不同品种菊芋总酚含量、PPO活性、POD活性及其与褐变的关系

对5个菊芋品种的总酚含量、PPO活性、POD活性与褐变强度进行了测定。结果表明：不同菊芋品种的总酚含量、PPO活性、POD活性与褐变强度差异显著,其中3个北方品种的各项指标均高于2个南方品种。相关性分析显示,4个外形呈不规则瘤形品种的PPO活性与褐变强度之间呈显著正相关,相关系数r=0.982。褐变主成分分析表明：PPO活性、POD活性和总酚含量这3个变量共同影响菊芋的褐变。     

双孢蘑菇易褐变菌株的多酚氧化酶特征

采用凝胶电泳等生化技术探讨了蘑菇易褐变菌株的酚酶特征。发现易褐变菌株具有特异的同工酶表型,子实体阶段表达的酚酶位点多,且酶活性高;其整个生活史的胞内酚酶活性曲线变化与优质菌株不同;所表达的酚酶对亚硫酸盐类酚酶抑制剂的敏感性低;所表达的酚酶较耐热,在加热的初始阶段(35～40℃)就能迅速催化褐变反应;所含的潜伏型酚酶含量大,且随着鲜菇贮藏期延长而大量活化,继续催化褐变。本文还就如何防止褐变进行了探讨。     

用8-羟基喹啉硫酸盐防止梨、苹果外植体褐变

以金花梨（PyrusbretschneideriRehd．）、金冠（MaluspumilaMill．）和富士（M.pumilaMill．）苹果2～3mm茎尖为外植体,用8-羟基喹啉硫酸盐（8－Hydroxy－Quinolinol－Sulfate,8－HQS）进行处理后,接种在MS＋2．0mg·1-1BA＋0．2mg·1-1IBA培养基上,结果表明,外植体接种后用0．1％的8-HQS淹没24h,然后再将外植体转移至新鲜培养基上,能有效地防止金花梨和金冠苹果外植体褐变（褐变率65％～75％）;外植体消毒前用0．1％的8－HQS预处理24h与接种后用0．1％的8－HQS处理24h对防止富士和金冠苹果外植体褐变具有同样效果（褐变率50％～85％）;金冠与富士苹果外植体消毒前用0．1％和1．0％的8－HQS预处理12h与24h褐变率差异不显著（相差0．6～1．0个百分点）,建议用1．0％的8－HQS预处理12h。     

一品红愈伤组织诱导·增殖及悬浮系建立的研究

[目的]为一品红原生质体融合及遗传转化等相关研究奠定基础。[方法]以一品红品种"喜庆红"的顶芽和带芽茎段为外植体,进行愈伤组织诱导、增殖及悬浮系建立的研究。[结果]以浓度0.1%升汞处理顶芽和带芽茎段的时间分别以6 min和10 min为宜。在MS固体培养基里分别添加活性炭、PVP和Vc后,愈伤组织在培养过程中褐化程度有所减轻,但与对照相比差异并不显著。[结论]一品红愈伤组织悬浮系的适合继代周期为7~8 d。     

普通丝瓜耐褐变研究进展

普通丝瓜在运输、加工过程中果皮、果肉易发生褐变,严重影响其商品价值。从褐变的生理生化机理、耐褐变品种的选育、耐褐变的遗传研究3个方面对丝瓜耐褐变的研究进展情况进行了概述,以期为普通丝瓜耐褐变育种工作提供理论依据。     

Combined effects of glucose oxidase,papain and xylanase on browning inhibition and characteristics of fresh whole wheat dough

