Potential stabilization effect of native and modified anchote (Coccinia abyssinica) starches in tomato sauce

ABSTRACT

 Starch is a prevalent functional component in food processing because due to its thickening capabilities. The aim of this study was to assess the potential stabilization effects of native, heat-moisture treated, and hydroxypropylated anchote starches in tomato sauce. Tomato sauce was made with different percentages (0%, 0.5%, 1%, and 1.5%) of native and modified anchote starch. A maximum 3.97% decrease in moisture content was observed in tomato sauce concentrated with 1.5% heat-moisture treated anchote starch. Significance differences were observed among tomato sauce samples in their proximate composition. The maximum lightness (L*) value was 29.23% in tomato sauce concentrated with 1.5% hydroxypropylated anchote starch, while the lowest was 26.2% for tomato sauce without starch. With increasing levels of starch used for thickening, b* increased, while the a* value decreased insignificantly. Sauce samples with 1.5% native anchote starch had the highest titratable acidity (0.64%) and total soluble solids (8.97%). Increased storage time resulted in a decrease in vitamin C content of all sauce samples. The addition of starch to tomato sauce resulted in a significant change in pasting qualities, with the highest peak viscosity (11287.69 cP) achieved at 1.5% native anchote starch. The highest (6.2 cm) and lowest (3.7 cm) Bostwick consistency was recorded for the control sauce and for the sauce concentrated with 1.5% native anchote starch. In general, although few undesirable characteristics resulted, especially the addition of modified anchote starch resulted in considerable quality attributes, and can be used as an alternative thickening agent in food processing.

KEYWORDS:

• Anchote starch
• tomato sauce
• physicochemical
• pasting properties
• rheological

Introduction

Tomato (Solanum lycopersicum L.) is an important vegetable worldwide and is consumed in both fresh and processed forms. Tomatoes belong to a seasonal crop of shrubs and belong to the family Solanacea.^[1] World tomato production in 2021 reached 391,850,000 tons.^[2] Tomatoes are rich in nutrients and functional compounds. The compounds in tomatoes include solanine (0.007%), saponins, folic acid, malic acid, citric acid, bioflavonoids (including lycopene, α- and β carotene), protein, fats, vitamins, minerals and histamine.^[3] Lycopene is one of the most abundant chemicals in tomatoes; 100 grams of tomato on average contains as much as 3–5 mg of lycopene. One of the methods of tomato processing is to make it into sauce. Tomato sauce can be made from crushed tomato fruit, which is then heated. Tomatoes are processed by preheating before being consumed to increase lycopene bioavailability in tomatoes.^[4]

In the majority of poor nations, postharvest loss is a significant obstacle to the production of tomatoes.^[5] Due to its high moisture content, tomatoes are a perishable crop with a limited shelf life of approximately 48 hours in tropical climates.^[6] To reduce poverty, increase revenue, and enhance food security in the world’s poorest nations, such as Ethiopia, postharvest losses are a critical concern.^[7] As a result, alternate processing and preservation approaches are critical. Preparing high-quality, safe, shelf-stable, inexpensive, and widely available tomato sauce from fresh tomato could be a solution. In the processing of turbid sauce, a tiny number of insoluble particles, such as proteins, pectin, lipids, hemicellulose, cellulose, and other minor components, remain. In hazy fruit sauces, it is impossible to obtain a brilliant, natural color.^[8] Additionally, sauce cloud loss is a condition in which customers disagree. It is thought that the presence of insoluble materials in clear beverages is a sign of deterioration. Colloidal suspensions in fruit sauces, on the other hand, are preferred because they add a distinctive flavor, color, and mouthfeel. To satisfy consumer demand, sauce turbidity must be maintained and improved.^[9]

Starch can be used as a stabilizer because it is organic and can represent synthetic stabilizers such as gelatin and carboxyl methyl cellulose (CMC).^[10] In comparison to other stabilizers such as proteins and non-starch polysaccharides (NSPs), starch has interesting pasting properties, swelling power and water solubility, and in vitro digestibility, allowing it to be used as a stabilizer in food processing involving high temperature and demanding high viscosity products.^[11]

