动态高压微射流协同糖基化对β-乳球蛋白乳化性和结构的影响

采用动态高压微射流（dynamic high pressure microfluidization,DHPM）协同糖基化处理β-乳球蛋白,研究改性β-乳球蛋白乳化性、乳化稳定性和结构的变化。研究发现DHPM协同糖基化处理过程中β-乳球蛋白结构变化与其乳化性能可能存在关联;DHPM协同糖基化处理能显著提高β-乳球蛋白的乳化性和乳化稳定性。0、40、120 MPa糖基化处理后β-乳球蛋白的乳化活性指数（emulsifying activity index,EAI）分别为136.3、168.1、177.9 m2/g。0 MPa协同糖基化处理后β-乳球蛋白的乳化稳定指数（emulsifying stability index,ESI）为52.3 min;随着压强逐渐增加至40 MPa和120 MPa,协同糖基化处理后ESI值分别升高为56.4 min和59.0 min。通过表征分析β-乳球蛋白结构变化发现：不同压力DHPM协同糖基化处理后,β-乳球蛋白分子质量升高;巯基含量升高;表面疏水性降低;二级结构变化以及氨基酸三维空间构象暴露程度发生变化。这些变化说明β-乳球蛋白与低聚半乳糖发生共价交联时改变了蛋白质结构,造成β-乳球蛋白表面亲水基团的增加,从而导致其乳化性能显著提高。     

DHPM处理下β-乳球蛋白与油酸相互作用对其功能性质的影响

采用动态高压微射流处理β-乳球蛋白与油酸混合物,研究β-乳球蛋白与油酸相互作用对其功能性质和表面疏水性的影响。与标准β-乳球蛋白相比,未经DHPM处理的混合物的功能性质和表面疏水性没有显著性变化(p0.05)。随着DHPM压力从40 MPa增至160 MPa,β-乳球蛋白油酸复合物的溶解度、乳化性、起泡性和表面疏水性都呈先增加后减少的趋势。溶解度和起泡性在80 MPa压力条件下达到最大,分别为95.36%和32.00%。而乳化性和表面疏水性呈正相关关系,在120 MPa压力条件下达到最大,分别为1.09和640.20。结果表明功能性质和表面疏水性的变化与不同DHPM压力下β-乳球蛋白与油酸相互作用的程度有关。     

动态高压微射流协同美拉德反应对α-乳白蛋白结构和功能性质的影响

采用聚丙烯酰胺凝胶电泳(SDS-PAGE)、光谱学等方法,研究动态高压微射流(DHPM)预处理结合美拉德反应对α-乳白蛋白(α-LA)结构和功能性质的影响。结果表明,DHPM预处理使α-LA的内源性荧光强度、表面疏水性增大,且呈先增后降的趋势,在处理压力为110MPa时,达到最大值。经乳糖美拉德反应后,α-LA的内源性荧光强度降低,表面疏水性增大,乳化性、抗氧化活性增强,表明DHPM预处理改变了α-LA的三级结构,从而促进美拉德反应、提高美拉德反应产物的乳化性能和抗氧化活性。DHPM预处理协同美拉德反应是一种有效改善蛋白质功能性质的方法。     

动态高压微射流协同糖基化对β-乳球蛋白乳化性和结构的影响

采用动态高压微射流(dynamic high pressure microfluidization,DHPM)协同糖基化处理β-乳球蛋白,研究改性β-乳球蛋白乳化性、乳化稳定性和结构的变化。研究发现DHPM协同糖基化处理过程中β-乳球蛋白结构变化与其乳化性能可能存在关联;DHPM协同糖基化处理能显著提高β-乳球蛋白的乳化性和乳化稳定性。0、40、120 MPa糖基化处理后β-乳球蛋白的乳化活性指数(emulsifying activity index,EAI)分别为136.3、168.1、177.9 m2/g。0 MPa协同糖基化处理后β-乳球蛋白的乳化稳定指数(emulsifying stability index,ESI)为52.3 min;随着压强逐渐增加至40 MPa和120 MPa,协同糖基化处理后ESI值分别升高为56.4 min和59.0 min。通过表征分析β-乳球蛋白结构变化发现:不同压力DHPM协同糖基化处理后,β-乳球蛋白分子质量升高;巯基含量升高;表面疏水性降低;二级结构变化以及氨基酸三维空间构象暴露程度发生变化。这些变化说明β-乳球蛋白与低聚半乳糖发生共价交联时改变了蛋白质结构,造成β-乳球蛋白表面亲水基团的增加,从而导致其乳化性能显著提高。     

