2025 年 31 巻 5 号 p. 441-453
This study aims to evaluate the physicochemical, thermal, and functional characteristics of powders and starches derived from four cassava varieties (Chichu, Hawassa-4, Kello, and Qulle) grown in Ethiopia. To achieve this aim, a factorial design was employed with four cassava variety with two product type (starch and powder). The results revealed significant variations on above mentioned properties. Qulle and Kello cassava starches exhibited the highest amylose contents, at 13.73 % and 13.6% respectively, whereas Chichu and Hawassa-4 powders showed significantly lower 2.35 % and 4.4% respectively. Hawassa-4 powder demonstrated higher water-holding capacity (2.7 mL/g), oil-holding capacity (2.2 mL/g), and pasting temperature (71.12 °C), making it preferable for cookie development. Chichu and Qulle powders had lower gelatinization temperatures and setback viscosity, indicating their suitability for bakery applications. Overall, this study provides valuable insights into the properties of cassava varieties, which can guide the selection of appropriate cassava types for specific food applications.
Cassava (Manihot esculenta) is viewed as an important food security crop with great potential for food applications. Its powder and starch are used as raw materials in the processing of a wide range of value-added food products (Awoyale et al., 2017). The rising demand for cassava starch and powder for domestic and industrial food products has encouraged cassava breeders to focus on increased yield, improved nutrition, and disease resistance (Mbanjo et al., 2021). This has led to the release of several cassava varieties. This study focuses on four Ethiopian cassava varieties—Chichu, Hawassa-4, Kello, and Qulle—that were released for food use (Eshbel, 2022; Tadesse et al., 2020). However, traditional methods of processing local cassava varieties were common in Ethiopia, with little use of value-added products (Gezahegn and Bazie, 2021). Evaluation of varietal differences for different food applications might be crucial in unlocking cassava’s potential for food innovation. This could enable the development of diverse, value-added products that enhance food security and nutrition.
Findings of several studies have shown that differences exist among cassava varieties in terms of their starch composition, morphological, functional, thermal, and pasting properties (Akonor et al., 2023; Tingting et al., 2023; He et al., 2020; Aprianita et al., 2014). For their varied food applications, information regarding the contents and characteristics of the powder and starch of cassava varieties is needed. For example, the low amylose content of starch showed high swelling power and had good bakery product quality(Charles et al., 2005). Understanding pasting properties is crucial for assessing the cooking quality of food and is also used for identifying starch applications in different foods (Zhang et al., 2020; Awoyale et al., 2017). The lower setback viscosity makes the starch have a lower retrogradation tendency during cooling and a lower staling rate (Chisenga et al., 2019), which is desirable for bread and injera products. The temperature at which gelatinization occurs determines the amount of energy required to cook a food matrix (He et al., 2020). A deeper understanding of the characteristics of these varieties is crucial for their food applications.
Previous research in Ethiopia has primarily focused on the physicochemical and functional characteristics of cassava, often emphasizing the acceptability of cassava-based products (Halake and Chinthapalli, 2020; Girma et al., 2015; Mesfin and Shimelis, 2013; Berhanu and Desta, 2017). However, a comprehensive study on the physicochemical, thermal, pasting, and functional properties of both the starch and powder forms of Ethiopian cassava varieties has not been exhaustively conducted. Most existing studies treat cassava as a single ingredient, without differentiating between the potential contributions and applications of cassava powder and isolated starch. Yet, these two forms differ significantly in composition—cassava powder contains fiber, protein, and other constituents, while starch is more refined and predominantly composed of carbohydrates—potentially affecting their behavior in food processing and applications. Additional evaluation of both starch and powder from these varieties may provide insights into their suitability for diverse food uses. This knowledge gap might be one reason for the limited utilization of cassava-based value-added food products in Ethiopia (Daemo et al., 2023). To address this gap, the present study aimed to evaluate the physicochemical, thermal, and functional properties of starch and powder from four cassava varieties grown in Ethiopia. By identifying key differences and highlighting unique characteristics, the study provides a scientific basis for selecting appropriate cassava forms for specific food applications and informs future research directions.
Material Fresh cassava roots were obtained from the Hawassa Agricultural Research Centre, Ethiopia. Four sweet cassava varieties—Chichu, Hawassa-4, Kello, and Qulle—released for food use in Ethiopia were selected for the current experimental research. The cassava roots were harvested 18 months after planting and used for powder and starch processing.
Experimental design A factorial design experiment with two factors, such as the variety of cassava at four levels (Chichu, Hawassa-4, Qulle, and Kelo) and the types of products at two levels (powder and starch), was used in this study. Granule size, functional properties, proximate composition, starch composition, pasting properties, and thermal properties were studied in this experiment.
Cassava powder preparation and storage Cassava powder was processed according to Kebede et al. (2012) with a slight modification (the extended drying time). Fresh cassava roots were peeled, washed, sliced, and then sun-dried (15 hrs) until a constant moisture content was reached. During the drying process, the average daytime temperature varied between 26 °C and 28 °C, while the relative humidity remained around 40 %. These values reflect overall conditions but do not capture short-term fluctuations during drying. To maintain consistency and ensure proper drying, conditions were monitored daily using a thermometer, helping to minimize variations and achieve the target moisture content. Then milled and the powder was sieved (750 µm), packaged in a polyethylene bag, and stored at 4 oC until use.
