酶技术改善烟叶品质的研究进展

酶在烟叶调制,陈化和贮存期间起着非常重要的作用.近年来关于如何利用外加酶改善烟叶内在品质已经成为烟草行业的热点话题.利用酶制剂可以降解烟叶中过量的淀粉、蛋白质、细胞壁物质和果胶质,增加香气和改善质量品质.另外,酶制剂在烟草添加剂、烟草香料、烟草薄片中的应用,酶制剂和微生物配合使用的研究也在增加.     

Physicochemical Properties of a Time-Temperature Indicator Based on Immobilization of Aspergillus oryzaeα-Amylase in Polyacrylamide Gel as Affected by Degree of Cross-linking Agent and Salt Content

ABSTRACT: Currently available time-temperature indicators (TTIs) with favorable thermal inactivation kinetics are physically incompatible with microwave or radio frequency systems. Here, TTIs for microwave and radio frequency food pasteurization processes were developed that have dielectric properties that match target foods. The TTI can be easily recovered from a food and assayed using a rapid, simple colorimetric assay. Enzyme recovery was reduced by 8% but diffusion was retarded by 20% when bisacrylamide content was increased from 3.3% to 5.3%. The specific enzyme activity was highest in 20% polyacrylamide gels containing 2% NaCl. The residual enzyme activity in the TTI following 2 mo of storage at 8 °C exceeded 70%.     

Selective enzyme inactivation in a simulated system and in cabbage juice using electrospray technology

Enzyme inactivation is vital in fruit and vegetable juice processing, and selective inactivation is a major focus of enzyme inactivation. We used electrospray treatment to investigate directional enzyme inactivation in cabbage juice. Peroxidase and polyphenol oxidase in cabbage juice are the enzymes causing deterioration, whereas myrosinase is a beneficial enzyme. The particle size distribution, zeta potential and secondary and tertiary structures of the enzyme proteins were evaluated before and after enzyme inactivation. After the electrospray treatment, the relative activities of peroxidase, polyphenol oxidase and myrosinase in the mixed-enzyme simulation system were 4.09%, 5.62% and 84.67%, respectively, and those in the cabbage juice were 6.68%, 5.24% and 77.34%, respectively. Additionally, electrospray treatment induced substantial aggregation of peroxidase and polyphenol oxidase in the mixed-enzyme solution, and the secondary and tertiary structures of peroxidase and polyphenol oxidase were destroyed. Moreover, the conformation of myrosinase was preserved. These findings indicated that electrospray treatment can cause selective inactivation of peroxidase and polyphenol oxidase while preserving myrosinase activity.     

酶技术在食品加工中应用研究进展

酶技术是一种绿色安全高效的生物技术,对食品工业的技术革新和水平提高具有重要的作用。食品加工过程涉及许多复杂的理化变化,受热时营养素、颜色、质构、风味等方面容易受到破坏,这就为酶技术的应用提供了必要。目前,酶技术已经广泛应用于乳制品工业、肉制品工业、焙烤工业、饮料和果汁工业、淀粉和糖工业、油脂工业及安全检测等食品领域。本文主要从改善食品加工工艺、提高食品品质、提高食品安全性、增强食品质量控制等方面介绍了酶技术在食品加工中的应用进展,并对酶技术在食品行业中的发展作了展望。     

Modeling survival of high hydrostatic pressure treated stationary- and exponential-phase Listeria innocua cells

