Study and characterization of microstructural and physio-chemical properties of potato products for 3d food printing
- Autores: Iman Dankar
- Directores de la Tesis: Fawaz El Omar (dir. tes.), Montserrat Pujolà Cunill (dir. tes.), Francesc Sepulcre Sánchez (dir. tes.), Amira Haddarah (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Olga Martín Belloso (presid.), Joaquím Minguella Canela (secret.), J. Saldo (voc.)
- Programa de doctorado: Programa de Doctorado en Tecnología Agroalimentaria y Biotecnología por la Universidad Politécnica de Catalunya
- Materias:
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- Resumen
3D food printing is a precise digitalized process that is based on monitoring the characteristics of the printed substrate in accordance with the process parameters. In this thesis mashed potatoes were first mixed with different food additives (agar, alginate, lecithin and glycerol) at different concentrations (0.5, 1 and 1.5%) in order to compare how each additive would affect the yield stress, viscosity, thixotropy, mechanical properties as well as the internal microstructure of potato puree. It was observed that agar and alginate enhanced the rheological and mechanical properties of puree by forming a stronger internetwork structure thus providing better printing with many build up shapes and that are stable post deposition.On the other hand, lecithin and glycerol decreases the rheological and mechanical properties of puree and thus although the extrusion was smooth, end printed products were unstable and collapsed instantly. additionally, to inspect the reason behind obtaining those rheological and mechanical values, a further investigation at the molecular level (applying FTIR and XRD) was done. It was revealed that additives such as glycerol and lecithin can penetrate the starch granules and induce a more intense effect on the structure as their respective concentrations increase by either suppressing (ex, glycerol) or enhancing (ex lecithin) the starch structure. In contrast, long polymeric molecules such as agar and alginate interact partially via the surface of the starch granules modifying partially the conformation of starch structure, which confirms the previous deductions from the rheological properties part. Furthermore, FTIR spectra showed that the skeleton formed by the amylose/amylopectin is somehow hidden in the dehydrated potato flakes, but was covered almost completely upon the addition of water such as to complement that of an original raw potato FTIR spectra, proving that water molecules have a central role in the maintenance of the starch structure conformation. To verify this hypothesis, task 4 was developed in order to make sure after what time of water reduction is the starch conformation altered (using this time potato tubers) and to identify whether the starch structure is modified more by the effect of the water removal or the heat treatment (microwaved and boiling). Findings showed that microwaved (MP) and boiled (BP) potato were more susceptible for water evaporation by freeze drying expressed via the following microstructural changes only after 6 hours of lyophilization; 1- obtaining an IR spectrum with much lower intensities (dried spectrum) compared to the initial spectrum, 2- undergoing a major transformation from gelatinized swollen starch to some recoiling towards a dried starch granule (SEM figures), 3- exhibiting an increase in the intensity of their respective XRD patterns. Moreover, RP took around 24 hours to reach a dried stage that was characterized by some ruptured granules embedded within leached starch matrix, an FTIR spectra that resembles in intensity that of BP and MP, possessing two peaks at 485 cm-1 and 620 cm-1 and that were assigned as a distinctive for a dried potato starch spectra. Concluding that water removal sublimes the effect of the heat processing treatment, being the major contributor in the modifications of the starch structure. MP and BP were then used as basic samples for 3D printing trials while adding to each different food substrates at 1% concentration with respect to the weight (butter, olive oil, alginate and agar) except for carrots which were added at a ratio of 1/3 of the respective potato weight. All MP samples showed higher rheological and mechanical properties that lead to more stable printed products. Best printability was accounted with butter insertion which elevated the yield stress and thixotropy, thus increasing structural integrity and maintianing higher retaining shape property while preserving smooth extrusion and creamy surface structure
