Inactivation kinetics of polyphenol oxidase and peroxidase in pineapple juice by dielectric barrier discharge plasma technology

The non-thermal plasma technique is an innovative non-thermal approach for food preservation and decontamination. Polyphenol oxidase (PPO) and peroxidase (POD), the principal food degrading enzymes in pineapple juice, were inactivated by the Dielectric Barrier Discharge (DBD) plasma. The inactivation kinetics of PPO and POD in pineapple juice were examined at three different voltages 25, 35, and 45 kV for up to 10 min of plasma treatment. The present study's findings revealed that plasma parameters such as voltage and treatment time substantially reduced enzyme activity of both enzymes, with the former parameter having a more pronounced influence on enzyme inactivity. To mathematically represent the model parameters, established kinetic models viz. log-linear, Weibull, and logistic were fitted to observe experimental data. The Weibull model was discovered to be the best fit for the enzyme inactivation kinetics. The scale factor for PPO was 15.95, 10.87, and 5.73 min at 25, 35, and 45 kV, respectively which was lower than POD with scale factor 40.74, 19.76, and 7.28, respectively. This shows that POD was more resistant to inactivation by DBD plasma than PPO.     

Residual polyphenol oxidase and peroxidase activities in high pressure processed bok choy (Brassica rapa subsp. chinensis) juice did not accelerate nutrient degradation during storage

Polyphenol oxidase (PPO) and peroxidase (POD) cannot be fully inactivated by commercial high pressure processing (HPP) operations, and their residual activities may accelerate nutrient degradation during storage. This study hence aimed to establish the effect of residual enzyme activity on nutrient preservation in bok choy (Brassica rapa subsp. chinensis) juice. Bok choy juice was treated at 600 MPa for up to 20 min and enzyme inactivation, nutrient retention immediately after treatment and nutrient preservation during storage were determined. High residual PPO (85.1 ± 2.6%) and POD (68.5 ± 1.0%) activities remained after 20 min of treatment. Increasing the pressure holding time to enhance enzyme inactivation did not compromise total antioxidant capacity, vitamin C, carotenoids, isothiocyanates and vitamin K levels. Neither did it significantly reduce the vitamin C degradation rate during refrigerated storage. Maximising enzyme inactivation may thus not be necessary for nutrient preservation during the storage of HPP-treated bok choy juice.Industrial relevance textWith HPP, an increase in pressure or holding time is required to achieve higher levels of enzyme inactivation. Without the need to maximize PPO and POD inactivation, juice processors may employ the minimum pressure and holding time required for microbial inactivation. As vegetative bacteria are typically less resistant to HPP inactivation than these enzymes, this could translate to reduced energy costs and increased throughput.     

High pressure processing of cocoyam,Peruvian carrot and sweet potato: Effect on oxidative enzymes and impact in the tuber color

High pressure processing (HPP) is a non-thermal technology used to activate or inactivate enzymes. This study investigated the effects of HPP (600 MPa for 5 or 30 min at 25 °C) on cocoyam, Peruvian carrot and sweet potato color, and the polyphenoloxidase (PPO) and peroxidase (POD) activities in tuber cubes, puree, and enzyme extract subjected to HPP. The results showed enzyme inactivation by HPP in cocoyam (up to 55% PPO inactivation in puree and 81% POD inactivation in extract) and Peruvian carrot (up to 100% PPO and 57% POD inactivation the extract). In contrast, enzyme activation was observed in sweet potato (up to 368% PPO and 27% POD activation in puree). The color results were compatible to enzyme activity: the color parameters remained unchanged in cocoyam and Peruvian carrot, which showed high PPO and POD inactivation after HPP. Furthermore, the impact of HPP on the enzymes was influenced by the matrix in which HPP was carried out, evidencing that the enzyme structure can be protected in the presence of other food constituents.Industrial relevanceThe enzymes PPO and POD are an important concern for vegetable processing, due its ability to induce browning after vegetables are cut. The HPP at 600 MPa for 5 or 30 min can be used to inactivate these enzymes in cocoyam and Peruvian carrot, guaranteeing the color and freshness of the tubers similar to the fresh cut vegetable.     

