六种果皮原料果胶的理化及凝胶特性比较

为了解不同品种水果的果皮(柚子皮、西番莲皮、脐橙皮、石榴皮、榴莲皮)以及向日葵盘所提取果胶的理化和质构特性,研究了不同原料果胶的得率、色泽、果胶酸含量、甲氧基含量、酯化度、黏度及质构特性,特别是采用高效液相色谱准确测定了各类果胶的分子量。结果表明:柚子皮、向日葵盘和脐橙皮果胶质量分数较高,分别为18.06%、14.61%和14.43%;西番莲皮果胶质量分数为8.76%;而石榴皮及榴莲皮果胶质量分数较低(均<3%)。从分子量看,石榴皮、脐橙皮果胶分子量较大(>1000kDa),向日葵盘果胶分子量最小(483kDa)。此外,几种果胶的溶胶均属低黏度值果胶(<25厘泊),且在pH值为7.0时黏度最大、在pH值为5.0时黏度最小。结合凝胶质构分析表明:石榴皮果胶分子量最大,凝胶强度最大,但为高甲氧基果胶,且得率较低;而向日葵盘果胶分子量最小,但得率较高,且为低甲基果胶,在非糖及含糖体系中均可形成性能优良的凝胶,因此是生产果胶的良好原料。该文为果胶的生产及应用提供参考。     

微波辅助提取黄皮果肉果胶工艺参数优化

为优化微波辅助提取黄皮果肉中果胶的工艺,采用均匀设计法,考察了微波功率、提取时间、液料比及提取液pH值4个因子对黄皮果胶得率的影响。利用SAS软件对试验数据进行模型拟合和回归分析,确定提取时间和液料比是影响果胶得率的重要因子,并最终获得微波辅助提取黄皮果胶的最优工艺参数为:微波功率600W,提取时间8min,液料比24:1mL/g,提取液pH值2.0。在此条件下果胶得率为3.59%。通过对果胶基本特性的测定分析,该工艺提取的黄皮果胶品质基本符合国家标准,可为黄皮果胶提取的工业化放大提供参考。     

微波辅助提取中pH值与脱色对苹果果胶的影响

为了得到高得率、高品质的苹果果胶,该文利用不同pH值的盐酸溶液对苹果渣中果胶进行微波辅助提取（Microwave-assisted extraction, MAE）,之后对果胶提取液进行大孔树脂XAD-16HP脱色,研究了pH值与脱色对果胶得率和品质的影响。结果表明：微波辅助提取工艺中随着pH值的升高,果胶得率、半乳糖醛酸质量分数和总离子含量减少,酯化度、黏均分子量和总多酚增加,褐变度无显著变化;大孔树脂吸附脱色后果胶褐变度、总多酚、彩度C*值显著下降,色调角H°值显著增加,半乳糖醛酸质量分数和酯化度没有     

传统与微波辅助工艺提取苹果果胶品质比较

该研究比较了传统工艺（CSE）与微波辅助工艺（MAE）所提取苹果果胶的品质差异,微波工艺[pH=1.0,提取时间20.8 min,功率499 W,料液比=1︰14.5（m/V）]提取的苹果果胶其得率、纯度和总离子含量均显著高于传统工艺[pH=2.0,提取时间1.5 h,温度85℃,料液比=1︰13],动态模式下对果胶溶液凝胶性能分析发现,传统工艺提取的苹果果胶凝胶温度为94℃,微波工艺提取的温度为82℃,但其酯化度和黏均分子质量显著小于传统工艺;传统工艺提取的苹果果胶溶液褐变指数、屈服应力、表观黏度、活化能显著高于微波工艺,总酚含量显著低于微波工艺;传统工艺提取苹果果胶溶液的亮度值和色调角均高于微波工艺,彩度值低于微波工艺提取的苹果果胶;频率扫描发现,传统工艺提取的果胶溶液具有更加稳定的三维结构,分子间相互结合得更加紧密,具有更好的凝胶特性。     

