ORIGINAL PAPER Esterification of pea starch with octenyl succinic anhydride using conventional and microwave irradiation method: synthesis and characterization Hitendra S. Mahajan 1 & Yogesh A. Sonar 1 Received: 20 June 2019 /Accepted: 10 August 2019 # The Polymer Society, Taipei 2019 Abstract The purpose behind this investigation was to modify native pea starch by means of the microwave-assisted and conventional method of esterification by utilizing octenyl succinic anhydride (OSA) as esterifying agent and investigation of structural as well as its functional properties. The present investigation shows the direct esterification of pea starch using OSA (esterified-starch) under alkaline conditions to activate the native pea starch and followed by terminating the esterification process of starch by maintaining acidic conditions. Starch esters, containing amphiphilic groups are well known to enhance emulsification properties, and after hydrolysis employed for encapsulation. The esterification of pea starch was confirmed by FTIR and nuclear magnetic resonance. Structural changes were confirmed by XRD, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and by molecular weight determination. Some functional properties were investigated by performing emulsification capacity, oil absorption capacity, emulsion stability, transparency, and viscosity determination. Both OSA-modified starches were compared with native pea starch. Esterification of pea starch with OSA enhanced the emulsification with an attractive scope of consistency that makes it appropriate as a divider material for encapsulation. Keywords Pea starch . Microwave esterification . Octenyl succinic anhydride . OSA-starch . Conventional esterification Introduction Starch is an eatable polymer likewise the most inexhaustible polysaccharide stored in tubers, grains and roots furthermore starch is a biodegradable and sustainable polymer [1]. Lipophilically altered water-soluble starches are widely appli- cable, such as thickness modifiers, coating agent, as a stabi- lizer in the biphasic dosage form and as surfactants [2]. The polymer surface properties play a vital role in their capacity of intermolecular attachment, on surfaces spreading properties and dispersing of oils and other lipophilic compounds. The starch of grain legume seeds is an interesting polysaccharide macro component. Legumes belong to the Leguminosae fam- ily plants [3]. It has been used for the production of amylase, sugars, and dextrins as a crude material [2, 4, 5]. Pea starch is nothing but the byproduct obtained after protein extraction. Therefore, pea starch is acknowledged as a relatively cheap source of starch in contrast to other starch material obtained from potato, corn, and wheat. Pea starch is widely utilized in industrial applications, yet very less used in food applications because of its poor functionality [6]. Chemical alteration on the B-D-glucopyranosyl units of pea starch basically involves oxidation of hydroxyl groups, etherification, esterification, etc. [7]. The esterification can be achieved by reacting starches with a various alkenyl succinic anhydride, for example, octenyl, octadecyl, dodecyl succinic anhydride. Esterified starch is one of the prominent amphiphilic derivatives. Besides all modifications, esterified starch permits maximum 3.0% OSA for modification of native starch in food applications as per U.S. official regulations [5, 8, 9]. Previously reported octenyl succinic (OS) starch esters were prepared using native starch obtained from various sources like tapioca, corn, cassava, wheat, rice, potato starch and even maltodextrins and gum arabica [1, 8–15] were * Hitendra S. Mahajan hsmahajan@rediffmail.com 1 Department of Pharmaceutics, R. C. Patel Institute of Pharmaceutical Education & Research, Karwand Naka, Shirpur, 425405, Dist., Dhule, Maharashtra State, India Journal of Polymer Research (2019) 26:247 https://doi.org/10.1007/s10965-019-1887-1