26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Received: 11 February 2022 Revised: 23 March 2022 Accepted: 24 March 2022 DOI: 10.1002/fft2.149 RESEARCH ARTICLE Enriched puree potato with soy protein for dysphagia patients by using 3D printing Farnaz Mirazimi1 Jordi Saldo2,3 Francesc Sepulcre1 Alvar Gràcia4 Montserrat Pujola1 1 Departament d’Enginyeria Agroalimentària i Biotecnologia, Universitat Politècnica de Abstract Catalunya - Campus del Baix Llobregat, Dysphagia affects a person’s ability to swallow, and it causes health problems by Castelldefels, Catalonia, Spain 2 Animal and Food Science Department, directly limiting nutritional intake, being the elderly the most at-risk group and also Centre d’Innovació, Recerca i Transferència en likely to be deficient in nutrition. Diets for patients with dysphagia require textural Tecnologia dels Aliments (CIRTTA), XaRTA, TECNIO, Universitat Autònoma de Barcelona, modifications to offer soft and safe food to swallow. Puree is easily consumed by the Facultat de Veterinària, Cerdanyola del Vallès, elderly, being an alternative food preparation providing essential nutrition for people Catalonia, Spain with dysphagia. In this study, we aimed to create different formulations with soy pro- 3 CEPROBI-IPN, Yautepec, Morelos, Mexico 4 tein and agar added to potato puree to add nutritional value and end up with printable Natural Machines Iberia S.L., Barcelona, Spain material by designing food for the elderly and people with dysphagia. Some enriched potato puree formulations were obtained by adding soy protein (3%, 5%, and 7%) and Correspondence Jordi Saldo, Animal and Food Science, Centre up to 0.2% agar. The use of three-dimensional food printing allows visual customization d’Innovació, Recerca i Transferència en with appeal benefits of nutritional food formulations for specific consumers. The rhe- Tecnologia dels Aliments (CIRTTA), Universitat Autònoma de Barcelona Facultat de ology and texture profile analysis of the different formulations has been performed. Veterinària, XaRTA, TECNIO Cerdanyola del According to International Dysphagia Diet Standardisation Initiative (IDDSI) scales, Vallès, Barcelona, Spain. Email: jordi.saldo@uab.cat the texture of all modified samples was suitable for people with swallowing difficul- ties. The samples with agar presented a better-printed shape and a more viscous-like Funding information behavior than the samples with soy protein. These findings highlight that soy protein None. could modify the texture and, from the nutritional point of view, add value to the for- mulations. The addition of 0.2% agar can establish good material for designing three- dimensional (3D)-printed food that allows the creation of textures in accordance with the needs of the elderly and people with dysphagia. KEYWORDS IDDSI, texture modified, thixotropy, TPA, viscosity, yield stress This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2022 The Authors. Food Frontiers published by John Wiley & Sons Australia, Ltd and Nanchang University, Northwest University, Jiangsu University, Zhejiang Univer- sity, Fujian Agriculture and Forestry University. 706 wileyonlinelibrary.com/journal/fft2 Food Frontiers. 2022;3:706–715. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License MIRAZIMI ET AL . 707 1 INTRODUCTION and due to its characteristic physicochemical, mechanical, and rheolog- ical properties, it can modify food texture and is useful to control the Dysphagia is an age-related disease and one of the dominant prob- rheological properties in the design of foods for the elderly. The most lems for the elderly. Dysphagia is directly linked to nutritional defi- important function of agar at low concentration is as a thickening agent ciency and expansion risk of pneumonia for its impairment on the swal- (Nishinari et al., 2016). low function (Sura et al., 2012). The topic of dysphagia in the elderly Protein and starch are used in the formulation of many foods has become an increasingly important concern (Aslam & Vaezi, 2013). because of their textural characteristics and structural gelation behav- Approximately one quarter of elderly patients in care centers had dys- ior. The texture and stability of protein–polysaccharides interactions phagia, whereas almost half were malnourished (Bomze et al., 2021). depend on the properties of protein and polysaccharides but in addi- Untreated dysphagia may affect protein-energy malnutrition, lead- tion, their interaction will show the strength (Hemar et al., 2002). In ing to life-threatening conditions, a result of increased risk of accom- recent years, we can find an increasing number of studies on the inter- panying infections related to the immune system due to the nutri- action between starch and polysaccharides in academic and industrial tional deficit (Hudson et al., 2000). Dysphagia can be managed by pre- sectors (Quan et al., 2020). Adding soy protein to potatoes is not just scribing texture-controlled diets that seek to modify the consistency to create a formulation with high nutritional value and have a healthy of foods and/or drinks by changing the rate at which food is trans- product, but to enrich a better physiochemical, functional, and sensory ported through the pharynx and thus decreasing the risk of aspiration characteristic potato product for the elderly and people with dysphagia (Quinchia et al., 2011). For solid kinds of food, the texture