Chemical aspects of food technology Flashcards
What is often the first step in the processing of a plant-based raw material?
‘breking’ the plant tissue by cutting, grating, grinding and so forth. Leading to the release of various chemical compounds/enzymes.
In which two groups can food components be divided in?
the major- and minor food components. Major: present in food in large amounts. Minor: present in food in small amounts.
What are raw materials?
unprocessed foods as such, derived from the land or directly from animals.
What are processed foods?
Food products made from processed raw materials.
What are ingredients?
Processed foods from one single raw material.
What are complex food products?
Food products made from several ingredients and raw materials.
What are taste and aroma dependent on?
taste is determined by the sugar/acid ratio.
aroma is dependent on the volatile aroma compounds.
What do antioxidants do?
They delay or prevent oxidation reactions.
What are typical oxidation results?
- loss of quality of food
- loss of color
- loss of vitamins
Name two types of antioxidants.
antioxidants that scavenge free radicals and antioxidants that reverse oxidation reactions.
What is a phenolic compound?
a benzene ring with a hydroxyl-group attached to the ring, which acts as a antioxidant by reacting with the free radical HO*.
How can a radical be ‘trapped’ inside a phenolic compound?
Because of the resonance that takes place in the benzene ring and O atom.
What is °Brix equal to?
To the mass percentage dissolved dry matter in the liquid.
What is the pKa?
The pH value where there are equal molar concentrations of the non-dissociated and the dissociated acid present.
How can the sugar/acid ratio bee calculated?
By dividing the °Brit by the acidity.
When can a drink be considered drinkable?
With a sugar/acid ratio of 10 or higher.
What is the main cause of enzymatic browning?
The enzyme polyphenol oxidase, which is present in cells, becomes active when the cell structure is destroyed because then oxygen can enter the cells.
What is the first step of enzymatic browning?
The reaction of an o-diphenol with oxygen, becomes a quinone which further reacts with other phenolic compounds and finally forms melanin polymers.
Why is vitamin C often added to food as an antioxidant against enzymatic browning?
It can reverse the first reaction of enzymatic browning. Although after some time all ascorbic acid is used and the browning reactions are not stopped anymore.
What is the optimal PH for the activity of most polyphenol oxidases at room temperature?
A pH between 5-7
How is caramel made?
Sugar first hydrolyzes into the monosaccharide glucose and fructose. The glucose/fructose then react further. Depending on the situation specific aromas and brown-colored polymers will be formed.
What happens in the initial phase of the Maillard reaction?
a reducing sugar (a sugar where the ring can open) reacts with a free amino group into a glycosylamine.
What happens with denaturation?
Occurs when proteins are heated above their denaturation temperature. Proteins start to lose their tertiary and secondary structure: they unfold. This is often irreversible.
What can form a gel structure?
Through aggregation forming of the attraction between hydrophobic groups of several proteins.
How does starch gelatinization work?
Starch granules take up water and start to swell (irreversible). Starch molecules are solubilized and the crystalline regions are lost.
