Effect of Thermal Pretreatments on Phosphorylation of Corypha umbraculifera L. Stem Pith Starch: A Comparative Study Using Dry-Heat, Heat-Moisture and Autoclave Treatments

Abstract

Talipot starch, a non-conventional starch source with a high yield (76%) from the stem pith of talipot palm (Corypha umbraculifera L.) was subjected to three different thermal treatments (dry-heat, heat-moisture and autoclave treatments) prior to phosphorylation. Upon dual modification of starch with thermal treatments and phosphorylation, the phosphorous content and degree of crosslinking significantly increased (p ≤ 0.05) and was confirmed by the increased peak intensity of P=O and P–O–C stretching vibrations compared to phosphorylated talipot starch in the FT-IR spectrum. The highest degree of crosslinking (0.00418) was observed in the autoclave pretreated phosphorylated talipot starch sample. Thermal pretreatment remarkably changed the granule morphology by creating fissures and grooves. The amylose content and relative crystallinity of all phosphorylated talipot starches significantly decreased (p ≤ 0.05) due to crosslinking by the formation of phosphodiester bonds, reducing the swelling power of dual-modified starches. Among all modified starches, dry-heat pretreated phosphorylated starch gel showed an improved light transmittance value of 28.4%, indicating reduced retrogradation tendency. Pasting and rheological properties represented that the thermal pretreated phosphorylated starch formed stronger gels that improved thermal and shear resistance. Autoclave treatment before phosphorylation of talipot starch showed the highest resistant starch content of 48.08%.

Preparation, Characterization, and Utilization of Crosslinked and Dual‐Modified Banana Starch for Stabilizing Pickering Emulsion

“…[48] Moreover, all samples have higher elastic modulus than loss modulus, which indicates all samples had solid and elastic dominating gel structure than viscous. A similar study was reported for xanthan gum with DHT waxy rice starch and talipot crosslinked, talipot DHT starch by Li et al [65] and Aaliya et al [10]…”

“…In addition, the DHT increases the interactions between the starch chains and reduces the diffusions of amylopectin molecules, reducing the molecular interaction between water and starch. [56] A similar finding was reported by Aaliya et al [10] for crosslinked and dry-heated talipot starch. The swelling power of the OSA modified sample was the highest at all cooking temperatures, might be due to weakening of the intermolecular hydrogen bonds between bulky groups of OSA, which allowed more water molecules to interact with the free -OH groups of starch molecules.…”

“…[37] In addition, the amylose content of dry heated and dual modified starches was further decreased due to increased mobility and reorganization of the amylose chain after heating at high temperature, which increased the amyloseamylose and/or amylose-amylopectin interaction and reduced the iodine complexing ability of amylose. [38] A similar finding was reported by Aaliya et al [10] for dual-modified talipot starch. The 3% OSA esterified starch had the least amount of amylose content (9.28%) due to disruption of the amorphous region containing the amylose chain by alkali treatment for OSA esterification.…”

“…The dual modification of waxy maize and talipot starch with a crosslinker, heat moisture treatment (HMT), and dry heat treatment (DHT) changes the physicochemical properties. [9,10] Park et al [9] found that crosslinked-HMT maize starch had low swelling power, low paste viscosity, high melting point, and low ∆H values compared to crosslinked starch. Moreover, the crosslinked-HMT starch was particularly efficient in producing resistant starch in raw (28.7%-41.5%) and gelatinized (23.3%-25%) forms.…”

“…In another study. Aaliya et al [10] observed that the amylose content and relative crystallinity of phosphorylated starches decreased significantly due to the formation of phosphodiester bonds by the crosslinker. The dual-modified starches showed a reduction in swelling power, exhibited better light transmittance values, and had a lower retrogradation tendency.…”