Preliminary study of the impacts of constituents of sugarcane juice on sucrose degradation and pH drop during evaporation

During sugar-manufacturing processes such as evaporation, loss of sucrose can occur due to acid-catalysed hydrolysis to glucose and fructose, a reaction that is exponential with temperature. This reaction is also affected by pH, dry substance (rds) content and residence time, as well as the nonsucrose composition. Sugarcane juice contains many nonsucrose substances extracted from the cane plant during processing, including invert sugars, minerals, organic acids, proteins, amino acids, phenolics, flavonoids and polysaccharides. Representative chemicals reflecting these nonsucrose substances were spiked into synthetic sucrose solutions to determine how specific classes of nonsucrose substances impact sucrose degradation under thermal conditions. Invert sugars, flavonoids and minerals had a catalytic effect on sucrose degradation that was accompanied by a higher juice pH drop. Organic acids minimised sucrose degradation slightly due to a buffering effect. Other juice constituents showed minimal impact. Studies on the catalytic activity of minerals showed that catalytic activity increased in the order of Na+ < K+ < Mg2+ < Ca2+. During thermal processing, juice constituents are involved in complex interactions, so further research is necessary to better elucidate these interactions.