Characterization of starch nanoparticles obtained from Araucaria angustifolia seeds by acid hydrolysis and ultrasound

Native starch (NS) extracted from the seeds of pinhão (Araucaria angustifolia) was modified by two methods: acid hydrolysis (AH) and ultrasound (US). The three starch samples were subjected to spray drying and characterized. Chemical composition and rheological characteristics were evaluated and morphology was analyzed by scanning electron microscopy. The starch modified by US and AH achieved nanometric size, with mean particle size of about 453 and 22 nm, respectively. Besides the modified starch reached nanometric size, the three starch preparations were significantly different in four characteristics: starch and amylose content, the percentage of syneresis and colorimetric data. The AH sample differed from the others in terms of solubility (more soluble), hygroscopicity (more hygroscopic) and paste clarity (more translucent). Modified starch nanoparticles obtained by AH and US can be useful for development of novel biocomposites with improved properties to be employed as coating materials or films. •The starch from Araucaria angustifolia seeds was modified by acid hydrolysis and ultrasound.•Starch nanoparticles were obtained by either acid hydrolysis or ultrasound processing.•Most chemical and physical properties of the modified starches remained as the native starch.•Starch modified by acid hydrolysis showed higher solubility and paste clarity, and lower amylose content.