Investigation on the effect of the heating surface temperature of 1st evaporator on sucrose loss and the degradation of sugarcane juice constituents

• Published in: Journal of food engineering Vol. 329; p. 111074
• Main Authors: Marasinghege, Chalani, Broadfoot, Ross, Bottle, Steven, Bartley, John, Doherty, William O.S., Rackemann, Darryn W.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2022
• Subjects: Evaporation; Juice degradation; Sucrose hydrolysis; Sugarcane; Superheat; Thermal stability; ΔT; LP; HTC; Evaporation; Juice degradation; Sugarcane; ESJ; Thermal stability; Sucrose hydrolysis; Superheat
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2022.111074

To enable more energy efficient sugar production from sugarcane, higher process temperatures in the 1st evaporator is typically utilized, as this allows higher temperature bleed vapours to be used rather than process steam for other heating duties in the factory. This invariably increases juice degradation and the temperature difference (ΔT) between the heated surface and juice can be even higher where process steam used for heating is superheated. This study investigated the effect of high surface temperatures (139–168 °C) and residence times (0–60 min) on both factory and synthetic juice degradation using a specially designed laboratory evaporator rig. The results show that ΔT is inversely proportional to the heat transfer coefficient. At up to 148 °C and short residence time, there were minor differences in the juice degradation profile. However, at higher temperatures there were significant sucrose loss (≤2.5%), amino acid degradation, lignin (associated with fibre in juice) depolymerization to hydroxycinnamic acids, isomerization of trans-to cis-aconitic acid, and the formation of alcohols. Strategies to minimize juice degradation in evaporators are highlighted. [Display omitted] •Rate of sucrose degradation in sugarcane juice increased with Heating Surface Temperatures (HSTs) (<2.5% at 168 °C).•The rate of degradation of sugarcane juice constituents increased with increasing HSTs.•Sugarcane juice degradation caused increased colour and higher pH drop in the juice.•Higher temperature differentials in evaporators cause reduced heat transfer coefficients.•Sugarcane juice contains catalytic impurities (i.e., minerals) that significantly increase sucrose degradation.