预处理对蓝莓NFC果汁品质和风味的影响

为研究预处理对蓝莓NFC果汁品质和风味的影响,以新鲜蓝莓为原料,探讨热水漂烫和酶解前处理对蓝莓果汁感官品质、过氧化物酶(POD)活性、多酚氧化酶(PPO)活性、出汁率、可溶性固形物、花色苷含量、挥发性香气成分的影响。结果表明:热水热烫可使蓝莓PPO、POD活性显著降低,蒸汽热烫可在60 s内使POD残余酶活力降至7.10%, 80℃热烫2min对蓝莓褐变酶活性的钝化效果最佳,花色苷损失较少,色泽较好;优选果胶酶和纤维素酶按4∶1酶解处理,出汁率高达(81.8±1.5)%,可溶性固形物相比对照组显著提高1.4°Brix,花色苷提高1.92倍;酶解后的果汁香气成分增加,酯类含量增加20%,其中乙酸乙酯、异戊酸乙酯和邻苯二甲酸二丁酯含量增加,同时增加了乙酸异戊酯和苯甲酸乙酯新成分,起到增香的效果。     

蒸汽灭酶工艺在龙眼果肉中的应用研究

对龙眼果肉加工前热烫工艺进行了研究,通过PPO、POD等酶活性指标的检测分析和感官评价,探讨了水煮热烫、蒸汽热烫这两种热烫处理方式对龙眼果肉品质的影响。实验结果表明,适宜的热烫处理工艺(100℃蒸汽热烫2min)能很好地钝化PPO和POD酶活性,同时能最大程度地减少龙眼果肉的生青味和蒸煮味。此外,本实验得到复合护色剂对龙眼的褐变最佳抑制效果的配比是:0.1%柠檬酸+0.1%异抗坏血酸钠+0.05%EDTA-Na2。     

蓝莓混汁加工中的防酶促褐变工艺

蓝莓含有大量的多酚氧化酶（PPO）,在果汁加工过程中易与酚类物质发生酶促褐变反应,影响果汁品质.榨汁前对蓝莓进行防褐变处理可以明显改善蓝莓混汁的品质,本文主要讨论了添加酶抑制剂和蒸汽热烫直接灭酶两种方法及其对果汁品质的影响.榨汁前添加0.05%VC可以抑制PPO与酚类物质反应,但不能使酶完全失活,且不能促进花色苷和多酚类物质的溶出;热烫2 min能使蓝莓的内源性PPO完全失活,防止酶促褐变,并且明显提高了果汁中的花色苷和总酚含量,提高果汁的色泽稳定性.     

热烫方式对百合褐变内源酶及微观结构的影响

以龙山百合为实验材料,采用沸水热烫和蒸汽热烫两种方式,研究热烫处理方式对百合多酚氧化酶 （polyphenol oxidase,PPO）、过氧化物酶（peroxidase,POD）及微观结构的影响。结果表明：鲜百合PPO活力 较POD活力高,其中厚外片（thick outer,TKO）PPO活力最高,薄内片（thin inner,TNI）最低;薄外片（thin outer,TNO）POD活力最高,TNI最低。两种热烫处理方式均可以有效抑制百合PPO与POD活力,并对其交叉横截 面微观结构及近轴面表面微观结构产生影响。在沸水与蒸汽两种热烫处理条件下,百合TNO与TNI的PPO在热烫时 间超过30 s后即失去活力,POD在热烫时间超过60 s后失去活力;百合TKO与厚内片的PPO在热烫时间超过60 s后失 去活力,POD在热烫时间超过120 s后失去活力。百合片经热烫后,其内部淀粉颗粒发生糊化,光滑结构表面逐渐 变得粗糙,颗粒间界面变得模糊;且热烫时间越长,糊化程度越高,当热烫时间为3 min时,百合片内部淀粉颗粒 完全糊化。百合近轴面没有观察到明显的气孔器结构,经热烫后的百合片表面出现了膜状和颗粒状的结构。热烫也 可以使百合片表面更加平整光滑。     

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。     

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。     

杏果脯预处理的烫漂与护色工艺优化

为研究不同护色剂对杏脯L* 值和褐变度的影响,探讨热水烫漂对杏脯感官品质、过氧化物酶（peroxidase,POD）活性、多酚氧化酶（polyphenol oxidase,PPO）活性的影响,以褐变度和L* 值为响应值,利用响应面试验进行优化。结果显示：热水烫漂使杏PPO、POD 活性显著降低,结合酶活及感官评价,90 ℃热烫2 min 为最佳工艺条件;0.60%柠檬酸、0.20%D-异抗坏血酸钠、0.20%L-半胱氨酸为复合无硫杏脯的护色配方,在此条件下L* 值为64.41,褐变度为0.075,结果与预测值相近,可有效抑制杏脯发生褐变。     

