Freeze- or spray-dried gluten hydrolysates. 2. Effect of emulsification process on droplet size and emulsion stability

Two gluten hydrolysates differing only in the drying process were studied: LS2 was freeze-dried and PS2 was spray-dried. The effect of emulsification procedure (turbo-mixer, valve-homogeniser) was determined as a function of the composition of the aqueous phase (hydrolysate dispersions, soluble frac tions). With turbo-mixer, all emulsions presented a monomodal droplet size distribution but emulsions formed with hydrolysate dispersions were unstabl e whereas these formed with soluble fractions were very stable. With hydrol ysate dispersions, the use of a valve-homogeniser decreased droplet size an d improved considerably the resistance to coalescence. Nevertheless, the en hancement of emulsion stability was higher with LS2 dispersions than with P S2 dispersions. In contrast, with soluble fractions, emulsions formed with valve-homogeniser remained highly stable but the droplet distribution becam e polymodal. The higher energy input provided by a valve-homogeniser result ed in the insoluble fraction becoming involved in the emulsion formation. T his led to a narrower droplet size distribution and more stable emulsions. (C) 2001 Elsevier Science Ltd. All rights reserved.