OIL AND FAT TECHNOLOGY LECTURES II Handling

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OIL AND FAT TECHNOLOGY LECTURES II
(Handling Storage of Oil-Bearing Materials -
Pretreatments)

• Prof.Dr.Aytaç SAYGIN GÜMÜSKESEN
• Yrd.Doç.Dr.Fahri YEMISÇIOGLU

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Handling Storage of Oil-Bearing Materials

• The handling and storage of oil-bearing materials
  is one of the most important phases of oil seed
  processing.
• The vegetable oils and feed industries are
  dependent for successful operation upon obtaining
  high yields and product of good quality from
  their raw material.
• Excessive biological activity in the seeds,
  either in the field prior to harvesting or
  subsequently during storage, will result in a
  reduction both in the quality and the yield of
  oil and meal.

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• The handling and control of the raw materials for
  the oil seed industry can be primarily
  characterized by the short harvest season, by the
  necessity to move them into protected storage in
  minimum time, and by the required care before
  they can be processed. But they can be treated
  and stored successfully with minimal
  deterioration long enough to allow the processing
  industry to operate throughout the year.

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• Sunflower seed, soybeans, cottonseed, rape seed
  and other oil seeds are subject to damage
  primarily from biological actions, which are
  accelerated by high moisture content, foreign
  material, physical damage, and such adverse
  climatic conditions as frost or rain before
  harvest.

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• Effects accompanying deterioration of seed during
  storage
• Respiration In the presence of oxygen as the
  oxidizing agent, organic food stuffs are oxidized
  to form water and carbon dioxide as the end
  product.
• 
  exothermic reaction
• C6 H12O 6 O2 6 CO2
  6 H2O energy
• Respiration intensity
• Sound seed low m.c. 0.1ml CO2 /g
  seed.day
• Damaged seed high m.c. 5.0ml CO2 /g
  seed.day

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• The respiratory quotient, defined as the ratio of
  carbon dioxide evolved to oxygen absorbed, is an
  indication of the class of substances undergoing
  oxidation.
• In aerobic respiration
• it is theoretically unity if the subctances
  are carbonhydrates,
• but less than unity if they are proteins or
  fats, which are less rich in oxygen.

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• Enzymes
• (a)Lipase. This enzyme catalyzes the reaction
  
• 
  1
• glycerol 3 fatty acid
  triglycerid 3 water
• 
  2
• 1 synthesis t.g
  2 hydrolysis t.g
• (b) Catalase and peroxidase. Both of these
  enzymes react with hydrogen peroxide.Catalase
  will decompose hydrogen peroxide while peroxidase
  utilizes it for further oxidation.
• 2 hydrogen peroxide
  2 water oxygen

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• Influence of moisture content
• Oil seeds are best stored at low moistures where
  respirotary and enzymic activities, germination
  and mold growth are inhibited. This maximum
  acceptable moisture level is known as critical
  moisture level (CML) .
• The moisture content of the nonoil portion of the
  seed rather than the whole seed is the important
  factor in oil seed deterioration.
• CML is relatively high for seeds of low oil
  content.
• CML is relatively low for seeds of high oil
  content.

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• Safe humidity for starchy food grains
  
• 16
• Oil content of soybean . 22
• Non-oily part of soybean . 78
• Critical moisture level 0.78 x 16 12.5

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• CML of oil seeds
• Hulls () Fat ()
  CML()
• Rape seed 14 40
  7.0
• Palm kernel - 52
  8.0
• Sunflower seed 28 43
  8.5
• Cottonseed 48 18
  10.0
• Soya beans 8 20
  12.0

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• Influence of temperature.
• In the case of soya beans and similar oilseeds
  where deterioration appears to b primarily a
  result of the growth of microflora, the storage
  temperature does not appear to be a major factor.
  However, temperature is very important factor in
  storage of cotton seed. The respiration of cotton
  seed is markedly temperature-dependent. The
  insulating effect of linters on cottonseed
  contributes to the peculiar tendency of this seed
  to heat in storage.
• It is because of the undesirable effect of high
  temperature that most seed houses are equipped
  with aeration ducts and large ventilating blowers
  to cool the seed.

