Foaming Properties of Lipid-Reduced and Calcium-Reduced Whey Protein Concentrates

The ability of whey protein concentrates (WPC) to form highly expanded and stable foams is critical for food applications such as whipped toppings and meringue-type products. The foaming properties were studied on six experimental and three commercial WPC, manufactured by membrane fractionation processes to contain reduced lipids and calcium. Lipid-reduced WPC had excellent foaming properties. Experimental delipidized WPC MF 0.45 and commercial delipidized WPC E had higher (P < 0.05) foam expansion than egg white protein (EWP). However. WPC B made bv low-pH UF and isoelectric orecinitation did not form a foam. Lipids and ash were the main factors affecting foaming properties.     

Comparison of milk‐derived whey protein concentrates containing various levels of casein

Milk permeate was obtained from microfiltration (MF) and concentrated to produce milk‐derived whey protein concentrate (MWPC); MF at low temperatures yielded permeate with caseins (MWPC‐HC), and at higher MF temperatures, low concentrations of caseins were present (MWPC‐LC). MWPC samples were compared to whey protein concentrates (WPCs). Solutions of MWPC were less turbid and produced larger foam overruns and more stable foams than WPC. MWPC‐HC solutions produced the most stable foams. MWPC contained fewer types and lower relative quantities of volatile compounds than WPC before and after storage. Compared with WPC, MWPC have superior sensory, foaming and storage properties.     

Foaming and drying behaviour of ripe bananas

The foaming of ripe bananas and the forced air-drying characteristics of the resulting banana foam mats were studied. Fresh banana puree with a density of 0.93 g/ml was foamed to a density of 0.50 g/ml after 12 min of whipping by the addition of 10 g/100 g soy protein as a foam inducer. Glyceryl monostearate did not induce foaming while commercially available food ingredients, Dream Whip and Gelatine induced foaming but such foams were not suitable for subsequent drying. Banana foam mats were dried at temperatures from 45°C to 90°C in a forced air, cabinet dryer, to a hard, porous and brittle solid which was amenable to grinding so as to produce a dehydrated banana powder. The transient drying behaviour of such mats was described by a capillary model of the form ln(M/M₀)=−Kt and over the bulk of the moisture ratio range, 0.05?M/M₀?1.0. The drying time (t) was directly related to the thickness of the foam mats. K values increased from 0.248 to 0.809 h⁻¹ as the drying air temperature was raised from 45°C to 90°C. Increasing the air velocity from 0.62 to 1.03 m/s did not profoundly influence the drying rate.     

Determination of effective moisture diffusivity and assessment of quality attributes of banana slices during drying

The influence of drying temperatures on the moisture diffusivity and quality attributes of the dried banana slices in terms of volatile compound, shrinkage, color, texture and microstructure were studied. Bananas with peel color index of 5 corresponding to yellow color with green tip were sliced into 3 mm thickness, dipped into ascorbic acid solution and dried at four temperatures of 70, 80, 90 and 100 °C. Drying rate of banana slices can be divided into two sub-drying periods, first and second falling rate periods. The effective diffusivity estimated by the optimization technique was found to decrease sharply with moisture content in the first falling rate period and changed slightly in the second falling rate period. High-temperature drying seems to provide lower loss of volatile compounds in the dried sample. Moreover, the dried banana was very porous, resulting in remarkably lower hardness value than that obtained from the low-temperature drying whilst the crispiness was not significantly different amongst the samples obtained at various drying temperatures. Although the textural property could be improved at high temperature, the product color was brown as manifested by the low L- and hue values in particular at the drying temperature of 100 °C.     

Foam-Mat Drying of Plantain and Cooking Banana (<Emphasis Type="Italic">Musa</Emphasis> spp.)