High pressure thermal processing of pears: Effect on endogenous enzyme activity and related quality attributes

The effect of high pressure-thermal (HPT) processing (600 MPa, 20–100 °C) on the activity of pear enzymes and related quality attributes was investigated. HPT processing at 20 °C for 5 min resulted in 32%, 74% and 51% residual activities of polyphenol oxidase (PPO), peroxidase (POD) and pectin methylesterase (PME), respectively. Increasing processing temperature to 40 and 60 °C reduced the level of PPO and POD inactivation, with the maximum residual activities of 64% and 123%, respectively observed after 3-min treatments at 40 and 60 °C. Overall, HPT at 20 to 60 °C had minimal effect on quality, although enzymatic browning was observed upon air exposure. HPT at 80 to 100 °C caused almost complete inactivation of PPO and POD with 90% and 92% inactivation respectively after 3-min processing at 100 °C, which reduced browning upon air exposure. Nevertheless, the lowest texture retention of 22% was observed under this condition.Industrial relevanceThe study examined the effects of combined high pressure thermal processing on quality related pear enzymes and related instrumental quality attributes such as colour and texture. The study enabled identification of processing regimes for enzyme inactivation and quality retention. The excellent quality retention following HPP at 20 to 40 °C makes this condition suitable for ‘fresh-like’ small portion products for immediate consumption after unpacking that do not require complete PPO and POD inactivation. On the other hand, the almost complete inactivation of oxidative enzymes PPO and POD at 100 °C makes this condition more appropriate for the production of bulk products for food service applications or pureed ingredients for baby food, or pear pieces for yoghurt, that require PPO inhibition but not necessarily high firmness retention.     

Use of response surface methodology to study the combined effects of UV-C and thermal processing on vegetable oxidative enzymes

The combined thermal (25–65 °C) and ultraviolet processing (UV-C) effects on lipoxygenase (LOX), peroxidase (POD) and polyphenoloxidase (PPO) at different pH values (4.0–7.0) were studied using a central composite design. An initial screening design revealed that all factors had a significant effect on enzymatic activity except wavelength which showed a negligible effect. A synergistic effect was found between temperature and UV exposure time for POD and PPO and between pH and exposure time for LOX. LOX enzyme was affected by acidic conditions. POD was UV-C labile whereas PPO was the most UV-C resistant enzyme but was thermolabile. Second-order polynomial equations indicated that enzyme activities were inactivated after exposure to 58.2 mJ/cm² UV at 60 °C or higher temperatures at any pH condition. Combination of UV and thermal processing allowed the use of low energy/doses to obtain complete enzymatic inactivation. This study may serve as a basis to design UV-C processes for the inactivation of enzymes in liquid matrices.     

超高静压对非浓缩还原杨梅果汁中氧化酶的钝化作用

该研究以非浓缩还原（not from concentrate,NFC）杨梅果汁为研究对象,研究不同超高静压（high hydrostatic pressure,HHP）处理（300~600 MPa/0~30 min）对NFC杨梅汁中多酚氧化酶（polyphenol oxidase,PPO）和过氧化物酶（peroxidase,POD）的影响。对比传统高温灭酶,拟合建立HHP压力与酶活性的一级动力学回归方程,分析得到相关参数（压力脉冲效应PE、压力脉冲数值ND、等效破坏值Dp及酶的失活速率K）。结果表明,较高压力（400~600 MPa）对PPO与POD均起到钝化效果,其中600 MPa/10 min能钝化90%的PPO活性,600 MPa/20 min钝化80%的POD活性。600 MPa/30 min条件下,重复加压不能明显加强钝化效果。将PPO和PPO活性与压力进行一级动力学拟合,得到相应线性回归方程（R2>0.8）。随着压力从300 MPa升高到600 MPa,PPO的K值从3.03×10-2升高到12.12×10-2,POD的K值从1.23×10-3上升到7.67×10-3。600 MPa条件下,PPO和POD的ND分别为1.04和1.59,Dp值都为19。同时,压力和保压时间及其相互作用对PPO和POD活性的影响均有极高的显著性（p<0.001）。因此,HHP对杨梅果汁中关键的氧化酶能起到较好的钝化作用,能够为NFC杨梅汁加工技术的应用提供科学依据。     

