用浊度法预测香蕉汁中混浊活性蛋白质和多酚

本研究采用浊度仪测香蕉汁混浊活性(HA)蛋白和多酚含量。为减少内源性蛋白和多酚的影响,分别用聚乙烯吡咯烷酮(polyvinyl polypyrrolidone, PVPP)和膨润土吸附多酚和蛋白质。将单宁酸加入PVPP处理与未处理香蕉汁中,果汁浊度变化与蛋白质含量呈线性相关,在蛋白质含量相同情况下,PVPP处理果汁的浊度较未处理样品小。热处理添加适量明胶的香蕉汁可反映果汁中HA多酚的含量,膨润土处理与未处理系列样品的浊度与其HA多酚含量呈线性相关。浊度法可用于测定香蕉汁中HA蛋白和HA多酚。     

苹果汁中活性蛋白的性质及其稳定化处理研究进展

苹果汁中活性蛋白质 (HAP)是澄清苹果汁产生混浊沉淀的重要原因之一 ,疏水性氨基酸易于和多酚聚集 ,形成混浊。苹果汁中不同浓度的活性蛋白质与低分子的多酚以及简单酚所引起混浊的反应机理不同 ;活性蛋白质的种类、分子结构、反应的时间、温度、反应体系的 pH、无机离子及其离子强度对浑浊的产生有重要影响。单宁酸、膨润土、硅溶胶和聚乙烯聚吡咯烷酮 (PVPP)是有效的稳定化处理措施。     

Effects of various clarification treatments on phenolic compounds and color of apple juice

The purpose of this study was to investigate the changes that occur during conventional clarification using gelatin, bentonite, silica sol, and water-soluble chitosan on the phenolic compounds, antioxidant activity, and color of apple juice. The apple material used in this study was of two varieties: Sampion and Idared. The changes in the polyphenols composition (procyanidins, hydroxycinnamic derivatives, and dihydrochalcones) were monitored through the clarification process. Sampion apple control juices contained more total polyphenols than do Idared apple juices. In Sampion variety apple juice, the dominant polyphenols are the flavan-3-ols (86% of total polyphenols), followed by hydroxycinnamic acids (9.7%), dihydrochalcones (3.0%), and flavonols (1.3%). In Idared apple juice the hydroxycinnamic acids (especially chlorogenic acid) are dominant (about 48% of total polyphenols), followed by flavan-3-ols (40%). However, the concentration of polymeric procyanidins in Sampion apple juices was 62.8 and 46.3% less when the Profloc (chitosan) and gelatin treatments were used, respectively. Aktivbentonit and Puranit (bentonite) supplementary added in juices clarification have some protective effect on polymeric procyanidins only with Profloc treatment. That kind of effect was not observed in Idared apple juices with almost eight times smaller polymeric procyanidins concentration than in Sampion apple juices. The antioxidant activity, measured by the DPPH (1,1-diphenyl-2-picrylhydrazyl radical) method, ranged from 0.20 mg TEAC/mL in Idared apple juice to 0.30 mg TEAC/mL in Sampion apple juice, measured by the ABTS method, from 0.17 to 0.48 mg TEAC/mL, respectively. Clarification of apple juices with chosen clarifying agents has statistically no significant (p>0.05) influence on antioxidant capacity. This study suggests that chitosan can be used as a conventional clarifying aid of apple juices and that treatment has no impact on their biochemical parameters.     

明胶吸附单宁酸的机理探讨及其在蓝莓汁脱涩中的应用

分别用0.01～0.11 g的明胶吸附25 mL 900 mg/L单宁酸模拟溶液,根据明胶吸附量和单宁酸去除率得到明胶的最佳用量,然后研究最佳用量的明胶对25 mL 900 mg/L单宁酸模拟溶液的吸附动力学方程和吸附等温线方程,最后研究明胶对单宁酸质量浓度为900 mg/L的25 mL蓝莓汁的脱涩效果。结果表明：吸附25 mL 900 mg/L单宁酸模拟溶液时,明胶最佳用量为0.03 g,其明胶吸附量为527.5 mg/g,单宁酸去除率为70.33%。明胶吸附单宁酸的过程符合准二级动力学方程,其吸附等温线符合Langmuir吸附方程,为单分子层吸附。当脱除单宁酸含量为900 mg/L的25 mL蓝莓汁的涩味时,明胶用量0.03 g、温度15 ℃、振荡时间20 min,在该条件下,其明胶吸附量为420.8 mg/g,单宁酸去除率为56.11%,脱涩效果良好。     

