酶法提取苹果皮渣果胶的特性研究

为深入研究苹果皮渣果胶的提取技术,本文比较了盐酸水解法和纤维素酶、半纤维素酶对苹果皮渣果胶的提取效果。采用高效阴离子交换色谱-脉冲安培检测法(HPAEC-PAD)测定可溶性果胶的单糖组分,并通过粘度计测定特性粘度,推导粘均分子量。结果表明,酶法提取的果胶,比酸法提取的得率高2～3倍,且溶解性好．酸法、纤维素酶、半纤维素酶三种方法提取的可溶性果胶粘均分子量分别为292600、122400和165200Da。     

果胶甲酯酶抑制剂的异源表达及其在果酒降甲醇中的应用

该文从猕猴桃中克隆出果胶甲酯酶抑制剂（Pectin Methylesterase Inhibitor,PMEI）基因,经EcoRⅠ/XbaI双酶切后连接到表达载体pPICzαA上,电转化到毕赤酵母GS115筛选出阳性菌株GS115/pPICzαA-PMEI,并将重组酵母表达的PMEI浓缩纯化后应用于果酒发酵。研究结果表明：重组毕赤酵母表达菌株GS115/pPICzαA-PMEI成功构建,PMEI的发酵表达量为35.38 mg/L。将PMEI应用到果酒发酵中,桔子酒甲醇降低47.54%,含量由189.75 mg/L降低到99.55 mg/L;苹果酒甲醇降低21.52%,含量由118.15 mg/L降低到91.20 mg/L;葡萄酒甲醇变化不显著,含量均低于20.00 mg/L,表明PMEI对果胶丰富且内源性果胶酶强的桔子具有明显的降甲醇效果。桔子酒发酵工艺优化的PMEI最低抑制质量浓度8.84 mg/L,最适温度18 ℃,此时桔子酒中的甲醇降低66.40%到89.10 mg/L。这为低甲醇果酒的发酵提供了新的技术路线。     

改性苹果果胶性质及抗氧化活性

以苹果果胶为原料,采用酸碱修饰和高压蒸汽法2种方法分别制备酸碱改性和热改性苹果果胶,并在分析苹果果胶改性前后理化性质的基础上,进一步研究了其体外抗氧化活性。结果表明:酸碱改性和热改性后的苹果果胶与未改性果胶相比:半乳糖醛酸含量由(683.92±4.51)mg/g分别增加到(910.61±1.08)mg/g和(780.19±5.68)mg/g,酯化度由(77.26±1.20)%分别降低到(35.48±1.90)%和(33.67±1.28)%。改性后果胶分子质量降低,多酚和蛋白质含量均较低(分别小于3 mg/g和7 mg/g)。改性前后苹果果胶的1,1-二苯基-2-三硝基苯肼自由基清除率、羟自由基清除率、2,2’-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐自由基清除率和超氧阴离子自由基清除率均随果胶质量浓度的增大而增强,而且酸碱改性更有助于其抗氧化活性的提高,这可能与其半乳糖醛酸含量增加有关。     

Tomato Product Quality from Transgenic Fruits with Reduced Pectin Methylesterase

Juice from transgenic tomato (Lycopersicon esculentum cv Rutgers) fruits with reduced levels of pectin methylesterase (PME) activity due to the expression of a PME antisense gene exhibited improvement in quality. The percentage increase in juice from transgenic fruits over that of juice from wild type Rutgers ranged between 5.1–5.3 for total solids, 3.8–6.1 for soluble solids, 70–80 for efflux viscosity, 180–220 for serum viscosity and about 50 for precipitate weight ratio. Time of harvest had no effect on quality of juice. Ketchup prepared from transgenic fruit juice had a lower Bostwick value, reduced serum separation and high serum viscosity compared to ketchup from parental Rutgers.     

超高压与重组果胶甲酯酶抑制剂联合应用对鲜榨橙汁果胶甲酯酶活性及品质的影响

为了探究超高压与重组果胶甲酯酶抑制剂(recombinant pectin methylesterase inhibitor,rPMEI)联合处理对鲜榨橙汁中果胶甲酯酶(pectin methylesterase,PME)活性及品质的影响,研究了超高压(400、500和600 MPa,5 min,20 ℃)与重组果胶甲酯酶抑制剂对橙汁微生物、PME酶活、色泽和V_C含量的影响。结果表明:超高压处理条件为500 MPa/5 min,rPMEI添加浓度为0.06 mg/mL时,橙汁中的菌落总数、霉菌与酵母菌数均能达到农业行业标准《NY/T 434-2016绿色食品、果蔬汁饮料》所规定的要求,同时PME被完全钝化;橙汁色泽变化显著小于热处理组(ΔE^*=1.22<2.26);V_C保留率为85.1%,显著高于热处理组(保留率=8.33%)。     

