foods Article Effect of Various Types of Sugar Binder on the Physical Properties of Gum Powders Prepared via Fluidized-Bed Agglomeration Donghyeon Lee, Gyeongeon Min, Wooseok Roh and Byoungseung Yoo * Department of Food Science and Biotechnology, Dongguk University-Seoul, Goyang 410-820, Gyeonggi, Korea; [email protected] (D.L.); [email protected] (G.M.); [email protected] (W.R.) * Correspondence: [email protected] Abstract: Particle agglomeration of fine gum powders to improve their physical and morphological characteristics is of crucial importance. Changes in the physical properties of guar gum, locust bean gum, and carboxymethyl cellulose powders subjected to fluidized-bed agglomeration with various sugar types as the binder were examined. The agglomerates with sugar binders had much larger particles (D50) and higher porosity (") than the corresponding fine gum powders, as confirmed by particle-size-distribution analysis and scanning electron microscopy. In particular, the carboxymethyl cellulose agglomerate exhibited much higher D50 and " values than the original fine gum powder, with sorbitol as the binder resulting in the highest D50 and " values. Except for guar gum with sorbitol as the binder, the guar gum and locust bean gum agglomerates with the other sugar binders showed lower Carr index and Hausner ratio values (thus exhibiting better flowability and lower cohesiveness) than the original powders, whereas those of the carboxymethyl cellulose agglomerates were higher. These findings indicate that the physical and structural properties of gum powders can be greatly Citation: Lee, D.; Min, G.; Roh, W.; improved according to the type of gum and sugar solution used in the agglomeration process. Yoo, B. Effect of Various Types of Sugar Binder on the Physical Keywords: Properties of Gum Powders Prepared physical property; gum powder; sugar binder; particle agglomeration via Fluidized-Bed Agglomeration. Foods 2021, 10, 1387. https://doi.org/ 10.3390/foods10061387 1. Introduction Academic Editor: Adamantini Fluidized-bed agglomeration (FBA) causes fine particles to cluster into larger ones, Paraskevopoulou leading to a porous aggregate much larger in size than the original particles. The agglomer- ate growth mechanism of FBA consists of three steps: (1) wetting of the liquid binder over Received: 4 May 2021 a dry powder and nucleating primary particles, (2) coalescing of nuclei and agglomerate Accepted: 11 June 2021 consolidation by compaction, and (3) agglomerate break-up and attrition by agitation [1]. Published: 16 June 2021 The FBA process improves the flowability, appearance, handling, and dispersion or disso- lution of fine particles by modifying their size, shape, density, and/or porosity [2]. In the Publisher’s Note: MDPI stays neutral food industry, agglomeration is applied when the principal objective is to produce porous with regard to jurisdictional claims in agglomerates with a suitable particle size that can be dispersed or dissolved quickly in a published maps and institutional affil- liquid [3]. Moreover, the agglomerated products can be final consumer foods (e.g., instant iations. powdered drinks) or products (e.g., gum or starch as a thickening or gelling agent) that are used in food processing [4]. In particular, a wide variety of food thickening or gelling agents mainly consisting of gums that must be agglomerated to avoid the formation of lumps or undissolved sediment during hydration. However, there is not much information Copyright: © 2021 by the authors. about using FBA on gum powders. Only a few researchers [5–7] have studied using FBA Licensee MDPI, Basel, Switzerland. on xanthan gum (XG) powder mainly used as an instant thickener for patients with swal- This article is an open access article lowing difficulty. They reported that the use of sugar and gum binder liquids could greatly distributed under the terms and enhance the physical properties of XG-based thickeners. Lee and Yoo [4] found that the conditions of the Creative Commons physical properties of agglomerated galactomannans could be considerably influenced by Attribution (CC BY) license (https:// the particle growth during agglomeration and the concentration of maltodextrin solution creativecommons.org/licenses/by/ 4.0/). used as a binder. They also suggested that the investigation of galactomannan gums Foods 2021, 10, 1387. https://doi.org/10.3390/foods10061387 https://www.mdpi.com/journal/foods Foods 2021, 10, 1387 2 of 15 agglomerated with different sugar binders is needed to understand the intermolecular interaction between galactomannans and sugar binder solution. In the FBA process, the binder solution usually undergoes a phase change due to the removal of the solvent, which leaves the solute behind as an adhesive [2]. Therefore, in FBA, both particle enlargement and drying can be carried out in the same equipment. The binder type is one of the parameters most widely varied in the FBA process to improve and modify the structure of agglomerated powders [8]. Many different types of binders have been used in particle size growth because the binder type plays a vital role in the physical and structural properties of agglomerates [9]. However, different binders at the same concentration have very different enlargement characteristics due to the intermolecular interactions between the particles in the presence of the binder solution [8]. It is well known that the different structural characteristics of agglomerates are considerably influenced by binder type [9]. Recently, several researchers [5,10–13] have described the effect of different binders on the FBA process to produce agglomerates for the food industry. Despite the importance of FBA, there is little information available on the physical effects of adding a sugar binder during gum-powder agglomeration. In the food industry, guar gum (GG), locust bean gum (LBG), and carboxymethyl cellulose (CMC) have been commonly used as thickening agents, or for dysphagia manage- ment because they are easy to swallow [14–16]. However, the underlying process of how FBA works on these gum powders is limited. Moreover, no attempt has yet been made to examine the effect of different types of sugar binders on the physical and structural properties of the agglomerates. The aim of this study was to examine the effect of various sugar binder solutions on the physical properties of agglomerates prepared via FBA by comparing them with their original fine gum powder. During these evaluations, the physi- cal and structural differences between GG, LBG, and CMC agglomerates prepared with different sugar binders were also investigated. The information presented in this study will provide additional knowledge to develop the agglomerated gum powders for thickening agents or food thickeners for people with dysphagia. 2. Materials and Methods 2.1. Materials Commercial GG (Habgen Guargums Ltd., Karachi, Pakistan), LBG (Incom Co., Mersin, Turkey), and CMC (Bolak Co., Ltd., Incheon, Korea) were used to produce agglomer- ates via the FBA process. The following sugars were used to prepare binder solutions: glucose (Samyang Co., Ltd., Seongnam, Korea), sucrose (Samyang Co., Ltd., Seongnam, Korea), lactose (Meggle Co., Ltd., Wasserburg, Germany), and sorbitol (Samyang Co., Ltd., Seongnam, Korea). 2.2. FBA Process A top-spray fluidized-bed granulator (Fluid Bed Lab System, Dae Ho Technology Co., Ltd., Hwaseong, Korea) was used for FBA. Binders were prepared by completely dissolving glucose, sucrose, lactose, or sorbitol in distilled water at room temperature to make a 10% (w/w) solution. Original fine gum powders (1500 g for GG and LBG; 750 g for CMC) were first placed in the product container and fluidized by an upward-flowing hot-air stream. The binder (1000 mL for GG and LBG; 500 mL for CMC) was then pumped through a peristaltic tube at a speed of 20 mL/min and sprayed into small droplets through a fluid spray nozzle onto the flowing powder with a pressure of 1.5 bar. Throughout the spraying process, the inlet air and product temperatures were adjusted to remain at 75 ± 1.0 ◦C and 53 ± 1.0 ◦C, respectively. Meanwhile, the blower and damper were also controlled to 70% and 30%, respectively. After the binder solution had been exhausted, the product was cooled and dried with fluidizing air at room temperature for 10 min. Foods 2021, 10, 1387 3 of 15 2.3. Particle Size Distribution (PSD) Measurements PSD measurements were made using a Malvern Mastersizer (Mastersizer 3000E, Malvern Instruments Ltd., Worcestershire, UK) based on the volume distribution. The D10, D50, and D90 values were the cumulative particle diameters where 10%, 50%, and 90% of the sample had smaller particle sizes than the given average particle size. The span index was calculated as (D90–D10)/D50. 2.4. Capillary Viscosity (hc) Measurements of the Sugar Solutions To measure the ηc values, 6 mL of binder solution was injected into a Cannon-Fenske capillary viscometer (Cannon Instrument Co., State College, PA, USA), and then the whole viscometer was immersed in a water bath (HBS 1000, Eyela, Tokyo, Japan) for 60 min to become thermostatically equilibrated at 25 ◦C. Once equilibration had been completed, ηc was measured as suggested by Bak and Yoo [17]. All measurements were carried out in triplicate. 2.5. Flowability and Cohesiveness Measurements Hausner ratio (HR) and Carr index (CI) values were calculated to measure the cohe- siveness and flowability of a powder, respectively. A powder was poured into a 100 mL graduated glass cylinder, and then the cylinder