Influence of pectin properties and processing conditions on thermal pectin degradation

Texture degradation of fruits and vegetables during thermal processing is partly due to pectin depolymerization. In this contribution we investigate the influence of pectin properties (degree and pattern of methoxylation) and processing conditions (pH 2.0, 3.0, 5.0 and 7.0; temperatures of 80 up to 110 °C) on pectin degradation rate constants. Pectins with different degrees and patterns of methoxylation were prepared and heated, the extent of acid hydrolysis, β-elimination and demethoxylation was assayed as a function of treatment time. As the degree of methoxylation and pH decreased, β-elimination rate constants decreased while acid hydrolysis rate constants increased. Demethoxylation rate constants were minimal at pH 3.0 and increased both at lower and higher pH. Reaction rate constants were not considerably influenced by the pattern of methoxylation. All reaction rate constants increased with increasing temperature. As β-elimination rates are reduced by competing demethoxylation, both rate constants were compared. The ratio of these reaction rate constants showed no trend with pH. However, an increase in degree of methoxylation or temperature resulted in a more pronounced increase in β-elimination rate constants than in demethoxylation rate constants.     

Improving pectin technology.

The effect of ultrasonic treatment on pectin stability in aqueous solution was studied to establish conditions which minimized degradation. Pectin was extracted under these conditions with an increased yield and without reducing the drainage properties of the extracted fruit mass. A pulsed ultrasonic method in aqueous acidic medium was developed, successfully tested with three different apple pomace samples, and its advantages demonstrated.     

南瓜果胶脱色工艺的研究

将南瓜皮中提取的果胶分别用活性炭、双氧水及树脂进行脱色研究。实验结果表明,树脂201×7采用摆幅为5r/min,在经过15h振荡后效果最佳。     

Inhibition of tomato pectin methylesterase by partially purified kiwi pectin methylesterase inhibitor protein

The inhibition of tomato pectin methylesterase (PME) by a recently discovered kiwi pectin methylesterase inhibitor (PMEI) is described. PME was consequently purified by CM Sephadex C-50, Concanavalin A-Sepharose 4 B and Mono S chromatography, and PMEI by Q-Sepharose and Sephacryl S-200 chromatography. Inhibition of tomato PME activity under optimal conditions (0.125 m NaCl, pH 7.5) by partially purified kiwi PMEI (MW of 27 kD, pI ≥ 3.67) was independent of the PMEI/PME ratio between 36 and 61% of the maximal uninhibited activity. the non-competitive inhibition observed was optimal in the pH range of 5 to 7. PMEI was inactivated by heating to 120°C, and showed actinidin-like activity towards N-α-benzyloxycarbonyl-L-lysine p -nitrophenyl ester (CBZ-lys-ONp) and azocasein which was partially inhibited by the protease inhibitor leupeptin.     

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％。     

Microwave-assisted extraction of lime pectin

Pectin was extracted from lime flavedo, albedo and pulp by employing microwave-assisted extraction (MAE) under pressure. Heating times ranged from 1 to 10 min. Optimal time of heating was 3 min. Molar mass, viscosity, radius of gyration and hydrated radius were found to decrease with heating time. At 3 min heating time, depending on the lime fraction which was extracted, weight average molar mass ranged from about 310,000 to 515,000 Da, and weight average intrinsic viscosities ranged from about 9.5 to 13 dL/g. Pectins dissolved in 0.05 sodium nitrate were characterized by HPSEC with online light scattering, dynamic light scattering and viscosity detection. Molar mass polydispersity passed through maximum at 4 min. Molecules of pectin became less compact with increasing heating time. The results obtained here are consistent with previous evidence that extracted pectins may exist in solution as networks, partially formed networks, i.e. branched molecules or linear molecules depending on extraction conditions and the solvent in which they are dissolved.     

桑皮胶质绿色降解法

对桑皮胶质绿色降解方法进行探讨,分析了温度、时间、pH值、接种量等条件与残胶率的关系。通过正交试验,确定其最佳工艺条件为:温度37℃,时间22 h,pH值7.3,接种量12.5%,此时残胶率为13.4%。对胶质降解后的桑皮纤维进行长度、细度、断裂强度性能测试,其长度为35~45 mm,细度为3.6~4.0 tex,断裂强度为3.71~5.07 cN/dtex。     

Interaction of lysine with pectin

The interaction of l-lysine with citrus pectin was studied in a model system to determine under what conditions it would occur and whether it would be of physiological significance. Thirty-nine per cent of the lysine was non-diffusible at pH 7, when the pectin concentration was 0·5% and the lysine concentration was $\text{2 × 10}{}^{\mathrm{?3}}\text{M}$. Of this, 29% was restricted due to the Donnan effect and the remainder was specifically bound. Increasing the pH (in the range 6–8) and the pectin concentration both increased the non-diffusible lysine. Increasing the ionic strength and the degree of esterification both decreased the non-diffusible lysine. It was concluded that lysine would not bind to pectin in the intestine because of the high salt concentration there.     