Cassava starch extraction and storage The extraction of starch was conducted according to Chisenga et al. (2019). The fresh cassava roots were washed, peeled, chopped into small pieces, and then pulverized in a blender. The pulp was suspended in tap water in a ratio of 1:10. Then the well-stirred mixture was filtered using double cheesecloth. The collected filtrate was allowed to sediment, and after decanting, the supernatant was washed six times with tap water. The resultant starch was washed using distilled water, and after decanting, the starch was oven-dried at 35 °C for 24 hours. The starch yield was packed in a polyethylene bag for further processing.
Determination of starch granule size distribution Starch granule morphology was analyzed using a scanning electron microscope (SEM) (JCM-6000Plus) following Chisenga et al. (2019). Starch samples were mounted on adhesive tape, sputter-coated with gold, and examined at 1.00 KX magnifications (SEI mode, 30 pA, 5.00 kV). Granule size was measured from 70 granules per image, categorized into diameter ranges (> 20, 15–20, 10–15, 5–10, and 0–5 µm). The percentage distribution was calculated by dividing the number of granules in each range by the total granules.
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Determination of the amylose and amylopectin content Amylose and amylopectin contents were determined using the K-AMYL assay kit (Megazyme), based on the method of Yun and Matheson (1990). A 20 mg flour sample was dispersed in dimethyl sulfoxide (DMSO) and precipitated in ethanol to remove lipids. The starch was then dissolved in sodium acetate buffer. Amylopectin was selectively precipitated using the lectin concanavalin A (Con A) and removed by centrifugation. The amylose remaining in the supernatant was enzymatically hydrolyzed to glucose using amyloglucosidase and α-amylase, followed by quantification through the glucose oxidase–peroxidase (GOPOD) reaction. Absorbance was measured at 510 nm using a UV-Vis spectrophotometer (Specord 210 Plus). Total starch was hydrolyzed in a separate reaction, and amylose content was calculated as the ratio of GOPOD absorbance of the Con A supernatant to that of total starch.
Amylose (%)=(Absorbance of the supernatant)/
(Absorbance of the total starch)×6.15/9.2×100 ・・・・ Eq. 2
Where the constants 6.15 and 9.2 are the dilution factors for the Con A and total starch extracts.
Resistant starch assay procedure The resistant starch (RS) content in cassava powder and starch was determined using the Megazyme Resistant Starch Assay Kit (K-RSTAR) following the manufacturer’s protocol (Megazyme, 2023). A 0.15 g sample was hydrolyzed using pancreatic α-amylase and amyloglucosidase (AMG) in a 37 °C water bath for 4 hours. Ethanol (99 % v/v) was added, and the mixture was vortexed and centrifuged (1 500 rpm, 10 min). The pellet was sequentially washed with 50 % ethanol and re-centrifuged. After drying, 2 M KOH was added to dissolve RS, followed by neutralization with sodium acetate buffer (pH 3.8) and AMG hydrolysis at 50 °C for 30 min. The solution was diluted to 100 mL and the RS content was measured using glucose oxidase-peroxidase (GOPOD) reagent at 510 nm (Specord 210 Plus). Non-RS was analyzed similarly by treating the combined supernatants with AMG and GOPOD. D-glucose served as the standard, and a reference sample provided assay validation. RS, non-RS, and total starch were calculated on a dry-weight basis (Megazyme, 2018). The percent resistant starch (RS), non-RS, and total starch were calculated on a dry weight basis as follows:
RS (%)=∆E F/W×90 ・・・・・・ Eq. 3
Non-RS (%)=∆E F/W×90 ・・・・・・ Eq. 4
Total Starch= RS(%)+Non-RS(%) ・・・・・・ Eq. 5
where ΔE is absorbance (reaction) read against the reagent blank, F is conversion factor from absorbance to micrograms, W is dry weight of sample.
Moisture content determination The moisture content of the dried flour samples was determined in triplicate according to AOAC, (2000). method 925.10 involves drying a 2.0 g sample at 130 ºC for two hours.
Moisture (%)=[((W1+W2)-W3)/W1]×100 ・・・・ Eq. 6
Where: W1is the weight of sample (g) after zeroing the balance, W2 is the weight of the aluminum cup, W3 is the weight of the aluminum cup plus weight of the sample after drying
Crude fat content determination The fat content was determined using soxlet ether extraction techniques according to the standard method expressed in AOAC, (2000) method No. 920.39. The fat content was calculated using the formula. A five-gram sample was used for extraction.
Crud Fat (db) %= [(W2-W1)/W] ×100 ・・・・・・ Eq. 7
Where: W1 is Weight of the extraction flask (g), W2 is Weight of the extraction flask + the extracted crude fat (g), and W is Weight of the sample (g)
Ash content determination The sample ash content was determined according to AOAC, (2000) method 923.03 by taking about 3.0 g of sample after carbonization and ignition at 500 °C for 6 h in the muffle furnace (Model 2-525, J. M. Ney furnace, Yucaipa, USA).
Ash % = ((W3-W2)/W1)×100 ・・・・・・ Eq. 8
Where, W1 is weight of cassava powder or starch before ashing, W3 weight of cassava powder or starch after ashing with weight of crucible; W2 is weight of crucible.
Crude fiber determination The acid and alkaline digestion procedure was used to assess the crude fiber content in accordance with the standard method in (AOAC, (2000). No. 962.09. About 1.5 g of the sample was used for the determination of crude fiber.
