Ever wondered what the expiration date on your food REALLY meant? Our food safety experts explore the reasoning and protocol behind microbiological shelf life evaluations. Learn who controls this important method in food testing and how to store your food properly.

1. Microbiological
Shelf Life Evaluations
Ivy Cho Heather Smith
Business Development Director Research Microbiology Assistant Manager
ivyc@abcr.com heathers@abcr.com

2. What does shelf life mean?
• It is the extent of time for
which a food remains
usable, acceptable for
consumption, or saleable
from manufacturing until
reaching the “best before
date”, “sell by date”, or
“use by date”.
– These terms all relate to the
quality of the food
Microbiological Shelf Life Evaluations

3. Terms used to describe shelf life
• A "Sell-By" date tells the store how long to display
the product for sale. You should buy the product
before the date expires.
• A "Best if Used By (or Before)" date is
recommended for best flavor or quality. It is not a
purchase or safety date.
• A "Use-By" date is the last date recommended for
the use of the product while at peak quality. The
date has been determined by the manufacturer
of the product.
• "Closed or coded dates" are packing numbers for
use by the manufacturer.
Microbiological Shelf Life Evaluations

4. Shelf life influences
Growers/ Producers Other suppliers
Manufacturers
Distributors
Retailers
Consumers
Microbiological Shelf Life Evaluations

5. Factors that affect the shelf life
• Moisture
• Water activity
• Fat/oil content
• Alcohol content
• Flavor loss
• Texture changes
• Color changes
• Acid content
• pH
• Light exposure
• Microbial spoilage
Microbiological Shelf Life Evaluations

6. Real time shelf life evaluations
• This is applicable in ambient,
refrigerated, and frozen foods where the
storage temperature is real time.
• Microbiological
evaluations are
applicable in
refrigerated (and
sometimes ambient)
foods.
Microbiological Shelf Life Evaluations

7. Real time shelf life
• Products are stored under normal conditions for the
length of time desired by the client. Manufacturer
may wish to evaluate products for a time length
greater than the expected shelf life to determine
the deterioration point
Microbiological Shelf Life Evaluations

8. Microbial Quality Shelf Life Evaluation
(refrigerated foods)
• Products analyzed for applicable quality
indicators (product specific)
– Aerobic Plate Count
– Gram-negative Bacteria count
– Lactic Acid Bacteria Count
– Yeast & Mold Counts
• Assesses microbiological quality of a product
(not safety)
• Results best understood by concurrent microbial
and organoleptic quality evaluations
Microbiological Shelf Life Evaluations

9. Total plate count humor

10. Microbial Quality Shelf Life Evaluation
(ambient foods)
• Microbiologically safe/stable foods
– Organoleptic Quality Shelf Life
• -Microbiologically safe foods/not
microbiologically stable under
ambient storage conditions
– Organoleptic Quality Shelf Life
– Microbial Quality Shelf Life
Microbiological Shelf Life Evaluations

11. Types of Microbiological
safety testing
1. Chemical testing
2. Product Assessment
3. Challenge study
4. Growth studies
5. Lethality studies
Microbiological Shelf Life Evaluations

12. 1. Chemical testing
– Safety can often be addressed via minimal
chemical testing, e.g.:
• Water activity (aw)
• pH
• NaCl
Microbiological Shelf Life Evaluations

13. 2. Product Assessment
– Predictive modeling
and safety
assessment based on
chemical
parameters, storage
temperature, shelf
life, packaging, etc.
Microbiological Shelf Life Evaluations

14. 3. Challenge Study
– Products inoculated with pertinent
pathogens
– Inoculation level depends on study
objective
– Storage temperature and shelf life mimic
worst case scenario
Microbiological Shelf Life Evaluations

15. 4. Growth studies
– Microbial levels monitored to detect
outgrowth or control of pertinent pathogens
• Example: Listeria monocytogenes challenge study
in refrigerated deli products
Microbiological Shelf Life Evaluations

16. 5. Lethality studies
– Verify target lethality (e.g., 5-log
reduction) in pertinent pathogens
• Example: 5-log reduction of acid-tolerant
pathogens in cold-packed, acidified hot
sauce
Microbiological Shelf Life Evaluations

17. Questions?
For additional
information, please
contact us at
352.372.0436 or visit our
website at abcr.com
Microbiological Shelf Life Evaluations