W8, Wine spoilage, necrotic enteritis in chickens

Question 1

What are the spoilage characteristics caused by Dekkera/Brettanomyces?

Answer 1

Contributes its own flavours and aroma

• ‘Brett’ character
  
  • mainly caused by volatile phenols
  • smells and tastes like a bandaid with a metallic aftertaste
  • mostly associated with red wine stored in barrels
• Mousy off-flavour (aftertaste reminiscent of the way a mouse cage smells)
  
  • N-heterocycles (ring structures containing a Nitrogen)
• Volatile acidity
  
  • ethyl acetate (nail polish remover)
  • acetic adic (vinegar)

Will grow in dry wine (not much sugar, which is the C source for most yeast/bacteria)

• Will turn it cloudy
  
  • Consumers expect wine to be clear

Question 2

What steps could a winemaker take to control Dekkera/Brettanomyces?

Answer 2

• Prioritise sanitisation to prevent the growth of unwanted microbes
  
  • Incl. barrel maintenance (making sure its not full of microbes when the wine goes in)
• Control (limit) contact with air
• Use sulphur dioxide
  
  • potent antimicrobial
  • pH-dependant (need to be around (or below) pH 3)
• Decrease the amount of residual sugars in wine (get it as dry as possible)
  
  • includes inside the barrel the wine is getting put in to

Question 3

Name the causal agent of necrotic enteritis in broiler chickens, and list three of its morphological or physiological features.

Answer 3

Clostridium perfringens

• Gram positive
• Rod-shaped
• Anaerobic
• Endospore-forming
• Motile
• Optimal ph: 6-8
• Ubiquitous in the environment

Question 4

Describe the predisposing factors that can elicit a necrotic enteritis outbreak in a broiler chicken flock.

Answer 4

Diet that has a high protein : energy

• unlikely
• fish meal and bone meal really high in protein
• raises pH to optimal level
• provides a nutritional substrate for bacteria

Viscous diet (high fibre)

• more likely
• wheat and barley have a high glucan content
  
  • normally in birds you add an enzyme to help with digestability of wheat and barley
  • if too much and/or not enough enzyme, the microbes are able to break it down instead
  • glucans are sticky
    
    • slows down the digesta in the gut
      
      • more time in the gut = more time for the bacteria to utilise it as a substrate and proliferate.

Coccidiosis

• produced by Eimeria parasites
• causes intestinal damage (kills intestinal epithelial cells)
• reduces luminal pH, making it more favourable for microbial growth
• Increases the transit time for digesta
• Increases mucus production
• Preconditions the gut for overgrowth