Elise Ringgenberg - Academia.edu (original) (raw)
Uploads
Papers by Elise Ringgenberg
Food Biophysics, Jun 13, 2012
The physico-chemical properties of soymilk particles were investigated as a function of concentra... more The physico-chemical properties of soymilk particles were investigated as a function of concentration of protein in soymilk. Soymilk samples were prepared using different water-to-protein ratios, resulting in 4 %, 5 % and 7 % protein content. The soymilk particles were not significantly different in their protein composition, surface hydrophobicity and intrinsic fluorescence; however, their ζpotential and particle size were affected by protein concentration. Using a relation between the effective refractive index of soymilk and the turbidity parameter determined experimentally using diffusing wave spectroscopy, it was possible to estimate, for the first time, a voluminosity of 4.11 mL/g and a refractive index of 1.388 for the colloidal particles. This allowed conversion of protein content to volume fraction, and comparison of the experimental data collected by diffusing wave spectroscopy, rheology and ultrasonic spectroscopy with theoretical models. Keywords Soy-milk. Physico-chemical characterization. Voluminosity. Diffusing wave spectroscopy. Ultrasound and soy-foods consumption. 1-3 To meet this growing demand, food companies are faced with new challenges to formulate innovative products that provide added health benefits. One of the possible ways to achieve this would be to exploit the use of soymilk as an ingredient base in foods and beverage products; however, a better understanding of the fundamental colloidal characteristics of soymilk is required to succeed. Soymilk particles are colloidal assemblies derived from the aqueous extraction of soybeans and are made up of various components, including lipids (such as triglycerides and phospholipids), proteins, complex carbohydrates, minerals and phytates. 4,5 There are two major proteins in soymilk, namely glycinin and β-conglycinin, constituting about 40 % and 30 % of total soy protein, respectively. Research on the chemical nature of soymilk particles revealed that they are composed of all the major subunits present in the original storage protein in the seed. 5-7 Heat treatment of soymilk is necessary to denature antinutritional components, prolong shelf-life and stability, as well as to improve sensorial characteristics of the final product. 8-10 Several studies report that heat treatment is essential to achieve colloidal stability of soymilk. 8,11 Protein particles are formed during heating through disruption, and subsequent rearrangement and aggregation of the storage proteins present in the seed. 4-6,12-16 Heat treatment was found to decrease the fraction of large particles, defined as particles larger than 100 nm (by differential centrifugation), and increase the fraction of medium-sized particles, defined as particles between 40 nm and 100 nm, which form by association of supernatant proteins with each other. The increase in medium sized particles seemed to be responsible for the colloidal stability of the system. 5,6,14 In agreement, another study reported that soymilk particles after heat-treatment are polydisperse in size with an average particle diameter of around 0.20±0.01 μm. 5
Food Hydrocolloids, 2013
The molecular details of the aggregation of soy protein particles in soymilk during acid-induced ... more The molecular details of the aggregation of soy protein particles in soymilk during acid-induced gelation using glucono-delta-lactone (GDL) were investigated. Soymilk samples were prepared from different water-to-bean ratios and contained approximately 4% and 7% protein. The effects of protein concentration and incubation temperature (30 or 7 C) on soymilk gelation were observed using rheology and diffusing wave spectroscopy at two different GDL concentrations. During acidification, there was a decrease in electrostatic repulsion between particles which well correlated with the pH of aggregation determined by dynamic light scattering. Gelation of soymilk occurred at about pH 5.8, and neither the rate of acidification nor the protein concentration affected the gelation pH. Gel stiffness was affected by protein concentration. A detailed study of the soluble fraction during the preceding stages of aggregation clearly demonstrated that glycinin components were the first to destabilize during acidification, followed by the b-conglycinin subunits. Decreasing the incubation temperature from 30 C to 7 C increased the pH of gelation and the gel modulus (G 0) measured by rheology. It was concluded that short range interactions play a major role in the formation of the protein network in soymilk curd.
