酰胺化低酯果胶凝胶破碎强度的影响因素

酰胺化低酯果胶具有较普通低酯果胶更优越的胶凝性质,国外对其的研究已经不限于制备工艺,而更多在于其性质及新产品的应用开发,但国内的研究还几乎是空白.本文以柑橘酰胺化低酯果胶为研究对象,对其凝胶破碎强度的影响因素进行了研究.研究其形成凝胶时的影响因素:凝胶保存时间与温度、成胶条件(果胶浓度、体系pH、钙离子浓度、缓冲盐的种类及含量),并探讨了各因素对凝胶破碎强度影响的机理.此外,对比高酯果胶形成的凝胶,研究了酰胺化低酯果胶凝胶的热可逆性质.研究表明其成胶时主要受到凝胶保存的温度与时间、酰胺化低酯果胶含量、凝胶体系pH、钙离子浓度、蔗糖浓度、缓冲盐种类及添加量等因素的影响;其中缓冲盐的种类及含量对凝胶破碎强度有影响;并且,酰胺化低酯果胶的热可逆性也与缓冲盐有关.该结论为其作为胶凝剂在食品中的应用打下良好的理论基础.     

低酯果胶凝胶质构特性的研究

以普通低酯果胶和酰胺化低酯果胶为研究对象,凝胶硬度和弹性为衡量指标,探讨果胶浓度、蔗糖浓度、钙离子浓度、pH值对果胶凝胶质构特性的影响,由单因素试验可以得出,酰胺化低酯果胶比普通低酯果胶的凝胶性能更好。通过正交试验,进一步得出酰胺化低酯果胶的最佳凝胶条件为:果胶浓度1.3g/100mL,蔗糖浓度20g/100mL,钙离子浓度35mg/g,pH 3.6,在该条件下,酰胺化低酯果胶凝胶的硬度为47.06g,弹性为3.81mm。     

豆腐柴叶胶质胶凝特性的研究

对豆腐柴叶胶质胶凝特性及其主要影响因子—pH值、盐离子、温度、增稠剂和脱水剂进行了研究,结果表明:豆腐柴叶胶质在pH<4.5以下自成凝胶;Ca2+及Cu2+均可促进胶质胶凝,但所成凝胶以加Ca2+者为好;单一温度对胶质胶凝性基本无作用;加10%糖并加热时可使胶质胶凝的pH值普遍下移0.5个单位;β-环糊精等增稠剂可改善胶质的凝胶强度或离析现象。     

黄秋葵果胶理化特性的研究

以商品柑橘果胶为对照,研究黄秋葵果胶的理化特性及果胶质量浓度、加热温度、pH值、蔗糖质量浓度和CaCl2质量浓度等因素对黄秋葵果胶黏度的影响。结果表明：黄秋葵果胶总半乳糖醛酸含量为86.68%,酯化度为75.45%,溶解度为82%,pH值为4.63,属于弱酸性高酯果胶;黄秋葵果胶的黏度随着加热时间的延长而下降,但其热稳定性优于商品柑橘果胶;黄秋葵果胶的黏度与其质量浓度、蔗糖质量浓度均成正相关,与加热温度成负相关,而随pH值、CaCl2质量浓度的增大呈先上升后下降的趋势,表现出一般果胶的黏度特性。黄秋葵果胶的黏度及热稳定性能优于商品柑橘果胶,是一种优质果胶。     

低酯桔皮果胶凝胶的动力学分析及分形研究

本实验通过流变学方法研究了酰胺化桔皮果胶的胶凝性质并进行相关的动力学分析。首先探讨了在冷却过程中果胶浓度及pH值对体系弹性模量及凝胶形成速度的影响;然后对果胶溶液在冷却过程中形成的凝胶进行了分形研究,采用两种模型进行相关运算并得到了相同的分维数但表征了不同的凝胶体系。     

