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1.
The kinetic process of pressure-induced gelation of whey protein isolate (WPI) solutions (20–28%, w/v) was studied using in situ light scattering. The gelation of WPI solutions could be induced by pressurization at 250 MPa, a pressure lower than that reported in other studies. The gelation time decreased with increasing WPI concentration and followed an exponential rule. The relationship of the logarithm of scattered light intensity (I) versus time (t) was linear after the induced time and could be described by the Cahn–Hilliard linear theory. With increasing time, the scattered intensity deviated from the exponential relationship, and the time evolution of the scattered light intensity maximum Im and the corresponding wavenumber qm could be described in terms of the power-law relationship as Im tβ and qm t−α, respectively. These results indicated that phase separation occurred during the gelation of WPI solutions under high pressure. 相似文献
2.
Seddik Khalloufi Marcela Alexander H. Douglas Goff Milena Corredig 《Food research international (Ottawa, Ont.)》2008,41(10):964-972
Concentrations ranging from 0% to 0.33% (w/v) of gum (Emerson and McDuff) were added to the emulsions at pH 7. Particle size distribution, viscosity, ζ-potential, microstructure, and phase separation kinetics of the emulsions were observed. Both polysaccharides and protein coated droplets are negatively charged at this pH, as shown by ζ-potential measurements. At all the concentrations tested, the addition of gum did not affect significantly (p < 0.05) the apparent diameter of the emulsion droplets. At low concentrations (gum 0.075% (w/v)), no visual phase separation was observed and the emulsion showed a Newtonian behaviour. However, at concentrations above the critical concentration of gum, depletion flocculation occurred: when 0.1 flaxseed gum was present, there was visual phase separation over time and the emulsion exhibited shear-thinning behaviour. These results demonstrate that flaxseed gum is a non-interacting polysaccharide at neutral pH; it could then be employed to strengthen the nutritional value of some milk-based drinks, but at limited concentrations. 相似文献
3.
Javier Osés Idoya Fernández-Pan Khalid Ziani Juan I. Maté 《European Food Research and Technology》2008,227(2):623-628
Whey protein isolate (WPI) films acting as oxygen barriers can be used to delay lipid oxidation in foods with high content
in polyunsaturated fatty acids (PUFA). The aim of this work was to study as to what extent WPI films are capable of delaying
lipid oxidation in vegetable oil, as an example of a food rich in PUFA. The effect of plasticizer type (glycerol or sorbitol)
and content (30, 40, 50 and 60%), as well as film thickness (60, 100 and 180 μm) and relative humidity (50 or 75%) were analyzed.
In order to evaluate the film protective capability, specially designed methacrylate cells and an accelerated test of oxidative
rancidity were used. Results obtained showed that WPI films delayed the rancidity in vegetable oil. Films with sorbitol were
more effective than films with glycerol, providing a protection as effective as aluminum foil. Both plasticizer content and
film thickness affected its protective capacity significantly. The thickest films with the lowest plasticizer content provided
the greatest protection against lipid oxidation. Plasticizer content affected film protection much more intensively than thickness.
WPI films presented a more effective protection at 50% RH than at 75% RH. 相似文献
4.
Effect of clay content on the physical and antimicrobial properties of whey protein isolate/organo-clay composite films 总被引:1,自引:0,他引:1
Whey protein isolate (WPI)/Cloisite 30B organo-clay composite films with different amounts of the clay (0, 5, 10, and 20 g/100 g WPI) were prepared using a solution casting method and their properties were determined to assess the effects of clay content on film properties. The resulting films had an opaque appearance, which depended on the amount of clay added, and a similar gloss. However, the composite films were slightly less transparent compared to the transparent neat WPI films. Film properties, such as surface color and optical properties, varied depending on clay content. The haze index of the WPI/clay composite films as assessed by surface reflectance decreased indicating that the surface of the films was more smooth and homogeneous. The tensile and water vapor barrier properties of the composite films were also influenced by the amount of incorporated clay. In addition, WPI/Cloisite 30B composite films showed a beneficially bacteriostatic effect against Listeria monocytogenes. 相似文献
5.
