Microbial and sensory quality of an Andean blackberry (Rubus glaucus Benth) cultivar

The “moras de Castilla” (Andean blackberries) are the blackberries most commonly cultivated in Ecuador. They are considered as non-climacteric fruit and thus, they are usually harvested at full maturity. They are also very perishable as rapid mold growth occurs during the postharvest period. The aim of this study was to evaluate the effects of harvest maturity and storage temperature on the microbiological and sensory quality of Andean blackberries. Blackberries were harvested at maturity stages 3 (light red) and 5 (dark purple), packed in PET clamshells (200±10 g) and stored under room temperature (18±2°C) or cold storage (8±1°C). The analyses were performed on days 0, 3, 6, and 9 of storage for sensory (visual quality, color, aroma, firmness and overall impression) and microbiological quality (total aerobic mesophiles, psychrotrophes, and yeasts and molds). Molds and yeasts' growth was the main factor limiting blackberries shelf-life. The counts for this microbial group continuously increased during the storage period, mainly under room temperature. Psychrotrophes were detected only after 6 and 9 days of cold storage in the more immature fruit and, regardless of maturity stage, mesophiles counts were greater in the blackberries stored at 18°C. The more mature fruit received higher scores in the sensory analyses and were preferred by the panelists as the blackberries harvested at maturity stage 3 were “too firm” and did not develop their full color and characteristic aroma. Based on our results, and even when the Ecuadorian Quality Standard allows to harvest blackberries when they reach the maturity stage 3, the fruit should be harvested at maturity stage 5 and kept under cold storage as refrigeration was effective in delaying microbial growth and in extending the shelf-life period from 3 days at 18°C to 8 days in cold storage.