Lecture 1 Flashcards
What is a food ecosystem?
Food is an ecosystem composed of the environment and the microorganisms living in it.
What are intrinsic factors?
Characteristics inherent to the food itself
What are examples of intrinsic factors
Water activity, pH and nutrients
What are extrinsic factors?
Environmental factors that affect food.
What are examples of extrinsic factors?
Time, temp, microorganisms, packaging, gases
True or False. Intrinsic factors and extrinsic factors can be manipulated to preserve food.
True
True or False. Food may contain multiple microenvironments.
True
What can affect gene expression of cells?
Acidity
The _______ the pH, higher energy is required by the cell to maintain cell intracellular pH neutrality and less energy is left for growth.
lower
Acidic food requires _______
milder
What is preshock?
The exposure to mild acid.
What type of pH intrinsic factor involves shifting cells directly from alkaline conditions to acidic?
Acid shock
What is free water?
Water that is available for microbial growth and chemical reactions.
What is bound water?
Water that is not available for microbial growth or chemical reactions
What is the measure of available water or energy of water in food?
Water activity
What foods are susceptible to bacteria?
Foods with high protein and water activity
How do cells protect themselves from osmotic stress?
Compatible solutes intracellularly
what not only controls growth rate but also regulates bacterial gene expression?
Temperature
What is multiple hurdle technology?
The use of two or more intervention measures to ensure a reduction of potential bacterial growth
What are the benefits of multiple hurdle technology?
Higher efficacy
Better taste
Save energy
Allows use of milder treatments
Why use enrichment?
Bacteria may be present in a low amount, some pathogens have very low infective doses.
What cell type is this: cells exposed to sub-lethal conditions, lose the ability to grow on selective media but can grow on non-selective media.
Injured Cells
Can injured cells recover and cause an outbreak?
Yes
What cannot be cultured on any culture media?
VBNC
What are 3 ways we can detect VBNC?
Cytological methods, viability staining, reverse transcription RT-PCR
What is biofilm?
Aggregation of bacteria or groups of bacteria living together on a solid surface
What are the steps in biofilm formation?
- Solid surface conditioning
- Adsorption of bacterial cells on a surface by biopolymer formation
- Microcolony formation: adsorbed cells multiply and form microcolonies
What are cells that can detach and move on to form biofilm at different locations?
Planktonic Film
