TOPIC 7 Product Evaluation & Storage Stability

Question 1

what are the types of product evaluation parameters ? (6)

Answer 1

● appearance, colour, odour, flavour, etc.
● physical-chemical eg. pH value, viscosity, density, etc.
● microbiological parameter eg. microbial count and challenge test of preserving system
● performance test
● sensory evaluation
● container parameters eg. interaction, migration of components between package, container deformity, etc.

Question 2

what microbes are tested for in microbial preservation testing ? (5)

Answer 2

bacteria
● Staphylococcus aureus
● Escherichia coli
● Pseudomonas aeruginosa

yeast
● Candida albicans

mould
● Aspergillus niger

Question 3

how are bacteria plate counts carried out according to USP <61> Total Microbial Count (3)

Answer 3

1. sample of product taken and placed in suitable neutraliser broth
2. dilutions plated to appropriate bacterial growth agar plates
3. plates incubated and then analysed to determine presence of aerobic bacteria (if contaminated, further evaluation / reformulation may be necessary)

Question 4

how is the preservative challenge test carried out using USP <51> test method ? (2)

Answer 4

1. product separated out into 5 containers each being challenged with one of the 5 method-specified microbes at fairly high concentrations
2. remaining concentration of each microbe counted at specified intervals for no less than 28 days

Question 5

how does a preservative system pass the preservative challenge test (2)

Answer 5

● no increase in microbes
● sufficient decrease by day 14

Question 6

what exempts a product from undergoing preservative challenge test ? (5)

Answer 6

● anhydrous (no water)
● pH < 3 or > 10
● contains > 20% alcohol
● filled in containers at > 65 deg C
● packaged in pressurised container, pump dispenser, or single-dose units

Question 7

sunscreen efficacy testing (in-vivo on human subjects)

Answer 7

● 3 days
● participants treated with product on small section of skin exposed to UV light and evaluated for erythema after specific periods

Question 8

regression method by Kligman (skin moisturising) (3)

Answer 8

1. product applied on subject’s body twice daily
2. test sites are evaluated on day 7 and 14 and dry skin scores given
3. treatment stopped after day 14 but evaluation continues for 2 more weeks to determine duration for regression to original condition

Question 9

methods to determine skin condition for Kligman’s regression method (3)

Answer 9

● corneometer
● spectroscopy imaging
● adhesive tape stripping

Question 10

levels of testing for product functionality test (3)

Answer 10

● lab testing
● salon testing
● consumer testing

Question 11

advantages of lab testing (2)

Answer 11

● most control over experimental variables
● provides most technical precise data

Question 12

limitation of lab testing (1)

Answer 12

does not provide info on consumers’ perception

Question 13

characteristics of salon testing (3)

Answer 13

● evaluation during actual usage on consumers while maintaining measure of control
● trained technicians generate data on product characteristics
● test product usually evaluated in comparison to designated control product

Question 14

how is consumer testing carried out ?

Answer 14

product is provided for consumer to test at home for certain period of time according to their usual habit / practice

Question 15

advantage of consumer testing (1)

Answer 15

provides accurate info on consumer perception of product

Question 16

limitation of consumer testing (1)

Answer 16

poor control over variables eg. frequency of usage, amount used

Question 17

what to test for in cleanser (6)

Answer 17

● pH
● viscosity
● cleansing ability
● lathering
● rinseability
● microbial testing

Question 18

what to test for in moisturiser (5)

Answer 18

● pH
● viscosity
● moisturising ability
● sensory test
● microbial testing

Question 19

what to test for in powder cosmetics (5)

Answer 19

● vibration test
● drop test
● covering power
● applied colour
● lasting quality

Question 20

what to test for in lipsticks (8)

Answer 20

● adhesion
● luster
● drying speed
● lasting quality
● colouring ability
● water resistance
● hardness
● load test

Question 21

stability testing

Answer 21

evaluating a product to ensure the key attributes stay within acceptable guidelines (maintain good quality throughout shelf life)

Question 22

3 steps of stability testing

Answer 22

1. accurately establish nature of critical product attributes
2. measure how they change over time
3. define the degree of change that is considered acceptable

Question 23

factors (3) affecting stability of product

Answer 23

● chemical reactions eg. hydrolysis, esterification, oxidation
● microbial contamination
● temperature

Question 24

how do chemical reactions (3 types) affect stability of product

Answer 24

● hydrolysis of ester decreases pH
● esterification may produce unwanted fruity smell
● oxidation may cause rancid odour or change in colour, affects efficiency of oxygen-sensitive ingredients (eg. vit A)

Question 25

how does microbial contamination affect stability of product

Answer 25

causes bad odour

Question 26

how does temperature affect stability of product

how does it affect stability ? (1)
4 aspects it affects (4)

Answer 26

stability decreases with changes to temperature
● affects solubility of surfactant
● affects Brownian motion
● affects fluid viscosity
● affects phases of interfacial film

Question 27

how to calculate accelerated testing for stability

Answer 27

each 10°C increase in temp doubles the reaction rate (halves the time taken)

Question 28

room temperature stability testing conditions (3) and how long

Answer 28

● in darkness
● exposed to artificial light
● under exaggerated humidity

for duration of product’s shelf life or up to 3 years

Question 29

stability test for 30-40°C conditions (2) and duration

Answer 29

● in darkness
● exaggerated humidity

for max. 6 mths

Question 30

stability test for 50°C duration

Answer 30

max. 6 mths

Question 31

stability test for > 50°C duration

Answer 31

max. 3 mths

Question 32

stability test for 0-5°C duration

Answer 32

duration of product’s shelf life or up to 3 years

Question 33

stability test outdoor condition and duration

Answer 33

under sunlight for duration of product shelf life

Question 34

freeze/thaw testing procedure (6)

Answer 34

1. prepare samples and take initial readings
2. freeze at -18°C for 24 hours
3. thaw at room temperature
4. place in 50°C oven for 24 hours
5. thaw at room temperature
6. complete 3-6 cycles - successful completion indicates good product stability

Question 35

potential drawback of accelerated stability testing

Answer 35

at high temperatures, one may be forcing reactions that would not happen at all at lower temperature to occur

Question 36

centrifugation stability testing

Answer 36

centrifuge emulsion at high speed eg. 10 000 rpm for 20 mins and check for separation

Question 37

stability test is needed for which situations (5)

Answer 37

● product development: obtaining preliminary stability information
● scaling up
● changes in manufacturing procedure
● change in raw materials (even if only change supplier)
● packaging considerations

Question 38

carry out stability study on

Answer 38

pilot batches and production batches

Question 39

how much deviation is acceptable for stability study

Answer 39

usually +/- 10% of original value of pH / viscosity

Question 40

approach during product failure

Answer 40

1. identify problem
2. propose possible causes
3. carry out testing
4. analyse result
5. propose possible solution