Formation Of Methylglyoxal And Control Of 4-Methylimidazole In Maillard Reaction

Class III and IV caramel color were applied widely as food colorant, which were manufactured by the Maillard reaction(containing oxidation, dehydration, heterocyclic reaction and polymerization) between reducing sugar and ammonium salt. However, the harmful compound 4-methylimidazole(4-Me I) was formed during the manufacture of caramel color. As a result, the technique for caramel color must be improved to receive the high quality of caramel color containing low level 4-Me I in food. In the early research, the efficient method was developed for analysis of 4-Me I in caramel color using high performance cation exchange chromatography with pulsed integrated amperometric electrochemical detector(HPCEC-PAD). In addition, the tautomer of glucose was analyzed using high-performance anion-exchange chromatography(HPAEC) to be coupled with electrospray ionization(ESI) mass spectrometry(MS), which was a powerful tool for the hydrogen/deuterium(H/D) exchange experiment of glucose in Maillard reaction. Moreover, a systemic research was carried out to indicate the effect of the structure of amino group, the value of p H and the intensity of ultrasound on the formation of α-dicarbonyls in Maillard reaction. Meanwhile, the mechanism of dicarbonyls and 4-Me I formation affected by sulfite in caramel color IV was confirmed by the isotope labeling and H/D exchange experiment. The result was helpful for reducing 4-Me I formation by control of the dicarbonyls formation during the manufacture of caramel color.HPCEC-PAD with post-column addition of hydroxide was firstly developed for simultaneous analysis of 4-Me I in cameral color and soft drinks after solid-phase extraction(SPE). A CS12 A cation exchange column was used to separate the targeted analytes with a perfect resolution(2.70). This method demonstrated low limit of quantification(0.05- 10mg/L) and excellent linearity with correlation of determination(R2 > 0.997 for 4-Me I). Low concentrations of 4-Me I were found in five soft drinks, whereas those in caramel color were generally high. Consequently, the proposed method showed high resolution and satisfied sensitive with respect to the prior routine methods in simultaneous analysis of 4-Me I.A novel interface that enables HPAEC- ESI-MS is reported. A sheath liquid consisting of 50 m M NH4 Ac in isopropanol with 0.05% acetic acid, infused at a flow rate of 3 μL/min at the tip of the electrospray probe, requires less ESI source cleaning and promotes efficient ionization of mono- and di-carbohydrates. The results suggest that use of a sheath liquid interface rather than a T-joint allows volatile ammonium salts to replace non-volatile metal salts as modifiers for improving sugar ESI signals. The efficient ionization of mono- and di-carbohydrates in the ESI source is affected by the sheath liquid properties such as buffer concentration and type of organic solvent. Addition of a make-up solution through the sheath liquid interface proved to be an efficient tool for enhancing the intensities of sugars analyzed using HPAEC-ESI-MS.Methylglyoxal(MGO) has been confirmed as a harmful compound in the Maillard reaction. In this experiment, methylglyoxal was detected using derivatization, and tested by a high performance liquid chromatography with a diode array detector(HPLC-DAD). Change of glucose and amino acids during the Maillard reaction were tested using a HPAEC-PAD. Results showed that lysine(containing two amidogens) and glycine(containing one amidogen) leaded to a higher reaction ratio to form methylglyoxal than arginine(containing four amidogens). And higher p H value significantly accelerated the formation ratio of methylglyoxal. Thus, it can be concluded that p H value should be the first important factor to lead to the formation of methylglyoxal. However, amino activity had no significant relativity on the formation of methylglyoxal.The effect of ultrasound cavitation on the formation of dicarbonyl compounds was investigated using D-glucosamine model system(p H 8) after treatment with various intensity levels(ranging from 2.62 to 10.7 W/cm2) and treatment time(ranging from 0 to 240 min) of ultrasound. The derivative dicarbonyl with o-phenylenediamine was identified using HRMS and 1NMR experiments and was monitored by a high performance liquid chromatography with a diode array detector. Change of D-glucosamine was detected using a high performance anion exchange chromatography with an electrochemical detector. Results showed that 3-deoxyglucose(3-DG) was the mainly formed dicarbonyls and the shorter chain dicarbonyls(such as methylglyoxal and glyoxal) were not detected. Low ultrasonic intensity could induce the formation of 3-DG.Sulfite at low levels was found to promote the formation of 4-Me I. Glucose-ammonium(40mmol/L, p H 7.4) model system with different levels of sulfite(i.e. 0, 10, 20, 40,100, 200 and 400 mmol/L) were incubated at 110 °C for 2 h. Α-dicarbonyls were detected after derivatization by HPLC-DAD. 4-Me I in Maillard reaction was tested using a HPCEC-PAD. Results showed that additional sulfite promoted the formation of deoxyosones and increased 4-Me I levels but inhibited osones formation. In addition, the effect of sulfite on brown intensity in the Maillard reaction was depended on the reaction time and sulfite level due to significant increase and inhibition of 4-Me I and advanced products(melanoidins), respectively, after the addition of sulfite. The H/D exchange experiment in Maillard reaction containing sulfite indicated that the promotion of the 1, 2-enolization reaction of glucose by sulfite was the main reason for increasing the level of MGO and 4-Me I in Maillard reaction.The solution of glucosamine or acetylglucosamine instead of glucose-ammonium solution was found to decrease the formation of 4-Me I. Glucose-ammonium, glucosamine or acetylglucosamine(40 mmol/L, p H 7.4) model system with different levels of sulfite(i.e. 0, or 40 mmol/L) were incubated at 110 °C for 2 h. Α-dicarbonyls were detected after derivatization by HPLC-DAD. 4-Me I in Maillard reaction was tested using HPCEC-MS. Results showed that acetylglucosamine model system induced the lowest level of 4-Me I formation. In addition, the promotion of sulfite on 4-Me I and MGO formation in acetylglucosamine model system was slight. The explanation was that the group of acetyl on glucosamine inhibited the 1, 2-enolization reaction of glucosamine as a result of decrease of MGO and 4-Me I formation.