Gerard Hofland | Delft University of Technology (original) (raw)

Papers by Gerard Hofland

Research paper thumbnail of Isoelectric precipitation of soybean protein using carbon dioxide as a volatile acid

Journal of Chromatography B: Biomedical Sciences and Applications, 2000

Research paper thumbnail of Stable sugar-based protein formulations by supercritical fluid drying

International Journal of Pharmaceutics, 2008

Research paper thumbnail of Synthesis and isolation of added‐value milk fat derivatives using lipase‐catalyzed reactions and supercritical carbon dioxide

Research paper thumbnail of Stabilization of Proteins in Dry Powder Formulations Using Supercritical Fluid Technology

Pharmaceutical Research, 2004

Research paper thumbnail of Production of microparticles from milk fat products using the Supercritical Melt Micronization (ScMM) process

The Journal of Supercritical Fluids, 2011

Research paper thumbnail of Ways of manipulating the polymorphism of glycine during supercritical fluid crystallisation

The Journal of Supercritical Fluids, 2008

Research paper thumbnail of Effect of the modifier on the particle formation and crystallisation behaviour during precipitation from aqueous solutions

The Journal of Supercritical Fluids, 2008

Research paper thumbnail of Solubility of Glycine Polymorphs and Recrystallization of β-Glycine

Journal of Chemical & Engineering Data, 2007

ABSTRACT The solubilities of α-, β-, and γ-glycine in aqueous solutions containing methanol, etha... more ABSTRACT The solubilities of α-, β-, and γ-glycine in aqueous solutions containing methanol, ethanol, 2-propanol, or acetone were measured at 310 K. The solubility of all the polymorphs dropped rapidly as a function of the concentration of antisolvent. The solubility of the glycine polymorphs in water−antisolvent mixtures was, in decreasing order: methanol > ethanol > 2-propanol > acetone. The solubility of α-glycine was slightly higher than that of γ-glycine, but the solubility of β-glycine was significantly higher by up to 17 %. The induction time for the recrystallization of β- to α-glycine in those water−antisolvent mixtures was, in decreasing order: methanol > ethanol > acetone > 2-propanol. This signifies that the selection of an antisolvent for preparation of β-glycine can have an important effect on the product.

Research paper thumbnail of Properties of Sugar, Polyol, and Polysaccharide Water−Ethanol Solutions

Journal of Chemical & Engineering Data, 2007

Research paper thumbnail of Lipase-Catalyzed Ethanolysis of Milk Fat with a Focus on Short-Chain Fatty Acid Selectivity

Journal of Agricultural and Food Chemistry, 2009

Mixtures of fatty acid ethyl esters were produced by lipase-catalyzed ethanolysis of milk fat tri... more Mixtures of fatty acid ethyl esters were produced by lipase-catalyzed ethanolysis of milk fat triglycerides. Three commercial immobilized lipases (Lipozyme TL, Lipozyme RM, and Novozym 435) were tested in different reaction conditions with the aim of maximizing the conversion of the short-chain fatty acid fraction of milk fat to flavor ethyl esters. The influence of the reactants molar ratio was investigated, as well as three different reaction media, that is, hexane, CO(2)-expanded liquid (GXL), and the solvent-free mixture. Novozym 435 showed the highest activity in all conditions. This lipase also exhibited selectivity for short-chain fatty acids, which, at short reaction times, resulted in a product mixture richer in short-chain fatty acids than the original milk fat. The highest selectivities were obtained in hexane and in CO(2)-expanded liquid fat, at low ethanol to fat ratios. Using dense CO(2) as the reaction cosolvent is attractive because it results in the largest short-chain fatty acid enrichment in the product mixture, while leaving no residues in the product.

Research paper thumbnail of Isoelectric Precipitation of Casein Using High-Pressure CO 2

Industrial & Engineering Chemistry Research, 1999

ABSTRACT High-pressure CO2 was used as a recyclable acid for the isoelectric precipitation of cas... more ABSTRACT High-pressure CO2 was used as a recyclable acid for the isoelectric precipitation of casein. Measurement of the pH during the high-pressure process allowed the comparison of the process with conventional precipitation using sulfuric acid. A simple model was made up to calculate the pH in complex aqueous solutions pressurized with CO2. It was established that the isoelectric point (pH 4.6) could not be reached with CO2, unless the milk was diluted. Nevertheless, high precipitation yields could be obtained with this process. Still, it was found that the precipitation is mainly caused by the decrease in pH. The removal of calcium phosphate appeared to be complicated, probably because of precipitation of calcium phosphate in the casein-free solutions after the pressure is released.

