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Microbiology > Food and Spoilage > Flashcards

Food and Spoilage Flashcards

1
Q

Why do we care about food microbiology

A

Large impact on economic market & largely consumed
* Alcoholic beverages
* Fermemented food

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2
Q

Respiration vs Fermentation

A
  • Respiration externally-derived electron acceptor, either O2 (aerobic) or some other oxidant (CO2, sulfate - anaerobic)
  • Fermentation: redox reaction in the absense of an added electron acceptor - endogenous organic electron acceptor = using something already in the cell
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3
Q

2 major types of fermentation

A

lactic acid & ethanolic

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4
Q

What are the three genera (genus) that use pyruvate to make important products for fermentation

A
  • Aspergillus: lactic acid
  • Lactobacillus: lactic acid
  • Saccharomyces: ethanol, CO2
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5
Q

Why are fermented foods so common

A
  • Preservation of food
  • Improved digestibility
  • Addition of nutrients and flavors
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6
Q

Cacoa seeds are fermented by:

3 things

A
  1. yeasts
  2. lactic acid bacteria
  3. acetic acid bacteria
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7
Q

The process of cacoa bean fermentation depends entirely on what type of microbial fermentation

A

Indigenous microbial fermentation - microbes that are naturally present on the cocoa beans and their surrounding environment

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8
Q

Microbial succession during cocao fermentation

A
  • Yeast (day 1-2): degrade pectin; ferment sigars and citrate to ethanol and acetate
  • **Lactobacillus **(day 2-4): ferments sugars to lactate and acetate
  • Acetobacter (day 4): oxidizes ethanol
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9
Q

Traditional ____ were used to start fermentation of soy and other products, today ____ are used

A

indigenous microbes; starter cultures

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10
Q

What does Aspergillus oryzae ferment

A

Soy products
* miso
* soy sauce

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11
Q

Saccharomyces cerevisiae

A

“Brewer’s yeast” or “baker’s yeast”
* involved in the fermentation/production of bread, beer, and wine

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12
Q

Which of the following is the best definition of a “yeast”?
a) Saccharomyces cerevisiae.
b) Beer and bread making Fungi.
c) Unicellular growth of a fungus.
d) Filamentous growth of a fungus.
e) Any single-celled Eukaryote.

A

c) Unicellular growth of a fungus.

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13
Q

Energy metabolism process for Saccharomyces cerevisiae (S. cerevisiae) in aerobic conditons

A

Aerobic respiration: complete breakdown of glucose into carbon dioxide and water, releasing energy in the form of ATP (high energy pathway)

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14
Q

Energy metabolism process for Saccharomyces cerevisiae (S. cerevisiae) in anaerobic conditons

A

Anaerobic fermentation (glycolysis + alcohol fermentation) Less efficient than aerobic respiration, yielding only 2 ATP molecules per glucose molecule

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15
Q

3 steps in anaerobic fermentation of sugar to ethanol & CO2 in S. cerevisiae

A
  1. Glycolysis
  2. Pyruvate to acetaldehyde by pyruvate dehydrogenase
  3. Acetaldehyde to ethanol by alcohol dehydrogenase
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16
Q

How is fermentation by Saccharomyces used to make bread

A

employs the CO2 used during fermentation: the alcohol is baked off & CO2 is responsible for leavening the bread causing it to rise as gas gets trapped

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17
Q

When does wine making date back to; how did it compare to water at that point

A

evidence for wine making dates to ~6000 BC
* safer to drink than water, before filtration and refrigeration

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18
Q

Primary fermentation of wine via Saccharomyces

A

First stage of wine fermentation - defines the wines alcohol content
Sugar –> Ethanol + CO2
* Fermentation is inhibited when ethanol reaches about 15%
* Amount of starting sugar determines sweetness of wine

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19
Q

Secondary fermentation of wine (malolactic fermentation)

Is this done by a diff bacteria?

A

Malic acid –> lactic acid + CO2
via Oenococcus oeni (lactic acid bacteria)
* contributes to the flavor of the wine and the “buttery” mouthfeel

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20
Q

Was beer invented or discovered

A

Discovered
- Mesopotamia 4000 BC

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21
Q

Production of traditionally fermented foods typically
relies on ____ microbiota, whereas commercial
fermentation generally relies on ________.
a) soil; edible
b) edible; indigenous
c) airborne; indigenous
d) indigenous; starter cultures
e) indigenous; chemicals

A

d) indigenous; starter cultures

22
Q

3 “special” microbes used to make “sour beer”

A
  • Brettanomyces (instead of Sacc.)
  • Lactobacillus
  • Pediococcus

Acetic acid and lactic acid
fermentation in addition to alcoholic
fermentation

23
Q

How is cheese made through fermentation (primary)

