Development of an intelligent enzyme indicator for dynamic monitoring of the shelf-life of food products

This work describes the development of a new smart time–temperature indicator, whose operating principle is based on the reaction between starch and iodine and the subsequent acting of an amylase on this complex, causing discoloration at a rate dependent on time and temperature of the medium. Laboratory simulations, manufacturing plant tests, and points of sale evaluated various enzyme concentrations in the TTI prototypes. The results showed that the color response of the indicators was visually interpreted as adaptive to measurement using colorimeter. Due to the possibility of defining the shelf-life of TTIs by varying enzyme concentrations, the indicators can be easily adapted to control the temperature conditions in the production chain of many perishable foods in a cheap, easy and accurate form.Industrial relevanceTemperature control during the distribution and storage of perishable products is often flawed, with conditions other than those recommended by the manufacturer. The difficulty in knowing the temperature history to which a food has been exposed to makes it difficult to predict its true shelf-life. An innovative alternative to dynamically ensure the validity of food can be the use of a smart time–temperature indicator (TTI). However, the success of the industrial application of TTIs depends on the simplicity, cost and reliability during operation, characteristics that have not yet been jointly observed in the indicators available in the market. In this perspective, it is part of the development of this work, which aims to develop a new TTI that presents a favorable combination of efficiency, reliability and viability. Thus, the aim is to contribute to the commercial acceptance of the concepts of smart packaging and in the establishment of regulation standards of usage, providing benefits to the conservation of a wide variety of foods.     

Modelling pH evolution and lactic acid production in the growth medium of a lactic acid bacterium: application to set a biological TTI

Time temperature integrators or indicators (TTIs) are effective tools making the continuous monitoring of the time temperature history of chilled products possible throughout the cold chain. Their correct setting is of critical importance to ensure food quality. The objective of this study was to develop a model to facilitate accurate settings of the CRYOLOG biological TTI, TRACEO. Experimental designs were used to investigate and model the effects of the temperature, the TTI inoculum size, pH, and water activity on its response time. The modelling process went through several steps addressing growth, acidification and inhibition phenomena in dynamic conditions. The model showed satisfactory results and validations in industrial conditions gave clear evidence that such a model is a valuable tool, not only to predict accurate response times of TRACEO, but also to propose precise settings to manufacture the appropriate TTI to trace a particular food according to a given time temperature scenario.     

Thermal inactivation kinetics of alkaline phosphatase in equine milk

Alkaline phosphatase (ALP) is widely used as an indicator of proper pasteurization in bovine milk. Due to interest in the use of equine ALP as a time/temperature integrator (TTI) for evaluation of the efficacy of thermal processing of equine milk, its inactivation kinetics were evaluated in whole and skimmed equine milk. Experimentally determined decimal reduction times showed that equine ALP is more readily inactivated in equine milk than its bovine counterpart. Thus, considering the required 6 D reduction of pathogens and the rather low enzyme level present in equine milk, equine ALP will not be suitable as indicator for correct pasteurization of equine milk under the conditions currently used in the reference method for the determination of ALP in milk-based products.     

Performance of a photochromic time–temperature indicator under simulated fresh fish supply chain conditions

The objective of this study was to investigate the performance of a photochromic time–temperature indicator (TTI) under dynamic temperature conditions simulating real fresh fish distribution chain scenarios. The work aimed at testing the possibility of extending the application of the TTI kinetic model, developed for specific temperature range of isothermal conditions, at low temperatures. The results showed that the TTI presented reproducible responses after being charged and during the discolouration process under different conditions, which revealed the reliability of the indicator. The TTI reflected well the temperature conditions of the studied scenarios, which indicates its potential application to continuously monitor the temperature history of the fresh fish supply chain. The kinetic model gave good fits in non‐abused scenarios at temperatures below 2 °C, presenting the potential for application of the model in determining the right charging level to suit a product’s shelf life at low temperatures.     

