Solubilized micellar calcium induced low methoxyl-pectin aggregation during milk acidification

Area of Science:

• Food Science
• Colloid and Surface Chemistry
• Biopolymer Interactions

Background:

• Low methoxyl (LM) pectin interactions with milk components are crucial for texture development.
• Understanding the role of solubilized micellar calcium is essential for controlling gel properties.

Purpose of the Study:

• To investigate the effect of solubilized micellar calcium on the viscoelastic properties of LM-pectin-milk mixes.
• To determine how temperature and pH during milk ultrafiltration influence permeate composition and subsequent gelation.

Main Methods:

• Ultrafiltration of skim milk at different pH values (6.7 to 5) and temperatures (7°C and 40°C).
• Combination of milk permeates with LM-pectin and measurement of viscoelastic properties (storage modulus, G').
• Correlation analysis between G' and free calcium concentration.

Main Results:

• Milk permeates exhibited gel-like behavior (G' > 1) with LM-pectin, influenced by pH and temperature during ultrafiltration.
• Gel onset pH was higher for permeates from milk filtered at 7°C compared to 40°C.
• Storage modulus (G') strongly correlated with free calcium concentration (r > 0.95) and showed a two-step increase during acidification.

Conclusions:

• LM-pectin-casein micelle interaction in milk is a two-step process.
• The first step involves calcium-dependent pectin-pectin interactions as pH approaches 5.0-4.9.
• The second step involves pectin-casein micelle interactions in the pH range of 5.0-4.9 to 4.0.