Lecture 5 - Food Chemistry Flashcards
What is the moisture content?
Ratio of the mass of water to the total mass of food
What is water activity?
• Partialvapor pressureof water in a Substance divided by the standard state partialvapor pressureof water
Measures the availability of water as solvent for chemical and biochemical reactions.
Determines the shelf life of foods.
Because it determines water available for chemical and microbial reactions.
What can do done to reduce the water activity of foods?
Heating
Freezing
Drying
Adding humectants
What is the difference between water content and water activity?
Difference between moisture content (how much water is present in the food) and water activity (how much water in the food is available for biochemical/microbial reactions
Functions of water?
Solvent for reactions to occur
Facilitate heat transfer between food products
Solvent for water soluble vitamins (C/B6/B12)
Act as plasticizer (reduce brittleness/increase flexibility)
Functional properties of sugar
Sweetening agent
Precursor to processed flavour in cooked foods
Adds to bulk and texture of foods
Sugar carrier in pharmaceutical products
Glycogen (energy storage for animals)
What are hydro colloids?
homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
○ Hydro-colloids - suspended in water
Used to increase viscosity - help emulsion to be stable - prevent easy movement of molecules in the emulsion.
Examples: guar gum, carrageenan (from seaweed), gum arabic, xanthan gum (from microbes), methyl cellulose (modified cellulose) etc.
What are enzymes?
Enzymes are biological catalysts (made from proteins) that catalyse/speed up biochemical and metabolic reactions in our body.
What is denaturation of proteins?
destroy the characteristic properties of (a protein or other biological macromolecule) by heat, acidity, or other effects which disrupts its molecular conformation.
What is water holding capacity and what can it be affected by?
Ability to interact and bind with water
Affected by pH/salt/temperature
What are the shapes of protein?
Globular (spherical) - myoglobin
Fibrous (elongated) - collagen
What is the optimum temperature of enzymes?
30 to 40 degrees
