Functional Properties of Proteins 3 major categories  Hydration properties  Protein to water interactions  Dispersibility, solubility, adhesion,  Water holding capacity, viscosity  Structure formation  Protein to protein interactions  Gel formation, precipitation,  Aggregation  Surface properties  Protein to interface interactions  Foaming, emulsification

Effects of Food Processing

Coconut Water-Milk  Milk protein concentrate (90% protein)  Coconut water concentrate (rich in Na, K, Mg, Ca)  Phosphate buffers to pH 7.0  Gum acacia  Locust bean gum  Flavors, minor ingredients

Coconut Water-Milk  Milk protein concentrate (90% protein)  Processed by ultra-filtration  Passed through a membrane to remove water  Washed over and over to remove:  Some whey proteins  Minerals  Lactose  Water

Coconut Water-Milk  The Process:  Buffers added to 35°C water (pH 11)  MPC added, mixed for 30 min with shear  Gums added  Coconut water added  Homogenized  Aseptically processed (140°C for 15 sec)  Homogenized again  Packaged cold

Coconut Water-Milk  The Issue:  Product has 20 gram of protein per 325 mL serving  Very thick, rich, and creamy  After 6 months on-shelf, it begins to fade.  Mild clumping of proteins  Sediment formation  Larger protein clumps form  Looks like curdled milk  Flavor is fine, no detectable microorganisms

Coconut Water-Milk  Initial diagnosis:  Protein oxidation?  Too high of a mineral content  Vitamin and mineral supplement was removed  Whey proteins were denaturing, loosing water  Slow and steady drop in pH was observed  pH 7.0 to pH 6.2 over 6 months  Need to re-buffer the system

Coconut Water-Milk  First attempts:  Add antioxidants (ascorbic, sulfite, polyphenolics)  Aded oxidizers (cross-link proteins)  Add more/stronger/different buffers  Adding more gum to stabilize the water  Slow down the shear rate  Reduce foaming to prevent protein denaturation  Adding oils to help stabilize protein hydration

Coconut Water-Milk  Nothing worked.  In lab trails, the product was form precipitates in 2-3 days at 37°C, compared to 6 months in commercial product.  Almost impossible to simulate the industrial process of homogenization and UHT processing and re-homogenization  pH drops from 7.0 to 6.0 in 24-hrs  Drops to <5.0 in 48 hrs

Coconut Water-Milk  So why a decrease in pH?  A natural ion exchange is taking place  Milk caseins are mostly negatively charged  Phosphates are negatively charged  CWC is mostly cationic, and slighly acidic  Where does the H+ come from?  Most likely….from the casein and phosphates  Exchanging ions with cationic minerals

Coconut Water-Milk

 So here is one of the craziest reactions I have ever seen.  Adding an ALKALI and a resultant LOWERING of the pH  Add CWC to alkaline phosphate buffer (with or without MPC) to hit pH 7.0.  Allow it to hold at 37°C, and the pH slowly drops with time (ion exchange)  Add MORE alkaline phosphate to raise the pH back to pH 7  Over minutes to hours, the pH will lover quickly to pH <6.  You can bounce it like a yo-yo….pH high, pH low, pH high, pH low

Coconut Water-Milk  What did work:  Changing the order of ingredient addition  Blending the phosphates (negatively charged, alkaline phosphates) with the CWC causes an immediate buffering with the ions present  So this SLOWS down the decrease in pH  But does not completely stop the precipitation  pH eventually drops, and proteins fall out

Coconut Water-Milk  What were the eventual solutions?  #1. Change the order of ingredients, to allow chelation of CWC minerals with phosphates  #2. Stop the ion-exchange by physical blocking of the reaction with ionic gums

Coconut Water-Milk  At it also turns out, gum hydration temperatures were too low.  35°C is insufficient to hydrate gum acacia, it needs temps closer to 70°C  Gum acacia is an ionic gum, so it is participating in the ion exchange reactions.  With the gum poorly hydrated, it was binding to water OUTSIDE the milk protein.  Hardest problems often have simplest solutions  Increased the processing temperature, problem gone!