Shelf Life StudiesBasics – Concepts – Principles

Presented by

Carol ZweepManager – Packaging Services, GFTC

mocon®

Advanced Packaging Solutions

Shelf-life Study Definition

A shelf-life study is an objective means to determine how long a product can

reasonably be expected to keep, without an appreciable change in quality, safety &

character

Shelf Life Factors

An acceptable shelf life is to allow desired sensory, chemical, functional, microbiological and physical characteristics of the product to be retained.

These are called the “End Of Shelf life Parameters” or EOSL’s

Tests employed to measure shelf life need to be product-specific, taking into account the ESOL’s

Thus…The exact test procedure is unique for each product

Shelf Life Evaluation

Microbial examinationChemical analysis (i.e. vitamin degradation)Physical testing (i.e. color or viscosity change)Sensory evaluation

Note: Key part of establishing usefulness of any analytical measurement is correlation with sensory quality

Factors Influencing Shelf Life

Initial quality of the food Inherent nature of the product Processing methods Barrier properties of the packaging Transportation and storage conditions

(temperature & relative humidity)

Food Deterioration

Shelf Stable Food

Perishable Food

Chemical

Vitamin Degradation,

Oxidation

Microbiological

Spoilage &Pathogenic

Microorganisms

Physical

Breakage,Bruising &Moisture Migration

Chemical

Enzyme Activity,Vitamin

Degradation,Oxidation

Physical

Breakage&

Moisture Migration

Microbiological Activity

Spoilage Microorganism

Pathogenic Microorganism

Food Spoilage

Off color Off flavorOff odor

Off textureGas formation

Food Borne Illness

Infection (Microorganism)

Intoxication (Pre-formed toxin)

Microbial Activity

Growth depends on environmental conditions

Different microorganisms grow in different environments and at different rates

Factors Influencing Microbial Growth

Nutrients & chemical properties of food Water Temperature Acidity Oxygen Chemicals

Water Activity of Foods or aw

Water activity (aw) is the term used to describe availability of water

It is defined as the vapor pressure of water divided by that of pure water at the same temperature; therefore, pure water has a water activity of exactly one.

aw is reduced by: drying, freezing, and addition of solutes (sugar, salt)

Why is water activity important?

Controlling microorganism growthMicroorganisms need water and grow well with aw between 0.91 to 0.99. In low moisture, microorganisms survive, but cannot grow

Controlling non-enzymatic reactionsFoods containing proteins and carbohydrates, for example, are prone to non-enzymatic browning reactions, called Maillard reactions which are rate dependent with aw

Slowing down enzymatic reactionsMost enzymatic reactions are slowed down at water activities below 0.8.

Preventing Microbial Spoilage

1. Create conditions unfavorable for microbial growth Reduce temperature Reduce water activity Lowering pH Modify atmospheric condition Add preservatives (sodium benzoate, sorbic acid,

propionic acid, sulfur dioxide, sulfites, nitrites and nitrates)

2. Kill microorganisms Heat treatment (Retort & UHT Aseptic) Gentle processing techniques i.e. HPP

Approaches to Shelf Life Testing

Direct method

Indirect method

Storing the product under selected conditions for a period of time longer than the expected shelf life and checking it at regular intervals to see when the product begins to deteriorate.

Selected conditions typically take into account the proposed processing, packaging, storage and distribution characteristics

Determination of shelf life by the direct method

Determination of shelf life by the indirect methods

Indirect methods predict the shelf life of a product without running a full length storage trial and are useful for products with long shelf lives.

Method Examples

Cold Cuts CookiesMethod: Direct IndirectDesired Shelf Life: 21 days 12 monthsActual Test Time: 21 days 8 weeksTemperatures: 4,8,10oC 20,30,40oCHumidity: 20% 50% or 90%Microbial: aerobic aerobic

` yeast yeast mold moldpsychrophiliccoliformsalmonella

Color: important n/aTexture: important importantTaste: important importantInspection: 1-2 days 1-2 weeks

Indirect Methods

Accelerated shelf life studies: The test period is shortened by deliberately

increasing the rate of deterioration. This is usually done by increasing the storage temperature.

Note: Accelerated procedures can only be used if the relationship exists between the storage behavior under ambient storage regime and the under an accelerated condition.

Indirect Methods

Predictive models: Uses information from a database to predict

bacterial growth under defined conditions (temperature, pH, water activity, etc) . This can be used to calculate the shelf life of a food.

The shelf life should be verified by direct method.

Accelerated shelf-life studies:

“The Rule of Ten”

Temperature Coefficient (Q10)

Q10 is a unitless quantity.

Q10 is the factor by which the rate increases when the temperature is raised by ten degrees.

For typical chemical reactions, Q10 values are 2.0

Temperatures MUST be in 0C or 0K

The Rule of Ten

The temperature coefficient (Q10) represents the factor by which the rate (R) of a reaction increases for every 10-degree rise in the temperature (T).

