Milk and milk products

List the components of milk and identify which one is the most abundant.

Components of whole milk in decreasing order are:

water

milk solids (milk fat and milk solids-not-fat)

lactose

proteins (casein and whey)

minerals

Is milk composition the same every time?

exact nutrient content (especially fat and protein content) varies somewhat by the species

List the types of fatty acid contents in milk ranking them by their percentage that makes up milk fat.

1. saturated 62.3%

2. monounsaturated 28.7%

3. polyunsaturated 2.4%

What is a fat-globule membrane composed of?

Contain phospholipids, proteins (enzymes, lipoproteins)

What are some characteristics of lactose in milk?

-Lactose is not very sweet unless hydrolyzed by addition of lactase.

-It is also converted to lactic acid by bacteria in yogurt, or sour cream.

- Aged cheese has ALL lactose fermented to lactic acid.

Caseins

• Precipitate to form curd (to begin cheese-making)

• Can be made with either renin or acid

• Aggregate to form micelles involving calcium and phosphate groups. Micelles then form colloidal dispersion which scatter light and give it opaque white color

4 types of caseins in fragile colloidal dispersions

alpha, beta, kappa, gamma

-        Most abundant component of milk

water

Monomers of lactose

galactose and glucose

How to make lactose free milk?

add lactase enzyme

is lactose soluble?

not very much- precipitates very easily giving ice cream a grainy texture

Micelles

hydrophobic core, hydrophilic surface

smaller than fat globules

kappa casein stabilizes colloidal dispersion

casein to whey ratio in milk

80 : 20

Whey main proteins

a-lactalbumin and B-lactoglobulin

whey

·       Denatured by heat

·       Do NOT coagulate when rennin is added

·       When rennin curds are formed, whey remains in liquid

Isolated and commercially sold as dietary supplements

Casein precipitate to form curd with RENNIN

(enzyme from calf stomach)- enzyme cuts hydrophilic portion of kappa casein which makes them clump together (aggregate) to protect themselves. This Destabilizes colloidal dispersion.

Casein precipitate to form curd with ACID

1.     Acid (H+) interacts with the negatively charged casein molecules which have been repelling each other. The counteracts repulsive forces result in precipitation.

How is whey formed?

Whey is denatured by heat, and they do NOT coagulate when rennin is added in contrast to casein. Therefore, the liquid that remains after that process is called whey

how does the food industry use whey?

it is purposefully isolated and sold by the food industry as dietary supplements.

What are the vitamins and minerals in milk?

Calcium

phosphorus

Vitamin A and D (fat soluble, and does NOT occur in whey)

riboflavin (light sensitive)

potentially potassium, sulfur, magnesium, sodium, and chloride.

Batch/HOLD method - pasteurization

Low temp 63C for long time 30 min

cooled to 7C

MOST COMMON

HTST method - pasteurization

High temp 72C for short time 1t sec

cooled to 10C

Flash method - pasteurization

Higher temp 100C for extremely short time 0.01 sec

ultra pasteurization method - pasteurization

138C for 2 sec

LONG SHELF LIFE 3 months

kills microorganisms

Ultrahigh temperature (UHT) method - pasteurization

138C or more for 2-6 sec

milk can be stored unrefrigerated until opened

SOME FLAVOR CHANGES

kills microorganisms

Which enzyme is present in raw milk? Why is this enzyme important in the pasteurization process?

Alkaline phosphatase is present in raw milk and is important in pasteurization because we test for its activities to make sure that pasteurization worked, and that other bacteria were killed. If the enzyme has been deactivated, then the milk is safer to drink as it has effectively been destroyed by pasteurization.

why must milk be homoginized?

prevent fat separation known as “creaming” mechanically with high pressure to break up fat globules = TOO SMALL TO FORM CREAM

Results of homogenized product

• richer texture

• bland flavor

• whiter

• less heat stale

• foamier

What is the process of making natural cheese?

1.     Form the curd (coagulation of casein)

2.     Treating the Curd-  cut, heated, salted, and pressed or kneaded to remove remaining whey

3.     Curing and ripening- contribute to unique flavor of different cheese, the long it ages the more the flavor changes because proteins fats and lactose get broken down to AA, fatty acids, and lactic acid. There are optional treatments like adding salt for bacteria, adding bacteria for molds like brie, or kneading for texture like mozzarella

clarification - via centrifuge

removes large size impurities

fat modification via centrifugation

• fat free (skim)

• reduced fat

• low fat

evaporation

volume production for canning and transportation

• evaporated milk

• sweet condensed milk

ferementation

uses microbes to ferment lactose into lactic acid- probiotics okay

RESULTS IN LOW PH AND THICK PRODUCT

• yogurt/kefir

• buttermilk

• cheese

how to concentrate cheese curd?

drain the whey by cutting, squeezing, or heating

overrun

increase in volume that occurs when ice cream is frozen with agitation (adds air)

how to make ice cream

milk + salt + sugar + egg yolk + flavor

rapid freezing to agitation to overrun

Flavor compounds affected by heat, fermentation, and storage

short chain fatty acids/free fatty acids, diacetyl, complex/organic/volatile compounds

xanthine oxidase

releases riboflavin from FAD in whey

Alkaline phosphatase

temporarily heat resistant- activity indicates lack of pasteurization

What is a complete protein

a protein that contains all essential AAs