Vanillin Interaction with Milk Protein Isolates in Sweetened Drinks

The impact of heat processing and emulsifier addition on the interaction of vanillin and sodium caseinate and whey protein isolate was examined in a model system. Free vanillin in the protein drink was evaluated by a sensory panel and HPLC. Sensory analysis indicated that emulsifier, heat × protein, and heat × emulsifier affected perception of vanillin flavor. Analysis of free vanillin by HPLC indicated only a significant protein effect, with sodium caseinate interacting more with vanillin than did whey protein isolate. No correlation was found between sensory and HPLC results.     

Drug release from hydrogel containing albumin as crosslinker

Albumin is the major plasma protein and acts as a physiological carrier for various compounds including drugs. To take advantage of the drug-binding ability of albumin for a drug delivery system, we have prepared hydrogels consisting of acrylamide (AAm) and bovine serum albumin (BSA) by introducing three to four vinyl groups into one BSA molecule and subsequently copolymerizing it with AAm. The resultant hydrogel was solubilized by trypsin treatment, since BSA served as a crosslinker in the hydrogel. The BSA-crosslinked hydrogel (BSA-AAm hydrogel) was loaded with salicylic acid or sodium benzoate and their release was investigated. The BSA-AAm hydrogel released much more salicylic acid than sodium benzoate. In addition, the amount of released salicylic acid increased with the BSA content of the hydrogel, despite a decrease in the swelling ratio of the hydrogel. On the other hand, the amount of released sodium benzoate increased with the swelling ratio. When a hydrogel crosslinked with N,N'-methylenebis (acrylamide) was used as a control, both drugs showed release tendencies similar to that of sodium benzoate from the BSA-AAm hydrogel. Furthermore, the salicylic acid release was sustained longer on the BSA-AAm hydrogel than the sodium benzoate release. Taken together, it is thought that albumin in the BSA-AAm hydrogel preferentially adsorbs salicylic acid and contributes to the high drug loading and the sustained release of salicylic acid.     

Aspergillus flavus growth in the presence of chemical preservatives and naturally occurring antimicrobial compounds

The combined effects of water activity ([a(w)] 0.99 or 0.95), pH (4.5 or 3.5) and antimicrobial agent (potassium sorbate, sodium benzoate, sodium bisulfite, carvacrol, citral, eugenol, thymol, or vanillin) concentration (0, 100, 200 up to 1800 ppm) on the growth of Aspergillus flavus were evaluated in potato dextrose agar (PDA). Mold spore germination time and radial growth rates (RGR) were significantly (p<0.05) affected by the variables. For equal antimicrobial concentration, reduction in pH or a(w) had important effects, lowering RGR and delaying germination time. Depending on a(w) and pH, increase in antimicrobial concentration slightly reduced RGR until a critical concentration where RGR was drastically reduced or mold growth was inhibited. Germination time increased as antimicrobial agent concentration increased and when a(w) and pH decreased. Important antimicrobial differences were observed, being, in general, the natural antimicrobials less pH-dependent than chemical preservatives. A. flavus exhibited higher sensitivity to thymol, eugenol, carvacrol, potassium sorbate, sodium bisulfite, and sodium benzoate (at pH 3.5) than to vanillin or citral.     

香草醛分子印迹聚合物微球的合成及表征

香草醛作为食品中一种重要的调味剂,可以从热带兰花香荚兰的种子中找到。本文以香草醛(VAN)为模板分子,a-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,二甲基亚砜(DMSO)为溶剂,分别采用沉淀聚合法、悬浮聚合法、本体聚合法制备了香草醛分子印迹聚合物(微球)(MIPs)。通过紫外光谱(UV)、傅里叶变换红外光谱仪(FT-IR)研究了模板分子与功能单体之间的相互作用和最佳配比,利用透射电子显微镜考察了分子印迹聚合物的微观形貌。采用平衡和等温吸附实验对印迹聚合物的吸附性能进行了研究。实验表明,MAA与VAN之间通过氢键相互作用,沉淀聚合法制备的MIPs具有均匀规则的球状结构,且表现出对VAN更好的结合能力,具有较高的特异识别性。     

Proteolytic regulation of the extent of dietary proteins with skin grape proanthocyanidin and anthocyanidin's interactions