Anchote (Coccinia abyssinica (Lam.) Cogn.) is a potentially productive and nutritious starchy tuberous crop native to Ethiopia, but it is only grown in the southwest. Anchote starch has comparable properties to potato and other tuber starches.^[12,13] Based on our previous research,^[14] starch from anchote primarily modified (heat-moisture treated and hydroxypropylated) showed important physicochemical, pasting, and thermal properties, allowing them to be used for product stabilizations such as jellies, sausage, and fruit pastes. There are many potential advantages of using anchote in different food applications. Furthermore, adopting anchote for various product developments can both motivate producers and offer a raw material choice for the food industry. Opportunities to increase anchote use might grow as a result.

Despite the fact that starch is widely used in yogurt preparation, research on the use of starch in fruit juice for stabilization is limited. Some authors^[15] presented their findings on the influence of anchote starch on the colloidal stability of pineapple juice, but the possible stabilization effect of native and modified anchote starch in tomato sauce has not been examined. Therefore, this study aimed to investigate the potential stabilization effects of adding various concentrations of native, heat-moisture treated, and hydroxypropylated anchote starch to fresh tomato sauce.

Materials and methods

Materials

Well-ripened tomato was collected from the Kilinto agricultural farm. Samples were placed in a mechanical refrigerator to prevent unnecessary changes until processing. Native anchote starch, heat-moisture treated anchote starch, and hydroxypropylated anchote starch from previous studies,^[14] made in the laboratory of Addis Ababa Science and Technology University were used. All of the chemicals and reagents used in this study were purchased from Zonaschem Trading Plc (Kirkos, Addis Ababa, Ethiopia) and were of analytical quality.

Tomato sauce preparation

With minor adjustments, tomato sauce was made according to the procedure given by.^[16] The equipment and containers used in the preparation of tomato sauce were cleaned, rinsed, and sterilized to reduce microbiological contamination. Four kilograms of fresh, well-matured tomato fruit acquired from the Kilinto agricultural farm were weighed, graded by maturity level, washed and soaked. After that, the soaked tomato was sliced and diced into small pieces for easy crushing and heating. The skins and stems were filtered, and the pulp was placed in a container for final product development. Ingredients were added following pulping. Onion, salt, sugar, garlic, vinegar, and Niger seed oil were the basic elements employed in the production of tomato sauce. The percentage of the ingredients used for the development of tomato sauce was determined according to a proprietary recipe and.^[16] Details of the proportions of the ingredients used for the production of tomato sauce are provided as supplementary material. After that, a mixture of pulp and added ingredients was mixed with various concentrations of anchote starch suspensions as mentioned in the experimental design (Table 1). The mixture was divided into 10 equal parts and treated with different concentrations of native, heat-moisture treated and hydroxypropylated anchote starch suspensions named control (T₀), sauce with 0.5% native anchote starch (T₁-NAS), sauce with 0.5% heat-moisture treated anchote starch (T₁-HMT), sauce with 0.5% hydroxypropylated anchote starch (T₁-HYPP), sauce with 1% native anchote starch (T₂-NAS), sauce with 1% heat-moisture-treated anchote starch (T₂-HMT), sauce with 1% hydroxypropylated anchote starch (T₂-HYPP), sauce with 1.5% native anchote starch (T₃-NAS), sauce with 1.5% heat-moisture treated anchote starch (T₃-HMT), and sauce with 1.5% hydroxypropylated anchote starch (T₃-HYPP) before being cooked at a temperature of 80°C for 30 min. Following cooking, the tomato paste was subjected to homogenization for the production of tomato sauce with smooth consistency. To prevent recontamination of tomato sauce, before cooling, the sauce was filled into containers that were previously sterilized.

Table 1. Experimental design for tomato sauce formulations with native and modified anchote starches.