Food Hydrocolloids, 2013
The molecular details of the aggregation of soy protein particles in soymilk during acid-induced ... more The molecular details of the aggregation of soy protein particles in soymilk during acid-induced gelation using glucono-delta-lactone (GDL) were investigated. Soymilk samples were prepared from different water-to-bean ratios and contained approximately 4% and 7% protein. The effects of protein concentration and incubation temperature (30 or 7 C) on soymilk gelation were observed using rheology and diffusing wave spectroscopy at two different GDL concentrations. During acidification, there was a decrease in electrostatic repulsion between particles which well correlated with the pH of aggregation determined by dynamic light scattering. Gelation of soymilk occurred at about pH 5.8, and neither the rate of acidification nor the protein concentration affected the gelation pH. Gel stiffness was affected by protein concentration. A detailed study of the soluble fraction during the preceding stages of aggregation clearly demonstrated that glycinin components were the first to destabilize during acidification, followed by the b-conglycinin subunits. Decreasing the incubation temperature from 30 C to 7 C increased the pH of gelation and the gel modulus (G 0) measured by rheology. It was concluded that short range interactions play a major role in the formation of the protein network in soymilk curd.
Food Research International, 2008
The effect of heat treatment at 95-100°C for 5 min and homogenization on the physicochemical prop... more The effect of heat treatment at 95-100°C for 5 min and homogenization on the physicochemical properties of soymilk was studied, determining the particle size distribution and the amount and type of protein present after step-wise centrifugation. Differential scanning calorimetry of soy protein showed three thermal transitions for unheated soymilk at 54, 70 and 94°C, which were attributed to 2S, 7S and 11S, respectively. These thermal transitions were absent from heated (and homogenized) soymilk. Unheated soymilk showed a large average particle size, a broad size distribution, and significant protein precipitation with centrifugation. Heating of soymilk decreased the particle size distribution and improved its stability. Homogenization also resulted in a decrease in particle size, with a narrower size distribution compared to heated soymilk. During step-wise centrifugation changes in the ratios of 11S (glycinin) and 7S (b-conglycinin) in the supernatants were noted, and they depended on the treatments applied to soymilk. Transmission electron microscopy observations showed the distribution of the colloidal particles in soymilk and helped further identify the differences after heating and heating with homogenization.
Food Biophysics, Jun 13, 2012
The physico-chemical properties of soymilk particles were investigated as a function of concentra... more The physico-chemical properties of soymilk particles were investigated as a function of concentration of protein in soymilk. Soymilk samples were prepared using different water-to-protein ratios, resulting in 4 %, 5 % and 7 % protein content. The soymilk particles were not significantly different in their protein composition, surface hydrophobicity and intrinsic fluorescence; however, their ζpotential and particle size were affected by protein concentration. Using a relation between the effective refractive index of soymilk and the turbidity parameter determined experimentally using diffusing wave spectroscopy, it was possible to estimate, for the first time, a voluminosity of 4.11 mL/g and a refractive index of 1.388 for the colloidal particles. This allowed conversion of protein content to volume fraction, and comparison of the experimental data collected by diffusing wave spectroscopy, rheology and ultrasonic spectroscopy with theoretical models. Keywords Soy-milk. Physico-chemical characterization. Voluminosity. Diffusing wave spectroscopy. Ultrasound and soy-foods consumption. 1-3 To meet this growing demand, food companies are faced with new challenges to formulate innovative products that provide added health benefits. One of the possible ways to achieve this would be to exploit the use of soymilk as an ingredient base in foods and beverage products; however, a better understanding of the fundamental colloidal characteristics of soymilk is required to succeed. Soymilk particles are colloidal assemblies derived from the aqueous extraction of soybeans and are made up of various components, including lipids (such as triglycerides and phospholipids), proteins, complex carbohydrates, minerals and phytates. 4,5 There are two major proteins in soymilk, namely glycinin and β-conglycinin, constituting about 40 % and 30 % of total soy protein, respectively. Research on the chemical nature of soymilk particles revealed that they are composed of all the major subunits present in the original storage protein in the seed. 5-7 Heat treatment of soymilk is necessary to denature antinutritional components, prolong shelf-life and stability, as well as to improve sensorial characteristics of the final product. 