During technological processing, proanthocyanidins and anthocyanidins could be partly lost due to the complexation phenomena, affecting food and beverage nutritional properties, organoleptic properties and health-promoting potentials. A common issue is encountered when processing food and beverage which is binding of phenolics to dietary proteins. The present investigation aims at evaluating the proteolysis contribution, using pure protease (Pepsin, 3000 units g⁻¹), to protein–anthocyanidin and protein–proanthocyanidin interactions. Bovine serum albumin (BSA), ovalbumin (OVA) and casein (CAS) dietary protein models were used. High-performance liquid chromatography coupled to diode array detector (HPLC-DAD) and size exclusion chromatography analyses proved that pepsin treatment significantly (P > 0.05) decreased the ratio of flavonoids’ interaction with tested proteins . The proteolysis reduced anthocyanidin interactions with CAS, OVA and BSA by 64.88%, 57.37% and 42.87% respectively. Similarly, proanthocyanidins interaction with CAS, OVA and BSA were reduced by 34.23%, 13.74% and 2.39% respectively. This study provides the basis to develop innovative technologies to limit protein–flavonoid complexation during food and beverage processing.     

Study on the interaction of food colourant quinoline yellow with bovine serum albumin by spectroscopic techniques

The interaction of a food colourant, quinoline yellow (Qy), and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorometry, FT-IR and circular dichroism (CD) techniques. The experimental results indicated that the quenching mechanism of BSA by the dye was a static procedure. Various binding parameters were evaluated. The negative value of ΔH, negative value of ΔS and the negative value of ΔG indicated that van der Waals force and hydrogen bonding play major roles in the binding of Qy and BSA. Based on Forster's theory of non-radiation energy transfer, the binding distance, r, between the donor (BSA) and acceptor (Qy) was evaluated. The results of CD and UV-vis spectroscopy showed that this dye could bind to BSA and the conformation of BSA changed.     

The determination of protein hydrophobicity. 2. Determination of the of protein binding of sodium dodecyl sulfate with the use of the ultracentrifuge]

The interaction between sodium dodecylsulphate (SDS) and the proteins bovine serum albumin (BSA) and ovalbumin, respectively, was studied using a synthetic boundary cell of an ultracentrifuge. A method for the determination of protein-bound SDS is described. The SDS binding capacity of BSA is found to be 250 +/- 50 micrograms SDS per 500 micrograms of BSA. The amount of SDS bound by ovalbumin is so low that the procedure cannot be recommended for this protein.     

Effect of moderate electric field on structural and thermo-physical properties of sunflower protein and sodium caseinate

Moderate electric field (MEF) was employed to sunflower protein isolate (SPI) and sodium caseinate (CAS) to change their structural and thermo-physical properties with a non-thermal approach. MEF treatment significantly reduced the average particle size with noticeable changes in the uniformity of SPI and CAS solutions. A maximum of 10% reduction in the surface tension was observed for 0.2% w/w SPI sample by applying 150 V for 20 s. This effect was less pronounced for CAS samples and for the protein concentration of 2% w/w. FTIR spectra provided an increased α-helix content for SPI inducing a bulkier, loosened and more hydrophilic structure which is unlikely for CAS. Intrinsic Fluorescence Spectroscopy revealed that MEF treatments changed the tertiary structures of SPI and CAS. Denaturation temperatures and enthalpies of the SPI and CAS samples were decreased by MEF treatments.     

Interaction of Vanillin with Soy and Dairy Proteins in Aqueous Model Systems: A Thermodynamic Study

ABSTRACT: Interactions of vanillin with soy, casein, and whey proteins were studied in aqueous model systems using a thermodynamic approach. Vanillin-protein binding was examined at 12 and 4 °C using 3 proteins and 6 vanillin concentrations. The results were analyzed using a Klotz plot. Number of binding sites (n) and dissociation constants (K_d) were derived from the plots. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) for the bindings were calculated. Under identical experimental conditions, whey protein was found to have higher affinity to vanillin than the other 2 proteins. Bindings of vanillin with casein and whey protein were enthalpy driven, while the interaction of vanillin with soy protein was highly entropy driven. The results inferred that conformational changes of soy protein might be important in binding of vanillin.     

