Synthesis and characterization of lactic acid esterified starch by an in-situ solid phase method

Ping Li; Xiaoyu He; Yingfeng Zuo; Xianjun Li; Yiqiang Wu

doi:10.1016/j.ijbiomac.2019.11.171

Synthesis and characterization of lactic acid esterified starch by an in-situ solid phase method

Int J Biol Macromol. 2020 Aug 1:156:1316-1322. doi: 10.1016/j.ijbiomac.2019.11.171. Epub 2019 Nov 21.

Authors

Ping Li¹, Xiaoyu He¹, Yingfeng Zuo², Xianjun Li¹, Yiqiang Wu³

Affiliations

¹ College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan 410004, PR China.
² College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan 410004, PR China. Electronic address: zuoyf1986@163.com.
³ College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan 410004, PR China. Electronic address: wuyq0506@126.com.

PMID: 31760010
DOI: 10.1016/j.ijbiomac.2019.11.171

Abstract

To improve the hydrophobicity and thermoplastic processability of starch, lactic acid esterified starch (LA-e-starch) was prepared by in-situ solid phase esterification with corn starch as the raw material and LA as the esterifying agent. Fourier transform infrared spectroscopy confirmed that the esterification reaction was successful. The optimal esterification efficiency of LA-e-starch was obtained when the LA proportion was 20% by mass, catalyst ratio at 3%, reaction temperature 80 °C and reaction time 2.5 h. LA-e-starch was characterized by scanning electron microscopy (SEM), contact angle (CA) analysis, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) as well as its water absorption rate evaluated. Results showed that in-situ solid phase esterification mainly occurred on starch granule surfaces and did not destroy the starch granularity. LA-e-starch surfaces were covered with a layer of polylactic acid resin, which caused starch granules to stick together. The initial contact angle of LA-e-starch was clearly larger than that of native starch and the water absorption rate lower than native starch in a 168 h test time, which showed that esterification effectively improved the hydrophobicity of starch. This esterification destroyed the crystalline structure of starch to some extent, resulting in a crystallinity reduction to 25.16%. In addition, the gelatinization temperature and enthalpy were lower than those of native starch. XRD and DSC analyses indicated that esterification modification increased starch thermoplasticity. Also, LA-e-starch exhibited better thermal stability than native starch, from which it was inferred that this application of esterification could improve the thermoplastic processability of starch modify the interfacial compatibility between starch and polymer resins.

Keywords: Corn starch; Esterification modification; Hydrophobicity; In-situ solid phase method; Lactic acid; Thermoplasticity.

MeSH terms

Esterification
Hydrophobic and Hydrophilic Interactions
Lactic Acid / chemistry*
Starch / chemistry*
Surface Properties

Substances

Lactic Acid
Starch