The aim of this work was to study the influence of a wide range of incubation temperatures (4 to 40 °C) and sodium caseinate concentrations (2 to 6% (w/w)) on acid-gel properties during and after long ageing times, formed under different acidification rates promoted by gradual hydrolysis of glucono-δ-lactone (GDL) into gluconic acid. The kinetics of acidification and gelation were followed from pH 6.7 to a final pH value around 4.6 by evaluation of the pH and mechanical properties using uniaxial compression measurements (stress and strain at rupture). As a general trend, faster acidification rates led to faster gel network formation, and lower incubation temperatures led to a higher final pH, while increasing caseinate concentration promoted a small increase in the pH value. Stress at rupture of gels induced by fast acidification rates did not exhibit a weaker gel network, showing the contribution of rearrangements of the network gel at final pH to the electrostatic balance, besides the fact that the hydrophobic interactions and hydrogen bonds were important forces involved in microstructure stabilization. Rearrangement of the gel network was mainly observed at pH values close to 4.6 and was more pronounced at longer ageing times of incubation. The stronger gels were obtained at incubation temperatures of 10 °C followed by 25, 4 and 40 °C, which was an indication of the behavior of the gel network microstructure, since at the highest temperature the pores were larger and syneresis more pronounced. The results of this study suggest that the incubation temperature, protein concentration and rearrangement at final pH have a great influence on the balance between the attractive and repulsive forces between protein and water, contributing to development of optimized texture and water-holding capacity of acid-gels of sodium caseinate. © 2008 INRA EDP Sciences.886667681Dairy Products (1996) Official Method of Analysis of AOAC International, 2. , AOAC, 16th edition, vArshad, M., Paulsson, M., Dejmek, P., Rheology of buildup, breakdown and rebodying of acid casein gels (1993) J. Dairy Sci, 76, pp. 3310-3316Braga, A.L.M., Menossi, M., Cunha, R.L., The effect of the glucono-delta-lactone/caseinate ratio on sodium caseinate gelation (2006) Int. Dairy J, 16, pp. 389-398Bringe, N.A., Kinsella, J.E., Calcium-chloride, temperature, preheat treatments and pH affect the rate of acid-induced aggregation of casein, Food Hvdrocoll, 7 (993), pp. 113-121Bryant, C.M., McClements, D.J., Molecular basis of protein functionality with special consideration of cold-set gels derived from heat-denaturated whey (1998) Trends Food Sci. Technol, 9, pp. 143-151Carr, A.J., Munro, P.A., Reversible cold gelation of sodium caseinate solutions with added salt (2004) J. Dairy Res, 71, pp. 126-128Dalgleish, D.G., Law, A.J.R., pH-induced dissociation of bovine casein micelles. I. Analysis of liberated caseins (1988) J. Dairy Res, 55, pp. 529-538de Kruif, C.G., Roefs, S.P.F.M., Skim milk acidification at low temperatures: A model for the stability of casein micelles (1996) Neth. Milk Dairy J, 50, pp. 113-120Ettelaie, R., Computer simulation and modeling of food colloids (2003) Curr. Opinion Colloid Interface Sci, 8, pp. 415-421Farrell, H.M., Pessen, H., Brown, E.M., Kumosinski, T.F., Structural insights into the bovine casein micelle - small-angle X-Ray-scattering studies and correlations with spectroscopy (1990) J. Dairy Sci, 73, pp. 3592-3601Gastaldi, E., Lagaude, A., Marchesseau, S., de la Fuente, B.T., Acid milk gel formation as affected by total solids content (1997) J. Food Sci, 62, pp. 671-678Hearle J.W, Polymers and their properties, in: Hearle J.W, Ed, Fundamentalsof Structure and Mechanics, 1, Ellis