Shimelis Admassu (Prof.)Yohannes Toles2024-07-312024-07-312024-06https://etd.aau.edu.et/handle/123456789/3316Anchote (Coccinia abyssinica (Lam.) Cogn) is an underutilized root and tuber crop indigenous to Ethiopia and potentially an important source of starch. The native users cultivate anchote for its medicinal, economic, nutritional, and socio-cultural benefits. The anchote tuber has a significant number of beneficial nutrients, such as carbohydrates, protein, fat, fiber, and different minerals. Compared to other root and tuber crops, this crop is renowned for its vital protein and calcium content. Anchote tubers have a high starch content (75–79%), making them a suitable alternative source of starch for use in several industrial applications. However, understanding the physicochemical properties of starch generated from such underutilized roots and tubers is critical in order to develop unique value-added products. The quality of starch is determined by its physicochemical properties, which include its morphology, particle size, amylose content, crystallinity, thermal properties, and swelling powers. However, there is still a dearth of studies on important anchote starch properties from different genotypes: the rheological properties of anchote starch gels, intrinsic characteristics like storage texture kinetics, and the effect of starch concentration on the gel rheological properties of anchote starch gels, which are so important for their food applications. Thus, this study examines the properties of native and hydrothermally modified starches from four anchote tuber cultivars and compares them to potato and cassava starches. It also investigates the effects of hydrothermal modifications on the pasting, morphological, and thermal properties of anchote flour-starch mix. The study also examines the impact of partial replacement of gluten-free teff flour with modified anchote flour-starch mixes on gluten-free biscuits. The granule sizes of the anchote cultivars varied, but they all exhibited a B-type crystalline structure similar to that of potato starch. The amylose content of anchote starches ranged from 15.8–22.3%. The phosphorus in anchote starches ranged from 82 to 93 mg/100 g, which is much higher than that of potatoes and cassava (60.3 and 5.8 mg/100 g, respectively). This high phosphorus content influences the functional properties of anchote starches, making them well-suited for use in various types of noodles, glucose syrups, and viscous products. Anchote starches had a significantly different gelatinization temperature and enthalpy than potato and cassava starches, ranging from 60.97 to 69.33 °C and 16.87 to 18.38 J/g. Significant differences were also noticed in the pasting properties of anchote cultivar starches. In comparison to potato and cassava, they demonstrated greater stability to heating and shearing, with higher trough viscosity (TV) (2046 to 2280 mPa·s), lower breakdown viscosity (BV) (248 to 487 mPa·s), and a higher final viscosity (FV) (3409 to 3686 mPa·s). These properties are significant in the food processing industry and when high gel viscosity is needed after cooling. In comparison to cassava and potato gels, anchote starch gels displayed considerably greater viscoelastic moduli and much lower (tan δ)1 values. These rheological features are typical of true gels. According to the present findings, anchote starch had acceptable color characteristics that were similar to those of potato and cassava starches. The anchote starch exhibited lightness (L*) and whiteness values above 95 across different cultivars. As the cooking temperature increased from 40 - 90 °C, the swelling power (SP) and water solubility index (WSI) of anchote starches demonstrated a clear rise. It's important to note that the rate of increase differed significantly from that of the control starches, with anchote starches showing a lower increase compared to potato starches and cassava starch in the following order: anchote starches < potato starches < cassava starch. Compared to potato (PS) and cassava (CS) starch gels, anchote starch gels had lower (tan δ)1 values and demonstrated better elasticity, withstanding higher stresses before breaking their structure. In addition, they were more stable at higher concentrations and exhibited higher viscoelastic moduli even at lower concentrations than the PS and CS gels. The study of the textural evolution of the gels over storage revealed that anchote starch gels were less adhesive than PS gel and had initial and final hardness that was significantly higher (≥40%) after 192 hours. The hydrothermal treatments (ANN and HMT) significantly altered the pasting characteristics of anchote starches. The pasting properties (PV, TV, and BV) were decreased significantly after HMT and ANN treatment. HMT significantly reduced the PV of anchote starches compared to ANN treatment. The lower BV values obtained in all studied cultivars show the higher stability of modified anchote starches to thermal treatment and mechanical