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• Storage method
• Warehouses (Muskogee type seed houses)
• Bulk storage in warehouses on flat floors has the
  advantage of easy control of oil seeds, like
  cottonseeds, sunflower seed, corn germ, further
  meals etc. To prevent self heating or
  autocombustion of the seeds, recycling by
  horizantal and vertical transportation means is
  recomended.

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• Muskogee type seed store

Oil seed
Belt conveyer
Oil seed bulk
Section through storage building
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• Preparation of Oil-bearing Materials
• Cleaning foreign materials
• Delinting for cottonseed lints
• Dehulling hulls
• Flaking
• Cooking moist

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• CLEANING
• Cleaning is important not only to ensure the
  good quality of the final products oil and meal
  but also to avoid premature wear of the
  preparation equipment.
• The removal of foreign materials from oil seeds
  is done by cleaning machines working on
  mechanical, pneumatic and magnetic principles.
• Cleaning machines
• Screens
• Aspirators
• Magnets
• Shape sorters

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• SCREENS
• Screening is the seperation of mixtures of
  different sizes into fractions the portion
  staying behind being oversize, the portion
  passing through being undersize.
• Rotating screens
• Vibrating screens

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Drum screen
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• Vibrating screen

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• ASPIRATORS
• In order to seperate impurities or fractions of
  different density, pneumatic means, like air
  nozzles and aspirators are used.

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• MAGNETS
• Permenant or electromagnets enclosed in a
  rotating aluminium drum are used in feeders to
  distribute the material uniformly over the whole
  active width of the drum.The magnetic material
  collected is removed by a blade on the
  ono-magnetized half and, in this way, it remains
  seperated even in the case of power failure

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• Self cleaning rotary magnets

aspirator
Seed inlet
Rotating drum
Stationary magnet
Iron parts
Cleaned seed
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• DELINTING
• (for cottonseed)

cottonseed
lints (8-12)
Hull (40-45)
Delinting process to remove the
remaining lint from cotton seed Aims of
delinting 1)increase oil yield 2)obtain first-
and second- cut linters
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Delinter
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• Cutting operation

cottonseed
seed feeder
cut lints
saws
delinted seed
brush
Saw teeth
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• Method of delinting cotton seed comprises the
  steps of passing the cotton seed through a saw
  delinter to remove a substantial portion of the
  lint, preferably at least 40, and thereafter
  passing the partially delinted seed through a
  brush delinter to remove substantially all of the
  remaining lint.

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• Cottonseed Delinting Equipment

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DEHULLING

• Dehulling is a process of removing hulls from the
  oilseeds for obtaining high quality edible oil by
  the processing of kernels. This reduces fibrous
  content of the meal and increases the
  marketability as stock feed. About 99 of oil is
  stored naturally in kernels and the hulls contain
  not more than 1 oil.
• If the hulls are not removed they reduce the
  total yield of oil by absorbing or retaining oil
  in the pressed cake. In addition to this the wax
  and colouring matters present in the hulls get
  mixed with the expressed edible oil. This
  necessitated the refining process, and therefore,
  increase the production cost of edible oil.
• Moreover, processing oilseeds without dehulling
  reduces the capacity of the extraction equipment
  in addition to more repair and maintenance
  charges.

