Extruded Foods
Cheese or Cocoa Puffs
Periods: 3
Period 1: Planning
Period 2: Manufacture
Period 3: Product evaluation
Objectives:
1. To familiarize the student with the principles of food extrusion.
2. To identify what foods can be extruded and why and how.
3. To familiarize the student with the operation of extruders.
4. To enable the student to prepare mixes and run the food ingredients through the extruder.
5. To analyze extruded foods for texture, consistency, and composition.
Background:
Extrusion is defined as "shaping by force through a specially designed opening often after previous heating of the material." Extrusion is the continuous forming of plastic or soft materials through a die. Several types of extruders include ram or piston types and screw or worm types (Harper, 1981).
Cooking extrusion combines the heating of food products with the act of extrusion to create a cooked and shaped food product and is a process in which moistened, starchy, proteinaceous foods are cooked and worked into a viscous, plastic-like dough. The results of cooking the food ingredients during extrusion are:
1 ) gelatinization of starch
2) denaturation of protein
3) inactivation of raw food enzymes
4) destruction of naturally occurring toxic substances
5) diminishing of microbial counts in the final product.
Upon discharge through the die, the hot, plastic extrudate expands rapidly with loss of moisture and heat because of sudden decrease in pressure. After expansion cooling, and drying, the extruded product develops a rigid structure and maintains a porous texture.
Advantages of food extrusion are versatility, high productivity, low cost, product shapes, high product quality, energy efficiency, production of new foods, and no effluents or waste.
Procedure:
The following is an example of cheese puffs. The formulation may be modified for cocoa puffs.
1. Mixing – The following formulas may be used to prepare mixes to be run through the extruder.
Startup Mix
Corn flour 6 Ibs. 5 oz.
Wheat flour 1 Ib. 80z.
Sugar ----- 12 oz.
Salt ----- 1 oz.
Water 1 Ib. 8 oz.
Cereal Mix
Corn flour 6 Ibs. 13 oz.
Wheat flour 1 Ib. 80z.
Sugar ----- 12 oz.
Salt ----- 1 oz.
Water 1 Ib. -----
Snack Food Mix
Corn flour 6 Ibs. 7 oz.
Rice flour 2 Ibs. 50z.
Salt ----- l/~oz
Water 1 Ib. 50z.
Hydrogenated oil ----- 3 oz.
2. Extrusion - Under the direction of the laboratory manager, carefully start the extruder and auxiliary equipment.
CAUTION: THERE ARE EXTREMELY DANGEROUS MOVING PARTS ASSOCIATED WITH THE EXTRUDER. HEED ALL WARNING SIGNS.
a. Add mix to extruder and adjust heating zones as instructed.
b. Collect samples of extruded product and process further as instructed.
c. Make adjustments in formulations and processing to test your variables.
d. Determine the expansion ratio of the extruded food according to the following formula:
EXPANSION RATIO = DIAMETER OF EXTRUDATE--DIAMETER OF DIE.
3. Flavor extruded material according to directions.
Analysis and Organoleptic Evaluation:
1. Determine the total solids and moisture content of each extrudate.
2. Observe the structure of the extruded material under the microscope.
References:
Harper, J. M. 1981. Extrusion of Food. CRC Press, Boca Raton, FL
Riaz, Mian N 2000 Extruders in Food Applications. Technomic Publ. Co., Lancaster P. A.
Ruseo, E. W. & Rooney, L R. (2001) Snack Food Processing. Technomic Publ. Co., Lancaster PA