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。     

热处理延缓采后龙眼果实果皮褐变及其与酚类物质代谢的关系

龙眼果实采后容易发生果皮褐变,是影响采后龙眼果实品质和货架期最重要的因素。热处理是一种能延缓果蔬衰老、保持贮藏品质的环保型采后物理处理方法。本文探讨热处理对采后龙眼果实果皮褐变和酚类物质代谢的影响。采后"福眼"龙眼果实用50℃热水处理10 min,晾干,用聚乙烯薄膜袋密封包装,置于(15±1)℃下贮藏。贮藏期间定期测定果皮褐变指数、总酚含量、苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)和过氧化物酶(POD)活性的变化。结果表明:与对照果实相比,50℃热水处理10 min可有效降低采后龙眼果实果皮褐变指数,降低果皮PPO和POD活性,提高果皮PAL活性,保持较高的果皮总酚含量。因此认为,50℃热水处理10 min可有效降低采后龙眼果实酚类物质代谢,从而延缓采后龙眼果实果皮褐变的发生。     

抗坏血酸处理对鲜榨莲藕汁酶促褐变和品质特征的影响

研究不同浓度的抗坏血酸(AA)处理对鲜榨莲藕汁酶促褐变和品质特征的影响。分别测定0 (对照组),2,4,6,8mmol/L AA处理后的莲藕汁中褐变度、总酚含量、可溶性醌含量、多酚氧化酶(PPO)活性和过氧化物酶(POD)活性等5个酶促褐变参数以及莲藕汁白度、可溶性固形物、黏度、pH值、蛋白质含量和VC含量等6个品质指标,并对酶促褐变指标和品质指标进行相关性分析。结果表明:与对照组相比,随着AA浓度升高,莲藕汁总酚含量上升,褐变度、可溶性醌含量、PPO酶活、POD酶活下降,白度、黏度、VC含量上升,pH值和蛋白质含量下降,可溶性固形物含量基本维持稳定。相关性分析发现AA处理的莲藕汁总酚含量、可溶性醌含量、PPO酶活、POD酶活等酶促褐变参数与其pH值、白度等品质指标的变化密切相关。综上所述,AA处理的莲藕汁在抑制酶促褐变和维持品质特征方面优于对照组,且研究范围内AA浓度越高,效果越好,酶促褐变与品质密切相关。     

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     

高压均质对NFC水蜜桃浊汁稳定性及品质的影响

本文采用高压均质技术,探究了均质压力（20~40 MPa）及次数（1~2次）对NFC水蜜桃浊汁的混浊度、离心沉淀率、粒径、Zeta电位等稳定性指标和pH、TSS、总酸、固酸比、还原糖、色泽、总酚、V_C等品质指标的影响。结果表明:高压均质（30~40 MPa/1、20~40 MPa/2）可有效提高NFC水蜜桃浊汁的稳定性,离心沉淀率较未处理组下降13.49%~24.22%,平均颗粒粒径由1853.67 nm降至501.10~665.27 nm,绝对Zeta电位值显著提高（P<0.05）。随着均质压力及次数的增加,浊汁中可溶性果胶含量上升,而残存果胶甲基酯酶活力逐渐降低。高压均质后,浊汁色泽显著改善,L*值升高,褐变指数BI值下降（P<0.05）;30 MPa/1下,品质保持最佳,总酚、V_C含量较未处理组显著提高（P<0.05）,而pH、TSS、总酸和固酸比无变化（P>0.05）;随着均质次数增加,pH、TSS、总酚和V_C含量显著降低（P<0.05）,品质下降。高压均质处理可有效提高NFC水蜜桃浊汁稳定性、抑制褐变,并提高总酚、V_C等营养物质含量。     

Inhibition of browning on the surface of peach slices by short-term exposure to nitric oxide and ascorbic acid

The effect of 0.2% ascorbic acid (AA), 5 μM nitric oxide (NO), and the simultaneous use of 0.2% AA and 5 μM NO solutions on inhibiting surface browning of fresh-cut peach slices stored at 10 °C and RH 95% was investigated. The browning index, relative leakage rate, microstructure, total phenol content, and activity of the phenol metabolism-associated enzymes phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) were evaluated. The results indicate that treatment with 0.2% AA, 5 μM NO and simultaneous use of 0.2% AA and 5 μM NO resulted in higher total phenol content, inhibition of PPO and POD activity, reduced membrane permeability and protection of cell microstructure to maintain compartmentation between enzymes and their substrates. In addition, NO increased PAL activity. The causes of inhibition in the browning of peach slices by NO are discussed.     

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).     

不同预处理方式对西兰花等外品热风干燥粉体性质的影响

为明确西兰花等外品热风干燥制粉工艺适宜预处理方式,分别采用蒸汽蒸制、热水烫漂、切小丁的预处理方式制备西兰花等外品热风干燥粉体(the hot air drying powder of broccoli defective product,简称HBD粉),研究了不同预处理方式对HBD粉粉体性质的影响。结果表明:烫漂对HBD粉色泽保持效果最好,V_C保留量较高,但溶解性较差。烫漂10 s粉体流动性较差。烫漂30 s粉体较难吸湿,更利于压片成型和干燥保存;蒸汽蒸制粉体水溶性指数较大。蒸汽10 s粉体平均粒径最小,流动性较差,总糖、还原糖含量最高,吸湿能力最强,达22.8%。蒸汽30 s更利于压片成型;小丁粉体膨胀力、持水力较强。经烫漂10 s、蒸汽10 s预处理的HBD粉适宜作为功能配料添加到食品中或吸附于食品表面,经烫漂30 s、蒸汽30 s预处理的HBD粉体适宜片剂、胶囊等产品剂型加工。     

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。