添加顺序对β-乳球蛋白与EGCG及葡萄糖三元复合物结构和功能的影响

采用碱法和美拉德反应将β-乳球蛋白（β-lactoglobul in,β-LG）、表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）及葡萄糖（glucose,Glc）通过不同添加顺序获得2 种共价复合物β-LG-EGCGGlc con和β-LG-Glc-EGCG con,与直接混合形成的非共价复合物β-LG-EGCG-Glc mix和β-LG-Glc-EGCG mix进行对比,研究添加顺序对三元复合物的结构和功能性质的影响。结果表明：不同添加顺序对共价复合物的影响大于非共价复合物。β-LG-EGCG-Glc con与β-LG-Glc-EGCG con在结构和功能性质上有较大差异,而β-LG-EGCGGlc mix和β-LG-Glc-EGCG mix在结构和功能上差别不大。聚丙烯酰氨凝胶电泳和紫外吸收光谱结果显示不同添加顺序对三元复合物的共价结合过程具有较大影响。结构表征发现,共价复合物的荧光猝灭和疏水性都高于非共价复合物。相较于β-LG-EGCG-Glc con,β-LG-Glc-EGCG con有更强的猝灭程度以及更高的疏水性,而β-LG-EGCG-Glc mix与β-LG-Glc-EGCG mix两者差距不明显。此外,2 种共价复合物的功能性质都优于非共价复合物。β-LG-Glc-EGCG con的乳化性、乳化稳定性和起泡性、起泡稳定性都优于β-LG-EGCG-Glc con,而非共价复合物之间差距不大。     

乳铁蛋白-EGCG共价复合物对鱼油乳液稳定性和消化特性的影响

通过碱处理法制备乳铁蛋白（lactoferrin,LF）-表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）共价复合物,研究LF-EGCG物理混合物和共价复合物对鱼油乳液流变性质、氧化稳定性和体外消化特性的影响。由于EGCG与LF共价结合,蛋白质分子质量增加,使得共价复合物制备的乳液黏度增加（其黏度分别是单一蛋白乳液和物理混合物乳液的2.74 倍和1.42 倍）,物理稳定性显著增强（在55 ℃恒温、避光贮藏15 d后仍能保持较好的流动性）。与LF稳定的乳液相比,物理复合或共价结合的LF-EGCG能够有效地抑制贮藏过程中鱼油氧化（贮藏第15天时,LF、物理混合物和共价复合物稳定的鱼油乳液中脂质的硫代巴比妥酸反应物值分别为2.25、0.75 nmol/g和0.70 nmol/g）。在体外消化过程中,共价复合物稳定的鱼油乳液能够更好地抑制聚集体的产生,在一定程度上延缓脂肪酸的释放。本研究能够为合理设计鱼油递送系统提供一定参考。     

微射流技术对食品大分子物质性质及结构的影响

利用动态高压微射流（dynamic high-pressure microfluidization,DHPM）对纤维多糖（AX）、蛋白质（WP）、淀粉（PS）和果胶（PE）进行均质处理,通过分析处理前后大分子物质的粒径、扫描电镜图、X射线衍射图、紫外吸收光谱、傅里叶红外光谱以及表观黏度,研究DHPM对大分子物质基本性质和结构的影响。结果发现：经DHPM处理后4种大分子物质粒径均减小,平均粒径分别减小了79%、31%、68%、63%,大分子颗粒表面在剪切力作用下受到了不同程度的剪切和破碎,AX和PS的表观黏度增加,WP和PE则减少;X射线衍射、紫外吸收光谱及傅里叶红外光谱结果显示均质前后的特征峰及官能团未发生改变,而吸收峰的强度有不同程度的变化,样品部分吸收峰发生红移,AX、PS、PE的O—H氢键缔合伸缩振动特征吸收峰峰宽增加,WP二级结构α-螺旋消失,β-折叠含量减少,结晶度下降。可以看出,DHPM处理使4种大分子物质的性质及结构产生一定的改变。该研究为食品大分子物质的深度开发与资源利用提供了理论依据。     