Research paper thumbnail of Stabilization of IgG by supercritical fluid drying: Optimization of formulation and process parameters

European Journal of Pharmaceutics and Biopharmaceutics, 2008

Research paper thumbnail of Distinct effects of sucrose and trehalose on protein stability during supercritical fluid drying and freeze-drying

European Journal of Pharmaceutical Sciences, 2006

Research paper thumbnail of A process for the production of a diacylglycerol-based milk fat analogue

European Journal of Lipid Science and Technology, 2011

ABSTRACT We propose a novel process for the production of a DAG-rich acylglycerol mixture derived... more ABSTRACT We propose a novel process for the production of a DAG-rich acylglycerol mixture derived from milk fat. This product has potentially interesting nutritional properties, derived from both its high content of DAG and of short-chain fatty acids (FAs). The proposed process consists of three steps: lipase-catalysed partial ethanolysis of milk fat, extraction of the by-product fatty acid ethyl esters (FAEEs) using supercritical carbon dioxide (SC-CO2) and isomerization of DAG to increase the proportion of 1,3-DAG. The experimental investigation of the process steps was done using milk fat and trilaurin. Several lipases were tested for maximizing the percentage of DAG in the acylglycerol mixture produced by ethanolysis. The selectivity of the chosen lipase was such that the produced AG mixture was enriched in short-chain FAs in relation to the original milk fat. FAEEs were completely extracted from the ethanolysis mixture by SC-CO2. In the final process step, we explored the reaction conditions for facilitating acyl migration in the DAG mixture, so that the equilibrium proportion of 1,3-DAG (∼64%) was attained. Our results set the basis for the development of a simple process for the production of a DAG-rich milk fat analogue.

Research paper thumbnail of The potential of milk fat for the synthesis of valuable derivatives

European Food Research and Technology, 2011

Research paper thumbnail of Selective Production of Polymorphs and Pseudomorphs Using Supercritical Fluid Crystallization from Aqueous Solutions

Crystal Growth & Design, 2007

The precipitation of amino acids and mannitol from aqueous solution was studied in a spraying pro... more The precipitation of amino acids and mannitol from aqueous solution was studied in a spraying process using a mixture of supercritical CO2 and ethanol as drying medium and as anti-solvent. By changing the flow rates, the process was tuned to selectively precipitate α- ...

Research paper thumbnail of Carbon Dioxide Induced Soybean Protein Precipitation: Protein Fractionation, Particle Aggregation, and Continuous Operation

Biotechnology Progress, 2001

Research paper thumbnail of Fractionation of soybean proteins with pressurized carbon dioxide as a volatile electrolyte

Biotechnology and Bioengineering, 2001

Fractionation of specific proteins from plant material is a complex and involved science, yet pur... more Fractionation of specific proteins from plant material is a complex and involved science, yet pure protein extracts are in high demand by a wide range of food and pharmaceutical industries. In this study carbon dioxide has been used as a volatile electrolyte to isoelectrically precipitate two major protein constituents of soybean. Carbon dioxide was shown to be effective in purifying glycinin and beta-conglycinin in a three-step process as 95% and 80% concentrated fractions with precipitation yields of 28% and 21%, respectively. Recycling of the mixed precipitate of the intermediary step enables complete separation into the concentrated fractions. Fractionation acidity was precisely controlled by a simple modification of pressure. In addition, the occurrence of a pH overshoot was prevented at any point in the fractionation vessel, as the pH minimum was defined by its equilibrium relationship with carbon dioxide operating pressure. The removal of the glycinin precipitate was an important factor in the purification procedure. The yield of the individual concentrated glycinin and beta-conglycinin precipitate fractions was a function of carbon dioxide pressure, extract concentration and, to a much lesser extent, temperature.

