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Discussion Topics Flashcards

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1
Q

[8.1] What are the different types of diluents for different purposes?

A
  1. General purpose
  2. Anaerobic microbes
  3. Osmophilic and halophilic
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2
Q

[8.1] Content of general purpose diluent

A

0.1% peptone and 0.85% NaCl

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3
Q

[8.1] Content of anaerobic microbe diluent

A

Diluents that are capable of keeping redox potential as low as possible

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4
Q

[8.1] Content of osmophilic microbe diluent

A

20% sterile sucrose

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5
Q

[8.1] Content of halophilic microbe diluent

A

15% sterile NaCl diluent

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6
Q

[8.2] Sampling method for liquids

A

Large samples (100-500mL) should be mixed ina sterile container, then mixed once again before analysis

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7
Q

[8.2] Sampling method for solids

A

Done in small quantities; if the object is large must be done in multiple locations. For meats and perishable foods, sampling must be done in both the deep part and the surface

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8
Q

[8.3] Types of sampling methods for sample surface

A
  1. Surface slides
  2. Rinses and washes
  3. Swabs
  4. Impression techniques
  5. Adhesive tape
  6. Agar sausage
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9
Q

[8.3] Surface slide mechanism

A

Slicing layers of food thinly with forceps and scalpels

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10
Q

[8.3] Rinse and wash mechanism

A

Done in sterile diluents; the initial washing is considered the initial 0.1 dilution
good for small objects (e.g. sausage/veg)

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11
Q

[8.3] Swab mechanism

A

Surface swabbed and mixed with diluents; diluted microbed then transfered into medium for incubation

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12
Q

[8.3] Impression technique mechanism

A

Medium impressed irectly to sample

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13
Q

[8.3] Adhesive tape mechanism

A

Tape is impressed to sample then to the media (tapes and adhesives are self sterilizing after manufacture)

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14
Q

[8.3] Agar sausage mechanism

A

Impressing the end of agar sausage to the sample, then sliced and placed onto a petri dish

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15
Q

[8.4] Qualitative analysis is done based on what reactions?

A
  1. Biochemical reaction
  2. Enzymatic reaction
  3. Redox potential reaction
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16
Q

[8.5] Test for presence of active enzymes

A
  1. Catalase test
    Identify organisms that produce catalase
    Uses H2O2 (H2O2 -> H2 + O2)
    Positive results, bubbles formed
  2. Oxidase test
    Identify organisms that can produce catalase oxidase
    Positive results, deep purple color
  3. Coagulase test
    Identify organisms that produce coagulase
    Positive results, clumping
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17
Q

[8.6] Explain DMC

A

Quantitative analysis that gives an estimate of actual organism number under the microscope at microscopic factors (MF) 300000-600000

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18
Q

[8.7] Adv and disadv of DMC

A

(+) rapid, can be stained to be read later, minimum equipment, Gram strain type can be identified
(-) only if amount is large, but small quantity is examined so small precision, debris may eb present, analyst fatigue reduces precision

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19
Q

[8.6] Types of DMC

A

THOMA
(no. in 100 sq x 1/0.25 x 1/0.1 x 1000)

Petroff Hauser
(no. in 80 sq x 1/0.2 x 1/0.02 x 1000)

Neubauer
(no. in 80 sq x 1/0.2 x 1/0.1 x 1000)

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20
Q

[8.8] How to count plates in CCM

A

*FOR POUR PLATE

(n1 + 0.1*n2) x V x D

n1: no of dishes retained in first dilution
n2: no of dishes retained in second dilution
d: dilution factor of first dilution

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21
Q

[8.8] Type of Colony Count Methods

A
  1. Total Plate Count/Aerobic Mesophilic Count (TPC)
  2. Mold and Yeast Count (MYC)
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22
Q

[8.8] Incubation temp for pour plate method

A

1-10 C psychrotrophs and psychrophiles

20-32 C saprophytic mesophiles

33-37 C Parasitics and commensals of homoiothermic animals

55-63 C thermophiles

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22
Q

[8.8] Colony count on each TPC plate

A

ISO 10-300

BAM FDA 25-250

MYC 10-150

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23
Q

[8.9] Detection of positive results in MPN

A
  1. Turbidity
  2. Metabolic end products
    - gas production
    - detection of acid/base
    - reduction methods (color change)
    - others (NO3 reduction, indole production, starch hydrolysis, H2S production)
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24
Q