Tomato sauce treatment	Anchote starch %
T0	-
T1-NAS	0.5
T1-HMT	0.5
T1-HYPP	0.5
T2-NAS	1
T2-HMT	1
T2-HYPP	1
T3-NAS	1.5
T3-HMT	1.5
T3-HYPP	1.5

Characterization of tomato sauce

Proximate analysis

The moisture, ash, crude protein, and crude fat contents of the prepared tomato were determined according to the method described by.^[17]

Color parameters

Color parameters L*, a*, b* of tomato sauce samples were determined using a colorimeter (NR110, Precision Colorimeter, China) according to the method described by.^[18]

Ascorbic acid

The vitamin C or ascorbic acid content of the sauce samples was evaluated using a simple iodometric titration approach modified slightly from.^[19] A 20 mL sauce sample, 5 mL HCl, and 5 mL KI solution were placed in an Erlenmeyer flask to titrate against 0.001 M KIO₃. The sauce was titrated three times and the average values of the titrant values were taken to calculate the vitamin C or ascorbic acid concentration. This was done on days 1, 5, and 10 after tomato sauce was produced.

Determination of pH

The pH of the sauce samples was determined using the method described by.^[20] One gram of tomato sauce was homogenized with one milliliter of distilled water and one milliliter of deionized water (pH 7). The pH of the sauce was measured using an electronic pH meter that had previously been calibrated with a pH 7 buffer solution.

Total soluble solids (TSSs)

With minor modifications, total soluble solids were determined using.^[21] Two drops of tomato sauce samples were placed on the refractometer’s prism (Digital refractometer, KRÜSS, Germany), which had been set to a temperature of 20°C.

Titratable acidity

The titratable acidity of tomato sauce was determined using a process suggested by.^[22] Sodium hydroxide (NaOH, 0.1 N) was used to titrate 15 mL of sample sauce to pH 8.1. The total titratable acidity of the sauce sample was calculated as a percentage of citric acid as follows.

(1) $Titratableacidity(\%\text{)=}\frac{\text{N}\times {\text{V}}_{\text{1}}\times {\text{Eq}}_{\text{wt}}}{{\text{V}}_{\text{2}}\times \text{1000}}\times \text{100}$(1)

where N is the normality of NaOH, $V_1$ is the volume (mL) of titrant/NaOH needed, $E{q}_{wt}$is the equivalent weight of predominant acid/citric acid (mg/mEq), $V_2$ is the volume of sample (mL) used, and 1000 is a factor relating mg to grams (mg/g).

Turbidity

The turbidity of tomato sauce was measured using the method proposed by.^[23] Serum cloudiness was used as a standard to assess the turbidity of tomato sauce. The cloud stability of centrifuged 25 ml tomato sauce samples (4000 rpm for 15 minutes) was determined using a UV spectrophotometer (UV-1800, Shimadzu, Japan) calibrated with distilled water to measure the absorbance at 750 nm. The turbidity of tomato sauce was measured in nephelometric turbidity units and correlated to absorbance at 750 nm according to the result suggested by.^[24]

Sedimentation

With minor adjustments, the sedimentation of the tomato sauce sample was assessed by the method described by.^[25] A 30 ml sample of tomato sauce was transferred to a 100 ml graduated tube and kept at room temperature. After that, the sedimentation progress was monitored for three weeks. The volume of the sediment was calculated as (total volume – serum phase). It was mathematically expressed as:

(2) $IS=\frac{V_{inf}}{V_{total}}$(2)

where $V_{inf}$ is the sediment volume (ml) and $V_{total}$ is the total volume of the sample (mL).

Rheological properties

Consistency

The consistency of tomato sauce was measured using a Bostwick consistometer (24 cm, Bostwick consistometer, Cam lab, United Kingdom) according to the recommendations by.^[26] The sample was placed in the compartment of the consistometer with the amount needed to fill the reservoir, and the measurement was performed at room temperature. The reservoir’s gate was opened, and after 30 seconds, the distance traveled by the sample’s leading edge was measured.

