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Examining Simplified Shelf Life Testing Methods
Dr. Brady Carter discusses simplified methods for determining product shelf life, emphasizing the influence of intrinsic properties like water activity and extrinsic factors like temperature and humidity on shelf stability. He outlines a systematic approach for accelerated shelf life testing, highlighting the importance of controlling water activity, tracking mode of failure, and using a moisture analysis toolkit. The presentation also covers the role of packaging in maintaining desired water activity levels and provides guidance for establishing appropriate best by dates based on empirical data.
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Examining Simplified Shelf Life Testing Methods
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- 3. HOUSEKEEPING ITEMS 45 minutes ofpresentation 15 minutes for questions Use chat pane for Q&A Recording/slides will be sent out following presentation
- 4. SPEAKER INTRODUCTION Examining Simplified ShelfLife Testing Methods Dr. Brady Carter, Director of Food Science METER Group, Inc. USA
- 5. WHAT IS SHELFLIFE? The practical time a product remains desirable to the consumer Used to translate to a best by date Not regulated for most products Dependent upon the intrinsic properties of the product such as • Water activity • Matrix type • Ingredients Dependent on extrinsic factors such as • Storage humidity • Storage temperature • Packaging
- 6. WHAT WILL ENDSHELF LIFE? Microbial spoilage Loss of flavor Browning Oxidation Moisture migration Loss of texture Nutrient loss
- 7. HOW DO YOU DETERMINESHELF LIFE? Guess Estimate based on similar products on the market Store product and observe until it becomes unacceptable • What do you track? • How do you test it? Accelerated shelf life testing • How do you use data to determine real shelf life?
- 8. WHAT IS SHELFLIFE SIMPLIFIED? Step-by-step approach to determining shelf life Eliminate unlikely mode of failures Use simplest method to track mode of failure Set up straightforward experiment at accelerated conditions Use MOISTURE ANALYSIS TOOLKIT to model and predict shelf life
- 9. STEPS TO SHELFLIFE SIMPLIFIED Question 1: What is the expected water activity of my product at typical storage temperature? Question 2: At that water activity, what is the most likely mode of failure? Water Activity >0.85 • Microbial Spoilage Water Activity 0.70-0.85 • Microbial Spoilage • Chemical Instability Water Activity 0.40-0.70 • Chemical Instability • Texture • Moisture Migration Water Activity 0.20-0.40 • Texture • Caking and Clumping Water Activity <0.20 • Chemical Instability
- 10. SHORTBREAD COOKIE Question 1:What is the expected water activity of my product at typical storage temperature? Question 2: At that water activity, what is the most likely mode of failure? Water Activity 0.40-0.70 • Chemical Instability • Texture • Moisture Migration 0.40 aw
- 11. GENERAL EXPERIMENTAL DESIGN Use actual product Controlthe water activity and temperature • Usually 3 water activities at 3 temperatures Track progress of mode of failure Collect time vs. quantity change to determine rate Model collected data accounting for both temperature and water activity
- 12. CONTROLLING WATER ACTIVITY ANDTEMPERATURE Control humidity with a salt slurry or humidity pack Evacuate air in chamber if needed Small enough to fit several in oven at controlled temperature Clear lid allows for tracking color changesSensors can be used to track gas concentrations in air
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- 14. DERIVATION OF HYGROTHERMAL TIME EyringEquation for Rate Change f∞= fo 𝑒 "# $% ΔG = Ea – BRTaw r = roexp(Baw – Ea/RT) Hygrothermal Time Rate = roexp(Baw – Ea/RT) Where ro, B, and Ea/R are derived empirically through modeling 0 0.005 0.01 0.015 0.02 0.025 20 25 30 35 40 45 50 Rate Temp 0.43 aw 0.5 Substituting ΔG into the Eyring equation and using common notation for rate gives Where R is the gas constant, T is the temperature and ΔG is Gibbs Free energy, which is defined as
- 15. MODEL PERFORMANCE Rate =roexp(Baw – Ea/RT) ro = 6.9X106 B = 1.8 Ea/R = 6578.5 Good agreement between predicted and measured rates Successfully used to model – Aspartame loss – Tbar lipid oxidation – Lysine loss – Browning reaction R² = 0.96254 0 0.005 0.01 0.015 0.02 0.025 0.000 0.005 0.010 0.015 0.020 0.025 PredictedRate Measured Rate
- 16. REAL-TIME SHELF LIFE 25%Loss aw Temp Time 15% Loss 30% Loss 30% Left 0.45 25C 14 Days 0.35 25C 14 Days Shelf Life (θ) 14 Days 28 Days 0.55 25C 8 Days 36 Days 0.45 22C Take Measurement ? Days
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- 18. TEXTURE STABILITY FOR SHORTBREADCOOKIES Texture –Hardness testing with Perten TVT6700 texture analyzer Sensory –20-member untrained sensory panel –Random sample distribution –9-point Hedonic Scale –Asked to rate Appearance, Aroma, Color, Flavor, and Overall
- 19. DDI CRITICAL WATER ACTIVITY -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.00 5.00 10.00 15.00 20.00 25.00 00.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 MoistureContent(%wb) Water Activity 25C 35C 40C 25C 2nd Der 35C 2nd Der 40C 2nd Der
- 20. TEXTURE ANALYSIS 0 5 10 15 20 25 30 0.250 0.3000.350 0.400 0.450 0.500 0.550 0.600 0.650 0.700 0.750 0.800 0.850 0.900 Crispness(N) Water Activity 25C 35C 40C Fermi 25C Fermi 35C Fermi 40C B RHc’s from DDI awc from Fermi Modeling
- 21. SENSORY VS. WATERACTIVITY AND TEMPERATURE 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0.2 0.3 0.4 0.5 0.6 0.7 0.8 OverallSensoryScore Water Activity Sensory Score Shortbread Cookies 25C 35C 45C
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- 23. SHORTBREAD COOKIE Question 1:What is the expected water activity of my product at typical storage temperature? 0.40 aw Question 2: At that water activity, what is the most likely mode of failure? Texture Step 3: Identify ideal water activity range <0.50 aw Step 4: Choose appropriate packaging
- 24. STEP 4: ROLEOF PACKAGING Package permeability and storage humidity determines the water activity of the product Packaging models can be used to predict the water activity in a package at any storage humidity Models can also be used to determine packaging needed to achieve a specific shelf life Combining packaging models with shelf life testing data and models provides a real time shelf life Fick’s Law ( )s wf wike a a WVTR E x - = = Evaporation H20 H20 H20 aw in aw out k/x k/x k/x
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- 26. WHAT TO DOWITH SHELF LIFE INFORMATION? Set best by date based on actual information using a conservative set of storage conditions • Determine worse case shelf life if abuse conditions occur Process product to ideal water activity that maximizes shelf life • Verify using water activity testing in QA • Fast 5-minute test • Moisture content not enough Package in appropriate packaging Set aside some product and store to predicted shelf life at normal conditions
- 27. CONTACT US FOR MOREINFORMATION Brady Carter, PhD Phone: (509) 332-2756 / (800) 755-2751 Web: www.metergroup.com Email: brady.carter@metergroup.com