W8, Wine spoilage, necrotic enteritis in chickens
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What are the spoilage characteristics caused by Dekkera/Brettanomyces?
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
What steps could a winemaker take to control Dekkera/Brettanomyces?
• 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
Name the causal agent of necrotic enteritis in broiler chickens, and list three of its morphological or physiological features.
Clostridium perfringens • Gram positive • Rod-shaped • Anaerobic • Endospore-forming • Motile • Optimal ph: 6-8 • Ubiquitous in the environment
Describe the predisposing factors that can elicit a necrotic enteritis outbreak in a broiler chicken flock.
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