Food Micro - Exam 2 Flashcards
(316 cards)
1
Q
Bacteria reproduce through what when conditions are favorable?
A
Binary fission
2
Q
What is a positive outcome of bacteria reproduction?
A
Food fermentations
3
Q
What is a negative outcome of bacteria reproduction?
A
Spoilage or safety (dec. in food safety)
4
Q
Microbial growth is the equivalent of what?
A
Population size
5
Q
Describe the 5 steps of binary fission.
A
- Cell replicates its DNA
- The cytoplasmic membrane elongates, separating DNA molecules
- Cross-wall forms, membrane invaginates
- Cross-wall forms completely
- Daughter cells form
6
Q
Microbial growth is measured as growth in what?
A
Numbers (not necessarily size)
7
Q
Generation time equals what?
A
Doubling time (for microbial generations this is about 7 - 10 minutes)
8
Q
Generation time (doubling time) depends on what?
A
Conditions (environmental)
9
Q
Is generation time (double time) the same for each microorganism?
A
No, it is different for each.
10
Q
Why do we manipulate generation time (doubling time)?
A
To prevent spoilage or safety issues.
11
Q
What are some optimal conditions for growth of microorganisms?
A
Temperature, salinity, nutrients, etc.
12
Q
At what temperature do many foodborne pathogens prefer growth around?
A
37ºC
13
Q
Vibrio parahaemolyticus (usually found in salt water) has a typical generation time of what?
A
10 - 12 minutes
14
Q
Escherichia coli has a typical generation time of what?
A
15 - 20 minutes
15
Q
Bacillus cereus has a typical generation time of what?
A
28 minutes
16
Q
Staphylococcus aureus has a typical generation time of what?
A
27 - 30 minutes
17
Q
Mycobacterium bovis has a typical generation time of what?
A
960 - 1200 minutes
18
Q
Bacillus cereus and Staphylococcus aureus usually depend on what for their generation time?
A
Depend on environment
19
Q
Why do aerobic conditions speed up generation time for Bacillus cereus and Staphylococcus aureus?
A
Because they utilize oxidative phosphorylation.
20
Q
What three things paved the way for microbiology?
A
Fire, salt, and fermentation.
21
Q
Early cultures discovered that fire, salt, and fermentation could do what for foods and beverages?
A
Cook, cure, and reduce the pH of foods and beverages
22
Q
Define intrinsic factors.
A
Characteristics inherent to the food.
23
Q
What are the major intrinsic factors?
A
Nutrients
pH
Water activity
Antimicrobial
Biological structures
Redox potential
24
Q
Define extrinsic factors.
A
Characteristics that are external to the foods.
25
What are the major extrinsic factors?
Temperature
Relative humidity
Atmosphere
Byproducts of microbial activity
26
Growth of microorganisms occurs through what? (2 things)
What does this say about growth rate?
- Proliferation and metabolism
- Rates differ for microorganisms
27
Survival of microorganisms means what? (3 things)
- Injured -- viable but nonculturable
- Membrane integrity compromised (leaky cells)
- Slowed metabolism -- focus on repair
28
What is occurring during the lag phase of a microbial growth curve?
Adjusting to surroundings
29
What is occurring during the logarithmic/exponential phase of a microbial growth curve?
High metabolism rates
30
What is occurring during the stationary phase of a microbial growth curve?
Survival and death rates are roughly even within the population.
31
What is occurring during the death phase of a microbial growth curve?
Depletion of nutrients; unsuitable conditions
32
Which factors are not inherent to food?
Extrinsic
33
Which factors are characteristic of food?
Intrinsic
34
What are the 3 extrinsic factors we need to know for the exam?d
Temperature
Atmosphere
Relative humidity
35
What are the 6 intrinsic factors we need to know for the exam?
Nutrients
pH
Water activity
Oxidation/reduction potential
Antimicrobials
Biological structures
36
Hurdle technologies are what?
Additive and synergistic
Hurdle technologies are what we actively do to intervene.
37
In what foods do we need control of pH and atmosphere? (Hurdle technologies)
Fermented foods
38
In what foods do we need control of aw and pH? (Hurdle technologies)
Jams and jellies
- In regard to pH, fruits are naturally acidic.
39
If we add sugar to fruits to make jams/jellies what will occur?
Sugar will bind to H2O and reduce water activity.
40
In what foods do we need control of pH and temperature? (Hurdle technologies)
Range of perishable and shelf-stable foods
41
In what foods do we need control of temperature and use of bacteriocins/organic acids? (Hurdle technologies)
Yogurt and other fermented dairy products
42
What are psychrophiles?
Microorganisms that grow in 0 - 20ºC conditions (they love the cold)
43
What are psychrotrophs?
