Lab exam of butter

Question 1

Flow diagram:

Answer 1

Raw milk
Skimming
Cream
Heat treatment
Vacuum removal of off-flavours
Cooling (6-8*C 2 hours)
Addition of LAB: inoculation and cream fermentation

Question 2

Principles used for butter production:

Answer 2

Foaming method: grinding cream
Concentration method: plate centrifuge to prepare high fat cream
Emulsification method: milk plasma is emulsified in pure milk fat

Question 3

What is important during butter production?

Answer 3

The cream is in good microbial quality
Iodine value is deciding factor
Must not contain ATB or disinfectants
Hygiene

Question 4

What is important during butter pasteurization?

Answer 4

95*C or higher
Negative peroxidase test
Not too intense heat treatment

Question 5

Vacuum deaeration:

Answer 5

Vacuum treatment to remove undesirable flavouring substances
Cream is heated to 78*C
Reduced pressure causes volatile flavouring and aromatic matter to escape in gas
Cream is returned to heat exchanger for pasteurisation and cooling

Question 6

What is important in bacterial souring (sour cream)?

Answer 6

The ratio between numbers of acid and aroma producers
- to produce sufficient diacetyl

Question 7

How is ripening?

Answer 7

Several hours at temp 5-10*C
- crystallisation

Question 8

How is churning:

Answer 8

5-10C, max 15C
- beating in of air
- churn: 30-45 min
- latter churning
- butter making machine

Question 9

How is washing of butter?

Answer 9

Mixing butter grains with cold water, and drain the water off
- reduce dry matter
- control temperature

Question 10

Working of butter is done to:

Answer 10

Transform butter grains into a continuous mass
Finely disperse moisture in butter
Regulate water content
Incorporate salts

Question 11

Sensory evaluation of butter:

Answer 11

Appearance:
- colour, purity, absence of physical contamination, absence of mould growth, uniformity of water dispersion
Consistency:
- body, texture, firmness
Flavour

Question 12

Butter defects:

Answer 12

Rancidity: lipolysis
Marbled butter: moulds
Unclean, cheese butter: psychotropic bacteria
Tallowy, fatty, fishy - fat oxidation
Fishiness
Cheesiness: lactobacilli
Barny
Malty
Musty
Colour defects

Question 13

Determination of water in butter:

Answer 13

10 g butter into cold and dry aluminium dish
The dish is held with forceps above burner
Water is removed by a circling motion
Sediment on bottom is brown
Sample is cooled and weighed

Question 14

Determination of fat oxidation in butter:

Answer 14

1.5-diphenyl-carbohydrazide + oxidized fat = red colour
Liberation of iodine from potassium iodide
Colorimetric ferric thiocyanate –> ferrous iron into ferric iron - red pigment
Optical density