Shelf life of Foods
CL5901~ FOOD PACKAGING
Official (Closed) and Non-Sensitive
Outline
 Methods to Determine Shelf Life
 Factors Affecting Product Shelf Life
 Packaging Properties & Product Shelf Life
Water Vapour Transfer & Shelf Life
 Accelerated Shelf Life Testing (ASLT)
ASLT Procedures
Problems associated with ASLT
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Official (Closed) and Non-Sensitive
Introduction
 Singapore Food Regulation defines “expiry date”
in relation to a prepacked food (specified in The
Second Schedule) as “ the date after which the
food, when kept in accordance with any storage
conditions set out on the label of that food, may
not retain its normal wholesomeness, nature,
substance and quality”
 EU legislation in COMMISSION REGULATION (EC)
No 2073/2005 defines shelf life as “ either the
period corresponding to the period preceding
the ‘use by’ or the minimum durability date, as
defined respectively in Articles 9 and 10 of
Directive 2000/13/EC”
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Official (Closed) and Non-Sensitive
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Official (Closed) and Non-Sensitive
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Official (Closed) and Non-Sensitive
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Official (Closed) and Non-Sensitive
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Official (Closed) and Non-Sensitive
In Singapore, date marking is mandatory for 19 categories of foods.
These include perishable products, infant foods, product whose
quality deteriorate over time (e.g. oil/ juice drink), products that are
susceptible to contamination after prolong storage ( e.g. flour/
cereals)
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Official (Closed) and Non-Sensitive
Source: SFA, 2020
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Official (Closed) and Non-Sensitive
Source: SSO, 2021
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By Singapore Food Agency
Published 2 1 May 2019 |
Updated 2 7 Feb 2 0 2 0
'Use by' dates are for highly perishable food
such as milk and yoghurt. You are advised to
not consume them if they have passed their
'use by' dates.
'Best before' dates are for food with a longer
shelf life such as cereals. They indicate how
long the food will be at its best quality. ‘Sell
by’ dates inform retailers when to take the
item off the shelves.
Source: SFA, 2020
However, the safety of a food product is not
dependent on its expiry date alone. Products
not stored or handled properly can be unsafe
for consumption too. So remember to check
for signs of spoilage before consuming them!
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Source: FAO, 2018
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Official (Closed) and Non-Sensitive
Common date
marking

Use By / Expiry Date:
 Foods must be discard by the date. Unsafe to consume after the
date
 Usually storage condition is stated
 Illegal to sell foods after “Use-by” or “Expiry date”
 Usually for foods that are highly perishable from microbiological
point
 Best Before Date/ Best if Use By :
 Foods may still be acceptable (safe to eat) as long as they are not
damaged/deteriorated but their quality may have deteriorated
 Usually for canned, dried, ambient and frozen foods e.g. cereal,
biscuits
 However, in Singapore for the purpose of Food Regulations, “BEST
BEFORE” has the same meaning as “Use By”
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Official (Closed) and Non-Sensitive
Common date marking

Use By / Expiry Date:
 Foods must be discard by the date. Unsafe to consume after the
date
 Usually storage condition is stated
 Illegal to sell foods after “Use-by” or “Expiry date”
 Usually for foods that are highly perishable from microbiological
point

Best Before Date/ Best if Use By :
 Foods may still be acceptable (safe to eat) as long as they are not
damaged/deteriorated but their quality may have deteriorated
 Usually for canned, dried, ambient and frozen foods e.g. cereal,
biscuits
 However, in Singapore for the purpose of Food Regulations, “BEST
BEFORE” has the same meaning as “Use By”
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Official (Closed) and Non-Sensitive
Shelf Life Determination
Companies conduct shelf life determination:
 To determine shelf life of existing products
 To study effect of changes in processing parameters,
ingredients, storage conditions and packaging materials
on product shelf life
 To determine shelf life of new products
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Official (Closed) and Non-Sensitive
Methods to Determine Product Shelf Life
 Literature Study:
 Published literature e.g. books on shelf life of foods
 Limited data and applicable to commodity-type of foods
 Turnover Time:
 Monitor the sales and determine the average duration that products stay
on the retail shelf
 Estimate only the “required” shelf life at retail outlets rather than “true”
shelf life.
