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YR2SEM1 > Food2150 Set 2 > Flashcards

Food2150 Set 2 Flashcards

1
Q

What was Napolean’s primary challenge in the Franco-Russian (Napoleonic) wars?

A
  • supplying advancing French army food
  • limiting conquest to months they could pillage Russian agricultural resources
  • offered reward to anyone who could develop a method to preserve food
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2
Q

What are Koch Postulate’s four criteria?

A
  • The microorganism must be found in diseased but not healthy individuals;
  • The microorganism must be cultured from the diseased individual;
  • Inoculation of a healthy individual with the cultured microorganism must
    recapitulated the disease
  • The microorganism must be re-isolated from the inoculated, diseased individual
    and matched to the original microorganism.
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3
Q

Who was Nicolas Appert?

A
  • spoilage organisms were once unbeknownst
  • developed an early canning
    (Appertization) industry by preserving foods in
    glass bottles, forming a continuous seal (preventing anything from entering)
  • ontents were heating in a pressurized glass vesicle (early retort) to prevent spoilage.
  • spontaneous generation disproved
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4
Q

Who was Louis Pasteur?

A
  • his work was the foundation of hygiene, public health and the germ theory of diseases
  • to ensure quality and limit losses of French wine (major national revenue source)
  • postulate: fermentation of wine, yeast used to make beer and wine decomposed sugar into ethanol and CO2
  • spoilage yeasts convert sugar to lactic acid leading to spoilage, coined the term microbiology
  • swan-neck experiment
  • foundation of pasteurization, disproving spon. gen.
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5
Q

How has mass production changed from the past to today?

A

Past: food grown or hunted (some primary processing), home prep

Today: mass production and feeding, central processing and storage, advance prep, nation/worldwide distribution
- outbreaks less frequent but involve more people

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5
Q

What are the goals of food preservation?

A
  • Safety - eliminate food hazards
  • Extended shelf-life - limit spoilage
  • Quality - nutritional and aesthetics
  • Availability and Variety
  • Convenience
  • Favorable economics- minimizing losses and waste
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6
Q

What are the causes of deterioration of food preservation?

A
  • pests (insect, rodents)
  • microorganisms (bacteria, yeasts, mold, viruses, parasites)
  • chemical/biochemical reactions (oxidation, enzymatic activity)
  • physical factors (light, temperature, moisture, damage by force)
  • time !! (deteriorates all food)
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7
Q

What is preservation intended to do?

A
  • decrease rate of microbial growth (refrigeration)
  • stop microbial growth (freezing)
  • destroy/inactivate microorganisms (heating)
  • restrict access of microorganisms to the food (packaging)
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8
Q

What is water activity?

A
  • the water available to support microorganisms
  • close to 0 for freezing, and so microorganisms cannot move freely
  • lower during refrigeration
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9
Q

When is lactic acid bacteriostatic and bactericidal?

A

bacteriostatic: @1%
- limits growth of bacteria
bacteriostatic: @2+%
- kills bacteria

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9
Q

How does fermentation affect food?

A
  • increased shelf life
  • enhanced safety
  • improved quality + flavour
  • fermentation of sugars by bacteria or yeasts to produce lactic acid, CO2, ethanol etc
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10
Q

How is yogurt made?

A
  • starter culture (contains Lactobacillus delbrueckii subsp. Bulgaricus and Streptococcus thermophilus)
  • growth temperature important to enable species (43.3C)
  • above 43.3C: Lactobacillus predominates, making it too acidic
  • below 43.3C: Streptococcus has too strong of flavour
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11
Q

What are some hazards for foodborne illnesses?

A
  • illnesses resulting from food ingestion
  • biological (bacterial, parasites, viruses, toxins)
  • chemical (cleaners, lubricants, antibiotics, hormones)
  • physical (glass, woodchips, plastic, metal)
  • not just microorganisms !
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11
Q

How does organic acids affect food?

A
  • Antimicrobial effect due to their undissociated molecules
  • pKa range 3.6-4.8: dissocatied lactic acid cannot get through cell wall, in protonated form can move into cell wall
  • most foods have pH > 5
  • small molecules pass the cellular membrane of microbes
  • provide flavour, enhance shelf-life
  • lactic, acetic, propionic acid
  • @1-2%: prevent spoilage
  • effective against gram pos, gram neg, yeats, mols
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12
Q

Describe sporeformers

A
  • highly resistant form for adverse conditions
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13
Q

What are intrinsic parameters: factors affecting microbial growth?

