bab 1_preparation of raw material part a

5/26/2018 Bab 1_preparation of Raw Material Part A

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UNIT OPERATION IN FOOD PROCESSING

PREPARATION OF RAWMATERIALS BEFORE PROCESSING

PART A

(CLEANING PROCESS)

Prepared by: Pn Rosliza Bt. Mohd Radzali


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Objectives

Explain the steps of preparation of raw materials beforeprocessing.

Define cleaning and explain the purposes of cleaning.

Identify the types of contaminants in raw materials.

Explain and differentiates of wet and dry cleaning

methods.

Explain and identify the related equipment with respectto wet and dry cleaning methods.


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Pre-testState whether these statement are TrueorFalse

1. The present of contaminant such as fungal and yeast can reducethe quality of food product.

2. Filtration and brushing are types of wet cleaning method.

3. Soaking is a wet cleaning method.

4. Aspiration is a dry cleaning method.

5. Wet cleaning have low cost production because it produce loweffluent.

6. Spray drum washer is an equipment that used in wet cleaningmethod.


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Fill in the blank this statement with the right answer

1. __________ use detergent and water to remove soil anddust from foods.

2. __________ use principles of different buoyancy to

remove debris from the foods.3. __________ is one of contaminant type of chemical

elements.

4. __________ can detect metal particles.

Wet cleaning

aspiration

pesticides

Magneticcleaning

Pre-test


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Cleaning

Cleaning Of Raw Material-Cleaning is the unit operation in which contaminantmaterials are removed from the food and separated toleave surface of the food in a suitable condition for

further processing.

Purpose Of Cleaning

- to take out the contaminant which is can harmful the

human health.- Control chemical and biochemical reaction of the

microbial content can reduce the quality of foodproduct.


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Types Of Contaminant In Raw Material

Elements Examples

Metals Ferrous and non ferrous metals, bolts, filings

Minerals Soil, stone, grease, metal particles and engine

oilPlants Leaves, weed seed,pods and skin,

Animals Hair, bone,blood, egg, insect, larvae and part ofanimal body

Chemical Fertilizers, pesticides and herbicides

Microbial products Colours, flavours, toxin

Microbial cells fungal growth, yeasts


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Method of Cleaning

Removing soil from root ordust and pesticide residuesfrom soft fruits or vegetables

Use clean warm water /different combination ofdetergent or sterilants

Will produces large volume ofeffluent/ high dissolved andsuspended solid in water

WETCLEANING

For smaller product, greater

mechanical strength andprocess a lower moisturecontent

Use air, magnetism or otherphysical method

Will cause of dust, create badhealth and recontaminates theproduct

DRYCLEANING


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WET CLEANING METHOD


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WET CLEANING METHOD

(SOAKING)


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Soaking

- It is the simplest cleaning method.

- As a preliminary stage in the cleaning of rootvegetables other foods which are heavily contaminated.

- Adhering soilis softened and some is removed,together with stone, sands and other abrasivematerialswhich would damage the machinery used in

the later stages of cleaning.

- Soak tanksare made of metal, smooth concrete orother materials of construction suitable for regular

cleaning and disinfection.


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Absorbent materials such as wood should not be used.

The efficiency of soaking is improved:

i) by moving the water relative to the product bymeans of caged propeller-stirrer built into the tank

ii) by moving the product relative to the water

either by means of slow moving paddles or byfeeding the raw material into a horizontalperforated drum which rotates whilst partiallysubmerged in the soak tank. Can cause damage to

delicate food.

Soaking


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Agitation may also be produced by sparging

compressed air through tank for delicate material,eg; strawbery and asparagus, spinach or celery whichtraps dirt internally

Warm water improves the efficiency but the rate ofspoilage of foods may be increased.

Care is necessary, however, in the selection and use ofsuch agent, since the appearance and texture of thefood may be affected.

eg; softening affects of sodium hexametaphospate onpeas and toughening agent of some metal ions on peas

and peaches destined for canning.

Soaking


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Frequently, soak tanks are supplied with lightlycontaminated water from subsequent washing stages.

In this way, water economies are effected and effluentvolume are reduced.

With such counter-current re-use of water it becomeimportant to exercise careful microbiological controland for regular changing of soak water to becarriedout.

