Biotechnological Industries Unit 2 Dairy Industries Chapter 5

Biotechnological Industries Unit 2

Dairy Industries Chapter 5

Milk n n n Normal milk contains sugar, fat, protein, vitamins & minerals Sugar – provides energy Fats – energy & insulation Proteins – growth & repair Vitamins – protect from deficiency diseases Minerals – helps bones, blood, teeth, skin

Milk treatment n n n n Can be treated/processed: a) removal of fat (skimmed/semi-skimmed) b) heat treatment - pasteurisation (72 o. C for 15 secs, then cooled) - UHT (138 o. C for 2 -5 secs) - both help prevent bacterial growth - Resauzarin dye test for presence of bacteria (purple – white) c) evaporation (condensed) – milk heated to reduce water content

Yoghurt n n n n Produced from milk Yoghurt-forming bacteria added to heat treated milk Bacteria change sugar into lactic acid - this ‘clots’ & ‘thickens’ the milk Yoghurt is therefore tangy, acidic & slightly sour Most bacteria can’t grow in these acid conditions – natural preservative ‘Natural’ & ‘Bio’ yoghurts contain live bacteria

Yoghurt production

Aseptic Conditions n n n n n When working with micro-organisms, conditions must be sterile or aseptic - prevents experiment being contaminated - prevents micro-organisms escaping from experiment The following conditions should be used: - no eating or drinking - using protective clothing - washing hands - suitable work surfaces (glass/plastic) - sterilised equipment (e. g. autoclave) - a sterile inoculating loop to transfer microbes

Cheese n n n n n A solid food made from a liquid (milk) Milk needs to curdle first - cheese making bacteria are added - they change sugar into lactic acid Rennet is added to help the milk to curdle - milk changed into curds (solid) & whey (liquid) - acid clots the milk proteins into curds Curds are chopped and mixed with salt - cheese left to mature & develop flavour Whey can be re-used as part of cattle feed