Environmental aspects associated with quality variation in bilberries (Vaccinium myrtillus L.) from Norwegian populations – Results from a 4-years trial

Bilberry (Vaccinium myrtillus L.), also called European blueberry, is native to Norway and strongly preferred by the Norwegian food industry due to its genuine flavour and high content of phytochemicals. However, Norwegian natural resources are underexploited, and only few investigation have focused on quality aspects of bilberries from wild populations with regard to potential cultivation and industrial utilization. Important goals of the 4-years study were to investigate (a) Berry quality parameters, (b) Fertilization effects, and (c) Geographic and seasonal variation in trial locations at regions in Southern, Mid and Northern Norway. Berry quality assessment included parameters such as total anthocyanins (ACY) and phenols (TPH), antioxidant capacity (AOX), pH, titratable acidity (TAC) and soluble solids (SS). Based on multivariate statistics (PCA), regional segregation patterns could be observed which were strongly overlapped by year-to-year variation. Within-seasonal variation of parameters were recorded for berries harvested at different time points throughout the season (Southern location/ Hedmark), but between-seasonal effects were generally stronger. Similar year-to-year effects were also found in bilberries from Northern Norway (Bardu), but not in berries harvested from the field in Mid Norway/Langvatnet. The field in Northern Norway was treated with organic fertilizer (compost and wood chippings), while the field in Mid Norway was fertilized with mineral fertilizer combinations (N+P). Application of organic fertilizer did not have any clear effect on berry quality, while mineral fertilizer resulted in clear segregation patterns of berry samples after three years of treatment, thus minimizing year-to year variation. Mean values of quality parameters ACY, TPH and AOX, measured at the different locations (all years and treatments) varied between 330-427 mg/100 g f.w., 531-640 mg/100 g f.w., and 5-8 mmol/100 g f.w., respectively, thus underscoring the phytochemical value of bilberries from Norwegian populations.