is an impor- (Alvarez et al., 2012). tant factor to be considered because textural changes occur more dras- The overall objective of this study was to determine the effect of soy tically during oral processing in solid foods than in liquid foods. Rhe- protein and agar on the physicochemical properties of a formulation ological properties have a key role to understand swallowing process, based on puree potato for patients with dysphagia. The specific objec- being of paramount importance to be aware of dysphagia (Gallegos tives of this study were to study the rheological and textural measure- et al., 2012). Recently, the practical method for testing food texture ments to characterize the suitable range of formulation ingredients for and thickened fluids developed by International Dysphagia Diet Stan- people with dysphagia, and to create printable nutritional formulations dardization Initiative (IDDSI) have been widely welcomed by evaluat- to investigate possible opportunities to personalize food for the elderly ing diets for patients with dysphagia due to its simplicity and reliabil- with 3D food printing (3DFP) and to understand the effect of sieving on ity (Cichero et al., 2017). Hadde & Chen, 2021, identified several points the characteristic of the puree products. Our hypothesis was to iden- regarding the relevant parameters of swallowing for dysphagia man- tify the suitable range of formulation ingredients that can be printable agement. One of the important parameters of texture-modified foods formulate products for people with dysphagia. is the degree of structure, which is a combination of textural properties and particulate properties of the bolus, such as hardness, cohesiveness, adhesiveness, and particle size. It is possible to have indirect informa- 2 MATERIALS AND METHODS tion about particle size by measuring the IDDSI fork test and informa- tion related to food cohesiveness, adhesiveness, and hardness by mea- 2.1 Sample preparation suring the IDDSI spoon tilt test. Since recently, three-dimensional (3D) printing has gotten high con- Dehydrated potato puree (Maggi, purchased from a local supermarket) sideration for customized food and personalized meals, and the use of has the following nutritional values: energy 348 kcal, fat 0.8 g, carbo- this technology has become very important for people with specific hydrates 75 g, fiber 6.8 g, proteins 7.4 g, and salt 0.06 g. Soy protein nutritional requirements such as the elderly and people with swallow acid hydrolysate (SPAH) food-grade was procured from Sigma–Aldrich difficulties (Pant et al., 2021; Pérez et al., 2019). Adapting 3D printing (nitrogen analysis ≥12% total = 75% protein, calculated applying a fac- in the food sector induced a new challenge because most of the food tor of 6.25 g prot/g N). Powdered Agar (food grade) was purchased materials often consist of different ingredients with distinct physico- from Panreac AppliChem. chemical properties (Godoi et al., 2016). For all the food formulations, the same base (100 ml distilled water For elderly adults, nutrition plays an essential role in health and plus 17 g potato powder) was used and differed in soy (SPAH) and agar function (Baum & Wolfe, 2015). A dietary protein intake of at least amounts were added regarding the following codes: S3 (3 g soy), S6 (6 g 1.2 g/kg⋅day is required for older people (Nowson & O’Connell, 2015). soy), S9 (9 g soy), S3A (3 g soy and 0.2 g agar), S6A (6 g soy and 0.2 g Soy protein has multiple health benefits, because its high nutritional agar), and S9A (9 g soy and 0.2 g agar). value and desirable functionality have been included in a wide variety Samples were prepared by boiling 50 ml distilled water to dis- of formulated foods (Kinsella & Whitehead, 1989). Many studies show solve agar and added with 50 ml distilled water (25◦ C) where the cor- that consuming soy protein might be the reason for lower incidences of responding SPAH was incorporated. Subsequently, all samples were certain diseases (Hagen et al., 2009), and it is recognized that soy pro- placed in an oven at 90◦ C and kept for 30 min to denature the pro- tein at the same time as a low-fat diet can decrease the risk of certain tein and, as the last step, the dehydrated potato powder (17 g) was cancer (Lille et al., 2018; Nestel, 2002). Agar is obtained from seaweed, added. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 708 MIRAZIMI ET AL . The samples were kept overnight (22–24 h) in a fridge set at 2◦ C, and Each formulation was printed three times, either in the form of all samples were placed in an incubator at 20◦ C for 2 h before starting a pentagon prism for TPA assay or as some complex shapes such as the rheological measurements. snowflake, mountain, and honeycomb. The whole experiment was repeated three times. 2.4 International Dysphagia Diet Standardization 2.2 Rheological measurements Initiative tests The rheological measurements were carried out in a rheometer IDDSI divides modified food into eight levels (0–7) and presents a com- (Rheostress RS1, version 127, Barcelona, Spain) controlled with com- bination of tests to confirm which level texture is modified food for mercial computer software (HAAKE RheoWin 3 Job and Data Man- people with swallow difficulties (Cichero et al., 2017). Fork pressure ager Software). Samples were analyzed for their viscoelastic properties test and spoon tilt test were performed on the sieved samples. Fork using 35-mm plate–plate geometry with a 1 mm gap. After placing the test was done by pressing the fork by thumb until it blanched (pres- sample and trimming off the excess, the sample was let to rest for 2 min sure of ∼17 kPa), resembling the tongue pressure while swallowing. before starting the assay. The temperature was kept at 20.0 ± 0.1◦ C The spoon tilt test was completed for all formulations for experiment- during all the assays. A preliminary test was conducted to identify the ing with adhesiveness and cohesiveness (Cichero et al., 2017; Steele deformation limits for the linear viscoelastic region. et al., 2014). 