百香果皮果胶的理化及凝胶特性

以商品柑橘果胶为对照,对百香果皮果胶进行了理化性质和色差比较,傅里叶红外光谱分析,质构特性测定,并探讨了百香果皮果胶质量浓度、蔗糖添加量、pH、温度、金属离子类型对百香果皮果胶凝胶强度和持水性的影响。结果表明,百香果皮果胶颜色呈黄褐色,经理化性质测定和红外光谱分析,百香果皮果胶各项指标均符合国家标准,酯化度和半乳糖醛酸分别为(66. 46±0. 41)%和(81. 99±1. 54)%,属于高酯果胶;添加百香果皮果胶后,百香果果胶凝胶体系的质构特性有所提升,其凝胶强度和持水性与百香果皮果胶质量浓度成正相关,随蔗糖质量浓度、温度、pH的增大呈现先增大后减小的趋势,在凝胶过程中添加Ca2+、Cu2+均可提高百香果皮果胶的凝胶特性。     

海藻酸钠-高甲氧基果胶复合体系凝胶特性的研究--蔗糖、Ca2+、葡萄糖酸-δ-内酯对复合体系凝胶特性的影响

研究了蔗糖、Ca2+、葡萄糖酸-δ-内酯对海藻酸钠-高甲氧基果胶复合体系凝胶特性的影响.结果表明蔗糖、Ca2+对该体系的凝胶特性影响很大,适量蔗糖的添加不仅可增加体系的凝胶强度和持水性,还可增加凝胶的融点;Ca2+的添加可使体系的凝胶类型从热可逆变成热不可逆,且对体系凝胶强度的影响与其对海藻酸钠的影响类似;在海藻酸钠、高甲氧基果胶单独不能形成凝胶的条件下,葡萄糖酸-δ-内酯的添加可诱导两种胶的混合物形成凝胶,且该复合物的凝胶强度与葡萄糖酸-δ-内酯的浓度、胶体总浓度有关.     

Ca2+激活生物酶对苎麻纤维脱胶的工艺参数优化

利用Ca2+对生物酶进行有效激活,以提高苎麻生物酶脱胶效果,优化脱胶工艺中Ca2+浓度、pH值、通气量等工艺参数,经过Box-Behnken试验设计和SAS软件分析,得出最优工艺条件为:果胶酶、半纤维素酶浓度分别为12、4 mg/mL,酶处理时间5 h,酶处理温度50°C,Ca2+浓度4.23 mg/mL,pH值4.8,通气量9.2 dm3/min.利用最优工艺处理后的精干麻的残胶率为1.96%,断裂强力为64.5 cN,纤维平均细度为0.457 tex.     

高酯果胶氨法降酯条件的研究

采用氨水对高酯速凝果肢进行降酯条件的研究，并对所得到的产品的半乳糖醛酸、酯化度、胶凝度等重要指标进行分析，通过正交实验确定了氨法降酯的最佳工艺条件：果胶浓度2％、反应pH值10．0、反应时间1h、反应温度15℃。     

低甲氧基果胶的胶凝机理及防止预凝胶形成的措施

对低甲氧基果胶的胶凝机理及影响胶凝的主要因素———pH值、可溶性固形物含量、钙离子浓度进行了探讨 ,并针对低甲氧基果胶应用中产生的降低产品质量的预凝胶问题进行了讨论 ,为分析低甲氧基果胶应用中的问题提供了依据 ,并提出了一些防止预凝胶形成的措施。     

酰胺化果胶的特性、应用及研究现状

本文将酰胺化果胶与普通低酯果胶以及高酯果胶进行了多方面的比较，重点介绍酰胺化果胶的特性。结合国内外对酰胺化果胶生产和研究的状况，及其在食品工业和医疗方面的应用现状，对酰胺化果胶生产的开发前景进行了分析。     

On the formulation design and rheological evaluations of pectin-based functional gels

