![Example of Ingredient Mixing
DLP Combined Isotherm
w = ∑φi wi
Ingredient 1 Ingredient 2 Combined
φi = mass fraction of component i
wi = moisture content of component i. 25
Moisture Content (% w.b.)
20
3 2
wi = b3i χ + b2i χ + b1i χ + b0i 15
10
Where b3, b2, b1, and b0 are empirical constants from
the DLP isotherm model and χ is ln(-ln(aw)) 5
0
3 2
w = χ eq b3 '+ χ eq b2 '+ χ eq b1 '+b0 ' 0
0.2
0.4
0.6
Water Activity
0.8
1
Where b3’, b2‘, b1‘, and b0’ are the DLP constants for
the combined isotherm and χeq is ln(-ln(aw(eq)))
b3’ = ∑Φib3i , b2’ = ∑Φib2i , b1’ = ∑Φib1i , b0’ = ∑Φib0i
aw(eq ) = exp[− exp(− χ eq )]](https://image.slidesharecdn.com/2011basicsofwateractivityvirtualseminar-121119010625-phpapp01/85/basics-of-water-activity-virtual-seminar-24-320.jpg)
![Package Performance
α = slope of the isotherm (g/g)
Calculations
Water activity under specific conditions
awo = initial water activity
awc = critical water activity
aw = ha − [(ha − awo ) exp(−t / τ )] pa = atmospheric pressure (kPa)
M = total mass of product inside the
Time Constant
package (g)
α pa M es = saturation water vapor pressure at
τ=
es Ag v package temperature (kPa)
Shelf life prediction of packaging A = package surface area (m2)
gv = package conductance (g m-2 s-1)
⎛ h − a wc ⎞
t shelf = −τ ln⎜ a
⎜ h − a ⎟ ⎟ ha= Humidity of air,
⎝ a wo ⎠
WVTR = Water Vapor Transmission Rate
Determine Package Conductance t = Time in package,
α pa M paWVTR τ = Time constant
gv = =
es Aτ ha es](https://image.slidesharecdn.com/2011basicsofwateractivityvirtualseminar-121119010625-phpapp01/85/basics-of-water-activity-virtual-seminar-26-320.jpg)
basics of water activity virtual seminar
- 1. Basics of Water Activity Brady Weldon Decagon Devices, Inc.
- 2. Objectives § Define Water Activity and Moisture Content § Compare and Contrast Water Activity and Moisture Content § Water Activity and Moisture Content Measurements Methods § Applications for Water Activity and Moisture Content
- 3. Water activity vs. Moisture content § Moisture Content § Quantitative amount of water in a sample on a wet or dry basis. § An extensive property that depends on the amount of material. § Water Activity § A measure of the energy status of the water in a system (Qualitative). § A intensive property that does not depend on the amount of material.`
- 4. Water Activity Defined Correct Definition: Water Activity is a measure of the energy status of the water in a system. Old Definition: Water activity is the amount of “free” or “available” water in a product as opposed to “bound” water. aw = f/fo = p/po Vapor pressure of water above sample @ °C aw = —————————————————— Vapor pressure of pure water @ same °C aw = ERH (%) /100
- 5. Moisture Content Defined § Quantitative measure of amount of water § Empirical measurement with no standard § Loss on Drying – Fick’s Equation gv E = (es − ea ) Pa § Titration 3Z + ROH + I 2 + H 2O → 3ZH + + ROSO3− + 2 I −
- 6. Cheese & Cracker System Cracker and Cheese are placed together in a sealed container 20% Moisture 30% Moisture Which way does water move? Sodium Chloride .753
- 7. Moisture Analysis Comparison Water Activity Moisture Content Measures Energy of Water Amount of “Water” No, empirical Standard Available Yes, salt standards measurement Cost $1000-$10,000 $250-$25,000 Reporting aw units Dry or wet basis % Methods Methods 4 methods 35 methods Sample Little to none Depends on method Preparation
- 8. Water Activity vs. Moisture Content
- 9. Chilled Mirror Dew Point § Advantages § Primary method of measuring vapor pressure (not calibrated) Fan § Highest accuracy Optical Sensor ±0.003aw Mirror § Rapid measurement <5 Infrared Sensor minutes § Measures entire aw range (0.03 – 1.0aw) § High reliability Sample § Disadvantages § Need clean mirror § Readings affected by alcohol and propylene glycol
