1. Biotechnological Industries Unit 2

2. Dairy Industries Chapter 5

3. Milk 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

4. Milk treatment Can be treated/processed: a) removal of fat (skimmed/semi-skimmed) b) heat treatment - pasteurisation (72oC for 15 secs, then cooled) - UHT (138oC 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

5. Yoghurt 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

6. Yoghurt production

7. Cheese 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

8. Environmental Impact In the past whey was disposed of as waste Often poured into rivers/lakes But, whey is rich in protein So bacteria in rivers fed on the whey More bacteria led to other species dying - due to a lack of oxygen Upgrading Whey is now used as a feed for yeast Also used for pig food Whey powder used in many human foods

9. Aseptic Conditions 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