Introduction Lecture Flashcards
The good microorganisms
Add them to foods to they are there naturally
Used for food fermentation ?
Examples of good microorganism
Cheese Yogurt Sour cream Bread Salami Pickles
What is the goal of food fermentation ?
Preservation and/or creating unique flavors and textures
The bad microorganisms
Change foods and cause them to do bad or spoil
Affect aroma, texture and appearance of food
Examples of bad microorganism
Discolored,mushy or fuzzy vegetables
Sour milk
Slimy, putrid meat
The ugly microorganism
Pathogenic, cause illness ranging from mild to life threatening
May NOT affect sensory characteristics of the food
Examples of microorganism
Salmonella
E coli 0157: H7
Common side effects of ugly microorganism
GI symptoms
Diarrhea
Nausea
Vomiting
What is incubation period
From the time you are infected to the time that you show symptoms
Challenges with pathogens that have longer incubation period
You dont remember where and how you got it from
Collecting samples
Factors affecting microbial growth in foods
Intrinsic factors ( food environment
Extrinsic factors
What are intrinsic factors
Inherent parameter of foods that affect their microbiology
What are extrinsic factors
Properties of the storage environment that affect their microbiology
Examples of intrinsic factors
General nutrient Water activity PH Oxidation reduction potential Growth inhibitors in foods
What are general nutrient in intrinsic factor ?
Water Nitrogen Carbon for growth Carbon for energy Oxygen Phosphorous , potassium, sulfur Cofactors, vitamins , trace minerals , micronutrient
Water activity
Ratio of vapor pressure of water in sample to vapor pressure of pure water at the same temperature
Formula for water activity
Aw=Ps/Pw
Water activity is always
Less than 1
Water activity measure free water or bound water
Free water
What is formula for relative humidity
RH=aw X 100
Water activity for many bacteria
0.91
Processing to reduce water activity
Drying-less than 10-15% moisture means no growth
Additives- solutes
Salt, sugar, alcohol ( glycerol)
Compound blending- both in food manufacturing and recipe development
How does adding solutes is related to water activity
When you add solutes they bind to free water and will be unavailable so it lowers the water activity
Classification of foods by acidity
Acid foods 4.5 or less
Low acid : above 4.5
What are foodborne microorganisms?
Molds
Bacteria
Parasites
Viruses
Molds
Multicellular organisms
Bacteria
Single celled organisms that live independently
Parasites
Intestinal worms or microscopic Protozoa that live in a host animal or human
Viruses
Small particles that live and can only replicate in a host
Where do foodborne pathogens live
Most are residents of intestinal tracts of human and animals
Some common in soils
Pathogens that live in intestinal tract of humans and animals
Salmonella Ecoli O157:H7 Shigella Campylobacter Viruses and parasites
Foodborne pathogens that live in soils
Listeria monocytogenes
Bacillus cereus
Clostridium botulinum
What are Extrinsic Factors?
Temperature Relative humidity Atmosphere of storage Physical state Additives
Most important Extrinsic factor?
Temperature
Low temperature
Prolong generation time and extend shelf life
Hot temperature
Prevent microbial growth
High temperature
Kill microorganisms and spores
Goal of MAP
Slow respiration rates
Reduce microbiological growth
retard enzymatic spoilage
How to achieve MAP
Reduce oxygen content
Increase carbon dioxide
Increase Nitrogen
2 methods of MAP
Vaccum packaging
Gas packaging
What does vacuum packaging do?
Result in headspace O2 of less than 1% and CO2 levels of 10-20% depending on tissue or microbial respiration
What does Gas packaging do?
Extension of vacuum packaging
Replace the removal of air with another gases-usually N2 and Co2 or O
Name some Edible Antimicrobial films
Zein
Bacteriocins
Nisin
Nisin is particularly good for inhibition of
Listeria
