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Guidelines for the Generation of

Guidelines for the Generation of

Guidelines for the Generation of

Guidelines for the Generation of

Microbiological

Microbiological

Microbiological

Microbiological Shelf Life Data

Shelf Life Data

Shelf Life Data

Shelf Life Data

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Version control

Version control

Version control

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AMENDMENT

AMENDMENT

AMENDMENT

AMENDMENT
Version No.

Version No.

Version No.

Version No.

Date

Date

Date

Date

Change

Change

Change

Change

1

28.01.11

New document

INDEX

INDEX

INDEX

INDEX

Page

1. Bought In

4

1.1 Applicable products

4

1.2 Considerations

4

1.3 Sampling

4

1.4 Specific Product Requirements

5

1.5 Frequency of Testing & Sample
Storage

5

1.6Additional Information Requirements 6
1.7 Predictive Models and Challenge
Testing

7

1.8 Organoleptic Shelf Life

7

1.9 Enterprise

7

Appendix 1 – Bought-In Microbiological
Shelf Life

8

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Aim:

Aim:

Aim:

Aim:

The shelf life of a product is the time after production during which it remains
acceptable for consumption. The shelf life must be set before the product is
launched by either Food Technology or Food Safety Specialist to ensure the product
will, when stored and handled under the recommended conditions:

1) Remain safe
2) Retain its desired sensory, chemical, physical and microbiological

characteristics so it is of an acceptable quality that we are happy to be
associated with

The end of shelf life may be determined by the potential for growth of the micro-
organisms that are likely to be present or able to cross-contaminate the product or
by its organoleptic properties. This will be determined through the product shelf life
study.

Once the initial study has been carried out, it is important that the shelf life of a
product is re-assessed regularly after launch, which for most chilled perishable
products will be at a minimum yearly.

The guideline below details Morrison’s expectations for what should be included in
shelf life studies carried out on both bought-in and in-store prepared products.
However, as it is not possible in a guideline document like this to provide a shelf life
testing protocol that will cover every product type, any products which do not fit
this must be discussed with your Technical Manager so that a protocol can be
agreed to obtain the most realistic shelf life evaluation for that product.

It should also be noted that Morrisons do not accept accelerated shelf life
testing due to the potential inaccuracy of the results – time for a shelf life
study to be carried out over the full life of the product should be built into
the product development schedule for all applicable products. Any
exceptions to this must be agreed with the relevant Technical Manager and
Company Microbiologist.

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1. Bought

1. Bought

1. Bought

1. Bought----In (including Market Street ingredients)

In (including Market Street ingredients)

In (including Market Street ingredients)

In (including Market Street ingredients)

1.1

1.1

1.1

1.1 Applicable Products

Applicable Products

Applicable Products

Applicable Products

The following products require a microbiological shelf life study to be carried out
before launch:

1) Chilled perishable (e.g. ready meals, pies, sandwiches, bagged salads, etc)
2) Ready-to-Eat frozen products (e.g. ice-cream, cream cakes) or those with >1d

shelf life at <5

0

C post defrost

3) Ambient bakery products (Aw <0.87 then yeasts and moulds only as a

spoilage indicator)

4) Raw meat and poultry

This applies to both bought in products and those made in store

For all other products the shelf life should be determined by its organoleptic
qualities over the shelf life. This must include shelf life of the product once opened
if the customer is recommended to consume the product within a particular time
(e.g. jarred pesto, jam, etc).

1.2

1.2

1.2

1.2 Considerations

Considerations

Considerations

Considerations

The micro-organisms tested should at a minimum be those detailed in Morrison’s
microbiological specification. The following should also be taken into consideration
when determining any additional micro-organisms to test for:

- raw materials used
- product manufacturing process
- key finished product parameters (e.g. pH, Aw)
- finished product packaging
- any preservatives present
- how the customer will handle the product

1.3

1.3

1.3

1.3 Sampling

Sampling

Sampling

Sampling

Key points to note:

a) Samples tested must be from a pre-production run not

not

not

not a kitchen sample to

simulate manufacturing conditions

b) Product tested must be worst case unless with previous agreement from the

relevant Technical Manager – i.e. ingoing ingredients used at their
maximum ingoing shelf life

c) Seasonal variation may need to be taken into account for those products

containing uncooked produce as microbial loading/quality may vary through
the year. If worst case produce is not available at the point of the initial shelf
life trial then the trial should be repeated when available to ensure this
seasonal variation is captured.

