Title: Variability of Phytonutrient Content of Potato In Relation to Growing Location and Cooking Method Author
Submitted to: Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2008
Publication Date: November 19, 2008
Citation: Brown, C.R. 2008. Variability of Phytonutrient Content of Potato In Relation to Growing Location and Cooking Method. Potato Research. 51:259-270. Interpretive Summary: Potato is a nutritious vegetable laden with vitamins, minerals and antioxidants. Two pigment classes are especially assoicated with potatoes, anthocyanins and carotenoids. Anthocyanins are strong antioxidants and anti-inflammatory compounds while carotenoids have similar capacities and in addition are major constituents of the human retina. Anthocyanins are water soluble compounds that impart red, blue, or purple color to skin and/or flesh. Carotenoids are flesh pigments that supply yellow to orange hue to the flesh. The potential variation in either of these pigments far exceeds the commercially available variation in most of the world. Anthocyanin concentration is strongly affected by environment, and is higher at high elevations, 1,550 meters above sea level, than at sea level by a factor of two. Carotenoids are less affected by growing location remaining stable through different elevations. Antioxidant capacity is also affected by growing location and was elevated in particular at the Powell Butte, Oregon high elevation site. Cooking method may increase or decrease antioxidant capacity. Boiling did not reduce antixoidant level and may have increased it. While baking and frying reduced antioxidant activity by about half. No method completely eliminated antixoidant activity. The characterization of performance of new potato breeding lines for pigment content and antioxidant activity establishes an information base for the development of new marketing strategies of potato.
Technical Abstract: Potato has a defined complement of metabolites that contribute to the human diet. Among these are the carotenoids and anthocyanins. Carotenoids are found in all potatoes in the flesh. White fleshed varieties have 50 to 100 micrograms per 100 grams FW, while moderately yellow fleshed varieties generally possess from 100 to 350 micrograms. The more intensely yellow fleshed genotypes which may look orange at the higher extremes are at levels above 1000 micrograms. The highest level published is 2600 micrograms in diploid germplasm derived from South American Papa Amarilla cultivars. Potato generally has predominantly lutein, a xanthophyll which is also found in the human retina, and must be obtained in the diet. The extremely high total carotenoids have zeaxanthin, an isomer of lutein, which is also present in the human retina. Anthocyanins are present in red or purple skinned and fleshed varieties. Total anthocyanins range from 1.5 mg per 100 g FW to 48 mg in a solidly pigmented purple skinned purple fleshed breeding line. The degree of pigmentation in the flesh appears to be under polygenic control. Anthocyanins are potent antioxidants and anti-inflammatories. The level of total anthocyanins are correlated with antioxidant level (r = 0.94, P < 0.001).. Total anthocyanins was strongly affected by growing locations, while total cartoenoids was not. Also, it was found that several methods of cooking interacted with genotypes in the level of antioxidant remaining after cooking. No method of cooking completely eliminated antioxidant activity while boiling appeared to increase it compared to raw potato in the case of the most highly pigmented clone.