[8.10] Why is dilution needed in CCM

A

To reduce amount of colonies so that the counting process is easier

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25
Q

[9.1] What are the four types of fermentation

A
  1. Alcoholic
    1 glucose -> 2 ethanol + 2 ATP + 2 CO2
    e.g. wine, beer (Saccharomyces)
  2. Acetic acid
    ethanol -> acetic acid
    e.g. Vinegar (escherichia, acetobacter)
  3. Lactic acid
    homo: glucose -> 2 lactic acid
    hetero: glucose -> 1 lactic acid, ethanol, CO2
    e.g. cheese, yogurt, soy sauce (aspergillus, lactobacillus, streptococcus)
  4. Alkaline
    formation of amino acid
    e.g. natto (bacillus subtilis)
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26
Q

[9.2] Differences between homofermentative and heterofermentative

A
  • in terms of products tau lahya
  • gas produced/not
  • homo used as starter in dairy industry, hetero rarely
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26
Q

[9.2] Differences between homofermentative and heterofermentative

A
  • ## in terms of products
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27
Q

[9.3] examples of fermented foods derived from milk

A

cultured buttermilk, yoghurt, cheese, kefir, dadih, sour cream, crème fraîche, custard, lassi and koumiss

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28
Q

[9.4] examples of fermented foods derived from cereals

A

Tempe
Beer
Tape
Oncom
Bread
Soy Sauce (Kecap)

29
Q

[9.5] Commercial fermentation products in food industries

A

Yoghurt
Probiotic drink
Soy Sauce
Kombucha
Kimchi
Tempe
Vinegar
Cheese

30
Q

[9.6]

A

PRIMARY
- produced during log phase
- directly involved in normal growth, development, reproduction
- examples: ethanol, citric acid, glutamic acid, lysine, vitamins, polysaccharides

SECONDARY
- produced near onset of stationary phase
- does not cause death if not present
- examples: bacteriocin, antibiotics, toxin

31
Q

[9.7] Advantage of fermentation in food

A
  • Extend the shelf-life of product than the raw or original product
  • Increase the organoleptic properties
  • Removal of harmful ingredients from raw materials
  • The enhancement of nutritional properties due to the presence of fermenting microorganisms
  • Reduce the cooking time
  • Consist of higher in vitro antioxidant capacity, make the quality of food more better than the raw or original product
32
Q

[9.8] Why is it necessary to conduct a gradual process when scaling up fermentation?

A

Scale up studies refers to the act of using results obtained from laboratory studies for designing a prototype and a pilot plant process; construction a pilot plant and using plant data for designing and constructing a full scale plant

doing it gradually the chances of success in the fermentation process become greater and provide maximum results of the aimed products. From laboratory scale to pilot scale and industrial scale at last large amounts of money are committed to full scale production mainly to build industrial size fermenter capable or close of producing the fermentation products as efficient as those produced in small scale fermenters. Other than financially, scaling up studies is important because we could determine the various operational parameters for optimized oxygen supply to the fermentation process, selection of optimum operative modes of the fermenter, determine the changes in rheological properties and its effect on the fermentation process, modelling and formulation of process controls.

33
Q

[10.1] Microbial spoilage in meat products under aerobic conditions

A

Slime production
Colour change
Rancid smell

34
Q

[10.1] Microbes involved in slime production (context: aerobic meat spoilage)

A

Pseudomonas
Micrococcus
Stretococcus
Achromobacter
Bacillus

35
Q

[10.1] Microbes involved in colour change (context: aerobic meat spoilage)

A

*production of H2O2 oxidative agent, turning meat from red to green-brown/grey

Leuconostoc
Lactobacillus

36
Q

[10.1] Microbial spoilage in meat products under anaerobic conditions occur in what conditions

A

vacuum-packed meat; LAB population 10^7 - 10^8

37
Q

[10.1] Microbes involved in anaerobic meat spoilage

A

Predominantly LAB (Lactobacillus, Carnobacterium, Leuconostoc)

Others: E coli, Clostridium, Pseudomonas, Achromobacter, Peroteus

38
Q

[10.1] Microbial spoilage in meat stored close to 0 C

A

slime production
sour/cheesy/acid odours
discoloration

39
Q

[10.1] Microbes responsible for spoilage of meat stored close to 0 C

A

Enterobacteriaceae: Serratia liquefaciens, entero bacter agglomerans, hafnia alvei
Others: Achromocabter, leuconostoc, pseudomonas, flavobacterium, lactobacillus, streptococcus