淀粉酶纳米花型时间-温度指示剂的制备及性能分析

目的：研制基于蛋白质杂化纳米技术和酶促反应的淀粉酶纳米花型时间-温度指示剂（time-temperature indicator,TTI）,确定其活化能及适合指示的食品种类。方法：利用淀粉酶与铜离子之间相互作用,对淀粉酶进行固定化,形成淀粉酶@Cu纳米花,改变淀粉酶用量,筛选出花形最好的纳米花,并测试纳米花中淀粉酶的生物活性及保存稳定性;以15 mL 40 g/L可溶性淀粉溶液为底物,4.5 mL 1 g/L碘液为指示剂,分别加入10、20、30、40、50、60 mg的淀粉酶@Cu纳米花,制备出6 种配方的TTI;在5、15、25、35 ℃的恒温条件下,研究6 种TTI的性能,观察变色过程,测定动力学参数,计算反应活化能值。结果：淀粉酶质量浓度为0.5 mg/mL时,淀粉酶@Cu纳米花的花形最完整,淀粉酶活性提高到3.42 倍,保存稳定性显著提高;6 种TTI呈现出从深蓝色到无色的变化过程,活化能分别为14.84、21.00、28.85、33.03、32.55 kJ/mol和32.83 kJ/mol。结论：淀粉酶纳米花型TTI操作简单,指示效果明显,根据TTI与食品匹配原则,该系列TTI适用于监测由扩散控制、酶反应、脂肪氧化等原因引起腐败变质的食品质量变化。     

A novel photochromic time–temperature indicator to support cold chain management

A detailed investigation of the behaviour of a new printable photochromic time–temperature indicator (TTI) was conducted to characterise its properties under specific temperature conditions and to analyse the influence of ultra violet (UV) light irradiation (activation) on the discolouration process. The reproducibility of the charging process and the discolouration process of the TTI were analysed. For different charging times the calculated activation energies based on the Arrhenius model ranged from 23.2 to 25.3 kcal mol^?1 depending on the UV light irradiation (charging time). A quality contour diagram was established to define the appropriate charging time for different kinds of products. Due to the possibility of defining the shelf life of a TTI by different charging times, this novel TTI constitutes a reliable tool to monitor the cold chains of a broad range of food products on their way from production to consumption.     

扩散型时间温度指示器在表征奇异果品质中的适用性

目的评估本研究所用时间温度指示器(time-temperature indicators,TTI)在奇异果品质监测中的应用情况。方法分别研究了4种贮藏温度下该TTI的颜色变化和奇异果品质变化情况。通过阿伦尼乌斯方程计算TTI颜色反应和奇异果品质变化的活化能Ea值,将TTI颜色变化活化能值与奇异果品质变化的活化能值进行比较,评估使用TTI表征奇异果品质的可行性。结果 TTI颜色和奇异果品质受贮藏温度及时间的影响。贮藏温度越高,TTI颜色和奇异果品质变化速度越快,TTI的RGB值减小速度越快。结论此TTI能够用于奇异果品质的表征,说明其在食品品质表征方面具有一定的应用潜力。     

Reliability of Time-Temperature Indicators as Food Quality Monitors Under Nonisothermal Conditions

Application of time temperature indicators (TTI) is based on response information or kinetic models from isothermal testing. The reliability of such models under variable temperature conditions was systematically studied. Nonisothermal experiments of two types were conducted involving prolonged exposures to high temperatures followed by storage at low temperatures to study the “history effect,” and storage at controlled, sinusoidaly varying temperatures. Three major types of commercial TTI were studied. Results showed that, although some types of TTI exhibit a significant “history effect,” the prediction models can be applied satisfactorily for the variable temperature storage.     

淀粉酶型时间-温度指示卡的研制

本文以淀粉酶、淀粉和碘为原料,制作监测食品质量的时间-温度指示卡。通过试验确定了制作工艺参数。最终制作出的指示卡颜色变化明显,可以用于食品质量监测。     

Applicability of Time-Temperature Indicators as Shelf Life Monitors of Food Products

A systematic approach that allows the correlation of the response of a Time-Temperature Indicator (TTI) to the consumed and remaining shelf life of a food product exposed to the same variable temperature conditions was developed. The approach was based on kinetic principles and is applicable to a TTI-food system without necessitating side by side testing. The applicability of three major TTI types to the developed scheme was studied. Experiments under several isothermal conditions were conducted and kinetic parameters for the three TTI were determined. All TTI showed an Arrhenius temperature dependence and their calculated activation energies ranged from 10 to 40 kcal/mol.     

谷物羊奶的杀菌工艺研究

本文研究了不同杀菌条件对谷物羊奶的影响,比较了巴氏杀菌、高温长时杀菌、高温短时杀菌、超高温瞬时(UHT)杀菌对羊奶的稳定性、口感、香气等感官品质的影响.结果表明,高温短时杀菌,即125℃下保温30 s杀菌,谷物羊奶稳定性最佳、口感清爽、香气浓郁.     

