Powdered Milk Replacer Reconstitution - Solubility Test Methodology
Objective of the solubility test
The objective of the solubility test conducted by WildAgain was to measure the solubility of the various powdered milk replacers in the final stage of the reconstitution process (dissolution). The methodology for this test followed a slightly modified IDF-Standard 129A insolubility index test (International Dairy Federation). This procedure was performed to assess the insolubility of the reconstituted powders as a reasonable estimation for dissolution efficiency.
The testing procedure involved the following steps for each powder sampled:
1.) Individually weigh a sufficient number of 15ml conical centrifuge tubes (Celltreat®, 15 ml, .5 ml graduation with conical bottom, flat surface (HDPE) leak-proof seal caps) and uniquely identify each with a permanent marker. Record individual weight for each (tube and cap).
2.) Combine 1.3 grams of dry powder with 10ml of 110°F water in a tube and replace tube cap. Shake vigorously for 1 minute to mix.
3.) Repeat for 3 other powders to test.
4.) Let reconstituted milk sit for 10 minutes.
5.) Shake each tube again briefly.
6.) Place the 4 tubes in low-speed centrifugation (4,000rpm, 1,790g RCF) for 5 minutes using a 800-1 bench-top centrifuge to sediment the solids.
7.) For each tube, remove supernatant (liquid) being careful not to disturb the solid pellet at the bottom of the tube.
8.) Re-suspend the pellet in 10ml water, recap and repeat steps 4. and 5. above.
9.) Place uncapped tubes in forced air dehydrator at 135°F until all moisture has evaporated and the tube (plus pellet) attain a constant weight.
10.) Recap each tubes original cap and weigh and record weight for each capped tube containing a pellet. Subtract the initially weight for each tube and cap to arrive at weight for each pellet.
11.) Divide the divide the pellet weight by 1.3 grams to arrive at the percent of powder weight that was insoluble.
References (not intended as an exhaustive list)
Anema, S. G., D. N. Pinder, R. J. Hunter, and Y. Hemar. Effects of storage temperature on the solubility of milk protein concentrate (MPC85). Food Hydrocolloids (2006) 20:386-393.
Baldwin, Alan J., Fonterra Research Centre, Palmerston, NZ. Insolubility of milk powder products- a minireview. Dairy Science Technology (2010) 90:169-179.
Boiarkina, I., N. Depree, W. Yu, D. I. Wilson, and B. R. Young. Rapid particle size measurements used as a proxy to control instant whole milk powder dispersibility. Dairy Science and Technology (2017) 96:777-786.
Forny, Laurent and Stefan Palzer (Food Science and Technology Department, Nestlé Research Centre, Vers-Chez-Les-Blanc, CH-1000 Lausanne, Switzerland). Wetting, disintegration and dissolution of agglomerated water soluble powders. Conference Paper · June 2009
Ilari, Jean-Luc and Laila Mekkaoui. Physical properties of constitutive size classes of spray-dried skim milk powder and their mixtures. Le Lait, INRA Editions, 2005, 85 (4-5), pp.279-294. hal-00895603
International Diary Federation. In determination of insolubility index, Standard 129A. Brussels, IDF (1988)
Pugliese, Alessandro, Giovanni Cabassi, Emma Chiavaro, Maria Paciulli, Eleonora Carini, and Germano Mucchetti. Physical characterization of whole and skim dried milk powders. Journal of Food Science Technology (2017) 54(11):3433-3442.
Sharma, Anup, Atanu H. Jana, and Rupesh Shrikant Chavan. Functionality of milk powders and milk-based powders for end-use applications - a review. Comprehensive Reviews in Food Science and Food Safety (2012) 11:518-528.