Summary FCH-30306 Knowledge clips and reader
Marly Verest
Summary FCH-30306 FIF
Knowledge clips and reader
Proteins
Introduction
Functionality of proteins
- Nutritional e.g. essential amino acids
o Affected by primary structure = amino acid sequence
- Physiological e.g. bio-active peptides, anti-nutritional factors
o Affected by primary structure = amino acid sequence
- Physical/technological e.g. texture in bread, beer foam
o Affected by tertiary structure = three-dimensional form
Why study proteins?
- Increase functionality
o New product formulations
o Avoid allergic responses
- Reduce variability between batches
Production of protein isolates
Isolation of proteins – general scheme First step = removal of other compounds
Use difference in:
- Solubility (precipitations)
- Size (filtration, size-exclusion
chromatography)
o Microfiltration, ultrafiltration,
nanofiltration, reverse
osmosis
- Charge (ion-exchange
chromatography)
Protein concentrates and isolates are heterogeneous
- Contain non-protein compounds
- Several different proteins
- ‘main’ protein can be present in different forms e.g. glycated, denatures, and aggregated
1
, Summary FCH-30306 Knowledge clips and reader
Marly Verest
Properties of hydrolysates
Characterization of proteins hydrolysates
- Degree of hydrolysis (DH)
o Solubility of hydrolysates affected by:
Exposure hydrophobic groups
Loss of single iso-electric point (pI)
o Gel properties: Changed electrostatic and hydrophobic interactions result in changed
aggregation and gel properties
o Foam and emulsions: Composition and properties of hydrolysates depend on DH as
well as enzyme and hydrolysis conditions (can have good techno-functional
properties until the peptides become too small)
- Concentration of intact protein
- Molecular weight distribution of peptides
- Identification of peptides
- Quantification of the peptides
Effect of heating and processing
Reasons to heat protein preparations
- Inactivation e.g. bacteria/spores, endogenous enzymes
- Product modification e.g. increased gelling properties
Effect of heat on protein preparations
- Chemical modifications e.g. Maillard reaction, cross-link reaction, dephosphorylation, …
- Physical changes
o Denaturation (globular protein)
o Dissociation (micellar proteins)
o Precipitation of Ca-phosphate (caseins)
Measuring protein unfolding
- Differential Scanning Calorimetry (DSC)
o Enthalpy of unfolding (peak area) can be used to quantify fraction of ‘native’ protein
- Precipitation at iso-electric point
o Amount of soluble protein at pI can be used to quantify ‘native’ whey proteins
Proteins do NOT always denature when heated higher denaturation temperature in dry
conditions, so more protein unfolding during heating in solution (pasteurisation) than during spray
drying
2
, Summary FCH-30306 Knowledge clips and reader
Marly Verest
Structure function relation
Technological functionality (table chapter 2: Figure 2)
Challenge in making structure function relations
- Current understanding
o Rules of thumb for mechanisms
o Case-by-case observations
o Only a limited number of well-studied proteins
- Future understanding
o Systematic studies
o Better understanding of underlying mechanisms
o Quantitative predictions
Gel properties
Proteins have much less, or almost no effect on viscosity compared to polysaccharides due to the
small size
Gelatin gels
- Difference between sources of gelatin melting temperature
- Gel strength of gelatin gels depend on the amount of helices formed
Globular protein gels
- Native, unfolded, aggregate, gel formation
- Effect of ionic strength
- pH=pI high ionic strength fractal/random aggregate
Changing the gel properties: disulfide bridges
- Increased permeability
- Increased turbidity
- Syneresis
- Spontaneous gel rupture
3
Marly Verest
Summary FCH-30306 FIF
Knowledge clips and reader
Proteins
Introduction
Functionality of proteins
- Nutritional e.g. essential amino acids
o Affected by primary structure = amino acid sequence
- Physiological e.g. bio-active peptides, anti-nutritional factors
o Affected by primary structure = amino acid sequence
- Physical/technological e.g. texture in bread, beer foam
o Affected by tertiary structure = three-dimensional form
Why study proteins?
- Increase functionality
o New product formulations
o Avoid allergic responses
- Reduce variability between batches
Production of protein isolates
Isolation of proteins – general scheme First step = removal of other compounds
Use difference in:
- Solubility (precipitations)
- Size (filtration, size-exclusion
chromatography)
o Microfiltration, ultrafiltration,
nanofiltration, reverse
osmosis
- Charge (ion-exchange
chromatography)
Protein concentrates and isolates are heterogeneous
- Contain non-protein compounds
- Several different proteins
- ‘main’ protein can be present in different forms e.g. glycated, denatures, and aggregated
1
, Summary FCH-30306 Knowledge clips and reader
Marly Verest
Properties of hydrolysates
Characterization of proteins hydrolysates
- Degree of hydrolysis (DH)
o Solubility of hydrolysates affected by:
Exposure hydrophobic groups
Loss of single iso-electric point (pI)
o Gel properties: Changed electrostatic and hydrophobic interactions result in changed
aggregation and gel properties
o Foam and emulsions: Composition and properties of hydrolysates depend on DH as
well as enzyme and hydrolysis conditions (can have good techno-functional
properties until the peptides become too small)
- Concentration of intact protein
- Molecular weight distribution of peptides
- Identification of peptides
- Quantification of the peptides
Effect of heating and processing
Reasons to heat protein preparations
- Inactivation e.g. bacteria/spores, endogenous enzymes
- Product modification e.g. increased gelling properties
Effect of heat on protein preparations
- Chemical modifications e.g. Maillard reaction, cross-link reaction, dephosphorylation, …
- Physical changes
o Denaturation (globular protein)
o Dissociation (micellar proteins)
o Precipitation of Ca-phosphate (caseins)
Measuring protein unfolding
- Differential Scanning Calorimetry (DSC)
o Enthalpy of unfolding (peak area) can be used to quantify fraction of ‘native’ protein
- Precipitation at iso-electric point
o Amount of soluble protein at pI can be used to quantify ‘native’ whey proteins
Proteins do NOT always denature when heated higher denaturation temperature in dry
conditions, so more protein unfolding during heating in solution (pasteurisation) than during spray
drying
2
, Summary FCH-30306 Knowledge clips and reader
Marly Verest
Structure function relation
Technological functionality (table chapter 2: Figure 2)
Challenge in making structure function relations
- Current understanding
o Rules of thumb for mechanisms
o Case-by-case observations
o Only a limited number of well-studied proteins
- Future understanding
o Systematic studies
o Better understanding of underlying mechanisms
o Quantitative predictions
Gel properties
Proteins have much less, or almost no effect on viscosity compared to polysaccharides due to the
small size
Gelatin gels
- Difference between sources of gelatin melting temperature
- Gel strength of gelatin gels depend on the amount of helices formed
Globular protein gels
- Native, unfolded, aggregate, gel formation
- Effect of ionic strength
- pH=pI high ionic strength fractal/random aggregate
Changing the gel properties: disulfide bridges
- Increased permeability
- Increased turbidity
- Syneresis
- Spontaneous gel rupture
3