Impact of different pasteurization temperatures on the survival of microbial contaminants isolated from pasteurized milk

The thermal inactivation of selected microbes was studied using the low temperature long time (LTLT), high temperature short time (HTST) and 'pot' pasteurization methods. Survivors were enumerated after heating for up to 40 min for the LTLT and HTST pasteurization methods and after heating for up to 30 min for the 'pot' pasteurization method. With the exception of the Bacillus cereus strain, the selected microbes did not survive the LTLT and HTST pasteurization methods. The results from the 'pot' pasteurizer showed that B. cereus, Chryseobacterium meningosepticum, Pseudomonas putida, Acinetobacter baumannii and Escherichia coli strains survived the pasteurization conditions applied, showing that the 'pot' pasteurizer does not pasteurize effectively.     

THE INFLUENCE of pH ON the KINETICS of ACID HYDROLYSIS of SUCROSE

Sucrose acid hydrolysis was studied as a potential chemical time-temperature integrator to use under pasteurization conditions. A nonisothermal method was used to determine the kinetic parameters of this reaction at different pH values in the range of 0.8 to 2.5 and covering the range of temperatures from 50 to 90G. the nonisothermal method was first validated with the classical two-step isothermal method at pH 2.5. Kinetic parameters showed to be highly collinear (correlation of 0.99), but it was concluded that the activation energy can be assumed independent of pH and equal to 99 kJ/mole with the preexponential factor being proportional to the H⁺ concentration. Results are favorable for the future application of this system in the evaluation of pasteurization processes. Since the activation energy was found to be independent of the pH, this system is useful as a TTI for validation of mathematical models, but not so much for monitoring quality factors, except those with an equal activation energy.     

A sterilisation Time–Temperature Integrator based on amylase from the hyperthermophilic organism Pyrococcus furiosus

A candidate Time–Temperature Integrator (TTI) which is potentially suitable for use in validation of sterilisation processes was identified and tested. The TTI was based on the highly thermostable amylase produced from the extracellular medium of a Pyrococcus furiosus fermentation: this organism grows at temperatures in the region of 100 °C. Kinetic properties for the amylase following inactivation by heat showed it to be suitable for use as a sterilisation TTI. Isothermal kinetic data at 121 °C and non-isothermal kinetic data over the range 121 to 131 °C were determined. A decimal reduction time (D_T-value) at 121 °C of 24 min was calculated from isothermal tests and a range from 18.1 to 23.9 min from non-isothermal tests. A z-value of 10 °C was estimated from non-isothermal tests. Thus, sterilisation values (F₀) estimated from this TTI would be similar to F₀-values representative of the destruction of Clostridium botulinum spores. Industrial measurements under non-isothermal conditions were conducted in metal cans processed in an FMC reel and spiral cooker–cooler and a bar simulator, and also in plastic pouches processed in a Lagarde steam-air retort.Industrial relevanceMany food processes, such as canning, are based upon thermal sterilisation of the food material. The development of a reliable Time–Temperature Integrator for such a process would be industrially valuable by providing a simple way of validating such processes. This study demonstrates the feasibility of one such TTI.     

超声处理对羊乳中大肠杆菌和金黄色葡萄球菌的杀灭效果

以新鲜羊乳为原料,研究了超声处理对新鲜羊乳中大肠杆菌和金黄色葡萄球菌的杀菌效果,为羊乳的非热杀菌方法及产品开发提供参考。基于单因素实验,采用Box-Behnken试验设计研究了超声功率、温度及时间对羊乳中大肠杆菌和金黄色葡萄球菌杀菌效果的影响,并以大肠杆菌和金黄色葡萄球菌的灭菌对数值为响应值,通过响应面分析对超声处理条件进行了优化,并研究了超声处理和巴氏杀菌处理对两种菌株菌体的破坏情况以及贮藏期内菌落数的变化。结果表明,超声处理羊乳的最佳条件为超声功率530 W,超声温度60 ℃,超声时间30 min,在此条件下对大肠杆菌和金黄色葡萄球菌的灭菌对数值可到达7.55和6.53。与巴氏杀菌处理相比,超声处理能更大程度地破坏菌体细胞表面结构,杀菌效果更好,并能将羊乳贮藏期从巴氏杀菌处理后的14 d延长至21 d,品质要求仍符合国家标准。     

Development of a time-temperature integrator system using Burkholderia cepacia lipase

A time-temperature integrator (TTI) is a device used to show a time-temperature dependent change that reflects the temperature history and quality status of the food to which it is attached. An enzymatic TTI system based on the reaction between Burkholderia cepacia lipase and tricaprylin, which causes a pH change, was developed. The temperature dependence of the response rate of this new lipase-type TTI was modeled using the Arrhenius equation, and the estimated activation energy was calculated as 70.61±11.10 kJ/mol (±95% confidence interval). The TTI response was validated under dynamic storage conditions with independent variable temperature experiments, and a good agreement was obtained between the predicted and measured values.     

