Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd Starch-based Janus particles: Proof-of-concept heterogeneous design via a spin-coating spray approach Arkaye Kierulf a , Morteza Azizi a , Hamed Eskandarloo a , Judith Whaley b , Weichang Liu b , Mariana Perez-Herrera b , Zheng You b , Alireza Abbaspourrad a,∗ a Department of Food Science, College of Agriculture and Life Sciences, Cornell University, 243 Stocking Hall, Ithaca, NY, 14853, USA b Tate & Lyle Ingredients Americas LLC, 5450 Prairie Stone Pkwy, Hoffman Estates, IL, 60192, USA ARTICLE INFO Keywords: Janus Waxy cornstarch Amaranth Heterogeneous modifcation Patch Self-assembly ABSTRACT The asymmetric nature of Janus particles made from synthetic polymers gives them intriguing properties that have found applications in a wide variety of felds, such as drug delivery, emulsion stabilization, and environ- mental decontamination. The potential of using natural biopolymers as base materials for Janus particles in the food industry, however, has not yet been fully explored. Here we demonstrate for the frst time the design ofa starch-only-based Janus particle. Using a spin-coating spray approach, we produced both large (12.2 μm) half- porous, waxy cornstarch Janus granules by alpha-amylase treatment and small (1.2 μm) half-hydrophobic, amaranth starch Janus granules by octenyl succinic anhydride esterifcation. Optical microscopy, scanning electron microscopy, super resolution-structured illumination spectroscopy, and infrared spectroscopy were used to confrm the binary nature of these particles. A methylene blue adsorption test further showed that the un- treated (non-porous), half-porous Janus, and fully porous waxy cornstarch granules had fve-hour adsorption rates of 20.5, 72.1, and 100%, respectively, and adsorption capacities of 0.82, 2.88, and 3.96 mg/g. Meanwhile, untreated amaranth starch granules were shown not to interact with each other in water, while > 68% of the half-hydrophobic granules self-assembled into wormlike strings and micelles, and > 66% of the fully hydro- phobic granules aggregated into spherical, complex supermicelles. While the low yield typical of Janus particle formation prevents a more detailed characterization of these starch-based Janus particles, the unique properties they displayed here may open exciting, future applications in the food industry as texturants or surface-active agents, as well as in other felds requiring such uncanny materials. 1. Introduction “Janus particles”—i.e., solid particles featuring two diferent faces or sides—were frst popularized by Nobel Laureate P.G. de Gennes in the 1990s, largely due to properties that were uniquely diferent from that of their isotropic or one-faced counterparts (Hu, Zhou, Sun, Fang, & Wu, 2012; Zhang, Grzybowski, & Granick, 2017). Research progress in this area over the last two decades has produced a variety of distinctly shaped particles made using diferent methods and designed for dif- ferent applications. For example, Tanaka, Okayama, Minami, and Okubo (2010) used a solvent evaporation approach followed by radical polymerization to produce amphiphilic, mushroom-shaped, synthetic polymer-based particles that could be used to stabilize Pickering oil-in- water emulsions better than homogeneous particles due to their in- creased surface activity (Poggi & Gohy, 2017; Tanaka et al., 2010). Orozco, Mercante, Pola, and Merkoci (2016) sputter-coated a Pt catalyst onto one side of graphene oxide-covered SiO 2 spheres so that the Pt side would generate O 2 bubbles (by catalyzing the decomposition of hydrogen peroxide in water) and self-propel the particles to enable the graphene oxide side to remove organic pollutants more efciently as the particles moved (Orozco et al., 2016; Eskandarloo, Kierulf, & Abbaspourrad, Nano- and micromotors for cleaning polluted waters: Focused review on pollutant removal mechanisms, 2017; Eskandarloo, Kierulf, & Abbaspourrad, Light-harvesting synthetic nano- and micro- motors: a review, 2017). In medicinal research, by using a mini-emul- sion and sol-gel reaction, Wang et al. (2013) functionalized one side of a polystyrene nanoparticle with folic acid to make it preferentially bind to tumor cells, and then on the other side immobilized the anti-tumor agent doxorubicin for the purpose of targeted release (Wang et al., 2013; Poggi & Gohy, 2017). The versatility of synthetic polymers and inorganic materials has made them the main building blocks of Janus particles produced thus https://doi.org/10.1016/j.foodhyd.2019.01.037 Received 17 October 2018; Received in revised form 9 January 2019; Accepted 14 January 2019 ∗ Corresponding author. E-mail address: Alireza@cornell.edu (A. Abbaspourrad). Food Hydrocolloids 91 (2019) 301–310 Available online 16 January 2019 0268-005X/ © 2019 Elsevier Ltd. All rights reserved. T