Effects of Operating Conditions on the Cellular Structure and the Thermal Properties of Extruded Foams Made From Corn

Abstract

The characteristics of a corn extrudate generally appear similar to commercial plastic foam cushioning materials. If extruded foams from whole yellow dent corn are used for loose fill cushioning material, low cost will be realized. In addition, this extruded foam is biodegradable and might even be recoverable as animal feed or as an ethanol feedstock. It could also be spread on farm fields as a soil amendment. Extrusion technology has been applied in cornstarch processing for many years. Different categories of extruders have been developed to give various advantages and disadvantages as used for production. The low-moisture (low-cost) extruder cooker is a good choice for producing low cost expanded corn for packaging use. The objective of this study is to focus on the feed compositions and screw configurations affecting the cellular structure and the specific heat of extruded foams and to evaluate corn/ PVA extrudates as packaging material.

Experimental results indicated that:

1. The size of air cells became smaller and more uniform, and the air cell wall became thinner with the increase in screw pitch and screw speed. Moreover, using the food grade corn grits also made the size of cells smaller and more uniform.

2. Treatments 5 and 22 had the highest specific heats. For all treatments, the specific heat increased linearly as the temperature increased.

3. The extrudates from Treatments 5 and 22 have potential applications as thermal insulation applications for their high specific heat values.

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References

1. Altieri, P.A. and Lacourse, N.L. (1990). Starch-based Protective Loose Fills Material , In: Proceedings, Corn Utilization Conference III, National Corn Growers Association, St. Louis, MO.

2. Andreas, M.L. (1989). The Polyclean Process . Iowa Corn Promotion Board Corn-Based Degradable Plastics Symposium, Des Moines, IA.

3. Barenberg, S.A., Brash, J.L., Narayan, R. and Redpath, A.E. (1990). Degradable Materials: Perspectives, Issues, and Opportunities, CRC Press .

4. Bastioli, C., Bellotti, V., Del Giudice, L., Lombi, R. and Rallis, A. (1991). Expanded Articles of Biodegradable Plastic Materials and a Method of their Production, PCT Int. Appl. WO 91 02023.

5. Bhatnagar, S. and Hanna, M.A. (1995). Physical, Mechanical and Thermal Properties of Starch-Based Plastic Foams , Transaction of the ASAE, 38(2): 567–571 .

6. Chakrabarti, S.M. and Johnson, W.H. (1972). Specific Heat of Flue Cured Tobacco by Differential Scanning Calorimetry , Transactions of ASAE, 15(5): 928–931 .

(b) Chinnaswamy, R. and Hanna, M.A. (1991). Extrusion Grafting Starch onto Vinylic Polymers , Starch, 43: 396–402 .

8. Dziezak, J.D. (1989). Single- and twin-screw Extruders in Food Processing , Food Technology, 43(4): 164–174 .

9. George, E.R. (1994). Thermoplastic Starch Blends with Polyvinyl Alcohol: Processability, Physical Properties, and Biodegradability.

10.

10. Frey, H.E. and Star, S. (1988). Chemical Economics Handbook, p. 580-580, Menlow Park, SRI International, Calif.

11.

11. Harper, J.M. (1981). Extrusion of Foods, Vols. 1 and 2. CRC Press Inc., Boca Raton, FL, USA .

12.

12. Hayter, A.C., Smith, A.C. and Richmond, P. (1986). The Physical Properties of Extruded Food Foams , J. Mater. Sci., 21(10): 3729–3736 .

13.

13. Hutchinson, R.J., Siodlak, G.D.E., and Smith, A.C. (1987). Influence of Processing Variables on the Mechanical Properties of Extruded Maize , J. Mater. Sci., 22(11): 3956–3962 .

14.

14. Lacourse, N.L. and Altieri, P.A. (1989). Biodegradable Packaging Material and the Method of Preparation, U.S. Patent No. 4,863,655.

15.

15. Lourdin, D., Del Valle, G. and Colonna, P. (1995). Influence of Amylose Content on Starch-films and Foams , Carbohydr. Polym., 27(4): 261–270 .

16.

16. Miller, R.C. (1992). Effects of Tapered Screw Elements in Twin-screw Cooking Extrusion, In: Food Extrusion Science and Technology, Marcel Dekker, Inc., New York .

17.

17. Mohsenin, N.N. (1986). Physical Properties of Plant and Animal Materials: Vol. 1, Structure, Physical Characteristics, and Mechanical Properties. Gordon & Breach Science Publishers, Inc., New York, N.Y.

18.

18. Moore, D., Sanei, A., Van Hecke, E., and Bouvier, J. M. (1990). Effect of Ingredients on Physical/structural Properties of Extrudates , J. Food Sci., 55(5): 1383–1402 .

19.

19. Narayan, R.A. (1994). Biodegradable Plastics.

20.

20. Neumann, P.E., and Seib, P.A. (1993). Starch-based Biodegradable Packaging Filler and Method of Preparing Same, U.S. Patent No. 5,165,383.

21.

21. Peng, J., Huff, H.E. and Hsieh, F. (1994). An RTD Determination Method for Extrusion Cooking , J. Food Process Pres., 18(4): 263–277 .

22.

22. Roger, E.J. (1989). Degradable Plastics for the 90s , Iowa Corn Promotion Board Corn-Based Degradable Plastics Symposium, Des Moines, IA.

23.

23. Roper, H. and Vilvoorde, K.H. (1990). The Role of Starch in Biodegradable Thermoplastic Materials , Starch, 42: 123–130 .

24.

24. Sachetto, J.P., Silbiger J. and Lentz D.J. (1991). Polymer Base Blend Compositions Containing Destructurized Starch, Eur. Pat. Appl. EP 409, 781.

25.

25. Tsai, K. (1991). Evaluation of Extruded Corn as a Packing Material, MS, Thesis, U. of Illinois-Urbana, Urbana, IL, USA.