8-10 Several studies report that heat treatment is essential to achieve colloidal stability of soymilk. 8,11 Protein particles are formed during heating through disruption, and subsequent rearrangement and aggregation of the storage proteins present in the seed. 4-6,12-16 Heat treatment was found to decrease the fraction of large particles, defined as particles larger than 100 nm (by differential centrifugation), and increase the fraction of medium-sized particles, defined as particles between 40 nm and 100 nm, which form by association of supernatant proteins with each other. The increase in medium sized particles seemed to be responsible for the colloidal stability of the system. 5,6,14 In agreement, another study reported that soymilk particles after heat-treatment are polydisperse in size with an average particle diameter of around 0.20±0.01 μm. 5
Food Hydrocolloids, 2013
The molecular details of the aggregation of soy protein particles in soymilk during acid-induced ... more The molecular details of the aggregation of soy protein particles in soymilk during acid-induced gelation using glucono-delta-lactone (GDL) were investigated. Soymilk samples were prepared from different water-to-bean ratios and contained approximately 4% and 7% protein. The effects of protein concentration and incubation temperature (30 or 7 C) on soymilk gelation were observed using rheology and diffusing wave spectroscopy at two different GDL concentrations. During acidification, there was a decrease in electrostatic repulsion between particles which well correlated with the pH of aggregation determined by dynamic light scattering. Gelation of soymilk occurred at about pH 5.8, and neither the rate of acidification nor the protein concentration affected the gelation pH. Gel stiffness was affected by protein concentration. A detailed study of the soluble fraction during the preceding stages of aggregation clearly demonstrated that glycinin components were the first to destabilize during acidification, followed by the b-conglycinin subunits. Decreasing the incubation temperature from 30 C to 7 C increased the pH of gelation and the gel modulus (G 0) measured by rheology. It was concluded that short range interactions play a major role in the formation of the protein network in soymilk curd.
Food Hydrocolloids, 2013
The molecular details of the aggregation of soy protein particles in soymilk during acid-induced ... more The molecular details of the aggregation of soy protein particles in soymilk during acid-induced gelation using glucono-delta-lactone (GDL) were investigated. Soymilk samples were prepared from different water-to-bean ratios and contained approximately 4% and 7% protein. The effects of protein concentration and incubation temperature (30 or 7 C) on soymilk gelation were observed using rheology and diffusing wave spectroscopy at two different GDL concentrations. During acidification, there was a decrease in electrostatic repulsion between particles which well correlated with the pH of aggregation determined by dynamic light scattering. Gelation of soymilk occurred at about pH 5.8, and neither the rate of acidification nor the protein concentration affected the gelation pH. Gel stiffness was affected by protein concentration. A detailed study of the soluble fraction during the preceding stages of aggregation clearly demonstrated that glycinin components were the first to destabilize during acidification, followed by the b-conglycinin subunits. Decreasing the incubation temperature from 30 C to 7 C increased the pH of gelation and the gel modulus (G 0) measured by rheology. It was concluded that short range interactions play a major role in the formation of the protein network in soymilk curd.
Food Research International, 2008
The effect of heat treatment at 95-100°C for 5 min and homogenization on the physicochemical prop... more The effect of heat treatment at 95-100°C for 5 min and homogenization on the physicochemical properties of soymilk was studied, determining the particle size distribution and the amount and type of protein present after step-wise centrifugation. Differential scanning calorimetry of soy protein showed three thermal transitions for unheated soymilk at 54, 70 and 94°C, which were attributed to 2S, 7S and 11S, respectively. These thermal transitions were absent from heated (and homogenized) soymilk. Unheated soymilk showed a large average particle size, a broad size distribution, and significant protein precipitation with centrifugation. Heating of soymilk decreased the particle size distribution and improved its stability. Homogenization also resulted in a decrease in particle size, with a narrower size distribution compared to heated soymilk. During step-wise centrifugation changes in the ratios of 11S (glycinin) and 7S (b-conglycinin) in the supernatants were noted, and they depended on the treatments applied to soymilk. Transmission electron microscopy observations showed the distribution of the colloidal particles in soymilk and helped further identify the differences after heating and heating with homogenization.