大叶冬青皂苷与牛血清蛋白的相互作用研究

为研究不同温度下大叶冬青皂苷G（Latifoloside G）、大叶冬青皂苷C（Latifoloside C）及苦丁皂苷G（Kudinoside G）与牛血清白蛋白（BSA）的相互作用情况，为大叶冬青皂苷在体内运输及作用机制研究提供实验依据，本文采用荧光光谱法研究小分子与蛋白的结合机制、结合模式、结合常数和结合位点等，采用圆二色谱法研究蛋白质的构象变化。结果表明:三种皂苷均能有效猝灭BSA内源荧光，Kudinoside G为静态猝灭，Latifoloside G、Latifoloside C为动态猝灭。随着三种药物小分子浓度的增加，BSA的内源荧光强度降低，两种温度下BSA的最大发射峰皆发生轻微蓝移，三种皂苷的发射波长皆由347 nm蓝移到345 nm，三种皂苷与BSA结合能力的顺序为Latifoloside G>Latifoloside C>Kudinoside G。Kudinoside G与BSA之间主要作用力类型为氢键和范德华力，Latifoloside G及Latifoloside C与BSA之间主要作用力为疏水作用。发现Latifoloside G和Kudinoside G两种小分子与BSA的结合能力与C-28位所连的极性基团有关，且齐墩果烷型的Latifoloside C比Kudinoside G更易于插入到BSA的疏水腔中。圆二色光谱表明，三种皂苷与BSA的结合均可使BSA内部结构环境发生改变，α-螺旋含量增加，微环境极性减小，疏水性增加。     

复凝聚法和食用油双层微胶囊化香兰素研究

微胶囊化香精,使其具有热缓释性能,从而减少香兰素在食品烘焙过程中的损失.选用壳聚糖聚阳离子及海藻酸钠聚阴离子为壁材,在溶解有香兰素的食物油表面形成多层包覆结构.真空冷冻干燥脱水获得微胶囊成品.根据微胶囊微观形态、产率和效率,对制备工艺进行评价.结果表明最佳制备条件为:香兰素与油脂质量比为1:20,乳化剂为质量比1:1的吐温-80和司盘-60用量为0.1%,海藻酸钠:壳聚糖质量比为2:3,壳聚糖添加速度为0.01g/min.热重分析和烘焙实验证实,微胶囊产品较之原始的香兰素纯品,耐热性能得到明显提升.     

Interactions in bovine serum albumin–calcium alginate gel systems

Young's modulus of heat-denatured gels of calcium alginate and bovine serum albumin (BSA) was determined and compared to the modulus of BSA gels containing sodium alginate and to pure BSA gels. Ionic strength, pH, and calcium concentration were varied. The BSA/Ca-alginate gels were either prepared with -glucono-δ-lactone (GDL) and CaCO₃ to induce alginate gelation before the gelation of BSA, or by soaking heat-denatured BSA/Na-alginate gels in a CaCl₂ solution. BSA/Ca-alginate gels were stronger than BSA/Na-alginate gels at all conditions, and stronger than pure BSA gels up to higher pH values and up to somewhat higher ionic strengths than BSA/Na-alginate gels. The strength of BSA/Ca-alginate gels was highly dependent on the strength of the alginate gel. This was shown by variation of the calcium concentration and by soaking the gels in EDTA, NaCl, and CaCl₂ solutions. When BSA/Na-alginate or BSA/Ca-alginate gels prepared at optimum conditions were soaked in solutions of higher ionic strength or pH, no reduction in gel strength was observed. Consequently, they were much stronger than gels that were prepared directly at high pH or ionic strength. The results may suggest that the alginate network in a BSA/Ca-alginate gel increases the effectiveness of electrostatic BSA-alginate cross-links or entanglements. However, other explanations are also possible.     

Comparison performances of membrane bioreactor and conventional activated sludge prcesses on sludge reduction induced by Oligochaete

Pilot-scale experiments were carried out to compare sludge reduction induced by Oligochaete in a submerged membrane bioreactor (MBR) and a conventional activated sludge (CAS) reactor for 345 d. Worm growth in the CAS reactor was much better than in the MBR. The average worm density of the aeration tank in the CAS reactor was 71 total worms/mg of volatile suspended solids (VSS), much higher than that in the MBR (10 total worms/mg of VSS). Worms did not naturally produce in the MBR, and the dominant worm type in the MBR depended on sludge inoculation from the CAS reactor. Only two types of worms were found in the MBR, Aeolosoma hemprichicii and Nais elinguis. Worm presence and disappearance in the MBR alternated. Worms in the CAS reactor occurred nearly throughout the operating period and were continuously maintained at over 30 total worms/mg of VSS in the aeration tank for 172 d. Three types of worm were found in the CAS reactor, A. hemprichicii, Pristina aequiseta, and N. elinguis, but P. aequiseta was present only occasionally. The alternating dominance of worm types in both reactors changed between Aeolosoma and Nais, and the time of Aeolosoma dominance was longer than that of Nais dominance. Worm growth in the MBR contributed to neither sludge reduction nor improvement of sludge settling characteristics because of low density. But worm presence and bloom in the CAS reactor greatly decreased sludge yield and improved sludge settling characteristics at high density. Both the average sludge yield (0.17 kg of suspended solids (SS)/kg of chemical oxygen demand removed (CODremoved)) and sludge volume index (60 mL/g) in the CAS reactor were much lower than those in the MBR (0.40 kg of SS/kg of CODremoved and 133 mL/g). Nais had more potential for sludge reduction than Aeolosoma. Worm growth had little impact on effluent quality in the MBR but affected effluent quality very much in the CAS reactor.     

