Acid gelation of raw and reconstituted spray-dried dromedary milk: A dynamic approach of gel structuring

Abstract

Dynamic oscillatory rheology and scanning electron microscopy (SEM) were used to further understand the formation of acid milk gels obtained from raw and reconstituted spray-dried dromedary milk. The influence of acidification temperature, concentration of acidifier (glucono-δ-lactone; GDL) and milk fat content on the rheological parameters of milk gelation were firstly investigated. Our results confirmed the poor ability of dromedary milk to be processed into acidic gels. Under optimised conditions (45 °C, 2.25% GDL), the gel point of dromedary milk occurred at a lower pH (4.46) than that of bovine milk (5.06). The resulting gel obtained after 3 h acidification had a storage modulus (G′) 35 times lower than that obtained from bovine milk. SEM observations of dromedary and bovine milk during acidification highlighted many important differences in the implementation of the microstructure of acid gels. These fundamental differences are discussed based on the literature knowledge of cows' milk acid gelation.