黑莓清汁贮藏期间二次沉淀的研究

分析了黑莓清汁贮藏六个月后二次沉淀的化学成分,讨论了影响二次沉淀的主要因素。结果表明,冷冻干燥的二次沉淀中含有蛋白质15.67%、多酚50.39%、总糖13.19%、灰分1.73%。氨基酸分析表明黑莓含有较多的脯氨酸等混浊活性蛋白质,而含有组氨酸较多的蛋白质也容易形成二次沉淀。采用气相色谱(GC)、高效液相色谱-质谱联用技术(HPLC-MS)分别分析了黑莓清汁二次沉淀的糖和酚类物质成分。与贮藏前相比,贮藏六个月后,黑莓清汁中的酚酸类、儿茶素及其衍生物大为减少。固体核磁共振检测发现,黑莓清汁二次沉淀中的聚合物是缩合单宁类化合物。在黑莓清汁的贮存过程中,花色苷的C8亲核进攻儿茶素或者表儿茶素的C4,或者儿茶素、表儿茶素的C8亲核进攻花色苷的C4生成缩合单宁,并可能进一步聚合形成多聚体,这些多聚体也会与蛋白质发生相互作用生成二次沉淀。     

单宁酸与麦胶蛋白结合反应的研究

以单宁酸和麦胶蛋白分别作为引起啤酒浑浊的敏感多盼和敏感蛋白的模型物质，用分光光度法对影响单宁酸与麦胶蛋白结合反应的因素进行了研究。发现，麦胶蛋白的浓度影响单宁酸与麦胶蛋白结合的方式，也影响二者的结合比例。反应温度越低、反应时间越长，单宁酸与麦胶蛋白结合反应越完全。在很低的pH值时，单宁酸与麦胶蛋白结合能力很差，在pH4．0附近，单宁酸与麦胶蛋白结合反应较完全。低乙醇浓度下，随着乙醇浓度的上升，单宁酸与麦胶蛋白结合反应程度有所下降，而在较高乙醇浓度下却随之增大。     

鱼皮明胶和多酚组装行为与相互作用

研究不同结构多酚与鱼皮明胶（fish skin gelatin,GLA）间的相互作用及组装行为,期望对水产品加工、副产品的利用和新型食品配料的开发提供科学依据,同时为多酚-蛋白质复合物在食品领域的应用提供理论指导。选取单宁酸（tannic acid,TA）、表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）、没食子酸3 种含有不同数量邻三元酚结构的多酚为研究对象,以体系浊度和复合物粒径为考察指标,探讨多酚添加量、pH值对GLA和多酚体系的组装行为的影响。采用荧光光谱和等温滴定量热法探究多酚与GLA之间的相互作用机制。结果显示：TA、EGCG在一定浓度下均可与GLA发生组装形成多酚-GLA纳米复合物,且随着pH值的变化,体系透光率可实现可逆转变。荧光光谱结果分析发现3 种多酚均可以和GLA形成多酚-GLA复合物导致GLA内源荧光的猝灭,猝灭机制为静态猝灭。等温滴定量热法表明TA和GLA结合的主要作用力为氢键和范德华力,而EGCG和GLA间的相互作用主要为静电相互作用。     

Measurement of protein in tannin-protein precipitates using ninhydrin

A method was tested for quantifying protein in precipitated tannin-protein complexes in which protein was hydrolysed with acid and the amino acids released were measured with ninhydrin. Unlike previously published methods, this technique requires no prior separation of tannin and protein and can be used to compare the binding of different soluble proteins to tannins under identical conditions. The method was used to compare the precipitation of bovine serum albumin, porcine pancreatic protease, β-glucosidase and γ-globulin by tannic acid. The amount of tannic acid required to precipitate maximal amounts of protease and β-glucosidase was approximately 7–8 times that required to cause maximal precipitation of albumin and γ-globulin when tested with 2 mg ml^?1 protein. All protein preparations contained a fraction (10–40% of total protein) which was not precipitated by tannic acid. Protein in tannin-protein precipitates produced in a standard haemanalysis assay were also measured with ninhydrin. Per cent precipitation at each tannic acid concentration as measured with ninhydrin was identical to that determined by haemanalysis within the linear portions of the binding curves produced by the two methods. These results confirm that the ninhydrin method accurately measures precipitation of protein by tannin.     

