Submitted to: Critical Reviews in Food Science and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2014
Publication Date: 6/11/2015
Citation: Uchimiya, S. 2017. Roles of reversible and irreversible aggregation in sugar processing. Critical Reviews in Food Science and Nutrition. 57(6):1206-1214.
Interpretive Summary: Sugar solutions are the important starting materials to produce first-generation biofuels (e.g., bioethanol) as well as food products (e.g., soda). Impurities in the sugar solution are small particles that attach to one another to form larger particles. The formation of large particles depends on the solution chemistry and temperature, and can have expensive consequences. This article will address fundamental understandings in particle-particle interactions to help end-users foresee behaviors of impurities during industrial processing.
Technical Abstract: Colloids (1-1000 nm particles) in sugar cane/beet juice originate from non-sucrose impurities (polyphenolic colorants, residual soil, polysaccharides) of the plant materials; additional colloids form during the high temperature processing. Colloids are reactive towards aggregation, sorption, desorption, and redox/hydrolysis/thermal transformation reactions. Both DLVO (van der Waals and electrostatic) and non-DLVO (involving hydrophilic colloids) interactions control the stability of colloids in juice. Heteroaggregation causes a range of feedstock and end-product problems including turbidity, viscosity, color, gelling, crystallization, starch ghost, and heat transfer problems. Even after intensive clarification and refining, trace colloidal impurities on white (refined) sugar remain to cause a problem known as acid beverage floc. Acid beverage floc is an example of DLVO-type aggregation of oppositely charged particles at decreased pH. Examples of irreversible aggregates include starch ghost and recalcitrant organomineral composites formed at elevated temperature that resist heat transfer. Fundamental knowledge in aggregation kinetics is necessary to predict the occurrence of undesirable aggregates as pH, ionic strength, temperature, and sucrose concentration changes during the processing of sugar cane/beet juice.