Effect of addition of proteins on the production of amorphous sucrose powder through spray drying

• Published in: Journal of food engineering 2009-09, Vol.94 (2), p.144-153
• Main Authors: Adhikari, B., Howes, T., Bhandari, B.R., Langrish, T.A.G.
• Format: Article
• Language: English
• Subjects: Amorphous sucrose; Biological and medical sciences; blended foods; caseinates; drying quality; drying temperature; electron paramagnetic resonance spectroscopy; ESCA; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Glass transition; glass transition temperature; mixing; model food systems; particle size distribution; powdered sugar; protein isolates; Protein segregation; proteins; Spray drying; Stickiness; sucrose; sugar-protein powders; surface active properties; surface tension; total solids; water activity; water content; whey protein; X-ray diffraction
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2009.01.029

Spray drying trials were carried out to produce amorphous sucrose powder. Firstly, pure sucrose solutions were prepared and spray dried at inlet and outlet temperatures of 160 °C and 70 °C, respectively. No amorphous powder was obtained and only 18% of the feed solids were recovered in a crystalline form, with the remaining solids lost as wall deposits. Secondly, sodium caseinate (Na–C) and hydrolyzed whey protein isolate (WPI) were added in sucrose:protein solid ratios of (99.5:0.5) and (99.0:1.0) and drying trials were conducted maintaining the initial drying conditions. In both these cases, greater than 80% of the feed solids were recovered in an amorphous form. The increase in protein concentration from 0.5% to 1% on dry solid basis did not further improve the recovery. The remarkable increase in recovery from a small addition of protein is attributed to preferential migration of protein molecules to the droplet-air interface, and the subsequent transformation of the thin, protein-rich film into a non-sticky glassy state upon drying. This film overcomes both the particle-to-particle and particle-to-wall stickiness. The measured bulk glass rubber transition temperature ( T g–r) values of the bulk mixtures at various moisture contents were very close to the corresponding mean glass transition temperature ( T g) of the pure sucrose indicating that surface layer T g rather than the bulk T g is responsible for this. Electron spectroscopy for chemical analysis (ESCA) studies revealed that the particle surface was covered by 50–58% (by mass) proteins. The calculated glass transition temperature of the surface layer ( T g,surface layer), based on the surface elemental compositions, showed that the T g,surface layer has increased to the extent that it remained within the safe drying envelope of spray drying.