动态高压微射流技术对β-乳球蛋白微观结构的影响

采用动态高压微射流技术（DHPM）处理β-乳球蛋白,研究DHPM对β-乳球蛋白微观结构的影响。实验结果表明,未处理的β-乳球蛋白的微观结构表现为球体且分布紧凑。随着DHPM处理压力的逐渐增大,β-乳球蛋白分子被逐渐打散,大部分颗粒逐渐变细。然而仅有小部分β-乳球蛋白分子在经过100MPa和150MPa处理后,发生了部分团聚现象,分别形成不同聚集体的形貌结构。     

不同来源乳铁蛋白及乳铁蛋白素对小鼠脾淋巴细胞增殖影响的比较

以牛乳清乳铁蛋白（bovine whey lactoferrin,LFW）、牛初乳乳铁蛋白（bovine colostrum lactoferrin, LFC）、人乳铁蛋白（human lactoferrin,LFH）、牛乳铁蛋白素（bovine lactoferricin,LfcinB）和人乳铁蛋白 素（human lactoferricin,LfcinH）为研究对象,研究其对小鼠脾淋巴细胞增殖的影响并比较不同来源乳铁蛋白 （lactoferrin,LF）及乳铁蛋白素（lactoferricin,Lfcin）作用效果的差异性。采用CCK-8法检测不同来源的LF与 Lfcin作用小鼠脾淋巴细胞24、48、72 h后,及其与丝裂原共同作用对小鼠T、B淋巴细胞增殖作用的影响。结果显 示：LF与Lfcin均在48 h时对小鼠脾淋巴细胞增殖的促进效果最好,且在一定质量浓度范围内促进效果随质量浓度升 高而加强;LF与Lfcin均在一定质量浓度范围内提高刀豆蛋白A诱导的T淋巴细胞的增殖和脂多糖诱导的B淋巴细胞 的增殖。结果表明：两种牛乳铁蛋白（bovine lactoferrin,LFB）及LfcinB可替代LFH应用于婴幼儿配方产品中以提 高婴幼儿免疫能力,LFB推荐添加质量浓度为0.50～2.00 mg/mL,Lfcin推荐添加质量浓度为75～125 μg/mL。     

pH对乳糖-乳铁蛋白复合物结构及理化特性的影响

为了探究热处理条件下不同pH对乳铁蛋白(LF)-乳糖复合物的结构与理化特性的作用,对LF-乳糖复合物的浊度、粒径、微观结构和构象进行测定。结果表明：在不同pH（2~10）条件下,LF-乳糖以不同的结构存在。在pH为2和4的酸性环境中,LF和乳糖处于共溶状态,热处理前后溶液浊度没有明显变化,其粒径维持在10 nm左右。在弱酸性和碱性环境中（6~10）,LF和乳糖形成复合物,其溶液浊度明显增大,其粒径也从约10 nm增加到约460 nm。扫描电镜（SEM）显示了其结构从零散分布到线性聚集,再到团状聚集的过程。红外光谱（FT-IR）显示了复合物形成后的酰胺带和890 cm-1处β-糖苷键的特征峰的变化。圆二色谱（CD）显示α-螺旋随pH增加从20.62%减少到18.23%,β-折叠则逐渐从33.35%增加到37.17%。SDS-PAGE图谱表明,碱性条件下生成了以非二硫键为主要作用力的聚集体。研究结果拓展了乳铁蛋白在食品中的应用。     

Effect of dynamic high-pressure microfluidization on physicochemical,structural, and functional properties of oat protein isolate

Dynamic high-pressure microfluidization (DHPM) technology was used to treat oat protein isolate (OPI) to improve its functional properties and broaden its application in food processing. Results showed that the particle size of OPI was significantly reduced by 70.96%, and the absolute zeta potential increased by 33.51% at a DHPM pressure of 120 MPa. The major subunits of OPI were not degraded, but the secondary structures of OPI were altered with increasing α-helix, β-sheet, and β-turn structures and decreasing random coil after DHPM treatment. In addition, the significant increase in the surface hydrophobicity and free sulfhydryl content, as well as fluorescence quenching of OPI indicated the conformational expansion and rearrangement of OPI. Additionally, the changes in OPI structures affected its functional performance. DHPM treatment at 120 MPa significantly improved the solubility, water and oil holding properties, and emulsifying and foaming abilities of OPI. Therefore, DHPM treatment can improve the functional properties of OPI, which provides a new idea for expanding the application of OPI in food processing.     