High Hydrostatic Pressure (HHP) inactivation (325–400 MPa; 0–20 min; maximum temperature 30 °C) of cells of Listeria innocua CECT 910 was studied in two different growth phases (exponential and stationary), and the corresponding survival curves were obtained for each case. The curves were fitted to two nonlinear models, the modified Gompertz equation and the Baranyi model. The kinetic constants calculated for both models, µ_max and k_max, indicated that cells in exponential growth phase were more sensitive to pressure than those in stationary phase. Both mathematical models were suitable for describing L. innocua HHP survival curves, rendering kinetic constants that increased with increasing pressure. When considering the experimental models validation, both Gompertz and Baranyi predicted in a similar way, however Baranyi had slightly lower A_f (Accuracy factor) and B_f (Bias factor) values, which indicated better prediction values. In summary, both mathematical models were perfectly valid for describing L. innocua inactivation kinetics under HHP treatment.Industrial relevanceThe mathematical models for inactivation and growth of microorganisms are the foundation of predictive microbiology and are used in risk assessments procedures as part of the food safety management system. Besides, these models together with those applied to inactivation of enzymes and destruction of quality factors are essential to optimize processes and thus to lay the foundations for industrial processing. It is therefore necessary to identify generally applicable kinetic models that will produce primary and secondary kinetic parameters and are statistically reliable as a key tool to predict the behaviour of microorganisms, enzymes and quality factors after processing.     

Polyphenoloxidase inactivation by light exposure in model systems and apple derivatives

The effect of UV-C and visible light on the enzyme polyphenoloxidase was studied in model systems and food. Enzyme inactivation under non thermal conditions was achieved following both UV-C and visible light exposure. UV-C light promoted enzyme inactivation in the entire range of irradiance and exposure time tested whilst visible light was effective only at high doses since lower intensity treatments were associated to enzyme activation. Polyphenoloxidase inactivation upon UV-C light exposure occurred as a consequence of protein aggregations other than those derived from thermal denaturation.The possibility to apply UV-C light exposure to achieve enzymatic stability of clear apple juice and fresh-cut apple slices was studied. Polyphenoloxidase inactivation in apple juice occurred to the detriment of natural occurring phenols which independently underwent photo oxidation. However, UV-C light exposure for few min prevented enzymatic browning during storage of refrigerated apple slices. The latter resulted comparable to the untreated apple slices from the sensory point of view.

Industrial relevance

Light irradiation is very effective in promoting polyphenoloxidase inactivation. UV-C light treatment has a good potential of successful application to achieve enzymatic stability in fresh-cut vegetables under non thermal conditions.     

POST-IRRADIATION INACTIVATION OF HORSERADISH PEROXIDASE

SUMMARY —Aqueous solutions of purified horseradish peroxidase lost enzymic activity not only during irradiation with gamma rays but also after irradiation. The higher the dose of irradiation, the greater the rate of post-irradiation inactivation. Enzyme activity loss after irradiation increased at higher temperatures of post-irradiation storage. Adjusting the pH of the irradiated enzyme solution to 9 resulted in greater inactivation than adjusting to pH 5 or 7. When the enzyme solution was diluted before irradiation the inactivation proceeded more rapidly after irradiation than in the more concentrated solution. When, however, the already irradiated enzyme was diluted, it was the concentrated enzyme solution that lost more activity. Glycerol added to irradiated enzyme diminished rate of inactivation. Irradiating a frozen enzyme solution resulted in very little or no loss of activity during post-irradiation storage. Neither irradiated water nor irradiated enzyme solution affected the activity of non-irradiated enzyme mixed with them. The following mechanism for the post-irradiation inactivation of HRPO is proposed: A portion of the enzyme which is not inactivated during irradiation is modified so as to result in subsequent inactivation by reacting with itself.     

抗酶解淀粉的研究进展及其在食品工业中的应用

抗酶解淀粉是食品工业中新发现的一种特殊的碳水化合物。本文对抗酶解淀粉的分类、形成及其在食品工业上的应用进行了综述。     

Inactivation of Escherichia coli by Carbon Dioxide under Pressure

Thermal inactivation of Escherichia coli was studied under CO₂ pressures of 1.2, 2.5, and 5 MPa at 25, 35, and 45°C. Two phases were observed in the destruction curves. The earlier stage was characterized by a slow rate of inactivation, which increased sharply at the later stage. An increase of pressure and/or temperature enhanced the antimicrobial effects of CO₂ under pressure. The effects on cell structure were studied by scanning electron microscopy and the specific mechanism of action appeared to be related to enzyme inactivation.     

