Evaluation of physicochemical properties in three raspberries (Rubus idaeus) at five ripening stages in northern China

Abstract

To evaluate the physicochemical properties of raspberries (Rubus idaeus L.) at five ripening stages in Shanxi, northern China (non-traditional area of cultivation), 25 physicochemical indexes including 5 anthocyanins and 10 phenolic compounds by HPLC-MS, fruit weight, moisture content, soluble solids content, sugar-acid ratio (SAR), of three commercial cultivars, cv. Reveille, Tulameen and Heritage, were investigated. The fruit qualities of the three cultivars were close to those of fruit produced in the traditional cultivation areas, especially cv. Tulameen at the overripe stage (Stage 5), which had the largest fruit weight of 4.20 g, and the highest SAR of 4.01 and total anthocyanin content of 103 mg 100 g−1 fresh weight. By intercropping the annual-fruiting ‘Heritage’ and the biennial-fruiting ‘Reveille’ and ‘Tulameen’, the raspberry season in Shanxi, China was extended without a break from mid-June to early October. The unripen raspberries (Stages 1 and 2) with high levels of non-anthoycanin phenols, especially ellagictannin were suitable as a plant-derived polyphenol materials. The ripe raspberries (Stages 3 and 4) with a high anthocyanin level and SAR, were suitable for fresh use and processing. The overripe raspberries (Stage 5) which quickly rotted, with the highest anthocyanin level, moisture content and SAR, were suitable as raw materials for anthocyanin extraction. Cyanidin-3-sophoroside, cyanidin-3-glucoside, and cyanidin-3-rutinoside were the main anthocyanins in cv. Heritage, Tulameen, and Reveille, respectively. Thus, commercial raspberries can be utilized on the basis of their properties and active compounds at different ripening stages, and we provide basic data for their production in Shanxi, northern China.