## 3 Results and Discussion
### Volatile Compounds Formation and Their Precursors
The deoxy-dicarbonyl sugar derivatives underwent further dehydration and cyclization processes, forming a series of oxygen heterocyclic compounds, such as furan compounds and furanones (Figure 5b). Additionally, they could also undergo dehydration, and fragmentation, giving rise to products containing one or more carbonyl groups [49], which could be further involved in the consequent Strecker degradation processes. A possible addition reaction between Heyns products and D-fructose was proposed by [PERSON]. (1993) [48], with further aldol condensation and dehydration, forming the substituted pyrrole. Thus, the 1-(1H-pyrrol-2-yl)-ethanoneone developed from S-210 towards the end could be the derivative of the substituted pyrrole. Figure 5: _Cont._  
PLRS analysis also indicated that all the FAA were positively correlated to the formation of aldehydes, sulfur compounds, acids, oxygen, and nitrogen heterocyclic compounds, while negatively correlated to esters and hydrocarbons (Figure S2b). Total FAA content in the system experienced an overall decreasing trend from 87.69 at the beginning to 62.62 mg/kg.\({}^{\circ}\)Bx towards the end (Table 1). However, each FAA content fluctuated from S-0 to S120, followed by a decreasing trend thereafter (Supplementary Figure S3), the fluctuation could be due to the consumption of FAA in the early stages of the Maillard reaction (a relative mild heating condition), forming Amadori products [50], and the release  
Figure 5: (**a**) Sucrose chemical and thermal inversion process, the possible caramelization reaction pathway of mono sugars, and the initiation of mono sugars Maillard reaction pathways, and (**b**) the possible Maillard reaction pathways for the typical volatiles formed in the dehydration process. of amino groups from the furfural-based Schiff base intermediates that occurred at a higher temperature among the dehydration process [51]. Meanwhile, the decreasing trend from S150 to S-240 could be due to the consumption of amino acids in the Strecker degradation process, forming Strecker aldehydes and amino containing carbonyl compounds. As shown in Figure 4 Stage 3, Strecker aldehydes developed in the process were significantly differed from that in fresh cane juice, most of them are short chain aldehydes. The possible reaction pathway of the typical Strecker aldehydes formed in the dehydration process are shown in Figure 5b. The amino containing carbonyl products further react with the amino groups, followed by condensation or polymerization process, forming pyrazines and melanoidins that contribute to the flavor and browning appearance of the products, respectively [52]. The possible reaction pathway of the typical nitrogen heterocyclic compound pyrazines identified from S-210 to S-240 are shown in Figure 5b. In addition to aldehydes, the heterocyclic compounds containing the heteratoms' oxygen and nitrogen, sulfur compounds, including dimethyl sulfide and dimethyl sulfoxide, were also increased significantly in the post stages (S-180 to S-240). The concentration of the furfural, dimethyl sulfide and dimethyl sulfoxide are particularly high, and it would be beneficial to reduce or eliminate them from NCS without affecting the aroma characteristic but still maintain health and nutritional promoting properties. The boiling point of some of these volatile compounds, e.g., dimethyl sulfide (37 \({}^{\circ}\)C), is low and so the composition of the aroma compounds of NCS will vary during storage, thereby impacting on the sugar odor. In this regard, the dehydrating process should be re-designed and may involve changing the reaction temperature and time profiles.