Isolation and Characterization of Pectin in Sugar-Beet Pulp

Pectin was extracted from sugar-beet pulp by various solvent fractionation procedures. An optimal HCI-extraction method yielded 19.53% pectin from the raw material. The HCl-isolated pectin contained 81.8% galacturonic acid. The sugar-beet pulp pectin obtained from different extraction procedures had a high methoxy content ( 60% degree of methylation). The pectin also contained 10 to 17.5% neutral sugars which were mainly arabinose and galactose as analyzed by gas chromatography. The peak molecular weights (relative to dextrans) of the pectins as determined by gel permeation ranged from 35,500 to 44,700 daltons. The pectin possessed high water-holding capacity and low viscosity.     

Isolation and Characterization of Invertase from Iraqi Date Fruit

Soluble invertase was isolated and characterized from the pericarp of Iraqi date fruit, Sayer variety. The optimum pH of the soluble invertase was 4.0–4.7 and the optimum temperature was 50°C. The specific activity of the partially purified soluble invertase was 70.0 units per mg protein. The molecular weight of the soluble invertase was 70.0 units per mg protein. The molecular weight of the soluble invertase was probably more than 300,000 Daltons, and had high affinity for sucrose with a Km value of 3.33 × 10^-3 mM. Sodium dodecyl sulfate (SDS) inhibited the activity of the soluble invertase.     

欧李果胶理化特性及乳化性质

以商品苹果果胶（commercial apple pectin,CAP）为对照,研究欧李果胶（Cerasus humilis fruit pectin,CSP）的结构、理化性质及乳化特性。与CAP对比,所得CSP半乳糖醛酸质量分数为70.42%,含有更高含量的金属元素（Ca、Zn、Mg）、蛋白质和总多酚（P＜0.05）。通过扫描电镜、傅里叶变换红外光谱、气相色谱-质谱联用、X射线衍射等结构表征表明,CSP表面呈光滑、连续和卷曲的片状或丝状结构,为高甲氧基果胶（酯化度52.04%）,具有无定形性质,阿拉伯糖（65.7%）、半乳糖（18%）和鼠李糖（11%）为其主要的3 种中性单糖。此外,通过测定CSP的Zeta电位值和其乳液体系的乳化指数、乳化能力、乳化稳定性、显微结构、液滴粒径及流变学性质,探究CSP的乳化性质。结果显示,CSP具有较好的乳化性质,可作为乳液体系的天然乳化剂,具有巨大潜力。     

Kinetics of Tomato Pectin Methylesterase Inactivation by Temperature and High Pressure

ABSTRACT: In this study we investigated the inactivation of endogenous pectin methylesterase (PME) in tomato juice during combined high-hydrostatic pressure (ambient to 800 MPa) and moderate temperature (60 to 75 °C) treatments under isobaric and isothermal processing conditions. PME inactivation rates increased with increasing processing temperature, with the highest rate obtained during processing at 75 °C and ambient pressure. Inactivation rates were dramatically reduced as soon as processing pressure was raised. High inactivation rates were again attained when processing pressure exceeded a value of about 700 MPa. Such a behavior was described by considering two parallel mechanisms of inactivation, each one following first order kinetics with its own kinetic parameters.     

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。     

微波辅助提取苹果皮中果胶的研究

讨论利用微波辐射萃取法从苹果皮中提取果胶的不同因素的影响,通过实验确立微波条件下提取果胶的最佳工艺条件为:用盐酸调pH为1.8,用水作为溶剂,料液比为1∶20(g/mL),微波辐射功率为600 W,辐射时间为4 min,乙醇浓度为60%,提取率可达到12.9%。     

Extraction and Characterization of Pectin from Apple (Malus Pumila. Cv Amri) Peel Waste

Abstract

Apple peel, the major waste in preserves manufacturing, contained 1.21% pectin. Peel waste could be stabilized with 600 ppm sulphur dioxide and 1% citric acid. Pectin extraction was better in citric acid than hydrochloric acid. The pectin powder was prepared by triple extraction with citric acid solution (1%) clarification through sedimentation, concentration (24°B), precipitation using ethyl alcohol, vacuum drying and grinding. Physico-chemical properties of pectin powder revealed moisture (10.0%), total ash (1.4%), equivalent weight (652.48), methoxyl content (3.7%), anhydrouronic acid (62.82%), degree of esterification (33.44%), acetyl value (0.68), and jelly grade (80).     