Microorganisms that grow in 20 - 30ºC conditions (fridge temp).
Capable of less than or equal to 7ºC
44
What is an example of a psychrotroph?
Listeria monocytogenes
45
What are mesophiles?
Microorganisms that grow in 30 - 40ºC conditions.
Capable of 20 - 45ºC.
46
What is an example of a mesophile?
E. Coli and Salmonella
47
What are thermophiles?
Microorganisms that grow in 55 - 65ºC conditions.
Capable of greater than or equal to 45ºC.
48
Most microorganisms grow in what temperature zones?
Psychrotrophic and mesophilic temperature zones.
49
What is the temperature danger zone?
40 - 140ºF (5 - 60ºC)
50
Cooling rates impact what?
Microorganism growth rate
51
Cooling rates vary by what?
Food types and amount
52
Cooling rates impact microorganism growth rate by impacting what?
Membrane fluidity
53
Can cooling rates alter virulence?
Yes, there is reduced expression of virulence genes at reduced temperatures and enhanced expression of virulence at optimal growth temperatures.
54
What microorganisms serves as an example of cooling rates altering virulence?
Listeria monocytogenes
55
Microorganisms require what specific conditions for growth?
Atmospheric conditions
56
What are some obligate aerobes?
Pseudomonas
Molds
Bacillus Cereus
57
What are some facultative anaerobes?
Listeria monocytogenes
Salmonella
E. Coli
58
What are some obligate anaerobes?
Clostridium spp.
59
What are some aerotolerant anaerobes?
Lactobacilli
60
What are some microaerophiles?
Campylobacter jejuni
61
We can manipulate O2, N2, and CO2 content to what?
Restrict growth
Inactivate microorganisms
62
What are 3 examples of controlling the extrinsic factor atmosphere?
Vacuum-packaging
Modified atmosphere packaging
Controlled atmosphere storage
63
What does vacuum packaging help with?
It slows spoilage and controls oxidation
64
What does modified atmosphere packaging help with?
It increases CO2 levels (by 7 - 10%) and decreases O2 levels (to less than 1%).
65
What is an example of a food that we use modified atmosphere packaging in order to control its atmosphere?
Lettuce
66
What does controlled atmosphere storage help with?
It allows for control O2 levels (3%) and controlled CO2 levels (3%).
67
What is an example of a food that we use controlled atmosphere storage in order to control its environment?
Apples
68
What are some nutrients that affect microorganism growth?
Water and energy sources (such as carbon, sugar, nitrogen, and phosphorus)
- energy sources affect enzymatic activity
- these include macro and micronutrients
69
Are nutrients in some foods more accessible than others?
Yes
70
What is one way nutrient availability is impacted?
By processing (slicing, macerating, inclusions)
71
What is another way nutrient availability is impacted?
By competition (starter cultures will out-compete pathogens in fermented foods)
72
pH is a measurement of what and is measured on a scale of what?
A measurement of acidity
0 - 14
pH = -log [H+]
73
Moth pathogens require what pH range for growth?
pH greater than or equal to 4.4 - 4.6
(however, some spoilage microorganisms can grow in acidic foods)
74
What is an example of a spoilage microorganism that can grow in acid foods?
Lactic acid bacteria (LAB)
75
Foodborne microorganisms prefer what pH range?
6 - 7 pH
76
What microorganism can grow as low as 4.4 pH?
Clostridium botulinum
77
What are the 5 major effects of pH on microorganisms?
1. undissociated acid crosses membrane
2. acid dissociates within cytoplasm
3. anion can disrupt cellular function
4. more cellular energy spent to maintain intracellular balance (F-ATPase system and passive diffusion of H+)
5. Dissociated acid cannot cross membrane when charged
78
Low-acid foods are commonly associated with what?
Outbreaks
79
Low-acid foods means what?
pH on the higher end (around neutral)
80
Adding acid to lower pH will result in what?
Acidified foods
- ex: cucumbers pickled with acetic acid
81
Acid foods have a naturally low pH of what?
Less than 4.6 pH
82
Define antimicrobials.
Substances natural to the foods with inhibitory or inactivating properties.
83
What are some examples of antimicrobials?
Bacteriocins
Organic acids and iso-a-acids (hops)
Essential oils --> thyme oil, eugenol, allicin
Enzymes --> lysozyme
84
How does a lysozyme exert antimicrobial activity?
It is found in the peptidoglycan in the cell wall and disrupts the cell (hydrolyzes beta linkages).
It is effective against gram-positive bacteria.
85
The Lactoperoxidase system exerts what intrinsic activity?
Antimicrobial activity
86
What is the lactoperoxidase system?