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• Approximate Hulls and Kernels Percentage in
  different seeds
• 
  oil
• kernel hull
  whole kernel husk
• Cottonseed 55
  45 19 30
  1-2
• Rapeseed 82
  18 42 -
  -
• Sunflower 75
  25 22-36
  36-55 1-2
• Soybean 93
  7 18
  19 0.6

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• HULLER
• The hulling machines used for the decortication
  of medium-sized oil seeds with a flexible seed
  coat, such as cottonseed, sunflower seed and
  peanuts, are of two principle types
• Bar hullers
• Disc hullers

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Bar huller

• The rotating member of a bar huller is a cylinder
  equipped on its outer surface with a number of
  slightly projecting, longitudinally placed,
  sharply ground, square-edged knives or
  bars.Opposed to the cylinder over an area
  corresponding to about one-third of its surface
  is a concave member provided with similar
  projecting bars.The seed are fed between the
  rotating cylinder and the concave member, and the
  hulls are siplitted as the seeds are caught
  between the opposed cutting edges.The clearence
  between the cutting edges may be adjusted for
  seed of different sizes.

seed
Bars (concave surface 1/3)
Square-edged knives
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Disc huller

• The disc huller consists of vertically mounted
  discs, one of which is stationary and the other
  rotating.The seeds are fed to the center of the
  discs and are discharged at their periphery by
  centrifigal force.

Adjust according to seed size
Rotating disc
seeds
Stationary disc
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• The moisture content of seed effects the
  efficiency of dehulling operation.
• Wet seeds are difficult to split cleanly and may
  clog the huller.
• If the seeds are very dry, the kernels may
  disintegrate excessively.

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• Universal dehulling
• Seed
• First huller (coars huller)
• Hull beater
• Kernel Hull Uncut seed
• Second huller
• Hull beater
• Kernel Hull Uncutseed

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• FLAKING
• The extraction of oil from oil seeds, either by
  mechanical extraction or solvent extraction, is
  facilitated by reduction of the seed to small
  particles.
• Flaking is achieved on corrugated roll stands.
  Cracking mills with one or two pairs of rolls are
  used.
• Hammer mills are used for certain raw
• materials like palm kernel.

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• Crushing rolls
• A roll assembly commonly used for the reduction
  of oil seeds consists of a series of five rolls
  placed one above the other. The seed is
  introduced by a feeding mechanism between the two
  top rolls.Seed travels from the top to the bottom
  of the system, hence it is rolled four times.

Corrugated roll
Speed 0.05 m/sec knife Smooth rolls
kernel
flake
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Crushing rolls
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• COOKING HEAT TREATMENT
• Effects of cooking process on the physical and
  chemical properties of oil seeds
• The oil droplets in the oil seed are
  ultramicroscopic in size. Because of the increase
  in temperature they come together and form larger
  droplets to flow from the seed.
• Heating of the seeds causes the protein to
  denature and as a consequence, the emulsion to
  break and the oil to seperate from the solid
  surface of the seed.

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• Cooking of the seed gives the seed mass the
  proper plasticity for efficient pressing.
• Insolubulization of phosphatides and other
  impurities.
• Destruction of molds and bacteria.
• Increase of the fludility of the oil through
  increase in temperature.
• In the case of cottonseed, detoxification of
  gossypol or related substances.

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• A four high stack cooker
• The cooking of oil seeds is usually carried out
  in stack cookers.These consist of a series of
  four to eight closed, cylindirical kettles. Each
  kettle is normally jacketed for steam heating on
  the bottom and is equipped with a sweep-type
  stirrer mounted close to the bottom.There is an
  automatically operated gate in the bottom of all
  kettles. The top kettle may be provided with
  spray jets for the addition of moisture to the
  seed, and each of the lower kettles is provided
  with an exhaust pipe with natural or forced draft
  for the removal of moisture, thus it is possible
  to control moisture content of the cooked seed.

Seed flakes
Direct steam
T (0C)
2-3.5 m diameter 50-70 cm high
Sweeper-type stirrer
Exhaust pipe
gates
Cooked flakes
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STACK COOKER
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• Cooking of cottonseed
• Detoxification
• Before cooking, moisture 12.
• Cooking time 90 mn
• Final cooking temperature 115 0C
• Final moisture 3

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Conventional preparation system