Crude fiber % (db) = [(W2-W3)/W1] ×100 ・・・ Eq. 9
Where: W1 is weight of samples (g); W2 is weight of crucible and residue after drying (g)
W3 is weight of crucible and ash after incarnations (g)
Crude protein determination The protein content was determined following the Kjeldhl method in accordance with the standard method in AOAC, (2000). About 1 g of samples were used for crude protein determination. The borate ion was titrated with a standardized 0.1 N hydrochloric acid solution using Kjeldahl analyzer distillation until a light pink color was observed.
Nitrogen % = [(Vs-Vb)/10W] ×NHCl×14.01g ・・・ Eq. 10
Where: Vs is volume of HCl consumed during titration of sample (mL), Vb is volume of HCl consumed during titration of blank (mL), N is normality of HCl used (0.1), W is Weight of sample (g), 14 is molecular weight of nitrogen
The percent of nitrogen was converted to the protein percentage as follows:
Crude protein % = %N× F ・・・・・・ Eq. 11
Where: the conversion factor is 6.25
Determination of water holding capacity (WHC) and oil holding capacity (OHC) The water and oil holding capacity of the cassava powder and starch samples was determined according to the method mentioned in Huang et al. (2007). About 1 g of sample (W1) was weighed in a previously cleaned and weighed test tube by using a digital electronic balance. Ten mL of water or oil was added to the test tube along with the sample (W2) and vortexed to mix the powder and water or oil. Then the test tube was allowed to stand for 30 min. The test tube containing the solution was centrifuged at 3 000 rpm for 30 min. Finally, the supernatant was discarded; the test tube with sediment was weighed (W3), and the water/oil holding capacity was calculated as follows:
WAC or OAC % = [((W3-W2))/(W1)] ×100 ・・・ Eq. 12
Where: W1 is Weight of dry sample (g), W2 is Weight of tube and dry sample (g), W3 is Weight of tube + sediment (g)
Pasting property analysis The pasting properties of the powder and extracted starch of cassava were assessed using Rapid Visco Analyzer (RVA) (Model: RVA4500, Perten) as reported in Chisenga et al. (2019). The samples (2 g dry basis) were suspended in 12 g of distilled water. A heating-and-cooling cycle program was utilized. The samples were held at 50 °C for 1 min, followed by heating to 95 °C for 7.5 min at a heating rate of 6 °C/min, holding at 95 °C for 5 min, cooling to 50 °C for 7.5 min, and holding at 50 °C for 1 min. Parameters measured were pasting temperature (PT), peak viscosity (PV), final viscosity (FV), breakdown viscosity (BD) as PV-HPV, peak time, and setback viscosity (SB) as CPV-HPV.
Determination of Swelling Power and Solubility Swelling power and solubility were determined using the method of Leach as described by Kusumayanti et al. (2015). A 0.2 g sample was dispersed in 10 mL of distilled water in a test tube and heated in a water bath at 60 °C for 30 min with constant stirring. The suspension was centrifuged at 1 600 rpm for 15 min. The supernatant was carefully decanted, and the sediment paste was weighed to calculate the swelling power using Equation (13). The supernatant was transferred to a pre-weighed Petri dish and dried in an oven to constant weight. The dried residue was weighed, and solubility was calculated using Equation (14).
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Determination of thermal properties The thermal properties parameters (start, peak, and finish gelatinization temperature and enthalpy of gelatinization) of cassava powder and starch were measured using differential scanning calorimetry (Model TA Q200), as reported in (Huang et al., 2007). Four milligrams of starch and 16 mg of water were combined in an aluminum pan for the measurement. Hermetically sealed is the lid. To give it time to acclimate, the sample is allowed to stand for an hour. An empty crucible was used as the reference sample for the measurement in the DSC apparatus. Starting at 30 °C and reaching 150 °C at the end, the heating rate is 10 °C/min. Nitrogen was used as the purge gas at 30 ml/min. The data was collected by TA Instrument Explorer and evaluated with TA Universal Analysis.
Data analysis The data was analyzed using JMP Pro 14 software. Granule size was analyzed using Imagej software and SPSS software version 26. Eight samples in duplicate totally sixteen samples were analyzed in this research. Two- way ANOVA was employed to assess the effects of independent variables. The mean differences were determined using the Tukey Honestly Significant Difference (HSD). Spearman’s correlation was employed to see the relationship among variables of interest. The data was collected in triplicate, and a significance difference test at the 0.05 significant levels was used.
Granule size distribution The granule size distribution of cassava starch and powder, analyzed via SEM, revealed distinct variations across varieties (Fig. 1 and 2). The average starch granule sizes for Chichu, Hawassa-4, Kello, and Qulle cassava varieties were 9.1 µm, 8.8 µm, 9.0 µm, and 10.47 µm, respectively. The corresponding granule sizes in the powder samples were 9.6 µm, 7.6 µm, 10.3 µm, and 9.9 µm, respectively. Starch granule sizes ranged from 2.75 to 22.5 μm,with Qullestarch exhibiting the largest granules (22.5 μm) and Chichu starch the smallest (2.75 μm). Granule size distribution varied by variety and product type, with 60 % of Chichu cassava powder and 80 % of Hawassa-4 powderfalling within the 0–10 µm range. Notably, granule size showed a strong negativecorrelation with water-holding capacity (r = -0.8, Table 1).
