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

Basheer Aaliya,Plachikkattu Parambil Akhila,Cherakkathodi Sudheesh,Maximilian Lackner,Kappat Valiyapeediyekkal Sunooj,Johnsy George,Muhammed Navaf,Chillapalli Babu Sri Rajkumar

doi:10.3390/polym13213855

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%.

Highlights

Starch is a naturally occurring biopolymer with an extended application in food and non-food industries, owing to its technological properties, bioavailability, biodegradability, and safety
Talipot starch modified by phosphorylation alone and phosphorylation and thermal pretreatments remarkably changed the starch granule characteristics and starch paste functionality compared to NTS
The phosphorylation modification in talipot starch was confirmed by the increased P content and degree of crosslinking (DC) of PTS versus NTS, and the P content and DC of thermal pretreated phosphorylated starches was significantly greater (p ≤ 0.05) than PTS

Summary

Introduction

Starch is a naturally occurring biopolymer with an extended application in food and non-food industries, owing to its technological properties, bioavailability, biodegradability, and safety. It is a well-favored, multifunctional and renewable material majorly sourced from cereals, seeds, roots, and tubers [1]. Starch is a storage polysaccharide made up of chains of linear amylose and branched amylopectin. Native starch possesses certain undesirable characteristics such as low shear stress resistance, high retrogradation and syneresis tendency [3,4]. Native starch is subjected to physical, chemical, enzymatic, and genetic modifications to improve functionality and nutritional benefits, such as increasing resistant starch (RS) content [5]

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