低温漂烫对泡菜脆度的影响研究

利用低温漂烫激活果胶甲酯酶活性和果胶酸盐具有不溶性、黏度大的原理,选用萝卜为泡菜原料,在一定钙盐存在的条件下,对萝卜进行低温漂烫处理,探讨泡菜低温漂烫处理的最佳条件.结果表明,低温漂烫处理激活了萝卜中的果胶甲酯酶活性,在一定钙盐存在的条件下,萝卜泡菜的脆度得到了很大提高,且萝卜泡菜保脆的最佳低温漂烫条件为:温度55 ℃,时间20 min.     

果胶甲酯酶可使果蔬保持青脆

据日本专家研究，果蔬组织中存在一种果胶甲酯酶，通过降低装罐过程中烫漂阶段的温度及食品中存在钙原子，可逆转加热处理时的软化效应，激发该酶活性，使果蔬中形成更大的果胶聚合物，使食物的青脆度近于新鲜。研究发现，新鲜果蔬在烫漂过程中失去脆实性，使罐头果蔬降低商品价值，     

果胶甲酯酶的作用机理及在食品加工中的应用

该文综述食品加工中应用较为广泛的果胶酶的一个分类——果胶甲酯酶的作用机理及目前在果蔬汁澄清、果蔬制品改善、低酯果胶制备等食品相关行业中的应用现状,并进行总结,为果胶甲酯酶在食品加工中的深入研究开发及未来应用前景预测提供参考。     

果胶甲酯酶对保持苹果质构作用的研究

从质构、酯化度、水溶性果胶含量三个方面研究了果胶甲酯酶对苹果块质构的保持作用。实验证明,用果胶甲酯酶能有效地保持苹果的质构。由经果胶甲酯酶处理的苹果切块(酶浓度0.4mL／50g水,Ca2 浓度0.2％,pH4.5,在0.09MPa下脱气20s)制成的悬浮饮料,在37℃、RH为50％的环境下放置30d后,其硬度保持率为48.5％,咀嚼度保持率为33.46％;未经该酶处理的样品的相应指标分别为32.5％和16.45％。同时模拟实验也表明,苹果中果胶的酯化度从78.6％下降到48.7％,果胶物质在介质中的溶出率从38.95％下降到15.59％。     

果胶甲酯酶对保持苹果质构作用的研究

从质构、酯化度、水溶性果胶含量三个方面研究了果胶甲酯酶对苹果块质构的保持作用。实验证明,用果胶甲酯酶能有效地保持苹果的质构。由经果胶甲酯酶处理的苹果切块（酶浓度0.4mL／50g水,Ca2+浓度0.2％,pH4.5,在0.09MPa下脱气20s）制成的悬浮饮料,在37℃、RH为50％的环境下放置30d后,其硬度保持率为48.5％,咀嚼度保持率为33.46％;未经该酶处理的样品的相应指标分别为32.5％和16.45％。同时模拟实验也表明,苹果中果胶的酯化度从78.6％下降到48.7％,果胶物质在介质中的溶出率从38.95％下降到15.59％。      

超高压技术对草莓汁果胶甲酯酶钝化作用的研究

研究不同条件超高压处理及超高温瞬时灭菌(UHT)对调配草莓汁果胶甲酯酶(PME)钝化作用的影响。以完成调配的草莓汁为对照,分别考察处理压力、保压时间、协同温度以及处理次数对样品的影响。结果表明,不同超高压处理及UHT处理与对照组相比都能导致PME酶活性降低(p<0.05)。200、400MPa(30℃,20min)处理对PME钝化效果与UHT处理相当,达到一定压力(600MPa)钝化效果明显强于UHT处理;超高压处理时间越长,PME钝化效果越明显;超高压协同温度30~60℃处理对PME钝化无显著差异;超高压处理时间一定,增加处理次数对PME钝化作用不明显。贮藏30d后,不同处理PME酶活性基本无变化。      

