Dairy Processing Operations

Dr. Mohammad Ashraf PaulDivision of Livestock Products TechnologyFaculty of Veterinary Sciences & Animal Husbandry SKUAST-K , Alusteng, Ganderbal Kashmir

Manufacture, packaging and storage of pasteurized Milk

RECEIVING MILK (Unloading,Grading,Sampling,Weighing,Testing

PREHEATING(35-400c)

FILTRATION / CLARIFICATION

COOLING & STORAGE

STANDARDIZATION

PASTEURIZATION

HOMOGENIZATION(Optional)

PACKAGING & STORAGE / DESPATCH

Unloading Grading sampling and testing

Sampling may be individual, composite (one or more individual samples) or Drip (whole days collection )

To keep the sample sweet- preservatives are used:a) Mercuric chloride or corrosive sublimate: poisonous colored tabs. (bright red) to prevent

the milk from being mistaken for food.b) Formalin: liquid - convenient to handle-

interferes with fat testc) Pot dichromate: not so effective, however, it is

easy to handle as it is available in tablet form.

Plat form tests 1. Flavor2. sediment3. Temperature4. Alcohol Precipitation Test 5. Clot On Boiling Test6. Titratable Acidity7. pH 8. Bromothymol Blue Test9. Lactometer reading10.Electrical conductivity11.Freezing point

Other common tests carried out on milk supplies are:• Somatic cell countA large number (more than 500 000 per ml of milk) of somatic cells in the milk indicates that the cows are suffering from udder diseases.

Bacteria count

• Protein content

• Fat content

Composite samples - stored in cool places away from direct sunlight- properly labelled.

Weighing:

~weigh tank – dial reading scale

~ flow meter- in case of tankers

~ weigh bridge in road tanker Testing: Accepted, rejected, doubtful categoriesPreheating: 35-400C- plate or tubular heater may

be used for efficient F / C- flow easy as the viscosity decreases with the increase in temp

Filtration / clarification: Object:

To improve aesthetic quality of milk by removing visible foreign matter which is unsightly and may therefore, cause consumer complaints.

Principle: While filtration removes, suspended foreign particles by the straining process, clarification removes the same by centrifugal sedimentation

Type of filters & clarifiers: 2 types–

a) those that operate with cold milk

b) which operate with warm milk –commonly used

Advantages : Cold---i. No preheating is needed

ii. Less likelihood of soluble matter/ dirt going into the solution

Disadvantages:

i. Flow of milk is slow.

General construction & operation

Filters consist of :

ii. A filter cloth or pad of the desired pore size which can retain the smallest particle.

iii. A frame or support to compress and hold the margins of the cloth or pad, so that milk can pass only through pores.

iii. A perforated metal or other support for the cloth or pad which will not tear under the pressure of milk.

iv. An enclosure to confine both the unfiltered and filtered milks, in a closed system fitted suitably with inlet and outlet connections for sanitary piping

v. A means of distributing the incoming stream of milk so that it does not damage or tear any part of the cloth or pad by vigorous washing.

vi. A design so planned that filter cloths or pads can be changed quickly, and all parts are easily accessible for washing.

where continuous operation is essential, or where large volumes of milk are processed, two or more filters are used so that operations need not be interrupted when it becomes necessary to change the filter cloth. The frequency with which the cloth is changed will depend upon the temp. of the milk, the amount of foreign matter in it, etc.

it is best to use filter clothes only once, a washed cloth, besides being a source of contamination, results in inefficient filtration .

Clarifiers: In general appearance and construction, clarifiers are quite similar to centrifugal cream separators. However, the

The main difference are:

i. In clarifiers, there is 0nly one outlet while in separators there are two-one for cream and the other skim milk.

ii. The discs in the clarifier bowl are smaller in diameter ( so as to provide a large space for the accumulation of slime ) than separators .

iii. The milk distribution holes are at the outer edge of the discs in clarifiers, but near the center in separators

Location of filter/clarifiers in the processing

line:

In some cases, it is the practice to locate the filter in the raw milk line before the milk enters into pasteurization plant; in others the filter is located at a convenient point in the regeneration section where the temp. of milk may be 50-600C.