Research paper thumbnail of Mathematical modeling of the mass transfer from aqueous solutions in a supercritical fluid during particle formation

Research paper thumbnail of Supercritical drying of lysozyme from aqueous solution

Research paper thumbnail of Isoelectric precipitation of soybean protein using carbon dioxide as a volatile acid

Journal of Chromatography B: Biomedical Sciences and Applications, 2000

Research paper thumbnail of Stable sugar-based protein formulations by supercritical fluid drying

International Journal of Pharmaceutics, 2008

Research paper thumbnail of Synthesis and isolation of added‐value milk fat derivatives using lipase‐catalyzed reactions and supercritical carbon dioxide

Research paper thumbnail of Stabilization of Proteins in Dry Powder Formulations Using Supercritical Fluid Technology

Pharmaceutical Research, 2004

Research paper thumbnail of Production of microparticles from milk fat products using the Supercritical Melt Micronization (ScMM) process

The Journal of Supercritical Fluids, 2011

Research paper thumbnail of Ways of manipulating the polymorphism of glycine during supercritical fluid crystallisation

The Journal of Supercritical Fluids, 2008

Research paper thumbnail of Effect of the modifier on the particle formation and crystallisation behaviour during precipitation from aqueous solutions

The Journal of Supercritical Fluids, 2008

Research paper thumbnail of Solubility of Glycine Polymorphs and Recrystallization of β-Glycine

Journal of Chemical & Engineering Data, 2007

ABSTRACT The solubilities of α-, β-, and γ-glycine in aqueous solutions containing methanol, etha... more ABSTRACT The solubilities of α-, β-, and γ-glycine in aqueous solutions containing methanol, ethanol, 2-propanol, or acetone were measured at 310 K. The solubility of all the polymorphs dropped rapidly as a function of the concentration of antisolvent. The solubility of the glycine polymorphs in water−antisolvent mixtures was, in decreasing order: methanol > ethanol > 2-propanol > acetone. The solubility of α-glycine was slightly higher than that of γ-glycine, but the solubility of β-glycine was significantly higher by up to 17 %. The induction time for the recrystallization of β- to α-glycine in those water−antisolvent mixtures was, in decreasing order: methanol > ethanol > acetone > 2-propanol. This signifies that the selection of an antisolvent for preparation of β-glycine can have an important effect on the product.

Research paper thumbnail of Properties of Sugar, Polyol, and Polysaccharide Water−Ethanol Solutions

Journal of Chemical & Engineering Data, 2007

Research paper thumbnail of Lipase-Catalyzed Ethanolysis of Milk Fat with a Focus on Short-Chain Fatty Acid Selectivity

Journal of Agricultural and Food Chemistry, 2009

Mixtures of fatty acid ethyl esters were produced by lipase-catalyzed ethanolysis of milk fat tri... more Mixtures of fatty acid ethyl esters were produced by lipase-catalyzed ethanolysis of milk fat triglycerides. Three commercial immobilized lipases (Lipozyme TL, Lipozyme RM, and Novozym 435) were tested in different reaction conditions with the aim of maximizing the conversion of the short-chain fatty acid fraction of milk fat to flavor ethyl esters. The influence of the reactants molar ratio was investigated, as well as three different reaction media, that is, hexane, CO(2)-expanded liquid (GXL), and the solvent-free mixture. Novozym 435 showed the highest activity in all conditions. This lipase also exhibited selectivity for short-chain fatty acids, which, at short reaction times, resulted in a product mixture richer in short-chain fatty acids than the original milk fat. The highest selectivities were obtained in hexane and in CO(2)-expanded liquid fat, at low ethanol to fat ratios. Using dense CO(2) as the reaction cosolvent is attractive because it results in the largest short-chain fatty acid enrichment in the product mixture, while leaving no residues in the product.

Research paper thumbnail of Isoelectric Precipitation of Casein Using High-Pressure CO 2

Industrial & Engineering Chemistry Research, 1999

ABSTRACT High-pressure CO2 was used as a recyclable acid for the isoelectric precipitation of cas... more ABSTRACT High-pressure CO2 was used as a recyclable acid for the isoelectric precipitation of casein. Measurement of the pH during the high-pressure process allowed the comparison of the process with conventional precipitation using sulfuric acid. A simple model was made up to calculate the pH in complex aqueous solutions pressurized with CO2. It was established that the isoelectric point (pH 4.6) could not be reached with CO2, unless the milk was diluted. Nevertheless, high precipitation yields could be obtained with this process. Still, it was found that the precipitation is mainly caused by the decrease in pH. The removal of calcium phosphate appeared to be complicated, probably because of precipitation of calcium phosphate in the casein-free solutions after the pressure is released.

