Starch granules isolation

FIGURE 6.5 Scanning electron micrograph of starch granules isolated from Eleusine (Jideani et al., 1996. Reproduced with permission from Cereal Chemistry). 

Recent studies have shown that pores on maize starch granules develop during a late maturation stage, i.e. 30 days after pollination (DAP).39 Starch granules isolated from maize kernels harvested on 30 DAP show few or no pores, whereas those from kernels harvested on 45 DAP (fully matured and dried in the field) show a large number of pores.39 Heavily pitted starch granules are observed close to the germ of maize kernels in a dormant state.40... 

Steup. M., Robenek, H., and Melkonian, M. 1983. In vitro degradation of starch granules isolated from spinach chloroplasts. Planta 158, 428-436. 

Amylase has been isolated and purified, to a state free from contaminating enzymes, from barley malt and ungerminated barley grains, respectively. Starch granules, isolated from the same sources, served as substrates to study the mode of action of amylases on the digestion of starch granules in vitro (see p. 480). 

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. 

Table 3.2 Amylose content of starch granules of various size classes isolated from maize endosperm 36 days post-pollination and from intermediate size (5-6 cm) potato tubers...

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