1. Dairy Lecture Alec Barrett-Wilsdon
James Buckel

2. Background
Types of Dairy:
Milk
Yogurt
Cheese
Cream
Butter
Related:
Eggs

3. Milk Overview
•Purpose of milk is to provide nutrients and immunity to mammalian
infants
•pH 6.4 to 6.8 (slightly acidic). Sometimes called basic – why?
•pH decreases over time due to lactic acid bacteria – souring
•Roughly 1.5:1:1 carbohydrate : protein : fat ratio (whole milk)
•Milk nutritional content changes as the calf ages
•Most milk commercials use white paint

4. Colostrum
•Directly after birth, colostrum is secreted from
the mammary gland.
• Provides antibodies to help protect the newborn until its
own immune system is established. Within 72 hours,
the composition of colostrum returns to that of fresh
milk
• Colostrum is more yellow than mature milk
• All commercial cow’s milk is mature, unless otherwise
labeled. Immunoglobin domains of an antibody

5. Milk
Why the difference?

6. Lactose intolerance

7. Lactose intolerance
•Caused when the body stops production of lactase in the small intestine
•All mammalian milk has lactose in it (including human)
•As early as 8000 BCE, humans learned how to domesticate animals
•Our ancestral condition is lactose intolerance. The derived condition is tolerance.
•In tropical countries, weather and lack of refrigeration prevented strong reliance on dairy
•In northern Europe and North America dairy is integrated into traditional diet
•NOT a food allergy
•Symptoms include bloating, diarrhea, cramps, and nausea
•65% worldwide population are intolerant as adults

8. Lactose intolerance prevalence

9. composition
•Depends on animal, region, diet
•87.3% water (range of 85.5% - 88.7%)
•3.9 % milkfat (natural range of 2.4% - 5.5%)
•8.8% solids other than fat (range of 7.9 - 10.0%):
 protein 3.25%
 lactose 4.6%
 minerals 0.65% - Ca, P, citrate, Mg, K, Na, Zn, Cl, Fe, Cu, sulfate, bicarbonate
 acids 0.18% - citrate, formate, acetate, lactate, oxalate
 enzymes - peroxidase, catalase, phosphatase, lipase
 gases - oxygen, nitrogen
 vitamins - A, C, D, thiamine, riboflavin
Lactose
A micelle

10. composition
• Unprocessed milk is an emulsion with fat globules
dispersed in skim milk (casein micelles are in a
colloidal suspension)
• If raw milk were left to stand the fat would separate
and form a cream layer (top or bottom?)
• During the separation of whole milk, you get a fat-
depleted stream for milk and the fat-enriched stream
for cream
Raw milk
Un-homogenized
milk

11. Milkfat
•67% saturated fats
•mainly triglyceride (98.3%)
•small amounts of MAG, DAG, and free fatty acids
•Phospholipids (0.8%) associated with the fat
globule membrane and cholesterol (0.3%) is
located in the core
•Melting point 37° C (What is the significance of 37°
C?)
•Lubrication, creamy texture, unique butter flavor
Triacylglyceride (TAG)
unsaturatio
n

12. Milk processing
•Homogenization is the stabilization of the fat
globules in milk brought about by passing milk
under high pressure through a tiny opening –
the goal is to eliminate natural cream separation
•Fat destabilization (clumping of the fat globules)
is necessary for structure formation in butter,
whipping cream, and ice cream
•Pasteurization – rapid and short increase in
temperature to kill bacteria; does not change
nutrition
Homogenization

13. Milk protein: casein
•Caseins are the primary protein in milk (80%) - other 20% is whey.
•Exist as micelles whose biological function is to deliver large amounts of
calcium to the infant
•Why is it able to do that? High phosphate content
•Denaturation at pH 4.6
•Random, loose structure due to the amino acid composition (high proline
content)
•Heat alone will not denature casein (acid is needed, too)
•Curdles once hydrophobic residues are exposed

14. Milk Proteins: whey
•Collection of proteins and vitamins appearing in the
supernatant of milk during cheese production
•ß -lactoglobulin, α-lactalbumin, bovine serum
albumin (BSA), and immunoglobulins
•Many sulfur-containing amino acids
•More hydrophilic than casein, so good gelling
properties
•Supplements, yogurt, some cheeses (e.g. ricotta),
substitute for water
Curds and whey

15. Milk proteins: enzymatic action
•Lipoprotein lipase: splits fats into glycerol and free fatty acids.
•Plasmin: attacks casein; heat stable; may also play a role in the ripening and flavor
development of certain cheeses, such as Swiss cheese.
•Alkaline phosphatase: works at pH 9.8 (basic). Heat sensitive; indicator of proper
pasteurization
•Lactoperoxidase, lysozyme: anti-bacterial
In your stomach: few effects. Acidic nature of your stomach (pH = 2) hydrolyzes and
denatures milk proteins, deactivating them. Milk protein allergies are rare and unrelated
to lactose intolerance.