2.2.1 Frequency sweep test 2.5 Texture properties characterization: TPA Oscillatory tests were performed to explain the behavior of material from 0.1 to 10 Hz to understand viscous or elastic dominating proper- 3D-printed pentagon shape was analyzed by textural profile analysis ties. Each sample from each of the 16 different formulations and three (TPA) test to determine its textural properties. TPA of printed sam- repetitions were measured independently three times. ples was performed at 20◦ C using a texture analyzer (TA.XTPlus, Sta- Rheological properties can be evaluated by the storage modulus (G′) ble Micro Systems, UK) with a compression plate (P/100). Double- and loss modulus (G″). cycle compression tests were performed at a pretest speed, test, and posttest speed of 2 mm/s, and a compression strain of 35%. Hardness, gumminess, cohesiveness, adhesiveness, and resilience were obtained 2.2.2 Rotational rheological measurements, from the recorded results, and duplicate values were averaged for each thixotropy, and yield stress replicate. The compression analysis was set at a distance of 30 mm and a speed The shear rate raised logarithmically from 0.1 to 10 s−1 during the first of 2 mm/s. The method adjusted the value of the speed to the printing 30 s, kept constant at 10 s−1 for 30 s, and finally was cut down loga- conditions of the Foodini. rithmically again to 0.1 s−1 over 30 s. For each sample, we recorded the viscosity (η) and the shear stress (τ), along with the yield stress (Tabilo- Munizaga & Barbosa-Cánovas, 2005). 2.6 Statistical analysis 2.3 3D food printing conditions Statistical analyses of the data were conducted on Minitab 18 (Minitab link. Coventry, UK). Data concerning rheology and textural character- All formulations were 3D printed using a commercial extrusion-based istics were tested for significant differences (p < .05) using analysis of 3D food printer (Foodini, Natural Machines Iberia S.L., Barcelona, variance, general linear model, and Tukey’s comparison test. Spain). Samples were printed using a nozzle with a diameter of 1.5 mm, the print speed was set at 3500 mm/min, the first ingredient holds at 4.2 mm, the first layer nozzle height was 1.4 mm and at the moment it 3 RESULTS is not possible to control the temperature with Foodini machine, so all the samples were printed at room temperature at 20◦ C. Before print- 3.1 Rheological properties of the formulation ing, all the samples were sieved to avoid the presence of lumps that may affect the printing process. A spoon was used to press the sam- 3.1.1 Viscosity ples through the 250 μm mesh sieve. Then, the stainless-steel printing capsules (100 ml) of Foodini were manually filled with the sieved sam- All soy-enriched potato puree samples exhibited a non-Newtonian ples. Food samples must be well pressed down inside printing capsules behavior as can be seen by the exponential decay of the viscosity with to avoid the presence of air bubbles. the increase of shear strain in Figure 1. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License MIRAZIMI ET AL . 709 F I G U R E 1 Rheological characterization of food formulations, viscosity versus shear rate. Each curve represents the average of three replicates per sample. (a) Viscosity before sieving and (b) viscosity after sieving. Note: S3 (3 g soy), S6 (6 g soy), S9 (9 g soy), S3A (3 g soy and 0.2 g agar), S6A (6 g soy and 0.2 g agar) and S9A (9 g soy and 0.2 g agar) Figure 1 shows that SPAH and agar had a significant (p < .05) effect having the strongest thixotropic properties which means requiring the on increasing the viscosity. The samples with different concentrations highest energy to break down the internal structure, with high resis- of SPAH had increased the viscosity at 0.3 s−1 shear rate from 3% (S3, tance to time-dependent flow and high levels of internal viscosity and 925 Pa⋅s) to 5% (S6, 1205 Pa⋅s), but from 5% (S6) to 7% (S9) 1104 Pa⋅s stability. However, upon decreasing the shear rate in the last part of the rate decreased. test, all formulations showed the capacity to reform the damaged inter- To evaluate the effect of sieving the formulation, a step necessary nal network and to recover their viscosities. to 3D print, the rheological properties were evaluated before and after sieving. Sieving slightly decreased the viscosity for samples with agar (Figure 1). For instance, the formulation S3A changed its apparent vis- 3.1.3 Yield stress cosity at 0.3 s−1 from 1409 to 1289 Pa⋅s after sieving and it also occurs with S6A (from 1606 to 1458 Pa⋅s) and S9A (from 1244 to 1164 Pa⋅s). Many methods have been applied for characterizing the yield stress Conversely, the sieving process did not change the viscosity of the for- of food systems (Sun & Gunasekaran, 2009). To choose the model mulations without