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Butter

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Butter

Butter from cream Skimming of milk for butter production reduces costs  1.Only part of the original milk needs to be churned 2.Reduction of fat loss  (fat contents skimmed milk 0.05% and butter milk 0.4%)  3.Reduction in volume of buttermilk

Pre-treatment
- cream separation
- High pasteurization of cream
  - Micro-organisms are killed
  - Enzymes are inactivated
  - Cream becomes a better substrate for starter cultures (denaturation of serum proteins)
  - more resistant to oxidative deterioration
Churning
- Air bubbles are formed covered by proteins
- Air bubbles deform and break (surface area increases, temporarily increase of surface tension)
- Fat globules attached to the air bubbles
- Fat needles pierce the thin film between globule and the air-water interface
- Liquid oil spreads over the air bubbles and air bubbles break→fat globules are forced together
- Liquid fat acts as sticking agent
- Conditions
  - Part of milk fat should be crystallized
  - 8-12°C
  - If pre-cooling is not deep enough: too much fat in buttermilk
- features
  - Homogenized milk cannot be churned
  - Sour cream takes more time for churning than sweet cream
Traditional butter making v.s. NIZO procedure
- Distribution of FA
  - Hac = undissociated acid Ac- = dissociated acid
  - Classical method churning at pH 4.5→ HAc in fat
  - NIZO method churning at pH 6.5 → HAc in buttermilk
Kneading
- A steady-state droplet size will be the end result
- Very small droplets: flat taste, colour pale
- Shelf life depends on moisture distribution (and pH)
- shear stress G: high→disruption small water droplets; low→coalescence large water droplets (excessive moisture squeezed out)
Firmness of butter
- Fraction of solid fat
  - Temperature
  - Fatty acid composition
  - Compound crystals
  - Polymorphism
- Number&Size of fat crystals
  - Nucleation rate
  - Rate of crystal growth
- Number&strength of the bonds between fat crystals
  - Sintering
  - Recrystallization
- Crystal aggregate network
  - cold/warm/cold for soft butter in winter
    - 6-8°C Many small crystals are formed 18-23°C Melting of crystals that contain a high proportion of low melting TAGs & reduction of the number of crystals 14°C Growth of existing crystals, crystals formation is limited Final result: low number of big crystals which make thebutter soft
  - warm/cold/cold for hard butter in summer
    - Formation of many, small size crystals, which make the butter harder
- Work-softening process
- Temperature during storage
Other fat products
- Anhydrous milk fat
- Fractionated milk fat
- Recombined butter
- Low fat butter products