16. micronutrients
•Vitamins (organic)
• Milk includes all fat-soluble vitamins (ADEK) as well as
• B1 – thiamine, B2 – riboflavin, B6 – pyridoxine, B12 - cyanocobalamin
• niacin
• pantothenic acid
• Vitamins A and D are often supplemented to replace what was lost in the fat separation process
•Minerals (inorganic)
• All 22 essential minerals present in milk
• Minerals contribute to acid-base equilibrium (by pH buffering) in milk

17. Microorganisms
•Milk itself is sterile, but gets contaminated during milking, handling,
storage, and other pre-processing activities
•Some strains ferment lactose to lactic acid. Naturally occurring in milk
and used as starter cultures in the production of dairy products such as
yogurt.
• Lactococci: Streptococcus lactis, Streptococcus cremoris
• Lactobacilli: L. casei, L. lactis, L. bulgaricus

18. microorganisms
•Some bacteria produce extracellular lipases
and proteases that are not heat labile and
survive past pasteurization. Pasteurization is
not perfect and although refrigeration slows
growth, it does not stop it.
•Risk of pathogens including Listeria
monocytogenes, Yersinia enterocolitica, E. coli

19. yogurt
•Fermented milk product traditionally from Eastern Europe
•Eaten by itself, alongside main dish, or in baking.
•Pasteurized or unpasteurized
•Several factors influence the ability of the probiotics to survive in the product and
become active when entering the consumer's gastrointestinal tract
1. Physical conditions of product storage (e.g. temperature)
2. Chemical composition of the product (e.g. pH, carbohydrate content, nitrogen
sources, mineral content, and oxygen content)
3. Possible interactions of the probiotics with the starter cultures (e.g. antagonism,
synergism)

20. Yogurt Production
Heat is added, the milk is pasteurized, then it is
allowed to cool.
Bacteria is added (for yogurt formation and
probiotic purposes).
Lactose is converted to lactic acid; there is some
protein coagulation, and the whey removed.
Yogurt is technically a gel.

21. cheese
•Made from the pressed curds of any number of different types of animal milk
•Type of cheese used in cooking is highly dependent on culture
•Found in salads, casseroles, sandwiches, and even desserts (favorite
recipes anyone?)
•Fresh cheeses: high moisture content, usually mild, creamy taste, soft
texture
• Italian mascarpone, cottage cheese, cream cheese, ricotta
•Ripened cheeses can be aged for years—can be mild or sharp/pungent
• Firm, hard cheeses: Parmesan and pecorino for grating
• Soft-ripened cheeses: triple crème, brie
• Blue cheeses: Italian gorgonzola, Danish blue cheese

22. Cheese Production
Formed as microorganisms convert lactose to lactic acid; this lowers the pH
to the IEP of casein (pH = 4.6)
The enzyme complex Rennet is added, which denatures casein, separating
the hydrophilic and hydrophobic portions.
Heat is added, and casein curdles (precipitates out of the solution).
Whey is drained off, and remaining casein curds are pressed (to remove
water).
10 lbs of milk => 1 lb of cheese
Blue cheese = molds added

23. Ice cream
•Ice crystals: Created when the water starts to freeze, giving body. The main
objective is to keep the size of the ice crystals down as much as possible.
•Fat: Adds richness, improves density, flavor, ‘mouthfeel’ and smoothness
•Sweeteners: Improves texture and body. Also lowers the freezing point of the
mix (What does that mean for the ice cream?)
•Air: Tiny air cells whipped into the base mix are largely responsible for the
texture, and volume
•Addition of egg technically isn’t ice cream. It is custard.

24. Ice cream structure
Production: you blend the ingredients, rapidly
cool/freeze mixture while agitating, and prepare for
overrun.
Ice cream must be minimum 10% milkfat and 20%
total milk solids (fat + protein + lactose + minerals +
added sugar).
Stabilizers (proteins/carbohydrates) prevent the
accumulation of small ice crystals, which can create
larger, unpleasant crystals.

25. https://www.youtube.com/watch?v=-rlapUkWCSM
Ice Cream Production

27. Butter and cream
Cream is what naturally rises to the
top in milk; in commercial production, it
is separated by centrifugal action.
Cream is oil in water.
Minimum 18% fat; whipping cream is 30%
fat; heavy whipping cream is 36% fat
Butter results from agitation (i.e.
churning) of cream.
Butter is water in oil
>80% fat

28. Eggs
Contain:
Yolk, with cholesterol, triglycerides, phospholipids
(lecithin), fat soluble vitamins, some protein, Omega 3?
Egg White: majority of protein, lysozyme, water
Shell: CaCO3 composition. Inside of egg is sterile, but
there is bacteria on outside of shell

29. Egg structure

30. substitutes
•Baking: Soy margarine, fruit puree for a healthy twist, coconut butter
•Sautéing: Oil in place of butter
•Condiment: Nutritional yeast is deactivated yeast sold as a powder or flakes
•Cheese: Tofu mimics mozzarella or provolone on sandwiches or crackers. For
a cottage cheese or ricotta substitute, you can blend or mash silken tofu with a dash
of lemon juice. Good for dips, sauces, smoothies, pies, and pasta dishes.
•Imitation cheese is a fusion of tofu, calcium caseinate, rice starch, lecithin, and
various additives
•Milk: Lactose-free milk, almond milk, coconut milk, soy milk
•Ice cream: soy, rice, coconut alternatives

31. Bonus: dairy and peppers
Capsaicin – the active ingredient in hot peppers – binds to the TRPV1
receptor, which normally senses heat, acid, and physical abrasion.
The milk protein casein interferes with the capsaicin-receptor bonding and
allows it to be washed out of your mouth.
Capsaicin is non-polar, so polar
solutes like water will not affect it
Too hot? Drink milk (or alcohol!).
Capsaicin

32. Questions
1. Besides nutrients, what does milk provide to an infant?
2. Why is lactose intolerance more prevalent in certain races?
3. What are the two main proteins in milk? Which one carries calcium?
4. Yogurt is a __________, meaning it contains live cultures of bacteria.
5. Cheese is made from pressed ______.

33. discuss
What would you like to talk about in future lessons?
Format: helpful?
Anything in particular you want to cook/bake?