Effect of a cold‐active pectinolytic system on colour development of Malbec red wines elaborated at low temperature

The effect of a new cold‐active pectinolytic system on colour of Malbec wines was studied under the following winemaking conditions: (i) fermentation at low temperature (20 °C) and (ii) prefermentative cold maceration (PCM) (5 °C–7 days) followed by traditional fermentation (28 °C). The pectinolytic system was mainly composed of polymethylgalacturonase and pectin lyase activities, detected under similar conditions to those in winemaking (pH 3.6–20 °C). The results show that the enzyme system significantly accelerated colour extraction by reducing the maceration time necessary for vinification at low temperature and shortening the PCM stage. Enzyme‐treated wines exhibited better chromatic parameters than their controls at devatting and after 6 months of storage. The cold‐active enzyme compensated the decrease in colour extraction due to the low maceration temperature, achieving high‐quality wines with chromatic characteristics similar to those of traditional wines.     

Inactivation kinetics of peroxidase and polyphenol oxidase in peach juice treated with gaseous ozone

The effectiveness of gaseous ozone for inactivating peroxidase (POD) and polyphenoloxidase (PPO) in peach juice was investigated. The suitability of first‐order and Weibull models to describe inactivation kinetics was also analysed. Peach juice was exposed to ozone (0.11 and 0.20 mg O₃ min^?1 mL^?1) in a bubble column up to 12 min at 20 ± 1 °C. Enzyme activities were reduced due to treatments. The magnitude of the inactivation increased with ozone level and exposure time. Reductions in activity after 12 min of treatment ranged between 99.5% and 99.8% for POD and between 93.9% and 97.3% for PPO, depending on ozone concentration. Inactivation curves were successfully fitted with the first‐order and Weibull models; although, based on the root‐mean‐square error, the corrected Akaike and the Bayesian Schwarz criterion, the Weibull model showed stronger capability in all cases.     

Quality-Related Enzymes in Plant-Based Products: Effects of Novel Food-Processing Technologies Part 3: Ultrasonic Processing

High-power ultrasound is a versatile technology which can potentially be used in many food processing applications including food preservation. This is part 2 of a series of review articles dealing with the effectiveness of nonthermal food processing technologies in food preservation focusing on their effect on enzymes. Typically, ultrasound treatment alone does not efficiently cause microbial or enzyme inactivation sufficient for food preservation. However, combined with mild heat with or without elevated pressure (P ≤ 500 kPa), ultrasound can effectively inactivate enzymes and microorganisms. Synergistic effects between ultrasound and mild heat have been reported for the inactivation of both enzymes and microorganisms. The application of ultrasound has been shown to enhance the rate of inactivation of quality degrading enzymes including pectin methylesterase (PME), polygalacturonase (PG), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) at mild temperature by up to 400 times. Moreover, ultrasound enables the inactivation of relatively heat-resistant enzymes such as tomato PG1 and thermostable orange PME at mild temperature conditions. The extent to which ultrasound enhances the inactivation rate depends on the type of enzyme, the medium in which the enzyme is suspended, and the processing condition including frequency, ultrasonic intensity, temperature, and pressure. The physical and chemical effects of cavitation are considered to be responsible for the ultrasound-induced inactivation of enzymes, although the dominant mechanism depends on the structure of the enzyme.     