Foaming, reconstitution, and sensory attributes of foam-mat-dried plantain and cooking banana were investigated. Plantain and cooking banana pastes mixed with different concentrations (0.005%, 0.01%, 0.015%, and 0.02%) of glyceryl monostearate (GMS) were whipped, and the resulting foams were air dried at 60°C, 70°C, and 80°C. Physical, chemical, and sensory properties of fresh and reconstituted paste from plantain and cooking bananas were determined. Higher GMS concentration and longer whipping time resulted in lower foam densities. Generally, cooking banana foams showed lower foam density compared to plantain foam. Lower drying temperatures and concentration of GMS resulted in longer drying time. pH (4.41–4.80), titratable acidity (0.06–0.08), and water absorption capacity (56.75–64.02%) of the reconstituted pastes varied with commodity, drying temperature, and %GMS concentration. Fresh and reconstituted pastes showed comparable physical and chemical attributes, while the taste and sensory attributes of fresh plantain and cooking banana pastes were significantly (p < 0.05) better than those of reconstituted pastes.     

Foam-mat drying of cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis>) using glyceryl monostearate and egg albumin as foaming agents

Foam-mat drying of cowpea using glyceryl monostearate (GMS) and egg albumin (EG) as foaming agents was investigated. GMS and EG were incorporated into cowpea paste (22%, 25% and 28% total solids) at 2.5, 5.0, 7.5, 10.0, 12.5 and 15% (w/w), and whipped for 3, 6, 9, 12, 15, 18 and 21 min, maintaining 15, 25 and 35 °C foaming temperatures. Foam density was measured and expressed in g/cm³. Cowpea foams were dried at 60 °C (Twb, wet bulb temperature 35 °C) for 48 min. Sensory attributes of akara produced from fresh and reconstituted pastes were evaluated.Generally, foam density decreased with increased concentrations of GMS and EG in cowpea paste. Foam density decreased with decrease in total solids of cowpea paste. Minimum foam densities were obtained in cowpea foams with GMS and EG after 9 and 21 min of whipping, respectively. EG-stabilized foams were unstable for drying. Sensory evaluation showed no significant difference (P>0.05, 0.01) in the quality attributes of akara produced from fresh and reconstituted GMS-stabilized cowpea powders.     

Characterization of Apple Juice Foams for Foam-mat Drying Prepared with Egg White Protein and Methylcellulose

ABSTRACT: Intrinsic stability and rheological properties of apple juice foams for foam mat drying were studied. Foams were prepared from clarified apple juice by adding various concentrations of 2 foaming agents of different nature: a protein (egg white at 0.5%, 1%, 2%, and 3% w/w) and a polysaccharide (methylcellulose at 0.1%, 0.2%, 0.5%, 1%, and 2% w/w), and whipping at different times (3, 5, and 7 min). In general, egg white foams were less stable but showed a higher degree of solidity (stronger structures), higher foaming capacity, and smaller bubble average diameter than methylcellulose foams. Foam stability increased with increasing concentrations of either methylcellulose or egg white. Increasing whipping times increased the stability of egg white foams only. Stability parameters (maximum drainage and drainage half-time) were correlated in terms of rheological parameters of the continuous phase (consistency index and apparent viscosity at 30/s, respectively). The correlations ( R ²= 0.766 and 0.951, respectively) were considered acceptable because they were independent of whipping time and foaming agent nature and concentration. Results on foam rheology obtained by dynamic and vane tests were in agreement, but the latter method was more sensitive. Optimal concentrations to obtain the most solid foams (0.2% methylcellulose and 2% to 3% egg white, respectively) were the same concentrations required for maximum foaming capacity. Based on this observation and previous models, an empirical expression was proposed to predict the degree of solidity (in terms of inverse phase angle and yield stress) only as a function of foam structural properties (air volume fraction and average bubble size). The model proved to be satisfactory to fit experimental results ( R ²= 0.848 and 0.975, respectively), independently of whipping time, foaming agent nature and concentration.     

Physico-chemical factors controlling the foamability and foam stability of milk proteins: Sodium caseinate and whey protein concentrates

We explored the foaming behavior of the two main types of milk proteins: flexible caseins and globular whey proteins. Direct foam comparison was complemented with measurements in model experiments such as thin foam films, dynamic surface tension, and protein adsorption. Foaming was studied as a function of pH (from below to above isoelectric point, pI) and range of ionic strengths. Maximum foamability was observed near pI ≈ 4.2 for WPC in contrast to sodium caseinate which had minimum foaming near pI = 4.6. Good foamability behavior correlated well with an increased adsorption, faster dynamic surface tension decrease and increased film lifetime. Differences in the stability of the foams and foam were explained with the different molecular structure and different aggregation behavior of the two protein types. Far from its isoelectric pI, casein adsorption layers are denser and thicker thus ensuring better stabilization. Added electrolyte increased further the adsorption and the repulsion between the surfaces (probably by steric and/or osmotic mechanism). In contrast the globular molecules of WPC probably could not compact well to ensure the necessary films and foams stabilization far from pI, even after electrolyte addition.     

