Food Science

Question 1

Conduction

Answer 1

Where heat is transferred from one molecule to another

Question 2

Convection

Answer 2

Where warm molecules rise + cooler molecules fall closer to source of heat

Question 3

Radiation

Answer 3

Where heat is transferred by electromagnetic waves from one place to another

Question 4

Coagulation

Answer 4

Setting; change in structure of protein brought about by heat (dry or moist methods), mechanical action or acids

Question 5

Colloidal structure

Answer 5

When two substances are mixed together

Question 6

Emulsion

Answer 6

Mixture of two liquids e.g oil and water, emulsifier e.g lecithin in egg yolk

Question 7

Gelatinisation

Answer 7

When wet heat is applied starch forms suspension, it swells at 60ºC, breaks open + thickens mixture at 80ºC, full gelatinisation complete at 100ºC, which thickens + sets sauce

Question 8

Shortening

Answer 8

When fat coats flour grains + prevents gluten from developing + absorbing water (gives waterproof coating), so product is crumby + short e.g shortcrust pastry, if made with lard

Question 9

Plasticity

Answer 9

Lower melting point for product, e.g. allowing customer to use spread straight out of fridge

Question 10

Aeration

Answer 10

Process of trapping air in mixture e.g. when egg whites are whisked, protein (albumin) stretches + traps air. If left to stand, they will collapse + can’t be whisked again. If heat is applied, they will coagulate. Another example, when creamed with sugar, air is trapped which expands.

Question 11

Caramelisation

Answer 11

Process of changing colour of sugar from white to brown when heated

Question 12

Dextrinisation

Answer 12

When dry heat is applied to flour + it browns as starch is changed into sugar

Question 13

Maillard reaction

Answer 13

When sugars are mixed with other products, e.g eggs + flour (which both contain protein) in baked products, browning occurs in these products e.g biscuits when they contain carbohydrates + protein

Question 14

Denaturation

Answer 14

When acids are used to change structure of protein in food

Question 15

Albumin

Answer 15

Protein found in egg white

Question 16

Syneresis

Answer 16

Usually refers to eggs; if overcooked or heated too quickly, protein shrinks as it coagulates + it becomes tough + separates from watery liquid of egg

Question 17

Gluten

Answer 17

Protein in flour (gliadin + glutenin, which when kneaded with water, form gluten). Bread needs strong flour (more than 10% protein) to provide stretchy dough. Plain flour has less protein, so it gives very crumbly texture (short) e.g shortcrust pastry in Quiche.

Question 18

Enzymic browning

Answer 18

Oxidation reaction of enzymes in fruit + vegetables resulting in flesh browning e.g apples, pears, bananas, potatoes, avocados + lettuce. Happens because cells are exposed to oxygen, which react with enzyme Polyphenoloxidase to create melanin giving brown colour. Prevented by adding citrus acid e.g lemon juice as it slows down PPO activity + ties up copper ions, reducing colour change

Question 19

Oxidation

Answer 19

Presence of oxygen creates chemical changes. Antioxidants reduce rate of oxidation, otherwise food deteriorates. Oils become rancid, fruit + vegetables brown etc. Signs of oxidation: discolouration, sticky touch + food becomes darker + cloudier

Question 20

Fermentation

Answer 20

When given warmth, moisture, food + time, yeast produces carbon dioxide + alcohol. Yeast can be used to are bread-based products e.g Cinnamon + Hot Cross buns, Pizza + Bagels