不同发酵条件对重组猕猴桃果胶甲酯酶抑制剂表达量的影响

将已在毕赤酵母中成功表达的重组猕猴桃果胶甲酯酶抑制剂为研究对象,通过改变发酵培养时间、培养基装填量及培养基配方,对该重组蛋白的表达量进行研究。最终确定使用BMMY培养基、表达时间为96h、培养基装填量为10%时为最佳表达条件,在最佳表达条件下,该重组蛋白的表达量最高可达0.2g/L。     

保脆处理对泡红辣椒脆度与色泽影响的研究

研究了氯化钙、海藻酸钠两种保脆剂对鲜红辣椒脆度与色泽的影响,同时探讨了经保脆处理泡红辣椒脆度与色泽在腌制贮藏过程中的变化,且在腌制结束后,对成品泡红辣椒进行了感官品质分析。研究结果表明,氯化钙与海藻酸钠两种保脆剂对红辣椒均具有较好的保脆作用;但对于色泽而言,氯化钙对腌制红辣椒色泽有损害作用,海藻酸钠对色泽有一定的保护作用;经正交实验得出,0.4%氯化钙与0.3%海藻酸钠复配处理,所得泡红辣椒的脆度与色泽最优。在腌制贮藏过程中,单一或复配处理对样品脆度均具有较好的保持作用,其中复配组脆度保持最好;而对于色泽而言,单一氯化钙处理使色泽损失较大,单一海藻酸钠处理使色泽略有提高,复配组由于二者综合作用,色泽未有明显变化。感官分析得出各处理组分值均高于86,产品品质均可接受,其中复配组分值最高,产品品质最好。      

高压二氧化碳和超高压对多酚氧化酶和果胶甲酯酶结构的影响

为考察高压二氧化碳(HPCD)和超高压技术钝化多酚氧化酶(PPO)和果胶甲酯酶(PE)活性的机理,采用SDS-PAGE电泳、红外光谱和荧光光谱对处理前后酶蛋白的结构进行比较研究。结果表明：经过不同压强HPCD处理和超高压处理60min后,PPO和PE的活性均随着处理压强的增大而逐渐降低。SDS-PAGE电泳分析显示处理后酶蛋白的肽链不发生断裂,但红外光谱和荧光光谱分析显示酶蛋白的二级和三级结构均发生变化。因此,HPCD和超高压技术通过改变PPO和PE酶蛋白的结构达到钝化酶活性的目的。     

应用果胶甲基酯酶改善番茄酱的粘度

研究了添加果胶甲基酯酶对不同类型番茄酱粘度的影响。结果表明,果胶甲基酯酶对于热破番茄酱具有明显增强粘度的作用,而对于冷破番茄酱作用较弱。热破番茄酱中的果胶在果胶甲基酯酶的作用下成为低酯果胶,并在钙离子的作用下进一步形成交联,从而使粘度提高;而冷破番茄酱中没有果胶(或含量很低),所以果胶甲基酯酶对其粘度没有明显作用。     

The effect of methyl bromide on esterase activity in wheat

Fumigation of wheat with methyl bromide causes a change in the polyacrylamide gel, isoelectric focusing profile of esterase proteins from aqueous extracts of wheat. The significance of this effect is discussed in the light of known reactions of methyl bromide in stored products.     

DCE-01菌株果胶酯酶基因克隆与表达

从麻类脱胶高效菌株DCE-01中克隆果胶酯酶基因并进行原核表达。根据全基因组测序注释结果设计引物,PCR扩增果胶酯酶基因连接到pEASY-E1载体上,导入大肠杆菌进行诱导表达,采用水解圈法进行选择和定量分析。结果表明:克隆出全长1107bp的果胶酯酶基因（GenBank登录号:KC422449）,编码368个氨基酸;该基因表达蛋白质序列的前26个氨基酸为信号肽,前导蛋白的分子量约为39.6ku,成熟蛋白为36.9ku,pI为9.1;基因工程菌株以高度酯化橘子果胶为底物的发酵液粗酶活为1.5IU/mL,是原始菌株DCE-01的22.4倍。本研究成功发掘出果胶酯酶基因,其表达产物果胶酯酶能降解高甲氧基果胶,在低甲氧基果胶制备方面具有重要应用前景。      

Enhanced inactivation of pectin methyl esterase in orange juice using modified supercritical carbon dioxide treatment

The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase (PME), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide (SC‐CO₂). Addition of ethanol to the SC‐CO₂ at 2% (v/v) caused greater inactivation than SC‐CO₂ alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first‐order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC‐CO₂ remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.     