桃仁清蛋白与大豆分离蛋白功能特性比较研究

为提高桃仁清蛋白(PKA)在食品工业中的应用,将其与大豆分离蛋白(SPI)对照,研究了PKA的溶解性、持水性、持油性、起泡性及泡沫稳定性、乳化性及乳化稳定性和凝胶性等功能特性.结果表明:与SPI相比,PKA具有很好的溶解性、泡沫稳定性、乳化稳定性及较低的凝胶质量浓度,持油性略高于SPI,但起泡性、乳化性及持水性较差;PKA溶解性受溶解条件影响较小.PKA具有良好的功能性质,适合作为食品添加剂或配料.     

Improvement of Foaming Property of Egg White Protein by Phosphorylation through Dry-Heating in the Presence of Pyrophosphate

ABSTRACT:  Egg white protein (EWP) was phosphorylated by dry-heating in the presence of pyrophosphate at pH 4 and 85 °C for 1 d, and the foaming properties of phosphorylated EWP (PP-EWP) were investigated. The phosphorus content of EWP increased to 0.71% as a result of phosphorylation. To estimate the foaming properties of EWP, the foams were prepared by 2 methods: bubbling of the 0.1% (w/v) protein solution and whipping of the 10% (w/w) protein solution with an electric mixer. The foaming power, which was defined as an initial conductivity of foam from 0.1% (w/v) protein solution, was a little higher in PP-EWP than in native EWP (N-EWP), and the foaming stability of PP-EWP was much higher than that of dry-heated EWP (DH-EWP) and N-EWP. The microscopic observation of foams from the 10% (w/w) solution showed that the foams of PP-EWP were finer and more uniform than those of N- and DH-EWP. Although there were no significant differences in the specific gravity and overrun of the foams between PP- and DH-EWP ( P  < 0.05), the specific gravity and overrun of the foams from PP-EWP were smaller and higher, respectively, than that of the foams from N-EWP. The drainage volume was smaller in the foams from PP-EWP than in those from N- and DH-EWP. These results demonstrated that phosphorylation of EWP by dry-heating in the presence of pyrophosphate improved the foaming properties, and that it was more effective for the foam stability than for the foam formation.     

The composition of interfacial material from skim milk foams

The foaming properties of skim milk vary with temperature of foaming in the range from 5 to 85°C, with foams of maximum stability being formed at approximately 45°C. This paper reports the significance of different milk fractions in the foam and concludes that the micellar casein fraction plays an important role in stabilization of milk foam formed at higher temperatures. This finding was supported by the fact that added calcium chloride increased and calcium-chelating agents decreased foam stability. These effects were attributed to the increase and decrease, respectively, in the amount of micellar casein in the milk. Furthermore, bubble ghost material sedimented by low-speed centrifugation of foam was found to contain predominantly caseins, and electron micrographs of foams formed at 45°C clearly showed casein micelles spread over the interface. However, other structures observed in the electron micrographs suggest that soluble milk proteins and possibly polar lipids are also present in the foams and play a role in formation of milk foams.     

紫苏分离蛋白功能性研究

为了开发紫苏蛋白在食品工业中的应用,以大豆分离蛋白为对照,研究紫苏分离蛋白的功能特性。结果表明：紫苏分离蛋白的溶解性与大豆分离蛋白的溶解性随pH值变化的趋势基本一致,但在等电点时紫苏分离蛋白的溶解性高于大豆分离蛋白。在pH7.0时,紫苏分离蛋白的持水性、起泡性及泡沫稳定性、乳化性和凝胶性均不及大豆分离蛋白。但紫苏分离蛋白的吸油性仅稍小于大豆分离蛋白,此外,在紫苏分离蛋白的蛋白质质量浓度为3g/100mL以后,其乳化稳定性与大豆分离蛋白的乳化稳定性基本相当。紫苏分离蛋白在食品加工中作为一种蛋白质强化剂具有一定潜力。     

