板栗的酶促褐变特性及灭酶预处理研究

对冻藏板栗中多酚氧化酶（PPO）的活力及热稳定性进行了比较,研究低糖板栗果脯灭酶顸处理及其对后续渗糖过程的影响。结果表明：板栗中影响褐变的酶主要有PPO和POD,其中PPO较POD热稳定性略高。冻藏后的板栗中PPO最适温度及pH分别为20℃和6．5。板栗加工中应以板栗PPO活力降至8％以下作为是否灭酶充分的标准。通过与热水烫漂灭酶、蒸汽灭酶比较发现,微波热烫处理可抑制低糖板粟果脯加工过程中的褐变,并有助于提高渗糖效率。微波炎酶的最佳条件是：功率密度4W／g,处理6min。     

微波烫漂对速冻怀山药品质的影响

采用不同的微波烫漂水平处理怀山药,通过测定过氧化物酶活性、多酚氧化酶活性、失重率、可溶性固形物含量和游离氨基酸总量5项指标,研究微波烫漂对速冻怀山药品质的影响。同时对护色剂处理、热水烫漂、微波烫漂3种不同处理条件下怀山药解冻后的硬度、质地以及感官特性进行比较。结果表明：微波烫漂怀山药短时间内即可达到灭酶效果,而且营养成分损失少,解冻后品质较好。最佳的微波功率及相应的处理时间为407.6W和60s。     

新型果蔬漂烫技术研究进展

果蔬水分含量较高,不易贮藏,采后腐烂变质情况较为严重。干燥可以有效延长果蔬的贮藏期,是果蔬加工常用的方法之一。漂烫是果蔬干燥前的关键步骤,具有灭酶、护色的作用。传统的漂烫方法采用高温热水及蒸汽进行灭酶,对果蔬品质影响较大。近年来科学家们提出并研究了一些新型漂烫技术。本文主要针对在传统漂烫方法基础上改进的一些新技术(超高温瞬时蒸汽漂烫和超声波辅助热漂烫)和新型干法漂烫技术(远红外漂烫、欧姆漂烫、微波漂烫以及射频漂烫),重点介绍其技术原理和应用优势。新型漂烫可提高漂烫效率,其中干法漂烫不采用水为加热介质,水溶性营养物质损失较少,产品品质较好,在工业上应用可降低能耗并减少废水的产生,具有良好的应用前景。本文为后续研究新型果蔬漂烫技术以及开发新型联合干燥技术提供参考。     

脱水黄花菜加工过程中的预处理工艺研究

以黄花菜的主栽品种鲜猛子花为材料,在测定过氧化物 酶及多酚氧化酶活力的基础上,通过对热水、蒸汽及微波 灭酶等灭酶方法的研究,确定了蒸汽漂烫70～80s的最佳 灭酶工艺条件;同时,以护色剂种类、护色剂浓度、浸泡时 间为影响因素,进行了三因素三水平试验,得到了将原料 浸泡在0.5％的柠檬酸溶液中45min的最佳护色工艺。     

微波在刀豆脱水中的应用

本文利用微波技术对刀豆进行脱水处理，微波处理与热水烫漂相比具有维生素Ｃ损失少和灭酶彻底的优点，并且微波干燥比热风干燥的速率快时间短。     

微波烫漂对杏鲍菇POD酶活的影响

研究微波烫漂对杏鲍菇POD酶的灭活效果,并与沸水和蒸汽烫漂两种常规灭酶模式效果进行比较。为获得微波烫漂的优化条件,采用响应曲面分析法建立微波功率和微波时间对POD相对酶活影响的二次多项数学回归模型。结果显示：杏鲍菇最适宜的灭酶条件为微波功率570W,微波时间59s。在此条件下处理的杏鲍菇游离氨基酸含量损失少,感官品质佳。     

微波处理对食用菌烫漂效果的影响

对微波烫漂与常规方法烫漂食用菌的烫漂效果进行了初步探讨，试验结果表明，微波烫漂食用菌不但灭酶效果好，而且在营养成分保留和感观状态等方面明显优于常规烫漂处理。     

干制前处理对切分杏褐变内源酶及色泽的影响

目的：采用4种方式对切分杏干制前进行处理,研究对多酚氧化酶、过氧化物酶及色差的影响,确定切分杏干制前处理的最佳条件。方法：以切分、去核的赛买提杏为材料,探究热水、蒸汽漂烫、微波处理、浸硫处理的杏果内源酶活性、失活率和色差的变化,研究4种最佳前处理条件下对杏果色差（干制前后）的影响,并进行色差各指标间的相关性分析。结果：热水、蒸汽漂烫下酶活性随热烫时间的增加而降低,100℃、90 s为该处理的最佳条件;微波处理下内源酶失活率随功率的增大、时间的延长而增加,最佳条件为50%(350 W),5 min,失活率分别为92.83%、91.05%;浸硫处理下酶失活率分别为98.73%、16.35%。结论：热水漂烫和浸硫处理结合热风干燥在温度为60℃时色泽保持较好,而蒸汽漂烫和微波处理选择40℃为宜。通过相关性分析得出热水漂烫对杏干色泽损伤较大,硫处理可有效保持杏干色泽。     

