Starch Conversion

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[Shetty, 2006]:

  • gelatinization: heating in excess water, endothermic reaction, loss of crystalline order
  • irreversible w/r to the shape of the granule
  • amylopecting and amylose may form new structures when cooled down -> retrogradation
  • during heating -> swelling to up to 30x its weight. reversible process
  • retrogradation is cause for hard stale bread

[Donald, 2004]

  • irreversible order -> disorder transition called gelatinization.
  • swell, absorb water, leach amylose, loose crystallinity.
  • birefringence is lost
  • range is quite large for all granules 56-64 for wheat and potato but much smaller (1 C) for individual granules
  • substantial swelling
  • inital water absorption in the amorphous growth rings
  • swelling driven process
  • crystalline regions break open b/c of the swelling
  • if water is limited (high density or presence of sugars) swelling doesn't take place as well and a melting of the crystalline sections needs to happen
  • gelatinization temperature increases
  • Maize starch: from 70C to 78C when placed in 25% sugar solution.
  • sugar removes free water

[Briggs, 2004]

  • sugar concentration raises gelatinization temperature
  • enzymatic breakdown should happen before retrogradation occurs
  • some starches require cooking temps between 90 and 120C (194-248F) before amylose lipid complexes are broken -> one of the reasons why cooking of some adjuncts is necessary.

[Narziss, 2005]

  • starch is insoluble in cold water
  • granules start to swell (50C +)
  • then they get small fissures
  • amylose leaches out
  • amylopectin separates as gelatenous sheet
  • viscous and sticky mass is formed\
  • doesn't happen in mashing b/c of the enzymes
  • but may cause problems in cereal cookers (especially rice)

[Kunze, 2007]

  • 4 phases: ungelatenized, gelatinization, liquification, saccharification
  • gelatinization temp dependent on growing conditions and crop year : 59 - 65C




  • gelatinization
  • active enzymes
  • emzyme temperature and pH optima
  • mash parameters affecting conversion


References

[Valclavik] Vickie A. Valclavik, Elizabeth W. Christian, Essentials of Food Science, Third Edition, Springer
[Champe] Pamela C, Champe, Richard A. Harvey, Denise R. Ferrier, Biochemistry, Lippincott's Illustrated Reviews
[Kunze, 2007] Wolfgang Kunze, Technologie Brauer und Maelzer, 9. Auflage, VLB Berlin
[Narziss, 2005] Prof. Dr. agr. Ludwig Narziss, Prof. Dr.-Ing. habil. Werner Back, Abriss der Bierbrauerei, Technische Universitaet Muenchen (Fakultaet fuer Brauwesen, Weihenstephan). WILEY-VCH Verlags GmbH Weinheim Germany, 2005
[Donald, 2004] A. M. Donald, Understanding Starch Stucture and Functionality, Chapter 5 in Starch in Food: Structure, Function and Applications By Ann-Charlotte Eliasson, CRC Press, 2004
[Shetty, 2006] Kalidas Shetty, Food Biotechnology, CRC Press, 2006