Investigating the influence of insoluble pulp particles on flavor retention and characterization of freshly squeezed and pasteurized mandarin juice.

The presence of insoluble pulp particles influences flavor release and aroma characteristics in citrus juice. This study aimed to investigate the distribution of volatiles in both the liquid and insoluble pulp particle phases of freshly squeezed and heated mandarin juice. Two methods fiber-solid phase microextraction (SPME) and thin film (TF)-SPME, were employed to extract volatiles, which were then analyzed via gas chromatography-mass spectrometry (GC-MS) and a thermal desorption unit-cold injection system 4-multidimensional GC-MS/olfactometry (TDU-CIS4-MDGC-MS/O) with time-intensity. A total of 95 volatiles, including 31 odorants, were identified. Notably, methional was the only volatile sulfur compound detected in different sizes of insoluble pulp particles. More volatile varieties were found in the liquid phase (48-65) than in the insoluble pulp particles (37-45), and larger insoluble pulp particles retained more volatiles. The volatile content of heated insoluble pulp particles was 1.43-20.63 times greater than that of the corresponding fresh pulp particles, mainly due to hydrocarbon retention. Pasteurization enhanced aroma compound retention in insoluble pulp particles, especially hydrocarbons (α-terpinene and terpinolene) and ketones (geranylacetone). With increasing centrifugation intensity, the aroma intensity of off-flavor dimethyl sulfide and methional increased in freshly squeezed mandarin serum, that of carbon disulfide increased, that of dimethyl sulfide decreased in heated mandarin serum, and that of methional decreased in insoluble pulp particles. In conclusion, insoluble pulp particles significantly impact the flavor of mandarin juice. Six and four potential markers were identified to distinguish flavor differences between freshly squeezed and heat-sterilized liquid phase or insoluble particle samples, respectively.