Biotechnological Industries

Unit 2

Dairy Industries

Chapter 5

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

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

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

Yoghurt production

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

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

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