Amylose, amylopectin, resistant and non-resistant Starch Contents Amylose and amylopectin, the key components of starch, play a crucial role in determining its properties and applications. Their contents varied significantly among cassava varieties (p < 0.05) (Table 2). Qulle and Kello starches exhibited the highest amylose contents, at 13.73 % and 13.6 %, respectively, while Chichu powder had the lowest value at 2.35 % (Table 2). Notably, all varieties in this study had amylose levels below 15 %. A strong negative correlation (r = -0.8) was observed between amylose content and swelling power (Table 1). Resistant starch (RS) and non-resistant starch (NRS) also differed significantly (p < 0.05) across cassava starches and powders (Table 2). Qulle starch contained the highest RS (15.61 %), whereas its corresponding powder had the lowest (1.42 %). Additionally, granule size showed a strong positive correlation with RS content (r = 0.9) (Table 1).
Proximate compositions The proximate composition of cassava starch and powder showed significant variation (p < 0.05) across varieties (Table 3). Moisture content ranged from 7.41 % to 9.22 % in powders and 10.3 % to 12.5 % in starches. Fiber content also varied significantly, with Hawassa-4 powder having the highest (4.8 %) and Kello starch the lowest (0.2 %). The highest fat content (1.8 %) was recorded in Chichu powder, while Hawassa-4, Kello and Qulle starchs had the lowest (negligible amounts). Protein, a key macronutrient in food formulations, was generally low in cassava starch and powder. It was highest in Kello powder (1.7 %), whereas the starches of Qulle and Kello contained negligible amounts. Ash content also differed significantly among the samples.
Cassava powder and cassava starch granules.
Where CP = Chichu powder, HP = Hawassa-4 powder, KP = Kello powder, QP = Qulle powder, CS = Chichu starch, HS = Hawassa-4 starch, KS = Kello starch, QS = Qulle starch,
Powder and starch particles size distribution of cassava varieties.
Where CF = Chichu powder, HF = Hawassa-4 powder, KF = Kello powered, QF = Qulle powder, KS = Kello starch, CS = Chichu starch, HS = Hawassa-4 starch, Kello starch, QS = Qulle starch
| GS | Amy | NRS | RS | WHC | SW | SO | PV | BDV | FV | SBV | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| GS | 1 | ||||||||||
| Amy | 0.70* | 1 | |||||||||
| NRS | 0.7** | −0.4 | 1 | ||||||||
| RS | 0.9*** | −0.1 | 0.9*** | 1 | |||||||
| WHC | −0.8*** | −0.2 | −0.6** | −0.7** | 1 | ||||||
| SW | 0.2 | −0.8** | 0.6* | 0.23 | 0.0 | 1 | |||||
| SO | −0.7* | −0.0 | −0.7** | −0.7** | 0.7** | −0.0 | 1 | ||||
| PV | 0.8*** | −0.4 | 0.8*** | 0.9*** | −0.6* | 0.5* | −0.6** | 1 | |||
| BDV | 0.7** | 0.2 | 0.4 | 0.7** | −0.7** | −0.1 | −0.7** | 0.4 | 1 | ||
| FV | 0.2 | −0.3 | 0.2 | 0.2 | −0.1 | 0.3 | 0.4 | 0.4 | −0.5 | 1 | |
| SBV | 0.7** | 0.2 | 0.3 | 0.7** | −0.6** | −0.2 | −0.7** | 0.5 | 0.23 | −0.4 | 1 |
| PT | −0.7** | 0.4 | −0.8*** | −0.6* | 0.6* | −0.6* | 0.3 | −0.7** | −0.2 | −0.1 | 0.8* |
Where GS = Granule size, Amy = Amylose content, NRS = Non-resistant starch, RS = Resistant starch, WHC = Water holding capacity, SW = Swelling capacity, SO = Solubility, PV Peak viscosity, BDV = Breakdown Viscosity FV = Final Viscosity, SBV = Setback viscosity, PT = Pasting Temperature, * = p < 0.05, ** = p < 0.01, *** = p < 0.001
| Product type | Varieties | Amylose (%) | Amylopectin (%) | Resistantstarch (%) | Nonresistant starch (%) |
|---|---|---|---|---|---|
| Powder | Chichu | 2.4 ± 0.1 e | 97.7 ± 0.1 a | 2.6 ± 0.3 d | 80.7 ± 0.3 c |
| Powder | Hawassa-4 | 4.3 ± 0.8 d | 95.7 ± 0.8 b | 3.0 ± 0.1 d | 80.9c ± 0.4 c |
| Powder | Kello | 12.5 ± 0.1 b | 87.5 ± 0.2 d | 2.3 ± 0.4 de | 75.4 ± 0.3 e |
| Powder | Qulle | 13.6 ± 0.2 a | 86.4 ± 0.3 e | 1.4 ± 0.1 e | 78.1 ± 1.0 d |
| Starch | Chichu | 5.8 ± 0.2 c | 94.2 ± 0.2 c | 13.1 ± 0.3 c | 86.3 ± 0.3 a |
| Starch | Hawassa-4 | 5.8 ± 0.1 c | 94.2 ± 0.1 c | 14.1 ± 0.1 b | 84.8 ± 0.2 ab |
| Starch | Kello | 13.6 ± 0.3 a | 86.4 ± 0.2 e | 13.5 ± 0.1 bc | 85.7 ± 0.2 a |
| Starch | Qulle | 13.7 ± 0.1 a | 86.3 ± 0.1 e | 15.6 ± 0.43 a | 83.5 ± 0.4 b |
Mean ± standard deviation. Values with same letter differ non-significantly ( p > 0.05)
| Product types | Cassava varieties | Moisture (%) | Fiber (%) | Fat (%) | Protein (%) | Ash (%) |
|---|---|---|---|---|---|---|
| Powder | Chichu | 7.8 ± 0.1 de | 2.4 ± 0.1 c | 1.8 ± 0.1 a | 1.5 ± 0.0 b | 2.5 ± 0.1 c |
| Powder | Hawassa-4 | 7.4 ± 0.1 e | 4.8 ± 0.2 a | 1.2 ± 0.1 ab | 1.2 ± 0.0 c | 4.8 ± 0.2 a |
| Powder | Kello | 9.2 ± 0.2 c | 2.7 ± 0.0 c | 1.1 ± 0.0 ab | 1.7 ± 0.1 a | 2.7 ± 0.0 c |
| Powder | Qulle | 8.7 ± 0.1 cd | 3.5 ± 0.1 b | 1.1 ± 0.1 ab | 1.6 ± 0.1 b | 3.5 ± 0.1 b |
| Starch | Chichu | 10.3 ± 0.2 b | 0.4 ± 0.1 d | 0.6 ± 0.6 bc | 0.1 ± 0.1 d | 0.2 ± 0.1 d |
| Starch | Hawassa-4 | 12.5 ± 0.7 a | 0.3 ± 0.1 d | − | 0.1 ± 0.1 d | 0.2 ± 0.1 d |
| Starch | Kello | 12.5 ± 0.0 a | 0.2 ± 0.0 d | − | − | − |
| Starch | Qulle | 13.1 ± 0.1 a | 0.5 ± 0.0 d | − | − | − |
Mean ± standard deviation. Values with same letter differ non-significantly ( p > 0.05). _ Represents values are not worth significant mention in terms of nutritional value.