感应电场处理后蓝莓泥酶活性及总花青素含量变化

为了避免食品电场加工中因电极使用而产生电化学反应造成食品污染和电极腐蚀的问题,采用交变磁通代替电极作为激励源,在果泥料液中诱导形成感应电场(induced electric field,IEF),实现对蓝莓果泥的IEF处理:分析激励电压、温度和时间对蓝莓果泥多酚氧化酶(polyphenol oxidase,PPO)和过氧化物酶(peroxidase,POD)活性及总花青素含量的影响。结果表明,100 V激励电压产生的IEF可减缓PPO和POD酶活的受热损失。150和250 V激励电压下,IEF与高温钝化PPO和POD具有协同作用。IEF可提高花青素分子的热稳定性且电场强度越高稳定作用越强。与未处理果泥相比,经85℃、250 V激励电压的IEF处理30 min的果泥总花青素含量得到最大提升(12. 55%),PPO和POD可被完全灭活。该条件下获得的蓝莓果泥表观黏度与鲜榨果泥更为接近,且储藏期内(4℃,8周)的菌落总数维持在1 lg(CFU/mL)以下,显著低于常规热处理(0 V)和未经热处理的果泥。研究为蓝莓果泥的IEF处理提供了数据参考。     

Combined effect of temperature and pulsed electric fields on apple juice peroxidase and polyphenoloxidase inactivation

Pulsed electric fields (PEF) were applied to freshly prepared apple juice using a laboratory scale continuous PEF system to study the feasibility of inactivating peroxidase (POD) and polyphenoloxidase (PPO). Square wave PEF using different combinations of electric field strength, pre-treatment temperature and treatment time were evaluated in this study and compared to conventional pasteurisation (72 °C; 26 s). Inactivation curves for the enzyme were plotted for each parameter and inactivation kinetics were calculated. Results showed the highest level of decrease in the enzymatic activity of 71% and 68%, for PPO and POD, respectively, were obtained by using a combination of preheating to 50 °C, and a PEF treatment time of 100 μs at 40 kV/cm. This level of inactivation was significantly higher (P < 0.05) than that recorded in juice processed by conventional mild pasteurisation where the activity of PPO and POD decreased by 46% and 48%, respectively. The kinetic data for the inactivation of both enzymes could be described using a 1st-order model (P < 0.001).     

超声波、紫外线、超声波联合紫外线对鲜切香菇多酚氧化酶与过氧化物酶的钝化及其机理研究

酶促褐变是影响鲜切蔬菜质量的重要因素之一。本文对比研究了单一紫外线、单一超声波、超声波联合紫外线处理对鲜切香菇中多酚氧化酶(PPO)与过氧化物酶(POD)的抑制效果,通过酶的紫外光谱、二级结构含量以及X衍射光谱分析,初步探讨了作用机理。结果表明:超声波处理和超声波联合紫外线处理能够有效钝化PPO与POD活性;在超声功率密度70 W/L、双频超声20 kHz与40 kHz顺序工作15 min,PPO和POD相对酶活分别为30.6%和44.3%;紫外剂量为1.8 kJ/m²处理后,PPO和POD相对酶活分别为66.5%和60.8%;在上述超声参数和紫外剂量联合处理后,PPO和POD相对酶活分别为31.0%和46.2%。紫外光谱表明,超声波、紫外线或超声联合紫外线处理后,酶分子C端的疏水性基团发生暴露。二级结构含量分析和X-衍射图谱表明,POD与PPO失活的原因在于α-螺旋、无规则卷曲含量的上升,β-折叠含量的减少,以及酶分子三维构象和衍射峰强弱的改变。本文能够为鲜切果蔬的钝酶提供理论依据和参考借鉴。     