- 10. Dewpoint Moisture Content § Construct a moisture sorption isotherm for product § Measure water activity (<5 minutes) § Through isotherm the water activity measurement gives moisture content § Product specific § Water activity and Moisture Content by 1 instrument
- 11. Accurate Measurements § Calibration / Verification Standards § Saturated Salt Slurries § Unsaturated Salt Solutions § Temperature § Sample Preparation § Need representative sample § If slicing / grinding – be consistent § Prevent moisture exchange with environment
- 13. AquaLab Series 4TE(V) Large screen and Clam Shell lid design easy to use menus for easier cleaning Same accuracy and repeatability as the O-ring seal for tighter Series 3TE chamber seal Volatiles sensor On board storage now incorporated in to save testing data testing block and can be used with a menu selection, so no need to swap out Can be upgraded to measure moisture a volatile block content and water activity Administrator settings allow user simultaneously control and makes instrument 21 CFR Part 11 compliant when used with AquaLink RG software
- 14. Applications for Water Activity § Water Activity Can Help You: § Control microbial growth § Formulate profitable products § Predict effects of temperature abuse § Control chemical reaction rates § Control moisture migration § Avoid caking and clumping § Predict packaging needs
- 15. Microbial Growth § Scott (1953 & 1957) showed that microorganisms have a limiting water activity level below which they will not grow. § Water activity, not water content, determines the lower limit of available water for microbial growth. Scott,W.J. 1953. Water relations of Staphylococcus aureus at 30ºC. Aust. J. Biol. Sci. 6:549-564. Scott,W.J. 1957. Water relations of food spoilage microorganisms. Adv Food Res 7:83-127.
- 16. Microbial Growth § Growth Limit § Every microorganism has a water activity level below which it cannot grow. aw limit Microorganisms 0.91 Gram Negative Bacteria 0.86 Gram Positive Bacteria 0.88 Yeast (practical limit) 0.80 Production of mycotoxins 0.70 Molds (practical limit) 0.62 Osmophilic yeast 0.61 Xerophilic molds 0.60 Absolute limit for all growth
- 17. Microbial Growth – Hurdle Technology
- 18. Interaction Table A Table A. Interaction of pH and aw for control of spores in food heat- treated to destroy vegetative cells and subsequently packaged. aw Values pH Values 4.6 or less > 4.6 – 5.6 > 5.6 0.92 or less Non-PHF*/non- Non-PHF/non- Non-PHF/non- TCS** TCS TCS > 0.92 – 0.95 Non-PHF/non- Non-PHF/non- PA*** TCS TCS > 0.95 Non-PHF/non- PA PA TCS * PHF means “Potentially Hazardous Food” ** TCS means “Time/Temperature Control for Safety Food” *** PA means “Product Assessment Required” 2005 Food Code
- 19. Interactive Table B Table B. Interaction of pH and aw for control of vegetative cells and spores in food not heat-treated or heat-treated but not packaged. aw Values pH Values < 4.2 4.2 – 4.6 > 4.6 – 5.0 > 5.0 < 0.88 Non-PHF*/ Non-PHF/non- Non-PHD/non- Non-PHF/non- non-TCS** TCS TCS TCS 0.88 – 0.90 Non-PHF/non- Non-PHF/non- Non-PHF/non- PA*** TCS TCS TCS > 0.90 – 0.92 Non-PHF/non- Non-PHF/non- PA PA TCS TCS > 0.92 Non-PHF/non- PA PA PA TCS * PHF means “Potentially Hazardous Food” ** TCS means “Time/Temperature Control for Safety Food” *** PA means “Product Assessment Required” 2005 Food Code
- 20. Formulating for Water Activity § Dehydrate Product § Additives § Edible films and § Ingredients involved in coatings water binding § Keep water from § Humectants: migrating between § salt – (NaCl) the different § sugars – (glucose, fructose, sucrose, components in a syrups) composite samples. § glycols – (glycerol, PEG, § They are located on propylene glycol) the surface or as § amino acids – (glycine, alanine) thin layers between § polymers – (starch, several parts within gums) the product. § acids – (citric acid, lactic acid) § Anticaking agents