 End point study
 Determine product quality through lab testing on samples purchased from
retail outlet
 Good estimation since products went through the actual supply chain
 Accelerated Shelf Life Testing (ASLT)
 Accelerate the deterioration rate by modifying the known environmental
conditions
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Official (Closed) and Non-Sensitive
Factors Affecting Product Shelf Life
Product shelf life are affected by:

Product formulation or processing parameters (intrinsic
factors)
 pH, Aw, m/o or enzymes which may be controlled by
ingredients or processing parameters

Environment where products are exposed (extrinsic
factors)
 RH, light, gas environment, temperature
stress during storage or distribution

or mechanical
Properties of packaging
 OTR,WVTR of plastic based packaging, hermetically sealed,
product/package interactions, package dimensions
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Official (Closed) and Non-Sensitive
Packaging Properties & Product
Shelf Life
 Metal and glass containers are essentially impermeable to gases,
odour and water vapour while plastic have varying degree of
permeability
 Excessive moisture gain/ oxygen uptake affect product shelf life
 Prediction of the rate of gas or vapour transfer across the film can
be expressed as following:
𝛿𝑊
𝛿𝑡
=
𝑃
𝑋
𝐴 (𝑝1 − 𝑝2 )  (1)
P/X = Permeance
A = Surface area of packaging
𝑝1 − 𝑝2 = Partial pressure of water vapour outside and inside the packaging
𝛿𝑊
𝛿𝑡
= rate of gas/vapour transport across the film
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Official (Closed) and Non-Sensitive
Water Vapour Transfer & Shelf Life
 The simplest analysis using Eq (1) is to assume P/X (permeance)
and external environment (e.g. temp & RH) to be constant
 P/X is unlikely to be constant due to fluctuation of temp and RH
during storage/transportation. However, using of WVTR at 38℃,
90% RH can give a “worst-case” scenario analysis
 Internal vapour pressure of water in foods (𝑝2 ) varies with
𝛿𝑤
moisture content of foods so
(rate of gain/loss of moisture)
𝛿𝑡
falls as ∆ρ is smaller. Thus, 𝑝2 as function of moisture must be
incorporated into the equation to make proper predictions
Recall Week 2 slide 20 : P = TR
𝑋
𝑝1 − 𝑝2
so
𝑃
𝑋
=
(
𝑇𝑅
𝜌1 − 𝜌2 )
or TR =
𝑃
𝑋
( 𝜌1 − 𝜌2 )
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Official (Closed) and Non-Sensitive
Recall: Moisture Sorption Isotherm
 Moisture content in food will
reach equilibrium with the
surrounding when they are
placed in an environment
with constant temp & RH.
This moisture is known as
equilibrium moisture content
 Moisture Sorption Isotherm
(MSI) is obtained by plotting
equilibrium moisture content
against RH or Aw at constant
temperature
Fig 1: Typical MSI showing effects of temp
Source: Robertson, 2013
