Transformation between 2-Threityl-thiazolidine-4-carboxylic Acid and Xylose–Cysteine Amadori Rearrangement Product Regulated by pH Adjustment during High-Temperature Instantaneous Dehydration

Abstract

2-Threityl-thiazolidine-4-carboxylic acid (TTCA) was found to be the predominant product rather than the Amadori rearrangement product (ARP) during the formation of xylose−cysteine-derived (Xyl−Cys-derived) Maillard reaction intermediates (MRIs) through a thermal reaction coupled with vacuum dehydration. To regulate the existence forms of Xyl−Cys-derived MRIs, an effective method carried out by pH adjustment during high-temperature instantaneous dehydration through spray-drying was proposed in this research to promote the conversion from TTCA to ARP. The increased inlet air temperature of spray-drying could properly facilitate the shift of chemical equilibrium between the MRIs and promote the transformation from TTCA to ARP while raising the total yield of TA (TTCA + ARP). The conversion to ARP was increased to 20.83% at 190 °C of hot blast compared to the product without spray-drying (6.03%). The conversion from TTCA to ARP was further facilitated in the pH range of 7.5−9.5. When the pH of the aqueous reactants was adjusted to 9.5, the equilibrium conversion to ARP was improved to 47.23% after spraydrying, which accounted for 59.48% of the TA formation. Accordingly, MRIs with different TTCA/ARP proportions could be selectively obtained by pH adjustment of the stock solution during high-temperature instantaneous dehydration of spray-drying.

Accelerated Dissipation of Free and Immobilized Water Facilitating the Intramolecular Dehydration of N-Xylosamine and Conversion Improvement of the Amadori Rearrangement Product of Aspartic Acid–Xylose Reaction

“…The quality of the product such as the recovery and granularity of the spray-dried product could be effectively improved by adjusting the concentration of solid contents in the stock solution. On the other hand, an appropriate increase in the substrate concentration was beneficial to the occurrence of the Maillard reaction . Therefore, it is very important to choose the most suitable concentration method and substrate concentration.…”

“…On the other hand, an appropriate increase in the substrate concentration was beneficial to the occurrence of the Maillard reaction. 20 Therefore, it is very important to choose the most suitable concentration method and substrate concentration. According to Gerrard, 29 the conversion of ARP was temperature-dependent, and a too high temperature can lead to the degradation of ARP to downstream products.…”

“…However, in industrial production, the Maillard reaction fluid in the vacuum concentrate tank is prone to the problem of uneven heating, causing ARP cracking and making the reaction proceed to the final stages. Therefore, spray drying was employed by Wang et al to achieve an efficient preparation of ARP in the aqueous medium, resulting in the yield of fructosyl proline rising from 3.6 to 69.2% . However, some amino acids, like aspartic acid, have lower reactivity in the Maillard reaction, which probably leads to a lower yield of aspartic acid–xylose ARP.…”

“…Therefore, spray drying was employed by Wang et al 13 to achieve an efficient preparation of ARP in the aqueous medium, resulting in the yield of fructosyl proline rising from 3.6 to 69.2%. 20 However, some amino acids, like aspartic acid, have lower reactivity in the Maillard reaction, 8 which probably leads to a lower yield of aspartic acid−xylose ARP. Thus, a new method to further dry the spray-dried product for the achievement of a higher ARP yield is needed.…”

Key Aspects of Amadori Rearrangement Products as Future Food Additives

“…In the system of cysteine and xylose, the dominant product becomes 2-threityl-thiazolidine-4-carboxylic acid (TTCA) rather than ARP. The application of short-time spray dehydration is alternatively applied and shifted the equilibrium TTCA to ARP, increasing the ARP yield to 59.48% when the inlet temperature is 190 °C and aqueous pH is adjusted to 9.5 [ 26 ].…”