A
  • Biological structures -barriers that keep microorganisms out (e.g., fruit
    skin)
  • nutrient content (organism specific – they all need energy, C, N,
    certain vitamins, minerals)
  • pH and organic acids (pH 7, neutral – low, medium, high acid foods
    and tolerances, acid production)
  • moisture content / water activity (aw) – water availability
  • antimicrobial constituents
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13
Q

Describe typical water activity (aw values)

A

p/pinitial (pi>p)
- free water (1.0)
- some immobilized (0.9)
- bacteria + yeasts stop growing (0.8)
- bacteria + yeasts + molds stop growing (0.7)
- enzymatic reactions slow/stop (0.5)
- chemical reactions slow/stop (0.3)

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14
Q

What is a strict or obligate aerobe?

A
  • can tolerate a level of oxygen
    equivalent to or higher than that present in an air atmosphere
    (21% oxygen), and has a strictly respiratory type of metabolism.
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14
Q

What are extrinsic parameters: factors affecting microbial growth?

A
  • storage temp.
  • relative environment humidity
  • presence + conc. of gases
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15
Q

What is the difference between intrinsic and extrinsic parameters?

A

Extrinsic: food storage, to prevent or slow microorganism growth
Intrinsic: food properties

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16
Q

Describe temperature as a factor affecting microbial growth

A
  • destroyed by heat - varies by species, can survive but not grow at cold temperatures
  • temperature increases, growth rate increases, to an optimum
  • Psychrotrophs - optimum growth temperature 20-30oC, can reproduce at temps. of 7oC or below
  • Mesophilic, 30-37oC optimum, (body temperature 370C)
  • Thermophilic 50-80oC optimum
17
Q

What is a microaerophile?

A
  • An organism that is capable of oxygen-dependent
    growth but cannot grow in the presence of a level of oxygen
    equivalent to that present in an air atmosphere (21% oxygen).
18
Q

What is a facultive aerobe?

A
  • an organism that can grow well both in
    the absence of oxygen and in the presence of a level of oxygen
    equivalent to that in an air atmosphere (21% oxygen)
19
Q

What is a strict or obligate anaerobe?

A
  • An organism that is incapable of
    oxygen-dependent growth and cannot grow in the presence of an
    oxygen concentration equivalent to that present in an air
    atmosphere (21% oxygen).
20
Q

What are the HACCP seven principles and what do they do?

A
  • super harsh guidelines to avoid bacteria in prepared foods (avoid outbreaks)
    ◼Conduct a hazard analysis (biological, chemical, physical)
    ◼Identify critical control points on flow diagram
    ◼Establish critical limits for each CCP
    ◼Establish CCP monitoring procedures
    ◼Establish corrective actions if limits exceeded
    ◼Establish record keeping procedures
    ◼Establish verification protocols
20
Q

What is botulinum and how is it present in canned foods?

A
  • food in containers are anaerobic and thus spore-forming bacteria become active if not processed to a high temp.
  • fatal
  • anaerobic: grows and produces toxin spore-former grows at pH >4.5
  • high acid: sterilize it due to botulism
  • low acid: minimal thermal process
21
Q

What is gram negative?

A
  • release fragments of LPS causing fever
  • lysed by immune system
21
Q

What is hurdle technology?

A
  • Combining numerous sublethal intrinsic and extrinsic modifications
    impede microbial growth
  • create an environment that does not support microbial growth
  • combine conditions that individually do not stop living, but together do
21
Q

What is gram positive?

A
  • no fever, lipopolysaccharides not broken out
22
Q

Describe foodborne infections going through the intestinal track

A
  • Infectious bacteria are consumed and they colonize the intestinal track.
  • During colonization the epithelial cells are damaged
  • Damaged epithelial cells are unable to take up solutes
  • Osmotic pressure causes water to move from tissues back to the intestinal track
  • Damage to the intestinal lining leads to vomiting
  • If the bacteria is gram negative it induces a pyrogenic effect causing a fever
    due to the presence of lipopolysaccharide
  • Examples include Salmonella, Yersinia, Shigella
  • Onset ranges from 12hr to 2 days depending on the quantity of bacteria
    ingested
23
Q

Describe food borne intoxications and how they come to be

A
  • Bacteria that cause intoxications are those that produce toxins in the food during growth
  • Onsets are very fast due to the presence of the preformed toxin

EX: Clostridium botulinum, Staphylococcus aureus, Clostridium
perfringens, and Bacillus cereus

24
Q

What are different ways to preserve food chemically?

A
  • solute addition (water activity control): sugar, salt
  • pH control (acids)
  • preservatives (nitrate, benzoate (moving away), sorbate
24
Q

Describe water activity control as preservation technique

A
  • reduce it so that there is no molecular mobility
  • most common technique
  • water activity is colligative: only matters depending on amount of molecule, not its identity
  • sugar and salt: bind water available in food, same effect as dying
25
Q

Describe pH control as a preservation technique

A
  • at home: shouldn’t can things of pH below 4.6 as we cannot sterilize it
  • pH below 4.6-> conditions for botulism won’t grow
  • ex: tomatoes are difficult to can, as they vary: have to double check pH so it is below 4.6
26
Q

What is a biological preservation technique?