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Official (Closed) and Non-Sensitive
Water Vapour Transfer & Shelf Life
 In simplest case, isotherm can be expressed as:
m = bAw + c  (2)
m = moisture content in g 𝐻2 𝑂 𝑔−1 solids
Aw = water activity
b = slope of isotherm
c = constant
 Moisture content (m), can be expressed as following:
m=
𝑊 (𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑡𝑟𝑎𝑛𝑠𝑝𝑜𝑟𝑡𝑒𝑑)
𝑊𝑠 (𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑑𝑟𝑦 𝑠𝑜𝑙𝑖𝑑𝑠 𝑒𝑛𝑐𝑙𝑜𝑠𝑒𝑑)
 (3)
So, W = m 𝑊𝑠  (4)
And, δ𝑊 = 𝛿𝑚 𝑊𝑠  (5)
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Official (Closed) and Non-Sensitive
Water Vapour Transfer & Shelf Life
Since δ𝑊 = 𝛿𝑚 𝑊𝑠
By substituting into Eq (1),
𝛿𝑚𝑊𝑠
𝛿𝑡
𝛿𝑚𝑊𝑠
𝛿𝑡
=
=
𝑑𝑚
𝑚𝑒 −𝑚
𝑃
𝑋
=
𝑃
𝑋
𝐴
𝐴(
𝑝𝑜
𝑏
𝑝𝑜 𝑚𝑒
𝑏
−
𝑝𝑜 𝑚
)
𝑏
 (6)
( 𝑚𝑒 − 𝑚)  (7)
𝑃 𝐴 𝑝𝑜
𝑋 𝑊𝑠 𝑏
𝛿𝑡  (8)
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Official (Closed) and Non-Sensitive
Water Vapour Transfer & Shelf Life
On integration,
ln
𝑚𝑒 − 𝑚𝑖
𝑚𝑒 −𝑚
=
𝑃 𝐴 𝑝𝑜
𝑋 𝑊𝑠 𝑏
𝑡  (9)
𝑚𝑒 = 𝐸𝑞𝑢𝑖𝑙𝑏𝑖𝑟𝑢𝑚 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑓𝑜𝑜𝑑 𝑒𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑒𝑥𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑎𝑐𝑘𝑎𝑔𝑒 𝑅𝐻
𝑚𝑖 = 𝐼𝑛𝑖𝑡𝑎𝑙 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑜𝑜𝑑
𝑚 = 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑜𝑜𝑑𝑠 𝑎𝑡 𝑡𝑖𝑚𝑒 𝑡
𝑝𝑜 = 𝑣𝑎𝑝𝑜𝑢𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑓 𝑝𝑢𝑟𝑒 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 𝑡ℎ𝑒 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 (𝑛𝑜𝑡 𝑡ℎ𝑒 𝑎𝑐𝑡𝑢𝑎𝑙
𝑣𝑎𝑝𝑜𝑢𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑢𝑡𝑠𝑖𝑑𝑒 𝑡ℎ𝑒 𝑝𝑎𝑐𝑘𝑎𝑔𝑒)
If end of product shelf life is when m = 𝑚𝑐 (critical moisture
content) and time = 𝜃𝑠 (shelf life), Eq (9) can be written as
ln
𝑚 𝑒 − 𝑚𝑖
𝑚𝑒 −𝑚𝑐
=
𝑃 𝐴 𝑝𝑜
𝑋 𝑊𝑠 𝑏
𝜃𝑠  (10)
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Official (Closed) and Non-Sensitive
Water Vapour Transfer & Shelf Life
Eq (10) is used for moisture gain in products while the following can be
used for moisture loss:
ln
𝑚 𝑖 − 𝑚𝑒
𝑚−𝑚𝑒
=
𝑃 𝐴 𝑝𝑜
𝑋 𝑊𝑠 𝑏
𝜃𝑠  (11)
𝑚𝑒 = 𝐸𝑞𝑢𝑖𝑙𝑏𝑖𝑟𝑢𝑚 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑓𝑜𝑜𝑑 𝑒𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑒𝑥𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑎𝑐𝑘𝑎𝑔𝑒 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 ℎ𝑢𝑚𝑖𝑑𝑡𝑦
𝑚𝑖 = 𝐼𝑛𝑖𝑡𝑎𝑙 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑜𝑜𝑑
𝑚 = 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑜𝑜𝑑𝑠 𝑎𝑡 𝑡𝑖𝑚𝑒 𝑡
𝑝𝑜 = 𝑣𝑎𝑝𝑜𝑢𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑓 𝑝𝑢𝑟𝑒 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 𝑡ℎ𝑒 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 (𝑛𝑜𝑡 𝑡ℎ𝑒 𝑎𝑐𝑡𝑢𝑎𝑙
𝑣𝑎𝑝𝑜𝑢𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑢𝑡𝑠𝑖𝑑𝑒 𝑡ℎ𝑒 𝑝𝑎𝑐𝑘𝑎𝑔𝑒)
𝑊𝑠 = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑑𝑟𝑦 𝑠𝑜𝑙𝑖𝑑𝑠
