Phenolic Compound Content and the Antioxidant and Antimicrobial Activity of Wild Blueberries (Vaccinium stenophyllum Steud.) Fruits Extracts during Ripening

The genus Vaccinium contains about 400 species distributed worldwide, but only a few species and varieties have had their phenolic composition and biological activity documented. In this study, phenols, flavonoids, anthocyanins, antioxidant and antimicrobial activity of methanolic extracts of Vaccinium stenophyllum Steud. fruits: 1-totally immature, 2-immature, 3-immature/close to maturity and 4-mature, were determined using UV-Visible spectrometry and HPTLC. The totally immature fruit extract showed the highest content of total phenols (19.153 ± 0.175 mg GAE/g DW), chlorogenic acid (20.867 ± 0.240 mg CAE/g DW), and the highest antioxidant activity by ABTS●+ (196.761 ± 0.641 µM TE/g DW) and DPPH● (146.580 ± 6.466 µM TE/g DW). Immature, immature/close to maturity and mature fruits extracts, exhibited the lowest MIC (9.37 mg/mL) and MBC (18.75 mg/mL) against Escherichia coli, Salmonella choleraesuis, and Shigella flexneri. The mature fruits extract exhibited the highest content of total anthocyanins (0.141 ± 0.004 mg CE/g DW) and cyanidin-3-glucoside (19.230 ± 0.309 mg CGE/g DW). The content of phenols, flavonoids and anthocyanins was higher than that reported for other Vaccinium species. These results showed the relevance of Vaccinium stenophyllum Steud. for breeding purposes to enhance the bioactivity of cultivars, or as a source of natural additives for the food industry, among others.

Is Drought Increasing in Maine and Hurting Wild Blueberry Production?

A few severe drought events occurred in the Northeast (NE) USA in recent decades and caused significant economic losses, but the temporal pattern of drought incidents and their impacts on agricultural systems have not been well assessed. Here, we analyzed historical changes and patterns of drought using a drought index (standardized precipitation-evapotranspiration index (SPEI)), and assessed drought impacts on remotely sensed vegetation indices (enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI)) and production (yield) of the wild blueberry fields in Maine, USA. We also analyzed the impact of short- and long-term water conditions of the growing season on the wild blueberry vegetation condition and production. No significant changes in the SPEI were found in the past 71 years, despite a significant warming pattern. There was also a significant relationship between the relatively long-term SPEI and the vegetation indices (EVI and NDVI), but not the short-term SPEI (one year). This suggests that the crop vigor of wild blueberries is probably determined by water conditions over a relatively long term. There were also significant relationships between 1-year water conditions (SPEI) and yield for a non-irrigated field, and between 4-year-average SPEI and the yield of all fields in Maine. The vegetation indices (EVI and NDVI) are not good predictors of wild blueberry yield, possibly because wild blueberry yield does not only depend on crop vigor, but also on other important variables such as pollination. We also compared an irrigated and a non-irrigated wild blueberry field at the same location (Deblois, Maine) where we found that irrigation decoupled the relationship between the SPEI and NDVI or EVI.

Field Capacity and Harvest Efficiency Evaluation of Traditional Small Box and Semi-Automated Bin Handling Systems for Wild Blueberries

Mechanical harvesters with small box and semi-automated bin handling systems are increasingly being used for harvesting wild blueberries in Eastern Canada, and Northeastern, USA. However, their field capacity and performance have not been quantified and compared. Important measures of field capacity and efficiency for a traditional mechanical harvester were compared with a novel semi-automatic bin handling harvester. Data were obtained from on-farm field trials conducted at four sites in Nova Scotia, Canada in 2017 and 2018. Both harvesters had double head configurations, along with other similar engineering configurations: (i) 0.66 m picking reels; (ii) 16 picker bars per head and 65 teeth per bar; (iii) 1.72 m picking width; (iv) 21 rpm head speed; and (v) 0.31 ms−1 ground speed. Each harvester was operated for 120 min and data such as berry harvesting time and box handling time were recorded, with six replications during each year. Statistical methods were used to compare the harvest efficiency of the two mechanical harvesters. Harvest time efficiency was significantly higher for the semi-automatic bin handling technology than for the small box handling technology both in 2017 (p < 0.001), and 2018 (p < 0.001). Weed coverage did not have a significant effect of harvest time in either 2017 (p = 0.694) or 2018 (p = 0.765), though it did significantly affect yield in both 2017 (p = 0.011) and 2018 (p = 0.045). The findings provide useful insights for decision-makers contemplating the choice of harvesting technology to sustain profits from wild blueberry production.