| Product types | Cassava varieties | WHC (mL/g) | OHC (mL/g) | Swelling power (g/g) | Solubility (g/g) |
|---|---|---|---|---|---|
| Powder | Hawassa-4 | 2.7 ± 0.1 b | 2.2 ± 0.4 ab | 5.6 ± 0.4 c | 0.1 ± 0.2 d |
| Powder | Chichu | 2.9 ± 0.1 a | 1.9 ± 0.2 bc | 6.4 ± 0.18 b | 0.4 ± 0.1 a |
| Powder | Kello | 2.5 ± 0.1 c | 2.2 ± 0.1 ab | 3.9 ± 0.1 e | 0.2 ± 0.13 c |
| Powder | Qulle | 2.5 ± 0.2 c | 1.9 ± 0.1 bc | 3.9 ± 0.1 e | 0.3 ± 0.1 b |
| Starch | Hawassa-4 | 1.9 ± 0.1 d | 1.9 ± 0.25 bc | 6.0 ± 0.1 bc | 0.1 ± 0.2 d |
| Starch | Chichu | 1.6 ± 0.1 e | 1.8 ± 0.1 c | 6.9 ± 0.1 a | 0.1 ± 0.2 d |
| Starch | Kello | 1.6 ± 0.2 e | 1.6 ± 0.3 d | 4.8 ± 0.6 d | __ |
| Starch | Qulle | 1.6 ± 0.1 e | 1.9 ± 0.3 bc | 4.4 ± 0.84 d | 0.1 ± 0.3 d |
Mean ± standard deviation. Values with same letter differ non-significantly ( p > 0.05). _ Represents values are not worth significant mention in terms of nutritional value, WHC= Water holding capacity, OHC = Oil holding capacity
| Product types | Variety | Peak viscosity (RVU) | Breakdown viscosity (RVU) | Final viscosity (RVU) | Setback viscosity (RVU) | Peak time (Min) | Pasting temperature (°C) |
|---|---|---|---|---|---|---|---|
| Powder | Haawassa4 | 90.6 ± 2.1 f | 16.3 ± 3.5 f | 96.8 ± 4.2 e | 22.4 ± 7.1 d | 5.9 ± 0.1 a | 71.1 ± 0.0 a |
| Powder | Chichu | 121.6 ± 3.2 e | 104.8 ± 4.2 a | 19.3 ± 2.8 g | 2.5 ± 2.1 f | 3.4 ± 0.1 d | 69.3 ± 0.5 abc |
| Powder | Kello | 122.4 ± 1.4 e | 9.5 ± 0.7 h | 140.6 ± 4.2 c | 29.2 ± 7.1 c | 5.6 ± 0.3 ab | 69.4 ± 1.4 abc |
| Powder | Qulle | 80.3 ± 4.2 g | 72.2 ± 7.8 c | 10.7 ± 1.4 h | 2.5 ± 0.7 f | 3.5 ± 0.0 d | 70.6 ± 0.6 ab |
| Starch | Haawassa4 | 173.5 ± 3.5 a | 81.5 ± 2.1 b | 138.8 ± 2.8 d | 46.8 ± 10.6 a | 4.9 ± 0.0 c | 68.8 ± 0.4 abc |
| Starch | Chichu | 127.8 ± 1.4 c | 63.8 ± 1.4 e | 77.4 ± 1.4 f | 13.5 ± 2.8 e | 5.2 ± 0.1 bc | 67.0 ± 0.6 c |
| Starch | Kello | 125.5 ± 5.7 d | 14.2 ± 5.7 g | 144.5 ± 0.7 a | 33.1 ± 4.9 b | 5.8 ± 0.1 a | 68.9 ± 0.3 abc |
| Starch | Qulle | 163.2 ± 4.2 b | 65.4 ± 0.7 d | 142.0 ± 8.5 b | 46.7 ± 7.8 a | 5.1 ± 0.1 c | 68.6 ± 0.6 bc |
Mean ± standard deviation. Values with same letter differ non-significantly ( p > 0.05).