Multispectroscopic studies on the interaction of 2-tert-butylhydroquinone (TBHQ), a food additive,with bovine serum albumin

The interaction of 2-tert-butylhydroquinone (TBHQ) and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorimetry, circular dichroism (CD) and FT-IR techniques. The experimental results indicated that the quenching mechanism of BSA by TBHQ was a static procedure. Various binding parameters were evaluated. The negative value of ΔH, positive value of ΔS and the negative value of ΔG indicated that hydrophobic and hydrogen bonding interactions play major roles in the binding of TBHQ and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance, r, between the donor (BSA) and acceptor (TBHQ) was evaluated. The results of CD, UV–vis and FT-IR spectroscopy showed that the binding of TBHQ to BSA induced conformational changes in BSA.     

STABILIZATION OF GROUND GARLIC COLOR BY CYSTEINE, ASCORBIC ACID, TRISODIUM PHOSPHATE AND SODIUM METABISULFITE

Various organic and inorganic compounds at different concentrations were added to ground garlic as a means of controlling changes in color. Among the compounds tested, cysteine (C), ascorbic acid (A), sodium metabisulfite (S) and trisodium phosphate (P) were found effective in preventing a change in color towards greening. When these compounds were mixed at 0.1 M level, their binary mixtures (CS, AS, SP, AC) and ternary/quaternary mixtures (CAP, CAS, CSP, CASP) turned out to be even more effective for sustaining the original color values (L = 45, a = -2, b = 10) of ground garlic. Although the controlling effect was somewhat decreased with a reduction in mixture concentration from 0.1 to 0.03 M, the majority of mixtures (CS, SP, CAP, CAS, CSP and CASP) still maintained their effectiveness in color control.     

Design of a fungal bioprocess for vanillin production from vanillic acid at scalable level by Pycnoporus cinnabarinus

The biotechnological process of vanillin production from vanillic acid by Pycnoporus cinnabarinus was scaled-up at the laboratory level. Vanillin production was studied in two types of bioreactors, a mechanically agitated and an air-lift bioreactor. In the mechanically agitated bioreactor where vanillin was produced in greater quantities, oxygen availability was studied during the growth and production phases. A maximal aeration rate (90l/h equivalent to 0.83 volume of air/volume of medium/min or vvm) during the growth phase and a minimal aeration rate (30 l/h equivalent to 0.28 vvm) during the production phase were necessary to increase vanillin production to 1260 mg/l. Vanillic acid bioconversion to vanillin occurred under the conditions of reduced dissolved oxygen concentration, gentle agitation, high carbon dioxide production and low specific growth rate. However, under these conditions, vanillin production was accompanied by a significant amount of methoxyhydroquinone. Vanillin over a concentration of 1000 mg/l was shown to be highly toxic to the growth of P. cinnabarinus on agar medium. The application of selective XAD-2 resin led to a reduction of vanillin concentration in the medium, thus limiting its toxicity towards the fungal biomass as well as the formation of unwanted by-products such as methoxyhydroquinone and allowed the concentration of vanillin produced to reach 1575 mg/l.     