- 21. Product Formulation Snack Cake § All 3 components have The image part with relationship ID rId5 was not found in the file. same water activity § 3 components have very different moisture contents § Each component has a unique texture § Icing serves as a moisture barrier for the cake
- 22. Modeling Temperature Abuse Granola Bar Isotherm at 3 different Temperatures § Water activity is temperature 35 dependent 30 Moisture Content (% d.b.) 25 § Most products 20 have a lower water 15 activity value at 10 5 15c 25c lower temperature. 40c 0 § Clausius- 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Water Activity Clapeyron relationship: aw2 ΔH ⎛ 1 1 ⎞ ln =− ⎜ − ⎟ aw1 R ⎜ T1 T2 ⎟ ⎝ ⎠
- 23. Moisture Migration § Moisture migration can lead to: § Solutions to limit § texture changes moisture migration § microbial growth § make components to § degradation reactions same water activity § organoleptic changes § lower aw of high aw component § raise aw of low aw component § retard diffusion § Examples of Multi-domain process within systems § cheese / cracker component § cereal with fruit pieces (viscosity) § baked dough – filling § edible barrier § frozen pizza crust – sauce § separate packaging § ice cream in cone § gelatin capsules
- 24. Example of Ingredient Mixing DLP Combined Isotherm w = ∑φi wi Ingredient 1 Ingredient 2 Combined φi = mass fraction of component i wi = moisture content of component i. 25 Moisture Content (% w.b.) 20 3 2 wi = b3i χ + b2i χ + b1i χ + b0i 15 10 Where b3, b2, b1, and b0 are empirical constants from the DLP isotherm model and χ is ln(-ln(aw)) 5 0 3 2 w = χ eq b3 '+ χ eq b2 '+ χ eq b1 '+b0 ' 0 0.2 0.4 0.6 Water Activity 0.8 1 Where b3’, b2‘, b1‘, and b0’ are the DLP constants for the combined isotherm and χeq is ln(-ln(aw(eq))) b3’ = ∑Φib3i , b2’ = ∑Φib2i , b1’ = ∑Φib1i , b0’ = ∑Φib0i aw(eq ) = exp[− exp(− χ eq )]
- 25. Water Activity and Glass Transition 20 Moisture Content (% d.b.) Large number of water binding sites 15 become available Caking, Clumping, 10 Crystallization, Loss Limited Water of Texture Binding Sites 5 RHc Critical Water Activity 0 Amorphous Metastable State 0 0.2 0.4 0.6 0.8 1 Water Activity *Data is for Spray Dried Milk Powder
- 26. Package Performance α = slope of the isotherm (g/g) Calculations Water activity under specific conditions awo = initial water activity awc = critical water activity aw = ha − [(ha − awo ) exp(−t / τ )] pa = atmospheric pressure (kPa) M = total mass of product inside the Time Constant package (g) α pa M es = saturation water vapor pressure at τ= es Ag v package temperature (kPa) Shelf life prediction of packaging A = package surface area (m2) gv = package conductance (g m-2 s-1) ⎛ h − a wc ⎞ t shelf = −τ ln⎜ a ⎜ h − a ⎟ ⎟ ha= Humidity of air, ⎝ a wo ⎠ WVTR = Water Vapor Transmission Rate Determine Package Conductance t = Time in package, α pa M paWVTR τ = Time constant gv = = es Aτ ha es
- 27. Conclusion § Water Activity is a measure of the energy status of water. § Decagon provides a range of products for measuring water activity § Decagon is always happy to provide application and technical support § Water Activity is important for § Microbial Safety § Chemical Stability § Physical Stability
- 28. Who uses Aw? WHO ARE OUR CUSTOMERS? In the U.S. alone, over 120 universities, 55 analytical labs, 20 government agencies, and hundreds of companies use water activity
- 29. Applications for Water Activity Ø Microbial Growth Ø Hurdle Technology Ø Chemical/Biochemical Stability Ø Physical Properties Ø Moisture Migration Control Ø Compliance with Government Agencies Ø Shelf Life Testing Ø Product Formulation Ø Process Control Ø Quality Control Ø Inspection of Incoming Ingredients Decagon Devices, Inc.
