Quality Assessment of Prune Jam with Different Concentration Methods Based on Physicochemical Properties, GC-IMS, and...

This study systematically investigated the impacts of four concentration methods-vacuum freezing concentration (VFC), microwave vacuum concentration (MVC), atmospheric thermal concentration (ATC), and vacuum thermal concentration (VTC)-on the quality and volatile compounds of prune jam. Advanced analytical techniques, including electronic tongue, electronic nose, gas chromatography-ion mobility spectrometry (GC-IMS), and multivariate statistical methods (principal component analysis, partial least squares discriminant analysis), were employed to evaluate physicochemical properties and flavor profiles. Results showed that non-thermal methods (particularly VFC) significantly outperformed thermal methods (ATC/VTC) in nutrient preservation. For instance, VFC retained 91.4% of ascorbic acid and limited dietary fiber loss to 4.55%, while ATC caused up to 60.1% ascorbic acid degradation and 51.75% dietary fiber loss. In terms of color stability, VFC induced a 1.04-fold increase in browning index (BI) and a 2.54-fold increase in total color difference (ΔE), significantly lower than ATC's 1.6-fold BI increase and 7.26-fold ΔE rise. GC-IMS identified 42 volatile compounds, categorized into aldehydes (17), alcohols (9), esters (7), etc. Multivariate analysis screened 15 key flavor compounds (VIP > 1, p < 0.05), such as ethyl acetate and methanol, revealing that non-thermal methods better preserved the characteristic sweet-sour flavor and reduced off-flavor formation. These findings highlight VFC's superiority in maintaining nutritional and sensory quality, providing scientific guidance for industrial jam production and flavor optimization in fruit processing.