A naturally occurring inhibitory system in milk
87
What does the lactoperoxidase system consist of?
Lactoperoxidase
Thiocyanate
Hydrogen peroxide (in natural amounts)
- However, there is typically additional thiocyanate and hydrogen peroxide added
88
What is the lactoperoxidase system inhibitory to?
Effective against gram-positive and negative microorganisms
89
What can the lactoperoxidase system do to the shelf life of milk?
Can extend shelf life from 2 - 5 days
90
The lactoperoxidase system works synergistically (cooperatively -- both benefit) with what two enzymes?
Lactoferrin and lysozyme
91
Oxidation / Reduction potential (Eh) is the measure of what?
The measure of tendency to gain or lose electrons
92
What does it mean for something to be reduced?
To have negative electric potential.
To favor anaerobic growth.
93
What does it mean for something to be oxidized?
To have positive electric potential.
To favor aerobic growth.
94
Eh changes within a food based on what 3 things?
Microorganism growth (resulting in respiration)
Processes that impact the atmosphere (M
Cooking / heating (forces oxygen out)
95
Anaerobes need what type of environment?
Reduced environment
96
Aerobes need what type of environment?
Oxidized environment
97
Define water activity.
The ratio of free, available water within a food.
98
What does available water mean?
Available for use by microorganisms
99
An aw (water activity) of 0.0 means what?
Bone dry
100
An aw (water activity) of 1.0 means what?
Pure water
101
Water activity greatly impacts what 3 things?
Physical characteristics of food
Chemical reactions
Microbial growth
102
Most bacteria have what type of water activity?
Fairly high water activity (0.91 - 0.88 at 25ºC)
103
What can grow at lower water activites?
Mold (but needs a little higher water activity in order to produce toxin)
104
How does lower water activity affect shelf life?
It allows for longer shelf life
105
How does higher water activity affect shelf life?
It causes shorter shelf life
106
What is the mechanism behind water activity?
Movement of water molecules from high to low aw.
This is known as osmotic stress.
107
What is the measurement of water activity and how do you measure it?
Ratio of free, available water within a food
Equilibrate liquid-phase water in sample to vapor-phase water in headspace
(Relative humidity is measured to indirectly determine water activity)
108
What are some consequences of osmotic stress that can challenge the food industry?
Dormancy
Filaments (elongation without separation until more favorable conditions)
Cross-protection (same protein used to respond to multiple stresses)
109
What is the typical aw (water activity) of fresh, raw fruits, vegetables, meat, and fish?
Greater than 0.98 (this is a high water activity)
- Usually high water activity constitutes greater than 0.95
110
What is the typical aw (water activity) of cooked meat and bread?
0.95 - 0.98
111
What is the typical aw (water activity) of cured meat products and cheeses?
0.91 - 0.95
112
What is the typical aw (water activity) of sausages and syrups?
0.87 - 0.91
113
What is spoilage?
Physical, chemical, enzymatic or biologcial changes
114
Spoilage can be the result of biological changes caused by what?
Bacteria, yeasts, or molds
115
What can prevent spoilage?
Extrinsic / intrinsic factors can be manipulated to extend the shelf life
Addition of preservatives
Prevention of exposure to spoilage microorganisms
116
Antimicrobials do what?
Inhibit microbial growth with bacteriostatic action
117
Bacteriostatic action does what?
Prevents multiplication
118
Antimicrobials also act as?
Biological preservation
119
What are some examples of antimicrobials?
NaCl
Acids
Nitrites
Phosphates
Sulfites
Lysozyme/lactoferrin/lactoperoxidase system
120
What is an example of antimicrobial inhibition?
Organic acids to treat produce
121
How do acids exert antimicrobial activity?
Manipulation of pH
122
Do weak acids have more effective antimicrobial activity and why or why not?
Yes, because they are able to dissociate within the cytoplasmic membrane.
123
What are preservatives?
A food additive that may:
- reduce or prevent browning
- reduce or prevent oxidation (antioxidant)
- stabilize the food formulation
- serve as an antimicrobial agent
124
Are preservatives bacteriostatic (prevents multiplicaiton)?
Yes
125
Traditional preservatives and antimicrobials can be?
Naturally derived or synthetically made
126
Do all preservatives have to be approved for use?
Yes
127
Natural antimicrobials or preservatives are:
From natural sources
Organic
Generally fit the clean label
128
What is clean labeling?
Based on the idea that consumers are intimidated by technical language
129
Give an example of clean labeling.
Saying "celery powder" instead of "nitrites"
130
How can you determine if there is spoilage?
Changes in sensory attributes that make the food unacceptable to the consumer
131
What are the 5 changes in sensory indicating spoilage?
