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Abbreviations:
MPC
Milk Protein Concentrate
SMP
Skim Milk Powder
WP
Whey Powder
WPC
Whey Protein concentrate
WPI
Whey Protein Isolate
MC
Micellar Casein
NaCn
Sodium Caseinates
CaCn
Calcium Caseinate
Yogurt is a very popular fermented dairy product widely consumed all over the world (Lucey & Singh, 1998; Verman & Sutherland, 2004; Peng et al. 2009). Three major types are found: drinking, set and stirred yogurt. The typical yogurt manufacturing process changes milk properties in an irreversible way and consists of different processing steps (Fig. 1). First, the milk base fat content is standardised to the desired level by mixing cream and skim milk powder (Sodini & Béal, 2003; Lee & Lucey, 2010). Afterward, the non-fat total solid content is traditionally increased to achieve a protein concentration between 40-50 g/kg (Sodini et al. 2005). Fortification of the milk base is one of the most important steps that enhances functional and nutritional properties and prevents textural defects such as poor gel firmness and syneresis as assessed by sensory evaluations and instrumental measurements (Dave & Shah, 1998; Schkoda et al. 2001; Sodini & Béal, 2003; Séverin & Wenshui, 2005; Marafon et al. 2011). Dry matter fortification can be achieved by either concentration process (evaporation under vacuum) followed by membrane processing (ultrafiltration or reverses osmosis) or by the addition of dairy ingredients including skim milk powder (SMP), whey proteins, caseins and caseinates (Tamime & Robinson, 2000; Sodini & Béal, 2003; Damin et al. 2009; Peng et al. 2009). The fortified milk is then homogenised at 10-20 and 5 MPa at first and second stage respectively with a temperature ranging between 55 and 65 °C (Lee & Lucey, 2010). This processing step generates fat globules with new surface layer formed by the caseins and whey proteins thus increasing the number of possible structure-binding components in yogurt products (Lee & Lucey, 2010). The milk base is subsequently submitted to a drastic heat treatment. In fact, it is usually heated at 85 °C for 30 min, at 90-95 °C for 5-10 min or at 115 °C for 3 s (Sodini & Béal, 2003). Heat treatment causes whey protein denaturation and complex formation (whey protein-whey protein or whey protein-casein micelles) through disulphide bonding, which initiates gelation (Ozer...