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Extrusion

Extrusion. Some examples. Licorice Extrusion. Ingredients. Wheat flour Sugar (sucrose, corn syrup) Gelatin or starches Emulsifiers Water Color and flavor (licorice black juice, aniseseed, caramel, berry flavors). Dry ingredients flour, sugar. Sugar syrup Licorice syrup. Metering.

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Extrusion

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  1. Extrusion Some examples

  2. Licorice Extrusion

  3. Ingredients • Wheat flour • Sugar (sucrose, corn syrup) • Gelatin or starches • Emulsifiers • Water • Color and flavor (licorice black juice, aniseseed, caramel, berry flavors)

  4. Dry ingredients flour, sugar Sugar syrup Licorice syrup Metering MIXING COOKING Minor Ingredients COOLING TUNNEL CUTTER SHAPER EXTRUSION Conveyor

  5. Cooking begins Sugar dissolves Starch granules hydrated & gelatinized Pressure increased just prior to die to force product through die Water vented & cooled Colors & flavors added Mixed with candy

  6. Direct Expanded Snack Foods

  7. Ingredients • Cereal grains such as corn, wheat, rice or oats • Water • Oil • Flavor coatings

  8. Usually produced at high shear • Temperatures greater than 100°C • Pressures kept high-water remains liquid at T > 100°C • On exit, moisture flashes from product causing expansion • Loss of water and cooling cause structure to set • Additional drying needed to reduce moisture from 15% to 2-3% • Coated with oil and lfavorings

  9. Breakfast Cereals

  10. Breakfast Cereals • Instant • Direct expanded • Flaked • Gun puffed • Oven puffed • Shredded

  11. In general: mixing, cooking, forming, texturizing, drying http://www.ktron.com

  12. Materials may be precooked • Boiling water cooker • Steam cooker • Adiabatic extrusion-high shear in extruder creates heat • Extrusion- adiabatic plus added heat

  13. Flaked cereals Corn grits and/or wheat are mixed with salt, sugar, malt etc and cooked with steam to form gelatinized mass. Mass broken up into pieces

  14. Cooked grain particles fed to flaking rolls. Particles must deform without fracture.

  15. Doughy particles pass through small gaps between Rollers. Rough surfaces help pull particles through nip, are compressed and flow out from the rollers

  16. Slightly dry product helps form irregularities. On further baking these help form crisp texturized product

  17. In later improvements, cooking and pieces are formed in a screw extruder • Relatively low shear is used and modest heating. Starch is gelatinized but excess shear damages starch. • Die resistance is low to maintain relatively dense strands • Die-face cutting may be unsatisfactory because pieces are too uniform

  18. Dry to 10-24% moisture (tempering) To overflow bins On to flaking rolls Further drying/toasting

  19. Extrusion Puffed Cereals • Superheated gelatinized cereal emerges from extruder die • Moisture flashes and causes puffing • Die determines shape • Typically high-shear extruders

  20. Product puffs as moisture flashes off Superheated dough

  21. Oven puffing Used for crispy rice products Cooked cereal piece exposed to very high temperatures Product expands into a cellular structure With proper moisture in the grain, this is similar to popcorn Need: moisture inside the kernel, starch inside the kernel and a hard shell to contain the pressure

  22. Treated with steam cooking to appropriate moisture level Cooled and dried to 9-11% moisture Flaking roller with wide gap Uniform pieces Fluidized bed dryer T ~ 340°C

  23. High heat raises pressure in grain. Hard shell keeps water from rapidly escaping. Water is superheated. At some point the pressure is sufficient to rupture the kernel. Water rushes out and puffs the product. 9-11% moisture

  24. Extruded pieces may also be oven puffed Often extruded ribbon embossed with waffle grid, fluting, etc to create interesting texture, then cut and oven puffed

  25. Baking or oven puffing

  26. Gun puffing Product heated under pressure in closed vessel Vessel suddenly opened Decompression causes moisture to flash Used in puffed wheat. Product looks more like original grain than with direct oven puffing

  27. Shredded Cereals Extruder cooked and formed pellets fed to shredding machinery One roller embossed with grooves to cause shredding

  28. Product fed into rollers. Pieces are extruded through serrations in one roller, are crushed and merged into a continuous steam Strands are collected on a conveyor

  29. To oven Strands are collected in layers on a conveyor. Crimping rolls form biscuit edges

  30. During baking, the outer layers shrink more causing the biscuit to puff

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