Effect of the ripening stage on the pulsed vacuum drying behavior of goji berry (Lycium barbarum L.): Ultrastructure, drying characteristics, and browning mechanism.

[Display omitted] • Effect of ripening on pulsed vacuum drying behavior of goji berry was explored. • Ripening stage changes goji's phytochemicals, ultrastructure and moisture status. • Ripening stage influences goji drying characteristics and physicochemical quality. • Lower maturity samples hold shorter drying time, while suffer more severe browning. • PVD promoted rupture and transformation of pectin and by thus enhanced browning. In current work, the effect of ripening stages (I, II, and III) on pulsed vacuum drying (PVD) behavior of goji berry was explored. The shortest drying time of goji berry was observed at stage I (6.99 h) which was 13.95 %, and 28.85 % shorter than those at stages II, and III, respectively. This phenomenon was closely associated with the ripening stage, as contributed by the initial physiochemical differences, ultrastructure alterations, and moisture distribution. In addition, lower maturity suffered more severe browning, primarily due to the enzymatic and non-enzymatic reactions of phenolics, followed by pigment degradation and the Maillard reaction. Additionally, the PVD process promoted the rupture and transformation of the pectin fractions, also causing browning either directly or indirectly through participation in other chemical reactions. These findings suggest that the appropriate ripening stage of goji berry should be considered as having a significant impact on drying behaviors and quality attributes. [ABSTRACT FROM AUTHOR]