shearing. The ANN treatment significantly (p < 0.05) increased the final viscosity (FV) compared to HMT and native anchote starches. The rheological property shows the dominance of the elastic over the viscous behavior, having higher G′ values than G″ in the entire frequency range for all studied starch gels. The G′, G′′, and (tan δ)1 values were significantly decreased upon HMT treatment, while ANN treatment significantly increased the G′ and G′′ of anchote starches related to the native starches. Both HMT and ANN increased gelatinization temperatures and decreased enthalpy in all cultivars studied. The study found that the B-type structure of anchote starches remained unchanged after hydrothermal treatments. However, ANN and HMT treated anchote starches had higher relative crystallinity compared to native starches. These results showed that ANN and HMT treatments efficiently modified the rheological, pasting, and thermal properties of anchote starches isolated from four cultivars. The hydrothermal treatments significantly (p < 0.05) affected the pasting properties of anchote flour (DF) and anchote flour-starch mix (DFS). The PV and BV of DF and DFS anchote samples were decreased upon ANN and HMT treatment. The addition of anchote starch to anchote flour significantly improved color characteristics, and carbohydrate contents in both native and hydrothermally modified samples. The study showed that HMT and ANN treatment significantly (p < 0.05) reduced the phytate, tannin, and total phenol contents in both DF and DFS, while the HMT treated samples had the lowest phytate contents compared to ANN and native samples. Likewise, the study showed that the hydrothermal treatments significantly affected the hydration properties (WAC, OAC, SP, and WSI) of studied DF and DFS. The HMT and ANN treatments did not affect the FTIR spectra of studied anchote samples. However, hydrothermal treatments raised the gelatinization temperatures (TO, TP, and TC) of DF and DFS. The results revealed that hydrothermal treatments enhanced the thermal stability of DF and DFS samples. As a result, it appears that the HMT and ANN anchote flours would be appropriate for applications requiring heat stability. The growing consumer demand for gluten-free food products has led to an increased need for innovative gluten-free ingredients that offer improved nutritional benefits. Thus, this study examines the impact of the partial replacement of gluten-free teff flour (TF) by modified anchote flour-starch mixes (HMT-DFS and ANN-DFS) on the physical, nutritional and sensory characteristics of gluten-free biscuits. The result showed that the color, proximate compositions, pasting, and functional characteristics of the gluten-free flours used in this study varied significantly (p < 0.05). HMT-DFS and ANN-DFS flours had higher L*, a*, b*, and whiteness values compared to TF flour. The protein contents of gluten-free HMT-DFS and ANN-DFS flours were almost similar, while those of TF flour had a slightly higher protein content. But HMT-DFS and ANN-DFS had significantly higher ash contents and lower fat and fiber contents compared to TF. The pasting properties of the studied flour samples varied significantly (p < 0.05). The lowest BV value of the ANN-DFS and HMT-DFS samples shows that they have the highest stability to thermal treatment and mechanical shearing; thus, these samples are ideal functional ingredients in formulations of food products that require higher thermal treatments. The study showed that substituting gluten-free HMT-DFS and ANN-DFS flours for teff flour did not affect biscuit thickness, but slightly increased spread ratio. However, the inclusion of HMT-DFS and ANN-DFS significantly influenced color features. The study also found that incorporating anchote flour-starch mix into teff flour significantly affected color characteristics at higher substitution levels. The study found that gluten-free biscuits AB10, AB20, HB10, and HB20 had superior physical and sensory properties compared to control biscuits. These biscuits had higher ash, fat, and fiber contents than the control WB biscuits and comparable values with the control TB biscuits. The study also found that incorporating a modified anchote flour-starch mix in gluten-free teff flour biscuits enhanced proteins, carbohydrates, energy values, and mineral contents, making it a useful functional ingredient for gluten-free formulations. Therefore, the present findings showed that the hopeful potential utilizations of modified anchote flour and starches as functional ingredients in food processing, product development, novel food product formulations, and additional industrial applications.en-USanchote tuberfunctional ingredientgelshydrothermal treatmentspasting propertiesrheological propertiesstarchtexture storage kineticsthermal propertiesAnchote (Coccinia abyssinica (Lam.) Cogn) Starch and Flour Modification Using Hydrothermal Treatments and Valorization as Functional Ingredients in the Development of Food ProductsDissertation