Osorio, Samara Dias

Santana, Ruth Marlene Campomanes

English

Lume 5.8

INFLUENCE OF GELATIN CONTENT IN BLENDS WITH STARCHEXTRACTED FROM POTATO SKINSSamara D. Osorio¹*, Ruth M. C. Santana¹1 -  Department of Materials, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazilsamara.osorio@ufrgs.brAbstract - Biodegradable materials from a natural source, such as polymer blends, are increasingly gaining popularityin research as an alternative to synthetic polymers, which are among the leading environmental problems of our time.Renewable raw materials such as starch and gelatin are attractive, capable of forming films, in addition to beingeconomically viable. Even the potato skins residue has the potential to be used as one of the components of the blend(starch). Thus, blends of starch (A) extracted from potato skins, and different proportions (20, 50, and 80 %) of gelatin(G) were produced in this work. The influence of varying these proportions on the blends G/A were characterized bycontact angle, moisture, and scanning electron microscopy analysis. The results indicated that different gelatin ratiosinterfered in the mixing behavior. Notably, 50:50 blends showed to be more attractive, having hydrophobiccharacteristics, and being more resistant to moisture, although immiscible.Keywords: Blend, starch, potato, gelatin.IntroductionPlastic materials originating from fossils are still widely used today, mainly due to theirversatility and low cost [1]. However, these materials are considered an environmental problemsince they have high molecular weight characteristics, strong intermolecular bonds, and chemicalinertness, which may take more than 100 years to degrade [2]. Given this, alternative materials havebeen sought in which polymer blends gain visibility [3].Among the new materials studied in the literature, blends of agricultural origin have stoodout due to their availability, low toxicity, biodegradability, filmogenic characteristics, and relativelylow cost [4]. Thus, gelatin and starch blends have attracted researchers’ attention recently [3,5,6-10]. These mixtures have advantages over the individual components, as they can combine thebenefits of each one, providing better mechanical, optical, sensory, barrier, and solubility properties[11]. Nevertheless, the final quality of a blend basically depends on the raw materials used and theirproportions and interactions, the formation process, and the desired application [6,9].Potato shows itself as a relevant starch, the fourth food source of humanity [12], withexcellent yield capacity and fundamental nutritional properties [13]. In Brazil, potatoes are plantedand harvested throughout the year and, therefore, during harvest times, the total amount of potatoesconsumed can be smaller than that produced, which ends up generating agricultural waste. Thiswaste is often mistakenly and even unnecessary discarded since its chemical formation presentsitself as a potential raw material for manufacturing products with higher added value [14].Proceedings of the 16th Brazilian Polymer Conference (16° CBPOL), October 24-28, 2021, Ouro Preto-MG, Brazil 1234Gelatin is another interesting raw material that has been widely explored in the literature,predominantly comprising the food and pharmaceutical industry, due to its ability to form films [3].It also attracts attention due to its ability to combine with other biopolymers, such as starch [15].Therefore, the objective of this work was to evaluate the influence of adding different proportionsof gelatin in blends with starch extracted from potato skins when subjected to contact angle,moisture, and scanning electron microscopy (SEM) analyses.ExperimentalTo produce the blends, commercial bovine gelatin, brand Dr. Oetker, starch extracted frompotato skin (Solanum tuberosum), glycerol plasticizer and water (as solvent) were used. First, thepotato peels were washed in running water and solution of sodium hypochlorite (NaClO) at a 20mg/L concentration for 10 min. Then, based on the methodology proposed by Fernandes [16] andMahecha [17], a process of mechanical grinding, filtration, and decantation was carried out toextract the starch. The extracted (hydrated) stayed in a controlled temperature environment of 60 ºCfor 24 h for water evaporation, leaving only the starch.The Casting methodology was used to produce blends, in which the filmogenic solutionswere prepared individually. The gelatin (G) solution was obtained by hydrating 10 g of gelatin in100 mL of distilled water for 1 h. The starch (A) solution was prepared using 3 g of starch in 100mL of distilled water. These solutions were heated at 85 °C for 10 min for gelatin and for 3 min forstarch, followed by the addition of 20 % glycerol. It was added concerning the dry mass of thecomponents under magnetic stirring until homogenization. Therefore, the volumetric mixture ofthese solutions was carried out, that is, the G/A blend, in proportions of 20:80, 50:50 and 80:20.The blends were homogenized for 15 min at 85 