海洋生淀粉酶菌株发酵条件响应面优化

生淀粉酶是催化淀粉直接水解的酶类,其可广泛应用于食品、工业、医学等领域。该研究首先利用单因素试验研究发酵时间、发酵温度,发酵初始pH、装液量、接种量对生淀粉酶活的影响,并在此基础上利用响应面法设计试验,优化了海洋生淀粉酶菌株ZXS-1的发酵条件。结果表明,其最佳发酵条件为发酵时间38 h,发酵温度25 ℃,初始pH 7。在此最佳发酵条件下,生淀粉酶酶活可达445.2 U/mL,较优化前提高25.6%。     

Time temperatüre integration for chilled food shelf life monitoring using enzyme‐substrate systems

Abstract

Time Temperature Integrators (TTI) are simple devices to monitor temperature exposure history and relate it to food shelf life behaviour. Four colorimetric enzyme reaction systems are proposed as the basis for TTI use and results for their kinetic characterisation under isothermal conditions are presented. Nonisothermal experiments have shown that the proposed system response reflected accurately the dynamic nature of the environment temperature. The reliability of the proposed TTI systems was demonstrated by a case study on chilled fish shelf life prediction after storage temperature abuse.     

TEMPERATURES IN EGG PRODUCT FOAMS DURING VAT PASTEURIZATION

SUMMARY– Most egg products are pasteurized in continuous-flow equipment, but small quantities are more economically processed in a vat pasteurizer. By insulating itself, the surface foam in the vat process may be below pasteurization temperature for a significant part of the holding time and salmonellae in the foam may survive. Using a 100-gal vat, we generated foams on 5 egg products and measured foam temperatures during pasteurization. Maximum jacket temperature was held to 160°F and no product burn-on was observed in the vat. All products were held above their respective pasteurization temperatures for 30 min. The minimum temperature of a 6.5-in. liquid whole egg foam was below pasteurization temperature for 11 min after start of pasteurization. The delayed heating effect of a 1-in. foam on sugared yolk (10% sucrose by weight) was 13 min. Yolk and salted yolk (10% salt by weight) foams were below liquid temperature during heating; however, in both cases liquid and foam reached pasteurization temperature simultaneously. Minimum temperature of plain egg white foam (pH 9.0) did not reach pasteurization temperature during the holding period. In vat pasteurization, the holding time begins when the liquid reaches pasteurization temperature, and the holding time should be long enough for both foam heating and pasteurization of foam. Except for egg white, about 15 min was required to heat foam to pasteurization temperature. Adding 15 min for pasteurization of the foam yielded a total holding time of 30 min, with the temperature of pasteurization established on the basis of the 15-min holding time for the foam as follows: liquid whole egg, 133°F; yolk and yolk blends, 135°F; sugared and salted yolk, 139°F. With egg white, foam heating times were in excess of 30 min, and vat pasteurization, with a holding time of 30 min, was not effective.     

基于扩散型时间-温度指示器表征鲜银耳贮藏过程品质变化

为了研究扩散型时间-温度指示器(Time-Temperature Indicator,TTI)能否表征鲜银耳贮藏过程中品质变化,分别研究了不同贮藏温度(5、13、17、23 ℃)下,扩散型TTI的颜色变化和鲜银耳品质(失重率、可溶性糖含量及丙二醛含量)变化情况,通过化学品质动力学模型及Arrhenius方程分别计算扩散型TTI颜色变化和鲜银耳品质变化的活化能Ea,并将扩散型TTI颜色变化的活化能与鲜银耳品质变化的活化能进行比较,从而评估扩散型TTI与鲜银耳的品质变化的匹配性。研究结果表明,贮藏温度及贮藏时间对扩散型TTI颜色变化和鲜银耳品质变化均有影响,且贮藏温度越高,扩散型TTI由白色变为蓝色的速度越快,鲜银耳也越容易腐烂。通过化学品质动力学模型及Arrhenius方程计算得出扩散型TTI的活化能E_a值为36.1135 kJ/mol,鲜银耳失重率、可溶性糖含量及丙二醛含量的活化能分别为53.3144、53.3368、43.9744 kJ/mol,扩散型TTI与鲜银耳品质变化的活化能差值<25 kJ/mol,因此可以将此扩散型TTI用于鲜银耳贮藏过程中的品质监控。