Pollination affects the nutritional quality of almonds

While it is clear that pollination by insects is key to a large slice of our agricultural systems, the effect it has on the quality of the produce is just starting to emerge as a topic of research. For instance, we now have evidence that the nutritional composition of some crops like canola and sunflower is significantly benefited by bee pollination. Likewise, mandarin orange is found to have higher sugar content when effective pollination takes place.

Almonds, like other nuts, are nutrient-dense foods that provide a rich source of plant-based lipids and proteins as well as other micronutrients. Given their almost obligate dependence on pollinators, a study by Brittain et al (2014)(1) is the first, and so far the only, of its kind to actually assess the nutritional differences in almonds subjected to varying pollinating treatments in combination with limiting plant resources.

‘Nonpareil’, the most popular variety of almonds grown in California was subjected to four individual treatments: cross-pollinated, self-pollinated, reduced water and no fertilizer, and the combination of the four. While assessing a number of macro and micronutrients the study concentrated on the variation in levels of fats, specifically the ratio of oleic to linoleic acid, and vitamin E as these are principal nutrients that almonds are valued for.

The study found that cross-pollinated almonds had higher oleic to linoleic acid ratio but self-pollinated almonds had higher levels of vitamin E. The water and fertilizer did not significantly alter the nutrient levels, as their effects are not expected to affect the yield significantly in short term studies. Higher oleic to linoleic acid ratio is a desirable feature of not just almonds but other nuts too as it aids better storage, enhances flavor, and has potential health benefits. High vitamin E levels in self-pollinated almonds were a surprising finding, tentatively explained by the slower development of these nuts.

This and a previous study by the authors demonstrated that self-pollinated almonds are larger in size than cross-pollinated ones. The researchers went on to test the hypothesis whether the nuts of differing sizes, obtained through open pollination by bees, show the difference in nutritional quality. They found this not to be the case thus indicating that while pollination affects the weight of the fruit, the weight of the fruit does not affect the nutritional quality, which in turn indicates that the pollination process affects the ratio of nutrients directly. Just like agricultural practices and climate, pollination affects the nutritional value and hence commercial quality of the almonds and should be researched further to better understand the actual economic and health value it brings to crops like almonds.

1. Brittain C, Kremen C, Garber A, Klein A-M (2014) Pollination and Plant Resources Change the Nutritional Quality of Almonds for Human Health. PLoS ONE 9(2): e90082. https://doi.org/10.1371/journal.pone.0090082

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