African Journal of
Food Science

  • Abbreviation: Afr. J. Food Sci.
  • Language: English
  • ISSN: 1996-0794
  • DOI: 10.5897/AJFS
  • Start Year: 2007
  • Published Articles: 837

Full Length Research Paper

Proteolysis of milk heated at high temperatures by native enzymes analysed by trinitrobenzene sulphonic acid (TNBS) method

Lucy M. CHOVE1*, Abdulsudi ISSA- ZACHARIA, Alistair S. GRANDISON2 and Michael J. LEWIS2
  1Department of Food Science and Technology, Sokoine University of Agriculture, P.O. Box 3006, Morogoro, Tanzania. 2Department of Food and Nutritional Sciences, University of Reading, P.O. Box 226, Reading RG6 6AP, UK.
Email: [email protected] or [email protected] or [email protected]

  •  Accepted: 17 July 2013
  •  Published: 31 August 2013



Native enzymes play a significant role in proteolysis of milk during storage. This is significant for heat resistant native enzymes. Plasmin is one of the most heat resistant enzymes found in milk. It has been reported to survive several heat treatments, causing spoilage during storage. The aim of this study was to assess susceptibility of high temperature heated milk to proteolysis by native enzymes. The trinitrobenzene sulphonic acid (TNBS) method was used for this purpose. Raw milk was heated at 110, 120, 130,142°C for 2 s and 85°C for 15 s and milk processed at low temperature (85°C /15s) was selected to mimic pasteurisation. TNBS method confirmed that raw milk and milk processed at 85°C /15s were the most proteolysed, whereas treatment of milk at high temperatures (110, 120, 130 and 142°C for 2 s) inactivated the native enzymes. It may thus be concluded that high temperature processing positively affects proteolysis by lowering its susceptibility to spoilage during storage.


Key words: Plasmin, proteolysis, trinitrobenzene sulphonic acid (TNBS), heat treatment, isoelectric precipitation.