𝜃𝑠 = 𝑆ℎ𝑒𝑙𝑓 𝑙𝑖𝑓𝑒
Eq 10 & 11 are used to predict weight gain/loss and to predict shelf life
for changes in packaging permeability, temp or RH, surface area :
volume ratio of package or changes in initial moisture content of food
24
Official (Closed) and Non-Sensitive
Relationship of 𝑚𝑖 , 𝑚𝑐 𝑎𝑛𝑑 𝑚𝑒 in biscuit
Moisture Content
Biscuit loss its crispiness to desirable
level i.e. no longer acceptable
𝑚𝑒
𝑚𝑐
𝑚𝑖
Water Activity
𝑚𝑒 = 𝐸𝑞𝑢𝑖𝑙𝑏𝑖𝑟𝑢𝑚 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑓𝑜𝑜𝑑 𝑒𝑥𝑝𝑜𝑠𝑒𝑑 𝑡𝑜 𝑒𝑥𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑎𝑐𝑘𝑎𝑔𝑒 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 ℎ𝑢𝑚𝑖𝑑𝑡𝑦
𝑚𝑖 = 𝐼𝑛𝑖𝑡𝑎𝑙 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑜𝑜𝑑
𝑚𝑐 = 𝐶𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑜𝑜𝑑 𝑤ℎ𝑒𝑛 𝑒𝑛𝑑 𝑜𝑓 𝑠ℎ𝑒𝑙𝑓 𝑙𝑖𝑓𝑒 𝑖𝑠 𝑟𝑒𝑎𝑐ℎ𝑒𝑑
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Official (Closed) and Non-Sensitive
Example 1
ABC cornflake has an initial moisture content (𝑚𝑖 ) of 2.5%.It is found that
when moisture content is 8%, the cornflake will loss its crispiness and
become unacceptable. The moisture sorption isotherm (MSI) at 25℃
indicates that the equilibrium moisture content (𝑚𝑒 ) is 14.8%. Extension of
the linear portion of the MSI shows that the pseudo-equilibrium moisture
content of 𝑚𝑒′ is 11% and slope of the isotherm (b) is 0.147g 𝐻2 𝑂/g
solids/unit 𝑎𝑤 .
The cornflake with dry weight of 400 g is to be packed in 50 𝜇𝑚 of LDPE
with dimension of 20 cm x 30cm. Determine the product shelf life if it is to
be stored at 25℃ and 75% RH.
Given:
Vapour Pressure of pure water at 25℃ (𝑝𝑜 )= 2.3756 cm Hg
WVTR of 50𝜇𝑚 LDPE at 25℃/75% RH = 8.0 g m-2 day-1
Vapour partial pressure difference across film (𝑝1 − 𝑝2 ) = 1.782 cm Hg
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Official (Closed) and Non-Sensitive
Example 1 ~ Answer
𝑚𝑖 = 2.5%
𝑚𝑐 = 8%
𝑚𝑒′ =11%
𝑊𝑠 = 400g
b is 0.147g 𝐻2 𝑂/g solids/unit 𝑎𝑤
𝑝𝑜 at 25℃ = 2.3756 cm Hg
WVTR of 50𝜇𝑚 LDPE at 25℃/75% RH = 8.0 g 𝐻2 𝑂 m-2 day-1
Vapour partial pressure difference across film (𝑝1 − 𝑝2 ) = 1.782 cm
Hg
Surface area = 20cm x 30cm = 0.2 m x 0.3 m = 0.06 m2
27
Official (Closed) and Non-Sensitive
Example 1 ~ Answer
𝑃
𝑋
=
ln
8 𝑔 𝐻2 𝑂 𝑚−2 𝑑𝑎𝑦 −1
1,782 𝑐𝑚𝐻𝑔
11−2.5
11 −8
= 4.49 g 𝐻2 𝑂 𝑚−2 𝑑𝑎𝑦 −1 (𝑐𝑚𝐻𝑔)-1
= 4.49 g 𝐻2 𝑂 𝑚
−2
𝑑𝑎𝑦
−1
−1
(𝑐𝑚 𝐻𝑔)
×
0.06 𝑚2
400 𝑔
×
2.3756 𝑐𝑚 𝐻𝑔
0.147𝑔 𝐻2 𝑂 (𝑔 𝑠𝑜𝑙𝑖𝑑𝑠)−1
ln 2.83 = 0.011 day-1 𝜃𝑠
𝜃𝑠 = _______ days
28
𝜃𝑠
Official (Closed) and Non-Sensitive
Example 2
A cookie with an initial moisture content (𝑚𝑖 ) of 1%.It is found that it will
loss its crispiness when moisture content is 3.5%. The pseudo-equilibrium
moisture content of 𝑚𝑒′ at 40℃ is 5% and slope of the isotherm (b) is
0.055 g 𝐻2 𝑂 (g solids)-1 (𝑢𝑛𝑖𝑡 𝑎𝑤 )-1. Determine the product shelf life if it is
to be stored and distributed at 38℃ and 90% RH using an OPP package.