微波干燥预处理对苹果渣提取果胶的影响

利用微波干燥技术对湿苹果渣进行预处理,研究了微波干燥预处理对苹果渣提取果胶的影响.以探索一种新的干燥方法和提高果胶品质.结果表明:微波能量越大,苹果渣组织结构破碎越严重,其复水能力越弱;但对苹果渣颜色无显著影响;微波干燥预处理能显著提高果胶得率,微波预处理条件为300 W、15 min、7.5×10-2kW·h或500 W、10 min、8.3×10-2kW·h时微波预处理苹果皮渣的果胶提取得率比对照提高了50%左右,是较为适宜的微波处理条件,但微波能量大于8.3×10-2kW·h时,对果胶得率有不利影响;微波干燥预处理对果胶半乳糖醛酸含量无显著性影响,但显著提高了果胶的酯化度、固有黏度和黏均分子质量.     

超声波辅助提取秋葵果胶工艺优化及理化性质分析

为开发优质果胶资源,利用超声波辅助法从黄秋葵和红秋葵果荚中提取果胶,采用单因素试验探讨了酸种类、料液比、pH值、提取温度、超声时间和超声功率对2种秋葵果胶提取率的影响,并应用BoxBenhnken设计应面试验,确定果胶的最优提取工艺,并对其理化性质进行比较分析。结果表明,黄秋葵果胶的最佳提取工艺条件:萃取溶剂为盐酸、pH值2.0、提取温度70℃、料液比1∶40 g·m L-1,超声时间41 min、超声功率350 W,果胶提取率最高为15.87%;红秋葵果胶的最佳提取工艺条件:萃取溶剂为盐酸、pH值2.0、提取温度70℃、料液比1∶36 g·m L-1,超声时间42 min,超声功率350 W,果胶提取率最高为15.03%。经傅里叶红外光谱分析及理化性质测定,黄秋葵、红秋葵果胶的各项指标均优于国家标准,两者半乳糖醛酸含量分别为78.72%、72.92%,酯化度分别为66.95%、68.68%,均属于高酯果胶。添加黄、红秋葵果胶后,凝胶质构特性均得到明显的提升。本研究结果为果胶新资源的开发利用提供了基础数据。     

微波加热法提取柚果皮果胶的工艺（简报）

对新鲜柚果皮中果胶进行微波提取,采用咔唑比色法测定提取液中的果胶含量.探讨了料液比、微波功率、微波处理时间、盐析条件等对果胶得率和半乳糖醛酸含量的影响,运用L9(34)正变试验对微波加热提取果胶的工艺条件进行了优化.结果表明:微波功率对果胶得率有极显著影响,微波处理时间影响较小.较佳工艺是:液料比(V/m)8:1,调pH值为2.0,微波功率640W,处理时间8 min,盐析饱和硫酸铝用量与酸萃取液比例为3:5,此条件下提取柚皮果胶得率为4.457％,果胶的半乳糖醛酸含量为42.58％．     

超声波微波协同提取沙棘叶黄酮及其组成和活性研究

沙棘叶中富含黄酮类化合物等多种活性成分,为提高其提取率和利用率,本研究采用常规溶剂萃取、超声辅助、微波辅助、超声波微波协同提取4种方法对沙棘叶黄酮进行提取,测定沙棘叶黄酮得率并观察沙棘叶的微观组织结构,比较筛选沙棘叶黄酮的最佳提取方法。并采用响应面法对最佳提取方法进行工艺优化,同时测定沙棘叶黄酮组成和体外抗氧化活性。结果表明,超声波微波协同提取法是提取沙棘叶黄酮的最佳方法,黄酮得率较常规溶剂萃取法提高了42.54%(P<0.05),沙棘叶细胞损伤最严重。超声波微波协同提取沙棘叶黄酮的最佳工艺为乙醇体积分数61%、提取时间18 min、微波功率446 W,此时黄酮得率为42.09 mg·g^-1。沙棘叶黄酮提取液中共鉴定出6种黄酮类成分,分别为儿茶素、丁香酸、山萘酚、槲皮素、异鼠李素、杨梅素,其中儿茶素含量最高,为1.474 8 mg·g^-1,其余5种的含量均在0.1~0.3 mg·g^-1之间,山萘酚最低,为0.125 2 mg·g^-1;沙棘叶黄酮提取液具有较强的还原力及较高的1,1-二苯基-2-三硝基苯肼(DPPH)、2,2'-联氮-双-3-乙基苯并噻唑啉-6-磺酸(ABTS)和羟基自由基清除率,抗氧化活性较高。本研究为沙棘叶黄酮的工业化生产提供了科学依据。     