高温蒸汽瞬时漂烫对黑牛肝菌酶活和品质影响的研究

研究了高温瞬时蒸汽对黑牛肝菌的过氧化物酶(POD)和多酚氧化酶(PPO)活性的影响,并研究了对黑牛肝菌几种重要营养成分的影响,包括总酚、可溶性总糖、VC以及可溶性蛋白。通过时间(s)、物料量(g)、蒸汽压力(MPa)的单因素试验,设计正交试验,对POD、PPO、总酚、总糖、VC、可溶性蛋白进行综合评价分析,得出最佳的试验条件:高温蒸汽瞬时漂烫时间为30 s、物料量300 g、蒸汽压力0.3 MPa,综合评分值最高。高温蒸汽漂烫最优结果与最佳的热水漂烫处理进行比较,体现了高温蒸汽漂烫的优势。     

酶钝化处理对菊苣茎PPO活性和绿原酸含量的影响

通过水浴、蒸汽、微波3 种烫漂方式处理新鲜菊苣茎,钝化多酚氧化酶（PPO）,为提高干燥菊苣茎中绿原酸含量提供依据。烫漂处理后立即测定菊苣茎PPO相对活性,同时测定经烫漂处理后再经空气干燥茎中绿原酸含量,分析二者之间的相关性;测定不进行烫漂处理直接进行空气干燥的菊苣茎在干燥过程中PPO相对活性和绿原酸含量的变化。结果表明：空气干燥过程中,PPO始终保持一定的相对活性（≥20.02%）;水浴、蒸汽和微波烫漂处理可有效抑制PPO相对活性,且在以上3 种处理方式中绿原酸含量与PPO相对活性均呈显著负相关（P＜0.05）;4 种方法处理后风干茎中绿原酸的含量依次为：直接空气干燥＜水浴烫漂后干燥＜蒸汽烫漂后干燥＜微波烫漂后干燥。在实验条件下,微波（600 W）烫漂鲜茎样品4.67 min时,风干菊苣茎中绿原酸含量（8.11 mg/g）最高,与鲜茎相比只降低16.82%,是直接空气干燥茎中绿原酸含量的2.17 倍。     

Effects of hot-water and steam blanching of sliced potato on polyphenol oxidase activity

The worldwide potato production is considered the fourth-most important food sector due to the increasing use of potatoes as raw materials for high-convenience food. Enzymatic browning, due to polyphenol oxidase (PPO), is related to unacceptability by consumer. Among antibrowning agents, thermal treatments are viable alternatives. In this study, the efficacy of hot-water and steam blanching at 80–90 °C of potato slices (1-cm thick) was evaluated in terms of colour changes as well as PPO inactivation kinetics, substrate specificity and transition state parameters. In general, all treatments [1] bleached the slices, [2] inactivated PPO and [3] reduced its kinetic efficiency. Results from thermal inactivation kinetics promoted hot-water blanching at 90 °C for approx. 2 min as the fastest treatment to obtain enzymatic-stable potato slices. Moreover, steam blanching required more energy (53.93 ± 1.24 kJ mol⁻¹) than hot-water treatment (41.41 ± 4.51 kJ mol⁻¹) to reach the transition state and then to unfold the PPO enzyme.     

Improvement of frozen banana (Musa cavendishii, cv. Enana) colour by blanching: relationship between browning, phenols and polyphenol oxidase and peroxidase activities

 Browning in banana (Musa cavendishii, cv. Enana) processed products is a result of phenol oxidation catalysed by polyphenol oxidase (PPO) and peroxidase (POD) or of other non-enzymatic reactions (Maillard and Strecker mechanisms). Microwave and steam blanching significantly reduced PPO and POD activities and phenol levels in banana flesh, steam blanching being the most effective method for enzyme inactivation. Freezing/thawing processes produced a significant increase in phenol levels in all samples, due to cellular breakdown. After microwave heating browning processes occurred while steam-treated samples did not exhibit a significant colour change. Extractable PPO and POD activities in all banana samples increased as a consequence of freezing/thawing: steam-blanched slices exhibited lower residual activities. High correlations occurred between phenols and browning (r=0.86) in control samples. Blanched samples (microwave or steam) only exhibited correlations between PPO (r=0.80) and POD (r=0.80) activities and browning. Received: 22 February 1996     

