超高压对胡萝卜-草莓复合汁中酶和微生物的影响

目的：为利用超高压技术加工鲜榨果汁提供依据；方法：采用超高压处理鲜榨胡萝卜-草莓复合汁，发现不同压力、保压时间对复合果汁中POD、PPO和LOX酶的活性及其微生物的致死作用不同；结果：在200，300，400，500，600MPa分别处理20min时，POD最耐压，LOX对压力最敏感，其中600MPa下POD、PPO和LOX分别失活46．15％、52％和77．24％。在400MPa、20min处理的复合汁中大肠杆菌≤3MPN／100mL，细菌总数≤10CFU／mL。     

热处理对哈密瓜汁中3种酶的钝化动力学研究

对热处理后的哈密瓜汁中的3种酶的钝化动力学进行研究,为热处理钝酶效果提供参考.设计热处理(不同温度、不同时间)对哈密瓜汁中过氧化物酶(POD)、多酚氧化酶(PPO)和脂氧合酶(LOX)活性的钝化效果进行研究,并对热处理钝化3种酶的一级动力学方程进行分析.发现温度的增加和处理时间的延长能有效地钝化POD和PPO,LOX酶的活性,一级反应动力学能较好地分析热处理对酶的钝化效果.     

微波处理对哈密瓜汁中酶活性的影响研究

初步研究了微波处理对哈密瓜汁中POD、PPO、LOX酶活性的抑制作用。结果表明,控制微波处理温度不超过48℃时,最优处理组合为微波处理时间40s、微波处理9次、pH值3.5。     

杀菌方式对哈密瓜汁贮藏中品质变化的影响

以哈密瓜汁为材料,研究不同杀菌方式对贮藏过程中其主要理化性质的影响。结果表明,哈密瓜汁经过两种杀菌方式处理后在贮藏过程中,哈密瓜汁的总糖、pH、可溶性固形物、总酚均呈下降趋势;褐变度、可滴定酸和透光率呈上升趋势;其中,微波处理不但对pH、总糖以及总酚的下降起到了显著影响,同时,其还缓解了可滴定酸含量的上升,更有效地抑制了哈密瓜汁中微生物生长以及过氧化物酶(POD)和多酚氧化酶(PPO)的失活。在哈密瓜汁贮藏过程中微波杀菌处理不仅能抑制微生物繁殖,而且能保持好哈密瓜汁风味、色泽和营养成分。     

采前钙处理对冬枣成熟衰老过程中相关酶的影响

以采前经过0.2?Cl2喷洒处理5次的冬枣果实为材料,通过研究果实成熟衰老过程中蛋白质、LOX、SOD、POD和PPO活性的变化,探讨钙对果实成熟衰老的影响。结果表明,采前钙处理降低了冬枣LOX活性,提高了SOD、POD和PPO的活性,提高了冬枣采后抗氧化能力,延缓了冬枣的衰老进程。     

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。     

超声波结合热处理对莲藕多酚氧化酶和过氧化物酶钝化效果研究

以莲藕中多酚氧化酶(PPO)和过氧化物酶(POD)为研究对象,研究超声波结合热处理对PPO和POD残留活力的影响.结果表明:在45℃条件下处理酶液10 min,PPO和POD活力分别为109.8％和104.3％;在0℃、260 W条件下处理酶液10 min,PPO和POD活力分别为80.6％和63.6％,表明超声波处理有一定程度的钝酶效果;在45℃、260 W条件下处理酶液10 min,PPO和POD活力显著降低,分别降低至28.8％和40.7％,表明超声波和热处理在莲藕PPO和POD钝化过程中有协同作用.PPO和POD是影响果蔬褐变的关键酶,试验为莲藕加工过程中防止褐变提供参考.     

热处理对新疆哈密瓜采后贮藏特性的影响

以新疆哈密瓜为研究对象,对哈密瓜进行采后热水处理,测定贮藏中哈密瓜的过氧化物酶(POD)活性、呼吸强度、细胞膜透性、可溶性固形物、硬度。结果表明:50、55、60℃热水处理能够提高哈密瓜呼吸高峰的到来,提高哈密瓜的可溶性固形物,保持果实较高的硬度,提高果实POD活性。且以55℃和60℃热水处理效果最显著。     