40
Q

[10.2] Bacteria in eggs from chicken of young age and good health

A

Gram (+) bacteria (micrococcus, staphylococcus)

41
Q

[10.2] Contamination of gram postitive bacteria in eggs

A

citrobacter
campylobacter
enterobacter
escherichia
hafnia
salmonella
serratia
proteus

42
Q

[10.3] Spoilage microbes in eggs

A

Bacteria: Proteus, Aeromonas, Serratia, Enterobacter, Acinetobacter, Alcaligens, Pseudomonas, Salmonella, Campylobacter, Listeria, and Staphylococcus

Mold: Cladosporium, Alternaria, Thamnidium, Mucor, and Aspergillus

Yeast: Candida, Debaryomyces, and Hyphopichia

43
Q

[10.3] Spoilage microbes in egg products

A

Bacteria: Bacillus spp., Enterobacter Aerogenes, Escherichia coli, Staphylococcus aureus

Yeast: Candida albicans, Candida catenulata, Candida tropicalis, Candida krusei and Candida parapsilosis

Molds: Alternaria alternaria, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Mucor spp., Rhizopus spp, Penicillium spp., Cladosporium spp., Aspergillus spp., and Alternaria spp

44
Q

[10.4] Spoilage bacteria in fish from tropical regions

A

gram positive mesophilic bacteria
Bacillus, Micrococci, and coryneform bacteria.

45
Q

[10.4] Spoilage bacteria in fish from temperate regions

A

gram negative psychotropic bacteria
Pseudomonas, Moraxella, Achromobacter, Cytophaga, and Flavobacterium.

46
Q

[10.4] Mechanism of spoilage in fish due to enzymatic reactions

A

After the death, fisheries enter the rigor mortis phase. In this phase, glycogen that is used in the muscle to be converted to CO2 and water after supplying oxygen to the cells slowly decreases. This could happen due to the presence of an enzyme in the muscle that converts glycogen into lactic acid. Thus, this condition makes the muscle softened and proteins are broken down by enzymes, making autolysis occurs. In this phase, fisheries already enter post rigor phase. The autolysis process may cause an internal breakdown of the structure of the protein and fats due to a complex series of reactions by enzymes.

47
Q

[10.4] Mechanism of spoilage in fish due to autolytic activities

A

influenced by commensal flora and storage conditions, such as duration time of storage, the temperature of storage, and presence of oxygen and other gases.

48
Q

[10.10] Why can refrigerated milk still be spoiled

A

Milk stored in the refrigerator can still experience spoilage, this is because the present of cold-resistant or psychrotropic bacterial microorganisms dominate milk. Pseudomonas, Flavobacterium, Alcaligenes, Bacillus and Enterococcus are gram-positive and gram-negative bacteria that are able to withstand cold temperatures. These cold-resistant bacteria cause some damage to milk such as

E. coli which produces CO2 gas so that, milk have a bubble in the surface
The bacteria above, especially Bacillus and Pseudomonas, also produce protein decomposition due to the activity of the protease enzyme produced so that, the smell and taste of milk is sour and bitter and rotten.
Pseudomonas give spot color to milk
Pseudomonas and Acinobacteria can oxidize fat so that a rancid odor arises from milk

49
Q

[11.1] Non-sporeforming pathogenic bacteria that causes foodborne diseases

A

Found primarily in the genera Bacteroides, Fusobacterium, Peptostreptococcus, Actinomyces, Arachnia, Bifidobacterium, and Propionibacterium.

The bacteria are;
* Salmonella spp.
* Vibrio parahaemolyticus
* pathogenic E. coli
* Cronobacter spp. such us C. sakazakii, C. Malonaticus, C. turecensis and etc.
* Staphylococcus aureus
* Listeria monocytogenes

50
Q

[11.2] Sporeforming bacteria that can cause fodborne diseases

A

Clostridium botulinum, Bacillus cereus, Bacillus antracis

51
Q

[11.3] Molds that are foodborne disease hazards

A
  • Alfaltoxins
    produced by Aspergillus flavus, A. niger, Clasdosporium cladosporioides and Ochratoxins produced by Aspergillus ochraceus. This toxin causes damage to the liver and if accumulated it can cause liver cancer
  • Rubratoxin produced by Penicillium rubrum, Patulin produced by P. expansum, P.moniliforme, P. claviforme and P. urticae, Islanditoxin or yellow rice toxin derived from P. islandicum, and citrinin produced by Penicillium citrinum which can cause renal failure.
  • Toxin produced by Fusarium spp. which causes burning in the mouth, throat, stomach and spinal cord and Claviceps spp. which causes narrowing of blood vessels.
51
Q