高浓度二氧化碳气调包装通过调节酚代谢抑制鲜切莲藕的酶促褐变

鲜切莲藕褐变的主要原因是酶促褐变,高浓度CO_2气调包装(Modified-atmosphere packaging,MAP)可以有效延缓鲜切果蔬褐变,而苯丙氨酸解氨酶(L-phenylalanine ammonia-lyase,PAL)、多酚氧化酶(Polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)的编码基因是引起果蔬褐变的主要基因。然而,高浓度CO_2 MAP对鲜切莲藕片PAL、PPO、POD酶及其编码基因表达的影响却鲜有报道。本文分析了100%CO_2MAP对鲜切莲藕贮藏过程中褐变度、总酚含量、PAL、PPO和POD酶活性及其编码基因表达的影响。结果表明:100%CO_2 MAP对延缓鲜切莲藕褐变有较好效果,且100%CO_2 MAP贮藏期间鲜切莲藕PAL、PPO和POD酶活性随褐变程度的增加而同步变化。此外,Nn PAL1,Nn PPOA和Nn POD2/3的表达变化与PAL,PPO和POD酶活性的变化及褐变相一致,说明高浓度CO_2 MAP可能通过下调Nn PAL1,Nn PPOA和Nn POD2/3的表达来延缓鲜切莲藕褐变。     

The role of polyphenol oxidase and peroxidase in the browning of water caltrop pericarp during heat treatment

The mechanism of browning involving enzymatic browning was investigated in the pericarp of water caltrop, an Asian vegetable popular for its taste and medicinal properties. Polyphenol oxidase (PPO) and peroxidase (POD) activities were determined in pericarp at various times and temperatures. Water caltrop consisted of 44.22% moisture content, 37.23% crude fibre, and 2.63% crude protein. PPO and POD activities dropped from 62 and 38 units/g sample, respectively, as water temperature was increased from 30 to 80 °C. Optimum pH and temperature for PPO activity was at pH 5.0, 25–45 °C, and POD activity peaked at 60 °C. High PPO and POD activities at 40–50 °C resulted in degradation of phenolic compounds, which led to increased aggregation of browning pigments and discolouration (lower L-values) of the pericarp. Enzymatic browning was determined as the major factor in the browning discolouration of heat-treated water caltrop pericarp.     

Cold plasma enzyme inactivation on dielectric properties and freshness quality in bananas

Cold plasma (CP) technology is a novel, non-thermal method to inactive enzymes and improve the quality of food materials. In this study, banana samples were processed via CP treatment for different lengths of time (1, 1.5, and 2 min intervals) and their properties, including dielectric properties, enzyme activities, levels of ROS (reactive oxygen species), enzymatic browning products, color, flavor compounds, and surface microstructure, were measured. The dielectric constant (ε′) and loss factor (ε′′) after CP treatment decreased with increasing frequency and increased with increasing temperature, respectively. Higher values of ε′ and ε′′ could also be found after CP treatment. The enzyme activity of polyphenoloxidase (PPO) and peroxydase (POD) decreased with increasing CP treatment time. ROS levels in cells increased after CP treatment, and quinones generated from enzymatic browning decreased at extended treatment times. CP treatment had a positive effect on the surface color of bananas due to enzyme inactivation, while significant differences in a^⁎ and b^⁎ values at different treatment times were noted. However, surface morphology changed with increasing CP processing time, leading to a rougher surface microstructure. CP treatment has little impact on flavor compounds and has demonstrated a potential pretreatment technology for dielectric heating/drying.     

