Exam 1: Dairy Manufacturing II

Milk comp.

Water 86, fat 4, protein 3

factors impacting milk comp

Breed, environment, health, nutrition

Breed with high milk fat

Jersey

Hot and humid months

depress milk fat and protein concentration

mastitis

High somatic cell count and decreased fat

grazing vs mixed ration

Fat and protein change slightly

Definition of milk

-Lacteal secretion, practically free from colostrum

-Not less than 8.25% milk solids not fat

-Not less than 3.25% milkfat

-Milk may be homogenized

What is suspended in milk to make color

fat globules and Casin micelles

milk structure pic

hydrophilic

Water loving

Proteins fold to expose primarily

hydrophilic groups to water

water activity

amount of water available to participate in

reactions

Removal of water from a dairy

product increases its shelf life by reducing water activity

true

Removal of water from dairy products is important for…

microbial safety

most important water activity

.85

no food poisoning below…

.85

moisture content of milk

87%

what hair product is most microbiologically stable

milk powder

In which dairy products can pathogens reasonably grow?

milk/cheese

In which dairy products can mold/yeasts reasonably grow?

cheese, milk, yogurt

lactose

major carbohydrate in milk

disaccharides of glucose and galactose

lactose forms

α-, and β-lactose (most soluble)

Lactose solubility

relatively low

lactose crystals

sandy defect

lactase

enzyme that breaks down lactose

maillard reaction

What component of milk is most susceptible to variation?

Fat

Prior to milk standardization, what is the approximate percentage of lactose in milk?

5%

A protein will fold to shield ____ amino acids from water

Hydrophobic

Milk fat

mainly composed of triglycerides

milk fat is contained in…

globules

variation of fatty acid is influenced by…

genetics, stage of lactation, feed, and season

emulsion

a fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible

milk fat microstructure

fat is low density and…

hydrophobic

milk fat globule membrane benefits

cognitive/in formula

lipolysis

hydrolysis of milk fat

_____ can hydrolyze milk fat

lipase

excessive levels of lipolysis are undesirable and result in ___

rancidity

homogenization

exposes fat to lipase

pasteurization

inactivates lipase

melting

crystallization process

func. of caseins

delivery sys. for calcium and amino acids

milk proteins

Casein micelles: 80%

Whey Proteins: 20%

Isoelectric point

pH which molecule has no electric charge

______ is the major whey protein

β-lactoglobulin

Denaturation

unfolding secondary and tertiary structure

β-lactoglobulin is not found in _____

human milk

α-lactalbumin is ___ heat stable than β-lactoglobulin

more

colostrum

richest source of bovine immunoglobulins

What percent milk is fat

4-5%

What contributes to the off flavors produced through the hydrolysis of fatty acids in milk fat?

The short chain fatty acids

Milk is __% protein

3.4

Which component of milk is most susceptible to variation?

Fat

Casein micelle

micelle

a loosely bound aggregation of several tens or hundreds of atoms, ions, or molecules, forming a colloidal particle

casein micelles carry ______ compounds

hydrophobic

Isoelectric point of caseins

4.6

Acidification in CM

Casein Micelle structure

Acidification brings casein micelles closer to their ___________

Isoelectric point

Casein micelles are the _______ in many dairy products

building blocks

Casein proteins account for approximately what percent of milk proteins?

80%

Which casein(s) are located primarily in the hydrophobic core of casein micelles?

α-casein (alpha-casein)

β-casein (beta-casein)

True or False: High-temperature, short-time pasteurization denatures casein proteins?

False

Milk is high (> 50 mg minerals/100 g product) in which of the following minerals?

phosphorus

Fermented milks

are made from pasteurized milk using specific bacteria that lower the pH to 4.6, causing casein to coagulate.

Synersis

liquid (whey) is expelled from a gel or coagulated protein network, like in yogurt or curd, causing the gel to shrink and release moisture

Yogurt def

contains the lactic acid-producing bacteria (LB and ST)

yogurt contains not less than ___ percent milkfat and not less than___ percent milk-solids-not-fat

3.25, 8.25

yogurt has acidity of not less than ___ percent, expressed as lactic acid, or a pH of _____ or lower

0.7, 4.6

Yogurt processing diagram

milk prior to high heat diagram

Whey denaturation

When milk is heated, whey proteins unfold and stick to casein. This changes milk’s texture and how it acts.

Yogurt steps simple:

1. Heat milk to kill germs (pasteurize).

2. Cool milk

3. Add starter culture

4. Fermentation

5. Coagulation: Acid makes milk thicken into yogurt.

6. Cool and store

Three production methods of greek yogurt

Centrifugal Separation, Ultrafiltration, milk proteins added

Centrifugal separation

Yogurt is run through a process until all solids are concentrated (whey removed)

Ultrafiltration

Whey is separated from the yogurt by specially designed filters, retaining more proteins

Milk proteins are added

No need for separation as milk proteins are added from the beginning

Can have gritty or chalky mouth-feel

by-product of greek yogurt

acid whey

What step in the yogurt manufacturing process causes the association between whey proteins with casein proteins?

Heat treatment

What is the main reason milk protein concentrate would be added to yogurt mix?

To increase the firmness of the yogurt coagulum

In contrast to regular yogurt, Greek yogurt is...

higher in protein

off flavors that can be caused by milk fat

1. hydrolytic rancidity

2. Oxidative rancidity

Lipase is inactivated by the _____ process.

Pasteurization

Which casein protein is located primarily on the surface of the casein micelle?

K-Casein

Glue of the casein micelle

Calcium Phosphate

Butter: Product with milk fat content not

less than ___ but less than ___

80%, 90%

• Butter has maximum water content of…

16%

Butter processing

Solid fat content changes by…

changing temp. of storage

Aging

To promote crystallization of milk fat using

selected temperature regimes

churning

Phase inversion and emulsion destabilization from oil-in-water to water-in-oil by physical agitation

Butter manufacturing diagram

Traditional buttermilk

The liquid drained following fat coalescence

in butter manufacture

•High in phospholipids

Cultured buttermilk

lightly salted, fermented product

prepared usually from low-fat milk

• Uses mixed mesophilic starter

culture, which produced diacyetyl and acetic acid (in addition to lactic acid

Butteroil

not less than 99.6% mf