Flow curve test and viscosity

A rotational rheometer (CC27 SN480070, A&D company Ltd, Japan) was used to carry out the flow curve testing on the tomato sauce sample. This was accomplished using the methods outlined by.^[26] Within 5 minutes of testing, the sample was relaxed and thermostated at the specified measurement temperature. The sample was subjected to a programmed increasing and decreasing shear rate of 0–0.05 S⁻¹ at temperatures ranging from 10 to 60°C, with a 10°C interval, in less than 10 minutes. Data from a rheometer were gathered, and a graph of shear stress versus shear rate was generated to analyze the flow behavior of tomato sauce thickened with various concentrations of native, heat-moisture treated, and hydroxypropylated anchote starches (i.e., whether it is Newtonian or non-Newtonian).

Pasting properties

The pasting properties of tomato sauce samples thickened with various percentages of native, heat-moisture treated, and hydroxypropylated anchote starch were determined using a Rapid Visco-Analyzer (RVA 4500, Perten Instrument Ltd., Sweden). Tomato sauce samples (3 g, dry basis) were suspended in 25 ml of distilled water, equilibrated at 40°C for 1 min, and then heated to 95°C at a rate of 5°C/min for 9 min. The samples were refrigerated to 50°C at a rate of 5°C/min. To homogenize the samples, samples were subjected to stirring for 10 s at 960 rpm, and finally, the stir drive motor was lowered to 160 rpm for the rest of the test. Pasting property data generated by the Rapid Visco-Analyzer were exported to Origin18 software (USA, Northampton, Massachusetts, Origin Lab Co.), and graphic representation was drawn.

Microbiological analysis

With minor adjustments, microorganism counting was performed using the method described by^[27] with slight modifications. First, all materials needed for analysis were thoroughly cleaned and autoclaved. The microbial load was measured using serial dilutions up to 10⁻⁴. One milliliter of each sample was obtained and added to a 10⁻¹ serial dilution. Agar media (EN ISO 11,133) containing nutrients was placed onto the plate and allowed to solidify. Once the media had solidified, 0.1 mL of each sample’s proper dilution was spread out and plated normally between 10⁻² and 10⁻⁴. The samples were then incubated for 24 hrs at 37°C. Finally, colonies were counted using a colony counter machine. The following formula was used to determine the actual number of bacteria in the plates.

(3) $CF=\frac{Totalnumberofcolony\times inverseofDf}{Amountoftransered}$(3)

where Df = dilution factor, and CF = colony forum

Sensory property evaluations

The overall sensory acceptability of adding native and modified anchote starches to tomato sauce was evaluated by a panel of 20 untrained panelists from Addis Ababa Science and Technology University according to the method described by.^[28] The appearance, mouth feel, flavor, taste, and color of tomato sauce containing native and modified anchote starch were evaluated using a five-point hedonic scale ranging from 4.5–5 (liked very much), 3.5–4.49 (liked moderately), 2.5–3.49 (neither liked nor disliked), 1.5–2.49 (disliked moderately), and 1–1.49 (disliked very much).

Experimental design and Statistical analysis

The expermental design is detailed in Table 1. All experiments were performed in triplicate. Minitab 18 Statistical Software (USA, State College, Pennsylvania, Minitab, LLC) was used to perform analysis of variance (ANOVA) for triplicate experiments. The Tukey test was used to analyze the mean significant differences (P < .05).

Results and discussion

Proximate compositions

The proximate compositions of tomato sauce concentrated with varying percentages of native, heat-treated, and hydroxypropylated anchote starch are shown in Table 2. The moisture content of tomato sauce decreased with the addition of native and modified anchote starch. The tomato sauce with no starch added had the highest moisture content (69.62%), while the tomato sauce concentrated with 1.5% heat-moisture treated anchote starch had the lowest (65.65%). The lower moisture content of tomato sauce concentrated with heat-moisture treated anchote starch than that of concentrated with native and hydroxypropylated anchote starch is because heat-moisture treated anchote starch had lower moisture content than native and hydroxypropylated anchote starch.^[14]

Table 2. Proximate compositions of tomato sauce samples.

