FNH 200 Final Exam Questions And
Answers
Clostridium botulinum:
-type of bacteria
-habitat
-what makes it dangerous
-biggest concern in what foods
-prevention - -anaerobic bacteria
-soil, water, air
-has microbial spores that are very heat resistant and produces potent neurotoxin
that affects CNS
-grows well in low acid foods: milk, meat, fish, and vegetables
-thermal processing
Vegetative Cells vs Spores - Vegetative Cells:
-actively metabolizing cells
Spores:
,-dormant form of bacterial cell that germinates in favorable conditions producing
vegetative cell
Bacteria:
-oxygen requirements
-reproduction method/speed - -grows fastest in food
-reproduce by cell division
-facultative anaerobe
Yeasts:
-oxygen requirements
-reproduction method/speed - -reproduce by budding
-grow slower than bacteria
-facultative anaerobe
Moulds:
-oxygen requirements
-products produced - -produce spores/myotoxins
-aerobic
Rank bacteria, yeast and mould in order of least to most tolerate of severe
environmental conditions (pH, low H2O activity) - bacteria, yeast, mould
Result of enzymatic deterioration - -softening of fruit tissues
,-changes in flavor and color
-enzymes in apple tissue degrade pectin resulting in textural change
-enzymatic browning: polyphenol oxidase catalyzes oxidation of colourless
phenols in tissue to brown compounds
Factors affecting microbial growth, enzyme activity, and chemical reactions in
food - Temperature:
-↑ temp = ↑ rxn rate until optimum is past ↓ rxn rate
-↑ temp denatures protein, breaks emulsions, removes moisture,
hydrolytic/lipolytic rancidity and destroys vitamins
-↓ temp = change texture/color, breaks emulsions, fat separation, denatures
protein, loss of moisture
Moisture:
-↓ = retrogradation
-↑ = gelatinization
-changes in aw influence chemical/enzymatic rxn & microbial growth
Oxygen:
-oxidative rancidity (oxidation of fats)
-hydrolytic/lipolytic rancidity (release of free F.As by lipase or high temp)
, -oxidation of vitamins/color pigments = ↓ nutrition/looks
Physical Deterioration:
-tissue disruption releases enzymes into tissue and makes food susceptible to
microbial invasion
Time:
-quality ↓ overtime
Principle of Food Preservation - -must destroy MOs, inactivate enzymes, and
prevent oxidation
-maintain nutritional value and quality
Perishable vs Semi Perishable vs Shelf Stable Foods - Perishable:
-minimal processing -shelf life < 60 days
-meat, leafy vegetables, soft fruits, milk
Semi Perishable:
-shelf life of 2-6 months
-ice cream, cheese, dry snack foods
Shelf Stable:
-shelf life > 6 months
Answers
Clostridium botulinum:
-type of bacteria
-habitat
-what makes it dangerous
-biggest concern in what foods
-prevention - -anaerobic bacteria
-soil, water, air
-has microbial spores that are very heat resistant and produces potent neurotoxin
that affects CNS
-grows well in low acid foods: milk, meat, fish, and vegetables
-thermal processing
Vegetative Cells vs Spores - Vegetative Cells:
-actively metabolizing cells
Spores:
,-dormant form of bacterial cell that germinates in favorable conditions producing
vegetative cell
Bacteria:
-oxygen requirements
-reproduction method/speed - -grows fastest in food
-reproduce by cell division
-facultative anaerobe
Yeasts:
-oxygen requirements
-reproduction method/speed - -reproduce by budding
-grow slower than bacteria
-facultative anaerobe
Moulds:
-oxygen requirements
-products produced - -produce spores/myotoxins
-aerobic
Rank bacteria, yeast and mould in order of least to most tolerate of severe
environmental conditions (pH, low H2O activity) - bacteria, yeast, mould
Result of enzymatic deterioration - -softening of fruit tissues
,-changes in flavor and color
-enzymes in apple tissue degrade pectin resulting in textural change
-enzymatic browning: polyphenol oxidase catalyzes oxidation of colourless
phenols in tissue to brown compounds
Factors affecting microbial growth, enzyme activity, and chemical reactions in
food - Temperature:
-↑ temp = ↑ rxn rate until optimum is past ↓ rxn rate
-↑ temp denatures protein, breaks emulsions, removes moisture,
hydrolytic/lipolytic rancidity and destroys vitamins
-↓ temp = change texture/color, breaks emulsions, fat separation, denatures
protein, loss of moisture
Moisture:
-↓ = retrogradation
-↑ = gelatinization
-changes in aw influence chemical/enzymatic rxn & microbial growth
Oxygen:
-oxidative rancidity (oxidation of fats)
-hydrolytic/lipolytic rancidity (release of free F.As by lipase or high temp)
, -oxidation of vitamins/color pigments = ↓ nutrition/looks
Physical Deterioration:
-tissue disruption releases enzymes into tissue and makes food susceptible to
microbial invasion
Time:
-quality ↓ overtime
Principle of Food Preservation - -must destroy MOs, inactivate enzymes, and
prevent oxidation
-maintain nutritional value and quality
Perishable vs Semi Perishable vs Shelf Stable Foods - Perishable:
-minimal processing -shelf life < 60 days
-meat, leafy vegetables, soft fruits, milk
Semi Perishable:
-shelf life of 2-6 months
-ice cream, cheese, dry snack foods
Shelf Stable:
-shelf life > 6 months