- 30. Microbial Growth • Microorganisms have a limiting water activity level below which they will not grow: v Bacteria ~0.91 v Yeast ~0.88 v Molds ~0.70 • Water activity, not water content, determines the lower limit of available water for microbial growth. Decagon Devices, Inc.
- 31. Microbial Growth Growth limits Every microorganism has a water activity level below which it cannot grow. 0.70 - Practical limit for the growth of Inc. Decagon Devices, mold
- 32. Hurdle Technology Hurdle technology deliberately combines existing and new preservation techniques to establish a series of preservative factors (hurdles) that the microorganisms in question are unable to overcome (jump over). These hurdles may be temperature, water activity, acidity, preservatives, and others. Decagon Devices, Inc.
- 33. Chemical/Biochemical Stability Ø Non-Enzymatic Browning Ø Lipid Oxidation Ø Nutrient Degradation Ø Enzymatic Reactions Decagon Devices, Inc.
- 34. Physical Properties • Texture • Moisture Migration • Powder Flow Properties • Caking and Clumping Decagon Devices, Inc.
- 35. Moisture Migration Multi-Domain Systems • Two distinct regions at different aw • Water moves from areas of high water activity to areas of low water activity. • Driving force for water migration directly related to aw difference. • Rate of migration depends on structure/diffusion properties. Decagon Devices, Inc.
- 36. Moisture Migration Moisture migration can lead to: • texture changes • microbial growth • degradation reactions Examples of Multi-domain systems • cheese / cracker • cereal with fruit pieces • baked dough – filling • frozen pizza crust – sauce • ice cream in cone • gelatin capsules Decagon Devices, Inc.
- 37. Moisture Migration Solutions • make components to same water activity lower aw of high aw component and keep soft raise aw of low aw component and keep crisp • retard diffusion process within component (↑ viscosity) • edible barrier • separate packaging Decagon Devices, Inc.
- 38. Moisture Migration Traditional Fruit Cake • make components to same water activity (flour, sugar, candied fruits, raisins, butter, eggs, nuts) Water activity Moisture Content (% db) Dough 0.857 24.5 Fruits (mixed) 0.862 52.2 Decagon Devices, Inc.
- 39. Compliance Water activity is a critical parameter for compliance with: • FDA’s Good Manufacturing Practices (21CFR) • HACCP – critical control point • ANSI/NSF Standard 75 for shelf stable baked goods • USP Method <1112> Decagon Devices, Inc.
- 40. Food Safety Concerns ? In the United States alone: • 76 million illnesses • 325,000 hospitalizations • 5,000 deaths annually due to foodborne disease Source: Centers for Disease Control (CDC) Decagon Devices, Inc.
- 41. Product Recalls The consequence of a microbiological failure, as it relates to product recalls, can be very costly. • Recalls can cost millions of dollars in product losses and operational delays • Sales may suffer as a result from: - loss of consumer confidence - consumers relating the recall to other products • Company reputation damage. Decagon Devices, Inc.
- 42. Product Recalls The annual medical costs, productivity losses, and costs of premature deaths due to five major foodborne pathogens are estimated to be $ 6.9 billion. (Crutchfield and Roberts, 2000 FoodReview 23(3):44-49) FDA posts recalls and safety alerts on website http://www.fda.gov Many food, cosmetic, and pharmaceutical recalls are due to bacterial (Listeria, Salmonella) or mold contamination. Decagon Devices, Inc.