Functional properties of starch and powder of cassava The functional properties of cassava powder and starch varied significantly (p < 0.05) among varieties (Table 4). Chichu powder exhibited the highest water-holding capacity (WHC) at 2.9 mL/g, while the lowest (1.6 mL/g) was recorded for starches from Kello, Qulle, and Chichu. Oil-holding capacity (OHC) was highest (2.23 mL/g) in powders from Kello and Hawassa-4, whereas Kello starch had the lowest (1.63 mL/g). Chichu powder also demonstrated the highest water solubility (0.4 g/g), while Kello starch showed an insignificant solubility level. Swelling power displayed a strong negative correlation with amylose content (r = −0.8, Table 1). The water solubility had a significant negative correlation (r = −0.67) with granule size (Table 1).
Pasting properties The pasting properties of cassava starch and powder varied significantly (p < 0.05) among varieties (Table 5). Hawassa-4 starch exhibited the highest peak viscosity (173.5 RVU), while the lowest (80.3 RVU) was recorded for Qulle powder. Breakdown viscosity was highest in Chichu powder (104.8 RVU) and lowest in Kello powder (9.5 RVU). Setback viscosity varied significantly, with Hawassa-4 starch exhibiting the highest value (46.8 RVU), while Chichu and Qulle powders showed the lowest values (2.5 RVU). The pasting temperature ranged from 68.9°C to 71.1 °C, with no significant differences observed among the powder samples of Hawassa-4, Chichu, Kello, and Qulle, as well as Kello starch. However, the lowest pasting temperature was observed in Chichu starch (67 °C).
Thermal properties The thermal properties and enthalpy (ΔH) of cassava powder and starch were analyzed using a differential scanning calorimeter (DSC), with results presented in Table 6. Significant differences (p < 0.05) were observed among products (powder and starch) of cassava varieties. Qulle, Hawassa-4, and Kello starches exhibited the highest onset gelatinization temperatures (57.5 °C, 57.4 °C, and 56.9 °C, respectively), while the lowest temperatures (55.5 °C and 55.9 °C) were recorded for Chichu and Qulle powders, respectively. Enthalpy of gelatinization varied significantly (p < 0.05), with Kello and Qulle starches showing the highest (16.3 and 16.1 J/g) and their corresponding powders and Hawassa-4 powder showed the least. Overall, cassava powders exhibited lower enthalpy values than their corresponding starches.
| Product type | Variety | T 0 [°C] | T peak [°C] | T c [°C] | ΔH [J/g] |
|---|---|---|---|---|---|
| Powder | Hawassa-4 | 56.5 ± 0. 3 bc | 65.9 ± 0.14 b | 73.5 ± 0.15 b | 11.6 ± 011 d |
| Powder | Chichu | 55.5 ± 0. 4 d | 66.6 ± 0.15 a | 73.7 ± 0.14 a | 13.1 ± 0.05 c |
| Powder | Kello | 56.3 ± 0.6 c | 63.8 ± 0.2 c | 72.4 ± 0.1 ab | 11.2 ± 0.2 d |
| Powder | Qulle | 55.9 ± 0.4 cd | 64.5 ± 0.14 b | 72.3 ± 0.84 ab | 11.8 ± 0.1 d |
| Starch | Hawassa-4 | 57.4 ± 0.13 a | 62.1 ± 0.07 ef | 68.5 ± 0.35 c | 14.9 ± 0.01 b |
| Starch | Chichu | 56.4 ± 0.12 bc | 62.5 ± 0.06 d | 66.2 ± 0.28 d | 13.7 ± 0.02 c |
| Starch | Kello | 56.9 ± 0.14 ab | 61.5 ± 0.28 f | 68.6 ± 0.42 c | 16.3 ± 0.42 a |
| Starch | Qulle | 57.5 ± 0.32 a | 62.2 ± 0.21 de | 69.23 ± 0.28 c | 16.1 ± 0.15 a |
Mean ± standard deviation. Values with same letter differ non-significantly ( p > 0.05). T 0 = onset gelatinization temperature, T peak = Peak gelatinization temperature, T c = Conculusion gelatinization temperature, ΔH = Enthalpy of gelatinization
SEM analysis showed notable differences in the size and shape of cassava starch and powder granules among varieties (Fig 1 and 2). Cassava powder had more irregular granules due to fragmentation and merging during processing (Fig 1), consistent with the findings of Nilusha et al. (2021) and Akonor et al. (2023). A strong negative correlation (r = -0.8) between granule size and water holding capacity (Table 1) supports Chisenga et al. (2019), who found that smaller granules offer a greater surface area, enhancing water absorption. Varieties with a higher proportion of small granules exhibit superior water uptake, making them suitable for applications requiring a smooth texture (Onitilo et al., 2007). The average granule sizes of starch and powder from the Hawassa-4 variety were 8.8 µm and 7.6 µm, respectively—both smaller than those of the other cassava varieties. In baking, smaller granule size is associated with enhanced water absorption, which positively influences texture, moisture retention, and overall product quality (Tatiana et al., 2021). Improved flour hydration enhances interactions with fats and liquids, which influences gluten formation and contributes to desirable cookie texture. Due to their higher proportion of small granules, the Chichu and Hawassa-4 varieties may be particularly well-suited for bakery applications.