Sauce samples	Parameters (%)
	Moisture	Ash	Crude Protein	Crude Fat
T0	69.62 ± 0.40^a	3.02 ± 0.01^a	3.25 ± 0.02^g	0.46 ± 0.01^bc
T1-NAS	67.97 ± 0.40^bc	2.99 ± 0.01^a	3.56 ± 0.01^c	0.48 ± 0.01^b
T1-HMT	66.88 ± 0.06^def	2.89 ± 0.02^b	3.47 ± 0.01^d	0.47 ± 0.01^b
T1-HYPP	68.57 ± 0.39^b	2.82 ± 0.01^c	3.29 ± 0.02^fg	0.46 ± 0.01^bc
T2-NAS	67.32 ± 0.22^cde	2.88 ± 0.02^b	3.61 ± 0.03^b	0.51 ± 0.01^a
T2-HMT	66.56 ± 0.20^fg	2.78 ± 0.03^c	3.50 ± 0.02^d	0.48 ± 0.01^b
T2-HYPP	67.87 ± 0.06^c	2.70 ± 0.01^d	3.33 ± 0.01^f	0.47 ± 0.01^b
T3-NAS	66.65 ± 0.07^ef	2.71 ± 0.02^d	3.73 ± 0.01^a	0.53 ± 0.01^a
T3-HMT	65.65 ± 0.03^fg	2.63 ± 0.03^e	3.62 ± 0.02^b	0.51 ± 0.01^a
T3-HYPP	67.36 ± 0.06 ^cd	2.56 ± 0.02^f	3.42 ± 0.02^e	0.47 ± 0.01^b

mean ± SD; n = 3 Means that do not share a letter in the same column are significantly different (P < .05).

The protein content of tomato sauce samples ranged from 3.25%-3.73%. Nature (native, heat-moisture treated, and hydroxypropylated) and percentages of starch used for tomato sauce thickening resulted in a statistically significant difference (P < .05) in the protein content of the sauce samples. The slight decrease in the protein content of tomato sauce concentrated with heat- moisture treated and hydroxypropylated anchote starch over tomato sauce concentrated with native anchote starch could be attributed to a decrease in the protein content of starch during heat-treatment and hydroxypropylation.^[29] With the tomato sauce sample concentrated with 1.5% native anchote starch (T₃-NAS) at the top (0.53%) and the sauce sample with no starch added (T₀) at the bottom (0.46%), the fat content increased with increasing percentages of starch used for thickening in all starch types used for thickening. Surprisingly, increasing percentages of native and modified anchote starches used for thickening resulted in a slight decrease in the ash content of tomato sauce. Several authors^[29,30] reported that heat-moisture treatment and hydroxypropylation of starches greatly reduce the ash content of starches. As a result, adding starch with a low ash content to tomato sauce reduced the overall ash content, which is determined as a percentage of the starch and sauce mixture. A similar decrease in the ash content of tomato paste enriched with rice flour was reported by.^[31]

Color parameters

Color parameters (L*, a* and b*) of tomato sauce thickened with different percentages of native and modified anchote starches are given in Figure 1. With increasing levels of starch used for thickening, a significant difference (P < .05) in the L* value of tomato sauce was observed. The maximum L* value (29.23) was observed in a tomato sauce sample concentrated with 1.5% hydroxypropylated anchote starch (T3-HYPP), whereas the lowest (26.20) was observed in tomato sauce with no starch added (T0). Similarly, the b* value, the greatest measure of yellowness of the tomato sauce, also increased with increasing levels of starch used for thickening. It ranged from 13.92–16.24. The addition of heat-moisture treated anchote starch to tomato sauce showed a tremendous effect on the b* value of the sauce. The addition of native and modified anchote starch to tomato sauce, on the other hand, decreased the sauce’s a* value. Except for the control tomato sauce (T0), no significant variation (P > .05) in the a* value was found among tomato sauces thickened with varying amounts of native and modified anchote starches. The overall change in color parameters of tomato sauce after the addition of native, heat-moisture treated, and hydroxypropylated anchote starch could be attributed to the color parameters of the native starch, the Millard reaction during the hydrothermal process between reducing sugars from heated starch and amino groups in the protein resulting in change color parameters of heat-moisture treated starch, and the change in color parameters of hydroxypropylated anchote starch as a result of the elimination of various components such as protein, fat, and salt during hydroxypropylation.^[32,33]

Figure 1. Color parameters (L*, a* and b*) of tomato sauce samples.