Location of clarifier

Location Type of clarifier

Between: •Reception and storage tanks •Storage tanks & pasteurizer •Pre-heater and pasteurizer •Regeneration And heating section of HTST •Heating section and holding tube of HTST

ColdColdWarmWarm

Warm

Relative efficiency: clarification removes sediment much more efficiently than filtration; clarifier removes still finer particles that may escape filtration process.

Slime composition(material accumulated): Filter•Suspended foreign particles•Milk fat•Protein•Leucocytes and bacteria

Clarifier•Foreign matter•Milk proteins•Leucocytes•Fragments of secreting cells of udder•Fat• Ash / Calcium phosphate•Bacteria•R.B.Cs

Factors influencing amount of clarifies slime

1. Amount of foreign matter2. Condition of the udder3. Stage of lactation4. Bacterial count5. Acidity of milk6. Clarifying temp.7. Velocity of bowl8. Amount of milk run through bowl9. Length of time bowl in run

Composition of clarifiers slime

Constituents Moist slime (%)Water 67.3TS 32.7

Fat 1.1

Protein 25.9

Ash 3.6

Lactose 2.1

Clarifier slime is similar in composition as that of separator slime

Removal of clarifier does not affect the composition of milk to a significant extent; the loss in solids resulting from clarification is usually 0.01% or less

General Remarks:-

i. Both tend to decrease the depth of the cream layer that will from on milk, and this effect becomes more pronounced as the processing temp. increases.

ii. Neither filtration nor clarification improves keeping quality of milk.

iii. Milk should neither be clarified nor filtered after pasteurization – as post pasteurization contamination may take place.

Bactofugation:• Process of removing 99% of the bacteria

in milk by centrifugal force • Triples the shelf life of market milk.• Two centrifugal clarifiers in a series – the

first operating at high velocity (~20,000 rpm)• Process is supplementary to pasteurization,

for it is necessary to remove the bacteria not removed.

Cooling and storage of raw milk:

Significance

• Milk contains some micro-organisms initially

• if allowed to stand @ ambient temperature these micro-organisms grow rapidly and deteriorate the quality

• Hence milk Cooling is important

Methods:

i. In-can-cooling/can immersion

ii. Tubular iii. PHEiv. Bulk tank coolerStorage: Storage tanks used for the storage of

raw, pasteurized or processed products, often in very large volumes.

Well designed so that CIP is carried out conveniently

Tanks are insulated/ refrigerated so that required temp. is maintained

Agitation should be adequate for uniform mixing but gentle enough to prevent churning and incorporation of air.

Objectives: i. To maintain milk at low temp. so as to

prevent any deterioration in quality peiodr to processing or product manufacture

ii. To facilitate bulking of raw milk supply, which ensures uniform composition.

iii. To allow for uninterrupted operation during processing and packaging

iv. To facilitate standardization of the milk

Types of storage tanks1 Insulated or refrigerated 5-7.5cm insulation - cooled water between the

inner & outer space.

2. ~ Requires more ~ Requires opposite floor space & less head space ~Large vertical tanks are practical – CIP easy .3. dead corners during agitation 4. Built for gravity flow (most common) or

pressure or vacuum operation ( Sometimes used to evacuate the product -

requires special construction)

Horizontal vertica

l

Rectangular ovalcylindrical

Location:1. Located on upper floor Milk pumped from receiving room to floor

above milk flows by gravity preheated filter/ clarifier pasteurization cooler Packaging

2. Milk pumped from storage tank preheater filter/ clarifierPasteurizer may flow by gravity to cooler or pumped to cooler while hot

Parts of storage tank:i. Sight glassii. Light glass & lampiii. Ladder

iv. Manhole

v. Agitator

vi. Outlet valve

vii. Inlet

viii. Air vent

ix. Safety valve

x. Legs

xi. Indicating thermometer

xii. Volume meter

Standardization:

Person square scheme

Problem I: How many parts by weight of 40% cream and 3% milk must be mixed to make milk testing 5% fat.

Problem II: How many kg. each of 28% cream and 3% milk will be required to make 500 kg of a mixture testing 4% fat

Problem III: Prepare 100 kg of toned milk from cow milk- 4% fat and Skim milk-0.1% fat