Usually, chlorination method is used to decreasebacterial loading in soak tank water but it high COD

rapidly remove active chlorine so that highconcentration of this is necessary.

Soaking


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WET CLEANING METHOD

(SPRAY WASHING)


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Spray Drum Washer

The spray drum washer consists of a reel constructed

of metal slats or rods, spaced so as to retain the foodwhilst allowing debris to be washing through.

The drum, rotates slowly and inclined to the

horizontal.

The speed of rotation and angle of inclination controlboth movement of the food within the drum and the

duration of the washing cycle.

The washer is equipped with a central spray rod whichis fitted with jets or slots through which water is

sprayed, however may cause damage to some foods.


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Spray Drum Washer


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Spray Belt Washers

This type of spray washer is simply aconveyor which carries the food beneathbanks of water sprays.

With roughly spherical foods such asapples, contact is improved by using

roller conveyors which cause the fruit tospin beneath the spray


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Spray Belt Washers


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WET CLEANING METHOD

(FLOATATION WASHING)


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Floatation Washing

This method depends on the difference in buoyancybetween the desired and undesired parts of the food tobe cleaned.

Thus bruised or rotten apples, which sink in water, maybe removed by fluming the fruit into a tank andcollecting the overflow of sound fruit.

The floatation washer effectively removes stones, dirtand plant debris from peas, beans, dried fruits andsimilar materials at rates of 3 tones/h.

Water flow rates in the range of 200-500 l/min arenecessary. Water recirculation is necessary.


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Froth Floatation

Depends on the differential wetting of the food and its

contaminants, is an elaboration of flotation procedure.

This method is freeing peas from weed seeds which arenot effectively remove by normal flotation methods.

Contaminated peas immersed in a dilute, mineral oildetergent emulsion through which air is blown.

The contaminants float on foam and removed.

The peas goes to final wash to remove emulsioncontaminant.


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Floatation Washing


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WET CLEANING METHOD

(ULTRA-SONIC CLEANING)


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Ultra-sonic cleaning

Sound waves of frequencies above 16 kHz are used.

Insonation of a fluid with ultrasonic waves offrequencies in the range of 20-100 kHz produces arapidly alternating pressure in the path of the wavesand this leads to the rapid formation and collapes of

bubbles in the fluid. These effect, called the cavitation and decavitation,

result in the release of energy causing a violentagitation of particles immersed in fluid.

This phenomenon is utilized to effect the loosening ofadherent dirt.

E.g: grit on vegetables, grease and wax on fruits anddirt on eggs. The contaminants after loosening are

removed by other cleaning methods.


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WET CLEANING METHOD

(DEWATERING)


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Dewatering

Wet cleaning results in a cleaned product that may

have some excess water adhering to it.

Dewatering may effected by passing the food overvibratory screens or specially designed rotary screen.

In the case of cleaned peas for freezing, or washedwheat for milling, centrifuges may be used.

Occasionally it may be necessary to resort to dryingprocedures, as in the case of cereals or fruits, which areto be stored or sold as fresh.


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DRY CLEANING METHOD


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Dry Cleaning Method

Method Aspiration cleaning, Magnetic cleaning , Filtration

cleaning, Abrasion cleaning, Electrostatic cleaning,Brushing, Radio isotope separator and X-Rayseparator

The methodchosen dependon:

1. Raw material properties.

2. contaminant elements to be removed.3. conditions required for surface cleaning.

Advantages 1. Low cost

2. Easy to handle

3. Cleaning surface in dry condition

Disadvantages 1. contaminants likely to occur again

2. Highdust content (control of dust is important,install special control system to detect anyexplosion.


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DRY CLEANING METHOD

(SCREENING)


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Screening

Screen are primarily size separatorsor sorting machines but may used ascleaning equipment for removing

contaminant of different size fromthat of the raw materials.


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Rotary Drum Screen

Description Usually known as trommel, reels and and centrifugescreen.it is a continuous unit that is widely used in food industry.

Function To remove weed-seeds, grit and small stones from cereals.Cleaning of flour, salt or sugar from which strings and bag-hairs.

Principle Filter arranged so that the clean material separated on thebasis of the size either oversize or undersize.

Eg; removal of small stone and sand from wheat.