Improvement of frozen banana (Musa cavendishii, cv. Enana) colour by blanching: relationship between browning, phenols and polyphenol oxidase and peroxidase activities

 Browning in banana (Musa cavendishii, cv. Enana) processed products is a result of phenol oxidation catalysed by polyphenol oxidase (PPO) and peroxidase (POD) or of other non-enzymatic reactions (Maillard and Strecker mechanisms). Microwave and steam blanching significantly reduced PPO and POD activities and phenol levels in banana flesh, steam blanching being the most effective method for enzyme inactivation. Freezing/thawing processes produced a significant increase in phenol levels in all samples, due to cellular breakdown. After microwave heating browning processes occurred while steam-treated samples did not exhibit a significant colour change. Extractable PPO and POD activities in all banana samples increased as a consequence of freezing/thawing: steam-blanched slices exhibited lower residual activities. High correlations occurred between phenols and browning (r=0.86) in control samples. Blanched samples (microwave or steam) only exhibited correlations between PPO (r=0.80) and POD (r=0.80) activities and browning. Received: 22 February 1996     

不同杀菌方式对泡椒鲜切马铃薯片贮藏品质的影响

为解决泡椒鲜切马铃薯片贮藏和流通过程中出现的褐变、胀袋、质地软化等问题,采用蒸汽、微波和辐照杀菌方式对泡椒鲜切马铃薯片进行处理,通过测定L*值、硬度和感官评分,筛选各杀菌方式最优工艺参数。通过贮藏实验,对比不同杀菌方式对泡椒鲜切马铃薯片色泽、质构特性、多酚氧化酶（PPO）活性及菌落总数等指标的影响。结果表明,各杀菌方式的最优工艺参数为蒸汽杀菌时间为3 min,微波杀菌功率为700 W,辐照杀菌剂量为8 kGy。贮藏实验结果表明,辐照和微波杀菌灭酶活效果优于蒸汽杀菌,但蒸汽杀菌能更好地保持产品色泽,减缓L*值的降低,维持产品硬度、弹性和咀嚼性,菌落总数和PPO活性虽比辐照处理组和微波处理组高,但整体控制在较低水平,综合感官评分以蒸汽处理组最高。综合对比,蒸汽杀菌更适合于泡椒鲜切马铃薯片的加工。     

热烫方式对草莓内源酶与主要品质影响的研究

主要研究了不同热烫方式（100。C蒸汽热烫1rain、1．5min、2min,100。C沸水热烫1min、1．5min、2min）对草莓的钝酶效果及主要品质的影响。结果表明,草莓过氧化物酶（POD）相对多酚氧化酶（PPO）热稳定性较强,热烫时间越长酶的钝化效果越好;热烫处理后草莓的色泽更加鲜艳,而可溶性固形物、PH、可滴定酸等变化不显著（P〉0．05）;热烫造成维生素C损失（P〈o．05）,而总酚及花青素含量显著增加（P〈O．05）;热烫处理后草莓的挥发性香气成分中酯类物质种类不变,相对含量增加,典型新鲜草莓香气成分反式--2-己烯醛显著减少（P〈o．05）,蒸汽热烫1mjn及1．5rain仍能保持草莓部分反式--2--己烯醛,热烫时间太长容易造成草莓清新青草风味的减弱。     

热烫处理对南瓜叶化学成分及色泽的影响

为探明热烫处理过程中南瓜叶的品质变化,研究了蒸汽热烫、微波热烫及热水热烫对南瓜叶中VC、可溶性蛋白、叶绿素及草酸含量、过氧化物酶（peroxidase,POD）活性及色泽的影响。结果表明：3 种热烫方法对南瓜叶POD活性均有明显的抑制作用,蒸汽热烫可在60 s内使POD残余酶活力降低至7.10%,热水热烫对POD活性的抑制作用受温度影响较大,在95 ℃以上即对POD活性有明显抑制作用,此温度条件下热烫60 s,POD残余酶活力可降至4.85%;于微波功率480 W条件下热烫50 s,南瓜叶POD残余酶活力降至5.05%;经热水热烫的南瓜叶VC、可溶性蛋白含量最高,其次是微波烫漂,蒸汽热烫的最低;热水热烫的南瓜叶草酸含量亦较低,且L*值最大而a*值最小,即热水热烫的南瓜叶色泽最优。热水热烫是南瓜叶最适宜的热烫方式,其最适宜的烫漂条件为95 ℃、60 s。     

