Dairy Science 1

Milk

Lacteal secretion, free from colostrum, obtained by the complete milking of one or more healthy cows. Milk that is in final package form for beverage use shall have been pasteurized or ultra pasteurized and contains >8 1/3% MSNF and >3 1/4% MF

Implications of milk definition

Lacteal secretion: no water can be added

Colostrum: first milk containing high levels of immunoglobulins after the first few days after calving

Complete milking: incomplete milking can lead to mastitis (infection of breast tissue)

Healthy cow: no mastitis or brucellosis

Pasteurized or ultra pasteurized: NO RAW MILK

% MSNF and MF: protects against watered down milk

Composition of milk

Water, fat, protein, carb (lactose), minerals, and vitamins

Vitamins in milk

Fat-soluble: A (beta carotene), D and E

Water-soluble: C, B2, B2, B6, B12, pantothenic acid, niacin, biotin, folic acid

Minerals: calcium

Factors that vary milk composition

Individual cows, stage of lactation, szn of the year, breed, feed, herd, weather, health, age

Holstein

Highest quantities (lb) of milk, with lower protein (3.3%) and fat (3.5%)

Jeresy

Lower production, milk has highest protein (4.0%) and fat content (5.2%)

Guernsey

High protein (3.7%) w/ high fat content (3.7%) and is high in beta-carotene content (unique yellow color)

Milk production overall process

Hauling, receiving, storage →

Clarification, separation → storage

standardization, pasteurization → byproduct processing

Homogenization, vitamin fortification → packaging

Prepping cow for milking

bovine gestation (pregnancy period) is 9 months

First milk: collostrum

• high in serum proteins, large amounts of antibodies

at 72hrs, milk production begins

Lactation period, how much do cows produce

305 days, 44 weeks

7000kg milk, with 1000kg needed to feed calf

Milk yield peaks at 10 weeks and slowly decreases when lactation period goes on

Milking protocols and facts

milk is sterile upon milking

Use of teat dips to sanitize teat before milking

microbial quality is dependent upon how milk is handled

Machine milking

Alternates between on and off - 50-60 times/min

Massage phase: vacuum off

Expansion phase: vacuum applied

Bulk tank

Storage, refridgerated

Hauler role

Quality check: smell, record temp

Record amount of milk at pick up w/ calibrated dip stick: X in = X lb of milk

Agitate for 5-10 min: sample of milk for antibiotic tests

Pump milk out, rinse, move onto next farm

Antibiotic implications

Farmers are liable for any milk they contaminate, so not having antibiotics is better

Quality control at the plant

<45 F

representation sample

• titratable acidity: below 0.17

• over 0.17: direct microscopic count of somatic cells (mastitis, counts live and dead cells, identifies contamination sources)

• antibiotic testing

Clarification

Remove sediment and somatic cells → filtration centrifuge

Separation

Removed fat from the fluid milk → centrifugation

1. cream (10-12% fat)

2. skim milk

Standardizing milk

Every kind of milk is mixed together, fat separated, added back in specific percentages

1%, 2%, whole is 3.6%

Vitamin supplementation to reduced fat milk

Added after separation prior to homogenization

vit A: 2000 international units/quart of milk

vit: 400 international units/quart

Homogenization

Push milk through small orifice, creating a large differential in pressure → breaks up fat globules

• 1-12 μm → 0.8 μm diameter

Pasteurization

Thermal process aimed at destroying specific pathogenic/spoilage organisms w/ 6-7 10 fold reduction

D

The time required for the death rate curve at a given temp. to traverse one log cycle

Time required to destroy 90% of the organisms at a given temp

log cycle: 10 fold reduction (changing decimal point position)

Heat processing

Defined with two components:

1. temperature

2. given amount of time

Holding temps & lethality

Holding times decrease as temp increase

All types of processing result in similar lethality bc:

• D-values are measured at each temperature