Keeichi Sasaki Jean Alamed Jochen Weiss Pierre Villeneuve Luis J. López Giraldo Jérôme Lecomte Maria-Cruz Figueroa-Espinoza Eric A. Decker 《Food chemistry》2010
In oil-in-water emulsions, the physical location of antioxidants has been postulated to be one of the most important factors impacting activity. The purpose of this research was to examine how the esterification of various hydrocarbon chains (C4, C8, or C12) onto chlorogenic acid (CGA) influenced physical properties and antioxidant activity in menhaden oil-in-water emulsions. Both surface activity and partitioning of CGA and its hydrocarbon esters into the lipid phase of oil-in-water emulsions increased with increasing size of the hydrocarbon chain. When CGA and its esters were added to a menhaden oil-in-water emulsion at concentration that resulted in equal free radical scavenging activity, CGA, butyl CGA and octyl CGA had similar antioxidant activity while dodecyl CGA was ineffective. These results suggest that phenolic antioxidants conjugated with hydrocarbon chains are more highly associated with lipid emulsions droplets, but these changes in physical properties did not increase antioxidant activity. 相似文献
6.
Composite films were manufactured using whey protein isolate (WPI), gelatin (G) and sodium alginate (SA) using a simplex centroid design. Tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), tear strength (TT), water vapour permeability (WVP) and oxygen permeability (OP) of films were evaluated. The interactions between biopolymers showed quadratic effects (P < 0.01) on TS, E, PT, TT and WVP values. Scanning electron microscopy (SEM) was performed to investigate the microstructures of composite films. The proportion of ingredients required to produce the optimum composite films was determined to be: WPI (g):G (g):SA (g) = 8.0:12.0:5.0. Overall, films (WPIGSA-9) produced using the combination of WPI (g):G (g):SA (g) = 10.0:16.0:14.0 demonstrated the best barrier to oxygen (8.00 cm3 μm/m2 d kPa); while films (WPIGSA-1) showed the best barrier to water vapour (48.04 g mm/kPa d m2); films (WPIGSA-6) using the combination of WPI (g):G (g):SA (g) = 10.0:17.5:22.5 had the best mechanical properties of all of the experimental composite films tested. 相似文献
7.
Dynamic oscillatory and steady-shear rheological tests were carried out to evaluate the rheological properties of whey protein
isolate (WPI) stabilized emulsions with and without hydrocolloids (pectin and guar gum) at pH 7.0. Viscosity and also consistency
index of emulsions increased with hydrocolloid concentration. At γ = 20 s−1, the value of viscosity of the emulsion with 0.5% (w/v) pectin was about fivefold higher than that of the emulsion without
pectin. Flow curves were analyzed using power law model through a fitting procedure. Flow behaviour index of all emulsions
except for containing 0.5% (w/v) guar gum was approximately in the range of 0.9–1.0, which corresponds to near-Newtonian behaviour.
The shear thinning behaviour of emulsions containing 0.5% (w/w) guar gum was confirmed by flow behaviour index, n, of 0.396. Both storage (G′) and loss modulus (G″) increased with an increase in frequency. Emulsions behaved like a liquid with G″ > G′ at lower frequencies; and like an elastic solid with G′ > G″ at higher frequencies. Effect of guar gum was more pronounced on dynamic properties. Phase angle values decreased from 89
to <10° with increasing frequency and indicated the viscoelasticity of WPI-stabilized emulsions with and without pectin/guar
gum. 相似文献
8.