Advantages 1. Have high capacity2. Maintain and operate

Disadvantages 1. Difficult to clean unless design properly.2. contaminant occurred again except with careful design.3. Expensive to install


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Flat Bed Screen

Description Consist of one or more flat screen decks fixed together in adust-proof casing, the assembly being shaken by a varietyof devices.

Advantages Suitable for cleaning delicate items such as flour andground spices powder.

Disadvantages Must be frequently cleaned to remove oversizecontaminant which may pulverized due to abrasion andspread contamination of the raw material.


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DRY CLEANING METHOD

(Abrasion Cleaning)


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Abrasion Cleaning

Abrasion between food particles or betweenfood and moving part of cleaning machinery isused to loosen and remove adhering materials.

Trommels, tumblers, vibrators and abrasivediscs and rotating brushes are used for thispurposes.

Dust removal to prevent recontamination andexplosion is essential in this type of cleaning.


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DRY CLEANING METHOD

(ASPIRATION CLEANING)


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Aspiration Cleaning

Aspiration finds wide application in removing debris differing inbuoyancy from the desired material.

In principle, the material to be cleaned is fed into a stream of airat controlled velocity when separation into two or more stream

(eg:light, middle and heavy ) is affected.

This is suitable for two or three stream separation of cereals, nutsand similar foods.

Use to clean onions, melons, eggs and other foods which are notamenable to wet. The soil is loosened by abrasion, using brushingor contacting with rotating rubber fingers and the debris is thenremoved, selectively by air stream.


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Aspiration Cleaning

Capable of very precise adjustment.

Can be used to remove particles from flour and even todiscriminate the protein and starch fragments in the

production of protein enriched flour.

Used large quantities of low pressure air and ,henceconsume much energy.

Careful dust control is necessary for safety and healthreason to prevent the spread of contaminants.


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Aspiration Cleaning


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The sortex air separator

A

The sortex air separatorB

Aspiration Cleaning


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Aspiration Cleaning


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DRY CLEANING METHOD

(MAGNETIC CLEANING)


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Magnetic Cleaning

Cascade the contaminated product stream over one ormore magnets which are usually located in theconveyor trunking.

Magnetic separators may also take the form of rotatingor stationary magnetic drums, magnetized belts,magnets located over belts carrying the food orstaggered magnetized grids through which the foodpassed.

Both permanent magnets and electromagnetsare used.

It is more suitable for foodstuff cleaning, the adheringmetallic particles being removes easily by switching offthe current.


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Electromagnets are more expensive thanpermanent magnets and subject to power

failure.

It may be followed by an electronic metal-

detector which monitors the products for bothferrous and non-ferrous particles.

Electronic detectors can also detect certainother inclusion such as clinker, some stones,carbonized grease and metal impregnatedgrease.


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DRY CLEANING METHOD

(Miscellaneous Dry-Cleaning Principles)


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ElectrostaticCleaning

The differences of electrostatic charging which is

material under controlled humidity condition, chargeparticles being removed by oppositely-charged orearthed rollers, grids.

This procedure is used in dust extraction and in otherprocesses such as the cleaning of tea.

In the application: tea-fanning are cleaned of dust and

stalks by flowing the material over a roller charged to apotential of 5-20 kV and rotating at 70-350 rev/min.

The tea adjusted to moisture content of 3 4% andthe separated matter is removed from the roller,

continuously by rotating brushes.


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Radio-isotopes

Use low energy gamma radiation to separate of clods ofearth and stones.

The differences are sensed by a Geiger-Muller detector,

the signals from this being used to actuate amechanism which rejects the rubbish.

The prototype machine is reported to remove 90% of

the contaminants.


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X-Ray Separation

X-Ray separation of stones, glass and metal fragments in food

such as confectionary is well established.

The food is conveyed through an X-Ray scanner and the image isviewed on a fluorescent screen by an operator who stop theconveyor when an inclusion is seen.

Mechanization of this process has proved difficult but a machinecapable of detecting inclusions in pickles has been reported.

In this machine, a difference in contrast between the optical andX-ray images of jars of pickles is used to generate an electricalsignal which triggers an injection device.


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Thank you

bab 1_preparation of raw material part a

Documents

preparation of raw material

wet cleaning method5262018

types of wet cleaning

cleaning of rootvegetables

purposes of cleaning

purpose of cleaning

simplest cleaning method

dry cleaning methods