Quality-Related Enzymes in Plant-Based Products: Effects of Novel Food Processing Technologies Part 2: Pulsed Electric Field Processing

Pulsed electric field (PEF) processing is an effective technique for the preservation of pumpable food products as it inactivates vegetative microbial cells at ambient to moderate temperature without significantly affecting the nutritional and sensorial quality of the product. However, conflicting views are expressed about the effect of PEF on enzymes. In this review, which is part 2 of a series of reviews dealing with the effectiveness of novel food preservation technologies for controlling enzymes, the scientific literature over the last decade on the effect of PEF on plant enzymes is critically reviewed to shed more light on the issue. The existing evidence indicates that PEF can result in substantial inactivation of most enzymes, although a much more intense process is required compared to microbial inactivation. Depending on the processing condition and the origin of the enzyme, up to 97% inactivation of pectin methylesterase, polyphenol oxidase, and peroxidase as well as no inactivation have been reported following PEF treatment. Both electrochemical effects and Ohmic heating appear to contribute to the observed inactivation, although the relative contribution depends on a number of factors including the origin of the enzyme, the design of the PEF treatment chamber, the processing condition, and the composition of the medium.     

食品中酶的微波钝化技术研究进展

食品中的酶对食品质量具有正反两方面的影响,因此在食品加工过程中,有效控制食品中酶的活性显得尤为重要。传统热处理是钝化食品中酶的主要方式,而近年来一些新型的钝化酶技术已成为新的研究热点。文中就微波钝化酶技术的原理与微波钝化酶的影响因素进行了综述,同时概述了微波钝化酶技术在食品中的应用状况,最后对微波钝化酶技术发展趋势提出了展望。     

Thermosonication of peach juice: investigation of PPO and POD activities,physicochemical and bioactive compounds changes,and development of FT-IR–based chemometric models for the evaluation of quality

In this research, the effect of thermosonication on peach juice was investigated. Enzyme inactivation increased with increasing power, temperature, and time. Enzymes were completely inactivated by thermosonication at 60 °C that was lower than the complete inactivation temperature (70 °C) of thermal treatment. Generally, as pH decreased, titratable acidity and °Brix increased by increasing temperature for each thermosonication treatment. The color of peach juice was preserved, and it became lighter. The bioactive components were protected with thermosonication. Fourier transform infrared (FT-IR) spectroscopy with chemometrics was used to evaluate polyphenol oxidase and peroxidase activity and quality attributes during thermosonication treatment. Moreover, the treatment methods were differentiated using principal component analysis, and models that correlated enzyme activity, quality attributes, and bioactive compounds with infrared spectra were constructed using partial least-squares. FT-IR with chemometrics can be used as a reliable method in peach juice quality determination during thermosonication.     

High‐Pressure Inactivation of Enzymes: A Review on Its Recent Applications on Fruit Purees and Juices

In the last 2 decades high‐pressure processing (HPP) has established itself as one of the most suitable nonthermal technologies applied to fruit products for the extension of shelf‐life. Several oxidative and pectic enzymes are responsible for deterioration in color, flavor, and texture in fruit purees and juices (FP&J). The effect of HPP on the activities of polyphenoloxidase, peroxidase, β‐glucosidase, pectinmethylesterase, polygalacturonase, lipoxygenase, amylase, and hydroperoxide lyase specific to FP&J have been studied by several researchers. In most of the cases, partial inactivation of the target enzymes was possible under the experimental domain, although their pressure sensitivity largely depended on the origin and their microenvironmental condition. The variable sensitivity of different enzymes also reflects on their kinetics. Several empirical models have been established to describe the kinetics of an enzyme specific to a FP&J. The scientific literature in the last decade illustrating the effects of HPP on enzymes in FP&J, enzymatic action on those products, mechanism of enzyme inactivation during high pressure, their inactivation kinetics, and several intrinsic and extrinsic factors influencing the efficacy of HPP is critically reviewed in this article. In addition, process optimization of HPP targeting specific enzymes is of great interest from an industrial approach. This review will give a fair idea about the target enzymes specific to FP&J and the optimum conditions needed to achieve sufficient inactivation during HPP treatment.     