Taste: sour, bitter, putrid
Texture: mushy, slimy
Smell: FAs, esters, aldehydes
Appearance: discoloration, structural
Sound: think "chips or popcorn"
132
Determine spoilage: <10^6 bacteria
Microbial spoilage generally not recognized
133
Determine spoilage: 10^6 - 10^7 bacteria
Some foods show early stages of changes
134
Determine spoilage: 10^7 - 10^8 bacteria
Spoilage associated with most foods
Off colors associated with meats and vegetables
135
Determine spoilage: 10^9 bacteria
Almost all foods display obvious indications of spoilage
136
Determine spoilage: >10^9 bacteria
Obvious structural changes
137
Lower water activity and lower pH usually mean what?
Longer shelf life --> less spoilage
138
What is the origin of spoilage microorganisms in red meat?
Hide / hair
Hooves
Mouth
Intestines
139
What are the typical spoilage microorganisms in red meat?
Staphylococcus
Micrococcus
Pseudomonas
Lactic acid bacteria (LAB)
Yeasts
(all of these microorganisms can tolerate or require oxygen)
140
What does it mean for meat to be comminuted?
Ground / combined
141
How does spoilage occur in comminuted meat?
Contamination during processing
Distribution of contaminants
Increased surface area = increased nutrient availability
Mixture of environment (aerobic and anaerobic)
142
A higher microbial load means what in regard to shelf life?
A shorter shelf life
143
What is the origin of spoilage microorganisms in poultry?
Skin
Feathers
Feet
Intestines
Litter
Transportation
144
What are the typical spoilage microorganisms in poultry?
Clostridium estertheticum (formerly Laramie) --> causes sulfide odor --> terrible for spoilage because forms spores
Pseudomonas
Lactic acid bacteria (LAB)
145
What is the origin of spoilage microorganisms in seafood?
Environment
Storage facility
Workers
146
What is the typical spoilage microorganism in seafood?
Pseudomonas (a psychrotroph) --> able to process the high protein / low carb content --> important for fish
147
Do spoilage microorganisms in seafood vary by water?
Yes
148
What are the typical cool water spoilage microorganisms?
Psychrotrophs (specifically pseudomonas)
149
What are the typical warm water spoilage microorganisms?
Mesophiles (specifically bacillus and micrococcus)
150
Active spoilage in produce is due to what?
Plant pathogens
151
Passive spoilage in produce is due to what?
Opportunistic pathogens (wound - induced)
152
What are some primary components of spoilage microorganisms in produce?
Cellulose
Pectin
Cutin
(degradative enzymes produced to break down components)
153
What are some examples of degradative enzymes produced to break down components in produce?
Pectinases produced by Botrytis cinerea
Penicillium spp
Erwinia carotovora
154
Is post-harvest mold due to wounds in produce?
No, it can occur with or without wounds
155
Erwinia carotovora is a spoilage microorganism in produce that causes what?
Soft rot
Damaged tissues allow invasion by Erwinia
- to prevent this you need to scrub potatoes
- passive spoilage because through damaged tissue (through wound)
156
What organization prevents spoilage in produce?
Good Agricultural Practices (GAPs)
157
What does GAPs do to prevent spoilage in produce?
Control of land, water, and air
Post-harvest processes --> washing (acts as control, not necessarily an intervention)
Temperature
Atomosphere
158
What does GAPs do to prevent spoilage in produce?
Control of land, water, and air
Post-harvest processes --> washing (acts as control, not necessarily an intervention)
Temperature
Atmosphere
159
Is the spoilage rate different for organic produce?
No, same for organic and non-organic produce
Fresh produce = no GMOs (people think it lasts longer but this is not true)
160
Grain is a dry, desiccated product, which means what about its water activity?
It has a low water activity (aw < 0.65)
161
What happens when condensation is present in grain?
Molds gain foothold --> mycotoxin production
- specifically Aspergillus mold
162
How can we prevent spoilage in grains?
Milling and grinding reduces microbial load
Control of storage conditions
Extrusion
163
What are signs of spoilage in breads and pastries?
Presence of yeast and mold
164
How can we prevent spoilage in bread and pastries?
Preservatives
Storage conditions (controlled humidity)
165
What is the typical shelf life of milk?
10 - 15 days if heated properly to eliminate most vegetative bacteria (pathogens)
Higher protein milk and soy milk = longer shelf life because lactose free
166
Spoilage after shelf life in milk occurs because of what?
Psychrotrophs
167
Specifically what spoilage microorganisms/mechanisms typically spoil milk after shelf life?
Lactic acid bacteria (heterofermentative) --> acetic acid
Proteolytic metabolism --> roping and clotting
168
How must raw milk be preserved?
