To my knowledge, the ordered densely-packed double helix of amylopectin constitute the crystalline lamella, and we can determine the diffraction pattern and relative crystallinity (RC) for normal starches. As for high amylose starch (nearly 100% AM), does the major part amylose also constitute kind of crystalline lamella? in which form?
Dear Peng Guo
Could you be more directly in your question? are you taking about a particular food? if yes, could you specify which one? I think that those small details will help to understand better what are you looking for and therefore we will be able to answer properly your question,
All the best
Edenio
Also check https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/amylose
In addition to the useful review paper by Eric Bertoft provided by Chinaza Godswill Awuchi I have added a recent review on high-amylose (HAM) starches by H. Li et al, together with a paper on some basic properties of very high-amylose maize starch by Y.C. Shi et al. Most notable features are a shift from A to B crystalline type and a broadening of gelatinization temperature range to higher T.
- A quick literature search suggests that the lamellar spacing of 9 nm (with minor variation) as measured by small-angle X-ray scattering (SAXS) appears to be a fundamental property of crystalline granular starch, irrespective of amylose (AM) content. It has been reported that the intensity of the 9 nm SAXS peak as well as the difference in electron density between crystalline and amorphous zones decreases with increasing AM (P.J. Jenkins et al., Int. J. Biol. Macromol., 6 (1995) 315-321). Unfortunately I have no access to this key paper. [On the other hand B. Zhang et al. interpreted their SAXS-results on both high- and low-AM starches (?) as an increasing spread in lamellar thickness (see added file).] I also recommend to have a look at J. Xu et al., Carbohydr. Polym. 229 (2020) 115481 (not added).
- AM content seems also to have an effect on the structure at larger length scale (growth rings and blocklets) as revealed by atomic force microscopy (AFM). See M.J. Ridout, Biomacromolecules 5 (2004), 1519-1527 (not added).
I am not aware of any high amylose starch with 100% amylose. The crystalline structure of high amylose starches available is still due to amylopectin, similar to normal starches. If you extract 100% amylose or you purchase 100% amylose from Sigma, it may be pretty amorphous. If the sample is semi-crystalline, that is due to amylose-alcohol inclusion complex formed during precipitating amylose.
In his yesterday's comment, Peng Guo points out that he is interested in native or mutant starch cultivars with nearly 100 % amylose. This has been achieved by down regulation of starch branching enzymes, e.g. in maize, as described by Sidebottom et al. It has resulted in a mutant maize starch containing less than 5 % amylose. See the attached file. As you see in Fig 7, the granular morphology is still present but the granules are highly distorted.
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