Antioxidative activity and emulsifying properties of cuttlefish skin gelatin modified by oxidised phenolic compounds

Antioxidative activity and emulsifying properties of cuttlefish skin gelatin modified by different oxidised phenolic compounds including caffeic acid, ferulic acid and tannic acid at different concentrations were investigated. Oxidised phenolic compounds were covalently attached to gelatin as indicated by the decrease in amino groups. Fourier transform infrared spectroscopic studies indicated the presence of an aromatic ring and a hydroxyl group in gelatin after modification. Modified gelatin had the increased antioxidative activity but the decreased surface hydrophobicity. Gelatin modified with 5% oxidised tannic acid had no change in emulsifying properties. Emulsion stability and oxidative stability of menhaden oil-in-water emulsion stabilised by 0.5% and 1.0% gelatin without and with modification by 5% oxidised tannic acid were studied. Both gelatins at a higher concentration (1.0%) yielded an emulsion with a smaller particle size. Modified gelatin inhibited the formation of TBARS in the emulsion more effectively than the control gelatin throughout the 12 days of storage.     

Antioxidative activity and emulsifying properties of cuttlefish skin gelatin–tannic acid complex as influenced by types of interaction

The non-covalent interaction between cuttlefish skin gelatin and tannic acid was observed in gelatin modified with unoxidized tannic acid at pH 7, whereas covalent interaction was found in gelatin modified with oxidized tannic acid at pH 9. Degree of tannic acid incorporation into gelatin via non-covalent interaction was more pronounced than that found via covalent interaction as evidenced by lowered free amino group content and increased total phenolic content and hydroxyl group and aromatic ring determined by FTIR. Gelatin modified with oxidized tannic acid had the slight decrease in surface hydrophobicity, with no changes in particle size distribution of the emulsions. Modification of gelatin with tannic acid, especially via non-covalent interaction, increased in vitro antioxidative activity, compared with the control gelatin. Gelatin modified with tannic acid via covalent interaction rendered the emulsion with high stability and could inhibit lipid oxidation of menhaden oil-in-water emulsion effectively throughout the storage of 12 days.

Industrial relevance

Cuttlefish skin gelatin modified with tannic acid possessing both emulsifying activity and the improved antioxidative activity can be used as a natural and safe additive in food industry. Therefore, cuttlefish skin, a by-product from seafood processing industry, can be produced as the high value added product with wider applications.     

苹果多酚提取浓缩过程中混浊的形成及控制

对苹果多酚提取浓缩过程中的混浊现象进行研究。通过分析苹果多酚提取浓缩液中引起混浊的主要成分,采用离心法脱除混浊中的蛋白质,观测脱除蛋白质前后大孔树脂对苹果多酚吸附解析的影响。结果表明引起混浊的主要成分是蛋白质、多糖、果胶、多酚,低速离心脱除蛋白质后大孔树脂对苹果多酚的比吸附量提高了25%,比解吸量提高了23%。     

新疆红肉苹果多酚的纯化、组成分析与抗氧化活性

本文以新疆红肉苹果为原料,在超声辅助提取红肉苹果多酚的基础上筛选大孔吸附树脂纯化多酚提取物,用高效液相色谱分析纯化后多酚的组成,并以V_C为对照采用体外试验分析其抗氧化活性。结果表明,在5种大孔树脂中NKA-Ⅱ树脂对新疆红肉苹果多酚的吸附和解析效果最好,其静态吸附与解析平衡时间分别为6和10 h;动态吸附和解析试验的最佳纯化工艺为:上样浓度为0.8 mg/mL,上样流速为4.0 BV/h,上样体积为3.5 BV,洗脱液乙醇的浓度为75%;在此条件下,纯化后的新疆红肉苹果多酚的纯度由原来的35%提高至84%。高效液相色谱分析确定纯化后的新疆红肉苹果多酚主要含有10种单酚类物质,其中绿原酸的含量最高(123.15 μg/mL),其次是槲皮苷和原花青素B₂(25.28、21.96 μg/mL)。体外抗氧化试验结果表明,不同浓度多酚对DPPH自由基、羟基自由基、超氧阴离子均具有明显的清除作用,清除率分别达到93.99%(0.1 mg/mL)、99%(0.8 mg/mL)、98%(0.4 mg/mL),并且对脂质过氧化具有明显的保护作用。该试验结果为进一步研究红肉苹果多酚的抗癌活性奠定了基础。     