Pre-drying treatment of plant related tissues using plasma processed air: Impact on enzyme activity and quality attributes of cut apple and potato

During post-harvest processing of fresh cut and dried fruits and vegetables, polyphenol oxidase (PPO) and peroxidase (POD) need to be inactivated or inhibited in order to avoid undesirable browning reactions and loss of sensorial or nutritional quality. To meet this goal, the application of plasma processed air (PPA) offers a promising “gentle” alternative to traditional methods, such as pasteurization or the addition of anti-browning compounds. Using ambient air as process gas instead of an expensive noble gas, such as argon, exhibits a substantial improvement for the development of large-scale plasmas at ambient pressure and allows the indirect treatment of larger goods within a remote exposure reactor. In this study the ability of PPA to inactivate PPO and POD in complex food matrices and its impact on quality parameters, such as color, texture and cell integrity directly after freshly cutting and during storage of warm air dried and freeze dried produce was evaluated.The study evidently shows that PPA processing is capable of reducing the activity of PPO and POD in the freshly cut tissue from both apple and potato. Following exposure to PPA for 10 min the PPO activity was reduced by about 62% and 77% in fresh cut apple and potato tissue, respectively. POD, as the more temperature-stable enzyme, was even less stable upon PPA treatment for 10 min and was reduced by about 65% and 89% in fresh cut apple and potato tissue, respectively. Blackening of the potato tissue could be completely prevented by plasma treatment while a browning different from the habitual nature of enzymatic browning occurred upon exposure of the apple tissue to PPA. In both cases, the pH value on the tissue surface dropped to 1.5 while cell integrity and dry matter content were not significantly affected.Industrial relevanceThe quality and shelf life of freshly cut and dried fruits and vegetables greatly depend on the activity of naturally occurring enzymes which catalyze browning reactions at cut surfaces. This study shows that the application of PPA, as a promising nonthermal “pasteurization” technology, enables the inactivation of PPO and POD in complex food matrices. It further describes the impact of the PPA treatment on quality parameters of the freshly cut tissue from apple and potato and goes beyond on evaluating color, texture and enzyme activity in warm air dried and freeze dried tissue over a storage time of three weeks. The results contribute to the understanding and product-specificity of PPA-induced effects on quality and shelf life of fresh cut and dried fruit and vegetable produce and could be a basis for a possible industrial implementation.     

贝莱斯芽孢杆菌处理对厚皮甜瓜保鲜效果及保护酶活性的影响

为探究生防菌处理对厚皮甜瓜保鲜效果和保护酶活性的影响,本研究选用西州蜜25号厚皮甜瓜作为研究对象,通过在25 ℃和4 ℃条件下在厚皮甜瓜表面接种贝莱斯芽孢杆菌BG-2,测定贮藏期间拮抗菌在厚皮甜瓜表面定殖特性、保鲜效果和厚皮甜瓜过氧化物酶（Peroxidase,POD）、多酚氧化酶（Polyphenol oxidase,PPO）和苯丙氨酸解氨酶（Phenylalnine ammonialyase,PAL）活性的变化。结果表明,在25 ℃和4 ℃条件下,拮抗菌在厚皮甜瓜表面定殖数量均呈现先上升后下降的趋势且能稳定定殖。接种拮抗菌的厚皮甜瓜腐烂效果、抑制pH和可溶性固形物含量的下降显著优于对照组（P<0.05）。POD和PAL活性呈现先上升后下降的趋势,PPO活性在室温下呈现先上升后下降趋势,在低温下呈现缓慢上升趋势。25 ℃下,拮抗菌处理组POD在第20 d时酶活最高,PAL和PPO在第10 d时酶活最高;4 ℃下,拮抗菌处理组POD和PAL在第20 d时酶活最高。PPO处理在第40 d时酶活最高。且拮抗菌处理过的厚皮甜瓜酶活始终高于病原菌处理组。在25 ℃和4 ℃贝莱斯芽孢杆菌BG-2均能在厚皮甜瓜表皮上稳定定殖,抑制贮藏期厚皮甜瓜腐烂,延缓pH、可溶性固形物、POD、PPO和PAL酶活性下降,且BG-2和低温相结合对上述效果更好。本研究为延长新疆厚皮甜瓜贮藏期提供理论依据,为生防菌作用在厚皮甜瓜采后保鲜提供技术支持。     