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d) A representative composite sample of the product should be taken
e) In addition, if the product is multi-component or a multipack of different

flavour varieties (e.g. ready meal with separate sauce and vegetables, triple
pack sandwich) then the components should be tested separately and the
maximum shelf life based on the worst-performing component

f) A minimum of 3

3

3

3 different samples are required

1.4

1.4

1.4

1.4 Specific Product Requirements

Specific Product Requirements

Specific Product Requirements

Specific Product Requirements

The following details some specific product requirements:

a) Pizza/Sandwiches/Pies – test topping/filling only

only

only

only

b) Cream desserts -test cream and high-risk components only (e.g. custard)
c) Mould-ripened cheese should be tested for

Listeria

in the rind due to the

elevated pH making it more likely for it to be found here

d) MAP/Gas-Flushed Products – shelf life study should include ‘open life’ of

product recommended to customer on the packaging. This needs to be done
‘worst case’, i.e. last days of total product shelf life

1.5

1.5

1.5

1.5 Frequency of Testing

Frequency of Testing

Frequency of Testing

Frequency of Testing & Sample Storage

& Sample Storage

& Sample Storage

& Sample Storage

The frequency at which microbiological analysis should take place should be based
on the following:
Shelf life 1-4 days: Daily
Shelf life 5 – 14 days: Every 2 days
>14d: Weekly with 3 tests in the final week

Analysis should be carried out up to End of Life + 20% of the total life. Any
variation to the above frequencies must be agreed with the appropriate technical
Manager

The study must take into account the temperatures the product is subjected to
throughout its shelf life, including manufacturing, distribution, display, and
customer handling.

Process Stage

Temperature (

0

C)

Distribution

0 - 5

0

C

Retail

0 - 5

0

C

Customer Purchasing

22

0

C

Customer

8

0

C

Chilled products must be held at 22

0

C for 2hrs to mimic customer purchasing and

then at 8

0

C for minimum 20% of their shelf life (30% if >25d)

Bakery samples should be held at 20

0

C and at 30

0

C for worst-case customer

handling

All results should be submitted on Appendix

All results should be submitted on Appendix

All results should be submitted on Appendix

All results should be submitted on Appendix 2

2

2

2

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1.6 Additional Information Requirements

1.6 Additional Information Requirements

1.6 Additional Information Requirements

1.6 Additional Information Requirements

The shelf life study only assesses the growth of those micro-organisms which are
likely to be present in or have cross-contaminated the batch of product being
analysed. As it is unlikely that food pathogens will be present in products if good
manufacturing practice has been followed, e.g.

Cl.botulinum

, the effect of the

product formulation on growth on these organisms will not be evaluated during
shelf life studies. This means that shelf life study can not be used to establish
product safety with respect to pathogens. For those products which get an
extended shelf life due to their manufacturing process, packaging or inherent
product parameters details of these need to be included in the Enterprise
specification under ‘Finished Product Parameters’ in the ‘Comment’ box to justify
how the product is safe.

Product Type

Possible Control

Naturally acid/acid formulated chilled
products (e.g. dips, yogurt, salad dressings)

pH

Ready Meals, Soups, Custard

Hot filling temperature
CAPCOLD
Sous Vide

Chilled sponges/jellies

pH
Aw

Cheese

% moisture, pH, % salt

Naturally acid/acid formulated ambient
jars/cans (e.g. pickles, jam, olives)

pH

Low acid ambient jars/cans (e.g. canned
tuna, canned soup)

F

0

Alcohol Creams

% aqueous alcohol

Fresh Pasta

Aw

MAP Bread (e.g. part-baked rolls, naan)

Aw & pH crust & crumb

UHT

Time & Temperature

Cold Smoked Fish

% Aqueous salt

Cooked cured meat/Pate

ppm nitrate/nitrite, % aqueous salt

Fermented Meat

pH
Aw

The values required from the above can be widely found in industry guidelines – for
further detail of any Morrisons specific requirements please contact your Morrisons
Technical Manager.