果胶类多糖的功能特性与应用研究

果胶类多糖具有抗癌、降血糖、治疗糖尿病、减轻机体疲劳和增强免疫作用等功效,果胶类多糖也可以作为乳化剂稳定油-水界面,并且能够在酸性条件下稳定牛乳蛋白质,还能够抑制脂质的氧化.从医药行业到食品加工业对果胶类多糖功能特性及其应用进行了综述.     

苹果果胶研究进展

苹果(Malus pumila Mill.)是我国北方广泛种植的经济作物。近年来,很多学者从苹果渣中提取分离得到苹果果胶。现代医学和生物学研究表明,苹果果胶具有抗氧化、降血脂、抗菌及抗癌的功效。本文介绍了苹果果胶的结构、组分分级与特性研究,着重阐述了目前国内外对于苹果果胶的提取、分离的最新进展及其生物活性,讨论了目前研究中存在的问题,并对其发展前景进行了展望。     

改性柑橘果胶研究进展

改性柑橘果胶是一种功能丰富且结构复杂的可溶性多糖,它改善了柑橘果胶的性质并扩大其应用范围,具有较大的市场开发价值。近年来,改性柑橘果胶的研究得到了迅速发展,柑橘果胶的改性技术日趋完善且产品形式多样。柑橘果胶的改性方法可分为化学改性法、生物改性法和物理改性法,不同的改性方法可制备出性质不同的柑橘果胶。随着人们的健康意识日益增强,改性柑橘果胶的生理功能特性得到了广泛关注,包括抗癌、吸附重金属、抗炎、免疫调节、降血脂和药物运输等生理活性。本文介绍了改性柑橘果胶研究的最新进展,包括改性柑橘果胶的结构特性、改性技术和生理功能特性,并对该行业的发展进行了展望,旨在为我国改性柑橘果胶行业的发展提供一定参考。     

果胶碱法脱酯工艺影响因素的研究

以商品柑橘高酯果胶为原料制取低酯果胶.重点探讨了低温碱法脱酯时间对果胶质量和得率的影响并比较了异丙醇、甲醇沉淀果胶的效果.以果胶的半乳糖醛酸含量、酯化度(DE值)、黏度、得率等为分析对象.结果表明,低温下(4℃)碱法脱酯可将影响果胶品质的β-消去反应控制在较小程度,所得产品黏度能最大程度得到保持.柑橘高酯果胶碱法脱酯的最佳工艺条件为pH 9.0,控制温度在4℃,处理30 min,沉淀果胶用异丙醇,该条件所得果胶半乳糖醛酸含量为86.57%,DE值为47.98%,得率为81.5%,指标达到低酯果胶产品的标准.     

On the water-sorption properties of pectin

In this work we investigate the water-sorption isotherms of three types of pectins (from apple, citrus and sunflower) at 25 °C, 35 °C and 45 °C through the classical gravimetric method. The experimental data are treated with BET and GAB model equations for finding the monolayer moisture content X_w,a, BET and Guggenheim constants. The investigated pectins were characterized by their X-ray and infrared spectra and an attempt was made to correlate between their water-sorption properties and their molecular structure and crystal organization.     

柠檬皮中果胶物质的提取研究

通过酸水解的方法,探索了柠檬皮中果胶物质的提取条件,研究结果表明,当样品浸泡2.5h后,在pH值为2.2的95℃水中水解2.8h,柠檬皮中果胶的提取率可达15.6%。     