Rheological properties of reduced-fat and low-fat ice cream containing whey protein isolate and inulin 总被引:3,自引:0,他引:3
Ayşe Sibel Akalın Cem Karagözlü Gülfem Ünal 《European Food Research and Technology》2008,227(3):889-895
Instrumental analyses were used to evaluate the rheological properties of regular (10%), reduced-fat (6%) and low-fat (3%)
ice cream mixes and frozen ice creams stored at −18 °C. The reduced-fat and low-fat ice creams were prepared using 4% whey
protein isolate (WPI) or 4% inulin as the fat replacement ingredient. The composition, colour, apparent viscosity, consistency
coefficient, flow behaviour index, hardness and melting characteristics were measured. No effect of WPI or inulin was obtained
on the colour values. Compared with regular ice cream, WPI changed rheological properties, resulting in significantly higher
apparent viscosities, consistency indices and greater deviations from Newtonian flow. In addition, both hardness and melting
resistance significantly increased by using WPI in reduced-fat and low-fat ice creams. Inulin also increased the hardness
in comparison to regular ice cream, but the products made with inulin melted significantly faster than the other samples. 相似文献
9.
The objective of this work was to study the effect of the freezing process on physical properties of whey protein emulsion films with different beeswax content dried at 5 °C. Thickness, microstructure, water vapour permeability, solubility in water, sorption isotherms and mechanical properties were measured in Control and Frozen films. The freezing process did not cause fractures or perforations in films, but films with beeswax showed a change in the appearance of the lipids after freezing. Only films with 40% of beeswax showed a significant increase in the water vapour permeability after freezing. The freezing process did not affect film solubility in water but produced small differences in the equilibrium moisture content values. In the puncture test, the freezing process increased puncture strength and deformation of films without beeswax but those parameters were not affected in films with beeswax. In tensile test, tensile strength and elastic modulus decreased, but elongation was not affected by freezing process. Principal component analysis accomplished an adequate condensation of the date grouping samples according to film formulation and treatment (Control and Frozen films). Indeed, the relationships of sample grouping and measured parameters were enlightened by principal component analysis. In conclusion, whey protein emulsion films were resistant to the freezing process (freezing, frozen storage and thawing) and could be a good alternative as a treatment to preserve the quality of frozen foods. 相似文献
10.
Composite films of whey protein isolate and TiO2 are formed through three simultaneous processes, i.e., the self-assembly of protein–protein, TiO2–TiO2, and the association of protein–TiO2. All the processes could be controlled by adjusting TiO2 concentration in the blended system. The self-assembly of protein–protein molecules constituted the main network of the composite film. A low TiO2 concentration (<0.25%) dispersed the TiO2 nanoparticles in the protein matrix, reinforced the association of protein–TiO2, reduced the ability of UVC absorption, and promoted the fluorescence and tensile strength of the composite films. In contrast, a high TiO2 concentration (>0.25%) enhanced the self-assembly of TiO2–TiO2 nanoparticles, brought fluorescent quenching, and produced a decline of the tensile strength and water vapor permeability. The transmittance of the visible, UVA, and UVB lights showed a first order exponential decay relative to the TiO2 concentration. 相似文献
11.
Effect of whey protein purity and glycerol content upon physical properties of edible films manufactured therefrom 总被引:1,自引:0,他引:1
Óscar L. Ramos Isabel Reinas Sara I. Silva João C. Fernandes Miguel A. Cerqueira Ricardo N. Pereira António A. Vicente M. Fátima Poças Manuela E. Pintado F. Xavier Malcata 《Food Hydrocolloids》2013
12.
13.
The fortification of dairy products with iron is an important approach to delivering iron in required quantities to the consumer. The binding of iron (ferrous sulfate) to two commercial milk protein products, sodium caseinate and whey protein isolate (WPI), dissolved in 50 mM HEPES buffer, was examined as a function of pH and iron concentration. Sodium caseinate had more sites (n = 14) than WPI (n = 8) for binding iron, and the affinity of caseinate to bind iron was also higher than that of WPI. These differences were attributed to the presence of clusters of phosphoserine residues in casein molecules, which are known to bind divalent cations strongly. The amount of iron bound to sodium caseinate was found to be independent of pH in the range 5.5–7.0, whereas acidification (pH range 7.0–3.0) caused a marked decrease in the amount of iron bound to WPI. 相似文献
14.