agar, irrespective of their protein content. that best fits our data, different mathematical equations or models (Power Law, Herschel–Bulkley, Casson, and Bingham models) were tested to select the best performer. Bingham was determined to be 3.1.2 Thixotropy the best model to fit the flow characteristics of the samples, with a high coefficient of determination (R > 0.98). The Bingham model is All formulations were studied varying the shear rate to characterize described by the equation τ = τ0 + ηρ ɣ̇, where τ (Pa) is the shear stress, the effects including SPAH and agar, and to depict the effect of sieving. τ0 (Pa) is the yield stress, ηρ (Pa⋅s) is the viscosity, and ɣ̇ (s−1 ) is the shear The results showed hysteresis loops, indicating that all formulations rate. exhibited thixotropic behaviors. S6A presented the highest yield stress among the tested formula- Flow curves obtained with controlled shear stress for all formula- tions (Table 1). This high yield can be explained by the effect of both tions, before and after sieving, are presented in Figure 2. The samples agar and SPAH in the starch internal microstructure, contributing to showed a behavior that differs by the effect of sieving, with a reduction the elasticity of the network of the potato starch puree and conse- in the shear stress, but more noticeably in the hysteresis area for for- quently generating a starch internal microstructure that was more mulations with agar with a decrease that means less energy is needed resistant to deformation in the shear stress region where the sample to destroy the internal structure of the material responsible for the is fully elastic. flow time dependence (Tárrega et al., 2004) in the samples that have The yield stress decreased for all sieved samples, showing the been previously sieved. increase in the easy-flowing of the materials after passing through a Formulation with 6 g SPAH and 0.2 g agar (S6A) exhibited the high- sieve and breaking the bonds and strengths of the structure, especially est degree of thixotropy, with the largest hysteresis area indicating for the formulations with agar. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 710 MIRAZIMI ET AL . F I G U R E 2 Rheological characterization of food formulations. Shear stress versus shear rate, each curve represents the average of three replicates per sample. (a) Thixotropy before sieving and (b) thixotropy after sieving. Note: S3 (3 g soy), S6 (6 g soy), S9 (9 g soy), S3A (3 g soy and 0.2 g agar), S6A (6 g soy and 0.2 g agar), and S9A (9 g soy and 0.2 g agar) TA B L E 1 Rotational rheological measurements, thixotropy, and yield stress, before and after sieving. The yield stress was obtained according to Bingham model η = ηρ + τ0 /ɣ̇. The numbers represent the average of three replicates per sample Yield stress Thixotropy Samples (Pa) (Pa⋅s) ηρ (Pa⋅s) τ0 (Pa) R2 Before sieving S3 638d 4246c 155c 405b 0.99 S6 757cd 5756bc 262bc 453ab 0.99 cd bc c ab S9 841 5482 164 461 0.99 b b ab ab S3A 1084 7971 386 488 0.98 S6A 1489a 15345a 549a 602a 0.98 bc bc bc ab S9A 950 6854 211 537 0.99 After sieving S3 623c 3648bc 76b 405b 0.99 bc bc b ab S6 743 3880 128 406 0.98 S9 639c 2537c 85b 409ab 0.99 b ab a a S3A 881 6414 234 456 0.98 a a a a S6A 1081 7360 315 475 0.98 S9A 707c 4888abc 123b 422ab 0.99 Note: S3 (3 g soy), S6 (6 g soy), S9 (9 g soy), S3A (3 g soy and 0.2 g agar), S6A (6 g soy and 0.2 g agar), and S9A (9 g soy and 0.2 g agar). The results with different letters in the same column are different with a significance level of p < .05. 3.1.4 Viscoelastic behavior viscoelastic properties of the food products (Hadde & Chen, 2018; Nishinari, Fang, et al., 2019; Nishinari, Turcanu, et al., 2019). As one of The shallowing process is determined by the interactions between the the requirements for dysphagia patients is safe swallowing, the charac- major molecules in thickened fluids and their effects on their exten- teristic and gel properties of starch have an important role in the final sional properties. These interactions can be elucidated by studying the product quality (Sungsinchai et al., 2019). 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License MIRAZIMI ET AL . 711 TA B L E 2 Frequency sweep rheological measurements. Storage 3.2 3DFP test and structure and correlation with modulus and loss modulus are reported at 10 Hz. The numbers rheology represent the average of three replicates per sample Samples G’ (Pa) G” (Pa) Some requirements are necessary to find out the best formulation for Before sieving any food product for 3DFP such as food type, hydrocolloids, type of S3 602e 107c printer, and so forth. Each type of food has different physical and chem- S6 850 cd 137 c ical interactions with the hydrocolloids (Pant et al., 2021). Different shapes were applied to see the printability of the formu- S9 719de 122 cd lations simply with SPAH and SPAH with agar and to test the visual S3A 1089b 185b performance when attempting complex structures as presented in a S6A 1352 226a Figure 3. All formulations were able to form stable self-supporting S9A 974bc 168b structures for simple shapes. The pentagon prism shape for all food for- After sieving mulations was able to keep the structure for more than 15 min. Honey- c c S3 599 105 comb shapes were able to form a stable self-supporting. All the print- S6 714bc 123bc ing materials could build the geometry of the design of a pentagon and S9 613 c 117 c honeycomb while displaying abilities to print snowflakes as well. The complicated mountain shape collapsed during printing in the S3A 977ab 165ab formulations fortified simply with SPAH as the material was not able to S6A 1090a 184a tolerate the load of many layers. The formulations with agar, however, S9A 529c 93c had the strength to tolerate the weight of many layers, a fact that can Note: S3 (3 g soy), S6 (6 g soy), S9 (9 g soy), S3A (3 g soy and 0.2 g agar), S6A be explained by the addition of agar which could restrain the mobility (6 g soy and 0.2 g agar), and S9A (9 g soy and 0.2 g agar). The results with of starch chains (Wu et al., 2009). different letters in the same column are different with a significance level of Some researchers (Lewis et al., 2006; Liu et al., 2018; Zhang et al., p < .05. 