1-MCP、乙烯调控杏果采后活性氧代谢酶活性及同工酶电泳的研究

以轮台白杏为试材,使用1μL/L1-甲基环丙烯(1-MCP)和30 mg/kg乙烯利处理,研究25℃贮藏过程中,杏果果肉中超氧化物歧化酶(SOD)、多酚氧化酶(PPO)、过氧化物酶(POD)和脂氧合酶(LOX)的活性变化规律及其同工酶表达变化。研究表明:1-MCP处理组显著地延缓了杏果衰老软化,乙烯利处理加速了杏果衰老软化;经1-MCP处理后的杏果SOD、PPO、POD的酶活均高于对照组及乙烯利处理组。SOD活性比对照组高25.21%(p0.05)、PPO活性比对照组高12.93%(p0.05)、POD活性比对照组高9.96%(p0.05),LOX活性显著低于对照及乙烯利处理组,比对照组低46%(p≥0.05);1-MCP处理组、对照较乙烯利处理的SOD、PPO、POD同工酶表达增强,LOX同工酶表达减弱。随着贮藏时间的增加同工酶条带由清晰变为弥散,同工酶表达随着时间的增加而减弱。1-MCP通过提高活性氧代谢相关酶的活力,减少活性氧的产生,减缓细胞衰老进程,延缓软化,提高杏果的贮藏品质。     

热水处理对哈密瓜采后生理指标影响的研究

以新疆"8501"哈密瓜为试验材料,设定不同水温40、50、60℃和不同时间2、3、4min对哈密瓜分别进行处理,通过预试验得出:处理温度为50℃时效果最佳。主要研究50℃水温处理2、3、4min对哈密瓜采后生理生化的影响。结果表明:不同的热水处理均能降低哈密瓜的腐烂程度,延迟和降低呼吸高峰的出现,能够有效抑制多酚氧化酶(PPO)活性的升高,并且能够提高过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)和超氧化物歧化酶(SOD)在贮藏期间的活性;延缓了哈密瓜后熟及其衰老,有效延长了哈密瓜的贮藏期。其中在50℃水温下浸泡处理3min对哈密瓜贮藏效果最为明显。     

超高压对苹果汁微生物和多酚氧化酶的影响

研究不同处理压力和保压处理时间对鲜榨苹果汁的杀菌和钝酶效果.结果表明,随着处理压力升高和保压时间延长,菌落总数、大肠菌群数和多酚氧化酶活性均下降显著.在压力达到400MPa,保压时间25 min时,菌落总数由9750 cfu/mL降低到80 cfu/mL,降低达2.5个对数,大肠菌群数由30 cfu/mL降低到0cfu/mL,多酚氧化酶活性降低了100％,符合美国FDA鲜榨果蔬汁非热力加工的安全营养要求和国家饮料食品卫生标准.     

超高压技术在鲜榨桃汁加工中的应用

以鲜榨桃汁为原料,分别研究了热处理对其多酚氧化酶(PPO)、过氧化物酶(POD)的灭酶效果影响和超高压对其微生物的灭菌效果影响。结果显示:PPO、POD相对残存酶活随着热处理温度和时间的增加而减小,PPO对热处理的耐受性明显高于POD,最适灭酶条件为75℃1min;菌落总数、霉酵总数和乳酸菌数均随着超高压处理压力和时间的增加而减少,霉菌和酵母菌对超高压的耐受能力明显差于细菌,最适灭菌条件为600MPa10min;按以上最适条件生产的桃汁在1个月贮藏期内达到商业无菌。     

高静压对桃汁杀菌、钝化酶活性的效果

研究在不同处理压力和时间条件下,高静压加工技术对桃汁中微生物(细菌总数、霉菌、酵母菌、大肠菌群)以及酶(多酚氧化酶、果胶甲基酯酶、脂肪氧化酶)的影响。结果表明:经400MPa、5min高静压处理即可完全杀灭桃汁中的微生物;在400MPa和500MPa条件下,桃汁中的多酚氧化酶和脂肪氧化酶的活性出现了不同程度的激活现象,但在600MPa时,随着处理时间的延长,其活性逐渐降低,经30min处理后,分别被钝化了0.7662和0.641。而果胶甲基酯酶在400、500、600MPa条件下,出现了不规律的激活或钝化现象。另外,研究表明在高静压加工前增加漂烫工艺,可以有效杀灭桃汁中的微生物及钝化酶活性。     

Inactivation of peroxidase and lipoxygenase in carrots, green beans, and green peas by combination of high hydrostatic pressure and mild heat treatment

