Dairy Lecture Alec Barrett-WilsdonJames Buckel

Background Types of Dairy: Milk Yogurt Cheese Cream Butter

Related: Eggs

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

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

MilkWhy the difference?

Lactose intolerance

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

Lactose intolerance prevalence

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

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

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)

unsaturation

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

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

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

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.

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

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

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

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)

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.

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

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

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.

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.

Ice cream is technically a foam

https://www.youtube.com/watch?v=-rlapUkWCSM

Ice Cream Production

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

EggsContain:

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

Egg structure

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

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

Questions1. 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 ______.

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