Titratable acidity (TA) values

Titratable acidity is a measurement of total acidity in foods that is mostly useful in determining acid content for sensory description.^[22] A significant difference (P < .05) in titratable acidity between tomato sauce concentrated with native, heat-moisture treated, and hydroxypropylated anchote starch can be seen in Table 3. The concentration difference did not significantly affect the titratable acidity of the tomato sauce. It was 0.39%, 0.63%, 0.58%, 0.52%, 0.63%, 0.59%, 0.52%, 0.64%, 0.59%, and 0.55% for the control (T₀), sauce with 0.5% native anchote starch (T₁-NAS), sauce with 0.5% heat-moisture treated anchote starch (T₁-HMT), sauce with 0.5% hydroxypropylated anchote starch (T₁-HYPP), sauce with 1% native anchote starch (T₂-NAS), sauce with 1% heat-moisture-treated anchote starch (T₂-HMT), sauce with 1% hydroxypropylated anchote starch (T₂-HYPP), sauce with 1.5% native anchote starch (T₃-NAS), sauce with 1.5% heat-moisture treated anchote starch (T₃-HMT), and sauce with 1.5% hydroxypropylated anchote starch (T₃-HYPP), respectively. The highest titratable acidity (0.64%) was recorded for tomato sauce containing 1.5% native anchote starch, and the lowest (0.39%) was recorded for the sample sauce without the addition of any fraction of native and modified starches (control). The results showed that tomato sauce with a high pH value also had a high proportion of titratable acidity, indicating that pH and titratable acidity had a direct relationship for the tomato sauce sample. According to some authors,^[34] the titratable acidity of fruit juices is mostly determined by the waiting period before processing, the variety, the kind of acid present, and the additives used during processing. Because all sauce samples were made from the same variety, a change in the titratable acidity of the starches during thermal treatment and hydroxypropylation could be a plausible parameter influencing the titratable acidity of the tomato sauce. However,^[35] and^[36] found that the pH and titratable acidity of the Zobo drink and pineapple flavored with roselle powder had an inverse relationship. This could be due to the titratable acidity content of the native and modified anchote starch in tomato sauce, which causes the sauce’s titratable acidity to rise.

Table 3. Physicochemical properties of tomato sauce.

Sauce samples	Physicochemical properties
	TA (%)	pH	TSS (%)
T0	0.39 ± 1.88^c	3.75 ± 0.04^d	4.50 ± 0.10^h
T1-NAS	0.63 ± 3.01^a	6.01 ± 0.04^a	7.63 ± 0.15^c
T1-HMT	0.58 ± 2.79^ab	5.54 ± 0.01^b	5.43 ± 0.15^g
T1-HYPP	0.52 ± 1.97^b	4.88 ± 0.02^c	5.70 ± 0.10^fg
T2-NAS	0.63 ± 2.71^a	6.00 ± 0.03^a	8.43 ± 0.15^b
T2-HMT	0.59 ± 3.35^ab	5.56 ± 0.02^b	6.20 ± 0.10^e
T2-HYPP	0.52 ± 2.48^b	4.95 ± 0.02^c	5.80 ± 0.1^efg
T3-NAS	0.64 ± 3.06^a	6.11 ± 0.01^a	8.97 ± 0.21^a
T3-HMT	0.59 ± 2.67^ab	5.34 ± 0.02^b	6.83 ± 0.25^d
T3-HYPP	0.55 ± 1.30^b	4.93 ± 0.01^c	6.13 ± 0.21^ef

Mean ± SD; n = 3 Means that do not share a letter in the same column are significantly different (P < .05).