Analytical Methods for Pectin Methylesterase Activity Determination: a Review

Pectin methylesterase is an enzyme with an important in vivo role in plants as well as in food industry. This enzyme catalyzes the hydrolysis of methyl ester bounds in pectin which is one of the main components of cell wall in plants, producing methanol and free carboxylic groups. The effect of pectin methylesterase in food quality has been extensively studied, producing desirable effects in texture improvement as well as undesirable effects in some beverages. Likewise, the low methoxyl pectin produced by this enzyme has characteristics that contribute to formulate best quality food products. Pectin methylesterase is a ubiquitously enzyme that presents multiple isoforms, but is not only present in plants; it is also found in fungi, bacteria, and yeast, which have specific chemical and physical characteristics. The latter makes the task of analyzing the wide variety of these enzymes with its specific characteristics difficult. Based on this enzyme relevance and the aforementioned, multiple methods have been developed in order to evaluate pectin methylesterase activity with different research objectives. In this paper, the importance of the enzyme as well as advantages and drawbacks of the different methods will be discussed besides applications and evolution of these will be mentioned. Additionally, this paper will improve the understanding of the systems used in pectin methylesterase activity analysis.     

Mild-Heat and High-Pressure Inactivation of Carrot Pectin Methylesterase: A Kinetic Study

ABSTRACT: Pectin methylesterase (PME) was extracted from carrots and purified by affinity chromatography. The thermal high-pressure inactivation of the PME was investigated in a model system. Under these conditions, the (thermo) stable fraction is not inactivated and the isobaric-isothermal inactivation followed a fractional-conversion model. At lower pressures (< 300 MPa) and higher temperatures (> 50°C), an antagonistic effect of pressure and heat was observed. A 2nd- and 3rd-degree polynomial model (derived from available thermodynamic model) was successfully used to describe the heat pressure dependence of the inactivation rate constants. From the purified carrot PME sample, the thermostable PME fraction was isolated. The thermal inactivation of this fraction followed first-order kinetics.     

Orange Juices and Concentrates Stabilization by a Proteic Inhibitor of Pectin Methylesterase

A proteic inhibitor of pectin methylesterase (PME), recently discovered in kiwi, was used to stabilize cloud of orange juice concentrate with “Cut-back,” 42° Brix. To concentrated and pasteurized orange juice were added increasing amounts of fresh juice (12° Brix) with PME 0.8 U/mL at the fresh to pasteurized ratios 6.6 to 38%. The PME inhibitor (65% pure), from kiwi, was added at 50 mg/L. After 8 mo at 5°C samples were compared with controls containing the same amount of fresh juice with PME inhibited by pasteurization. Pasteurized samples were not different from those treated with PME inhibitor. Conversely, where PME was not inhibited, cloud stability decreased with increasing amounts of fresh juice. Use of kiwi PME inhibitor in fruit juice production has potential advantages.     

苹果皮果胶的提取工艺研究

对从新鲜苹果皮中提取果胶的工艺条件进行了研究,经过酸水解提取、酒精沉淀等工艺提取出具有广阔市场前景和丰富营养价值的天然食品添加剂果胶粉。     

Influence of Enzymatic Clarification with a Pectin Methylesterase on Cider Fermentation

In this study, the effect of two apple juice treatments (clarification with a pectin methylesterase in the presence and absence of sulphiting) on the cidermaking process was investigated. Pre‐fermentative clarification with the pectin methylesterase (Rapidase CPE) slowed the alcoholic fermentation in respect to traditional fermentation, the greatest effect being found for the combination of the enzymatic treatment with sulphur dioxide addition. With this treatment the start of the fermentation was delayed seven days. Enzymatic clarification delayed malolactic fermentation (MLF) and the interaction of both treatments produced a cider in which malolactic fermentation had not occurred. Both treatments ensured that the volatile acid levels during the maturation phase were significantly lower than in the traditional fermentation. Enzymatic clarification led to lower levels of yeasts during the active phase of alcoholic fermentation with respect to the control. When this treatment was combined with sulphiting, a decrease in apiculate yeast numbers during alcoholic fermentation was observed and a better survival of these species was noted after 59 days of fermentation.