Sugar and nonvolatile acid composition of blackberries

Sugar and nonvolatile acid analyses were conducted on 52 samples of blackberries (Rubus spp), the objective being to develop a compositional database for evaluating authenticity and quality. Brix ranged from 6.88 to 16.83, with a mean of 10.82. Titratable acidity ranged from 0.52 to 2.24 g citric acid/100 mL, with a mean of 1.35. Sucrose levels (range, 0-12.9%; mean, 4.6%) were highly variable. The overall glucose:fructose ratio ranged from 0.81 to 1.17, with a mean of 1.01. Malic, isocitric, lactoisocitric, citric, shikimic, and fumaric acids were identified, with succinic acid being present in some samples. Malic acid ranged from 5.2 to 35.3% of total acids (87.5-603 mg/100 g), with a mean of 16.4% (280 mg/100 g). Isocitric acid ranged from 4.7 to 71.6%, with a mean of 34.7% (599 mg/100 g), and lactoisocitric acid ranged from 3.4 to 32.6% with a mean of 17.3% (293 mg/100 g). Citric acid ranged from 1.3 to 80.2%, with a mean of 31.6 (572 mg/100 g). Shikimic, fumaric, and succinic were present in trace quantities. Two patterns of nonvolatile acid compositions were evident. Ten commercial blackberry juice samples were analyzed, and it was possible to determine whether they were Marion, Evergreen, or a mixture of the two from their acid profiles.