COOKINGCooking is excellent prepara

COOKING
Cooking is excellent preparation for most oilseeds and necessary for those too soft to withstand the pressure generated within a screw press
EFFECTS OF COOKING PROCESS ON THE PHYSICAL AND CHEMICAL PROPERTIES OF OIL SEEDS:
1. 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
2. Heating of the seeds causes the protein to denature and as a consequence, the emulsion to break and the oil to separate from the solid surface of the seed
3. Cooking of the seed gives the seed mass the proper plasticity for efficient pressing
4. Insolubulization of phosphatides and other impurities
5. Destruction of molds and bacteria
6. Increase of the fluidity of the oil through increase in temperature
7. In the case of cottonseed, detoxification of gossypol or related substances
8. Cooking also ruptures oil cells, thereby releasing the oil into a more fluid state
9. Cooking inactives troublesome enzymes that adversely affect oil and meal quality
EXTRUSION PREPARATION
Cooking by extrusion
DETOXIFICATION
Several toxin are troublesome in oil seeds;
Cotton seed contain three toxins, CB-1A being the most difficult to inactive
Seed like peanuts, cotton seed that are permitted to mold can contain alfatoxin, a metabolic waste product of several Aspergili molds
EXTRACTION
1. Rendering
Wetprocess, Dry process, Slurry, Digestive process
2. Mechanical Extraction
Screw press, Hydraulic press (full pressing, pre-pressing, cold pressing)
3. Solvent Extraction
Continuous process, Batch process
Processing Options:
Oilseeds can be processed using one or more of a number of stages, depending on the nature of the seed, the capacity of the plant and the intended market
Seeds which contain relatively little oil < 20 % (soybeans), are almost processed by solvent extraction . (residual oil content in meal 0,5-1%)
Seeds with a higher oil content are processed in two stages. A-pre press to reduce the oil content to around 18-20% and the press cake is then treated with hexane to produce a meal with 0,7-1,5% oil
Cold pressing may also be used when a particular oil quality is required. However extraction rates are generally significantly poorer than with conventional processing
RENDERING OF ANIMAL MATERIALS
Fatty anima tissues, free from muscle and bone, usually contain 70-90% fat, the balance being water and connective tissue
Connective tissue is high in protein, hence the dried solids from rendering (tankage), like the solids in the raw material is small
- low temperature, done at temp below the boiling point of water
- high temp, or steam rendering, done under pressure in closed vessels
DRY RENDERING
DR is a simler method of fat extraction. It differs from wet rendering in that the explusion of fat is accompanied by dehydration of the fat and solid residue so that both are of low moisture at the end of the operation
SLURRY RENDERING
The raw material is coarsely ground, mixed with finished fat, and is then fine ground to form a pumpable slurry of approximately 68% fat, 10% solid, and 22% moisture.
The slurry is pumped through an evaporator under vacuum for moisture removal, then through a centrifuge for fat removal
The solid residue at approximately 35% fat is pressed to 10% fat in screw presses
DIGESTIVE RENDERING
Considerable attention has been given to wet rendering of animal fats with the assistance of added chemicals or enzymes that promote the separation of fat by hydrolyzing and dissolving the connective tissue.
Best result were obtained whwn the fat was digested at 85-95 C for 45 min to 1 h with a 1,75% sodium hydroxide. Solution . After digestion, the fat was seperated from the aqueous liquid (which contained a small amount of undigested solids) by cntrifuging. The fat was thn washed, first with 2-5 % salt solution, and then with water.
The process for the recovery of lard or other animal fat involves digestion of the fatty stock with a proteolytic enzyme of vegetable origin, for example , 0,005-0,020% papain at a pH of 6,0-7,5, followed by heating to 60-85°C to separate the fat.