pH

pH can be described as the negative log (base 10) of the hydrogen ion concentration. For foods, it is not only a function of the type and concentration of acid present but also the concentration of ionized acid counterparts. It is a good indicator of the microbial stability of food products since the ability of microorganisms to grow in specific foods is more dependent on the concentration of free hydronium ions (H₃O⁺).^[22] Table 3 shows the pH values of tomato sauce samples as follows: 3.75, 6.01, 5.54, 4.88, 6.00, 5.56, 4.95,6.11, 5.34, and 4.93 for control (T₀) sauce, sauce with 0.5% native anchote starch (T₁-NAS), sauce with 0.5% heat-moisture treated anchote starch (T₁-HMT), sauce with 0.5% hydroxypropylated anchote starch (T₁-HYPP), sauce with 1% native anchote starch (T₂-NAS), sauce with 1% heat-moisture-treated anchote starch (T₂-HMT), sauce with 1% hydroxypropylated anchote starch (T₂-HYPP), sauce with 1.5% native anchote starch (T₃-NAS), sauce with 1.5% heat-moisture treated anchote starch (T₃-HMT), and sauce with 1.5% hydroxypropylated anchote starch (T₃-HYPP), respectively. The pH values of tomato sauce significantly varied (P < .05) with the nature of the starch used for concentration (control, native, heat-moisture treated, and hydroxypropylated). The pH ranged between 6.11 and 3.75. However, no significant difference (P > .05) was shown with increasing concentrations of starch. The lowest pH (3.75) value was observed for the control; in contrast, the highest (6.11) was recorded for the tomato sauce concentrated with 1.5% native anchote starch. A similar increase in the pH of tomato sauce concentrated with starch and carboxymethyl cellulose was reported by.^[37] The increased pH value of tomato sauce with increasing levels of starch used for thickening could be attributed to the large number of glucoses in starch, which is mostly neutral.^[38] Although the pH level of tomato sauce concentrated with native anchote is quite large, it is still below the optimum pH range (6.5–7) for microbial growth.^[39] Tomato sauce with a high pH value can also prevent gastric disease, uneasiness, and heart burns, which may be caused by the release of excess gastric acid and excess acid flow up of food pipes as a result of excess consumption of tomato products.^[40]

Total soluble solids (TSSs)

The component of fruit consisting of water soluble compounds such as glucose, sucrose, fructose, and water soluble protein is referred to as total soluble solid (TSS).^[41] The results from the statistical analysis showed a significant difference (p < .05) between tomato sauce treated with native, heat-moisture treated, and hydroxypropylated anchote starch (Table 3). The total soluble solid content ranged from 4.55%, 7.63%, 5.43%, 5.70%, 8.43%, 6.20%, 5.80%, 8.97%, 6.83%, and 6.13% for the control (T₀) sauce, sauce with 0.5% native anchote starch (T₁-NAS), sauce with 0.5% heat-moisture treated anchote starch (T₁-HMT), sauce with 0.5% hydroxypropylated anchote starch (T₁-HYPP), sauce with 1% native anchote starch (T₂-NAS), sauce with 1% heat-moisture-treated anchote starch (T₂-HMT), sauce with 1% hydroxypropylated anchote starch (T₂-HYPP), sauce with 1.5% native anchote starch (T₃-NAS), sauce with 1.5% heat-moisture treated anchote starch (T₃-HMT), and sauce with 1.5% hydroxypropylated anchote starch (T₃-HYPP), respectively. The sauce concentrated with 1.5% native anchote starch (T₃-NAS) had the highest total soluble solids (8.97%), whereas the control sauce (T₀) had the lowest (4.55%). Increasing the concentration of starch used for thickening has a substantial effect on the total soluble content of tomato sauce. Comparable results of total soluble solids were reported by^[42] for sauce aliquots from 12 Ethiopian tomatoes. The total soluble solid content of the control and sauce concentrated with different percentages of native and modified starch was within the recommended range (4.08–8.68) of processed tomatoes.^[43] Total soluble solid rises in tomato sauce thickened with different concentrations of native, heat-moisture treated, and hydroxypropylated anchote starches could be attributed to excessive moisture loss, which raises concentration, as well as carbohydrate breakdown to soluble sugars.^[44]

Turbidity

With increasing storage duration, the turbidity of tomato sauce dropped significantly (P < .05). The concentration and nature of starch added for thickening of the tomato sauce showed a significant impact on the turbidity of the sauce (Figure 2). Furthermore, the cloudiness of the sauce samples varied over time, indicating particle aggregation caused by attraction forces.

