Collection, Chilling ,storage and standardization of milk

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Dairy Processing Operations Dr. Mohammad Ashraf Paul Division of Livestock Products Technology Faculty of Veterinary Sciences & Animal Husbandry SKUAST-K , Alusteng, Ganderbal Kashmir

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Manufacture, packaging and storage of pasteurized Milk

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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: Mercuric chloride or corrosive sublimate: poisonous colored tabs. (bright red)  to prevent the milk from being mistaken for food. Formalin: liquid - convenient to handle- interferes with fat test Pot dichromate: not so effective, however, it is easy to handle as it is available in tablet form.

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Plat form tests Flavor sediment Temperature Alcohol Precipitation Test Clot On Boiling Test Titratable Acidity pH Bromothymol Blue Test Lactometer reading Electrical conductivity Freezing point

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Other common tests carried out on milk supplies are: • Somatic cell count A 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

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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 categories Preheating: 35-40 0 C- plate or tubular heater may be used for efficient F / C- flow easy as the viscosity decreases with the increase in temp

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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

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Advantages : Cold--- i . No preheating is needed ii. Less likelihood of soluble matter/ dirt going into the solution Disadvantages : Flow of milk is slow. General construction & operation Filters consist of : A filter cloth or pad of the desired pore size which can retain the smallest particle. A frame or support to compress and hold the margins of the cloth or pad, so that milk can pass only through pores .

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A perforated metal or other support for the cloth or pad which will not tear under the pressure of milk. An enclosure to confine both the unfiltered and filtered milks, in a closed system fitted suitably with inlet and outlet connections for sanitary piping 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. A design so planned that filter cloths or pads can be changed quickly, and all parts are easily accessible for washing.

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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

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The main difference are: In clarifiers, there is 0nly one outlet while in separators there are two-one for cream and the other skim milk. The discs in the clarifier bowl are smaller in diameter ( so as to provide a large space for the accumulation of slime ) than separators . The milk distribution holes are at the outer edge of the discs in clarifiers, but near the center in separators

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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 50-60 0 C.

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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 Cold Cold Warm Warm Warm

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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

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Factors influencing amount of clarifies slime Amount of foreign matter Condition of the udder Stage of lactation Bacterial count Acidity of milk Clarifying temp. Velocity of bowl Amount of milk run through bowl Length of time bowl in run

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Composition of clarifiers slime Constituents Moist slime (%) Water 67.3 TS 32.7 Fat 1.1 Protein 25.9 Ash 3.6 Lactose 2.1

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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:- 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. Neither filtration nor clarification improves keeping quality of milk.

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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 ) P rocess is supplementary to pasteurization, for it is necessary to remove the bacteria not removed .

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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: In-can-cooling/can immersion

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Tubular PHE Bulk tank cooler Storage: 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.

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Objectives : To maintain milk at low temp. so as to prevent any deterioration in quality peiodr to processing or product manufacture To facilitate bulking of raw milk supply, which ensures uniform composition . To allow for uninterrupted operation during processing and packaging To facilitate standardization of the milk Types of storage tanks 1 Insulated or refrigerated 5-7.5cm insulation - cooled water between the inner & outer space.

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~ Requires more ~ Requires opposite floor space & less head space ~Large vertical tanks are practical – CIP easy . 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 ve rtical Rectangular oval cylindrical

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Location: Located on upper floor Milk pumped from r eceiving room to floor above  milk flows by gravity preheated  filter/ clarifier  pasteurization  cooler  Packaging Milk pumped from storage tank  preheater  filter/ clarifierPasteurizer  may flow by gravity to cooler or pumped to cooler while hot

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Parts of storage tank: Sight glass Light glass & lamp Ladder Manhole Agitator Outlet valve Inlet Air vent Safety valve Legs Indicating thermometer Volume meter

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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

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