The dominating effect of ionic strength on the heat-induced denaturation and aggregation of β-lactoglobulin in simulated milk ultrafiltrate

• Published in: International dairy journal Vol. 19; no. 3; pp. 123 - 128
• Main Authors: O'Kennedy, Brendan T., Mounsey, John S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2009; [Amsterdam]: Elsevier Science; Elsevier
• Subjects: Biological and medical sciences; calcium; denaturation; filtrates; Food industries; food processing; Fundamental and applied biological sciences. Psychology; heat treatment; ionic strength; lactoglobulins; Milk and cheese industries. Ice creams; model food systems; protein aggregates; sodium chloride; ultrafiltration; whey; Aggregation; Milk protein; Heat; Ionic strength; Denaturation; β-Lactoglobulin; Dairy industry; Dairy product; Whey protein; Milk
• ISSN: 0958-6946; 1879-0143
• DOI: 10.1016/j.idairyj.2008.09.004

The denaturation/aggregation behaviour of heated (78
°C, 10
min) β-lactoglobulin (1%, w/w) was examined as a function of heating pH (5.0–7.0), in the presence of different salts. Heating β-lactoglobulin in the presence of calcium (5
m
m) significantly increased the level of aggregated protein at most heating pH values, compared to heating in water or sodium chloride (100
m
m). Heating β-lactoglobulin in the presence of calcium (5
m
m) and phosphate (5
m
m), resulted in similar denaturation levels in the pH range 5.0–5.8 as in the presence of calcium (5
m
m) alone but reduced denaturation in the pH range 6.0–7.0, probably due to the formation of insoluble calcium phosphate. The addition of NaCl (100
m
m) counteracted the aggregation promoting properties of the calcium and calcium/phosphate systems. Heating β-lg in a simulated milk ultrafiltrate solution was similar to heating in NaCl alone. This suggested that Ca
2+ effects alone may not explain the heat-induced denaturation/aggregation behaviour of β-lactoglobulin in milk whey systems.