Given:
Weight of dry solids per packet (𝑊𝑠 ) = 500 g
Surface area of OPP package (A) = 0.045 m2
Vapour Pressure of pure water at 38℃ (𝑝𝑜 )= 4.969 cm Hg
WVTR of 25𝜇𝑚 OPP at 38℃/90% RH = 5.0 g 𝐻2 𝑂 m-2 day-1
Vapour partial pressure difference across film (𝑝1 − 𝑝2 ) =4.472 cm Hg
29
Official (Closed) and Non-Sensitive
Example 2 ~ Answer
𝑚𝑖 = 1%
𝑚𝑐 = 3.5%
𝑚𝑒′ =5%
𝑊𝑠 = 500g
A = 0.045 m2
𝑝𝑜 at 38℃ = 4.969 cm Hg
WVTR of 25𝜇𝑚 OPP at 38℃/90% RH = 5.0 g 𝐻2 𝑂 m-2 day-1
Vapour partial pressure difference across film (𝑝1 − 𝑝2 ) = 4.472 cm Hg
b = 0.055 g 𝐻2 𝑂 (g solids)-1 (unit 𝑎𝑤 )-1
𝑃
𝑋
=
5 𝑔 𝐻2 𝑂 𝑚−2 𝑑𝑎𝑦 −1
4.472 𝑐𝑚𝐻𝑔
=1.12 g 𝐻2 𝑂 𝑚−2 𝑑𝑎𝑦 −1 (𝑐𝑚𝐻𝑔)-1
30
Official (Closed) and Non-Sensitive
Example 2 ~ Answer
ln
5−1
5 −3.5
= 1.12 g 𝐻2 𝑂 𝑚
−2
𝑑𝑎𝑦
−1
(𝑐𝑚 𝐻𝑔)
−1
×
0.045 𝑚2
500 𝑔
×
4.969 𝑐𝑚 𝐻𝑔
0.055𝑔 𝐻2 𝑂 (𝑔 𝑠𝑜𝑙𝑖𝑑𝑠)−1
𝜃𝑠
ln 2.67 = 9.1 x 10-3 day-1 𝜃𝑠
𝜃𝑠 = _______ days
31
Official (Closed) and Non-Sensitive
Accelerated Shelf Life Testing (ASLT)
 Accelerated shelf life testing (ASLT) is commonly used to
shorten the process in determining product shelf life
 It deliberately increases the rate of deterioration making the
assumption that chemical kinetics can be applied to quantify
the detrimental effects of extrinsic factors (e.g. temp, RH, gas
and light)
 E.g. If storage temperature raised from 20 to 40℃, the shelf life
test that originally take 1 year will be completed within 1-2
months
 Used to speed up the evaluation process on the effects of
change in formulation/processing/packaging on product shelf
life esp. shelf stable products
32
Official (Closed) and Non-Sensitive
Accelerated Shelf Life Testing (ASLT)
 Due to problems associated with ASLT, the estimation of
actual shelf life may sometimes be limited to simple
reactions
 Hence, ASLT results are confirmed with shelf life testing
under actual environmental conditions
 As ASLT is using temperature as the accelerating factor, it
is more applicable to foods for temperate climates. In
tropical, warehousing and transportation might result in
temperature greater than 40℃
33
Official (Closed) and Non-Sensitive
Basic Principles
 Generally, foods deterioration mechanism follows either a zero
(n=0) or first order (n=1) kinetics and in any given extent of
deterioration the rate of constant is inversely proportional to
time
 𝑄10 approach can be used to estimate the effect of
temperature on the product shelf life. Temperature quotient
(𝑄10 ) is the ratio of the reaction rates between 2 temperature
that is 10℃ apart
𝑄10 =
𝜃𝑆𝑇
𝜃𝑆𝑇 = shelf life at T℃
𝜃𝑆𝑇+10 = Shelf life at (T + 10)℃
𝜃𝑆𝑇+10
 Advantage is the ability to extrapolate the results to normal storage
conditions using the results from accelerated experimental shelf life trials
34
Official (Closed) and Non-Sensitive
ASLT Procedures
Below is the recommend procedure in designing the shelf
life test:
 Identify the microbiological safety and quality parameter
 Determine Indices of failure (IoFs) and tests (e.g.