- 43. Shelf Life Testing • The presence of water influences the shelf life. • Water solubilizes reactants and increases their mobility, both of which can lead to faster deterioration. • Define unacceptable product conditions: microbial growth, chemical status (loss of nutrient), physical properties, sensory. Decagon Devices, Inc.
- 44. Shelf Life Case study: • Bakery company has re-formulated products along with packaging changes to more than double the shelf life of its products. Now at 10 to 17 days • Quality remains constant in terms of texture, flavor, color, etc. Ingredients are sampled directly off delivery trucks to ensure they meet specifications. • The added shelf life is an advantage selling to stores – managers have more time to sell the product – opened new markets. Decagon Devices, Inc.
- 45. Product Formulation (R&D) The water activity concept should be incorporated from the beginning. If you start with the concept of Aw then new products will be safe, have a maximized shelf life, and of the highest quality. Water activity data can be used to predict potential hazards for new products. Decagon Devices, Inc.
- 46. Product Formulation Case Study A pet food manufacturer produced to 8% moisture content. Why? Because at that level he had never had spoilage problems or shelf life concerns. He had a safe product. Then, he used water activity measurements. The aw of his product was 0.50aw. After a little research he understood that he needed only to stay below 0.65aw.
- 47. Product Formulation 0.50aw (8% moisture): 0.65aw (10% moisture) 1000 kg/hour 1020 kg/hour 16 hrs/ day 16hrs/ day 5 days/ week 5 days/ week = 3,840 tons/year = 3,916 tons/year It means 76,800 kilos more every year! Now, let’s assume that this company sells each kilo of their PetFood at US$0.84. Then 76,800 kilos x 0.84 = $64,512 extra in revenues every year! The Results: ü Increase revenues and profits ü Low-cost solution (water is cheap) ü Reduce electricity, heat, etc. ü Same labor, man hours, etc. ü Better product!
- 48. Process Control • aw measurement confirms shelf life, quality, and safety testing data on-line • Control belt speed, oven temperature • Archive information for inspections, customer complaints Decagon Devices, Inc.
- 49. Ingredients Inspection Many larger food companies are requiring their suppliers to meet water activity specifications on the ingredients. Rather than just buying raisins from a supplier, a food producer can purchase raisins at any aw level depending on the application. The aw of the raisin will be much lower if the application is for a breakfast cereal versus a higher aw raisin that is to be baked into a muffin. Decagon Devices, Inc.
- 50. Review: Why use aw? Ø Microbial Growth Ø Hurdle Technology Ø Chemical/Biochemical Stability Ø Physical Properties Ø Moisture Migration Control Ø Compliance with Government Agencies Ø Shelf Life Testing Ø Product Formulation Ø Process Control Ø Quality Control Ø Inspection of Incoming Ingredients Decagon Devices, Inc.
- 51. EminTech (http://emintech.com/) Independent Water Activity Study AquaLab +Very good reproducibility even after 11 days + reproducible results + stable calibration + quick measurements + nice design
- 52. Primary Method VS Secondary Method • Aqualab uses Dewpoint Method which is a Primary Method. • All other water activity meters on the Market use secondary method.
- 53. Testimonials The Vapor Sorption Analyzer has become an invaluable instrument to our R&D lab. The Dynamic Dewpoint Isotherm (DDI) method allows us to generate an isotherm in 12-24 hours, at a wide range of temperatures. The Dynamic Vapor Sorption (DVS) method provides a fully automated process of obtaining kinetics of moisture uptake in our products. The “Test Wizard” function in the software allows for quick and easy test set-up, and exporting the results is done with one click of a button. The Vapor Sorption Analyzer has provided us with very reliable and repeatable results that have been instrumental to the development of our products. Thanks! Kara Grant Process Development Intern GMCR Specialty Coffee Business Unit
- 54. Thank You! Decagon Devices, Inc. Brady Weldon International Product Manager www.aqualab.com Decagon Devices, Inc.