Roles of reversible and irreversible aggregation in sugar processing

Abstract

Colloids (1-1000-nm particles) in sugarcane/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 toward aggregation, sorption, desorption, and redox/hydrolysis/thermal transformation reactions. Both Derjaguin-Landau-Verwey-Overbeek (DLVO; van der Waals and electrostatic forces) 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 change during the processing of sugarcane/beet juice.

Acidity rectified aggregation behaviour of colloids in sugarcane juice

“…At higher pH, the reaction of catechol or hydroquinone with OH − and oxygen is enhanced, darkening the colour of sugarcane juice. In addition, owing to their high pKa values, polyphenols are more soluble at higher pH (Uchimiya, 2015). This can explain the decrease in TPC under alkaline conditions.…”

“…Sugarcane juice is a highly heterogeneous system that contains many non-sugar colloids composed of protein, starch, pectin, gum, wax and clay particles. During processing, the non-sugar colloids accumulate and form stable and unstable aggregates, eventually adversely affecting the clarity, viscosity and colour of sugarcane juice as well as the quality of its derived products (Uchimiya, 2015). Previous studies proved that membrane filtration displays superior performance in the removal of nonsugar substances (such as polysaccharides, proteins, and so on) (Li et al, 2017(Li et al, , 2018Shi et al, 2019Shi et al, , 2021.…”

“…During sugarcane juice processing and storage, changes in pH, salinity and temperature alter the stability of the colloid. The formation of non‐covalent and covalent bonds between the colloidal precursors lead to the formation of undesirable aggregates that negatively impact the aesthetic appearance of the juice, even though the aggregates are harmless (Uchimiya, 2015; Meng et al ., 2021). Therefore, there is a need to study and solve the problem of post‐hazy beverages.…”

“…Sugarcane juice contains caffeic acid, gallic acid, ferulic acid and chlorogenic acids. When the pH of sugarcane juice is close to neutral, catechol in sugarcane juice has a lower reduction potential and rapidly undergoes auto‐oxidation with O 2 (Uchimiya, 2015; Rodrigues et al ., 2021). The effects of pH on phenolic acids in plants vary as caffeic acid, chlorogenic acid and gallic acid are unstable at high pH and prone to degradation, which is irreversible.…”

Bifunctional of Fe3O4@chitosan nanocomposite as a clarifying agent and cationic flocculant on different sugar solutions as a comprehensive semi industrial application

“…Natural sugarcane juice is full of vitamins, minerals, amino acids, flavonoids, and sugars (sucrose, glucose, and fructose), as well as phenolic acids (ferulic acids, coumaric acids, caffeic acids, ellagic acids, and gallic acids), and amino acids 1 – 3 . In the most heterogeneous sugarcane juice, there are multiple non-sugar colloids made up of protein, starch, pectin, gum, wax, and particles of clay 4 .…”