单宁酸改性明胶脂肪替代物结构及功能性质的研究

为了改善明胶在加热过程中因热稳定性差而出现的融化现象,利用单宁酸改性明胶,探究对改性后明胶脂肪替代物结构及功能性质的影响。利用傅里叶变换红外光谱仪（FTIR）、扫描电镜（SEM）、热重分析（TGA）和冻融稳定性、耐蒸煮性、持水性和质构特性等方法探究单宁酸改性明胶脂肪替代物结构及功能性质的变化。结果表明:在pH为5,明胶与单宁酸质量比为1.2:1,36 ℃加热30 min的情况下,单宁酸与明胶之间官能团相互结合,二者发生化学反应,改变明胶的蛋白质结构,微观结构由致密均匀的团状结构改变为疏松多孔的孔隙结构;冻融稳定性和耐蒸煮性增强,持水性和溶胀能力下降,硬度和咀嚼性增强,弹性、凝聚性和胶着性下降,L*、a*和b*均增加。经过改性后,提高了明胶脂肪替代物热稳定性,改善了明胶脂肪替代物的结构特性,提高产品质地,为多酚改性明胶的脂肪替代物的制备提供理论基础。     

微波辅助响应曲面法优化提取苹果多酚工艺

目的探讨微波辅助法提取苹果果实中所含多酚的最佳提取条件。方法采用微波辅助法对苹果中的多酚进行提取,探讨在微波影响下,其功率、提取时间、料液比以及乙醇浓度对多酚提取率的影响,在单因素实验的基础上,通过响应面分析确定最佳提取工艺。结果各因素对苹果多酚得率的影响由大到小依次为:微波功率乙醇浓度微波提取时间料液比。由微波辅助法提取苹果多酚最佳工艺为:乙醇浓度50%、微波功率640 W、提取时间70 s、料液比1:14(m:V)时,多酚提取率最高为9.92 mg/g。结论由实验结果可知,运用微波辅助法可以快速有效、安全便捷地提取苹果中的多酚类物质,并且能够获得较好的提取率。     

明胶微球的制备及其对多酚的吸附效果

采用乳化法制备明胶微球,利用显微镜和扫描电镜进行形态表征,研究了明胶微球对不同种类多酚的吸附及解吸附作用,考察了明胶微球的重复使用率。结果表明：在pH 3.5、35 ℃条件下吸附120 min时,明胶微球对表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）、安石榴苷和原花青素表现出良好的吸附作用,而对绿原酸吸附能力弱。用蒸馏水80 ℃处理120 min,微球上吸附的多酚可较好地解吸附。当微球多酚质量比为5∶1时,除绿原酸外,其他多酚的吸附率约54%～78%、单位明胶微球多酚吸附值约107～156 μg/mg、解吸率约60%～75%。明胶微球重复利用5 次后对EGCG的吸附率和解吸率仍然可达55%以上,但重复利用8 次后微球吸附性能急剧下降。因此,明胶微球在食品中多酚的去除和回收中具有潜在的应用价值。     

茶多酚对明胶的改性作用

利用不同浓度茶多酚对明胶进行改性,研究明胶改性前后凝胶强度、流变学性质、分子结构以及蛋白质结晶度的变化,并探讨茶多酚作为明胶改性剂的最佳条件。结果表明,2 g/L的茶多酚对明胶凝胶的强度、熔点和凝固点提高最显著;傅里叶红外转换光谱和X-射线衍射的研究结果表明,2 g/L的茶多酚对明胶的交联作用最强。总之,浓度为2 g/L的茶多酚对明胶具有明显的改性作用。     

