Application of the acid hydrolysis of sucrose as a temperature indicator in continuous thermal processes

Abstract

The hydrolysis of sucrose in an acid medium was used as a temperature indicator to measure holding temperatures in a continuous thermal-processing unit. From a theoretical analysis, target conversion (v) and errors in both acid concentration and conversion measurements were found to aect signi®cantly the accuracy of predicted temperatures, whereas errors in the determination of the¯uid mean residence time did not show a signi®cant eect. For dierent pasteurisation temperatures (70°C < T < 86°C) and¯ow rates (4800< Re< 11,300), the acid concentration in the medium was adjusted so that dierent extents of reaction could be tested, as the reaction rate was found to increase exponentially with [H ]. Nitric acid solutions were circulated through the unit, a sucrose solution was continuously fed to the entrance of the holding tube and sucrose concentration was analysed at the half way part and at the exit of the holding tube. The temperature of the holding section was then estimated from the measured conversion. These results compared well with thermocouple measurements, with deviations of less than 4°C for conversions between 0.4 and 0.7, whereas greater errors were obtained for both low and high conversions.

Analysis of the hydrolysis of inulin using real time 1H NMR spectroscopy

“…1.7 kJ.mol −1 ) was determined for the hydrolysis of sucrose. This activation energy falls within the range of literature values for the hydrolysis of sucrose of between 98 kJ.mol −1 and 119.7 kJ.mol −1 62,63 . and agrees well with the results from Tombari et al 64 (109.2 kJ.mol −1 using calorimetry) and Buchanan et al .…”

Sucrose Is a Promising Feedstock for the Synthesis of the Platform Chemical Hydroxymethylfurfural

“…They investigated the kinetics of the acid-catalyzed conversion of fructose to HMF [23], HMF to levulinic acid [24], and glucose to levulinic acid [25]. However, kinetic parameters which are determined experimentally depend to a great extent on the setup and the procedure of the experiments themselves [26]. Attention must be paid to the following issues for the direct comparison of kinetic data obtained by different studies: (1) which reactor system is applied, (2) modifications to the Arrhenius equation, (3) modifications to reaction order, (4) the parameter range of reaction conditions, (5) anion effects of the acid utilized, and (6) which reaction scheme is applied.…”

Optimal experimental design for estimating the kinetic parameters of processes described by the first-order Arrhenius model under linearly increasing temperature profiles

“…6, as a function of the rate constant. As expected, the design eciency decreases as the heating rate increases, which implies that the experimental conditions applied by Pinheiro-Torres and Oliveira (1999) would inherently lead to a lower precision at the higher acid concentrations tested. As a matter of fact, this may be observed in the results reported by Pinheiro-Torres and Oliveira (1999), as the Fig.…”

“…To clarify the application of these concepts in food research, a case study is provided, using data from literature. Pinheiro-Torres and Oliveira (1999) estimated the kinetic parameters of acid hydrolysis of sucrose in a range of pH, under non-isothermal conditions, assuming that the kinetics followed a ®rst-order Arrhenius model. The experiments were initiated at a temperature of 50°C and the heating rate varied between 1.43°C min À1 and 2.39°C min À1 , depending on the [H ] concentration (some of the experimental conditions are summarised in Table 1).…”