Concentration-related microwave heating processes: electromagnetic interference of Maillard reaction substrates (glucose and lysine)

Abstract

a Glucose and lysine are important substrates involved in the Maillard reaction. The lack of studies on their electromagnetic properties has made it impossible to understand the influence of electromagnetic properties on the microwave heating process, and has hindered the application of the Maillard reaction in the microwave field. In this study, the electromagnetic properties of glucose, lysine solution and their 1 : 1 mixture were determined at frequencies of 1.7-2.6 GHz. The results show that the dielectric loss factors gradually increased. Reflection loss gradually decreased with concentration in the order of glucose > mixture > lysine. The heating rates gradually increased at low concentrations (#5%) and slowly changed at high concentrations ($10%). These results indicate that the effect of electromagnetic properties on the heating rate is related to concentration. The heating rates depended on the dielectric properties at low concentrations (#5%), whereas microwave-absorption properties dominated at high concentrations ($10%).

Investigations on the Effects of Salts and Carbohydrates on L-Lysine in Aqueous System at T=293.15K

“…The strong electrolytes (NaCl and KCl) dissociate almost completely into ions in solution and therefore their solutions have high conductance. The conductance of the samples was in the order of L-lysine + NaCl > L-lysine + KCl > L-lysine > L-lysine + sucrose > L-lysine + glucose 17 . The conductance of solution containing NaCl was highest in comparison to all because NaCl is a strong electrolyte and dissociates completely in an aqueous solution.…”

“…On the other hand, the conductance of the aqueous solutions of L-lysine with glucose was smaller than those obtained for L-lysine itself. This is because of the non-electrolytic nature of glucose and also the presence of Maillard reaction where free amino groups of L-lysine react with reducing sugar (glucose) resulting in less number of ions present in solution and hence decrease in conductance 17 . The conductance of sucrose was slightly smaller than L-lysine but higher than those obtained for L-lysine + glucose solution because sucrose is a non-reducing sugar and does not participate in the Maillard reaction.…”

Glucose Level Sensing Using Single Asymmetric Split Ring Resonator

“…Moreover, the time required to measure each sample was less than 3 s, i.e., the time when the radio frequency signal was applied onto the sample. Given that the input power was −20 dBm and based on the earlier observation of an insignificant change in temperature due to microwave-absorption properties when heating glucose solutions at different concentrations, we estimated that the increase in the temperature of the sample was negligible [ 59 ]. The sensor was designed to resonate initially at around 7 GHz without glucose solutions.…”