Effects of different organic weed management strategies on the physicochemical, sensory, and antioxidant properties of machine-harvested blackberry fruits.

Unlabelled: The effect of 3 different weed management strategies, nonweeding, hand weeding, and weed mat, were examined on physicochemical, sugar profile, and antioxidant properties of 2 cultivars of blackberry (Rubus spp), "Marion" and "Black Diamond" harvested at 3 time intervals during the 2012 season. Sensory analysis on flavor intensity of 6 different descriptors by an experienced panel was also performed on "Black Diamond" berries harvested at the same interval during the 2013 season. While weed management had no effect on pH, titratable acidity, and total soluble solids of either cultivar (P > 0.05), it showed a marked effect on total phenolics (5.65 to 7.80 mg GAE/g FW), total monomeric anthocyanins (1.07 to 2.85 mg/g FW), ORAC (271.51 to 644.97 μMol TE/g FW), FRAP (408.56 to 719.10 μMol Fe(2+) /g FW), sugar profile, and flavor intensity. Hand-weeding resulted in fruit antioxidant content and capacity as much as 30% greater, though the effect was not seen in the late harvest, where the nonweeded samples tended to have higher values. Overall, weed mat samples had the lowest antioxidant content and capacity in all harvests. Sugar profiling exhibited a greater variability based on cultivar and harvest, but overall, weed mat samples had lower sugar levels than fruit from the other 2 methods. Interestingly, the intensity of sensory attributes for "Black Diamond" appear to possibly be inversely related to phenolic and anthocyanin content, with the weed mat management strategy resulting in the highest values for virtually all sensory attributes. This study provided valuable information about the impact of organic production method on the quality of blackberries.

Practical Application: Weed management is one of the largest costs associated with organic agriculture because of limited availability of approved herbicides. While much work has been done to evaluate the effect of different methods on plant growth and yield, few have determined the impact of weed management methods on fruit quality. This study investigated the impact of 3 common weed management strategies on physicochemical, sensory, and antioxidant properties of 2 organically grown blackberry cultivars. Given the widespread belief that organically grown products are of higher quality than conventionally grown ones, the information generated is particularly important for growers and consumers.