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Food science > Introduction > Flashcards

Introduction Flashcards

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1
Q

What is CFU?

A

Colony forming unit

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2
Q

What is the most commonly used method for counting CFU/ml?

A

Turbidity measurment

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3
Q

What are the units for turbidity measurement?

A

Optical density

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4
Q

What does turbidity use to measure CFU/ml?

A

Scattered light

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5
Q

How do you calculate absorbance?

A

Log (incident light/transmitted light)

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6
Q

Negatives of turbidity

A

No difference between live or dead cells
Not reliable at low numbers

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7
Q

What is viable counting?

A

Using a dilution series to count cells

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8
Q

What does auxotrophic mean?

A

Microbes that can’t make a compound

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9
Q

What is D-value?

A

Time required to kill 90% of starting population for a concentration of biocide

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10
Q

How are biocides activated?

A

Contact with bacterial cell surface

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11
Q

What are the 6 classes of biocides?

A

Phenols
Alcohols
Halogens
Quaternary compounds
Metals
Oxidising agents

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12
Q

Examples of phenols

A

Carbolic acid and Lysol

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13
Q

Why aren’t phenols used in the food industry?

A

They leave a ‘taint’

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14
Q

Why are alcohols used in food production environments?

A

Detergent action
Lipid solvent
Protein denaturation

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15
Q

Ingredients in alcohol biocides

A

Methanol, ethanol and isopropanol

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16
Q

Why aren’t halogens used on metals?

A

Corrosion

17
Q

Examples of halogens

A

Iodine
Tyrosine
Chlorine
Hypochlorous acid

18
Q

Function of halogens

A

Oxidises cellular components

19
Q

Function of quaternary compounds

A

Penetrate aqueous environments and targets lipids and proteins

20
Q

Negatives of quaternary compounds

A

Very expensive

21
Q

Function of metals as biocides

A

Combine with SH group of cysteine and used as algicide and fungicide

22
Q

What is the main oxidising agent used?

A

Hydrogen peroxide

23
Q

Function of oxidising agents

A

Sporicidal

24
Q

Positives of oxidising agents

A

Residue free
Preservative in food treatment
Disrupts proteins

25
Q

What needs to be considered when picking a biocide?

A

Surface
Amount of organic matter
Toxic residue possibility
Capsules

Food science (3 decks)

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