Dairy products
17 important questions on Dairy products
Building a dairy product value chain
- Semi-skimmed milk (3.5% protein / 1.5% fat)
- Cream (2.5% protein / 40% fat
- Butter (80% fat)
- Buttermilk
What do we produce from 850 billion kg of milk?
- liquid milk / fresh dairy
- cheese
- butter /butteroil
- milk powder
- condensed milk
- whey ingredients
- water
There are 3 key elements when going from milk to dairy products:
- (standardized) milk
- Cream
- Whey
Ingredients
- Lactic acid bacteria (cheese, yoghurt)
- Enzymes (cheese)
- Salt, sugar etc
Processes
- Heat treatment
- Drying
- Fermentation
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What are the 4 objectives about liquid milk products
- Absence of pathogenic micro-organisms (phosphatase negative)
- Prolonged shelf life
- Flavour, taste and nutritive value close to fresh raw milk
- No creaming during storage (homogenisation)
When looking at heat treatment there are desired and undesired effects, name them
- Inactivation of pathogens
- Inactivation of spoilage bacteria
- inactivation of enzymes
Sensory / nutrition
- Denaturation of proteins
- Aggregation of proteins
- Maillard reactions
- Degradation of lactose
- Off-flavour formation
- Degradation of vitamins
What is the basic process of pasteurised milk products?
- Thermization to inactivate micro-organims
- Separation /standardization to achieve the right composition
- Homogenization to prevent creaming
- Pasteurization to inactivate micro-organisms and enzymes
- Cold storage to limit microbial growth and enzyme activity
- Achievable shelf-life: several weeks during cold storage
When looking at pasteurised milk, the shelf life depends on (7)
- Initial number of bacteria
- Number of Bacillus cereus spores
- Pasteurisation conditions
- Recontamination after filling
- Storage temperature
- Growth rate of bacteria
- Activity of natural inhibitors
What is the basic process of sterilised milk products?
- Thermization to inactivate micro-organisms
- Separation / standardisation to achieve the right composition
- Homogenization to prevent creaming
- Sterilization to inactivate micro-organisms and enzymes
- Aseptic packaging to prevent any recontamination
- Order of steps can differ
- Ambient storage
- Achievable shelf-life: several months or even years
When talking about sterilised milk the product quality and shelf life depends on (6)
- Decimal reduction time of heat-resistant spores
- Residence time distribution
- No bacterial enzymes present that cannot be fully inactivated
- Inactivation of enzymes naturally present in milk
- Aseptic packaging (or in bottle sterilisation)
- Low oxygen content
Shelf-life of sterilised products is typically limited by sensory and physical stability
High quality milk should be low in
- Low number of bacteria
- Low number of psychrotrophic bacteria which form heat-resistant proteases and lipases (sterilised milk)
- Low number of Bacillus ceraus (pasteurised milk)
- Low number of very heat resistant spores (sterilised milk)
- Low somatic cell count, low free fatty acid content
- No antibiotics
How does age gelation occur
What are the characteristics, main variants and use of butter
- Product should contain minimum 80% milk fat
- Product should not contain more than 16% water
- Salt and starter cultures may be added
Main variants
- Sweet (non-fermented) or cultures (fermented)
- Salted or non-salted
Use
- At home use
- Ingredient
- Base material for milk fat products
Cream fermentation in butter
Diacetyl formation
Cooling and churning of cream to make butter -->
- Part of milk fat must be crystallized
- starter bacteria must be active
- fatty acid composition determines butter consistency
- different temp/time combinations for butter in summer and winter
Churning temperature important; 8-12 *C
Industrial method for butter making
- FFA in butter cream
- Butter milk can be dried
- Fat crystallisation not influenced by temperatures needed for starter growth
- Continuous process
- Sweet buttermilk!
Kneading butter granules, how?
- Excessive moisture squeezed out
- phase inversion from oil-in-water to water-in-oil
- large water droplets disrupted
The quality of milk for butter making
- Fat content
- Fatty acid composition
- Absence of off-flavours
- animal feed
- short chain fatty acids after lipolysis
- fat oxidation
- Absence of fat soluble chemical contaminants (PCB, dioxins, pesticides)
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