Heat stability of milk supplemented with calcium chloride

• Published in: Journal of dairy science Vol. 95; no. 4; pp. 1623 - 1631
• Main Authors: On-Nom, N., Grandison, A.S., Lewis, M.J.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.04.2012; Elsevier
• Subjects: Animal productions; Animals; beta-lactoglobulin; Biological and medical sciences; calcium; Calcium - analysis; calcium chloride; Calcium Chloride - analysis; casein; Caseins - analysis; coagulum; Dialysis; Dietary Supplements - analysis; dried skim milk; electrophoresis; Food industries; Food Preservation; Fundamental and applied biological sciences. Psychology; heat stability; heat treatment; Hot Temperature; Hydrogen-Ion Concentration; ionic calcium; lactalbumin; milk; Milk - chemistry; Milk and cheese industries. Ice creams; Milk Proteins - analysis; Powders; sediments; temperature; Terrestrial animal productions; total solids; Vertebrates; whey protein; Whey Proteins; pH; ionic calcium; heat stability; Heat; Stability; Calcium; Quality; Dairy industry; Dairy product; Inorganic element; Calcium chloride; Milk
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2011-4697

Calcium chloride (0–25mM) was added to skim milk powder that was reconstituted to 9% total solids. Heat stability was evaluated between 60 and 120°C for different times by observing whether samples had coagulated, and by measuring the amount of sediment and residual protein in the centrifuged supernatant. Milk samples were also dialyzed during their respective heat treatments to recover the soluble phase at different temperatures to measure pH and ionic calcium. The transition conditions between good and poor heat stability were established for different calcium chloride concentrations and temperatures. As temperature increased, coagulation occurred at lower levels of added calcium chloride. The transition was quite distinct at higher temperatures but less so at lower temperatures; it was initiated by an increase in sediment formation before a firm coagulum was formed. Both pH and ionic calcium decreased in dialysates as temperature increased. No coagulation was observed if Ca2+ was <0.5mM and pH was >6.3 in dialysates taken at their respective coagulation temperatures. Being able to measure pH and ionic calcium at high temperatures will allow better understanding of factors affecting heat stability. Electrophoresis of the supernatants permitted identification of the protein fractions participating in the coagulation process. When coagulation was observed below 80°C, substantial amounts of undenatured β-lactoglobulin and α-lactalbumin were found in the supernatant, as well as some soluble casein fractions. All the major whey protein and casein fractions were found in the sediment.