Aspergillus flavus dose-response curves to selected natural and synthetic antimicrobials

The effects of selected concentrations of antimicrobials from natural (vanillin, thymol, eugenol, carvacrol or citral) or synthetic (potassium sorbate or sodium benzoate) origin on Aspergillus flavus lag time inoculated in laboratory media formulated at water activity (a(w)) 0.99 and pH 4.5 or 3.5, were evaluated. Time to detect a colony with a diameter > 0.5 mm was determined. Mold response was modeled using the Fermi function. Antimicrobial minimal inhibitory concentration (MIC) was defined as the minimal required inhibiting mold growth for 2 months. Fermi function successfully captured A. flavus dose-response curves to the tested antimicrobials with a highly satisfactory fit. Fermi equation coefficients, Pc and k, were used to compare antimicrobials and assess the effect of pH. Important differences in Pc and k were observed among antimicrobials, being natural antimicrobials less pH dependent than synthetic antimicrobials. A large Pc value represents a small antimicrobial effect on A. flavus lag time; thus, high concentrations are needed to delay growth. A. flavus exhibited higher sensitivity to thymol, eugenol, carvacrol, potassium sorbate (at pH 3.5), and sodium benzoate (at pH 3.5) than to vanillin or citral. MICs varied from 200 ppm of sodium bcnzoate at pH 3.5 to 1800 ppm of citral at both evaluated pHs.     

Fouling of nanofiltration, reverse osmosis, and ultrafiltration membranes by protein mixtures: the role of inter-foulant-species interaction

Protein fouling of nanofiltration (NF), reverse osmosis (RO), and ultrafiltration (UF) membranes by bovine serum albumin (BSA), lysozyme (LYS), and their mixture was investigated under cross-flow conditions. The effect of solution chemistry, membrane properties, and permeate flux level was systematically studied. When the solution pH was within the isoelectric points (IEPs) of the two proteins (i.e., pH 4.7-10.4), the mixed protein system experienced more severe flux decline compared to the respective single protein systems, which may be attributed to the electrostatic attraction between the negatively charged BSA and positively charged LYS molecules. Unlike a typical single protein system, membrane fouling by BSA-LYS mixture was only weakly dependent on solution pH within this pH range, and increased ionic strength was found to enhance the membrane flux as a result of the suppressed BSA-LYS electrostatic attraction. Membrane fouling was likely controlled by foulant-fouled-membrane interaction under severe fouling conditions (elevated flux level and unfavorable solution chemistry that promotes fouling), whereas it was likely dominated by foulant-clean-membrane interaction under mild fouling conditions. Compared to nonporous NF and RO membranes, the porous UF membrane was more susceptible to dramatic flux decline due to the increased risk of membrane pore plugging. This study reveals that membrane fouling by mixed macromolecules may behave very differently from that by typical single foulant system, especially when the inter-foulant-species interaction dominates over the intra-species interaction in the mixed foulant system.     

Sensory Evaluation of Binding of Vanillin by Fababean Proteins

Sensory studies were conducted to estimate the perceived vanillin flavor of protein-vanillin systems that contained free vanillin and vanillin bound to fababean protein micellar mass (PMM). Nine panelists used the magnitude estimation technique to evaluate vanillin flavor by tasting. A power function was established from a series of different concentrations of vanillin solutions versus their respective sensory estimates of vanillin flavor and used to convert sensory estimates to perceived vanillin concentrations of the vanillin-PMM slurries. The perceived vanillin in vanillin-PMM systems was directly related to the free vanillin in the corresponding system as determined by HPLC, indicating that only the free vanillin contributed to the flavor. Thus, instruments can be used to predict human perception of a particular flavorant in a food system of flavor-protein interactions.     

牛血清白蛋白与槲皮素及花青素相互作用方式及其纳米颗粒特征的比较

实验比较了牛血清白蛋白(bovine serum albumin,BSA)与脂溶性小分子槲皮素(quercetin,QUE)和水溶性花青素(anthocyanin,ACN)相互作用方式及其纳米颗粒的特征。QUE对BSA荧光猝灭作用为静态猝灭方式(低浓度),但在较高浓度时为静态与动态并存的复合猝灭方式,两者的相互作用力为疏水作用力;ACN对BSA的荧光猝灭程度小于QUE对BSA的,为静态猝灭方式,相互作用力为静电作用力。BSA与QUE的结合常数大于BSA与ACN的结合常数。BSA与QUE或ACN相互作用可形成纳米颗粒,其大小分别为42.5 nm和53.7 nm,ζ-电势分别为-25.64 m V和-21.50 m V。1 mol BSA分子可分别与8 mol QUE和10 mol ACN结合。BSA与QUE形成的纳米颗粒(BSA-QUE)粒径较BSA与ACN(BSA-ACN)的小,且稳定性较高。BSA-QUE对DPPH自由基和ABTS+·清除率均高于BSA-ACN。