HS-SPME-GC-MS-based profiling of volatile metabolites in Peel and flesh of Cerasus humilis fruit during development and their association with calcium fractions.

Cerasus humilis (Bge.) Sok (C. humilis) is a Rosaceae shrub fruit known for its high calcium content. However, the relationship between its endogenous calcium fractions and aroma compounds remains uncharacterized. In this study, we quantified four calcium fractions and profiled volatile metabolites in the peel and flesh of the cultivar 'Nongda 4' at three key developmental stages (S1-S3), with three independent trees sampled at each stage (n = 3 per stage; nine trees total); peel and flesh were separated from the same composite fruit sample of each tree. Total calcium content in the peel was 2.9-5.2 times higher than that in the flesh. During ripening, the dominant calcium fraction in the peel shifted from pectin-bound to water-soluble, whereas calcium fractions in the flesh remained relatively stable. We detected 1460, 1467, and 1465 volatile metabolites at S1, S2, and S3, respectively, covering 15 chemical classes, with terpenoids and esters as the dominant classes. The main site of volatile accumulation shifted from the peel during S1 and S2 to the flesh at S3. Different calcium fractions showed opposing association patterns with core ester volatiles. At S3, higher levels of pectin-bound calcium in the peel tended to be negatively associated with several esters, whereas water-soluble calcium showed the opposite trend. The dynamics of calcium fractions coincided with shifts in aroma-related pathways. Overall, this study provides a tissue-resolved, developmental view of calcium distribution and volatile profiles in C. humilis, and offers testable hypotheses for future functional studies on calcium-aroma relationships.