2015) found that printed shape retention was closely related to the G′ and τ0 of materials and to develop periodic structures through 3D printing, and also found that materials with higher G′ and τ0 showed better shape retention; the τ0 shows the minimum force necessary Viscoelastic behavior is explained by the level and nature of the for material extrusion and G′ reflect the mechanical strength of mix- leached material and the molecular interactions upon starch gran- tures, which is critical for supporting subsequently deposited layers ule disintegration in a 3D network structure (Alcázar-Alay & Meire- and maintaining printed shape. The samples with only SPAH had low les, 2015). The storage or elastic modulus G′ measures the recov- τ0 (Table 1) and G′ (Table 2), but the addition of agar led to an increase ered or accumulated energy in each deformation cycle and determines both in τ0 and G′. The formulations with only SPAH did not possess the elastic behavior of the samples. The loss or viscous modulus G″ enough mechanical strength for complex shapes with many layers; describes the loss of energy or dissipated energy in each deformation thus, the deformation and poor resolution supporting structure were cycle, which describes the viscosity behavior of the material. Table 2 observed in formulations without agar for complex printed objects shows that all formulations exhibit larger G′ than G′′, indicating the (Figure 3). The mixture with agar and SPAH had higher τ0 and G′ and presence of an internal network arrangement and a gel-like structure, was strong enough to support the deposited layers and hold the printed as happens in starch-rich preparations. structures. The storage modulus measured at 10 Hz significantly changed with the amount of SPAH included in the formulation. It increased from 602 Pa in S3 to 850 Pa in S6 but significantly decreased to 719 Pa in 3.3 Texture properties: TPA S9. A similar process occurred with G″, with an increase from 107 Pa in S3 to 137 Pa in S6 and a significant decrease to 122 Pa in S9. Formulations only with SPAH had lower hardness values than those The effects of agar on increasing the elastic and viscous moduli of that also contain agar and were not significantly different according potato puree can be seen on formulation S6A, with a G′ higher than that to the amount of SPAH (Table 3). The formulation S6A showed signif- corresponding to the other samples over all the range of frequencies icantly the highest hardness values. This was the formulation that had studied. the best 3D shape. After sieving, all formulations show weaker structures especially High adhesiveness is a very important property of semi-solid food samples with agar. Among all the formulations, S6A has the highest that needs more effort in pharyngeal swallowing in older adults (Park elastic modulus before (1352 Pa at 10 Hz) and after (1090 Pa) siev- et al., 2020). The formulations S6A and S9A had the highest values for ing and also viscous modulus before (226 Pa at 10 Hz) and after sieving adhesiveness pointing to a good performance on the design of formu- (184 Pa at 10 Hz). lations for people with dysphagia. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 712 MIRAZIMI ET AL . F I G U R E 3 3D prints. Representative image of 3D printed shape with six formulations. Note: (a) S3 (3 g soy), (b) S6 (6 g soy), (c) S9 (9 g soy), (d) S3A (3 g soy and 0.2 g agar), (e) S6A (6 g soy and 0.2 g agar), and (f) S9A (9 g soy and 0.2 g agar) TA B L E 3 The average values of Textural Profile Analysis (TPA) for six formulations from three replicates Adhesiveness Cohesiveness Gumminess Samples Hardness (N) (N⋅sec) Resilience (−) (−) (N) S3 1.01b −34.3a 0.005bc 0.007ab 0.80ab S6 1.31b −46.9b 0.006bc 0.009a 1.17ab S9 1.20 b −28.8 a 0.004 c 0.003 c 0.43b S3A 2.02ab −29.8a 0.014a 0.005bc 1.01ab S6A 5.49a −71.2c 0.013ab 0.006abc 3.54a S9A 3.31 ab −64.4 c 0.011 abc 0.006 abc 2.11ab Note: S3 (3 g soy), S6 (6 g soy), S9 (9 g soy), S3A (3 g soy and 0.2 g agar), S6A (6 g soy and 0.2 g agar), and S9A (9 g soy and 0.2 g agar). The results with different letters in the same column are different with a significance level of p < .05. Resilience is another attribute that indicates a food’s ability to resist from disintegrating into fragments during swallowing (Sharma et al., deformation, and the samples with just SPAH had lower resilience val- 2017). Formulations S6 and S9 presented the highest and lowest cohe- ues in coincidence with the worse performance on 3D printing tests siveness, respectively, among all the tested samples. and its difficulty to keep the designed shape. Gumminess is the amount of work needed to make a food sample The structural strength of internal bonds is measured as cohesive- ready to swallow. Sample S6A had significantly higher values for gum- ness, which holds the food matrix together in a bolus and prevents it miness compared to the rest. