Lecture 3 Flashcards
What is a good growth media for bacterial growth?
Milk
Why is milk a good growth media for bacterial growth?
High water content
Neutral pH
Variety of nutrients
What is pasteurization?
A rapid heat treatment followed by rapid cooling
What is the purpose of homogenization?
Fat particle reduction
What is the purpose of homogenization?
Break down fat globules so that the fat is dispersed evenly throughout
What are the two types of contamination?
Direct and environmental contamination
What are examples of direct contamination?
Animal/human health
Udder health
Residual fecal matter
What are examples of environmental contamination?
Atmosphere, water supply, inadequate equipment cleaning, inadequate refrigeration, and cross-contamination.
What are the major bacterial spoiling agents in dairy products?
LAB, Psychotropic Bacteria and Coliforms
The over-fermentation of LAB can lead to what?
Excessive acid production
What does psychro mean?
Cold
What does tropic mean?
Grow
True or False. Psychrotropic bacteria grow at refrigeration temperatures and are significant spoilage agents in dairy.
True
What type of bacteria produces enzymes that remain active even after pasteurization?
Psychrotropic bacteria
What spoils dairy products by producing gas and off odors?
Coliforms
What ferments lactose to produce CO2 resulting in gas pockets in cheese and spoilage in fluid milk products?
Coliforms
What are common signs of souring?
Sour milk and curding
What are the causes of souring?
Over fermentation of LAB
What are signs of ropiness?
Slimy, viscous consistency
What causes ropiness?
Specific types of bacteria that produce extracellular polysaccharides. EPS
What causes sweet curdling?
Section of proteases
What are the signs of sweet curdling?
Coagulates without the typical souring associated with lactic acid production
What is the primary energy source in milk?
Lactose
What is fermented to lactic acid?
Lactose
What remains soluble in milk and is less susceptible to microbial proteolysis?
Whey protein
What are the two bacterial growth inhibitors found in milk?
Lactoferrins and lactoperoxidase
What are lactoferrins?
Iron binding agents that limit the presence of iron, thus controlling bacterial growth
What is lactoperoxidase system?
An enzyme that is present in fresh raw milk. Can be reactivated by adding thiocyanate
When do spore-forming bacteria form?
Low-acid milk products are preserved by sub-sterilization heat treatment and packaged with little chance of recontamination with vegetative cells
What are examples of products in which spore-forming bacteria could occur?
aseptically packaged milk, cream, sweetened and unsweetened condensed milk
What is the most commonly know type of spoilage for produce?
Soft rot
What is soft rot?
When the plant’s structural polymers degrade
What are examples of degradative enzymes?
Pectinase, cellulase, protease, phosphatidase, dehydrogenase
What does cellulase break down?
Cellulose –> Glucose
What are the two groups that produce can be placed in based on physiological changes after harvesting?
Non-climacteric and climacteric
Non-climacteric
when it stops ripening after harvesting
What are contamination sources for produce?
Irrigation water
Soil and manure
Wildlife and Livestock
Atmosphere/Weather
Harvesting equipment
Composition of produce (pH, aw, sugar, aroma)
True or False. The spoilage of dried fruits is generally caused by osmophilic yeast and xerotolerant molds
True
What is the purpose of chemical sanitizers?
To help prevent cross-contamination by wash water
What is the purpose of MAP?
Reduced respiration and reduce senescence.
True or False. The microbiota of frozen produce is the same as fresh produce.
True
True or False. All produce undergo some type of processing before reaching the consumer.
True