Must be chilled to 7ºC within 2 hours after milking, never to exceed 10ºC
169
Why is raw milk very susceptible to spoilage?
Because it contains several microorganisms, and when it comes out, it is already in the temperature danger zone
Raw milk = never safe --> should be pasteurized
170
What is the oldest known antimicrobial preservative?
Sodium chloride (NaCl)
171
Sodium chloride is known to cause what?
Plasmolysis --> cell shrinkage due to presence in a hypertonic solution (more solutes in external solution than inside cell)
172
Sodium chloride can combine with other hurdles such as:
desiccation, heat, etc.
173
Sodium chloride inhibits foodborne pathogens at what percentage and water activity?
13% and aw = 0.90
174
How does sodium chloride prevent food spoilage?
Generally bacteriostatic (prevents multiplication of bacteria) by prompting plasmolysis
L. monocytogenes can survive in salt solution (NaCl causes plasmolysis)
Staphylococcus aureus can grow at aw 0.83 if other conditions are right (NaCl has aw = 0.90)
175
List the antimicrobial organic acids from most preventative to least.
Acetic > propionic > lactic > citric
- efficacy impacted by lipophilic nature
176
How do organic acids prevent spoilage?
Cross cell membrane into cytoplasm (molecule must be protonated and uncharged)
177
What happens when the pH of food is higher than pKa of organic acid?
The molecules dissociate and organic acid cannot cross membrane
178
Benzoates are antimicrobials that are commonly used as what and function best at what pH?
Commonly used as sodium or potassium benzoate
Functions best at lower pH (< 4.0)
179
How do benzoates prevent spoilage?
Forms benzoic acid, which enters cell like other acids
180
Benzoic acid is present in what foods?
Apples
Blackberries
Cranberries
Tomatoes
Cultured dairy products
Cinnamon
181
What is the first chemical preservative approved by FDA?
Benzoic acid
182
What are 3 common parabens?
Methyl
Propyl
Heptyl
Parabens = alkyl esters of para-hydroxybenzoic acid
183
How do parabens (antimicrobials) prevent spoilage?
Act on membrane, reduces fluidity
Leads to DNA damage and prevention of replication
184
What is the effective range pH for parabens?
pH 3 - 8
Remains in the undissociated form up to pH 8.5
185
Parabens are most effective against what?
Molds and yeasts (antifungal)
Attacks membrane and causes leakage
186
What are parabens used for?
Baked goods
Beverages
Fruit products
Syrups
Salad dressings
Fermented foods
187
Nitrites (antimicrobials) are present in what?
Leafy greens and root vegetables
188
Nitrites are used as a what for meats?
Curing ingredient for meat (bacon, hot dogs, and ham)
Adds pink color and flavor profile
189
Nitrites are effective at what pH and oxygen requirement?
Effective at low pH and anaerobic environment
190
Nitrites are paired with ascorbate to inhibit what microorganisms? How do they inhibit?
C. botulinum and L. monocytogenes
Interfering with cell wall synthesis, breaking apart nucleotides, derivatives (enzymes and proteins) can disrupt metabolism
191
Sorbates (an antimicrobial) are commonly used as what?
Potassium sorbate
192
Sorbates are effective at what pH?
pH < 6.5
193
Sorbates are antifungal and antibacterial but not against what? And how?
Fermenters
Disrupts membrane, induces oxidative stress (DNA damage)
194
Sorbates are used in what products to prevent spoilage?
Fermented products
Fruit products
Carbonated and fruit beverages
195
How do sulfites (antimicrobials) prevent spoilage?
Targets cytoplasmic membrane, DNA replication, protein synthesis and enzymes
196
Why are sulfites used in wines?
To allow for malolactic fermentation without inhibiting fermentation of yeasts
Also used in vegetable and fruit products
Antioxidant to prevent browning
197
The effectiveness of sulfites is dependent on what? When are they active?
pH and form
Active when undissociated
198
Lysozymes (antimicrobials) are present where?
Milk
Eggs
Tears
199
How do lysozymes prevent spoilage?
They are heat stable
They target cell wall by breaking down peptidoglycan
Effective against gram (-) and (+), but more effective against gram (+)
200
Lactoferrin (an antimicrobial) is present where?
Milk
201
How does lactoferrin prevent spoilage?
Binds iron and limits growth of pathogens that require high iron levels
(i.e. Clostridium, E. Coli, listeria, Pseudomonas, salmonella)
202
Lactoperoxidase system (antimicrobial) is naturally present where?
Milk
Can be enhance with increasing concentrations of components
203
How does the lactoperoxidase system prevent spoilage?
Works synergistically with lysozyme, lactoferrin, and hydrogen peroxide
204
What is the main concept regarding oxidative phosphorylation?