Inactivation kinetics and secondary structural change of PEF-treated POD and PPO

Effects of pulsed electric fields (PEF) on the activity of peroxidase (POD) and polyphenol oxidase (PPO) in buffered solution were studied while the corresponding changes to their secondary structures was demonstrated by far-UV Circular dichroism (CD). The relative residual activity of POD and PPO decreased with the increase in electric field strength and treatment time, and PPO was more susceptible than POD to PEF treatment. The greatest reduction of the activity was achieved for POD at 25 kV/cm for 1740 μs and PPO at 25 kV/cm for 744 μs with reductions of 32.2% and 76.2%, respectively. The inactivation kinetic parameters D-value and Z_E value were calculated. The D-values of PPO were smaller than those POD at higher electric field strength, and Z_E values of POD and PPO were 36.9 and 16.2 kV/cm, respectively. The secondary structures of the two enzymes were changed following treatment by PEF. The intensity of negative peaks in the CD spectra decreased, and the CD spectra of PPO changed more significantly than that of POD; the reduction of the relative α-helix fractions for POD at 25 kV/cm for 124 μs was 22.63% while it was 50.72% for PPO at 25 kV/cm for 52 μs. The inactivation of PEF-treated POD and PPO was in close agreement with their secondary structure changes.     

High pressure and thermal inactivation kinetics of polyphenol oxidase and peroxidase in strawberry puree

The objective of this work was to study the thermal and high pressure inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in strawberry puree. PPO from two strawberry cultivars (‘Festival’ and ‘Aroma’) was found to be highly thermostable in strawberry puree with no significant inactivation even after 30 min treatment at 100 °C. In contrast, POD from the two cultivars displayed very high thermosensitivity with complete inactivation in less than 5 min at 70 °C. The thermal inactivation kinetics of strawberry POD was described by a biphasic model. The activation energies for the inactivation of the stable and the labile fractions were estimated to be 254.9 and 221.6 kJ/mol respectively. Combined high pressure–thermal treatment at pressures ranging from 100 to 690 MPa, temperatures ranging from 24 to 90 °C and treatment times between 5 and 15 min did not have significant effect on PPO while substantial inactivation of POD was observed. The inactivation kinetics of POD during combined high pressure–thermal processing was well described by first-order kinetics probably due to the inactivation of the labile fraction during the pre-heating and the compression phase.Industrial relevanceThe oxidative enzymes polyphenol oxidase and peroxidase cause the degradation of anthocyanins and other polyphenols in strawberry products, leading to discoloration and loss of antioxidant activity. In this work the thermal and high pressure inactivation of strawberry polyphenol oxidase and peroxidase was investigated so as to assess the suitability of high pressure processing as an alternative to thermal processing. Strawberry polyphenol oxidase was found to be highly resistant to both thermal and high pressure inactivation. Thus in order to maintain the quality of processed strawberry products, high pressure processing should be accompanied by additional measures such as exclusion of oxygen, refrigerated storage and the use of natural enzyme inhibitors.     