果胶结构、提取方法及乳化特性研究进展

果胶是一种重要的酸性大分子多糖物质,具有良好的凝胶性、增稠性和乳化特性,被广泛应用于食品加工业中。果胶的结构及乳化特性会受到提取方法的影响,本文综述了果胶的分子结构及不同提取方法的应用特点,并介绍了影响果胶乳化特性的结构因素(蛋白质、阿魏酸、乙酰基、中性糖侧链、分子量)和环境因素(果胶浓度、油相浓度、pH、盐离子)及果胶与蛋白质结合用于稳定乳化液的研究现状,最后对果胶的研发前景进行展望,以期为果胶的开发和应用提供一定的理论参考。     

The Emulsifying and Emulsion‐Stabilizing Properties of Pectin: A Review

Pectin, a plant cell wall polysaccharide, is a natural multifunctional ingredientwhich imparts textural and rheological properties to a wide range of food systems. Up to the last decade, most pectin blank applications stemmed from its gel‐forming ability. Nowadays, pectin is gradually gaining acceptance as an effective emulsifier in numerous food applications. Accordingly, the emulsifying and emulsion‐stabilizing properties of this hydrocolloid are increasingly being assessed. These pectin functionalities are controlled by both the properties of the carbohydrate moieties and of the often attached protein groups. Generally, the protein moiety, feruloyl, and acetyl groups, play a major role in pectin emulsifying activities, while the emulsion‐stabilizing properties of the polymer are controlled by the homogalacturonan (HG) domain and the neutral sugar side chains of the rhamnogalacturonan‐I (RGI) structural element. However, the neutral sugar side chains might obstruct the accessibility of pectin hydrophobic species to the oil/water interface, thereby hampering emulsification. In addition, the contribution of HG to emulsion stabilization might be dependent on the polymer HG:RGI ratio. Hence, the influence of pectin structural features on the polymer emulsifying potentials is yet to be fully unraveled, as identified in this review. Furthermore, the emulsifying and emulsion‐stabilizing properties of pectin are influenced by the composition of emulsions.     

动态高压微射流对小麦面筋蛋白功能性质影响的研究

本文研究了动态高压微射流对小麦面筋蛋白功能性质的影响及其机理。结果表明:微射流对面筋蛋白功能性质的改变与其压力和蛋白浓度密切相关。随着压力的升高,在大于等于4%浓度时,溶解度先增大后减小,在80 MPa时达到最大值,在小于4%浓度时正好相反;蛋白浓度为4%时,起泡性减小,泡沫稳定性、乳化性和乳化稳定性增大,在100 MPa时达到最大,其他浓度例如2%和6%时正好相反。SDS-PAGE和DSC图谱显示,微射流使面筋蛋白大分子量亚基被破坏,形成新的具有更加紧凑的空间结构的水溶性聚集体,从而改变了面筋蛋白的功能特性。     

Degradation of high-methoxyl pectin by dynamic high pressure microfluidization and its mechanism

High-methoxyl pectin was degraded by dynamic high pressure microfluidization (DHPM). It was found that apparent viscosity, average molecular weight and particle size of pectin decreased, whereas the amount of reducing sugars increased with increasing DHPM pressure. At the same time, the surface topography of pectin was changed from large flake-like structure to smaller porous chips. The mechanism of DHPM-induced degradation of pectin was also investigated. Fourier transform infrared spectra showed DHPM had no effect on the primary structure of pectin. On the other hand, reducing sugars content increased linearly with decreasing average molecular weight, suggesting the degradation may derive from the rupture of glycosidic bond. The breakdown of glycosidic bond may not only result from intensive mechanical forces but also from acid hydrolysis, which was evidenced in the reduction of degradation when the concentration of H⁺ was lowered. In addition, neither β-elimination nor demethoxylation occurred with DHPM. Based on these results, a model was proposed to illustrate the degradation of pectin induced by DHPM.     

蒸汽爆破技术对苹果果胶乳化特性的影响

明确蒸汽爆破处理对苹果果胶乳化性的影响。对苹果果胶进行蒸汽爆破处理,研究汽爆压力和汽爆时间对果胶乳化活性和乳化稳定性的影响,并比较汽爆前后果胶粒径和果胶表观黏度,通过显微镜观察乳化液的微观结构。结果表明,果胶乳化活性和乳化稳定性随着爆破压力和爆破时间的增加而增加,与未汽爆处理的果胶相比,在0.6 MPa/120 s处理条件下,果胶乳化活性由21.05 m2/g增加至43.61 m2/g;乳化稳定性由89.60 min增加到125.92 min;乳化液平均粒径由143.1 μm减少为100 μm;乳化液表观黏度显著上升,显微观察显示汽爆后的苹果果胶乳化液滴更加均匀细密。蒸汽爆破处理苹果果胶提高了乳化性,使果胶乳化性整体改善。     