生物质在熔盐中的热裂解特性

为了研究生物质在熔盐中的热裂解特性,在自行设计的生物质热裂解反应器中,以熔盐热裂解生物质,考察了裂解温度、FeCl2含量和原料种类对生物质热裂解特性的影响,测定了生物油的物性参数,并用气相色谱-质谱（GC-MS）分析了生物油的主要组成。结果表明：在物质的量比为7︰6的ZnCl2和KCl混合熔盐中添加物质的量分数为5% FeCl2裂解生物质,温度对热裂解的影响显著,生物油得率随温度先升高后降低,存在最大值,以水稻秸秆为原料相对应的温度为525℃,最高生物油得率约为18%;添加FeCl2能提高生物油得率;以纤维素为原料裂解制得的生物油含水率小于以水稻秸秆为原料的生物油含水率;生物油含水率较高,其密度与水相近,黏度比水略大,灰分少,pH值为2.5～3.0;生物油成分复杂,含甲氧基类有机物较多,需改性后使用。该研究为熔盐热裂解生物质制取生物油提供了参考依据。     

豆皮果胶类多糖的提取及其在大豆蛋白凝胶类食品的应用

为提高大豆副产物利用率,拓展豆皮果胶类多糖（Soybean Hull Pectin Polysaccharide, SHPP）在凝胶类食品的应用,该研究采用盐辅助结合水热处理技术提取大豆豆皮中的豆皮果胶类多糖,并对其基本理化性质进行表征。通过以大豆蛋白为主要成分的凝胶类食品豆腐花为模型,探究不同添加量豆皮果胶类多糖（0～2.0%）与大豆蛋白的离散型相分离行为,分析其微相分离行为与宏观流变学性质、机械性能、持水性与感官评定的关联性,并与商品化柑橘果胶（Citrus Pectin, CP）作对比。结果表明,该提取法所得豆皮果胶类多糖提取率为17.95%±0.21%,其半乳糖醛酸含量为42.13%±2.05%,平均粒径为（210.3±2.9）nm,多分散性指数（Polydispersity Index, PDI）为0.466±0.037,豆皮果胶类多糖具有良好的亲水性和低黏度特性,易分散于水。添加0～0.5%豆皮果胶类多糖制备豆腐花,发现其微观上无相分离产生,具有良好的网络微结构;宏观上表现为外观白嫩,黏弹性、持水性与口感均良好。添加1.0%豆皮果胶类多糖的豆腐花宏观上出现明显析水,凝胶黏弹性和持水性均显著（P<0.05）减少。继续增加豆皮果胶类多糖至1.5%添加量则会导致相分离产生,蛋白凝胶网络微结构变得无序,网状孔隙增大,凝胶强度进一步减弱,保水性极差（46.2%±3.2%）。由此确定,豆皮果胶类多糖适宜添加量为0.5%。与经优化的柑橘果胶添加量为0.1%的豆腐花作比较,发现添加0.5%豆皮果胶类多糖的豆腐花在质构特性以及色泽、组织状态、滋味气味、口感、可接受度各方面的感官评分上均优于含柑橘果胶的豆腐花。结果表明豆皮果胶类多糖更适用于蛋白凝胶类食品。研究结果为豆皮果胶类多糖的应用开发,大豆副产物的再利用以及全豆食品的发展提供一定推动作用。     

