Food technology

Question 1

Describe the main intrinsic factors affecting microbial behaviour in foods;

Answer 1

Nutrients” contentin a food product.
Any natural antimicrobial substances that might be present.
The pH change and its ability to resist pH change (buffering capacity).
The oxidation reduction potential (Eh) of the food and its ability to resist redox change (poising capacity).
The water activity of the foodW

Question 1

describe the main extrinsic factors affecting microbial behaviour in foods;

Answer 1

Temperature.
Gaseous atmosphere surrounding the food.
Relative humidity of the atmosphere surrounding the food.
Time

Question 2

What is D value

Answer 2

D value (decimal reduction time) is the time taken for the population to pass through a log cycle (90% of the population is killed) at a certain temperature.

D121 – the time requires to kill 90% of a population of microorganisms at 121ºC.

Listeria monocytogenes D71.7 = 3.3 sec

Question 3

What is Z value

Answer 3

Temperature required to reduce the time needed to kill 90% of a population of microorganisms by a factor of 10. In other words, it represents the temperature increase needed to decrease the microbial death time (D value) by a factor of 10.

Question 4

Foods that undergo surface spoilage from moulds, yeasts, and certain bacteria should be stored under conditions of _____ RH

Answer 4

Low

Question 5

What gas is the single most important atmospheric gas that is used to control microorganisms in foods

Answer 5

CO2

Question 6

Why is smoking a way to preserve food

Answer 6

Wood smoke contains a number of substances that have antimicrobial activity.
Formaldehyde and higher aldehydes, phenols and methanol.
Highly inhibitory to miroorganisms.

Question 7

What is microbiological criteria

Answer 7

1. A statement of the microorganisms and/or their toxins of concern to the food.
2. The methods to be used for their detection and/or enumeration.
3. A sampling plan.
4. The microbiological limits to be used in assessing the results
5. Guidance for interpreting the results.

Question 8

What is a sampling plan

Answer 8

A sampling plan is a method used to evaluate a batch (lot) of items to decide if it meets certain standards or criteria. It involves selecting and testing a specific number of items (samples) from the batch based on a set of rules to determine whether the batch passes or fails.

Question 9

What is two class sampling

Answer 9

There are only two possible outcomes for a batch:

Pass (the batch meets the required standards)
Fail (the batch does not meet the required standards)

The specifications of a two-class plan are:
n = Number of sample units you need to test.
c = Maximum number of defective items allowed in the sample for the lot to be accepted.
m = Maximum number of defective items allowed in the entire batch (lot) for it to be accepted.

Question 10

What is three class sampling

Answer 10

This plan is a bit more complex and allows for more detailed classifications:

Acceptable (good items)
Marginally acceptable (can be accepted but require attention)
Unacceptable (fail the batch)

The specifications of a three-class plan are:
n = Number of sample units you need to test.
c = Maximum number of defective items allowed for the lot to be marginally acceptable.
m = Maximum number of defective items allowed for the lot to be acceptable.
M = Maximum number of defective items allowed before the batch is unacceptable.