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How To Measure Water Activity In One Minute

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In this 15 minute webinar, food scientists Mary Galloway and Dr. Zachary Cartwright talk about the theory and application of one-minute water activity readings, including:

- the physics-based model and hybrid analytics breakthroughs that make a one minute reading possible
- why these techniques work for samples that usually have long read times
- comparison to traditional first-order “fast” or “quick mode” readings
- pros and cons from Mary’s testing experience in the food lab

The webinar will be followed by a ten minute Q & A.

Presenters
Zachary Cartwright is a lead food scientist at METER Group. He helps customers achieve complete moisture analysis of their products and is an expert in the use of the Vapor Sorption Analyzer (VSA). He has a Ph.D. in food science from Washington State University and a bachelor’s degree in biochemistry from New Mexico State University.

Mary Galloway is the application scientist for METER Food and manages the Food Research & Development lab. She is a contributing author on several publications concerning water activity and its influence on physical properties. Mary uses her years of experience to help customers understand and solve their moisture-related product issues.

Published in: Food
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How To Measure Water Activity In One Minute

  1. 1. HOW TO MEASURE WATER ACTIVITY IN ONE MINUTE MARY GALLOWAY ZACHARY CARTWRIGHT, PHD APPLICATION SCIENTIST LEAD FOOD SCIENTIST METER GROUP, INC. USA
  2. 2. Zachary Cartwright, PhD Lead Food Scientist Mary Galloway Application Scientist
  3. 3. CONTENTS THE SCIENCE BEHIND WATER ACTIVITY MEASUREMENTS KEYS TO SPEED USING SPEED TO REDUCE UNCERTAINTY IMPACT OF FAST WATER ACTIVITY KEY TAKEAWAYS Q&A
  4. 4. THE SCIENCE BEHIND WATER ACTIVITY MEASUREMENTS
  5. 5. Several first-order processes, each with a different time constant SAMPLE CHAMBER SENSOR Not only are time constants different from each other, they’re different for different products and can change under different conditions FROM A PHYSICS PERSPECTIVE
  6. 6. KEYS TO SPEED
  7. 7. KEYS TO SPEED
  8. 8. FIRST-ORDER MODEL Well-known engineering strategy Speed up reading by using current data to extrapolate
  9. 9. FIRST-ORDER MODELING Using reading time series data • Obscures several different processes • Need to wait for fast processes to be nearly complete to fit data. Takes much longer than one minute • Results from this method are unsatisfactory (errors unpredictable)
  10. 10. FIRST-ORDER MODELING METER Competitor A Competitor B Aw Time (min) Aw Time (min) Aw Time (min) Equilibration Fast Equil Fast Equil Fast Equil Fast Equil Potato Chips 0.099 7.2 0.104 0.078 10.5 15.2 0.094 0.106 4.3 15.4 Peanut Butter 0.194 5.8 0.134 0.120 31.1 111.4 0.212 0.222 4.0 16.4 Ground Black Pepper 0.365 4.7 0.423 0.370 32.5 11.6 0.428 0.368 3.4 19.9 Dog Kibble 0.425 3.2 0.414 0.419 14.5 26.6 0.408 0.414 3.8 14.9 Craisins 0.504 4.3 0.502 0.500 9.8 18.4 0.522 0.504 3.4 7.9 Beef Jerky 0.716 3.2 0.702 0.696 13.2 16.2 0.712 0.700 3.7 26.4
  11. 11. FIRST-ORDER MODELING Chilled Mirror Competitor A Competitor B Aw Time (min) Aw Time (min) Aw Time (min) Equilibration Fast Equil Fast Equil Fast Equil Fast Equil Potato Chips 0.099 7.2 0.104 0.078 10.5 15.2 0.094 0.106 4.3 15.4 Peanut Butter 0.194 5.8 0.134 0.120 31.1 111.4 0.212 0.222 4.0 16.4 Ground Black Pepper 0.365 4.7 0.423 0.370 32.5 11.6 0.428 0.368 3.4 19.9 Dog Kibble 0.425 3.2 0.414 0.419 14.5 26.6 0.408 0.414 3.8 14.9 Craisins 0.504 4.3 0.502 0.500 9.8 18.4 0.522 0.504 3.4 7.9 Beef Jerky 0.716 3.2 0.702 0.696 13.2 16.2 0.712 0.700 3.7 26.4
  12. 12. SECOND-ORDER MODEL Uses complex modeling process • Second order model developed by physicists • Uses strategies from predictive environmental modeling Requires sample-specific coefficients • Sample needs to be identified so correct coefficients are used Needs 3 readings of a specific sample
  13. 13. SECOND-ORDER MODEL 0 0.005 0.01 0.015 0.02 0.0000 0.0928 0.1130 0.1500 0.1790 0.1793 0.2500 0.3877 0.5000 0.5126 0.5385 0.7406 0.7600 0.7775 0.8291 0.9200 0.9339 0.9840 1.0000 WaterActivityMaxError(aw) Expected Water Activity (aw) Fast aw vs. Final Dew Point aw One-Minute Aw Max Error Final Dew Point aw Max Error
  14. 14. USING SPEED TO REDUCE UNCERTAINTY
  15. 15. ONE-MINUTE READINGS POSSIBLE… “Normal readings” already fast • Readings take typically a couple of minutes Clean instruments • Eliminate materials that will adsorb water Accurate instruments • second order modeling can be applied to make faster If your sensor is slow, you can never get a one-minute reading.
  16. 16. VARIABILITY > ACCURACY VARIABILITY IS A BIGGER ISSUE THAN ACCURACY More measurements will reduce uncertainty better than increased sensor accuracy
  17. 17. Inherent variability makes uncertainty HIGH 10 MINUTES 1 READING UNCERTAINTY = 𝑺𝒕𝒂𝒏𝒅𝒂𝒓𝒅 𝑫𝒆𝒗𝒊𝒂𝒕𝒊𝒐𝒏 𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝑹𝒆𝒂𝒅𝒊𝒏𝒈𝒔 UNCERTAINTY 1 0.3 HOW UNCERTAINTY IS REDUCED FOOD SAMPLE 10 MINUTES 10 READING
  18. 18. HOW UNCERTAINTY IS REDUCED Fast water activity allows you to include more readings in your average to drastically improve uncertainty. If you can get 4 readings, that will cut uncertainty in half. The main source of uncertainty in factories is not taking enough readings. The inherent variability in the product means that one to two readings… is nowhere near enough to characterize aw.
  19. 19. IMPACT OF FAST WATER ACTIVITY
  20. 20. IMPACT OF ONE-MINUTE READINGS
  21. 21. BUSINESS IMPACT A well-known cured meat manufacturer: -Clearing their ovens and cure rooms in a fraction of the time. -40% increase in production throughput (no additional investment). -Saving over $1M in planned investment to scale operations.
  22. 22. BUSINESS IMPACT A prominent oven baked oat bar provider -6 readings went from over an hour to <10 min. -Know with certainty when they can move to packaging. -No unnecessary rework or lost batches. An innovative sunflower seed butter producer -30 min test down to 1 min. -No longer having delays on batch releases.
  23. 23. KEY TAKEAWAYS
  24. 24. QUESTIONS?
  25. 25. METER GROUP USA, INC. 2365 NE Hopkins Court Pullman, Washington 99163 Phone: (509) 332-2756 / (800) 755-2751 Fax: (509) 332-5158 Email: mary.galloway@metergroup.com zachary.cartwright@metergroup.com

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