Proteolysis and storage stability of UHT milk produced in Turkey

Topcu A., Numanoglu E., Saldamli I.

INTERNATIONAL DAIRY JOURNAL, vol.16, no.6, pp.633-638, 2006 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 16 Issue: 6
  • Publication Date: 2006
  • Doi Number: 10.1016/j.idairyj.2005.08.018
  • Journal Name: INTERNATIONAL DAIRY JOURNAL
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.633-638
  • Keywords: UHT milk, UHT temperature, proteolysis, plasmin, bacterial proteinase, somatic cell count, SOMATIC-CELL COUNT, DAIRY-PRODUCTS, BITTER FLAVOR, BOVINE-MILK, RAW-MILK, PLASMIN, QUALITY, CHEESE, PEPTIDES
  • Hacettepe University Affiliated: Yes

Abstract

The effect of raw milk quality (total and psychrotrophic bacterial and somatic cell counts, proteinase and plasmin activity) and UHT temperature (145 or 150 degrees C for 4 s) on proteolysis in UHT milk processed by a direct (steam -injection) system was investigated during storage at 25 degrees C for 180 d. High proteinase activity was measured in low-quality raw milk, which had high somatic cell count, bacterial count and plasmin activity. The levels of 12% trichloroacetic acid-soluble and pH 4.6-soluble nitrogen in all milk samples increased during storage, and samples produced from low-quality milk at the lower UHT temperature (145 degrees C showed the highest values. Bitterness in UHT milk processed from low-quality milk at 145 degrees C increased during storage-. gelation occurred in that milk after 150 d. The RP-HPLC profiles of pH 4.6-soluble fraction of the UHT milk samples produced at 150 degrees C showed quite small number of peaks after 180 d of storage. Sterilization at 150 degrees C extended the shelf-life of the UHT milk by reducing proteolysis, gelation and bitterness. (c) 2006 Elsevier Ltd. All rights reserved.