Emulsifying and structural properties of pectin enzymatically extracted from pumpkin

The present study investigated the emulsifying and structural properties of pectin enzymatically extracted from pumpkin. Pumpkin pectin fraction A was obtained from raw pumpkin with an enzymatic preparation of cellulase and α-amylase. Pumpkin pectin fraction B was achieved by treating the fraction A solution with pronase to reduce protein content. According to the findings (on protein content, galacturonic acid content, neutral sugar composition, and molecular weight distribution), the pronase treatment could remove protein from the fraction A without considerably influencing any other chemical and molecular properties. Moreover, the fraction A exhibited emulsifying properties in water and oil mixture, whereas the removal of protein in the fraction B resulted in the loss of emulsifying properties. The FT-IR and 1D NMR analysis revealed that the backbone of pumpkin pectin is mainly composed of α-1,4-d-galacturonic acid in which a considerable portion of galacturonic acid residues is present as methyl esters, and some l-rhamnose are involved in the linear region of the backbone through α-1,2-linkages.     

Preparation and characterisation of surface‐active pectin from soya hulls by phosphate‐assisted subcritical water combined with ultrasonic treatment

Surface‐active pectin was efficiently extracted from soya hull using phosphate‐assisted subcritical water combined with ultrasonic treatment (PASW‐UT). The physicochemical and functional properties of soya hull pectin (PSHP) were evaluated. Compared to pectin prepared by traditional acid extraction (ASHP), the yield and purity of PSHP were significantly increased, as well as PSHP also contained more protein moiety and displayed better emulsifying and foaming properties. However, the emulsifying and foaming properties of protein‐depleted soya bean hull pectin (PDSHP) were markedly decreased as compared to PSHP, which was supported by data of dynamic interfacial tension of pectins, suggesting that the emulsifying and foaming capacity of PSHP should be mainly ascribed to the existence of more extensin, as evidenced by the results of hydroxyproline content. In further comparison with commercial sugar beet pectin (SBP), the PSHP exhibited similar emulsifying properties with SBP over the pH range of 2–6. Moreover, the foam ability and stability were even higher than those of SBP, especially at pH 4.0. These findings suggest that PASW‐UT could be used as an effective strategy to prepare novel surface‐active pectin from soya hull.     

Improved emulsion stabilizing properties of whey protein isolate by conjugation with pectins

Functional properties of glyco-protein conjugates of the anionic polysaccharide pectin with whey protein isolate, obtained by dry heat treatment at 60 °C for 14 days, have been investigated in O/W emulsions containing 20% (w/w) soybean oil and 0.4% (w/w) protein both at pH 4.0 and 5.5. Emulsion stabilizing properties of mixtures and conjugates were compared at five protein to pectin weight ratios by determining changes in droplet size distribution and extent of serum separation with time. The results indicated that the dry heat-induced covalent binding of low methoxyl pectin to whey protein, as shown by SDS-PAGE, led to a substantial improvement in the emulsifying behaviour at pH 5.5, which is near the isoelectric pH of the main protein β-lactoglobulin. At pH 4.0, however, a deterioration of the emulsifying properties of whey protein was observed using either mixtures of protein and pectin or conjugates.The observed effects could be explained by protein solubility and electrophoretic mobility measurements. The protein solubility at pH 5.5 was hardly changed using mixtures of protein and low methoxyl pectin or conjugates, whereas at pH 4.0 it was decreased considerably. Electrophoretic mobility measurements at pH 5.5 revealed a much more pronounced negative charge on the emulsion droplets in the case of protein–pectin conjugates, which clearly indicated that conjugated pectin did adsorb at the interface even at pH conditions above the protein's iso-electric point. Hence, the improved emulsifying properties of whey protein isolate at pH 5.5 upon conjugation with low methoxyl pectin may be explained by enhanced electrosteric stabilization.Comparing two different commercial pectin samples, it was clearly shown that the dextrose content during dry heat treatment of protein–pectin mixtures should be as low as possible since protein–sugar conjugates not only resulted in increased brown colour development, but also gave raise to a largely decreased protein solubility which very badly affected the emulsifying properties.