Summer (subarctic) versus winter (subtropic) production affects spinach (Spinacia oleracea L.) leaf bionutrients: vitamins (C, E, Folate, K1, provitamin A), lutein, phenolics, and antioxidants.

Comparison of spinach (Spinacia oleracea L.) cultivars Lazio and Samish grown during the summer solstice in the subarctic versus the winter solstice in the subtropics provided insight into interactions between production environment (light intensity), cultivar, and leaf age/maturity/position affecting bionutrient concentrations of vitamins (C, E, folate, K1, provitamin A), lutein, phenolics, and antioxidants. Growing spinach during the winter solstice in the subtropics resulted in increased leaf dry matter %, oxidized (dehydro) ascorbic acid (AsA), α- and γ-tocopherol, and total phenols but lower reduced (free) AsA, α-carotene, folate, and antioxidant capacity compared to summer solstice-grown spinach in the subarctic. Both cultivars had similar bionutrients, except for higher dehydroAsA, and lower α- and γ-tocopherol in 'Samish' compared to 'Lazio'. For most bionutrients measured, there was a linear, and sometimes quadratic, increase in concentrations from bottom to top canopy leaves. However, total phenolics and antioxidant capacity increased basipetally. The current study has thus demonstrated that dehydroAsA, α-tocopherol, and γ-tocopherol were substantially lower in subarctic compared to subtropical-grown spinach, whereas the opposite relationship was found for antioxidant capacity, α-carotene, and folates (vitamin B9). The observations are consistent with previously reported isolated effects of growth environment on bionutrient status of crops. The current results clearly highlight the effect of production environment (predominantly radiation capture), interacting with genetics and plant phenology to alter the bionutrient status of crops. While reflecting the effects of changing growing conditions, these results also indicate potential alterations in the nutritive value of foods with anticipated shifts in global climatic conditions.

Relationship between fresh-packaged spinach leaves exposed to continuous light or dark and bioactive contents: effects of cultivar, leaf size, and storage duration.

Current retail marketing conditions allow produce to receive artificial light 24 h per day during its displayed shelf life. Essential human-health vitamins [ascorbic acid (vit C), folate (vit B(9)), phylloquinone (vit K(1)), alpha-tocopherol (vit E), and the carotenoids lutein, violaxanthin, zeaxanthin, and beta-carotene (provit A)] also are essential for photosynthesis and are biosynthesized in plants by light conditions even under chilling temperatures. Spinach leaves, notably abundant in the aforementioned human-health compounds, were harvested from flat-leaf 'Lazio' and crinkle-leafed 'Samish' cultivars at peak whole-plant maturity as baby (top- and midcanopy) and larger (lower-canopy) leaves. Leaves were placed as a single layer in commercial, clear-polymer retail boxes and stored at 4 degrees C for up to 9 days under continuous light (26.9 micromol.m(2 ).s) or dark. Top-canopy, baby-leaf spinach generally had higher concentrations of all bioactive compounds, on a dry weight basis, with the exception of carotenoids, than bottom-canopy leaves. All leaves stored under continuous light generally had higher levels of all bioactive compounds, except beta-carotene and violaxanthin, and were more prone to wilting, especially the flat-leafed cultivar. All leaves stored under continuous darkness had declining or unchanged levels of the aforementioned bioactive compounds. Findings from this study revealed that spinach leaves exposed to simulated retail continuous light at 4 degrees C, in clear plastic containers, were overall more nutritionally dense (enriched) than leaves exposed to continuous darkness.