The cassava varieties analyzed in this study had amylose contents below 15 %, categorizing them as waxy-type starches rather than normal starches (Rolland-Sabaté et al., 2012). A strong negative correlation (r = -0.8) was found between amylose content and swelling power, suggesting that lower amylose levels enhance swelling capacity, a key functional property affecting starch performance. Cassava varieties with low amylose content are well-suited for bakery applications (Lin et al., 2023; Chisenga et al., 2019). In contrast, teff starch, commonly blended with cassava for injera production, has much higher amylose content (28.4 %), indicating that cassava powder, with its lower amylose and greater swelling power, can improve the texture of baked foods. Given these properties, cassava powders from the Chichu and Hawassa-4 varieties appear particularly suitable for bakery applications, including bread making and injera production in Ethiopia.
Resistant starch (RS) is a key functional component that slows digestion in the upper gastrointestinal tract and promotes gut health (Remya and Jyothi, 2015). In this study, Qulle starch, which had the largest average granule size (Fig. 1), exhibited the highest RS (15.6) content (Table 2). However, it is important to note that these values were obtained using raw starch and flour. The RS content of Qulle starch may change upon cooking, as heat treatment typically alters starch property. On the other hand, Qulle powder showed the lowest RS content, likely due to granule damage caused by the dry milling process used in powder preparation (see Cassava Powder Preparation and Storage section).This reduction in RS levels underscores the impact of processing on starch functionality. The high RS content in Qulle starch suggests its potential for health-focused food formulations, particularly for glycemic control and dietary fiber enrichment.
The results revealed that the moisture content of all samples was below the recommended safe moisture content (13 %) for cassava powder (CAC, 1989). The fiber content of the cassava varieties in this study (0.2–4.8 %) was higher than the range reported in previous studies (1.06 to 1.18 %) by Montagnac et al. (2009), but lower than the 2.98 to 12.43 % reported by Aldana et al. (2013). The highest fiber content (4.8 %) was recorded for Hawassa-4 cassava powder and lowest was recorded for starch samples of all variety. In food applications, the presence of fiber can also enhance water and oil absorption capacity, improve textural quality, and contribute to satiety, which may be beneficial in formulating functional foods and diet-based interventions for weight management (Elleuch et al., 2011). Moreover the presence of non-starch components such as fiber, protein, and ash may interfere with the accurate determination of starch granule size and amylose content (Hoover, 2001). Protein content in current study ranged from 1.5 to not worth significant value. Previous studies reported protein contents in cassava powder ranging from 0.74 to 1.32 % (Manano et al., 2017) and 0.51 to 1.26 % (Oyeyinka et al., 2019), which indicates that the protein content in the current research is consistent with these previous findings.
The greater water holding capacity (WHC) of cassava powder compared to starch is likely due to its composition, which includes protein, and fiber. These hydrophilic components, particularly proteins and fibers might enhance water retention. This observation is consistent with previous studies reporting similar WHC values for cassava powder and starch, highlighting the significant role of protein and fiber in water absorption (Awoyale et al., 2017). The highest oil holding capacity (2.2 mL/g) observed for both Chichu and Hawassa-4 cassava powders indicates their potential suitability for various food product applications, particularly those requiring fat retention and improved mouth feel. High OHC is a desirable functional property in the formulation of products such as baked goods, meat analogs, and snack foods, where oil retention enhances flavor, texture, and caloric density (Adeyeye and Adesina, 2021). The study identified a significant negative correlation (r = −0.8) between amylose content and swelling power, aligning with the findings of Chisenga et al. (2019). This indicates that cassava varieties with lower amylose content, such as Chichu and Hawassa-4, are more suitable for applications requiring enhanced swelling and improved texture, particularly in bakery products. Cassava milling appeared to disrupt granule integrity, changes its functional property in cassava powder (Dasa and Binh, 2019). This supports the idea that mechanical processing impacts starch functionality, an important consideration for optimizing cassava-based ingredients. Additionally, the water solubility and swelling characteristics observed in cassava powders, particularly from Chichu with its smaller granule size, suggest superior hydration properties (Tatiana et al., 2021). The enhanced swelling and solubility of Chichu powder highlight its potential for improving the texture and quality of baked foods, offering valuable insights for specialized food formulations.
The ability of starch to form a paste or gel plays a crucial role in determining the texture of food products (Nilusha et al., 2023; Alamu et al., 2022). Peak viscosity which reflects the thickening potential of starch (Alamu et al., 2022), varies among the studied varieties, Qulle powder exhibited the lowest peak viscosity, might generally suggests greater cooking stability. Qulle powder with larger average granule size (10.47 µm) had reduced surface area for water interaction (Figure 1) or processing parameters like higher pasting temperatures (70.6 °C) (Table 5), which might decreases peak viscosity. These properties might help preserve the desired firm texture, might make Qulle powder suitable for pasta and noodle production, where and less breakdown during boiling (Aryee et al., 2006; Kolarič., et al., 2020). Breakdown viscosity, an indicator of paste stability under heat (Eke-Ejiofor, 2015), was lowest in Kello powder (9.5 RVU), suggesting strong resistance to granule disintegration and excellent paste stability. This property is particularly beneficial for heat-stable food applications such as sauces, soups, gravies, and custards (Kaur et al., 2007; Singh et al., 2007).
