Relatively high acidity is an important breeding objective for fresh juice-specific apple cultivars

Minimally processed fresh apple juice is a popular processed food product as it preserves the fruit's flavor and nutrients. To better understand the genetics of traits related to the quality of freshly squeezed apple juice (FS) in apple cultivars, we phenotyped hybrids derived from five biparental crosses of Malus asiatica 'Zisai Pearl', and M. domestica 'Red Fuji', 'Golden Delicious' and 'Jonathan' for a total of individuals 2575 in the year 2015 and 2023 in the year 2016. We also studied the inheritance of these traits with a quantitative trait loci (QTLs) analysis. Our results indicate that fruit juice yield, total soluble solid content (TSSC), pH value, light transmittance (TRA), and color traits (CIE coordinates, L*, a*, and b*) segregated quantitatively. We measured the average broad sense heritability and coefficient of variance to be 32.1-68.9% and 8.11-132.22%, respectively. Results from an untrained sensory evaluation panel indicated that FS with sour-sweet flavor, golden yellow color, moderate clarity and green apple aroma were most preferred. The overall sensory scores were closely related to TSSC, titratable acids (TA) and L* value. FS acidity (TA or pH) correlated with all physiochemical parameters except for polyphenol contents. We detected thirteen QTLs for juice yield, pH, TRA and b*, while QTLs for pH value co-localized with TRA and b* on linkage group 16 of both 'Zisai Pearl' and 'Red Fuji'. In summary, juice acidity, affecting juice flavor, color, clarity and the overall sensory scores, is an important breeding objective for FS specific apple cultivars.