Compositional Variability of Rowanberry Genotypes and Sugar-Organic Acid Distribution Between Juice and Pomace

This study evaluated the compositional and processing characteristics of 17 rowanberry (Sorbus spp.) genotypes, including sweet cultivars, interspecific hybrids, and a wild rowanberry. Fruit weight, colour parameters, soluble solids content (SSC), and titratable acidity (TA) were determined to assess fruit quality, and the distribution of soluble sugars and organic acids among whole fruit, juice, and pomace fractions was investigated. Significant (p < 0.05) variation was observed among genotypes, with fruit weight ranging from 0.40 g in wild rowanberry to 1.55 g in 'Alaja Krupnaja'. Hierarchical cluster analysis grouped the genotypes into two major clusters according to colour characteristics. Based on the SSC/TA ratio, 'Burka' and 'Oranzevaja' exhibited the most favourable balance between sweetness and acidity. Sorbitol was the predominant soluble carbohydrate and showed pronounced cultivar-dependent variation, ranging from 46.2 mg/g DW in 'Likernaja' to 189.0 mg/g DW in 'Krasnaja'. Malic acid was the dominant organic acid in all fractions, reaching 70.9 mg/g DW in the pomace of 'Krasnaja'. This study provides the first comprehensive comparison of sugar and organic acid partitioning among fruit, juice, and pomace fractions in a diverse set of rowanberry genotypes, revealing cultivar-specific patterns of carbon allocation relevant to fruit quality, processing, and by-product valorisation.