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License MIRAZIMI ET AL . 713 F I G U R E 4 International Dysphagia Diet Standardisation Initiative (2019). Testing Methods 2.0 2019: (1) Fork pressure test on soft and bite-sized 3D printed samples and (2) spoon tilt test. Note: (a) S3 (3 g soy), (b) S6 (6 g soy), (C) S9 (9 g soy), (d) S3A (3 g soy and 0.2 g agar), (E) S6A (6 g soy and 0.2 g agar), and (f) S9A (9 g soy and 0.2 g agar) Hardness, resilience, and chewiness were increased with the addi- test is required further study to accept the food as a dysphagic diet tion of agar, which could support the designed structure during the 3D food. printing process. 3.4 Fork pressure and spoon tilt test 4 DISCUSSION All the formulations could slide off the spoon on tilting and showed that The number of elderly and people with swallow difficulties is increasing they would not stick to the oral cavity. Fork pressure tests were done all over the world, so personalization diet and understanding about the with all formulations and showed the indent pattern (Figure 4). correct range of texture and rheological properties are necessary. Sev- According to these tests, all formulations terminated to be tran- eral studies show 3D printing is capable of converting mashed and not sitional foods. However, all printed structures may change meantime attractive dysphagia diets into appetizing foods with appealing appear- with water/saliva in the mouth, and the time for slide off from spoon ance (Diañez et al., 2021; Xing et al., 2022). 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 714 MIRAZIMI ET AL . The addition of SPAH and agar in the given range used in this study appearance of the food for elderly people and people with mastication had a significant effect on the rheological and textural properties. and shallowing problems. All the measured rheological parameters (viscosity, thixotropy, yield stress, and viscoelastic behavior) on the formulations without ACKNOWLEDGMENT agar significantly increased with rising the soy concentration from We want to acknowledge the help provided by Natural Machines 3% to 5%, but from 5% to 7% they had no significant differences, Iberia, S.L. company, Spain-Barcelona, allowing the use of their 3D- which can be explained by insufficient water in the formulation printer Foodini. caused by the high concentration of solids. This phenomenon has been previously reported, with a decrease in thickening for CONFLICT OF INTEREST the highest concentrations of added soy protein (Alvarez et al., The authors confirm that they have no conflict of interest to declare for 2012). this publication. The formulations with agar showed higher values on the rheological measurements compared to the ones without agar. Agar can improve ORCID mechanical strength due to the strong interaction of hydrogen bonding Jordi Saldo https://orcid.org/0000-0001-5166-6142 and the formation of hydrophobic aggregates (Wongphan & Harnkarn- sujarit, 2020). Starchy food’s texture and appearance can be improved REFERENCES by mixing starch with hydrocolloids as both share some key behavior as Alcázar-Alay, S. C., & Meireles, M. A. A. (2015). Physicochemical proper- being polysaccharide molecules (Bemiller, 2011). ties, modifications and applications of starches from different botanical The formulation with the highest values for all measured parame- sources. Food Science and Technology, 35(2), 215–236. https://doi.org/10. 1590/1678-457X.6749 ters has been S6A. This can be explained by the formation of a strongly Alvarez, M. D., Fernández, C., Olivares, M. D., & Canet, W. (2012). A rheo- interconnected network due to the effect of having both interactions, logical characterisation of mashed potatoes enriched with soy protein where a major part of the granules is strongly connected by the high isolate. Food Chemistry, 133(4), 1274–1282. https://doi.org/10.1016/j. molecular weight and length of the agar molecule (agar–starch), foodchem.2011.05.111 Aslam, M., & Vaezi, M. F. (2013). Dysphagia in the elderly. Gastroenterology (agar–SPAH), and (SPAH–starch) interactions and the formation of and Hepatology, 9(12), 784–795. https://doi.org/10.1159/000072614 (agar–agar) gel-like interactions. These interactions would result in Baum, J. I., & Wolfe, R. R. (2015). The link between dietary protein intake, a more elastic, structured, and gel-like microstructure than in the skeletal muscle function and health in older adults. Healthcare, 3(3), 529– case of the samples with SPAH alone. Our finding highlights that the 543. https://doi.org/10.3390/healthcare3030529 physiochemical properties for the samples with agar changed by the Bemiller, J. N. (2011). Pasting, paste, and gel properties of starch– hydrocolloid combinations. Carbohydrate Polymers, 86(2), 386–423. effect of sieving as agar could build different bonds with starch and https://doi.org/10.1016/j.carbpol.2011.05.064 proteins. The addition of agar improved the mechanical properties, but Bomze, L., Dehom, S., Lao, W. P., Thompson, J., Lee, N., Cragoe, A., Luceno, after passing through the sieve, physiochemical properties decreased C., & Crawley, B. (2021). Comorbid