The effects of different concentration methods on the chemical composition, functional and sensory attributes of molasses produced from grape (Vitis vinifera L.) juice

The effects of concentration by outdoor (OCM) and vacuum (VCM) and traditional (TCM) methods for the production of molasses from fresh grape juice (FGJ) were evaluated concerning volatile compounds, sugars, organic acids, hydroxymethylfurfural (HMF), total phenolic (TPC), total flavonoid (TFC) contents, and antioxidant capacity (TAC), and sensory properties. Compared to FGJ, its molasses had lower TPC, TFC, TAC, and total organic acids and total sugars (except for the OCM) in total soluble solids (TSS). Additionally, the most of (60.7%) volatile compounds in FGJ disappeared with the production of the molasses. Moreover, all investigated features were significantly influenced by the concentration method used. The TCM-concentration method markedly increased the amounts of both HMF (similar to 180- and 50-fold greater than of the OCM and TCM, respectively) and total volatile furans (similar to 20- and 3.6-fold greater than that of OCM and TCM, respectively). Additionally, this method presented the best antioxidant properties in terms of greater TPC, TFC, and TAC, whereas both TPC and TFC in the molasses produced by the OCM-method were not significantly different from those they obtained by the VCM-method. The principal component analysis (PCA) based on the chemical characteristics revealed close similarity between the OCM and VCM, even though the OCM had higher contents for sugars and organic acids. According to the sensory evaluation, there were no significant differences between the scores of flavor and overall acceptability for the TCM and OCM. In conclusion, an adapted the OCM-concentrating method to industrial-type can be proposed to produce high-quality molasses.