The effect of low molecular weight surfactants and proteins on surface stickiness of sucrose during powder formation through spray drying

• Published in: Journal of food engineering 2009-09, Vol.94 (2), p.135-143
• Main Authors: Adhikari, B., Howes, T., Wood, B.J., Bhandari, B.R.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; caseinates; dietary protein; droplet size; drying quality; food additives; Food engineering; Food industries; food surfaces; Fundamental and applied biological sciences. Psychology; General aspects; high carbohydrate diet; Low molecular weight surfactants; model food systems; molecular weight; nonionic surfactants; powdered foods; pressure; Protein; protein content; protein hydrolysates; protein isolates; Spray drying; Stickiness; sucrose; Sugar-rich foods; surface active properties; surface pressure; surface tension; total solids; viscoelasticity; viscosity; water activity; whey protein; X-ray photoelectron spectroscopy
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2009.01.022

The effect of competitive surface migration of proteins and low molecular weight surfactants (LMS) on the powder recovery in spray drying of highly sticky sugar-rich food has been studied. Sucrose was chosen as a model sugar-rich food because it cannot be easily converted into a pure amorphous powder through spray drying. Sodium caseinate (Na–C) and hydrolyzed whey protein isolate (WPI) were used as model proteins. Polysorbate 80 (Tween-80) and sodium dodecyl sulfate (Na-DS) were used as model non-ionic and ionic LMS. A sucrose solution was spray dried without any additives to establish a base case. Following this, spray drying trials of sucrose–protein solutions were conducted. The sucrose: protein ratio was maintained at 99.5:0.5 and 99.0:1.0. Finally, 0.05% of Tween-80 and Na-DS, on a nominal feed basis, were individually added to the solutions and spray dried. The solid concentration of all of the feed solutions was set at 25% and the inlet and outlet temperatures were maintained at 170 °C and 70 °C, respectively. Powder recovery was determined using a standard procedure and taken as an indicator of the surface stickiness. Coverage of the particle surface by the proteins was determined through elemental surface analysis and a nitrogen balance. It was found that in the absence of LMS, the proteins covered up to 55% of the particle surface and increased the powder recovery to between 84% and 85%. Formation of a glassy protein-rich film acts to reduce the surface stickiness of sucrose droplets. However, when LMS was added to the sucrose–protein solutions, the recovery dropped to zero in the case of Tween-80. In the case of Na-DS the recoveries ranged to 39% and 68%. At these recoveries 83% and 59% of the protein, respectively, was displaced from the surface. This drastic effect of surfactant types on the powder recovery is explained using the Orogenic Displacement model.