A
  • fermentation (addition of antimicrobial contaminants)
27
Q

What is a thermal preservation technique?

A
  • heating + cooling
28
Q

How does heating and cooling differ as preservation techniques?

A

heating:
- denature proteins in bacteria to stop growing
- kills bacteria, but often causes different sensory attributes
- don’t like to heat: things with free sugars (it caramelizes fast)
cooling:
- stops them from growing (does not denature)

29
Q

What are the 3 types of preservation by heat?

A

blanching, pasteurization, commercial sterilization

29
Q

Describe blanching as a preservation technique by heat

A
  • MILD heat treatment for fruits and vegetables
  • inactivate enzymes prior to freezing
  • de-gas products before canning
  • wilt vegetables to facilitate packaging prior to freezing or canning
  • requires something else to keep it shelf stable (freezing)
  • not to remove pathogens or spoilage microrganisms
  • deactivates enzymes
  • will not brown as the main protein is denatures
30
Q

When is botulism present?

A

Anaerobic - grows and
produces toxin spore-former grows
at pH > 4.5 (4.6)
- food in containers are anaerobic and thus
spore-forming bacteria become active if
not processed to a high temperature
- solid: surface-in
roll liquids: convection liquid in surface of can is exchanged: heats up uniformly

30
Q

Describe pasteurization as a preservation technique by heat

A
  • MODERATE heat treatment of liquid products
  • eliminate pathogenic bacteria
  • reduce the numbers of spoilage bacteria (not totally eliminated)
  • lasts weeks-months
31
Q

Describe commercial sterilization as a preservation technique by heat

A
  • destroy all microorganisms of commercial significance
    and produce a shelf-stable product
  • canning: - in-container
  • UHT (ultra high temp.) aseptic processing & packaging:
    out-of-container, continuous
  • long shelf-life
32
Q

What is the hermetic seal?

A
  • prevents contamination of
    the material
  • rounded lid and sidewall
  • side dent: ok to consume, top rim has sent: garbage (hermetic seal broken, potential contamination)
  • changed way we put cans together
33
Q

Why do we want to eliminate BPA?

A
  • exhibits hormone-like properties that mimic estrogen effects in body
  • banned in EU
  • supposedly not used since 2017 in Ca (not true)
34
Q

How do we sterilize food in its can?

A
  • Unsterile food is added to an unsterile
    can, sealed and immediately thermally
    processed
  • Minimum thermal process of the coldest
    point, must achieve a 12D process which
    means a 12 log reductions
  • Hermetic seal prevents contamination of the
    material after commercial sterilization
35
Q

Why does microbial death or inactivation never reach absolute 0?

A
  • because the death rate follows first-order reduction kinetics
  • 1,0.1,0.01
36
Q

What is the D-value for a bacterial survival curve?

A

time(temp) (min) required for 1 log reduction of bacteria (nutrient)
- dependent on intrisic and extrinsic propertiesL time it takes to get a log reduction of microorganisms
- have to report temp (temp-dependent), higher T= shorter D value
- D72: D at 72C=1 min, every minute at 72C, there is a log reduction, it would take 12 minutes to get to the 12 log red.

37
Q

What is the Z-value for a bacterial survival curve?

A
  • temperature dependence of the D-value
  • The temperature change (oC) required to
    change D-value by a factor of 10
  • higher T= shorter D, quicker processing of food

D72=1 min and Z=5°C
Indicates that if the processing temp increases from 72 to 77°C, for example, the new D = 0.1 min (or 6 sec) to get 1 log reductions

38
Q

What is the 3 different types of milk pasteurization?

A

LTLT (ice cream), HTST (milk), UHT (shelf-stable milk)
(low temp, low time) (high temp, short time) (ultra high temp)

39
Q

What is aseptic processing?

A
  • Process the food outside of the package
  • Allows for rapid heating and cooling
  • Must be packaged aseptically
  • food, packaging, environment all have to be sterile or else can be recontaminated
40
Q

What issues does refrigeration cause?

A
  • chill injury in fruits and vegetables (soft apples and dark bananas)
  • chill sweetening where starch is slowly converted to sugar
  • bread staling where starch changes more rapidly when in the cold than when at room temperature
  • cold shortening where freshly slaughtered meat
    muscle fibers contract and become tough to chew
41
Q

What does refrigerating food do?

A
  • reduce the rate of microbial growth,
    chemical changes and physical changes

YR2SEM1 (10 decks)

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