NB: For all vacuum-packed and MAP products product shelf life must not exceed
10d unless additional controlling factors are in place (as above) or the product has
been put through a predictive model/challenge test (see section 1.7)

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1.7

1.7

1.7

1.7 Predictive Models and

Predictive Models and

Predictive Models and

Predictive Models and Challenge

Challenge

Challenge

Challenge Testing

Testing

Testing

Testing

Where a product shelf life is required which is longer than the typical safe shelf life
for the product, and there is no intrinsic stability control present (as listed in section
1.6) a predictive model may be used. Predictive models allow the growth rate of the
relevant shelf life limiting microorganisms to be predicted in the product over the
desired life based on its parameters (e.g. pH, Aw, % salt, etc). They are however
limited in that the growth rate will be predicted ‘worst case’ and typically will not
exactly mimic that that would be found in the product as limiting factors such as
competing microorganisms, organism stress, etc, are not taken into account.
However they are a useful tool in assessing whether an atypical shelf life can be
safely achieved or not.

In addition, as it needs to be demonstrated that for all ready to eat chilled foods
able to support the growth of

L. monocytogenes

that if contaminated the organism

will not exceed a level of >100 cfu/g by the end of its shelf life predictive models
can also be used for this.

If, when used, the predictive model does not demonstrate that the requested shelf
life is safe then a challenge test MUST be carried out. Challenge testing is where
food is deliberately inoculated with known microorganisms and/or stored under a
range of controlled environmental conditions in order to determine if those
organisms can grow in the product. It is not quick or simple and cost can potentially
be inhibitive, and so should only be resorted to if all other methods of assessing
safety/stability of the product have failed and if product reformulation/a process
change is not feasible. In these cases, prior agreement must be made with the
appropriate Technical Manager, and the proposed protocol reviewed by the
Company Microbiologist before any work commences who will, if required, seek
outside expert advice.


1.8

1.8

1.8

1.8 Organoleptic Shelf Life

Organoleptic Shelf Life

Organoleptic Shelf Life

Organoleptic Shelf Life

The standards for organoleptic qualities for the product should be determined in
conjunction with both Product Development and Commercial teams, and take place
as part of the NPD process


1.9

1.9

1.9

1.9 Enterprise

Enterprise

Enterprise

Enterprise

Copies of any microbiological or organoleptic shelf life trials carried out must be
attached to the Enterprise specification for that product. Failure to supply the
relevant information will lead to the specification being rejected.

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APPENDIX 2

APPENDIX 2

APPENDIX 2

APPENDIX 2

Wm Morrisons Supermarkets PLC

Wm Morrisons Supermarkets PLC

Wm Morrisons Supermarkets PLC

Wm Morrisons Supermarkets PLC

Product:

Product:

Product:

Product:

Supplier:

Supplier:

Supplier:

Supplier:

Laboratory:

Laboratory:

Laboratory:

Laboratory:

Storage conditions:

Storage conditions:

Storage conditions:

Storage conditions:

Shelf life required:

Shelf life required:

Shelf life required:

Shelf life required:

Date Tested:

Date Tested:

Date Tested:

Date Tested:

Time (Day,

week, etc)

Micro

Micro

Micro

Micro----Organism

Organism

Organism

Organism

Temperature

Temperature

Temperature

Temperature

(

0

C)

TVC

(cfu/g)

0

4

0

C

1

2

3

8

0

C

Approved shelf life:

Approved shelf life:

Approved shelf life:

Approved shelf life:

All microorganisms tested should be as Morrison’s Microbiological Testing Specifications