Starch and Flour Characterization of Indigenous Ethiopian Potato (Plectranthus Edulis) and Development of Gluten Free Functional Foodd
| dc.contributor.advisor | Shimelis Admassu (Prof.) | |
| dc.contributor.author | Misikir Milkias | |
| dc.date.accessioned | 2025-04-25T08:25:56Z | |
| dc.date.available | 2025-04-25T08:25:56Z | |
| dc.date.issued | 2025-01 | |
| dc.description.abstract | This research aimed to explore the potential of Ethiopian potato (Plectranthus edulis) starch and flour, focusing on their physicochemical, structural, and functional properties. It also aimed to develop gluten-free functional food products and assess their quality for broader industrial applications. The study investigated multiple aspects, including starch isolation, flour processing, modification techniques, and the development of nutrient-dense, gluten-free noodles suitable for celiac patients. The findings provide critical insights into optimizing starch extraction, modification, and usage in advanced food processing and product development. The physicochemical, functional, and structural properties of starches isolated from two Ethiopian potato ecotypes (Chanqua and Loffo) using three different methods—distilled water (DW), sodium metabisulfite (SMS), and sodium chloride (NaCl)—were assessed. The study revealed significant differences in starch yield, with Chanqua yielding the lowest starch using DW (97.4%) and Loffo yielding the highest using SMS (99.3%). In terms of color, Loffo starches exhibited higher lightness (L*) and whiteness values, with NaCl and SMS isolation yielding superior results. Proximate composition, including moisture, protein, ash, fat, crude fiber, and carbohydrate content, showed variation across the ecotypes and isolation methods. Structural analysis using X-ray diffraction (XRD) revealed B-type diffraction patterns, while FTIR analysis indicated structural changes depending on both ecotype and isolation method. SMS was found to be the most effective isolation method for acquiring high-quality starch, particularly for the Loffo ecotype, with higher crystallinity and better functional properties. The next phase of the study focused on the effects of isolation media on starch granule morphology, powder flow properties, and functional characteristics such as pasting and thermal properties. Scanning Electron Microscopy (SEM) revealed that starch granules were predominantly spherical and elliptical, with no significant differences across isolation methods. Flow properties varied significantly, with porosity ranging from 27.16% to 40.72%, Hausner’s ratio from 1.04 to 1.20, and the angle of repose from 23.00° to 36.33°. Sodium chloride (CNaCl) had the highest peak viscosity (8979.02 mPa.s) and final viscosity (5936.03 mPa.s), making it superior for thickening applications. Thermal properties were also affected by the isolation methods, with gelatinization onset (To) ranging from 65.20°C to 68.80°C and conclusion (Tc) temperatures between 80.06°C and 84.14°C. Sodium metabisulfite (SMS) isolation produced starches with better flowability, thermal stability, and overall gelling potential, suggesting its suitability for both food and industrial applications. A comparison of Ethiopian potato flour from Chanqua and Loffo varieties with wheat flour (WF) followed, examining the effects of drying methods—oven drying and sun drying—on their physicochemical, structural, and functional properties. Moisture content (MC) ranged from 5.72% for oven-dried Chanqua Ethiopian potato flour (OD-CEPF) to 7.53% for sun-dried Loffo Ethiopian potato flour (SD-LEPF). LEPF demonstrated superior flow properties, with a lower Hausner ratio (1.16) and Carr’s index (CI) (14.51%), compared to CEPF. Significant differences were found in water absorption capacity (WAC), oil absorption capacity (OAC), and swelling power (SP), with LEPF outperforming CEPF in all aspects. Oven drying enhanced the physicochemical properties of flour, with XRD analysis confirming a B-type diffraction pattern and FTIR showing significant structural differences. These findings suggest that LEPF, particularly when oven-dried, has great potential for food applications due to its superior functional properties compared to wheat flour. The research also addressed the knowledge gap regarding moisture sorption isotherms and rheological properties of Ethiopian potato starch and flour. Sorption isotherms were determined at 20°C, with equilibrium moisture content (EMC) plotted against water activity (aw). The modified GAB and BET models best described the sorption behavior, with higher monolayer moisture content observed in flour due to its higher protein and fiber content. Rheological analysis revealed pseudoplastic behavior for both starch and flour, with flow index values (n) below 1. The Power-law model provided the best fit for starch, while the Prandtl-Eyring model was most suitable for flour. Dynamic frequency sweep tests indicated higher storage modulus (G') than loss modulus (G''), implying elastic dominance. Complex viscosity values were 289.92 Pa.s for starch and 346.24 Pa.s for flour, with lower tan δ values in starch indicating a stronger elastic response. These findings provide valuable insights for food processing and storage, particularly in the handling of Ethiopian potato starch and flour. The effects of heat moisture treatment (HMT) on the physicochemical, morphological, and functional properties of Ethiopian potato starch and flour were also studied. HMT significantly affected the color of both starch and flour, with a reduction in lightness (L*) values due to Maillard reactions. The amylose content increased from 23.02% in untreated starch to 23.95% in HMT-treated starch (HMTS-30), while crystallinity was reduced by 1.99% for starch and 2.62% for flour. FTIR spectroscopy confirmed the retention of structural integrity after HMT, while pasting properties showed reduced viscosity, with peak viscosity declining from 8346.15 mPa.s in native starch to 3950.79 mPa.s in HMTS-30. Thermal properties were similarly affected, with higher gelatinization temperatures and stability noted in HMT-treated samples. These findings highlight the potential of HMT-modified starch and flour for industrial applications, particularly where resistant starch with enhanced stability is required. Lastly, gluten-free noodles were developed using Ethiopian potato starch, resistant starch, and flour, fortified with egg white protein (EWP) and carboxymethyl cellulose (CMC). Noodles made from starch-based formulations exhibited better cooking properties, with swelling index (SI) values ranging from 2.31 to 2.79 and lower cooking loss (CL) compared to flour-based noodles, which had SI values of 1.63 to 1.94. Protein content ranged from 12.46% to 15.17% in flour-based noodles, while starch-based noodles had lower protein content. Texture profile analysis revealed significant differences in firmness, with higher values correlating to better sensory acceptance. Sensory evaluations showed favorable attributes for both flour and starch-based noodles, with hedonic scores exceeding six on a nine-point scale. These findings suggest that Ethiopian potato starch and flour, particularly when fortified with resistant starch and EWP, can be used to produce gluten-free noodles with improved texture, nutritional quality, and consumer acceptability. In conclusion, this study demonstrates the versatility of Ethiopian potato starch and flour, highlighting their potential for use in various food and industrial applications. The research provides comprehensive data on starch isolation, modification, and flour processing, paving the way for the development of functional food products, such as gluten-free noodles, that meet the growing demand for healthier and alternative food products. | |
| dc.identifier.uri | https://etd.aau.edu.et/handle/123456789/5366 | |
| dc.language.iso | en_US | |
| dc.publisher | Addis Ababa University | |
| dc.subject | Ethiopian potato | |
| dc.subject | starch | |
| dc.subject | isolation methods | |
| dc.subject | physico-chemical properties | |
| dc.subject | functional properties | |
| dc.subject | Ethiopian potato flour Morphological properties FTIR analysis Structural properties | |
| dc.title | Starch and Flour Characterization of Indigenous Ethiopian Potato (Plectranthus Edulis) and Development of Gluten Free Functional Foodd | |
| dc.type | Dissertation |