In the current study, formulation design and development of a novel pectin-based functional gel were investigated. Amidated low methoxyl pectin (ALMP), high methoxyl pectin (HMP), sorbitol, inulin, rebaudioside-A, gardenia, phloridzin, quercetin, apple flavor, and calcium chloride (as its dihydrated salt) were selected as general ingredients. Response surface methodology was applied to design different formulations and to investigate on their experimental responses. The oscillatory tests were carried out in 2 stages with ALMP, HMP, sorbitol, and inulin as the variables of the 1st stage and ALMP and calcium chloride as the variables of the 2nd stage. Results of the 1st stage indicated relatively similar behaviors throughout the frequency range applied for all of the samples studied (true gels). However, magnitudes of the 5 rheological parameters of this study (storage modulus, loss modulus, loss tangent, complex modulus, and complex viscosity) were affected by different variables (ALMP, HMP, inulin, and sorbitol concentrations). Experimental results confirmed that sorbitol could be omitted from the formula while inulin and HMP could be used at their highest levels studied. At the 2nd stage, only 2 formulas indicated a strong gel behavior and other formulas showed typical behaviors of weaker gels or those of the concentrated solutions. At the conclusion of this study, a finished gelled product formula was suggested with the application of the best levels of the ingredients. The resultant gel was found to be set rapidly with no syneresis and showed a potential to be considered as a functional gelled dessert.     

酰胺化果胶的特性、应用及生产和研究状况

对果胶类型做了概括介绍,将酰胺化果胶与普通低酯果胶以及高酯果胶进行多方面的比较,突出酰胺化果胶的特性。结合国内外对酰胺化果胶生产的研究现状,以及其在食品工业和医疗方面的应用现状,对酰胺化果胶生产的发展前景进行了分析。     

A light scattering study on the effects of pH on pectin aggregation in aqueous solution

Light-scattering measurements were carried out on pectins in aqueous solutions of pH ranging from about 4 to 2. The following pectin samples were used: three low methoxyl pectins which were demethylated by ammonia, acid and enzyme (all with a nearly similar methoxyl content from 6.1 to 6.2%), and pectin-NF with 12.04% methoxyl groups and sodium poly-galacturonic acid. When the pH of a 0.05% pectin solution containing 0.1 M NaCl was brought to pH 2 by adding HCl, the mol. wt and radius of gyration increased markedly, thus indicating that pectin molecules aggregate when the pH is lowered.     

Comparison of Dialysis and Metal Precipitation Effects on Apple Pectins

Metal precipitation as a purification method for pectins was investigated for effects on chemical composition (anhydrogalacturonic acid, methoxyl and degree of esterification and neutral sugars), and molecular properties (molecular weight and intrinsic viscosity) in comparison with dialysis. The Cu(II) ions were used to separate pectins from non-uronide components, and then the Cu(II) ions complexed with pectins were removed by 1% acid alcohol or EDTA treatment. The contaminants were removed more effectively by metal precipitation than dialysis. Acid alcohol did not affect degree of esterification of pectins, whereas it significantly cleaved the neutral sugar side chains. Pectins treated with acid alcohol had lower molecular weights, but larger intrinsic viscosities indicating their more linear nature compared to pectins treated with EDTA.     

柠檬皮高酯果胶的分步提取及表征

本研究采用草酸对柠檬皮进行分步提取,得到两种不同性能的高酯果胶(HMP-1、HMP-2),系统地探究了提取条件HMP-1和HMP-2得率和黏度的影响,对HMP-1、HMP-2进行物化性质表征,并通过原子力显微镜(AFM)进行微观结构观察。实验结果表明,在料液比1:20,pH 1.7,70℃1.5 h的反应条件下,HMP-1得率为19.22%,1%溶液的黏度为104.55 mPa·s,分子量为550.4 ku,酯化度为75.22%,胶凝度为218.24°SAG,在酪蛋白等电点附近具有较高的电位绝对值;在料液比1:10,pH 1.7,80℃1.5 h的反应条件下,HMP-2的得率为9.74%,1%溶液的黏度为49.23 mPa·s,分子量为424.7 ku,酯化度为64.34%,胶凝度为171.12°SAG。AFM结果表明,HMP-1呈现较长的线性形态,HMP-2则呈现较为分散、细碎的状态。本研究实现了柠檬皮果胶的分步提取,得到不同类型的果胶,有助于果胶的多元化发展及精准应用。     

