Plant starches from

Polysaccharides formed from a-glucose are called starches. A starch stores sugar until it is needed for energy production. Three important starches are glycogen, which animals produce in their livers, and amylose and amylopectin, produced by plants through photosynthesis. On average, plant starch is about 20% amylose and 80% amylopectin. Each of these polysaccharides contains glucose as its monomer, but they differ in how the monosaccharide units are linked. 

While it is possible to use genetic engineering techniques to manipulate the sort of starch produced, at the time of writing the use of such starch in foods is illegal in Europe. The starch from genetically modified plants can, however, be used in industrial products such as adhesives. 

The variation between the starch from different plants is considerable. The percentage of amylose varies from 27% in maize starch through 22% in potato starch to 17% in tapioca starch. The waxy maizes are unusual in that they are almost pure amylopectin. This is extremely convenient because it avoids the need to separate amylopectin from amylose chemically. 

Obtaining Different Properties in the Starch. One method of obtaining a starch with different properties is the biological method of using a different type of plant. The best example of this is waxy maize, which yields a starch that is nearly pure amylopectin. The other method is to chemically modify the starch. Chemically modified starch is normally declared as modified starch . A whole range of modified starches are available. There is of course no bar to chemically modifying a starch from a special source. 

Ball, S. G. and Morell, M. K. (2003). From bacterial glycogen to starch Understanding the biogenesis of the plant starch granule. Ann. Rev. Plant Biol. 54, 207-223. 

What to do Remove overwintering brassica plants as soon as they have finished cropping. This should be done by mid-spring. Bury plant debris deep in a compost pile, or in a compost trench. Examine young plants regularly from early summer to fall and squash any colonies of eggs or young. Pesticides Insecticidal soap pyrethrum plant oils and starch-based sprays. 

Table 5 Particle size distribution and moisture of starch from different plants...

This is based on the method by Van Soest and Wine (1967) which has been modified according to subsequent recommendations. It is the only fibre determination suitable for non-ruminants. The residue consists of the plant cell-wall constituents cellulose, hemicellulose, lignin, cutin, NDF-insoluble tannin and ash. See the article by Cherney (2000) for current modifications these include the use of amylase to aid in the removal of starch from forages containing grain (Van Soest et al., 1991), which has been adopted by MAFF... 

Viks0-Nielsen, A., Blennow, A., Kristensen, K. H., Jensen, A., Moller, B. L. (2001). Structural, physicochemical, and pasting properties of starches from potato plants with repressed ri-gene. Biomacromolecules, 3, 836-841. 

Starch, used in pharmacy, consists of granules separated from the grains or tubers of different higher plants. Starches obtained from different sources may not have identical properties for specific pharmaceutical purposes and, therefore they should not be interchanged in the different formulas. 

Amylose consists of linear chains, whereas amylopectin has a branched structure (Fig. 5). These chemical differences give the two substances different properties which contribute towards the distinctive characteristics of a starch from a particular plant origin. 

Barley -for brewing [BEER] (Vol 4) -copper as nutrient for [COPPER COMPOUNDS] (Vol 7) -growth regulators for [GROWTHREGULATIONS - PLANT] (Vol 12) -m malting [MALTS AND MALTING] (Vol 15) -protein source [FOODS, NONCONVENTIONAL] (Vol 11) -starch from [CITEMURGY] (Vol 5)... 

E2.1 Overview of Laboratory Isolation of Starch from Plant Materials E2.2 Enzymatic Quantitation of Total Starch in Plant Products E2.3 Determination of Total Amy lose Content of Starch... 

Probably the most important carbohydrate polymer in food, certainly from a nutritional standpoint, is starch, and Chapter E2 presents three units that can be used for starch isolation and characterization. UNITE2.1 condenses many different starch isolation methods into one scheme for starch isolation from virtually any plant source. In this protocol, the author notes the care that must be taken to prevent starch degradation during isolation. unite2.2 presents a simple enzymatic analysis method that can be used for estimation of starch in food. Finally, unit E2.3 describes a colorimetric method to determine starch amylose content. Again, different combinations of the units in this chapter can be used to characterize starch from any source. 

E2.1 Overview of Laboratory Isolation of Starch From Plant Materials E2.1.1... 

In this protocol additional steps are taken to eliminate starch from the isolated cell wall material to minimize erroneous estimations of glucose in later analytical procedures. In some plant material only small numbers of very tiny starch granules may be found after staining with iodine in potassium iodide (see Basic Protocol 1) and these may be deemed too few to warrant the drastic action necessary to remove the large amounts of starch found in cells of potatoes for example. If the starch granules are small in size (e.g., <10 pm), then they are likely pass though the 11 -pm nylon mesh and be lost from the cell wall material however, to remove large amounts of starch, additional treatments with dimethyl sulfoxide (DMSO) and/or a-amylase are required. 

Outside of the use of cellulose for papermaking, starch is the most widely used plant-derived carbohydrate for non-food uses. Around 60 million tonnes of raw starch are produced per year for food and non-food uses. The US accounts for most of the world s production, utilising starch from maize, which accounts for over 80% of world production. The starch market in the US is driven by the large isoglucose sweetener market and now increasingly by the growing bioethanol market, which uses maize as a fermentation feedstock. Europe derives most of its starch from wheat and potatoes, which account for 8% and 5% of world starch production, respectively. The other main source of starch is cassava (tapioca), produced in South East Asia. Small amounts of oat, barley and rice are also exploited for starch production. Many edible beans are also rich in starches, but are not commonly exploited for non-food uses. 

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