High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age

L. Gonzalez, S. Martin, S. Siso, T. Konold, A. Ortiz-Pelaez, L. Phelan, W. Goldmann, P. Stewart, G. Saunders, O. Windl, M. Jeffrey, S. A. Hawkins, M. Dawson, J. Hope

Research output: Contribution to journalArticlepeer-review

Abstract

The factors influencing the microstructure of fresh cheese, particularly the particle size, and its reduction by mechanical post-processing, were studied. In order to evaluate the influence of temperature and holding-time prior to cooling, microgel suspensions with a mean protein content of 8.22+or-0.23 g/100 g were produced by using membrane filtration (cut-off of 1.0 micro m). Fermentation was carried out overnight with culture F-DVS CC06, and rennet was added at one ml/100 litre at pH 6.50. The particle size distribution was measured by laser light scattering, and d75.3 was chosen to represent particle growth of big particles. In order to destroy particles formed in the microgel suspension, the treated microgel suspensions were prepared and tempered in a vessel at 38 degrees C for 300 min prior to post-processing. The mechanical post-processing was carried out with a rotor/stator device (Ytron-Z, Ytron Process Technology GmBH & Co., KG, Bad Endorf). Both a sensor for torque and rotation number of device were integrated to monitor the power input during post-processing. The particle size decreased with increasing rotational number. Furthermore, decreasing flow rates tended to decrease the particle size. A higher mechanical load resulted only in further degradation of the structure, and therefore an increased tendency to structural defects. Temperature load forced the particle growth in concentrated microgel suspensions. The higher the applied temperature, the faster the particle growth. Direct cooling after concentration was a useful tool for inhibiting particle growth. Mechanical post-processing with a rotor/stator device could be applied to reduce particle size.
Original languageEnglish
Article number65
Number of pages13
JournalVet Res
Volume40
Issue number6
Publication statusPublished - 2009

Keywords

  • Milk and Dairy Produce [QQ010]
  • Food Processing (General) [QQ100]
  • Food Storage and Preservation [QQ110]
  • Food Composition and Quality [QQ500]
  • Techniques and Methodology [ZZ900]
  • cheese quality
  • cheese starters
  • cheesemaking
  • cheeses
  • concentration
  • cooling
  • dairy equipment
  • fermentation
  • filtration
  • food processing
  • food quality
  • food storage
  • fresh cheese
  • gels
  • milk products
  • organoleptic traits
  • particle size
  • pH
  • protein content
  • rennet
  • rotors
  • shearing
  • storage life
  • temperature
  • tempering
  • texture
  • whey
  • cheese making
  • dairy products
  • fleecing
  • hydrogen ion concentration
  • organoleptic properties
  • potential of hydrogen

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