Exam Summary - Food Ingredient Functionality - Proteins
2024
,Chapter 1; Introduction
1. Know that variation within a set of ‘similar’ protein ingredients can be as large as variation between sets
of different protein ingredients.
2. Know the main factors that cause the variations of protein ingredients.
• Ingredient itself:
- Source of the ingredient
- Isolation method
- Modification method (hydrolysis)
- Drying method (spray drying or roller drying)
All affect the ingredient composition, molecular structure, and its powder properties
• Inside the food product:
- Other ingredients (affect pH) and electrostatic repulsion/attraction
- Processing technique in the factory used (protein shake or a bar for
example)
- Storage conditions
,Chapter 2; Interactions between proteins
Understand the protein properties ‘surface charge density’ and ‘surface hydrophobicity’.
Surface charge density describes the number of charges (positive or negative) per surface area of
protein surface.
• Changes with changing pH conditions
• Changes with salt concentration (counterions)
Zeta potential (mV), also called electrostatic potential or surface potential, which is a measure for the number of
charges on the surface of the protein (or protein particle or emulsion droplet).
Surface hydrophobicity of proteins refers to regions on a protein's surface that are nonpolar and repel water, while
hydrophilicity refers to areas that are polar and interact favorably with water. Proteins are hydrophobic when they
have nonpolar amino acids (like leucine or valine) on their surface, and hydrophilic when they have polar or charged
amino acids (like serine or lysine) on their surface.
Understand the effect of pH and salts (counterions) on electrostatic interactions between
proteins.
pH affects electrostatic interactions between proteins by altering the charge on their surface, which can enhance or
weaken attractions or repulsions depending on whether the pH shifts their ionization states.
Salts reduce electrostatic interactions by introducing counterions that neutralize surface charges, diminishing the
strength of these interactions and potentially altering protein behavior.
, Chapter 3; Protein solubility
Understand the effect of pH, protein concentration, enzymatic hydrolysis, heating and salts on protein
aggregation and how this is related to protein properties (surface charge and
hydrophobicity).
Effect of pH on protein aggregation: Changes in pH can alter a protein’s surface charge, affecting the balance
between electrostatic repulsion and attraction. This can either prevent aggregation by maintaining charge repulsion or
promote aggregation if neutralization of surface charges allows hydrophobic regions to interact.
PI with proteins with high exposed PI with proteins with low exposed hydrophobicty
hydrophobicty (aggregation) (almost no aggregation)
ex. Casein ex. Whey
Effect of protein concentration on aggregation: Higher protein concentrations increase the likelihood of protein
molecules interacting, which can promote aggregation, especially when stabilizing forces like electrostatic repulsion
are weak. At lower concentrations, proteins are less likely to collide and form aggregates.
Enzymatic hydrolysis: The secondary/tertiary structure of the protein will be lost, leading to
exposure of hydrophobic groups and increased attractive interactions between proteins.
Effect of heating on protein aggregation: Heating can cause proteins to unfold, exposing hydrophobic regions that
are normally buried inside the structure. These exposed regions can interact with each other, leading to aggregation
as the unfolded proteins attempt to minimize their exposure to the solvent.
Effect of salts on protein aggregation: Salts can shield surface charges on proteins, reducing electrostatic
repulsion and promoting aggregation, especially if hydrophobic patches on the protein surface become exposed. At
high salt concentrations, hydrophobic interactions dominate, leading to increased protein aggregation.
e.g. Na+, Cl-, Ca2+, PO42-) screen charges on the protein surface, which lowers the electrostatic interactions. The
effect that salt has on protein solubility, depends on the salt concentration (or, ionic strength) as well as the type of
salt.
2024
,Chapter 1; Introduction
1. Know that variation within a set of ‘similar’ protein ingredients can be as large as variation between sets
of different protein ingredients.
2. Know the main factors that cause the variations of protein ingredients.
• Ingredient itself:
- Source of the ingredient
- Isolation method
- Modification method (hydrolysis)
- Drying method (spray drying or roller drying)
All affect the ingredient composition, molecular structure, and its powder properties
• Inside the food product:
- Other ingredients (affect pH) and electrostatic repulsion/attraction
- Processing technique in the factory used (protein shake or a bar for
example)
- Storage conditions
,Chapter 2; Interactions between proteins
Understand the protein properties ‘surface charge density’ and ‘surface hydrophobicity’.
Surface charge density describes the number of charges (positive or negative) per surface area of
protein surface.
• Changes with changing pH conditions
• Changes with salt concentration (counterions)
Zeta potential (mV), also called electrostatic potential or surface potential, which is a measure for the number of
charges on the surface of the protein (or protein particle or emulsion droplet).
Surface hydrophobicity of proteins refers to regions on a protein's surface that are nonpolar and repel water, while
hydrophilicity refers to areas that are polar and interact favorably with water. Proteins are hydrophobic when they
have nonpolar amino acids (like leucine or valine) on their surface, and hydrophilic when they have polar or charged
amino acids (like serine or lysine) on their surface.
Understand the effect of pH and salts (counterions) on electrostatic interactions between
proteins.
pH affects electrostatic interactions between proteins by altering the charge on their surface, which can enhance or
weaken attractions or repulsions depending on whether the pH shifts their ionization states.
Salts reduce electrostatic interactions by introducing counterions that neutralize surface charges, diminishing the
strength of these interactions and potentially altering protein behavior.
, Chapter 3; Protein solubility
Understand the effect of pH, protein concentration, enzymatic hydrolysis, heating and salts on protein
aggregation and how this is related to protein properties (surface charge and
hydrophobicity).
Effect of pH on protein aggregation: Changes in pH can alter a protein’s surface charge, affecting the balance
between electrostatic repulsion and attraction. This can either prevent aggregation by maintaining charge repulsion or
promote aggregation if neutralization of surface charges allows hydrophobic regions to interact.
PI with proteins with high exposed PI with proteins with low exposed hydrophobicty
hydrophobicty (aggregation) (almost no aggregation)
ex. Casein ex. Whey
Effect of protein concentration on aggregation: Higher protein concentrations increase the likelihood of protein
molecules interacting, which can promote aggregation, especially when stabilizing forces like electrostatic repulsion
are weak. At lower concentrations, proteins are less likely to collide and form aggregates.
Enzymatic hydrolysis: The secondary/tertiary structure of the protein will be lost, leading to
exposure of hydrophobic groups and increased attractive interactions between proteins.
Effect of heating on protein aggregation: Heating can cause proteins to unfold, exposing hydrophobic regions that
are normally buried inside the structure. These exposed regions can interact with each other, leading to aggregation
as the unfolded proteins attempt to minimize their exposure to the solvent.
Effect of salts on protein aggregation: Salts can shield surface charges on proteins, reducing electrostatic
repulsion and promoting aggregation, especially if hydrophobic patches on the protein surface become exposed. At
high salt concentrations, hydrophobic interactions dominate, leading to increased protein aggregation.
e.g. Na+, Cl-, Ca2+, PO42-) screen charges on the protein surface, which lowers the electrostatic interactions. The
effect that salt has on protein solubility, depends on the salt concentration (or, ionic strength) as well as the type of
salt.
