 以明胶与氯金酸的还原反应为基础制备胶态金纳米型时间-温度指示器。通过紫外-可见分光光度计对TTI的吸光度进行测定,并将其与时间进行非线性拟合。采用单因素实验探讨制备参数对反应速率、变色寿命和活化能的影响。结果 TTI体系中生成的金纳米颗粒使得TTI呈现紫红色,金纳米颗粒数量的增加导致TTI的颜色变深。明胶用量减少而明胶-氯金酸质量比不变,以及明胶用量不变而明胶-氯金酸质量比增大的情况下,TTI体系的反应速率变慢,变色寿命延长。明胶-氯金酸质量比决定了TTI体系的活化能。TTI的活化能的范围为77.89～84.58 kJ/mol。结论 TTI具有监测因脂肪氧化而变质食品的潜能,通过调节TTI的制备参数可改变其变色寿命以匹配不同货架期的食品。     

生物供电时间温度指示器在酸奶中的实验研究

目的 研究生物供电时间温度指示器(Time-temperature integrator,TTI)放电参数与酸奶品质参数之间是否存在相关性.方法 实验以马铃薯为生物电池的底物,铜片和锌片为电极制作生物供电TTI,将生物供电TTI和酸奶同时置于温度37℃下存放30 min,其余时间置于2～6℃下恒温贮存,模拟酸奶从产地到消费者住所经历的多次温度变化,通过自制平台实时获取时间、温度和生物供电TTI的放电参数,以2～6℃恒温贮存的酸奶和生物供电TTI为对照,检测实验过程中酸奶的乳酸菌数和霉菌数的变化情况.结果 通过实验发现生物供电TTI的输出电压幅值和放电累积量均会随环境温度变化发生相匹配的变化,同时与乳酸菌数的变化也满足一定的线性关系.结论 生物供电TTI具有检测酸奶变质的潜能,通过改变TTI的电导池常数、底物种类、预处理温度和时间都可以改变其放电总量,以匹配更多的食品.     

微生物型时间‒温度指示器(TTI)研究进展

目的 介绍微生物型时间–温度指示器(Time Temperature Indicator,TTI)在食品智能包装中的研究进展,为TTI在食品品质监测上的应用提供一定的参考和理论依据。方法 概述微生物型TTI在食品智能包装中的研究进展,微生物TTI的组成,包括TTI微生物、培养基和pH指示剂;总结微生物TTI基于总色差(ΔE)和可滴定酸度(TA)的响应机制,以及微生物TTI模型的建立,并分析其应用和发展趋势。结论 大量的文献证明微生物TTI是可用于监测食品贮藏运输过程中温度历史的有效工具,有广阔的发展前景。     

温度对碱性脂肪酶型 TTI 可靠性的影响

酶型时间-温度指示器是一种新型的包装食品质量指示装置,在生产后到使用前的贮藏过程中酶活的变化直接关系到在应用中的可靠性。研究了25,37,50℃条件下,基于扩散显色的酶型时间-温度指示器(TTI)中酶活的变化规律,进行了动力学建模,并通过其动力学方程对该TTI在0℃和3℃下的品质变化状况进行了预测和验证。结果表明,该酶基体系在0℃贮藏180 d仍可以保持88.37%的相对酶活,与理论预测酶活的相对误差为3.37%。根据Orellana的研究标准,其相对酶活大于85%,可以有效保持其扩散显色特性。     

时间温度指示器的研究与应用

随着食品安全问题越来越引起人们的重视,作为食品品质质量监控器的时间温度指示器（TTI）应运而生。对物理型、化学型以及生物型TTI的工作原理、特点与研究应用进展进行了综述。指出今后TTI的研究方向主要有3个,即发展条件激活式TTI、加强食品腐败变质速率与TTI指示的匹配性研究以及发展可印刷或涂布的TTI。     