The formation of electrostatic complexes between whey protein isolate (WPI) and (κ-, ι-, λ-type) carrageenan (CG) was investigated by turbidimetric measurements as a function of pH (1.5–7.0), biopolymer weight-mixing ratio (1:1–75:1 WPI:CG) and NaCl addition (0–500 mM) to better elucidate underlying mechanisms of interaction. Emulsion stabilizing effects of formed complexes was also studied to assess their potential as emulsifiers. Complex formation followed two pH-dependent structure-forming events associated with the formation of soluble (pHc) and insoluble (pH?1) complexes. For both the WPI–κ-CG and WPI–ι-CG mixtures, pHc and pH?1 occurred at pH 5.5 and 5.3, respectively, whereas in the WPI–λ-CG mixture values were slightly higher (pHc = 5.7; pH?1 = 5.5). In all mixtures, maximum turbidity was found to occur near pH 4.5, before declining at lower pHs. Biopolymer mixing ratios corresponding to maximum OD was found to occur at the 12:1 ratio for both the WPI–κ-CG and WPI–λ-CG mixtures, and 20:1 ratio for WPI–ι-CG mixture. The addition of NaCl disrupted complexation within WPI–κ-CG mixtures as levels were raised, whereas when ι-CG and λ-CG was present, complexation was enhanced up to a critical Na+ concentration before declining. Adsorption of CG chains to the small WPI–WPI aggregates during complexation was proposed to be related to both the linear charge density and conformation of the CG molecules involved. Emulsion stability in the mixed systems (12:1 mixing ratio), regardless of the CG type (κ, ι, λ), was significantly higher than individual WPI solutions indicating enhanced ability to stabilize the oil-in-water interface. 相似文献
15.
本文研究了大豆多糖(SSPS)与乳清分离蛋白(WPI)乳状液静电组装,形成乳状液聚集体,考察了不同浓度的SSPS对WPI-乳状液稳定性与流变特性的影响,以期提高体系的粘弹性,形成高流变特性的食品体系。将不同浓度的大豆多糖与2%乳清分离蛋白乳状液(油相为20%)静电组装,分析乳状液的粒径,Zeta-电位,稳定性指数,流变性质和微观结构。结合剪切流变与微流变技术,深入研究了SSPS对乳清分离蛋白(WPI)乳状液流体特性与结构的影响。结果表明:随着SSPS浓度的增加,WPI乳状液的粒径在添加0.25%SSPS时达到峰值(3350±0.35)nm,而后随着SSPS浓度的增加而降低;Zeta-电位绝对值呈递减的趋势,表明SSPS与WPI间产生静电吸附作用;SSPS静电吸附提高WPI乳状液的稳定性;剪切流变结果表明,SSPS浓度为0.5%时,其粘度最大,并在剪切速率为95.8 s-1处其粘度是WPI乳状液粘度的10倍以上;微流变结果表明,0.5%SSPS-WPI乳状液的MSD曲线出现平台区,表明其弹性指数(EI)与宏观粘度指数(MVI)均显著提高达到最大值。微观结构结果表明,0.5%SSPS-WPI乳状液形成均一的乳状液聚集体。本研究将有助于理解大豆多糖与蛋白质乳状液的相互作用,同时为低脂高流变特性的食品(如蛋黄酱、调味汁、巧克力和植脂奶油等)生产提供理论指导。 相似文献
16.