Monovalent salt-induced gelation of enzymatically deesterified pectin

Pectin gels were induced by monovalent salts (0.2 M) concurrently with deesterification of high methoxy pectin using a salt-independent orange pectin methylesterase (PME). Constant pH was maintained during deesterification and gelation. If salt or PME was absent, the pectin did not form a gel. The gel strength was influenced by both pH and species of monovalent cation. At pH 5.0, the pectin gel induced by KCl was significantly stronger than the NaCl-induced gel. In contrast, a much stronger gel was produced in the presence of NaCl as compared to KCl at pH 7.0. LiCl did not induce pectin gelation at either pH. Molecular weights of pectins increased from 1.38 x 10(5) to 2.26 x 10(5) during NaCl-induced gelation at pH 7. One proposal to explain these pectin molecular weight changes is a hypothetical PME transacylation mechanism. However, these pectin molecular weight changes can also be explained by metastable aggregation of the enzymatically deesterified low methoxy pectin. We postulate that gelation was induced by a slow deesterification of pectin under conditions that would normally salt out (precipitate) low methoxy pectin in the absence of PME.     

Gel formation mechanism and gel properties controlled by Ca2+ in chia seed mucilage and model substances

Polygalacturonic acid (PGA) is considered as a model substance for mucilage to study mucilage–soil interactions, assuming that the gel formation mechanism of mucilage is comparable to the one of PGA. However, some studies question the accepted hypothesis, which states that, like for PGA, this mechanism relies on cross‐links between uronic acid and calcium for mucilage. The aim of this study was therefore to understand the influence of the abundance and degree of esterification of uronic acids and the influence of calcium on the gel formation mechanism in mucilage as compared to model substances. The mucilage used was from chia seeds, as it is easily available in great quantity and has gel properties shared by root mucilage. Results reported here demonstrate that, while the gel formation mechanism of PGA relied on specific cross‐links with calcium and led to heterogeneous gels, low‐methoxy pectin (LMP) formed homogeneous calcium gels also characterized by nonspecific ionic interactions with calcium. On the contrary, despite similar uronic acid content to LMP, chia seed mucilage was mostly governed by weak electrostatic interactions between entangled polymer chains, which conferred the gel poor water retention. Addition of calcium reduced repulsion and molecular expansion, resulting in a reduction of the water content in chia seed mucilage. Finally, the discrepancies between PGA, LMP and chia seed mucilage discredit the use of PGA as model for chia seed mucilage. Comparison with root mucilage is still needed. This study offers the keys for further mechanistic understanding on the influence of mucilage on soil properties.     

Influence of Microwave Heating on Some Physicochemical Properties of Wheat Grain Harvested in Three Consecutive Years

Grain of winter wheat cv. Begra was investigated for changes in some physical and chemical properties resulting from direct influence of microwave heating on grain harvested in three subsequent generations of crops at Plant Breeding Station DANKO in Choryn, Poland. Wheat grain samples tested immediately after microwave treatment with the highest grain temperature at 79 and 98°C showed a statistically significant decrease in moisture content (MC), thousand kernel weight (TKW), single kernel weight (SKW), single kernel diameter (SKD), and hardness index (HI), with the exception of grain samples M‐120 and M‐180, respectively, where statistically significant increases in HI and SKD were observed. Indirect effect of microwaves caused statistically significant fluctuation of the total protein content (TPC), TKW, single kernel moisture content (SKM), HI, SKW, and SKD in all three wheat grain crops in relation to their control samples. This indicates that the studied physicochemical properties of grain were affected by microwave rays not only directly but also indirectly.     

Citrus pectin: characterization and inhibitory effect on fibroblast growth factor-receptor interaction.

This study was undertaken to characterize the pectin from four citrus species and to determine their in vitro inhibitory activities on the binding of fibroblast growth factor (FGF) to the FGF receptor (FGFR). Pectin from various parts of lemon, grapefruit, tangerine, and orange were isolated and characterized. Tangerine had the highest pectin content among the four citrus species. Segment membrane contained as much as or more pectin than flavedo/albedo. Anhydrogalacturonic content was highest in pectin from segment membrane of tangerine and flavedo/albedo of grapefruit. Lemon pectin contained the highest methoxyl content (MC), and grapefruit contained the largest proportion of lower molecular weight (<10000 Da) pectin. Tangerine contained the highest neutral sugar in both flavedo/albedo and segment membrane. The interdependency of heparin on factor-receptor interaction provides a means for identifying new antagonists of growth factor activity and thus for treatment of various diseases. These results showed that pectin significantly inhibited the binding of FGF-1 to FGFR1 in the presence of 0.1 microg/mL heparin. The pectin from the segment membrane of lemon was the most potent inhibitor. The inhibition activity was significantly correlated with sugar content, MC, and size of pectin. Kinetic studies revealed a competitive nature of pectin inhibition with the heparin, a crucial component of the FGF signal transduction process. The observation that the heparin-dependent biological activity of FGF signal transduction is antagonized by citrus pectin should be further investigated for the use of these pectins as anti-growth factor agents for potential health benefits.     