Setback viscosity which is linked to retrogradation tendencies (Eke-Ejiofor, 2015) was varied among the samples. Hawassa-4 cassava starch exhibited the highest setback viscosity (46.8 RVU), whereas Chichu and Qulle powders recorded the lowest values (2.5 RVU). The low setback viscosities of Chichu and Qulle may be attributed to their faster gelatinization rates, as indicated by their shorter pasting times (3.4 and 3.5 min, respectively; Table 5). Rapid gelatinization may limit the extent of amylose leaching into the paste matrix, thereby reducing the potential for molecular re-association during the cooling phase (Tester and Morrison 1990). Interestingly, despite having comparable amylose and amylopectin contents, Chichu and Hawassa-4 powders exhibited a large difference in setback viscosity (2.5 RVU vs. 22.40 RVU), suggesting that other structural and compositional factors may be influencing retrogradation behavior. Hawassa-4 may possess longer or more linear amylose chains and a more ordered amylopectin structure that facilitate retrogradation. Additionally, its higher fiber content could interact with starch molecules during heating and cooling, modifying the pasting profile (Wang et al., 2020). Improved starch granule integrity in Hawassa-4 may also enhance water absorption, contributing to higher setback viscosity. Since low setback viscosity is typically associated with reduced retrogradation and slower staling, Chichu and Qulle powders may be better suited for food products requiring extended shelf-life and freshness, such as injera.
The findings also revealed that the higher pasting temperature of cassava powder could be attributed to its small starch granule size, consistent with Charoenkul et al. (2011). This elevated pasting temperature could enhance the Maillard reaction during baking, thereby improving the browning and flavor profile of baked foods like cookies. Given these characteristics and other properties like higher oil holding capacity, powders derived Hawassa-4 cassava variety used in this study might be suited for cookie production.
Cassava starch gelatinization temperatures vary among different varieties, with Qulle, Hawassa-4, and Kello starches exhibiting the highest onset gelatinization temperature (Table 6). Higher onset gelatinization temperatures generally indicate greater thermal stability of starch granules, which can delay gelatinization during heating and may be associated with stronger granular structure. This behavior is also reflected in their pasting properties, where these samples exhibit higher peak viscosities, 173.5 RVU for Hawassa-4 starch, 163.2 RVU for Qulle starch and 125.5 RVU for Kello starch (Table 5). In terms of product development, starches with higher gelatinization temperatures are advantageous in applications requiring heat stability and controlled thickening, such as in canned or baked goods like cookies (BeMiller, 2011). On the other hand, starches with lower gelatinization temperatures (e.g., Chichu powder) may be more suitable for products that require rapid gelatinization and less retrogradation, such as injera, where extended softness and freshness are desirable (Mezgebe et al., 2020).
Enthalpy of gelatinization, which measures the energy required to disrupt the starch granules and transition them to an amorphous state during heating, varied significantly (p < 0.05) among the starches. Kello and Qulle starches exhibited the highest values (16.3 and 16.1 J/g, respectively), while their corresponding powders and Hawassa-4 and Chichu powders displayed lower enthalpy values. The higher enthalpy values for Kello and Qulle starches indicate that these starches possess a more tightly packed crystalline structure, requiring more energy to break the intermolecular forces during gelatinization (Wang and Copel, 2012). This characteristic is typically linked to higher amylose content, as amylose molecules tend to form stronger hydrogen bonds, contributing to the starch's structural integrity (Tester et al., 2004). In product development, starches with higher enthalpy values and higher amylose content, such as Kello and Qulle, are valuable for products that require firmness, stability, and moisture retention such as noodle products, gelled desserts, and bakery fillings where structural integrity during cooking and storage is critical (Singh et al., 2003).
This study confirms that Ethiopian cassava varieties exhibit distinct granule size, functional, pasting, and thermal properties influencing their suitability for various food applications. The smaller average granule size, higher WHC, lower amylose and greater swelling power of Hawassa-4 and Chichu varieties might makes these varieties preferable for production of baked foods with improved texture. Qulle powder with larger average granule size (10.47 µm) had reduced surface area for water interaction (Figure 1), higher pasting temperatures (70.6 °C) (Table 5), and lowest (80.3 RVU) peak viscosity. These properties might be valuable for preserve the desired firm texture, might make Qulle powder suitable for pasta and noodle production where structural integrity during cooking and storage is critical. Chichu cassava powder exhibits high swelling power, high solubility, lower onset gelatinization temperature, and the lowest setback viscosity. These functional properties suggest that Chichu powder may be well-suited for products requiring a softer texture, extended softness, and prolonged freshness, such as injera, the Ethiopian staple food. Hawassa-4 powder showed good water-holding capacity (2.7 mL/g), oil-holding capacity (2.2 mL/g), and a suitable pasting temperature (71.12 °C), might make it potentially preferable for cookie development. Further research on cassava root processing methods is recommended to expand the potential applications of these cassava varieties. Due to this, further studies are recommended to explore the impact of different cassava root preprocessing methods; this could help to explore additional uses of these Ethiopian cassava varieties.
Ethics clearance The study protocol was approved by the Ethical Committee of the Institutional Review Board (IRB) at the College of Medicine and Health Science (Record number: IRB/381/15).
Acknowledgements The authors would like to recognize the research and technology Vice president Office of the Hawassa University for funding this research through cassava thematic research project. The authors would like to acknowledge Hawassa agriculture research center for provision of cassava samples. The Authors would like to appreciate the cooperation and support of Laboratory of University of Applied Sciences Fakultät Gartenbau und Lebensmitteltechnologie, Freising, Germany, Laboratory of Ethiopian Institute of Agricultural Research, Hawassa University Food Micro Laboratory, Animal Science Laboratory, Laboratory of Mechanical, Chemical, Materials Engineering Adama Science and Technology University during experimental work.
Conflict of interest There are no conflicts of interest to declare.