microbial, sensory) to be conducted during trial. IoFs are
quality attributes that indicates that the food is NOT
acceptable by consumers. E.g. rancid flavour due to
oxidation, loss of crispiness due to moisture ingress
 Select the package. Typically several packaging materials
are tested in order to choose the most cost effective
material
35
Official (Closed) and Non-Sensitive
ASLT Procedures
 Select the extrinsic factors to be accelerated. Typical storage for
ASLT procedures are shown below. Normally 2 test temp. are used
Type of Food
Test Temp (℃)
Control (℃)
Frozen
-7, -11, -15
<-40
Chilled
5,10,15,20
0
25,30,35,40,45
-18
25,30,35,40
4
Dry and Intermediate
moisture foods (IMF)
Canned
Source: Robertson, 2013
 Determine duration of storage using the hypothetical shelf life plot
or conduct open-ended ASLT (𝑄10 𝑣𝑎𝑙𝑢𝑒 𝑛𝑜𝑡 𝑘𝑛𝑜𝑤𝑛) using a
minimum of 3 test temp
36
Official (Closed) and Non-Sensitive
ASLT Procedures
 Determine test frequency. Can use the following to determine:
∆𝑇
𝑓2 = 𝑓1 𝑄10 10
𝑓1 = 𝑡𝑖𝑚𝑒 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝑡𝑒𝑠𝑡𝑠 𝑎𝑡 ℎ𝑖𝑔ℎ𝑒𝑠𝑡 𝑡𝑒𝑠𝑡 𝑡𝑒𝑚𝑝 𝑇1
𝑓2 = 𝑡𝑖𝑚𝑒 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝑡𝑒𝑠𝑡𝑠 𝑎𝑡 𝑎𝑛𝑦 𝑙𝑜𝑤𝑒𝑟 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑇2
∆ 𝑇 = 𝑇𝑒𝑚𝑝 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝑇1 𝑎𝑛𝑑 𝑇2
 Tabulate the total samples (including control) to be stored in
each test condition
 Conduct ASLT and plot data whenever available
 Estimate shelf life and plot shelf life graph to estimate the
potential shelf life under normal conditions
37
Official (Closed) and Non-Sensitive
Problems Associated with ASLT
 Errors associated with sensory evaluation or analytical
testing
 Change in phase (e.g. solid fat to liquid) as temp. increase
that could accelerate certain reactions
 2 reactions with different 𝑄10 might result in reaction
with higher 𝑄10 to predominate at higher temperature
which may be the other way under normal storage
temperature
38
Official (Closed) and Non-Sensitive
Problems Associated with ASLT
 Increase temp can cause Aw of dry foods to increase
resulting in increase in reaction rate for products with low
Aw inside sealed package
 Gas solubility (esp. oxygen in fat/water) decreases by
approx. 25% for every 10℃ increase in temp
 Foods packed in low barrier package may have higher
moisture loss if stored under high temp/low humidity
chamber
 High temp. may cause protein denaturation which might
increase/decrease reaction rate
39