一种酶型时间温度指示器的研究

食品保质期是食品质量安全的一个重要方面,而温度对于食品质量变化的影响较大却难以控制,使得食品保质期的可信度有所下降。时间温度指示器(TTI)的研发可以很好地解决这一难题,可以对食品流通环境中的关键影响因素进行监控、记录,通过时间温度累积效应来指示食品的安全程度。TTI在国外已被广泛用在大型超市及物流监控系统中,而我国对TTI的研究尚显薄弱。本文利用碱性脂肪酶-底物反应体系开发了一种时间温度指示器,建立了时间-温度-响应值模型,并对其应用形式、动力学参数进行了初步的研究,得出响应的活化能在52~56k J/mol,该体系有望用作检测环境温度的指示卡。     

鲜牛奶品质参数的动力学特性研究及货架期预测

目的 为了研究鲜牛奶的品质参数变化规律,建立鲜牛奶的货架期模型。方法 对鲜牛奶的脂肪、蛋白质、pH值和酸度在不同贮藏时间和温度内的变化进行分析,通过食品化学反应动力学方程和阿伦尼乌斯方程对鲜牛奶品质参数进行动力学特性研究。结果 鲜牛奶中脂肪、蛋白质、pH值在贮藏期内呈下降趋势,酸度呈上升趋势。4 ℃能减缓鲜牛奶pH值的下降和酸度的上升。结论 酸度能很好地表达鲜牛奶品质的变化过程,并且通过化学反应动力学特性研究得到了鲜牛奶酸度的活化能和基于酸度的鲜牛奶的货架期模型。     

燕麦生鲜湿面贮藏品质变化及货架期预测模型研究

目的 构建一种新的径向基函数神经网络货架期预测模型。方法 研究不同贮藏温度下燕麦生鲜湿面的微生物、理化等指标的变化情况，通过Pearson相关性分析，筛选影响燕麦生鲜湿面货架期的主要因素，利用微生物生长动力学模型和径向基函数神经网络模型对燕麦生鲜湿面的剩余货架期进行预测。结果 微生物生长动力学模型不能很好地拟合燕麦生鲜湿面菌落总数的变化情况，预测精度较差，径向基函数神经网络预测模型的预测值与实际值的相对误差为2.66%。结论 径向基函数神经网络预测模型的效果较好，为以后食品货架期的预测提供了一定的参考依据。     

Performances of time–temperature indicators in the study of temperature exposure of packaged fresh foods

The diffusion of time–temperature indicators (TTIs), attached as labels onto the packages of perishable food and non‐food products (intelligent packaging), is growing more and more. Aside from checking product shelf‐life, TTI devices can be used to monitor the distribution chain in real conditions. In this respect, the performances of some very common TTIs (A 12 Fresh Check, Lifelines Technologies) were extensively investigated in this work. The aim was to establish a procedure for an accurate, objective and reproducible estimate of the darkening progress of the sensitive area of the indicators and to discover a reliable data treatment to estimate the ‘effective temperature’, T_eff, namely a fictitious average temperature that can replace the overall temperature fluctuations experienced by a packaged fresh food. The image analysis approach was found very useful for an accurate and sensitive definition of the information provided by the indicators, leading to the evidence of a very slow darkening of the sensitive region, even at ?22°C. The kinetic parameterization of TTI responses was implemented in an EXCEL worksheet so as to directly evaluate T_eff on the basis of a set of label brightness values acquired by image analysis. Comparing the calculated ‘effective temperature’ with the average temperature recorded with conventional devices, the reliability of the TTI tags and the accuracy of this procedure was demonstrated. Taking into account the low cost of the TTI tags, their wide usage can be suggested to monitor the various steps of the real distribution chain of a given product, namely, transport, bench and home storage. Copyright © 2001 John Wiley & Sons, Ltd.     

Nisin/罗勒精油对冷鲜猪肉的保鲜效果

将Nisin与罗勒精油复配制备保鲜剂,对冷鲜猪肉进行了货架寿命研究。通过检测挥发性盐基氮、菌落总数、pH值以及脂肪氧化程度值,综合评价了保鲜剂的性能。结果表明:添加复合抑菌剂可有效抑制冷鲜猪肉菌落总数,保持猪肉鲜度;保鲜剂体积分数为0.75%时可延长冷鲜肉的贮藏期4d,体积分数为1%时可延长冷鲜肉的贮藏期6d。     

Monitoring quality changes in stored frozen strawberries with time-temperature indicators

Commercially available time-temperature indicators were examined as quality change monitors for frozen strawberries during storage. Strawberries were stored under constant (−12, −18 and −35°C) and variable temperature treatments, and quality changes were evaluated at three-week intervals by sensory and chemical analysis methods. Indicator response was strongly correlated with firmness and ascorbic acid change in strawberries stored at −12°C.