In situ inactivation of polyphenol oxidase in mamey fruit (Pouteria sapota) by microwave treatment

Polyphenol oxidase (PPO) is the enzyme responsible for quality loss in most fruits and vegetables. Quality loss is mainly because of oxidative chemical reactions which generate the darkening of tissues. Mamey fruit (Pouteria sapota) after harvesting suffers a rapid quality decay trough activation of PPO. However, PPO may be inactivated in situ by chemical or thermal treatment. In food processing, microwave treatment (MT) has been used recently as an alternative for PPO inactivation. In this study, it was observed that mamey fruit pulp subjected to a gently MT resulted in a higher PPO activity as the generated heat induced in situ the increase in PPO activity. In contrast, PPO was completely inactivated after long MT by using a high microwave power. Temperature in mamey pulp after MT reached a maximum of 79 °C; although PPO was active up to 60 °C. PPO was completely inactivated when conventional blanching treatment was performed but required a higher temperature (92 °C/300 s). The optimum energy intensity (E(opt)) for PPO inactivation by MT was 0.51 kJ/g or 937 W/165 s. Under this condition, the remaining PPO activity was inversely proportional to energy intensity (E). Interestingly, MT resulted in a negligible damage in microstructure of mamey pulp, although blanching treatment resulted in large damaging effects on tissue organization and shape. Therefore, MT is proposed as an effective way to completely inactivate PPO without causing any significant damage to fruit tissues and shape; as preservation of color, flavor, and taste would be favored.     

Steam blanching effect on polyphenoloxidase,peroxidase and colour of mango (Mangifera indica L.) slices

The heat stability of peroxidase (POD) and polyphenoloxidase (PPO) was investigated in mango (Mangifera indica L.) slices, and the relative colour was studied after different steam blanching times. There was complete inactivation after 5 min for POD and 7 min for PPO. Steam blanching of 3 min gave residual activity of 2.85% and 8.33% for PPO and POD, respectively, and when compared with samples blanched for 5 min had no effect on colour over 20 days of storage. Correlation was found between activities of PPO, POD and colour change over 20 days. After 7 min steam blanching the browning index was stable but less than at 3 and 5 min because non-enzymic browning had occurred. This research suggests that yellowness (b) and lightness (L) values contribute positively to the browning index (BI), compared to redness (a).     

Effects of microwave heating on pigment composition and colour of fruit purees

Microwave energy was applied to inactivate the oxydoreductases peroxidase (POD, EC 1.11.1.7) and polyphenol oxidase (PPO, EC 1.14.18.1) in processed fruit products. Microwave blanching of papaya, strawberry and kiwi purees at various conditions of power and time produced inactivation of PPO and POD activities depending on the fruit and the heating conditions. Treatment at 850 W/60 s produced about 60% of POD inactivation for papaya and kiwi fruit. POD activity in strawberry, however, seemed to be more resistant to microwave inactivation; treatment at 850 W/60 s only achieved a loss of POD activity near 8%. Papaya oxidoreductases showed lower stability in the microwave treatments tested. Microwave blanching at 475 W/45 s produced about 75% inactivation of POD activity and nearly complete PPO inactivation. Kiwi fruit and strawberry purees exhibited similar inactivation of PPO – 32% at 475 W/30 s and 70% at 475 W/60 s. The decrease of PPO activity in both products was almost linear at constant power. This thermal treatment, however, directly affects the colour of the fruit pulps. Papaya, kiwi and strawberry purees suffered slight colour (CIE L* a*b*) changes. Carotenoid, chlorophyll and anthocyanin changes were evaluated by HPLC and related to objective colour. Microwave treatments produced small modifications of the quantitative and qualitative composition of carotenoids (in papaya) and anthocyanins (in strawberry). Chlorophylls (kiwi) showed significant degradation as a consequence of microwave heating. © 1999 Society of Chemical Industry     

甜玉米速冻前热烫工艺研究

对甜玉米速冻前热烫工艺进行了研究,通过PPO、POD等酶活性、可溶性糖和Vc等指标的检测分析和感官评价,探讨了水煮热烫处理、蒸气热烫处理和微波热烫处理等热烫处理方式、热烫处理时间等因素对速冻甜玉米品质的影响。试验结果表明,适宜的热烫处理工艺(蒸气热烫20min)能减少可溶性糖和Vc的损失,同时钝化PPO和POD酶活性,提高速冻甜玉米的品质。