Textural properties of gelling system of low-methoxy pectins produced by demethoxylating reaction of pectin methyl esterase

ABSTRACT:  After deesterification of commercial pectins with a pectin methyl esterase (PME), their gelling properties were characterized using instrumental texture analysis. The final degree of esterification (DE) of the high- and low-methoxy pectins reached approximately 6% after the PME treatment, while deesterification of low-methoxy amidated pectin stopped at 18% DE. Furthermore, DE of high-methoxy pectin was tailored to be 40%, which is equivalent to the DE of commercial low-methoxy pectin. As a result, significant changes in molecular weight (Mw) distribution were observed in the PME-treated pectins. The texture profile analysis showed that PME modification drastically increased hardness, gumminess, and chewiness, while decreasing cohesiveness and adhesiveness of the pectin gels ( P < 0.05). The pectin gel with relatively high peak molecular weight (Mp, 3.5 × 10⁵) and low DE (6), which was produced from high-methoxy pectin, exhibited the greatest hardness, gumminess, chewiness, and resilience. The hardness of low-methoxy amidated pectin increased over 300% after PME deesterification, suggesting that the effects of amide substitution could be reinforced when DE is even lower. The partial least square regression analysis indicated that the Mw and DE of the pectin molecule are the most crucial factors for hardness, chewiness, gumminess, and resilience of gel matrix.     

Pectin methyl esterase treatment on high‐methoxy pectin for making fruit jam with reduced sugar content

BACKGROUND: Pectin methyl esterase (PME) has been postulated to catalyse the transacylation reaction between pectin molecules. The present study aimed to prove the occurrence of this reaction. The feasibility of applying PME‐catalysed transacylation between high‐methoxy pectin molecules in making fruit jam with reduced sugar content was also investigated. RESULTS: PME treatment increased the turbidity and particle size in pectin solution and the molecular weight of pectin, while it decreased the number of methoxy ester linkages and the intensity of the CH₃ absorption peak in the Fourier transform infrared spectrum without changes in the number of total ester linkages in pectin molecules. These findings support the occurrence of PME‐catalysed transacylation between pectin molecules. Higher values of hardness, gumminess and chewiness were found in a jam containing PME‐treated citrus pectin (10 g L^?1) and sugar (350 g L^?1) as compared with either a jam containing untreated citrus pectin (10 g L^?1) and sugar (350 g L^?1) or strawberry jam containing pectin (10 g L^?1) from the fruit and sugar (650 g L^?1). CONCLUSION: The demand for sugar in jam making can be greatly reduced by the use of PME‐treated high‐methoxy pectin. Copyright © 2012 Society of Chemical Industry     

复合防腐剂对袋装萝卜干防腐效果的比较研究

通过对萧山萝卜干中微生物的初步分析、鉴定,确定其微生物主要为蜡样芽孢杆菌。通过防腐剂抑菌实验,得出苯甲酸双乙酸钠复合防腐剂为一种可用于萝卜干防腐的高效防腐剂。     

内源果胶酯酶制备低甲氧基果胶的研究

以新鲜橙皮为原料，在盐酸水解乙醇沉淀提取果胶之前，激活并利用果皮中固有的果胶酯酶进行果胶的酶法脱酯，制备低甲氧基果胶，以产品的甲氧基含量和果胶得率为指标，确定最佳工艺条件。结果表明新鲜橙皮内源酶法制备低甲氧基果胶的最佳工艺条件为：加入果皮浆液量0．15％的内源性果胶酯酶激活剂碳酸钠，控制温度45℃，pH值8．0进行脱酯，时间60min；果胶提取温度90％，时间60min，pH值2．0；在此条件下制备的果胶甲氧基含量为5．93％，符合低甲氧基果胶标准，果胶得率为2．46％。