Example:

T1 T2 T3

20oC 30oC 40oC

R1 R2 R3

15 24 38

Example calculations

Q10 = (24/15)(10/(30-20)) = 1.61 = 1.6

Q10 = (38/24) (10/(40-30)) = 1.581 = 1.58

Here we find that the actual Q10 value is 1.6 not 2

How Q10 values can be appliedA (Accelerated Aging Rate) = Q10

((Te - Ta)/10)

Where... Ta = Ambient TemperatureTe = Elevated TemperatureQ10 = Reaction Rate

And...B (Accelerated Aging Time Duration) = Desired Real Time/A

FOR EXAMPLEIf the desired expiration date of the product is one year, and the test temperature is chosen to be 55C, Q10 is 2; the AATD is determined as follows...

A = 2 ((55-22)/10) = 9.85 B = 365 days/9.85 = 37.06 days or B = 37 days for every year of desired shelf life

ACCELERATED AGING EQUIVALENCY TABLE

based on Q10 =2 ambient Temp. = 22C

DEGREES C

DEGREES F

1 YEAR SHELF LIFE

EQUIVALENCY (WKS)35 95 21.1

40 104 14.9

45 113 10.6

50 122 7.5

55 131 5.3

60 140 3.8

How Q10 values can be applied

B = 37 days for every year of desired shelf life

Summary- we have just scratched the surface!

Shelf life studies can be complex and need to be product specific

Shelf life studies require detailed information about the product to establish the End Of Shelf Life parameters

Water activity can be a critical aspect of shelf life studies

Direct methods provide the most accurate results and should be used for products with shorter shelf lives (perishable)

Accelerated studies can be used to provide results for products with longer shelf lives (shelf stable) in a shorter time period.

With verification, Q10 value can be a useful tool for accelerated studies

Product Shelf Life Case Study

Presented by

Alan ShemaMOCON

Product Manager – Consulting & Testing Services

mocon®

Advanced Packaging Solutions

Overview:

A leading manufacturer of chip snack foods wants to increase its current shelf life from 16 weeks to 36 weeks.

Testing will include an accelerated shelf life study to analyze packaging material changes and the impact of M.A.P. Nitrogen gas flush.

The manufacturer supplied product samples packaged in various film structures plus samples that have been nitrogen gas flushed in one particular film.

Testing Proposal:All samples were stored at accelerated/elevated temperature & humidity conditions, approximately 110F and 90% - 100% RH for a period of about 5 – 6 weeks. Test samples were pulled from storage weekly and tested for the following:

Water Activity Texture Oxidation of Fats Oxygen Head Space content Moisture Content Human Sensory for taste, odor, color an appearance

Figure 5.  Water activity of chips with accelerated storage.

Figure 6.   Water activity of chips with ambient storage.

Figure1. Texture of chips with accelerated storage.

Figure2. Texture  of  chips with ambient storage

Figure 9.  TBAR value for chips under accelerated conditions

Figure3.  % moisture for chips with accelerated storage.

Figure4. % moisture for chips with ambient storage.

Shelf Life:

To predict the end of shelf life, a Q10 value was determined. For this product the value was 2.19 based on rates of moisture change at 45oC and 25oC.

Texture measurements and sensory evaluation indicate that end of shelf life is reached at a moisture level of 2.5 %.

At this moisture level the chips were tough, chewy, and had a stale taste. Based on this end of shelf life parameter the predicted shelf life at 25°C (ambient) was calculated.

Table 1.  Predicted shelf life at 25°C

Film Shelf life (wks) at 25°C

A Clear Film 16.8

B NON MAP 64.6

B MAP 86.0

Recall that customer stated their current shelf life is 16 weeks

Thank YouMOCON Inc.

webinars@mocon.com

Presenters:

Alan Shema – CTS Product Manager, MOCON INC.ashema@mocon.com

Carol Zweep – Manager - Packaging Services, Guelph Food Technology Centre

czweep@gftc.ca

Mocon’s Advanced Packaging Solutions

Modes of Food DeteriorationShelf‐life Modeling and StudiesMicrobial StudiesAccelerated Aging StudiesChemical and Physical Analysis of food and packagingGas Mix OptimizationMAP Systems AuditsShelf‐life OptimizationTransportation TestingHuman evaluation panels

Questions??

Email webinars@mocon.com if you have any further questions or comments.

A link to view the recorded presentation will be sent to you within 24 hours

following the seminar.

Upcoming Events

MOCON Webinars:Introduction to Modified Atmosphere Packaging I – June 8th at 10am CentralIntroduction to Modified Atmosphere Packaging II – July 13th at 10am Centralwww.mocon.com/events.php to register

GFTC Course:Shelf Life Determination & Food Safety – June 14, 8:30am – 4:30pmContact Erin Moore at emoore@gftc.ca or www.gftc.ca to register

Trade Show:GFTC is part of the PACKEX show (June 21-23, Toronto Ontario).Exhibiting (Booth #781) and speaking at the Innovation Briefs.www.packextoronto.com for more information