ºC. Subsequently, 30 mL aliquots of the blend weredistributed in 25 cm x 18 cm plates and placed in a laboratory oven at 30 °C for 24 h to form thefilms, and then placed in a desiccator for another 24 h. After this period, the films were removedfrom the plates and submitted to the proposed analyses in triplicate.Film thicknessThree measurements were performed at different and random points of the films using amicrometer, Mainard brand, and model M-73010.Contact angleA camera with focus adjustment and light source was used to project the images, followingan adaptation of the ASTM D 7334-08 standard [18], and assisted the contact angle measurement.Samples with 5 cm x 2.5 cm were previously stored in a desiccator 1 h before testing. Then, thefilms were positioned 3 mm away from the syringe needle tip containing deionized water. On eachsample, ten drops were dripped, which were photographed 3 seconds after application to assess thematerial’s stability. The measurements were performed in triplicate, using the Surftens software.MoistureA saline solution of sodium chloride (NaCl) with a relative humidity of 75 %, was used todetermine the moisture of the blends, following the ASTM E 104-02 [18]. Samples of 2 cm x 2.5cm, in triplicate, were placed in the laboratory oven at 60 °C for 1 h and then in the desiccator for24 h. After the first weighing, the samples of blends were placed in containers with the salinesolution. These containers were kept in the laboratory oven at 30 °C throughout the test. The samplemass was monitored for a total periodo of 99 h, and the moisture calculation was made based on themass differences.Scanning Electron Microscopy (SEM)Proceedings of the 16th Brazilian Polymer Conference (16° CBPOL), October 24-28, 2021, Ouro Preto-MG, Brazil 1235The evaluation of the morphology of the blends was performed using a scanning electronmicroscope, model Jeol JSM-6060. The samples were previously metalized in gold.Results and DiscussionThickness and contact angleTable 1 shows the average thickness of the plasticized gelatin/starch blends and the contactangle values obtained.Table 1. Average thickness and contact angle of gelatin/starch blendsProportion G/A Average blend thickness (µm) Contact angle (º)20:80 57 ± 6 81.95 ± 2.8350:50 60 ± 5 91.12 ± 1.2780:20 62 ± 9 84.35 ± 2.51When verifying the thickness values, it was possible to notice that they were close,suggesting that the amount of protein added to the blend was not enough to cause an increase inthickness. Similar results were found by Davanço, Tanada-Palmu, and Grosso [20] and Fakhouri etal. [5] in blends of corn starch and gelatin. In this context, Acosta et al. [9] analyzed the variation inthickness of their cassava starch and gelatin blends, in 1 and 5 weeks of storage, in which theyfound that there was no significant variation in thickness, remaining between 60 and 76 µm, valuessimilar to those obtained in this research.In general, it was observed that the different proportions of gelatin added to the blendinfluenced the contact angle, making them less hydrophilic, as also mentioned by Zhang et al. [7]and Nunes [21]. This result can be associated with the better barrier properties of the protein.Furthermore, according to Silva et al. [22], gelatin typically improves starch-based materials’performance. However, it can be noted that the effect of the gelatin increment was not proportionalto the hydrophobicity, since at the 80:20 ratio the blend became hydrophilic again, as the angle wasless than 90º [23]. This behavior is possibly related to the type of interactions carried out betweenthe blend components [9].MoistureFig. 1 illustrates the mass gain in the blends as a function of time. It can be seen that the50:50 blend remained more stable and with lower mass gain, which indicates greater resistance tomoisture compared to the other gelatin/starch ratios. However, the behavior of the blends whensubjected to a relative humidity of 75 % did not follow a proportion relationship when adding moregelatin, similar to what was observed for the contact angle values. Thus, making an associationbetween the obtained results, it was noticed that the contact angle values corroborated with themoisture results.A more significant mass gain was expected at higher proportions of starch, resulting fromthe higher number of hydroxyl groups available in starch [11], although this occurred in the 20:80blend. However, the efficiency of blends depends on the proportions of raw materials and theirinteractions [9]. Therefore, a possible explanation for the most attractive results found for the 50:50blends is based on the type of connections made between the blend components.Gelatin and polysaccharides can interact attractively, forming hydrogen bonds. Ingelatin/starch blends, these hydrogen bonds can occur between the hydroxyls of the starch and theamino and carboxyl groups of the constituent amino acids of the gelatin. And, therefore, polymermatrix cohesion and water sensitivity can be improved [10]. Furthermore, according to Ye [24], theProceedings of the 16th Brazilian Polymer Conference (16° CBPOL), October 24-28, 2021, Ouro Preto-MG, Brazil 1236excess of one of the polymers leads to exceeding amounts of charges in the system, harming theformation of the blend.Furthermore, it is important to highlight that both raw materials and glycerol used in theproduction of blends are hygroscopic: a characteristic that contributes to the sensitivity to moisture[3], and therefore, a certain sensitivity to water was already expected.Figure 1. Moisture of gelatin/starch blends as a function of timeScanning Electron Microscopy (SEM)Fig. 2 shows SEM images of blends in different gelatin/starch ratios. The presence of smallprotuberances can be verified as starch is added. It suggests that gelatin and starch form two distinctphases and, therefore, compatible blends, although immiscible [7-9].Acosta et al. [9] also obtained heterogeneous structures in starch and gelatin blends, in theproportions 25:75 and 50:50. According to Acosta et al. [9], despite the raw materials beingmacroscopically compatible, due to their similar hydrophilic character, there was a separation intotwo phases, one rich in starch and the other rich in gelatin. According to Zhang et al. [7] and Liu etal. [8], often, gelatin is presented as a continuous phase and starch as a dispersed phase, whichapparently happened in the present work. Furthermore, according to Liu et al. [8], this phasedifference may indicate that gelatin and starch shrinkage rates were different during drying or thatthere was an absence of strong interactions between starch and gelatin.It is worth remembering that the plates used as a mold are made of polystyrene, andtherefore they end up scratching easily, as shown in Fig. 2.Proceedings of the 16th Brazilian Polymer Conference (16° CBPOL), October 24-28, 2021, Ouro Preto-MG, Brazil 1237Figure 2. SEM images of different G/A ratiosConclusionsBased on the results obtained, it was found that increasing the gelatin proportions often ledto the improvement of the properties of starch blends. Additionally, the 50:50 G/A blend showedless moisture absorption, indicating that it is less hygroscopic, confirmed by the higher contactangle.AcknowledgementsI would like to thank the Laboratory of Polymeric Materials (LAPOL) and the FederalUniversity of Rio Grande do Sul (UFRGS) for the infrastructure and the CNPq/Universal andFAPERGS/PqG projects for the financial support for this work.References1. G. Rocha et al. Polímeros, v. 24, n. 5, p. 587–595, 2014.2. Q. Wu; L. Zhang. Industrial & Engineering Chemistry Research, v. 40, p. 1879–1883, 2001.3. C. Shi; F. Tao; Y. Cui. International Journal of Biological Macromolecules, v. 109, p. 863-871,2018.4. S. S. Farias et al. Geonorte, v.7, n. 26, p. 61-77, 2016.5. F. M. Fakhouri et al. Carbohydrate Polymers, v. 95, p. 681–689, 2013.6. A. A. Al Hassan;  M. H. Norziah. Food Hydrocolloids, v. 26, n. 1, p. 108-117, 2012.7. N. Zhang et al. Carbohydrate Polymers, v. 92, p. 455– 461, 2013.8. X. Liu et al. Chinese Journal of Polymer Science, v. 32, n. 1, p. 108-114, 2014.9. S. Acosta et al. Food Hydrocolloids, v. 49, p. 135-143, 2015.10. W. Tongdeesoontorn et al. International Journal of Polymeric Materials, v. 61, p. 778-792, 2012.11. D. M. Almeida et al. Polímeros, v. 23, n. 4, p. 538-546, 2013.12. A. C. Ávila et al. Horticultura Brasileira, v. 27, n. 4, 2009.13. D. A. Quadros et al. Ciência e Tecnologia de Alimentos, p. 316-323, 2009.14. E. Dinand; H. Chanzy; M. R. Vignon. Cellulose, v. 3, p. 183–188, 1996.15. P. Sobral et al. Food Engineering: Integrated Approaches, p. 193-223, 2008.16. A. F. Fernandes. Dissertação de Mestrado, Universidade Federal de Lavras, 2006.17. M. M. A. Mahecha. Dissertação de Mestrado, Universidade Estadual de Campinas, 2009.18. American Society for Testing Materials. ASTM D77334-08 Standard Practice for SurfaceWettability of Coatings, Substrates and Pigments by Advancing Contact Angle Measurement, 3 p.,Reapproved 2013.19. American Society for Testing Materials. ASTM E104-02 Standard Practice for MaintainingConstant Relative Humidity by Means of Aqueous Solutions, 5 p., 2002.20. T. Davanço; P. Tanada-Palmu; C. Grosso. Ciência e Tecnologia de Alimentos, v. 27, n. 2, p.408-416, 2007.21. Y. L. Nunes. Dissertação de Mestrado, Universidade Federal do Rio Grande do Norte, 2014.22. O. A. Silva et al. International Journal of Biological Macromolecules, v. 128, p. 290–296, 2019.23. P. V. P. Huillca. Dissertação de Mestrado, Universidade de São Paulo, 2015.24. A. Ye. International Journal of Food Science and Technology, v. 43, p. 406-415, 2008.Proceedings of the 16th Brazilian Polymer Conference (16° CBPOL), October 24-28, 2021, Ouro Preto-MG, Brazil 1238

Influence of gelatin content in blends with starch extracted from potato skins

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Influence of gelatin content in blends with starch extracted from potato skins

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Lume 5.8