In this study, a glucose oxidase (GOX), papain and xylanase combination was developed for fresh whole wheat dough for both browning inhibition and rheological improvement. Measurements of carotenoids extracted from enzyme-treated doughs showed that 0.001% (w/w) GOX could catalyze the oxidization of 40.0% carotenoids and thus cause a decrease of browning index (BI) by 5.20 during dough preparation. For 24 h browning inhibition, 0.010% (w/w) xylanase and papain individuals were able to separately act on the phenolic compounds and polyphenol oxidase, leading to lower BI rises (5.36 and 7.04, respectively) of doughs as compared to the BI rise (13.53) of the control dough; however, 0.020% GOX caused a higher BI rise (16.60) than control although it made BI decrease by 6.34 at 0 h. Rheological investigations on enzyme-treated doughs revealed that both xylanase and papain led to decreases of elastic (G′) and viscous modulus (G″) of doughs while GOX caused increases of G′ and G″. Therefore, an optimal combination composed of 0.010% (w/w) xylanase, 0.005% (w/w) papain and 0.002% (w/w) GOX was carried out using orthogonal experimental design by comparing BI rises in 24 h, which was also proved as a rheological improver for fresh whole wheat dough.     

玉米幼胚组织培养褐化发生因素的研究

以5个不同基因型玉米为材料,对影响玉米幼胚组织培养褐化发生的因素进行了初步研究。结果表明,基因型不同的材料发生褐化的程度不同。参试材料以沈农糯玉米和白糯1号褐化率较低;培养基添加20 g/L甘露醇后褐化率由高于30%降到10%以下;培养温度为24~25℃时,幼胚褐化率最低。     

The effects of nitric oxide and nitrous oxide on enzymatic browning in longkong (Aglaia dookkoo Griff.)

The effect of nitric oxide and nitrous oxide on pericarp browning of longkong fruit was studied. The fruit was either dipped for 5 min in 0.25 mM sodium nitroprusside (SNP), a nitric oxide donor, or continually exposed to 90% nitrous oxide (N₂O) vapour for 3 h and was compared to the untreated fruit (control). The fruits were then stored at 13 °C and RH of 90 ± 5%. The fruit treated for 3 h with nitrous oxide vapour had delayed pericarp browning with higher phenolic compounds. However, these fruit showed lower levels of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase than the control fruit and those treated with 0.25 mM SNP. Therefore, we conclude that nitrous oxide delays browning and reduces the activities of browning enzymes in longkong pericarp.     

鸭梨采后果肉 LOX 同工酶变化及其与果实褐变关系的研究

以河北鸭梨为试材,通过鸭梨果实褐变指数和果肉LOX同工酶变化的测定,研究缓慢和急速2种降温处理对不同成熟度鸭梨果肉褐变情况和LOX同工酶活性的影响。结果表明,果实褐变严重程度为：晚采果＞早采果＞中采果,急速降温＞缓慢降温,因此,鸭梨的最佳储藏方法为中采鸭梨（9月中旬）采用缓慢降温处理。鸭梨果肉中LOX同工酶有9条,急降温和缓降温处理对不同成熟度鸭梨果实LOX同工酶表达有一定的影响。急速降温处理比缓慢降温的LOX同工酶活性高,不同成熟度LOX酶活性大小顺序为：晚采果＞中采果＞早采果,这与褐变指数测定的结果相一致,暗示了脂肪氧合酶与鸭梨果肉的褐变有密切的联系。     

无硫复合护色液对干制红富士苹果片中可滴定酸和可溶性糖含量的影响

[目的]研究红富士苹果干制过程中无硫复合护色液对果片中的可滴定酸和可溶性糖含量的影响。[方法]分别以一定浓度的氯化钠(0.7%)、氯化钙(0.6%)、柠檬酸(0.7%)、EDTA-2Na(0.16%)、异抗坏血酸钠(1.3%)和复合护色液(氯化钠1.0%、氯化钙0.6%、柠檬酸0.9%、EDTA-2Na 0.16%、异抗坏血酸钠1.6%)浸泡苹果片2 h,取出,沥干,放入恒温干燥箱中干制(60℃),考察不同护色剂对干制苹果片中可滴定酸和可溶性糖含量的影响。[结果]试验表明,不同护色剂均能显著抑制干制果片中的可滴定酸和可溶性糖含量的下降,其中以柠檬酸和无硫复合护色液对果片中可滴定酸含量下降抑制效果最好;以异抗坏血酸钠和无硫复合护色液对果片中可溶性糖含量下降抑制效果最好。[结论]研究认为,无硫复合护色液护色的主要机理是通过抑制果肉中的氧化酶活力和延缓抗氧化酶活力的下降来实现的。