Recent Developments in Superheated Steam Processing of Foods—A Review

Although the use of superheated steam has been known for quite a long time, only in the recent past has it emerged as a viable technology for food processing. Superheated steam, having higher enthalpy, can quickly transfer heat to the material being processed, resulting in its rapid heating. The major advantages of using superheated steam for food processing are better product quality (color, shrinkage, and rehydration characteristics), reduced oxidation losses, and higher energy efficiency. This review provides a comprehensive overview of recent studies on the application of superheated steam for food-processing operations such as drying, decontamination and microbial load reduction, parboiling, and enzyme inactivation. The review encompasses aspects such as the effect of superheated steam processing on product quality, mathematical models reported for superheated steam drying, and the future scope of application in food processing. Recent studies on process improvisation, wherein superheated steam is used at low pressure, in fluidized bed mode, sequential processing with hot air/infrared, and in combination with micro droplets of water have also been discussed.     

Mathematical Models for Prediction of Temperature Effects on Kinetic Parameters of Microorganisms’ Inactivation: Tools for Model Comparison and Adequacy in Data Fitting

Microbial inactivation often follows a sigmoidal kinetic behaviour, with an initial lag phase, followed by a maximum inactivation rate period and tending to a final asymptotic value. Mathematically, such tendencies may be described by using primary kinetic models (Gompertz based model is one example) that describe microbial survival throughout processing time when stressing conditions are applied. The parameters of kinetic models are directly affected by temperature. Despite the number of mathematical equations used to describe the dependence of the kinetic parameters on temperature (so-called secondary models), there is a lack of studies regarding model comparison and adequacy in data fitting. This work provides a review of mathematical models that describe the temperature dependence of kinetic parameters related to microbial thermal inactivation. Regression analysis schemes and tests seeking model comparison are presented. A case study is included to provide guidance for the assessment of secondary model adequacy and regression analyses procedures. When modelling temperature effects on sigmoidal inactivation kinetics of microorganisms, one should be aware about the regression methodology applied. The most adequate models according to the two-step regression methodology may not be the best selection if a global fit is applied.     

预测食品微生物学概述及应用

为了解预测食品微生物学的基本内容,综述了预测微生物学在食品中的应用.预测食品微生物学通过数学模型来预测微生物在不同环境条件下生长或死亡的数据.预测模型的分类有多种方法,根据微生物生长或失活的情况将预测模型分为生长模型和失活/存活模型.预测微生物模型已经广泛应用于食品安全质量管理和生产工艺中.     

Activities and conformation changes of food enzymes induced by cold plasma: A review

Food endogenous enzymes have impacts on color, texture and flavor of foods during food processing or preservation. Cold plasma is a novel non-thermal food processing technology, which has been extensively studied for contamination elimination and shelf life extension of foods. Particularly, much work has been reported about the effects of cold plasma on enzyme activities and alterations about enzymes conformational structures. It is thus necessary to understand the mechanisms of actions and applications of cold plasma technology in the conformation of food endogenous enzymes. This review focuses on the applications of cold plasma for the inactivation of various endogenous enzymes, including peroxidase, polyphenol oxidase, lysozyme, α-chymotrypsin, alkaline phosphatase, and pectin methylesterase. The activations of several enzymes, such as superoxide dismutase, catalase, and lipase, by cold plasma are also discussed. In addition, this review highlights the transformation of conformational structures including primary and spatial structures induced by chemical reactive species during cold plasma treatments, such as reactive oxygen species and reactive nitrogen species, especially, active sites consisting of prosthetic group and specific amino acids are demonstrated. Both extrinsic and intrinsic factors affecting cold plasma treatments are also described. In general, cold plasma exhibits the ability to activate or inactivate enzymes activities with affecting the conformational structures of enzyme. Further studies should be focused on exploration at molecular level for providing more insight on the interaction mechanism. In addition, equipment and process parameters of cold plasma operation for different fresh food products should be optimized for achieving appropriate control on enzyme variation and obtaining maximum efficiency.