New tools for rapid fruit quality analysis in blueberry

Blueberry fruit quality, defined here as size, firmness, color, and chemical composition, attracts consumer purchases while a positive sensory experience encourages repeat purchases. While these attributes are important in breeding programs, phenotyping these traits using traditional methods is expensive and time consuming. A system was developed to screen about 3000 samples each from Florida and Oregon breeding programs for fruit puree soluble solids content (SSC), pH and titratable acidity using ball mill homogenization and refractometers. Near infrared spectrometry of freeze-dried powders was done to determine individual and total soluble sugars. The SSC, pH, and titratable acidity could be determined on about 150 puree samples day^-1, with 200 samples scanned day^-1 for NIR. Titratable acidity and pH were similar for Oregon and Florida samples, ranging in value from 0.10 to 1.53% citric acid equivalents and pH of 2.70 to 5.25. Total SSC was higher in Oregon samples (7.2 to 23.4%) compared to Florida samples (6.3 to 18.3%). Total sugar ranges were 455-765 mg g^-1 dwt. Sucrose content of fully ripe blueberries ranged from undetectable to 5% of total sugars, while fructose and glucose comprised 45-53 and 46-53% of total soluble sugars, respectively. The coefficient of determination (R²) of the NIR prediction models of sugars was 0.86 to 0.90 for fructose and glucose, respectively.