Karina D. Martínez

Modification of foaming properties of soy protein isolate by high ultrasound intensity: Particle size effect

The effect of high intensity ultrasound (HIUS) may produce structural modifications on proteins through a friendly environmental process. Thus, it can be possible to obtain aggregates with a determined particle size, and altering a defined functional property at the same time. The objective of this work was to explore the impact of HIUS on the functionality of a denatured soy protein isolate (SPI) on foaming and interfacial properties. SPI solutions at pH 6.9 were treated with HIUS for 20 min, in an ultrasonic processor at room temperature, at 75, 80 and 85°C. The operating conditions were: 20 kHz, 4.27 ± 0.71 W and 20% of amplitude. It was determined the size of the protein particles, before and after the HIUS treatment, by dynamic light scattering. It was also analyzed the interfacial behavior of the different systems as well as their foaming properties, by applying the whipping method. The HIUS treatment and HIUS with temperature improved the foaming capacity by alteration of particle size whereas stability was not modified significantly. The temperature of HIUS treatment (80 and 85°C) showed a synergistic effect on foaming capacity. It was found that the reduction of particle size was related to the increase of foaming capacity of SPI. On the other hand, the invariable elasticity of the interfacial films could explain the stability of foams over time.

New View to Obtain Dryer Food Foams with Different Polysaccharides and Soy Protein by High Ultrasound

The objective of this work was to determine the effects of high intensity ultrasound application on the foaming properties of soy protein-polysaccharides mixed solutions. To this end, foaming parameters during foam formation were analyzed. The samples were sonicated for 20 min using ultrasonic processor Vibra Cell Sonics, and model VCX 750 at a frequency of 20 kHz and an amplitude of 20%. The foams were produced by a Foamscan instrument. The evolution of the bubble size change in the foam was also determined by a second CCD camera. For all foamed systems, at two pHs 3 and 7, Foam expansion and Relative Foam Conductivity showed a great increase after ultrasonic treatment. Other parameters studied did not show difference. On the other hand, Final Time of Foaming and the Total Gas Volume incorporation for foams formation were correlated with the Relative Foam Conductivity decrease and the Foam Expansion increase when HIUS were applied in every system. Comparative bubble size and shape during the foam formation according to the treatments and pH used confirmed the parameters results.

Enhancing the foamability of beverages proteins by ultrasound

The objective was to study the foamability of two proteins after ultrasound application. Soy protein and whey protein isolate were used as starting material at pH used in the food processing. Ultrasound was used to analyze the foamability effect on the solutions relating with the bubble size change. The samples were sonicated at same conditions using an ultrasonic processor. Foam formation was measured by conductimetric and optical methods. Moreover, the evolution of the bubble size change was registered. Whey protein isolate solution was found a good choice to use as foaming agent at beverages preparations improved by ultrasound application. Keywords— foamability, soy protein isolate, ultrasound, whey proteins isolate.

Comparative evaluation of structure protein foamability with ultrasound of high intensity application

The objective was to study the foamability of two proteins after ultrasound application. Soy protein and whey protein isolate were used as starting material. Ultrasound was used to analyze the foamability effect on the solutions relating with the bubble size change. The samples were sonicated at same conditions using an ultrasonic processor. Foam formation was measured by conductimetric and optical methods. Moreover, the evolution of the bubble size change was registered. The effect of ultrasound depended on the protein. Therefore, the use of soy or whey protein isolate will be decided by the functionality required. Introduction Soybean proteins are widely used in many foods as functional and nutritional ingredients [1]. These proteins are used in a wide range of food applications, including processed meat, nutritional beverages, infant formulas, and dairy product replacement. Glycinin and β-conglycinin, the major components of soybean protein, account for approximately 70% of the proteins in soybeans [2]. Most studies were done using native soy protein isolate, glycinin and β-conglycinin, which are of limited value for the understanding of commercially available soy isolates. Whey protein concentrates and isolates are important food ingredients because of their desirable functional properties, such as gelation, foaming and emulsification. Whey proteins are a significant source of functional protein ingredients for many traditional and novel food products [3]. The main proteins in whey are β-lactoglobulin (β -lg), α-lactalbumin (α-lac) and bovine serum albumin (BSA) and they account for 70% of total whey proteins [4]. These proteins are responsible for the functional properties of whey proteins, such as solubility in water, viscosity, gelation, emulsification, foaming, colour, flavor and texture enhancement and offer numerous nutritional advantages to formulated products [5]. The effect of ultrasound is related to cavitation, heating, dynamic agitation, shear stresses, and turbulence [6]. It may cause physical changes producing aggregates through non-covalent bonds by cyclic generation and collapse of cavities depending of structural or aggregation protein state. In the present work, effects of ultrasound of high intensity on the foamability of two different proteins at similar concentration and electrostatic charges were compared, and were studied at pH 7. Bubbling method is the unique system to form the foam that gives the precise liquid and gas used to form them, having thus, the exact density of foams obtained. Soy protein and whey protein isolates were used as starting material. The foaming formation together with the bubble size change was analyzed. Materials and methods Protein samples preparation Soy protein isolate (SPI) was provided by Instituto de la Grasa, Seville, Spain and the complete description was published elsewhere [7]. Soluble SPI (SSPI) at pH 7 was used as starting material for the current work. Protein solution, at 4% w/w, was centrifuged for 1 hour at room temperature at 10,000 g. The protein content was determined in the soluble fraction by the Kjeldhal method (N x 6.25), resulting in 1.73. Whey protein isolate (WPI) was provided by Milkaut, Argentina. The protein was used at 2 % wt/wt and adjusted further to pH7. These final solutions were treated by high intensity ultrasound (HIUS). Foam formation The foams were made using a Foamscan instrument (TeclisIt Concept, Logessaigne, France). The foam is generated by blowing nitrogen gas at a flow of 45 mL/min through a porous glass filter of 0.2 μm at the button of a glass tube where 20 ml of the foaming aqueous solutions (25 ± 1oC) is placed. In all experiments, the foam was allowed to reach a volume of 120 ml. The bubbling was then stopped and the evolution of the foam was analyzed by means of conductimetric and optical measurements. The Final Time of Foaming (FTF), the Total Gas Volume (TGV) and the Final liquid volume (FLV) were taken from the table results after each experiment. The generated foam rises along a thermostated square prism glass column, where the volume is followed by image analysis using a CCD camera. The evolution of the bubble size Correspondence to: Karina Martínez, Department of Industries, Faculty of Exact and Natural Sciences, University of Buenos Aires, Ciudad Universitaria (1428) Buenos Aires, Argentina; Tel: +541145763377; E-mail: karinamartinez@ di.fcen.uba.ar

Role of Polysaccharides in Complex Mixtures with Soy Protein Hydrolysate on Foaming Properties Studied by Response Surface Methodology

The complex mixture studied, a hydrolyzed soy protein (HSP), κ-carrageenan (κC), and an hydroxypropyl methylcellulose (HPMC), could be used as a foaming agent under refrigeration or heating conditions because of the presence of one polysaccharide (HPMC) that gels on heating and another (κC) that gels on cooling. The objective of this work was to study the role of these polysaccharides on foaming properties by whipping methods at heating conditions. For this purpose, response surface methodology was used to optimize the mixed product in foamed food systems. The obtained results showed that the combination of E4M, κC, and HSP is an adequate strategy to generate good foam capacity and stability at heating conditions. The huge stability increase of foams at heating conditions was ascribed to combined effect of polysaccharides: gelling property of E4M and the viscozieng character imparted by κC to continuous phase of foaming.