Stability of pectins during storage

Low methoxyl pectins (LMP) prepared by HCl, NaOH and NH₃ deesterification procedures were stored with or without adding Na₂CO₃ as buffer at room temperature (25–30°C) or exposed to different relative humidities (r.h.) at 37°C. Losses of methoxyl, molecular weight and gelling power were observed in all the pectin samples. During storage, NaOH and NH₃ deesterified LMP were more stable than HCl deesterified LMP with respect to gelling power. The monolayer values ( V _m) of 0.5 to 0.7 g per 100 g of LMP showed that even when stored at 11% r.h., the moisture in LMP was present in the multilayer region which was conducive to methoxyl loss.
NH₃ deesterified LMP precipitated at pH 0.5 and 1.5 after saponification, formed good gels similar to the LMP precipitated at pH 0.5, dried and mixed with buffer. NH₃ deesterified LMP precipitated at pH 3.0 and 4.5, on the contrary, formed only coagulated gels.
The loss of gelling power of LMP during storage was due to depolymerization besides gradual transformation of increasing portions of pectinic acid molecules into pectic acid molecules. High methoxyl pectins with or without added sodium carbonate or citrate as buffer stored at 62 and 75% r.h. showed methoxyl loss. Between r.h. of < 0.1 and 49%, methoxyl loss was more in the buffered samples than in the control.     

Characterization of pectin extracted from banana peels of different varieties

Pectins were extracted from banana peels of five different varieties using citric acid solution. The chemical characteristics of banana peel pectins were investigated and compared with citrus peel and apple pomace pectins which were extracted under the same extraction conditions to assess the potential of banana peels as an alternative source of commercial pectin. The yield of banana peel pectins ranged from 15.89 to 24.08%. The extracted banana peel pectins were categorized as high methoxyl pectin with the degree of esterification between 63.15 and 72.03% comparable to those of conventional pectin sources from citrus peel (62.83%) and apple pomace (58.44%). The anhydrouronic acid (AUA) content of banana peel pectins varied from 34.56 to 66.67%. Among various banana varieties being studied, pectin from Kluai Nam Wa variety had the highest AUA content (66.67%) which met the criteria for food additive pectin indicating its commercial significance as an alternative pectin source.     

Pectins as Breadmaking Additives: Effect on Dough Rheology and Bread Quality

The effect of two types of pectins with different degrees of esterification on dough and bread characteristics was analysed. A high methoxyl pectin (HMP) and a low methoxyl pectin (LMP) were assayed in dough without or with salt (2%) at levels ranging from 0.25% to 2.0%. Farinographic water absorption increased when pectins were incorporated in dough with salt, whereas this effect was not observed in dough without salt. Pectin addition diminished the stability of dough in all cases. Texture profile analysis showed that pectins softened the dough, particularly when salt was added. Cohesiveness was also higher in doughs with salt at the maximum level of hydrocolloid addition. In dough with salt, HMP decreased the elastic and viscous moduli, while the values for tan (δ) were increased with respect to control. SEM micrographs showed that dough with pectin has a filamentous structure. In the breadmaking process, dough with HMP showed a better performance, leading to higher specific volumes and softer crumbs both in fresh and stored bread.     

The effects of γ irradiation on the structure of apple pectin

The effects of γ irradiation on the mol. wts, viscosities and methoxyl contents of apple pectins were investigated at doses of 0–10 kGy. The apple pectins investigated were samples isolated in the laboratory before and after irradiation and an industrially purified apple pectin. No changes in mol. wts of the pectins were observed when whole apples were irradiated but decreases in viscosity and methoxyl content were observed at doses of 1 kGy. When isolated pectins were irradiated, reductions also in mol. wt were detected, at the same doses.