milk and dairy production

Milk is the normal mammary secretion of milking animals without either addition to it or extraction from
Raw milk: milk which has not been heated beyond 40ºC or undergone any treatment or equal effect
Milk product: a product obtained by any processing of milk, which may contain food
additives, and other ingredients

made by WHO and FAO. for international harmonisation of food standards and trade in safe foods of a defined quality.

➢ Water: 87.3 % (85.5 – 88.7 %)
➢ Fat (lipids): 3.9 % (2.4 – 5.5 %)
▪ Whole milk 3.7%
▪ Semi-skimmed 1.8%
▪ Skimmed 0.1-0.3%
proteins 3.25 % (majority casein)
lactose 4.6 %
minerals 0.65 % : Ca, P, Mg, K, Na, Zn, Cl, Fe, Cu, sulfate, citrate, bicarbonate
acids 0.18 % : acetate, formate, lactate
enzymes : peroxidase, lipase, phosphatase, catalase
vitamins : A, C, D, riboflavin, thiamine

Cheese: more saturated fat and protein and less carbohydrate than milk.
Yoghurt: lower lactose content than milk, contain probiotics.

delivered to dairies
for supply
goes:
1- used in manufacture
2- used liquid consumption
3- stock change and wastage

FSA

• Temperature
• Total acidity
• Flavour
• Odour
• Tanker cleanliness
• Absence of antibiotics
• Microbiological quality (Somatic Cell Count (SCC), Aerobic Plate Count (APC))
• Butterfat content and solids-not-fat content analysed

72 hours

• Filtration
• Clarification: removal of sediment particles
• Decreaming: milk fat partially or totally reduced, centrifugation
• Standardisation: milk fat and, when required, solids-not-fat adjusted to standards
• Heat treatment:
• Homogenisation
• Cooling
• Filling and storage

pasteurisation
seterilisation

➢ To ensure safety of milk for human consumption by destroying pathogenic
bacteria
➢ To improve shelf life and keep quality by destroying undesirable enzymes and
spoilage bacteria

63C/ 30 min
done in batches

72 C/15 sec
continous flow
can increase time to reduce MAP

The alkaline phosphatase test :
Milk properly pasteurized is alkaline phosphatase negative

Milk is filtered through a special membrane to remove even further bacteria and
bacterial spores

➢ Microbiocidal control measure (complete elimination of microorganisms)
➢ UHT (“ultra high temperature”) 135 -150 C/2-5 sec continuous operation

• Direct mixing of the steam with the product
• Indirect heating by means of heat exchanging surface

aseptic packaging/ filling

pros: changes in comp are small, long shelf life, cheaper storage and transport

cons: reduction in vitamin content, changes in flavour and deteriorates flavour over time, sterility must be maintained.

➢ Milk from a healthy udder is virtually sterile at secretion.
➢ Contamination occurs mainly during or after milking.

▪ Spoilage organisms: affect shelf life and quality.
▪ Pathogenic: pose food safety risks.
▪ Technological desirable: used in fermentation and processing.

▪ Pseudomonas spp.
▪ Bacillus
▪ Clostridium
▪ Lactobacillus
▪ Micrococcus
▪ Streptococcus

▪ Salmonella spp.- commonest
▪ Escherichia coli O157:H7 - commonest
▪ Campylobacter jejuni- commonest
▪ Bacillus cereus
▪ Listeria monocytogenes
▪ Yersinia enterocolitica
staph. a toxins

Aspergillus, Penicillium, Fusarium spp.

poor hygiene during milking, processing, or handling at any
stage.

role in processing and quality
for yogurt, cheese
• flavour, aroma, and alcohol production
• proteolytic and lipolytic activities
• inhibition of undesirable organisms

acidification- lactose to lactic acid
coagulation- rennet added, forming curds and whey
cutting, stiring, heating- promote further seperation
draining, salting, moulding
ripening- mature, proteolysis changes texture. further drop in pH

microbial quality of milk
biochemical ph and water activity
time and temp control- insufficuent ripening
hygiene of containers and utensils
slow acid development= more time for pathogenic bacterial growth
contaminated started cultures
contamination from ingredients post pasteurisation.

cream seperation
pasteurise cream
colling , ageing
stature culture optional
churning
washing
salt

▪ Use of unpasteurized cream:
▪ Poor hygiene of churns or washing water = recontamination
▪ Use of containers or utensils that have not been adequately cleaned and sanitized.

milk homogenised
pasteurised
cooling
inoculation with stater culture
fermentation: lactose to lactic acid
cooling
flavour

Lactobacillus delbrueckii ssp.
bulgaricus, Streptococcus thermophilus

▪ Starter culturefailure: slow or incomplete acidification= growth of
pathogens.
▪ Use of contaminatedfruit or flavoring ingredients.
▪ Inadequate sanitation of fermenters or filling machines.

mix ingredients
pasteurise
homogenise
cooling, ageing
freezing and aeration
flavours
hardneing and frozen storage

▪ Inadequate pasteurization.
▪ Recontamination after pasteurization - when adding flavours
▪ Contaminated air supply to the freezer that introduces microorganisms.