果胶的提取与分离

果胶在食品、医药和其它行业应用非常广泛,市场需求量大,而传统的酸提醇沉的提取方法有许多缺点,本文就近年来一些果胶的提取和分离方法进行了总结。     

Reaction of apple pectin with ammonia

Amidated apple pectins were prepared in aqueous and aqueous-alcoholic media, and the factors influencing both ammonolysis and hydrolysis of the ester groups of apple pectin by ammonia were studied.
In aqueous solution, the extent of ammonolysis and hydrolysis was very dependent upon ammonia concentration. In aqueous alcohol, the products were also dependent upon the particular alcohol and its concentration, increasing concentrations suppressing hydrolysis; the overall rate of reaction is much slower than in the absence of alcohol. The product balance between amonolysis and hydrolysis of the ester groups is influenced by the polarity of the medium, and by the concentration of NH⁺₄ and OH⁻.
It was shown that the extents of ammonolysis and hydrolysis of the ester groups are significantly affected by the polarity of the medium and the acid-base equilibrium of the interaction of ammonia with water, i.e. NH₃+H₂O ↔ NH⁺₄+OH⁻. The content of free ester and amidated carboxyl groups in the pectin can be regulated by varying the concentration of ammonia, temperature, reaction time and the polarity of the medium. The rate of enzymic hydrolysis of amidated pectins decreases with increasing amide content. A mechanism for the reaction is proposed.     

果胶提取技术研究进展

果胶是一种亲水性植物胶,由α-1,4糖苷键联接的半乳糖醛酸与鼠李糖、阿拉伯糖、半乳糖等中性糖聚合而成,是重要的食品添加剂之一.目前全世界果胶的年需求量近2万t,据有关专家预计果胶的需求量在相当长的时间内仍将以每年l5%的速度增长.我国每年消耗约1500t以上果胶,80%依靠进口,需求量与世界平均水平相比呈高速增长趋势.大力开展果胶的研究与开发,探索提高果胶产量和质量的新方法和新资源,不仅能为我国食品加工领域广泛地应用优质果胶提供理论依据,而且将推动国产果胶生产的发展.本文介绍了果胶的化学结构及提取用原料,以及果胶的应用范围,并结合国内外近年来的研究成果,系统综述了果胶的提取、脱色、沉淀和干燥的方法.果胶的提取方法主要有酸水解法、离子交换树脂法、微生物提取法、微波提取法、酶提取法及超声波提取法,脱色的方法主要有活性炭脱色法、双氧水脱色法、大孔树脂脱色法,沉淀的方法主要有醇析法、盐析法,干燥的方法主要有常温干燥、真空干燥、冷冻干燥及喷雾干燥.     

果胶酶解液抑菌性能的研究

对果胶酶解液的抑菌性能进行了研究。结果表明,果胶在酶解到一定程度后具有明显的抑菌活性,可显著抑制食品中常见细菌,特别是乳酸菌的生长,是一种极有开发价值的新型天然食品防腐剂。     

In Situ De-esterification of lime pectin

The in situ de-esterification of pectin in lime pulp by the action of pectinesterase (PE) has been investigated. It has been shown that the degree of pectin esterification is reduced to about 20% when the pulp is held at pH 8.5 for 90 min. The rate of de-esterification by the enzyme in situ is highest when the pH is in the range 7.5–9.0 and the NaCl concentration is 0.1–0.3M. At pH values above 9 chemical de-esterification becomes important. The activity of extracted lime PE was shown to be almost independent of pH in the range pH 6.0–9.0. It is suggested that the difference between the behaviour of the extracted and the in situ enzyme is due to the fact that the latter needs to be solubilised before it can act on some of the pectin in the pulp. In support of this it is found that the proportion of lime PE which can be extracted from the pulp decreases with decreasing pH and ionic strength, reflecting electrostatic binding to the cell wall.     

贮藏期间芦荟果胶含量变化及影响果胶粘度因素的研究

果胶作为由植物中提取的天然添加剂,具有良好的胶凝化和稳定化作用。从具有保健作用和药用价值的芦荟中提取果胶已广泛应用于食品工业、化妆品、医药等领域。本文对贮藏期间芦荟果胶含量态变化进行研究,并确定影响果胶粘度的因素,对芦荟果胶提取具有指导意义。本文采用酸水解醇析法提取芦荟中的果胶,确定提取果胶醇析过程中的最优pH和温度,并明确贮藏0～60d芦荟中果胶含量,此外还确定各种影响因素对果胶成品粘度的影响。结果表明,醇析过程中的最佳pH3.5,最佳温度为50℃。果胶成品的pH2.79（符合国标）,甲氧基含量为8.518%,属于高甲氧基果胶。贮藏0～60d库拉索芦荟中的果胶含量在贮藏10d时达到峰值。而后果胶含量随贮藏时间的延长而降低,并且在20d之后明显下降。因此,最适宜芦荟果胶提取和加工的时间为0～20d。所得芦荟果胶粘度与温度、柠檬酸和氯化钠添加量呈负相关,而与果胶浓度和蔗糖添加量呈正相关。