[11.3] Molds that are foodborne disease hazards

A
  • Alfaltoxins
    produced by Aspergillus flavus, A. niger, Clasdosporium cladosporioides and Ochratoxins produced by Aspergillus ochraceus. This toxin causes damage to the liver and if accumulated it can cause liver cancer
  • Rubratoxin
    produced by Penicillium rubrum, Patulin produced by P. expansum, P.moniliforme, P. claviforme and P. urticae, Islanditoxin or yellow rice toxin derived from P. islandicum, and citrinin produced by Penicillium citrinum which can cause renal failure.
  • Patulin
    produced by Penicillium expansum and Penicillium moniliforme causing bleeding, eczema, inhibitory against bacteria
  • Fumonisin
    produced by Fusarium spp. which causes burning in the mouth, throat, stomach and spinal cord and Claviceps spp. which causes narrowing of blood vessels.
52
Q

[11.4] Why don’t viruses grow in food?

A

Viruses are intracellular obligate parasites, that is, parasites that cannot live outside their living host cells. Viruses can grow and develop by using host cells to help their reproduction so that, if the host cell does not function then, the virus will not be able to reproduce and grow. Food in the form of raw materials or the results of the process cannot be used as a place to grow by viruses, because the existing cells are dead. But, food can be a distributor of viruses present in food into the human body. New viruses can grow and develop in host cells present in the human body.

53
Q

[11.5] Factors for bacterial pathogen growth in food

A
  1. Intrinsic factors: pH level, nutrients, water activity, and redox potential
  2. Extrinsic factors: temperature, relative humidity
54
Q

[11.6] Main source of protozoa contamination

A

non-hygiene environtment. water that has been contaminated

often contains protozoa such as Giardia lamblia that can infect the digestive tract when consumed

55
Q

[11.7] What are the forms of helminthic parasites that are microscopic?

A

The egg and larva forms of helminthic parasites that are microscopic. Because of this, helminthic parasites can cause foodborne illness.

There are 3 major groups of helmintic parasites include : platyhelminths (flatworms), acanthocephalins (thorny-headed worms), and cestodes (tapeworms). Helminth is a general term for a parasitic worm

56
Q

[11.8] Difference between endotoxin and exotoxin

A

Endotoxins
- structures are tightly associated with the outer membrane of Gram-negative bacteria
- also known as lipopolysaccharides.

Exotoxins
- polypeptide proteins located on extrachromosomal genes
- toxins produced and released to the environment (foods, intestines) by bacteria or molds

57
Q

[11.9] Why are mycotoxins heat resistant

A

They are not proteins, thus are not heat labile as they do not get denatured at temperatures at which proteins do

58
Q

[11.10] Name a biotoxin and its effect on health?

A
  • SAXITOXIN by dinoflagellates
    Paralytic shellfish poisoning (PSP): causes nausea, diarrhea, shortness of breath
  • DOMOIC TOXIN by diatoms Psedonitzchia
    Amnesic shellfish poisoning (ASP): nausea, vomiting, coma, death
  • OKADAIC ACID by dinophysis
    Diarrhetic shellfish poisoning (DSP): nausea, vomiting, diarrhea, fever
  • HISTAMINE by Morganella morganii
    Scromboid toxin: headache, sweating, burning mouth and throat
  • SODIUM CHANNEL BLOCKER by symbiotic bacteria pseudomonas
    Tetrodotoxin: causes an increasing paralysis of the muscles of the body
59
Q

[12.1] Difference between infection and intoxication

A

Infection
- Ingestion of live bacteria
- Slow onset time

Intoxication
- consume food containing toxins produced by the microbe
- toxin can exust althoughr microbe is dead
- rapid onset time

60
Q

[12.2] How does the mechanism of infection due to virus differ from bacteria?

A

The virus, after getting to know the receptor it wants to host, the virus will infect the target by injecting viral DNA or RNA into the target cell so that the viral DNA or RNA will force the host cell to replicate to produce quite a lot of synthetics. It then damages the cells by making them lysis and the virus cells will release looking for new receptors to infect.