Résumé

Commercially available time-temperature indicators were examined as quality change monitors for frozen strawberries during storage. Strawberries were stored under constant (−12, −18 and −35°C) and variable temperature treatments, and quality changes were evaluated at three-week intervals by sensory and chemical analysis methods. Indicator response was strongly correlated with firmness and ascorbic acid change in strawberries stored at −12°C.     

Review of Time Temperature Indicators as Quality Monitors in Food Packaging

Time temperature indicators (TTIs) are devices used for recording thermal history and indicating the remaining shelf life of perishable products throughout their storage, distribution and consumption. This is achieved by the irreversible change of colour resulting from the cumulative effects of time and temperature. When applied in intelligent packaging, TTI can provide visual information that is easily accessible, and thus, consumers can judge from the visual information whether the food has deteriorated, which helps to assure the quality and safety of food. TTI can be classified into several different groups including chemical TTI, physical TTI, biological TTI, and other new types of TTI based upon different principles of colour change. Although these kinds of TTI can basically provide effective information about food quality, there are still a number of problems with them in the food supply chain, such as migration of toxic substances, the inaccuracy of temperature monitoring and the high cost in the area of commercial application. However, there are also some scientific methods to solve the aforementioned problems of TTI. In this paper, the latest research of TTI is summarized, its status and its main problems are elaborated and the prospect of its development is envisaged, aiming to provide reference and support for researchers in this realm. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Additives on Stability of Etoposide in PLGA Microspheres

The purpose of this article was to determine the shelf life of etoposide in poly(lacticco-glycolic acid) (PLGA) microspheres prepared with and without additives (i.e., tricaprin and isopropyl myristic acid ester [IPM]). The microspheres were prepared by a single-emulsion solvent extraction technique with and without 25% w/w additive. The batches of microspheres were subjected to an accelerated stability study at two elevated temperatures (70°C and 80°C or 80°C and 90°C). Samples were taken at 7, 14, 21, 28, and 35 days for estimation of drug content by high-performance liquid chromatography (HPLC). The drug stability in the microspheres was determined by plotting the log percentage drug remaining versus time to obtain the degradation rate constant k of etoposide at the measured temperature. This degradation rate constant was then used in the Arrhenius equation to obtain the activation energy of etoposide, which was utilized to determine the shelf life of the microspheres at room temperature. The results showed that all three microsphere formulations had good long-term stability at room temperature (6.62-8.86 years at 25°C). The plain microspheres were shown to possess a shelf life of 6.62 years, and the IPM and tricaprin were the most stable with shelf lives of 8.25 and 8.86 years, respectively.     

Effect of Additives on Stability of Etoposide in PLGA Microspheres

The purpose of this article was to determine the shelf life of etoposide in poly(lacticco-glycolic acid) (PLGA) microspheres prepared with and without additives (i.e., tricaprin and isopropyl myristic acid ester [IPM]). The microspheres were prepared by a single-emulsion solvent extraction technique with and without 25% w/w additive. The batches of microspheres were subjected to an accelerated stability study at two elevated temperatures (70°C and 80°C or 80°C and 90°C). Samples were taken at 7, 14, 21, 28, and 35 days for estimation of drug content by high-performance liquid chromatography (HPLC). The drug stability in the microspheres was determined by plotting the log percentage drug remaining versus time to obtain the degradation rate constant k of etoposide at the measured temperature. This degradation rate constant was then used in the Arrhenius equation to obtain the activation energy of etoposide, which was utilized to determine the shelf life of the microspheres at room temperature. The results showed that all three microsphere formulations had good long-term stability at room temperature (6.62-8.86 years at 25°C). The plain microspheres were shown to possess a shelf life of 6.62 years, and the IPM and tricaprin were the most stable with shelf lives of 8.25 and 8.86 years, respectively.