Inhibitory effect of unheated and heated d-glucose,d-fructose and l-cysteine solutions and Maillard reaction product model systems on polyphenoloxidase from apple. I. Enzymatic browning and enzyme activity inhibition using spectrophotometric and polarographic methods

To demonstrate whether caramelization products (CP) and Maillard reaction products (MRP) could inhibit enzymatic browning and/or inactivate apple polyphenoloxidase (PPO), l-cysteine, d-glucose, d-fructose aqueous solutions and equimolar mixtures (1 M) of hexose/cysteine were each tested on purified enzyme activity, using both spectrophotometric and polarographic methods. Inhibition was evaluated as a function of temperature (80–110 °C), time (0–48 h) of heating and concentration of reactants. High (1–2.7 M) concentrations of hexoses were needed to develop a slight inhibiting effect on PPO activity. Heating at 90 °C for extended time periods, increased their inhibitory effect. Unheated or heated cysteine solutions exhibited an inhibitory effect in terms of browning intensity, without noticeably affecting PPO activity. Conversely, MRP showed a very strong inhibitory potency. Inhibition efficiency increased with heating time and temperature. The extent of inhibitory effect was positively correlated with absorbance measurements of MRP at 350 nm, used as an indicator of the Maillard reaction development.     

Effect of ripening on protein content and enzymatic activity of Crimson Seedless table grape

The evolution of °Brix, protein content, polyphenoloxidase activity and peroxidase activity during the ripening of Crimson Seedless table grape was studied in three consecutive years (2006, 2007 and 2008). The total protein content was determined according to Bradford’s dye binding method, and polyphenoloxidase (PPO) and peroxidase (POD) were extracted using Triton X-114 and characterised using spectrophotometric methods. The year had a statistically significant effect on all the studied parameters and there was an interannual correlation in the evolution of protein, PPO, POD and °Brix. All the studied parameters were statistically correlated, except POD activity with protein content. Weather conditions during the ripening period had a greater effect on protein content than PPO and POD activity.     

Inhibition of enzymes and Pseudomonas tolaasii growth on Agaricus bisporus following treatment with surface dielectric barrier discharge plasma

In this study the applicability of cold plasma, produced by surface dielectric barrier discharge (SDBD), to inactivate Pseudomonas tolaasii (P.tolaasii), polyphenol oxidase (PPO) and peroxidase (POD) enzymes, as well as its impact on quality parameters such as, color, texture, pH and weight loss were evaluated. The study evidently shows that treating with combination of 30% hydrogen peroxide vapor)with flow rate of 0.47 mL min⁻¹) and argon (H₂O₂ + Ar) for 180 s is capable of reducing the activity of PPO (0.17 U min⁻¹ g⁻¹ FW) and POD (0.21 U min⁻¹ g⁻¹ FW) and increasing the SOD enzyme (16.29 U g⁻¹ FW) in a 21-day storage period compared to control samples. This is while the quality characteristics of button mushroom are preserved during storage after such treatment.Industrial relevanceThis study provides information of A. bisporus storage during 21-day period after SDBD plasma treatment, which is rarely. Greater inactivation of P. tolaasii after 180 s treatment with combination of hydrogen peroxide vapor and air (H₂O₂ + air) was shown compared to control samples, but this treatment caused also slightly degradation of button mushroom color. A better reduction of PPO and POD enzyme activity as well as further increase of SOD enzyme activity was observed following treatment with 180 s of H₂O₂ + Ar gas in a 21-day storage period. This research work contributes to the understanding SDBD plasma induced effects on the shelf-life of button mushroom and could be a basis for a possible industrial implementation.     

冻干荔枝前处理的酶促褐变控制研究

以怀枝荔枝为研究对象,研究了几种预处理方法对荔枝果肉中多酚氧化酶(PPO)和过氧化物酶(POD)活性的影响。结果表明,1mmol/L的谷胱甘肽溶液浸泡降低了PPO和POD活性,但并未使其失活;同样浓度的谷胱甘肽溶液和抗坏血酸溶液真空浸泡(真空度为0.08MPa)也不能使PPO和POD失活;90℃热烫3min以上可以使POD失活;采用0.3%的抗坏血酸溶液在90℃热烫3min以上可以使PPO失活,通过对热烫后冻干荔枝的色泽和脆度测定,确定最佳预处理条件为0.3%的抗坏血酸溶液90℃热烫5min。