超声预处理对荠菜微波干燥品质的影响

为提高荠菜的微波干燥品质,采用不同超声功率(4、6、8和10 W/g)对荠菜进行预处理,研究荠菜的传质特性、微观结构、水分分布、酶活性、微波干燥特性、色泽、复水性、营养成分和风味特性。结果表明：1)相较于未超声对照组,超声预处理显著降低了荠菜中过氧化物酶(peroxidase,POD)和多酚氧化酶(polyphenol oxidase,PPO)活性(P<0.05),提高了干物质损失率;2)超声预处理后,荠菜内部细胞间隙及直径增大,荠菜的水分自由度增大,当超声预处理功率为6 W/g时,细胞结构较为完整;3)超声预处理促使荠菜微波干燥速率提高,超声预处理功率为6 W/g时,荠菜干燥速率较高,有效水分扩散系数为2.153 1×10^-6 m²/s;4)荠菜微波干燥动力学模型拟合结果显示,Page模型决定系数R²(0.989 1～0.995 0)较高,均方根误差RMSE(0.024 2～0.035 1)及卡方值χ²(0.000 6～0.001 2)较低,拟合效果最佳;5)超声预处理功率为6 w/g时,微...     

Solvent effects on the molecular properties of pectins

Measurements revealed that LiAc/HAc buffer, when compared with other solvents, gave relatively low values of turbidity for five commercial pectins with various apparent molar masses and degrees of methyl esterification (DE). Therefore, HPSEC with on-line light scattering and viscosity detection was employed to compare LiAc/HAc buffer against NaNO(3) solution, a commonly used mobile phase for measuring the molecular properties of these pectins and an additional pectin prepared by microwave extraction. Microwave-extracted pectin was included in the study for its higher molar mass and DE compared with commercial pectins. Most commercial samples were more soluble and had a higher molar mass when dissolved in NaNO(3) than in LiAc/HAc buffer, whereas the microwave-extracted pectin was more soluble in LiAc/HAc buffer and had about the same molar mass. Furthermore, association fragments of pectin contained in samples were more dissociated by LiAc/HAc buffer than by NaNO(3). For the samples studied, weight-average molar masses ranged from about 41000 to 307000, weight-average intrinsic viscosities from about 0.86 to 9.76 dL/g, z-average radii of gyration from about 13 to 45 nm, and Mark-Houwink constants from about 0.62 to 0.94.     

Genetic Diversity in Properties of Starch from Zimbabwean Sorghum Landraces

Starch was isolated from 95 sorghum landraces from Zimbabwe using an alkali steep and wet‐milling procedure. The physicochemical properties of sorghum starch were examined for potential use in Southern Africa. All the landraces evaluated had a normal endosperm indicated by the amylose content of the starches. Starch properties were not correlated to most of the physical grain quality traits evaluated. Grain hardness was weakly correlated to starch gel adhesiveness (r = 0.36) and amylose content (r = 0.38) (P < 0.001). The mean peak viscosity (PV) of the sorghum starches was 324 Rapid Visco Analyser units (RVU) compared with 238 RVU in a commercial corn starch sample; PV was 244–377 RVU. Some landraces had low shear‐thinning starches, implying good paste stability under hot conditions. Pasting properties were highly correlated among the sorghum starches. The starch gel hardness showed considerable variation (44–71 g) among the landraces. Gelatinization peak temperatures were 66–70°C. The thermal properties of starches were not correlated with starch swelling and pasting properties. Genotype grouping by highest and lowest values in each category would allow selection of sorghums based on a specific attribute depending on the desired end use.