鞣剂与明胶在不同条件下作用时的电化学行为跟踪研究

用明胶作为生皮胶原的模拟物,使用激光粒度Zeta电位仪比较了无机鞣剂(CrCl3.6H2O)、植物鞣剂(鞣酸)和醛鞣剂(戊二醛)在不同的温度、浓度和pH条件下与明胶反应时Zeta电位的变化规律,并从明胶电化学性质的角度,对不同鞣剂的鞣制机理进行了分析。结果表明,在模拟实际鞣制的条件下,三种鞣剂与明胶的结合物表面都带正电荷,其中鞣酸与明胶的结合物所带的正电荷最高,而质子化的氨基是其正电荷的主要来源;鞣酸主要与明胶分子中的肽键结合;戊二醛与明胶作用以后,由于结合物疏水性的增大,也会导致结合物表面的正电荷增加。实验也证实了铬配离子是与明胶分子中的羧基结合。     

外源添加物质对黑莓清汁花色苷稳定性和抗氧化活性的影响

本文研究了咖啡酸、阿魏酸、单宁酸、黄芩素、茶多酚、没食子酸、原儿茶酸、芦丁等8种外源辅色素对黑莓清汁花色苷辅色效果、热稳定性、光稳定性和体外抗氧化活性的影响。结果表明:咖啡酸、原儿茶酸、茶多酚、没食子酸、单宁酸对黑莓清汁花色苷的辅色效果影响较显著(p<0.05),最适浓度为0.1 mmol/L,而芦丁的最佳辅色浓度为0.4 mmol/L;实验所选辅色素能够在一定程度上提高黑莓清汁花色苷的热稳定性,其中没食子酸、阿魏酸、咖啡酸对其影响效果显著(p<0.05),分别使黑莓清汁花色苷的热降解半衰期延长了6.06、2.07和1.39倍。此外,原儿茶酸、阿魏酸、芦丁能够显著提高黑莓清汁花色苷的光稳定性、DPPH自由基清除能力和总还原力(p<0.05);没食子酸和单宁酸的辅色作用降低了黑莓清汁花色苷的光稳定性。黄芩素、阿魏酸、咖啡酸、芦丁等外源物质可作为黑莓清汁花色苷有效的辅色素。     

The influence of simple and condensed phenolics on the clarification of apple juice by honey

The rate at which polyphenolics of six apple cultivars were able to flocculate (coagulate) with honey proteins was compared. Condensed tannins were primarily responsible for the formation of the flocculates. The activity of tannins with honey proteins was high in the cultivars Red Delicious, Rome, and McIntosh (group A), and lower for the cultivars Jonathan, Golden Delicious, and Rhode Island Greening (group B). In order to understand the differences in clarification rates by cultivars, model systems were used to estimate the effect of simple polyphenolic compounds on the formation of insoluble tannin/protein complexes. The addition of chlorogenic acid or gallic acid to the systems containing honey proteins and tannic acid resulted in a significant decrease in the rate of formation of flocculates, whereas the addition of catechol to the above systems did not affect the flocculation time of tannic acid with honey proteins. A hypothesis is put forward to explain these results.     

Polyphenol-Rich Beverages Enhance Zinc Uptake and Metallothionein Expression in Caco-2 Cells

ABSTRACT: The effect of red wine (RW), red grape juice (RGJ), green tea (GT), and representative polyphenols on Caco-2 cell ⁶⁵Zn uptake was explored. RW, RGJ, and GT enhanced the uptake of zinc from rice matrix. Fractionation of RW revealed that enhancing activity of zinc uptake was exclusively resided in the polyphenol fraction. Among the polyphenols tested, only tannic acid and quercitin stimulated the uptake of zinc while others did not influence the uptake. In tune with these results, only tannic acid and quercitin competed with zinquin (a zinc selective fluorophore) for zinc in vitro. Although all the polyphenols tested appear to enhance the expression of metallothionein (MT), the induction was higher with tannic acid, quercitin, and RW extract. Furthermore, phytic acid abrogated the tannic acid-induced MT expression. These results suggest that polyphenol-rich beverages, tannic acid, and quercitin bind and stimulate the zinc uptake and MT expression in Caco-2 cells.