Stabilization of emulsions and foams using barley β-glucan

Barley β-glucan (BBG) is receiving increasing attention as a food hydrocolloid. Stability of foams and emulsions was assessed using whey protein concentrate (WPC) as an emulsifier and foaming agent, and BBG gum extracted at pilot plant or laboratory scale as a stabilizer. WPC had a significant lowering effect (P⩽0.05) on surface tension of water and water–oil interfacial tension, while the effect of β-glucan was time dependent. Differential scanning calorimetry (DSC) showed that BBG formed a gelled network, responsible for stabilizing, that melts at 58–62°C. Reversible gels of BBG melt around 63°C. Emulsion (50% o/w) droplet size decreased several fold when prepared with BBG gum and phase separation was substantially decreased. Foam volume and 50% drainage were significantly (P⩽0.05) improved upon addition of β-glucan. Sugar significantly enhanced foam stability only when used together with β-glucan. BBG shows potential as a stabilizer in foam- and emulsion-type food products.     

巯基乙醇对大豆分离蛋白热致聚合物界面性质的影响

为探讨β-巯基乙醇对大豆分离蛋白热致聚合物界面性质的影响,以大豆分离蛋白为原料,在pH7.0、90 ℃加热添加和不添加β-巯基乙醇（2 mmol/L）浓度为10 mg/mL的大豆分离蛋白溶液0 h和10 h,制备不同大豆分离蛋白质热致聚合物。观察了大豆分离蛋白、添加β-巯基乙醇大豆分离蛋白、大豆分离蛋白热致聚合物和β-巯基乙醇大豆分离蛋白热致聚合物的微观形态、游离巯基含量的变化,同时比较了起泡能力、泡沫稳定性、乳化活性、乳化稳定性、表面疏水性和浊度的差异。结果表明,大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白呈现无规则状态,大豆分离蛋白热致聚合物为有规则的球状颗粒,而β-巯基乙醇大豆分离蛋白热致聚合物部分形成球状聚合物部分形成无规则聚合物。添加β-巯基乙醇改善了大豆分离蛋白的界面性质。与大豆分离蛋白相比较,添加β-巯基乙醇大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白热致聚合物的起泡能力分别提高了64.56%和95.77%,乳化活性提高的幅度分别为12.94%和14.61%。添加β-巯基乙醇大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白热致聚合物在长时间储藏中表现出良好的乳化稳定性和泡沫稳定性。这种良好的界面性质源于β-巯基乙醇的加入赋予聚合物具有更高的游离巯基含量和表面疏水性。并且本实验建立了4种样品的泡沫稳定性和乳化稳定性随时间变化的Rational函数和Linear函数经验模型,为大豆分离蛋白质的实际应用奠定了理论基础。     

Physicochemical and sensory properties of purple Brazilian cherry (Eugenia uniflora,L.) foams

The objective of this work was to characterise the foams of purple Brazilian cherry (Eugenia uniflora L.) pulp made with different additives, aiming at foam‐mat drying. Characterisation was made through analyses of moisture, pH, acidity, soluble solids, density, water activity, colour, total and reducing sugars, protein and ashes. Drying was done at 55 °C for 2 h. Dried Brazilian cherry juice powder was rehydrated for acceptance test. It is concluded that the physicochemical characterisation of fresh Brazilian cherry pulp was satisfactory and was in accordance with the Brazilian standards for agro‐industrial products. Albumin was the best foaming agent that produced a good‐quality powder in a short period. The foam‐mat drying of Brazilian cherry pulp using albumin and Superliga^® (Duas Rodas Industrial ltda, Santa Catarina, Brazil) as foaming agents produced a powder with good physicochemical properties and sensory quality and most preferred juice.     