A

Primary fermentation with lactic acid bacteria
* lactose -> lactic acid: milk protein (Casein) insolube in the acidic environment and curdles = curds and liquid whey
* Curds = cheese

24
Q

Proteolytic enzyme (used in cheese making) that helps coagulate milk more efficiently and completely than acid alone

A

Rennet
* enzyme from 4th stomach of a calf

25
Q

secondary microbial processing of cheese

What is it used for; what do we use to do it

A

additional bacteria or molds are introduced to develop specific flavors and textures
* Propionibacter shermanii (swiss cheese)
* Penicillium camemberti (brie)
* Penicillium roquefortii (blue cheese)

26
Q

What is the top layer of many cheese considered

A

a biofilm
* cheeses have complex microbial communities

27
Q

How are pickled foods created without the use of vinegar

A

Acetic acid and lactic acid producing bacteria grow in a salty brine
e.g. pickles, sauerkraut, kimchi, etc.

28
Q

What microbial processed food is made using Aspergillus oryzae

A

Meju - soy based Korean Cooking Paste

29
Q

what microbial processed food is made using Bacillus subtilis

A

Natto - fermented soy beans

30
Q

What microbial processed food is made using Monascus

A

Red yeast rice - chinese food coloring

31
Q

Spirulina

A
  • Cyanobacterium
  • Highlighted as a superfood
  • Fish food
32
Q

Fusarium venenatum

A
  • Ascomycota fungus
  • Type of mold since its a filamentous fungus that grows hyphae
  • Used in the meat substitute Quorn
33
Q

Agaricus bisporus

A

Species of mushroom
* known as Cremini, portobello, baby bella, button mushroom, champignon mushroom
* Basidiomycota fungus

34
Q

2 species of mushroom that are commercially produced

A
  • Agaricus bisporus “portobello”
  • Pleurotus osteatus “Oyster mushroom”
35
Q

What is the genus name of “brewer’s yeast”

A

Saccharomyces

36
Q

What is the species name of “brewer’s yeast”

A

Saccharomyces cerevisiae

binomial nomenclature

37
Q

Bacterium that rots potatoes (and other fruits/vegs)

A

Erwinia carotovora (Enterobacteriaceae)
* storage issue - happens when stored improperly

38
Q

2 examples of fruit and bread molds that are fungi

A
  • Penicillium spp.
  • Rhizopus stolonifer
39
Q

example of a fruit and bread mold that is a bacterium

A

Serratia marcescens

40
Q

What molds grow on foods with a low pH

A

fungal molds (penicillium spp & Rhizopus stolonifer)
* Acidic foods: oranges, tomatoes

41
Q

What molds grow on food with a neutral or high pH

A

bacterial molds (Serratia marcescens)
* bread

42
Q

What are Aflatoxins & what do they cause

A
  • toxic compound produced by fungi - carcinogenic - causes liver damage and liver cancer
  • contaminate food before harvest or during storage
  • Frequently found in peanuts and corn
  • US FDA has strict limits on how much is allowed in food for human and livestock/animal consumption (recalls are common)
43
Q

Who produces Aflatoxins

A

Fungi
* Genus Aspergillus (Ascomycota)

44
Q

What is odd about the genus of Aspergillus and Penicillium

A

Both are involved in food production and cause spoilage
* Aspergillus is used to make soy-based cooking paste but also makes a toxic carcinogenic compound
* Penicillium is used in secondary fermentation of cheese but is also a spoilage causing fruit mold

45
Q

Ergot of Rye

A

disease affecting rye (cereal crops)

46
Q

What fungus causes Ergot of Rye

A

Claviceps purpurea

47
Q

When ergot-infected rye is consumed what does i cause

A

Ergotism (2 types)
* Convulsive ergotism: seizures, spasms, psychosis, nausea
* Vasoconstrictive ergotism: gangrene, edema, low BP

48
Q

Historical significance of Ergotism

A

St. Anthony’s Fire: Treatment for Erogtism outbreaks were to send ppl to the St. Anthony’s Monastery - Fire referred to the vasoconstrictive symptoms
* Improvements just came from reloaction and no longer being exposed to ergot
Salem Witch Trials: Some historians believe that hallucinations and other symptoms caused by ergot poisoning could have contributed to the witchcraft hysteria

49
Q

Modern significance of Ergotism

A
  • Vasoconstictive properties led to use of inhibiting post-partum bleeding and Migraine treatment
  • Synthetic development of hallucinatory compounds (LSD)
50
Q

When was LSD first created

A
  • First synthezised in 1938 by Sandoz laboratory
51
Q

LSD and the cultural revolution

A
  • counterculture of the 1960s was heavily influenced by LSD
  • LSD impacted the colors, clothing, art, ideology, and music

Microbiology (10 decks)

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