Potatoes minerals

Some of the protein data presented here are outputs from the EU FP6 proj ect SAFE FOODS (Contract No. Food-CT-2004-506446), which is cordially acknowledged. The work of P JW on potato mineral composition is supported by the Scottish Government Rural and Environmental Research and Analysis Directorate (RERAD). 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Wszelaki AL, Delwiche JF, Walker SD, Liggett RE, Scheerens JC and Kleinhenz MD (2005) Sensory quality and mineral and glycoalkaloid concentrations in organically and conventionally grown redskin potatoes (Solanum tuberosum). Journal of the Science of Food and Agriculture, 85, 720-726. 

Chromium is a trace mineral that is necessary to process carbohydrates and fats, as well as to help cells respond properly to insulin—an especially important function for people with diabetes. Chromium, in its safest form, can be found in whole grains, seafood, green beans, peanut butter, and potatoes. As a dietary supplement, chromium is available in several forms, including chromium picolinate, chromium chloride, chromium nicotinate, and high-chromium yeast. 

Clockwise from top left) Plant problems Pea plants stressed by drought and heat leaf yellowing between the veins, a common symptom of mineral deficiency red currant bush with most of its leaves stripped to skeletons by the pest gooseberry sawfly the fungal disease potato blight... 

Fischer, A. and C. Richter (1986). Influence of Organic and Mineral Fertilizers on Yield and Quality of Potatoes. In Vogtmann, FI., Boehncke, E. and I. Fricke (1986). The Importance of Biological Agriculture in a World of Dimishing Resources. Proceedings of the 5 IFOAM International Scientific Conference at the University of Kassel (Germany) Kassel, 236-248. 

Humans require at least 22 mineral elements for their wellbeing (White and Broadley, 2005a). Potatoes are an excellent source of these elements (Storey and Davies, 1992 White et al., 2009). A single, medium-sized potato weighing 200 g fresh weight can provide about 26% of the US... 

Table 5.1 The mineral content of 200 g fresh weight of potatoes and its potential contribution to the US diet calculated as a percentage of the US Dietary Reference Intake (DRI).

Mineral contents are means of four potato varieties available In the USA (USDA, 2006) or the UK (FSA, 2002), with the exception of US potato I, which was taken from True et a I. (1978). The DRI values are those fora 31—50-year-old male (Food and Nutrition Board, 2004) ns = not sped fed. Adapted from White etal. (2009). 

Dietary Reference Intake (DRI) of Cu, 17-18% of the DRI of K, P, and Fe, and between 5 and 13% of the DRI of Zn, Mg, and Mn (Table 5.1). Potatoes are generally not rich in Ca, but can be a valuable source of trace elements, such as Se and I, if fertilized appropriately (Eurola et al., 1989 Poggi et al., 2000 Turakainen et al., 2004 Broadley et al., 2006). Moreover, since potato tubers have relatively high concentrations of organic compounds that stimulate the absorption of mineral micronutrients by humans, such as ascorbate (vitamin C), protein cysteine and various organic and amino acids (USDA, 2006), and low concentrations of compounds that limit their absorption, such as phytate (0.11-0.27% dry matter Frossard et al., 2000 Phillippy et al., 2004) and oxalate (0.03% dry matter Bushway et al., 1984), the bioavailability of mineral elements in potatoes is potentially high. 

Mineral elements are not synthesized by the plant. They must be acquired from the soil solution by the plant roots (Figure 5.3). Although tubers have associated roots, with the possible exception of Ca, these roots appear to supply only small amounts of minerals to tubers (Kratzke and Palta, 1985, 1986 Busse and Palta, 2006 Sowokinos, 2007). Most of the minerals present in potato tubers appear to have been taken up originally by the main roots that deliver them first to the shoot via the xylem. From the shoot, these mineral elements must be loaded into the phloem for... 

Distribution of mineral elements within potato tubers... 

Figure 5.5 Distribution of mineral elements within potato tubers. Data show longitudinal profiles of elements from the distal (Segment 1) to the stem end (Segment 5) of tubers from Stirling plants (N. Subramanian, G. Ramsay, M. R. Broadley and P.J. White, unpublished data).

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