Antioxidative activities of different phenolic compounds (catechin, caffeic acid, ferulic acid and tannic acid) at various levels were determined by different assays. Among all the phenolic compounds tested, tannic acid exhibited the highest 2,2-diphenyl-1-picryl hydrazyl (DPPH) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and ferric reducing antioxidant power (FRAP). Nevertheless, catechin showed the highest metal chelating activity (P < 0.05), whereas caffeic acid had the highest lipoxygenase (LOX) inhibitory activity (P < 0.05). The impact of different phenolic compounds at a level of 100 mg/l on lipid oxidation of menhaden oil-in-water emulsion and mackerel mince was investigated. Tannic acid showed the highest efficacy in retardation of lipid oxidation for both model systems as evidenced by the lower peroxide value (PV), conjugated diene (CD) and thiobarbituric acid-reactive substances (TBARS) values. This was also related with the lower non-heme iron content in tannic acid treated samples. Tannic acid was therefore considered as the most potential natural antioxidant for controlling oxidation of fish oil-in-water emulsion and fish mince, whereas ferulic acid seemed to possess the lowest preventive effect on lipid oxidation. 相似文献
17.
Jin-Long LiYong-Qiang Cheng Pan WangWen-Ting Zhao Li-Jun Yin Masayoshi Saito 《Food Hydrocolloids》2012,26(2):448-455
Extensive research has indicated that the electrostatic attraction between polysaccharides and proteins on the oil-water interface can improve the stability of emulsions. However, this electrostatic effect will be weakened or even eliminated as the solution pH or ionic strength of emulsions change, resulting in the shedding of the polysaccharide layer. We prepared primary oil-in-water emulsions at pH 7.0 using whey protein isolate (WPI) as an emulsifier and then beet pectin was added to form secondary emulsions. After the pH of emulsions was adjusted to 4.0 to promote electrostatic attraction between the beet pectin molecules and the protein-coated droplets, horseradish peroxidase was added to generate a cross-linked beet pectin coating. Results show that stable emulsions coated with WPI and cross-linked beet pectin interfaces could be formed. The sensitivity of the emulsions to the environmental stresses of pH changes, ions addition, thermal processing and freezing was also characterized in this work. Our results support the view that cross-linked beet pectin improves the stability of emulsions and is superior to simple deposition on the surface of lipid droplets. The interfacial engineering technology used in this study could be used to create food emulsions with improved stability to environmental stresses. 相似文献
18.
Formulation of apple juice beverages containing whey protein isolate or whey protein hydrolysate based on sensory and physicochemical analysis
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Mostafa Goudarzi Ashkan Madadlou Mohammad E Mousavi Zahra Emam‐Djomeh 《International Journal of Dairy Technology》2015,68(1):70-78
Whey protein isolate (WPI) or its bioactive hydrolysate (WPH) was mixed with apple juice along with sweetener, obtaining a series of beverages with various pH values. Sedimentation of WPI‐apple juice and WPH‐apple juice beverages was inhibited at pH values of 3.15 and 3.47, respectively. The higher the whey protein content, the more undesirable was the taste of samples. A clearer appearance with smaller particle size was obtained with WPH‐apple juice formulations compared to WPI‐apple juice formulations at pH values closer to the pI of the whey proteins. Intrinsic viscosity measurements revealed the weaker associations of peptides compared with protein molecules. 相似文献
19.
Effect of α-lactalbumin and β-lactoglobulin on the oxidative stability of 10% fish oil-in-water emulsions depends on pH 总被引:1,自引:0,他引:1
The objective of this study was to investigate the influence of pH on lipid oxidation and protein partitioning in 10% fish oil-in-water emulsions prepared with different whey protein isolates with varying ratios of α-lactalbumin and β-lactoglobulin. Results showed that an increase in pH increased lipid oxidation irrespective of the emulsifier used. At pH 4, lipid oxidation was not affected by the type of whey protein emulsifier used or the partitioning of proteins between the interface and the water phase. However, at pH 7 the emulsifier with the highest concentration of β-lactoglobulin protected more effectively against oxidation during emulsion production, whereas the emulsions with the highest concentration of α-lactalbumin were most stable to oxidation during storage. These differences were explained by differences in the pressure and adsorption induced unfolding of the individual protein components. 相似文献
20.