Horwood, Chichester, West Sussex, UK, 1982, p. 144Holt, C., Home, D.S., The hairy casein micelle: Evolution of the concept and its implications for dairy technology (1996) Neth. Milk Dairy J, 50, pp. 85-111Home, D.S., Casein interactions: Casting light on the black boxes, the structure in dairy products (1998) Int. Dairy J, 8, pp. 171-177Home D.S., Casein micelles as hard spheres: limitations of the model in acidified gel formation, Colloids Surf. A: Phvsicochem. Eng. Aspects 213 (2003) 255-263Kalab, M., Allanwojtas, P., Phippstodd, B.E., Development of microstructure in set-style nonfat yogurt - A review (1983) Food Microstr, 2, pp. 51-66Laligant, A., Famelart, M.H., Paquet, D., Brulé, G., Fermentation by lactic bacteria at two temperatures of pre-heated reconstituted milk. II - Dynamic approach of the gel construction (2003) Lait, 83, pp. 307-320Lucey, J.A., Tamehana, M., Singh, H., Munro, P.A., A comparison of the formation, rheo-logical properties and microstructure of acid skim milk gels made with a bacterial culture or glucono-delta-lactone (1998) Food Res. Int, 31, pp. 147-155Lucey, J.A., Teo, C.T., Munro, P.A., Singh, H., Rheological properties at small dynamic and large yield deformations of acid gels made from heated milk (1997) J. Dairy Res, 64, pp. 591-600Lucey, J.A., van Vliet, T., Grolle, K., Geurts, T., Walstra, P., Properties of acid casein gels made by acidification with glucono-delta-lactone. 1. Rheological properties (1997) Int. Dairy J, 7, pp. 381-388Lucey, J.A., van Vliet, T., Grolle, K., Geurts, T., Walstra, P., Properties of acid casein gels made by acidification with glucono-delta-lactone. 2. Syneresis, permeability and microstructural properties (1997) Int. Dairy J, 7, pp. 389-397Oakenfull, D., Miyoshi, E., Nishinari, K., Scott, A., Rheological and thermal properties of milk gels formed with kappa-carrageenan. I. Sodium caseinate (1999) Food Hydrocoll, 13, pp. 525-533Pugnaloni, L.A., Matia-Merino, L., Dickinson, E., Microstructure of acid-induced caseinate gels containing sucrose: Quantification from confocal microscopy and image analysis (2005) Colloids Surf. B: Biointerfaces, 42, pp. 211-217Reefs, S.P.F.M., The structure of acid casein gels (1986) A study of gels formed after acidification in the cold, , Ph.D. thesis, Wageningen Agricultural University, The NetherlandsRoefs, S.P.F.M., Walstra, P., Dalgleish, D.G., Home, D.S., Preliminary note on the change in casein micelles caused by acidification (1985) Neth. Milk Dairy J, 39, pp. 119-122Salaün E, Mietton B., Gaucheron E, Buffering capacity of dairy products, Int. Daily J. 15 (2005) 95-109Steffe, J.F., (1996) Rheological Methods in Food Processing Engineering, Freeman Press, East Lansing, Ml, , USASwaisgood, H.E., Proteins (1982) Developments in Dairy Chemistry, pp. 1-59. , Fox P.F, Ed, Applied Science Publisher, London, UKvan Vliet, T., Lucey, J.A., Grolle, K., Walstra, P., Rearrangements in acid-induced casein gels during and after gel formation (1997) Food Colloids: Proteins, Lipids and Polysaccharides, pp. 335-345. , Dickinson E, Bergenstahl B, Eds, Royal Society of Chemistry, Cambridge, UKvan Vliet, T., van Dijk, H.J.M., Zoon, P., Walstra, P., Relation between syneresis and rheological properties of particle gels (1991) Colloid Polym. Sci, 269, pp. 620-627Vétier N., Desobry-Banon S., EleyaM.M.O., Hardy J., Effect of temperature and acidification rate on the fractal dimension of acidified casein aggregates, J. Dairy Sci. 80 (1997) 3161-3166Walstra, P., On the stability of casein micelles (1990) J. Dairy Sci, 73, pp. 1965-1979Zoon, P., van Vliet, T., Walstra, P., Rheological properties of rennet-induced skim milk gels. 2. The effect of temperature (1988) Neth. Milk Dairy J, 42, pp. 249-269