The relationship between polypeptides and foaming during fermentation

The foam level during fermentations of hopped and unhopped wort and with fresh yeast and successive generations of yeast was examined. Simultaneously the total and hydrophobic polypeptide contents in worts, fermented worts and their concomitant foams were checked. It was shown that the total and hydrophobic polypeptide contents of the foam fraction and the foam level during fermentation were dependent on the generation number of yeast. The early generations of yeast (generations 1 and 2) promoted the formation of the largest amount of foam. It was also observed that a higher volume of foam occurred during fermentation of hopped wort in respect to unhopped one despite a higher concentration of polypeptides in unhopped wort. It could be a consequence of a higher foaming potential of polypeptides in hopped wort. The findings of the work may result in the limitation of foaming in the fermenters and consequently the increase of the brewery productivity without using additives and compromising the quality of the final product.     

High hydrostatic pressure modification of whey protein concentrate for improved functional properties

Whey protein concentrate (WPC) has many applications in the food industry. Previous research demonstrated that treatment of whey proteins with high hydrostatic pressure (HHP) can enhance solubility and foaming properties of whey proteins. The objective of this study was to use HHP to improve functional properties of fresh WPC, compared with functional properties of reconstituted commercial whey protein concentrate 35 (WPC 35) powder. Fluid whey was ultrafiltered to concentrate proteins and reconstituted to equivalent total solids (8.23%) as reconstituted commercial WPC 35 powder. Solutions of WPC were treated with 300 and 400 MPa (0- and 15-min holding time) and 600 MPa (0-min holding time) pressure. After HHP, the solubility of the WPC was determined at both pH 4.6 and 7.0 using UDY and BioRad protein assay methods. Overrun and foam stability were determined after protein dispersions were whipped for 15 min. The protein solubility was greater at pH 7.0 than at pH 4.6, but there were no significant differences at different HHP treatment conditions. The maintenance of protein solubility after HHP indicates that HHP-treated WPC might be appropriate for applications to food systems. Untreated WPC exhibited the smallest overrun percentage, whereas the largest percentage for overrun and foam stability was obtained for WPC treated at 300 MPa for 15 min. Additionally, HHP-WPC treated at 300 MPa for 15 min acquired larger overrun than commercial WPC 35. The HHP treatment of 300 MPa for 0 min did not improve foam stability of WPC. However, WPC treated at 300 or 400 MPa for 15 min and 600 MPa for 0 min exhibited significantly greater foam stability than commercial WPC 35. The HHP treatment was beneficial to enhance overrun and foam stability of WPC, showing promise for ice cream and whipping cream applications.     

Food Protein Functionality in a Liquid System: A Comparison of Deamidated Wheat Protein with Dairy and Soy Proteins

ABSTRACT: Solubility, surface properties, overrun, foam stability, apparent viscosity, and emulsification properties were evaluated for 3% protein dispersions of deamidated wheat protein (DWP), sodium caseinate (SC), soy protein isolate (SPI), and whey protein isolate (WPI). DWP dispersion had the highest apparent viscosity, 25% higher emulsion activity index (EAI), and 82% higher emulsion stability index (ESI) when compared to SPI dispersions. Dispersions of DWP had similar foaming properties and surface properties when compared to SC, but had 50% higher EAI and 1000% greater ESI when compared to the 2 dairy proteins. The utilization of DWP could be expanded into liquid food systems currently using dairy proteins.     

Moisture diffusion by the fractional-time model in convective drying with ultrasound-ethanol pretreatment of banana slices

Innovative drying pretreatments play an essential role in preserving food and reducing drying energy consumption. The aim of this study was, therefore, to investigate the effect of drying pretreatments with ethanol (EH) and ultrasound (UA) on the drying kinetics and moisture diffusion through an anomalous solution by the fractional time, as well as to evaluate the physical, bioactive compounds and antioxidant properties of banana slices. The results indicated that Page's model analyzed the anomalous calculus approach for emerging drying techniques with the appropriate goodness of fit. The anomalous diffusivity approach described the experimental data well and provided new insights into the structure of food material. The new approach also showed that drying pretreatments promote convective drying, reduce drying time by up to 31% and save energy by 19%. Analytical results showed that banana slices pretreated with EH + UA had higher conservation of phenolic compounds and antioxidant activity, as well as an attractive color and high shrinkage. The findings could provide help in the large-scale processing of good-quality dried banana slices.