Oxygen serves as terminal electron acceptor and yields energy.
205
What is the main concept regarding fermentation and what byproducts does it yield?
No oxygen in fermentation, so sugar will receive electron and is partially oxidized.
- yields some energy and incompletely oxidized byproducts (lactic acid, acetic acid, ethanol, etc.)
206
Fermentation is an anaerobic process that produces a number of what byproducts?
Acetic acid
Lactic acid
Alcohol
Gas (CO2)
207
Fermented foods provide advantages for what 3 things?
Preservation: longer shelf life by preventing spoilage
Safety: byproducts influence intrinsic factors
Nutrition: nutrient availability, beneficial byproducts
208
What are the key players in fermentation?
Lactic acid bacteria
Yeasts
(They will need to be tolerant of oxygen until fermentation where they will then be deoxygenated)
209
When did fermentation of cheese begin?
> 7,000 years ago in Mediterranean
210
When did fermentation of beverages begin?
7,000 years ago in Babylon
211
When did fermentation of breads begin?
> 5,000 years ago in Egypt
212
When did fermentation of vegetables begin?
3,500 years ago in China
213
What is the primary byproduct for alcoholic fermentation with yeasts? Give an example of this process.
Alcohol can be main or secondary byproduct
- ex: bread leavening by yeasts
- ex: ethanol evaporates during baking
214
Fermentation of lactic acid occurs in what products?
Dairy products
Bread
Fermented vegetables
215
Lactic acid fermentation does what to acidity?
Lactic acid increases acidity (increased acid, decreased pH)
216
What flavor profile does lactic acid fermentation create?
Sour flavor profile
217
Different pathways in lactic acid fermentation produce what?
Lactate (each lead to a variety of end products)
218
What is a major fermenter in fermentation process of lactic acid?
Lactic acid bacteria
219
There is a large group of fermenters in fermentation of lactic acid, what are they?
Lactobacillus
Leuconostoc
Pediococcus
Lactococcus
220
What is/are the byproducts of homofermentative (homolactic) fermentation?
Primary byproduct is lactic acid
221
What is/are the byproducts of heterofermentative (heterolactic) fermentation?
Multiple byproducts
222
Homolactic fermentation mostly produces lactic acid with the help of what fermenters?
Lactococcus
Pediococcus
Streptococcus
Some lactobacillus
223
Give an example of homolactic fermentation.
Fermented meats and vegetables
224
Heterolactic fermentation produces multiple byproducts with the help of what fermenters?
Lactobacillus
leuconostoc
225
What are some of the multiple byproducts of heterolactic fermentation?
Acetic acid
Propionic acid
Carbon dioxide
Acetaldehyde
226
Heterolactic fermentation allows for what?
Flexible use of sugars
More flavor profiles
(is able to multitask)
227
Give an example of heterolactic fermentation.
Vegetables
Yogurt
Sourdough bread
228
Natural/native starter cultures are derived from where?
The environment
Considered "wild"
229
Fermentation of starter cultures causes what to occur between batches? Give an example.
Variablility
- ex: sourdough bred at farmers market
230
What is back-slopping in starter culture fermentation?
Using a part of a finished product to start the new
Some consistency
- ex: sourdough
231
Designed or lab-grown starter cultures are present where?
In proprietary blends
232
Designed or lab-grown starter cultures are genetically enhanced for what?
Flavor compounds or performance
233
Designed or lab-grown starter cultures have what consistency?
Highest consistency
234
What does the clarification step in the dairy fermentation process do?
Removes sediment (leukocytes that may contain Listeria monocytogenes)
235
The formulation step in dairy fermentation depends on what?
The end-product
236
Pasteurization removes what from diary?
Unwanted bacteria
237
What does the homogenization step of dairy fermentation do?
Prevents ingredient separation during fermentation
238
What are some key fermenters in milk fermentation in yogurt?
Streptococcus thermophilus
Lactobacillus bulgaricus
Acidophilus
Bifidobacterium spp.
239
What does milk fermentation in yogurt do to lactose (milk sugar)?
Decreases lactose content and forms lactic acid
240
What does the lactic acid do to the milk (in yogurt)?
- Lowers pH (drops to about 4.8 when done; safe to consume, but less than or equal to 4.6 is no longer safe)
- Causes protein denaturation
241
What happens to casein during milk fermentation in yogurt?
It is broken down and reassembles (coagulation)
242
What are the key byproducts in milk fermentation in yogurt?
Acetaldehyde
Aromas
Bacteriocins
Acid
243
What are the 7 factors affecting microbial growth during cheese fermentation?