dysphagia and malnutrition in elderly by breaking hydrogen bonds that give strength to the 3D gel network. hospitalized patients. Laryngoscope, 131(11), 2441–2447. https://doi. org/10.1002/lary.29329 Passing the samples through the sieve before printing is a common Cichero, J. A. Y., Lam, P., Steele, C. M., Hanson, B., Chen, J., Dantas, R. O., practice in 3D printing, recommended for avoiding blocking the nozzles Duivestein, J., Kayashita, J., Lecko, C., Murray, J., Pillay, M., Riquelme, L., of the printer (Huang et al., 2020; Kim et al., 2018; Pant et al., 2021). & Stanschus, S. (2017). Development of international terminology and Our results showed that sieving process has a significant effect on the definitions for texture-modified foods and thickened fluids used in dys- phagia management: The IDDSI framework. Dysphagia, 32(2), 293–314. rheological properties of samples containing hydrocolloids, and it is https://doi.org/10.1007/s00455-016-9758-y important to consider this effect for the food products addressed to an Diañez, I., Gallegos, C., Brito-de la Fuente, E., Martínez, I., Valencia, C., aging population and people with dysphagia. Sánchez, M. C., & Franco, J. M. (2021). Implementation of a novel contin- SPAH addition increased the viscosity and mechanical strength of uous solid/liquid mixing accessory for 3D printing of dysphagia-oriented thickened fluids. Food Hydrocolloids, 120(April), 106900. https://doi.org/ all food formulations. The resultant self-supporting capacity of 3D- 10.1016/j.foodhyd.2021.106900 printed samples was very good for simple shapes, and after adding Gallegos, C., Quinchia, L., Ascanio, G., & Salinas-vázquez, M. (2012). Rheol- agar, self-supporting capacity of 3D-printed samples increased and was ogy and dysphagia: An overview. Annual Transactions of the Nordic Rheol- suitable for printing complex shapes because of increasing viscosity ogy Society, 20, 3–10. Godoi, F. C., Prakash, S., & Bhandari, B. R. (2016). 3D printing technologies and viscoelastic properties. Formulation S6A was available to perfectly applied for food design: Status and prospects. Journal of Food Engineering, support the extruded materials for a complex shape, and the layers 179, 44–54. https://doi.org/10.1016/j.jfoodeng.2016.01.025 remain strong during the printing process. Hadde, E. K., & Chen, J. (2018). Shear and extensional rheological characteri- All samples were classified as level 4 puree dysphagia diet within the zation of thickened fluid for dysphagia management. Journal of Food Engi- IDDSI framework. neering, 245, 18–23. https://doi.org/10.1016/j.jfoodeng.2018.10.007 Hadde, E. K., & Chen, J. (2021). Food texture and texture modification for Generally, formulation S6A (soy 6 g and agar 0.2 g) showed fine 3D dysphagia management. J Texture Stud, 52, 538–539. https://doi.org/10. printability with an appealing appearance and were acceptable for dys- 1111/jtxs.12650 phagia diets. This study provides the development of dysphagia diets by Hagen, M. K., Lehenbauer-Lüdke, A. R., Paludo, A. C., Schenkel, P., Gonçalves, emerging 3D printing technology, which would offer a more appealing L., Fernandes, T. G., Caron, R., Llesuy, S., Mill, J. G., & Belló-Klein, A. 26438429, 2022, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/fft2.149 by Readcube (Labtiva Inc.), Wiley Online Library on [16/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License MIRAZIMI ET AL . 715 (2009). Diet with isolated soy protein reduces oxidative stress and pre- Pérez, B., Nykvist, H., Brøgger, A. F., Larsen, M. B., & Falkeborg, M. F. (2019). serves ventricular function in rats with myocardial infarction. Nutrition, Impact of macronutrients printability and 3D-printer parameters on 3D- Metabolism and Cardiovascular Diseases, 19(2), 91–97. https://doi.org/10. food printing: A review. Food Chemistry, 287, 249–257. https://doi.org/ 1016/j.numecd.2008.03.001 10.1016/J.FOODCHEM.2019.02.090 Hemar, Y., Hall, C. E., Munro, P. A., & Singh, H. (2002). Small and large defor- Quan, H., Zhang, T., Xu, H., Luo, S., Nie, J., & Zhu, X. (2020). Photo-curing 3D mation rheology and microstructure of k-carrageenan gels containing printing technique and its challenges. Bioactive Materials, 5(1), 110–115. commercial milk protein products. International Dairy Journal, 12, 371– https://doi.org/10.1016/j.bioactmat.2019.12.003 381. https://doi.org/10.1016/S0958-6946(02)00032-8 Quinchia, L. A., Valencia, C., Partal, P., Franco, J. M., Brito-De La Fuente, E., & Huang, M.-S., Zhang, M., & Guo, C.-F. (2020). 3D printability of brown rice Gallegos, C. (2011). Linear and non-linear viscoelasticity of puddings for gel modified by some food hydrocolloids. Journal of Food Processing and nutritional management of dysphagia. Food Hydrocolloids, 25(4), 586–– Preservation, 44(7), 1–9. https://doi.org/10.1111/jfpp.14502 593. https://doi.org/10.1016/j.foodhyd.2010.07.006 Hudson, H. M., Daubert, C. R., & Mills, R. H. (2000). The interdependency of Sharma, M., Kristo, E., Corredig, M., & Duizer, L. (2017). Food hydrocolloids protein-energy malnutrition, aging, and dysphagia. Dysphagia, 15(1), 31– effect of hydrocolloid type on texture of pureed carrots: Rheological and 38. https://doi.org/10.1007/s004559910007 sensory measures. Food Hydrocolloids, 63, 478–487. https://doi.org/10. Kim, H. W., Lee, J. H., Park, S. M., Lee, M. H., Lee, I. W., Doh, H. S., 1016/j.foodhyd.2016.09.040 & Park, H. J. (2018). Effect