Microstructure and image analysis of mayonnaises

The microstructure of full-fat mayonnaise was characterised at different st ructural levels by using confocal laser scanning microscopy, CLSM, and tran smission electron microscopy on freeze-etched samples. The size of droplets varied, and in 80% mayonnaise many very small droplets were found between larger droplets. The colloidal structural parameters were quantified on CLS M images. A stereological approach was used to estimate the droplet size, t he interfacial surface area between the fat phase and water phase, and the size of the egg yolk aggregates. The mayonnaise samples were produced by a cold process line in a pilot plant equipment. A two-level fully factorial e xperimental design was used, with the processing parameters, (speed of the emulsification cylinder, the speed of the visco-rotor and the out-temperatu re) as design variables. The results showed that the speed of the emulsification cylinder had a main effect on the size of the droplets. No other effects were found when the s peed of the emulsification cylinder was high. When the speed was slow, howe ver, an interaction effect was found on the size of the droplets. The distr ibution of egg yolk was affected by the processing conditions and by the qu ality of the egg yolk. The storage modulus G' had higher values when the ma yonnaise was formed of smaller droplets at a high emulsification cylinder s peed. Lower values of G' were found when the mayonnaise was formed of large r droplets produced by a slower emulsification cylinder speed. (C) 1999 Els evier Science Ltd. All rights reserved.