Meanwhile, bacteria infect target cells by forming a collection of bacteria or tethering bacterial messengers to target cell proteins so as to disrupt metabolic processes in a cell. In addition, bacteria can also use their ability to invade body organs by penetrating into deeper tissues. Some bacteria make toxins outside the human body and then, the existing toxins attack the body if consumed.

61
Q

[12.3] Why are sporeforming bacteria present in heat treated food

A

the spore phase produced by the bacteria helps bacteria survive extreme environments, one of which is high temperatures

Endospores are formed through asymmetrical cell division followed by thickening of the cell wall and accumulation of unique endospore compounds. The thick endospore wall and dipicolinic acid compounds and small acid-soluble spore proteins produced are able to function as bacterial protection from extreme conditions so that damage does not occur

62
Q

[12.4] Sequellae in foodborne diseases

A

ARTHRITIS
Salmonella, yersinia

GUILLAIN BARRE SYNDROME
Campylobacter jejuni

HOMOLYTIC UREMIC SYNDROME
Enterohemorrhagic E. coli

THROMBOTIC THROMBOCYTOPENIC PURPURA
Enterohemorrhagic E. coli

63
Q

[12.5] What food is associated with Cronobacter spp infection

A

Dehydrated infant formula is the food most associated with infections by Cronobacter spp.

64
Q

[12.6] Defind foodborne disease outbreak

A

Incident in which two or more poeple experience a similar illness resulting from ingestion of a common food. Data collected from investigations and surveillance

65
Q

[12.7] Example of a foodborne disease outbreak

A
  • Enoki mushrooms in 2022 containing Listeria monocytogenes causing fever, headache, nausea, diarrhea, neck stiffness, and meningitis
  • Hepatitis A outbreaks in 2016 due to contaminated frozen strawberries causing 143 illness in 9 states
  • Salmonella outbreaks in 2016 from raw sprouts infected 32 people in 13 states
66
Q

[12.9] Nonspecific host defenses against a pathogen

A

The nonspecific innate immune response provides a first line of defense that can often prevent infections from gaining a solid foothold in the body. These defenses are described as nonspecific because they do not target any specific pathogen. Rather, they defend against a wide range of potential pathogens. n human body, for example, has skin protection to prevent pathogen from getting inside our body, mucous membrane to trap pathogen to be thrown out later with sneeze or cough, phagocytosis that ‘eats’ infected cells, fever which helps to raise body temperature and make it harder for bacteria or virus to survive in, inflammation which was your white blood cells attacking pathogen in your body, etc.

67
Q

[12.10] What are virulence factors of a pathogen?

A

Virulence factors help pathogenic bacteria to invade the host, cause disease, and evade host defenses. The following are types of virulence factors:

  1. Adherence Factors: Many pathogenic bacteria colonize mucosal sites by using pili (fimbriae) to adhere to cells.
  2. Invasion Factors: Surface components that allow the bacterium to invade host cells can be encoded on plasmids, but more often are on the chromosome.
  3. Capsules: Many bacteria are surrounded by capsules that protect them from opsonization and phagocytosis.
  4. Endotoxins: The lipopolysaccharide endotoxins on Gram-negative bacteria cause fever, changes in blood pressure, inflammation, lethal shock, and many other toxic events.
  5. Exotoxins: Exotoxins include several types of protein toxins and enzymes produced and/or secreted from pathogenic bacteria. Major categories include cytotoxins, neurotoxins, and enterotoxins. Maybe produced in the small intestines or colon
68
Q

[13] Factors affecting heat resistance of organism

A

WATER : decrease (peptide bond hyd)
FATS : increase
CARBOHYDRATES : increase
PROTEINS : protective effect
SALTS : increase

69
Q

[13.1] DIfference between pasteurization and commercial sterilization

A
69
Q

[13.1] DIfference between pasteurization and commercial sterilization

A

Pasteurization is a heating process to inactivate vegetative pathogenic bacteria. Two types: LTLT (63C 30min) and HTST (72C 15s)

Commercial sterilization inactivates vegetative and spore forming bacteria (121 moist heat 15min)

70
Q

[13.2] F0 value

A

Measurement of thermal adequacy equivalent to heating time at constant temp 250F

F0 = Dr (log Ninitial - log Nfinal)

Food Microbiology (5 decks)

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