The efficiency of high hydrostatic pressure (HHP) with the combination of mild heat treatment on peroxidase (POD) and lipoxygenase (LOX) inactivation in carrots, green beans, and green peas was investigated. In the first part of the study, the samples were pressurized under 250–450 MPa at 20–50 °C for 15–60 min. In the second part, two steps treatments were performed as water blanching at 40–70 °C for 15 and 30 min after pressurization at 250 MPa and 20 °C for 15–60 min. Carrot POD was decreased to 16% residual activity within the first 30 min at a treatment condition of 350 MPa and 20 °C and then it decreased to 9% at 60 min. When the carrots were water blanched at 50 °C for 30 min after HHP treatment of 250 MPa at 20 °C for 15 min, 13% residual POD activity was obtained. For green beans, the most effective results were obtained by two steps treatment and approximately 25% residual POD activity was obtained by water blanching at 50 °C for 15 min after pressurization at 250 MPa and 20 °C for 60 min. An effective inactivation of POD in green peas was not obtained. For carrots, LOX activity could not be measured due to very low LOX activity or the presence of strong antioxidants such as carotenoids. After pressurization at 250 MPa and 20 °C for 15 or 30 min, water blanching at 60 °C for 30 min provided 2–3% residual LOX activity in green beans. The treatment of 250 MPa for 30 min and then water blanching at 50 °C for 30 min provided 70% LOX inactivation in green peas.     

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.     

Effect of high hydrostatic pressure on the quality-related properties of carrot and spinach

This study was designed to evaluate the potential effectiveness of high hydrostatic pressure (HHP) on the changes in quality-related properties of carrot and spinach as measured by ascorbic acid, carotenoids, phenols, flavonoids, microstructure, enzyme activity, and antioxidant activity. Better retention of ascorbic acid and carotenoids was observed at the carrots and spinaches treated at 100, 300, and 500 MPa for 20 min compared to the thermal processing. The color differences were noticeable at the carrot treated at 500 MPa (ΔE=3.5) and the spinach treated at 100 MPa (ΔE=3.6). The least residual peroxidase (POD) activity was 16.6% at the carrot at 300 MPa. The residual polyphenoloxidase (PPO) activities were decreased in carrot (15.1-6.9%) and spinach (31.1–21.3%) and the amounts of phenols flavonoids were increased with increasing pressure levels, leading to the enhanced antioxidant activity. Therefore, the HHP could be used as an alternative for improving quality of vegetables.

     

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。     

Changes in microorganism, enzyme, aroma of hami melon (Cucumis melo L.) juice treated with dense phase carbon dioxide and stored at 4 °C

The effects of dense phase carbon dioxide (DP-CO₂) treatment of 8, 15, 22, 30 and 35 MPa for 5 min, 15 min, 30 min, 45 min, 60 min at 35 °C, 45 °C, 55 °C, 65 °C on microorganism, enzyme, and aroma compounds in hami melon juice during storage at 4 °C for 4-weeks were investigated. Meanwhile, the color, browning degree, and Vitamin C were also studied. The DP-CO₂ treatment had significant effects on inactivation of microorganism and enzyme. It was indicated that higher pressure caused more inactivation of microbial total count and enzyme activity. When it reached 35 Mpa, 55 °C, 60 min, the microorganism was totally inactivated. The least residual activity of polyphenol oxidase (PPO), peroxidase (POD), and lipoxygenase (LOX) was 25.26%, 38.46 and 0.02% at 35MP, respectively. The restoration of PPO, POD and LOX residual activity after DP-CO₂ treatment was also observed, which was dependent on the pressure level. The aroma compounds were less affected after being treated with DP-CO₂, and the flavor of the melon juice was close to the fresh juice after storage at 4 °C for 4 weeks and did not produced cook off-odor. The changes of lightness L and browning degree A during storage were well fitted to a first-order kinetic model. The Vitamin C concentration decreased by DP-CO₂ processing, but this loss was lower than of the untreated sample.

Industrial relevance

Hami melon is highly appreciated for its nutritional quality and special flavor. The flesh of melon is heat sensitive, the sensitive nutrients, color and aromatic profile will be spoiled greatly or off-odour when it was produced with high temperature treatment. Dense phase carbon dioxide processing (DP-CO₂) is important to find an innovative food process to inactivate the enzyme and microorganism and protect the nutrient and unique flavor. In this study, the data proved that DP-CO₂ processing is a promising non-thermal alternative pasteurization to preserved fresh-squeezed melon juice.     

超高压处理对香蕉果肉多酚氧化酶和过氧化物酶活性抑制的研究

为优化超高压处理对香蕉果肉多酚氧化酶(PPO)和过氧化物酶(POD)的酶活残存率,首先研究压力、温度和保压时间对香蕉果肉PPO 和POD 的酶活残存率的影响,然后采用二次回归正交旋转组合设计试验对工艺进行优化。结果表明,超高压处理香蕉果肉PPO 和POD 的酶活残存率影响因素的主次顺序分别为压力＞温度＞保压时间和温度＞压力＞保压时间;超高压处理香蕉果肉PPO 和POD 的酶活残存率最佳工艺参数为压力480MPa、温度55℃、保压时间10min,在此条件下,PPO 和POD 的酶活残存率分别为0.90% 和3.26%。