Journal of the American Oil Chemists’ Society

, Volume 76, Issue 9, pp 1101–1108 | Cite as

Mechanical and physical properties of protein-starch based plastics produced by extrusion and injection molding

Article

Abstract

Processing conditions, ingredient ratio, and moisture content were optimized for making soy protein/starch based plastics using a twin-screw extruder and an injection molding machine. A metering pump and a high speed mixer were used for ingredient mixing. The optimal processing temperature for injection molding was 130°C, and the moisture content of extruded pellets was 10–14%. Processing effects were investigated by measuring the tensile properties and water resistance of specimens. Reduction of water and glycerol in mixtures increased the barrel pressure of the extruder. Mold release was improved by incorporating 0.25 parts tallow per 100 parts of solid material (soy protein and starch). The water absorption of the specimens was reduced by adding acids to adjust the pH to the isoelectric point of soy proteins (pH 4.5). Effects of storage at different relative humidities were studied. The processibility of pellets was stable after a 4-wk-storage period, despite some moisture loss. Injection-molded specimens, after being stored for up to 6 mon at dry conditions [50 and 11% relative humidity (RH)] at room temperature and for 4 wk in a 50°C oven, showed no surface crack. However, humid (93% RH) storage at room temperature promoted fungal growth after storage for 3 mon, indicating that preservatives such as potassium sorbate and propionic acid were needed.

Key Words

Extrusion glycerol injection molding mold releasing proteins starches tallow tensile strength water absorption 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Kinsella, J.E., S. Damodaran, and B. German, Physicochemical and Functional Properties of Oilseed Proteins with Emphasis on Soy Proteins, in New Protein Foods, edited by A.M. Altchul and H.L. Wilcke, Academic Press, Inc., New York, 1985, Vol. 5, pp. 107–179.Google Scholar
  2. 2.
    Burnett, R.S., Soy Protein Industrial Products, in Soybeans and Soybean Products, Vol. II, edited by R.S. Markley, Interscience Publishers, Inc., New York, 1951, pp. 1006–1053.Google Scholar
  3. 3.
    Schwalbe, H.C., Isolated Soy Proteins from a User’s Viewpoint, in Synthetic and Protein Adhesives for Paper Coating, Technical Association of the Pulp and Paper Industry (TAPPI) Monograph Series 22, 1961, pp. 167–205.Google Scholar
  4. 4.
    Lambuth, A.L., Protein Adhesives for Wood, in Wood Adhesives—Chemistry and Technology, edited by A.P. Pizzi, Marcel Dekker, Inc., New York, 1989, Vol. 2, pp. 1–29.Google Scholar
  5. 5.
    Myers, D.J., Present and Potential Uses of Soy Proteins in Nonfood Industrial Applications, in Proceedings of The World Conference on Oilseed Technology and Utilization, edited by T.H. Applewhite, AOCS Press, Champaign, 1992, pp. 278–285.Google Scholar
  6. 6.
    Myers, D.J., Industrial Applications for Soy Protein and Potential for Increased Utilization, Cereal Foods World 38:35–55 (1993).Google Scholar
  7. 7.
    Mauro, D.J., An Update on Starch, Ibid.:776–780 (1996).Google Scholar
  8. 8.
    Paetau, I., C.-Z. Chen, and J. Jane, Biodegradable Plastic Made From Soybean Products. I. Effect of Preparation and Processing on Mechanical Properties and Water Absorption, J. Ind. Eng. Chem. Res. 33:1821–1827 (1994).CrossRefGoogle Scholar
  9. 9.
    Paetau, I., C.-Z. Chen, and J. Jane, Biodegradable Plastic Made From Soybean Products. II. Effects of Cross-Linking and Cellulose Incorporation on Mechanical Properties and Water Absorption, J. Environ. Polym. Degrad. 2:211–217 (1994).CrossRefGoogle Scholar
  10. 10.
    Spence, K.E., J. Jane, and A.L. Pometto III, Dialdehyde Starch and Zein Plastic: Mechanical Properties and Biodegradability, Ibid.:69–74 (1995).CrossRefGoogle Scholar
  11. 11.
    Jane, J., and S. Wang, Soy Protein-Based Thermoplastic Composition for Preparing Molded Articles, U.S. Patent 5,523,293 (1996).Google Scholar
  12. 12.
    Lim, S., and J. Jane, Storage Stability of Injection-Molded Starch-Zein Plastics Under Dry and Humid Conditions, J. Environ. Polym. Degrad. 2:111–120 (1994).CrossRefGoogle Scholar
  13. 13.
    Spence, K.E., A.L. Allen, S. Wang, and J. Jane, Soil and Marine Biodegradation of Protein-Starch Plastics, in Hydrogels and Biodegradable Polymers for Bioapplications, American Chemical Society, Washington, DC, 1996, pp. 149–158.Google Scholar
  14. 14.
    Wang, S., H.-J. Sue, and J. Jane, Effects of Polyhydric Alcohols on the Mechanical Properties of Soy Protein Plastics, J. Macro. Sci.—Pure Appl. Chem., AA33:557–569 (1996).Google Scholar
  15. 15.
    Huang, H.C., E.G. Hammond, C.A. Reitmeier, and D.J. Myers, Properties of Fibers Produced from Soy Protein Isolate by Extrusion and Wet-Spinning, J. Am. Oil Chem. Soc. 72:1453–1460 (1995).CrossRefGoogle Scholar
  16. 16.
    Ledward, D.A., and J.R. Mitchell, Protein Extrusion—More Question Than Answers? in Food Structure—Its Creation and Evaluation, edited by J.M.V. Blanshard and J.R. Mitchell, Butterworths, London, 1988, pp. 219–229.Google Scholar
  17. 17.
    Wiedmann, W., and W. Pfaller, Innovative Uses of Extrusion Technology in the Food Industry, in Research and Development Associates for Military Food and Packaging Systems 44:244–261.Google Scholar
  18. 18.
    ASTM D638-86, Standard Test Method for Tensile Properties of Plastics, Book ASTM Stand. 8:210–225 (1991).Google Scholar
  19. 19.
    ASTM D570-81, Standard Test Method for Tensile Properties of Plastics, Book ASTM Stand. 8:187–190 (1991).Google Scholar
  20. 20.
    Moore, C.O., J.V. Tuschhoff, C.W. Hasting, and R.V. Schanefelt, Application of Starches in Foods, in Starch: Chemistry and Technology, edited by R.L. Whistler, J.N. BeMiller, and E.F. Paschall, Academic Press, Orlando, 1984, pp. 575–591.Google Scholar
  21. 21.
    Rutenberg, M.W., and D. Solarek, Starch Derivatives, Ibid., edited by R.L. Whistler, J.N. BeMiller, and E.F. Paschall, Academic Press, Orlando, 1984, pp. 311–388.Google Scholar
  22. 22.
    Hanssen, M., in E for Additives, Thorsons Publishing Group, Wellingborough, United Kingdom, 1987, p. 107.Google Scholar

Copyright information

© AOCS Press 1999

Authors and Affiliations

  1. 1.Department of Food Science and Human Nutrition and Center for Crops Utilization ResearchIowa State UniversityAmes
  2. 2.Department of Industrial Education and TechnologyTowa State UniversityAmes
  3. 3.Bioproducts, Inc.Naperville

Personalised recommendations