Are Wild Blueberries a Crop with Low Photosynthetic Capacity? Chamber-Size Effects in Measuring Photosynthesis

Wild lowbush blueberries, an important fruit crop native to North America, contribute significantly to the economy of Maine, USA, Atlantic Canada, and Quebec. However, its photosynthetic capacity has not been well-quantified, with only a few studies showing its low photosynthetic rates. Its small leaves make accurate leaf-level photosynthetic measurements difficult and introduce potential uncertainties in using large leaf chambers. Here, we determined the photosynthetic rate for five different wild blueberry genotypes using a big leaf chamber enclosing multiple leaves and a small leaf chamber with a single leaf to test whether using big leaf chambers (branch-level measurements) underestimates the photosynthetic capacity. Photosynthetic rates of wild blueberries were significantly (35–47%) lower when using the big leaf chamber, and they are not a crop with low photosynthetic capacity, which can be as high as 16 μmol m−2 s−1. Additionally, wild blueberry leaves enclosed in the big chamber at different positions of a branch did not differ in chlorophyll content and photosynthetic rate, suggesting that the difference was not caused by variation among leaves but probably due to leaf orientations and self-shading in the big chamber. A significant linear relationship between the photosynthetic rate measured by the small and big leaf chambers suggests that the underestimation in leaf photosynthetic capacity could be corrected. Therefore, chamber-size effects need to be considered in quantifying photosynthetic capacity for small-leaf crops, and our study provided important guidelines for future photosynthesis research. We also established the relationship between the Electron Transport Rate (ETR) and photosynthetic CO2 assimilation for wild blueberries. ETR provides an alternative to quantify photosynthesis, but the correlation coefficient of the relationship (R2 = 0.65) suggests that caution is needed in this case.

Effects of Daily Wild Blueberry Consumption on Cognitive and Vascular Function in Healthy Older Individuals: A Randomized Double Blind Controlled Trial (the Bluflow Study)

Objectives To investigate the effects of 12-week daily consumption of wild blueberry (poly)phenols on cognitive performance, vascular function, cerebral blood flow and gut microbiome in healthy older individuals. Methods A parallel, double blind, placebo controlled RCT was conducted in 61 healthy individuals, aged 65–80 years. The impact of wild blueberry (poly)phenols on cognition, vascular function (flow-mediated dilation; FMD, and blood pressure; BP), active and resting cerebral blood flow (CBF; using transcranial doppler ultrasound) was assessed. Measurements were taken at baseline and 12-weeks following daily consumption of 26 g freeze-dried blueberry powder containing 260 mg anthocyanins (equivalent to 178 g fresh wild blueberries) or a placebo powder matched for colour, taste, nutrients and fibre. Faecal samples were collected in both visits to measure changes in the gut microbiome using 16s rRNA sequencing. Blood and 24 h urine samples were also collected for the analysis of plasma and urinary (poly)phenol metabolites using LC-MS and authentic standards. Results Linear mixed modelling analysis with baseline performance as a covariate, revealed that accuracy scores for the switching task targeting executive function, significantly improved for the wild blueberry (WBB) group compared to placebo at 12 weeks (F(1,90,12) = 5.13, P = 0.026)). Additionally, immediate recall measure (AVLT) examining short-term recall memory revealed a significant improvement for the WBB compared to placebo at 12 weeks (F(1,46) = 4.321, P = 0.043)). FMD improved by 0.86% (F(1,54) = 32.8, P &lt; 0.001) in the WBB group compared with the placebo group after 12-weeks daily consumption. Systolic 24 h ambulatory BP decreased by −3.59 mmHg (F(1,51) = 4.6, P = 0.037) in the WBB group compared to the placebo group. No changes in active or resting CBF were observed between groups. Conclusions This data suggests that daily consumption of wild blueberries may improve cognitive and vascular function in older adults. The role of circulating (poly)phenol metabolites and the gut microbiome on the effects observed is currently under investigation. Funding Sources Wild Blueberry Association of North America.

Development and Evaluation of a Closed-Loop Control System for Automation of a Mechanical Wild Blueberry Harvester’s Picking Reel

Mechanical harvesting of wild blueberries remains the most cost-effective means for harvesting the crop. Harvesting of wild blueberries is heavily reliant on operator skill and full automation of the harvester will rely on precise and accurate determination of the picking reel’s height. This study looked at developing a control system which would provide feedback on harvester picking reel height on up to five harvester heads. Additionally, the control system looked at implementing three quality of life improvements for operators, operating multiple heads until the point when full automation is achieved. These three functions were a tandem movement function, a baseline function, and a set-to-one function. Each of these functions were evaluated for their precision and accuracy and returned absolute mean discrepancies of 3.10, 2.20, and 2.50 mm respectively. Both electric and hydraulic actuators were evaluated for their effectiveness in this system however, the electric actuator was simply too slow to be deemed viable for the commercial harvesters. To achieve the full 203.2 mm stroke required by the harvester head, the electric actuator required 13.96 s while the hydraulic actuator required only 2.30 s under the same load.