Brown sugar aroma: Key aroma-active compounds, formation mechanisms and influencing factors during processing

Aroma is an important quality index for brown sugar. To date, a complete review of the aromatic consideration of brown sugar is lacking in the literature. In this review, the key aroma-active compounds of brown sugar, their formation mechanisms, processing and key influencing factors were elaborated. Hundreds of volatile compounds and key aroma-active compounds have been reported in brown sugar, among them, oxygen heterocyclic compounds and N-containing compounds are the key aroma-active compounds, especially furfural, furanones and pyrazines, which contribute to the 'sweet' and 'roasted' notes. The processing is the main means of forming the aroma, and the evaporation and concentration play a key role in influencing the formation mechanism (caramelization, Maillard reaction and thermal degradation). Sugar and amino acids are the precursors of oxygen heterocyclic compounds and N-containing compounds; temperatures, pH and moisture control the speed and direction of the reactions by influencing their fracture, cyclization and dehydration; phenols and metal cations can combine with reaction intermediates, thus affecting the overall flavor of brown sugar. This paper could assist researchers and manufacturers by giving a comprehensive review of brown sugar aroma, with a view to continuously producing popular brown sugar.