- starter cultures and byproducts
- pH and organic acids
- Redox potential
- Nutrients (sugars, proteins)
- Water activity (water and salt concentration)
- Temperature
- Bacteriocins
244
What decreases throughout the cheese fermentation process?
Microbial diversity
245
Starter cultures in cheese are capable of what?
Metabolizing lactose and casein
246
What are common in cheese fermentation?
Homolactics
247
What provide flavor in cheese fermentation?
Heterolactics (specifically diacetyl, CO2)
248
What are the 4 major steps in cheese fermentation?
1. Milk
2. Cultures
3. Rennet (protease enzyme)
4. Salt
249
How does coagulation during cheese fermentation?
Microbes and enzymes hydrolyze casein
250
Cutting curd during cheese fermentation does what?
Increases microbial activity by increasing surface area
251
Cooking during the cheese fermentation process does what?
Selects for specific enzymatic and microbial activity
252
Salting during the cheese fermentation process does what?
Reduces moisture and brines
253
Aging of cheese is what type of process?
Controlled process (controlled through temperature and humidity)
254
What are some examples of inedible cheese rinds?
Wax
Paper
Bark
255
What are some examples of edible cheese rinds?
Bloomy (snowy white, ripened by mold --> ex: Brie, Camembert)
Washed (reddish-orange, from bacteria Brevibacterium linens)
Natural (hard layer --> ex: cheddary, parmesan)
256
Molds can also be used for what in cheese fermentation?
Veining (poke holes where oxygen can promote growth of mold)
- ex: Penicillium roqueforti
257
Where does the microbiome of raw milk come from?
Teats
Handlers
Environment
Equipment
258
Raw milk is exposed to what specific pathogens?
Brucella abortus
Campylobacter spp.
E. Coli
Salmonella
Listeria monocytogenes
Staphylococcus aureus
259
Raw milk is responsible for many outbreaks such as what?
Typhoid fever
Salmonellosis
Campylobacteriosis
Brucellosis
260
Cheeses made from raw milk are regulated through what process?
Aging process
261
What is the standard aging requirement according to 21 Code of Federal Regulations (CFR) section 133?
Requires 60 days aging at > 35ºF (this is based on earlier data from > 60 years ago)
262
What two microorganims can survive for longer periods of time when it comes to cheese aging?
Salmonella
E. coli
263
Native microorganisms on surface of produce (vegetables) offer what?
Diversity
264
Lactic acid bacteria in vegetable fermentation is tolerant to what?
Salt and anaerobic environment
(Metabolism and byproducts make them good competitors)
265
What is the final pH after vegetable fermentation?
Usually below 4.6
266
Give an example of vegetable fermentation.
Cabbage
Cucumbers
Olives
267
What are the 5 steps of vegetable fermentation?
1. Start with healthy vegetables
2. Pretreat if necessary (washing, blanching, cooking)
a. additional processing such as slicing, cutting, or
maceration
3. Place into fermentation vessel
a. additional optional ingredients (salt, starter cultures)
4. Submerge and cover vegetables with brine
5. Allow fermentation to take place, checking at points to determine product readiness
268
What are the main fermenters in fermentation of Sauerkraut (cabbage)?
Microbial succession of:
Leuconostoc mesenteroides
Lactobacillus plantarum
Lactobacillus brevis
269
What is the final pH after cabbage fermentation?
3.8 - 4.1
270
What are the main fermenters in pickle (cucumber) fermentation?
Lactobacillus plantarum (homofermentative)
Heterofermentative LAB (may cause floaters)
271
Pickle (cucumber fermentation) occurs via?
Natural fermentation
272
What is the final pH of pickle (cucumber) fermentation?
3.7
273
What does the color of olives indicate?
Green = unripe
Black = ripe
274
What are the main fermenters in olive fermentation?
Pediococcus spp.
Leuconostoc mesenteroides
Lactobacillus plantarum
Brevis
275
How must unripened olives be treated? And how long is fermentation?
Must be treated in 2% NaOH to remove oleuropein (antibacterial compound)
Long fermentation ( > 1 month)
276
How must ripened olives be treated? And how long is fermentation?
May not require NaOH solution (depends on targeted flavors)
shorter fermentation ( > 2 weeks)
277
Olives are washed and placed where for fermentation?
In brine (5 - 10 % NaCl)
278
What are the steps for fermentation of meats?
1. Grinding raw meat
2. Blended with ingredients (salt, nitrites, spices)
3. Package
4. Incubate for fermentation
5. Final heating step
6. Dry Package
279
What are the starter cultures present during meat fermentation and what conditions can they grow in?
Pediococcus acidilactici
Can grow at higher temperatures (43 - 50 ºC)
Can grow at high salt concentration (about 6%)
Added sugars can promote growth
280
If fermented sausages are shelf-stable they must include what ingredients that inhibit growth of microorganisms?
