Morphology and structure of acorn starches isolated by enzymatic and alkaline methods

Abstract

Morphology and structure of starch from fruits of two acorns species, Quercus rotundifolia Lam. (QR) and Quercus suber Lam. (QS), isolated by enzymatic (ENZ) and alkaline (A3S) methods were studied. Acorn starches granules presented a round and oval shape, consisting of medium/small granules, with a mean granule size ranging between 9 and 13 µm. Isolated acorn starches appear as light grayish-brown in naked eye, with high values of L* for starches isolated by the ENZ method, and QR starches were duller than QS. No differences were observed for all the samples in FTIR spectra results. Acorn starches showed a C-type pattern, with a relative crystallinity between 43.1 and 46.6%. The 13C CP/MAS NMR spectra are different for the used isolation methods but are similar for both acorn species. However, acorn-isolated starches presented a predominant A-type allomorph packing type, and the A3S starches showed a higher degree of crystalline material. Those differences in the structure of acorn starches would be helpful to better understand the relationships among structure and functional properties for a possible potential industrial application of chestnut starches.

The Effect of Starch Isolation Method on Morphological and Physicochemical Properties of Zagros Oak (Quercus brantii var. Persica) Starch

“…The satisfactory yield of EAE can be attributed to the efficiency and specificity of the enzyme to digest the proteins attached to a surface of starch granules and interrupt the starch–protein interactions. [ 19,20,34 ] In WME and EAE method the maximum yield was obtained in B‐level (i.e., WME‐B and EAE‐B). It was suggested that suitable treatment time and higher acid concentration increase the starch yield and purity by decreasing the protein level of the isolated starch.…”

“…[ 10 ] EAE method also can preserve the structure of the starch with selective proteolytic action. [ 34 ]…”

“…[ 38 ] This behavior was also reported in previous studies. [ 15,16,34,61 ] For example, Correia et al. did not report any outstanding differences in the spectra of starch isolated by alkaline and enzymatic methods.…”

“…did not report any outstanding differences in the spectra of starch isolated by alkaline and enzymatic methods. [ 34 ]…”

“…The spectra of the sample showed peaks confirmed the polysaccharide nature of the starches (at ≈3335–3427, 2929, 1645, 1360, 1156, 1010, 928, and 915–760 cm −1 ) which is in agreement with those found in previous studies for different acorn starches. [ 34,50,62 ] These peaks are related to various bonds such as O─H, C─H, C─C, C─OH, and etc. listed in Table 2 .…”