of hydrocolloids on rheological proper- Steele, C. M., Molfenter, S. M., Péladeau-Pigeon, M., Polacco, R. C., & Yee, ties and printability of vegetable inks for 3D food printing. Journal of C. (2014). Variations in tongue-palate swallowing pressures when swal- Food Science, 83(12), 2923–2932. https://doi.org/10.1111/1750-3841. lowing xanthan gum-thickened liquids. Dysphagia, 29(6), 678–684. https: 14391 //doi.org/10.1007/s00455-014-9561-6 Kinsella, J. E., & Whitehead, D. M. (1989). Proteins in whey: Chemical, phys- Sun, A., & Gunasekaran, S. (2009). Yield stress in foods: Measurements and ical, and functional properties. Advances in Food and Nutrition Research, applications. International Journal of Food Properties, 12(1), 70–101. https: 33(C), 343–438. https://doi.org/10.1016/S1043-4526(08)60130- //doi.org/10.1080/10942910802308502 8 Sungsinchai, S., Niamnuy, C., Wattanapan, P., Charoenchaitrakool, M., & Lewis, J. A., Smay, J. E., Stuecker, J., & Cesarano, J. (2006). Direct ink writing Devahastin, S. (2019). Texture modification technologies and their of three-dimensional ceramic structures. Journal of the American Ceramic opportunities for the production of dysphagia foods: A review. Compre- Society, 89(12), 3599–3609. https://doi.org/10.1111/j.1551-2916.2006. hensive Reviews in Food Science and Food Safety, 18(6), 1898–1912. https: 01382.x //doi.org/10.1111/1541-4337.12495 Lille, M., Nurmela, A., Nordlund, E., Metsä-Kortelainen, S., & Sozer, N. (2018). Sura, L., Madhavan, A., Carnaby, G., & Crary, M. A. (2012). Dysphagia in Applicability of protein and fiber-rich food materials in extrusion-based the elderly: Management and nutritional considerations. Clinical Inter- 3D printing. Journal of Food Engineering, 220, 20–27. https://doi.org/10. ventions in Aging, 7, 287–298. https://doi.org/10.2147/CIA.S23404 1016/j.jfoodeng.2017.04.034 Tabilo-Munizaga, G., & Barbosa-Cánovas, G. V. (2005). Rheology for the food Liu, Z., Zhang, M., Bhandari, B., & Yang, C. (2018). Impact of rheological industry. Journal of Food Engineering, 67(1–2), 147–156. https://doi.org/ properties of mashed potatoes on 3D printing. Journal of Food Engi- 10.1016/j.jfoodeng.2004.05.062 neering, 220, 76–82. https://doi.org/10.1016/J.JFOODENG.2017.04. Tárrega, A., Durán, L., & Costell, E. (2004). Flow behaviour of semi-solid 017 dairy desserts. Effect of temperature. International Dairy Journal, 14(4), Nestel, P. (2002). Role of soy protein in cholesterol-lowering how good is it? 345–353. https://doi.org/10.1016/J.IDAIRYJ.2003.12.004 Arteriosclerosis, Thrombosis, and Vascular Biology, 22, 1743–1744. https: Wongphan, P., & Harnkarnsujarit, N. (2020). Characterization of starch, agar //doi.org/10.1161/01.ATV.0000035520.25551.97 and maltodextrin blends for controlled dissolution of edible films. Inter- Nishinari, K., Fang, Y., & Rosenthal, A. (2019). Human oral processing and national Journal of Biological Macromolecules, 156, 80–93. https://doi.org/ texture profile analysis parameters: Bridging the gap between the sen- 10.1016/J.IJBIOMAC.2020.04.056 sory evaluation and the instrumental measurements. Journal of Texture Wu, Y., Geng, F., Chang, P. R., Yu, J., & Ma, X. (2009). Effect of agar on Studies, 50(5), 369–380. https://doi.org/10.1111/jtxs.12404 the microstructure and performance of potato starch film. Carbohy- Nishinari, K., Takemasa, M., Brenner, T., Su, L., Fang, Y., Hirashima, M., drate Polymers, 76(2), 299–304. https://doi.org/10.1016/j.carbpol.2008. Yoshimura, M., Nitta, Y., Moritaka, H., Tomczynska-Mleko, M., Mleko, S., 10.031 & Michiwaki, Y. (2016). The food colloid principle in the design of elderly Xing, X., Chitrakar, B., Hati, S., Xie, S., Li, H., Li, C., Liu, Z., & Mo, H. (2022). food. Journal of Texture Studies, 47(4), 284–312. https://doi.org/10.1111/ Development of black fungus-based 3D printed foods as dysphagia diet: jtxs.12201 Effect of gums incorporation. Food Hydrocolloids, 123(September 2021), Nishinari, K., Turcanu, M., Nakauma, M., & Fang, Y. (2019). Role of fluid cohe- 107173. https://doi.org/10.1016/j.foodhyd.2021.107173 siveness in safe swallowing. NPJ Science of Food, 3(1), 5. https://doi.org/ Zhang, M., Vora, A., Han, W., Wojtecki, R. J., Maune, H., Le, A. B. A., 10.1038/s41538-019-0038-8 Thompson, L. E., Mcclelland, G. M., Ribet, F., Engler, A. C., & Nelson, A. Nowson, C., & O’Connell, S. (2015). Protein requirements and recommen- (2015). Dual-responsive hydrogels for direct-write 3D printing. Macro- dations for older people: A review. Nutrients, 7(8), 6874–6899. https: molecules, 48(18), 6482–6488. https://doi.org/10.1021/acs.macromol. //doi.org/10.3390/nu7085311 5b01550 Pant, A., Yilin, A., Karyappa, R., Pau, C., An, J., Hashimoto, M., Tan, U., Wong, G., Kai, C., & Zhang, Y. (2021). Food hydrocolloids 3D food printing of fresh vegetables using food hydrocolloids for dysphagic patients. Food Hydrocolloids, 114, 106546. https://doi.org/10.1016/j. How to cite this article: Mirazimi, F., Saldo, J., Sepulcre, F., foodhyd.2020.106546 Gràcia, A., & Pujola, M. (2022). Enriched puree potato with soy Park, J. W., Lee, S., Yoo, B., & Nam, K. (2020). Effects of texture properties protein for dysphagia patients by using 3D printing. Food of semi-solid food on the sensory test for pharyngeal swallowing effort in the older adults. BMC Geriatrics, 20(1), 1–5. https://doi.org/10.1186/ Frontiers, 3, 706–715. https://doi.org/10.1002/fft2.149 s12877-020-01890-4