Nitrites / curing agents
Acid (pH < 5.0)
Specific moisture to protein ratio (3.1 : 1.0)
281
Cocoa beans contain what type of coating?
Mucilaginous coating with sugars
282
What does this mucilaginous coating on cocoa beans mean for fermentation?
Beans with mucilage are fermented in piles by native microbes (2 - 8 days)
283
Where are cocoa bean pods located?
theobroma cacao in tropic regions (South America and Western Africa)
284
A careful drying process is required to end cocoa bean fermentation with what?
The right flavor profile and moisture content
285
What are the 6 steps of chocolate processing in cocoa bean fermentation?
1. Roasting (preservation and flavor)
a. Rapid (high heat, strong flavors)
b. Slow (low heat, subtle flavors, floral notes)
2. Milling (grinding into chocolate liquor (no alcohol)
3. Pressing (separate cocoa powder from butter)
4. Conching (kneading / smoothing of liquor, releases flavors)
5. Tempering (controlled heating process to develop cocoa butter crystals that result in smooth, shiny surface)
6. Molding (pouring liquid chocolate into molds for shaping)
286
What are the main fermenters in coffee bean fermentation?
Coffea arabica
C. canephora
C. robusta
287
Coffee bean fermentation with native LAB will remove what?
The mucilaginous layer
(Last thin layer of cellulose and remaining microbes are washed away with water)
288
Extended fermentation of coffee beans may allow for what?
Yeast and molds to compete with LAB and spoil product
289
What are the coffee processing steps?
1. Drying (following fermentation to drop moisture to 11%)
2. Roasting (develop flavor profile)
3. Grinding and brewing
290
What is Kopi Luwak?
Fermentation of beans within digestive tract of Asian palm civet
291
What is the basis of yeast fermentation?
Processes carbohydrates / starchy grains to leaven and produce flavor
292
What is the most common grain?
Wheat flour
Gluten formed from glutenin and gliadin; developed during kneading, provides structure and elasticity
293
What is the most common yeast for bread fermentation?
Saccharomyces cerevisiae
294
What is the main byproduct of Saccharomyces cerevisiae during bread fermentation?
Carbon dioxide (about 40% expansion)
295
Yeast fermentation produces what two byproducts?
Ethanol (vaporized during baking)
CO2 (yields bubbles and gives structure)
296
What does proofing during bread fermentation consist of?
Temperature (27ºC)
Humidity
Time
297
Sourdough bread uses a mixture of what?
Yeast and LAB
298
The acidic and tangy flavor profile in sourdough is due to what?
The byproducts
299
San Francisco sourdough consists of what specific yeast and bacteria mixture?
Yeast: Candida milleri
Bacteria: Lactobacillus Sanfrancisco
(blend used continuously for > 140 eyars)
300
What byproducts will pyruvate yield in beverage fermentation?
CO2
Ethanol
Some acids
301
Wine and beer have a variety of what fermenters?
Varieties of yeasts
302
Kombucha is fermented with what?
SCOBY (symbiotic culture of bacteria and yeasts)
303
What are the benefits of beverage fermentation?
Preservation
Nutrients
Safety
Recreation
304
Fermentation is mainly affecting what intrinsic factor?
Nutrients
305
What are the 5 steps in beer production?
1. Malting (part affecting nutrients)
2. Mashing
3. Wort boiling
4. Fermentation
5. Postfermentation processing
306
Beer uses the same yeast as bread but is looking for what byproduct instead?
Alcohol
307
What are hops and what do they do during beer fermentation?
Hops = flower cones of hop plant
Provide aroma, bitterness, antimicrobial effects for alpha - acids
308
Yeast used in beer fermentaion depend on what?
Style of fermentation and temperature
309
What type of yeast is used for top yeast fermentation (warmer brew)?
Saccharomyces Cerevisia
310
What type of yeast is used for bottom yeast fermentation (colder brew)?
Saccharomyces uvarum
(S. eubayana and S. pastorianus are also good for colder temperatures)
311
Secondary fermentation is additional fermentation that will require more what?
Nutrients and microbes
312
What are the two types of beet fermentation?
Top fermentation (warmer brewing temps)
Bottom fermentation (colder brewing temps)
313
What are the antimicrobials present in beer?
Ethanol
CO2
Hops
314
Spoilage in beer is due to?
Wild and aerobic yeasts
315
What are some safety methods used during beer fermentation to prevent from spoilage?
Pasteurization
Cold pasteurization
Antimicrobial hurdles
316
If we see Saccharomyces before adding actual yeast during beer fermentation what does this indicate?
This indicates that we have a problem
(should not be added until after adding yeast)