Research paper thumbnail of Stabilization of IgG by supercritical fluid drying: Optimization of formulation and process parameters

European Journal of Pharmaceutics and Biopharmaceutics, 2008

Research paper thumbnail of Distinct effects of sucrose and trehalose on protein stability during supercritical fluid drying and freeze-drying

European Journal of Pharmaceutical Sciences, 2006

Research paper thumbnail of A process for the production of a diacylglycerol-based milk fat analogue

European Journal of Lipid Science and Technology, 2011

ABSTRACT We propose a novel process for the production of a DAG-rich acylglycerol mixture derived... more ABSTRACT We propose a novel process for the production of a DAG-rich acylglycerol mixture derived from milk fat. This product has potentially interesting nutritional properties, derived from both its high content of DAG and of short-chain fatty acids (FAs). The proposed process consists of three steps: lipase-catalysed partial ethanolysis of milk fat, extraction of the by-product fatty acid ethyl esters (FAEEs) using supercritical carbon dioxide (SC-CO2) and isomerization of DAG to increase the proportion of 1,3-DAG. The experimental investigation of the process steps was done using milk fat and trilaurin. Several lipases were tested for maximizing the percentage of DAG in the acylglycerol mixture produced by ethanolysis. The selectivity of the chosen lipase was such that the produced AG mixture was enriched in short-chain FAs in relation to the original milk fat. FAEEs were completely extracted from the ethanolysis mixture by SC-CO2. In the final process step, we explored the reaction conditions for facilitating acyl migration in the DAG mixture, so that the equilibrium proportion of 1,3-DAG (∼64%) was attained. Our results set the basis for the development of a simple process for the production of a DAG-rich milk fat analogue.

Research paper thumbnail of The potential of milk fat for the synthesis of valuable derivatives

European Food Research and Technology, 2011

Research paper thumbnail of Selective Production of Polymorphs and Pseudomorphs Using Supercritical Fluid Crystallization from Aqueous Solutions

Crystal Growth & Design, 2007

The precipitation of amino acids and mannitol from aqueous solution was studied in a spraying pro... more The precipitation of amino acids and mannitol from aqueous solution was studied in a spraying process using a mixture of supercritical CO2 and ethanol as drying medium and as anti-solvent. By changing the flow rates, the process was tuned to selectively precipitate α- ...

Research paper thumbnail of Carbon Dioxide Induced Soybean Protein Precipitation: Protein Fractionation, Particle Aggregation, and Continuous Operation

Biotechnology Progress, 2001

Research paper thumbnail of Fractionation of soybean proteins with pressurized carbon dioxide as a volatile electrolyte

Biotechnology and Bioengineering, 2001

Fractionation of specific proteins from plant material is a complex and involved science, yet pur... more Fractionation of specific proteins from plant material is a complex and involved science, yet pure protein extracts are in high demand by a wide range of food and pharmaceutical industries. In this study carbon dioxide has been used as a volatile electrolyte to isoelectrically precipitate two major protein constituents of soybean. Carbon dioxide was shown to be effective in purifying glycinin and beta-conglycinin in a three-step process as 95% and 80% concentrated fractions with precipitation yields of 28% and 21%, respectively. Recycling of the mixed precipitate of the intermediary step enables complete separation into the concentrated fractions. Fractionation acidity was precisely controlled by a simple modification of pressure. In addition, the occurrence of a pH overshoot was prevented at any point in the fractionation vessel, as the pH minimum was defined by its equilibrium relationship with carbon dioxide operating pressure. The removal of the glycinin precipitate was an important factor in the purification procedure. The yield of the individual concentrated glycinin and beta-conglycinin precipitate fractions was a function of carbon dioxide pressure, extract concentration and, to a much lesser extent, temperature.

Research paper thumbnail of Mathematical modeling of the mass transfer from aqueous solutions in a supercritical fluid during particle formation

Research paper thumbnail of Supercritical drying of lysozyme from aqueous solution