Figure 2. Turbidity/cloudiness of tomato sauce after 1, 2, and 3 weeks of storage.

During the first week of storage, the tomato sauce concentrated with 1.5% heat-moisture treated anchote starch had the maximum turbidity (549.73 NTU), while the control sauce had the lowest turbidity/cloudiness (222.48 NTU). The turbidity of the sauce significantly decreased with storage time, with the highest turbidity (450.94 NTU) observed for tomato sauce concentrated with 1.5% heat-moisture treated anchote starch and the lowest cloudiness (105.16 NTU) recorded for the control sauce at the third week of storage. The high turbidity value of tomato sauce, including native and modified anchote starches could be due to the presence of large proportions of tiny particles in the sauce because these particles are stable to sedimentation during centrifugation.^[45] During storage, however, these small particles might agglomerate and precipitate, resulting in turbidity reduction.^[46] Additionally,^[14] reported that the gel clarity of hydroxypropylated anchote starch was higher than that of native and heat-moisture treated anchote starch, which amply demonstrated the potential for hydroxypropylated anchote starch to improve paste clarity and reduce turbidity of the tomato sauce.

Sedimentation volume

The nature of starch added (native, heat-moisture treated, and hydroxypropylated), the percent of starch used for thickening, and the storage time all revealed significant differences in the sedimentation index except during the first week of storage (Figure 3). All sauce samples showed a small sedimentation index during the first week of storage. After two and three weeks of storage, the highest sedimentation index in terms of the nature of the starch used (19.89%, 32.89%) was recorded for tomato sauce thickened with 1.5% hydroxypropylated anchote starch, while the lowest was recorded (7.78%, 15.67%) for tomato sauce thickened with 1.5% heat-moisture treated anchote starch. After three weeks of storage, the results revealed that the control samples had the highest sedimentation index (41.33%).

Figure 3. The sedimentation index of tomato sauce after week 1, week 2, and week 3 of storage.

The sedimentation index increased rapidly with storage time and gradually decreased with increasing starch concentration used for thickening. The Stokes equation states that the particle sedimentation velocity is inversely related to the viscosity of the dispersed media.^[46] As a result, the increased viscosity prevents particle aggregation, resulting in a reduction in particle size in the suspension. This can be linked to the increased stability of the starch-added samples, and starch can be thought of as a key instrument in reducing sauce sedimentation. According to one study,^[15] the sedimentation index of pineapple sauce increased with storage duration and decreased with starch addition.

Ascorbic acid (vitamin C) content

The ascorbic acid content of tomato sauce concentrated with different concentrations of native, heat-moisture treated, and hydroxypropylated anchote starches during 15 days of storage is shown in Figure 4. During the first, fifth, and tenth days of production, respectively it was 17,16.3, and 14.5 (mg/100 g); 16.6, 16.1, and 14.4 (mg/100 g); 16.6, 16, and 15 (mg/100 g); 16.4, 16, and 14.9 (mg/100 g); 16, 16.1, and 14.5 (mg/100 g); 16, 15.6, and 14.5 (mg/100 g); 15.8, 15.5, and 14.5 (mg/100 g); 16.1, 13.5, and 13 (mg/100 g); 15.5, 13.5, 13 (mg/100 g); 14.8, 13.5, 13 (mg/100 g) for control (T₀) sauce, sauce with 0.5% native anchote starch (T₁-NAS), sauce with 0.5% heat-moisture treated anchote starch (T₁-HMT), sauce with 0.5% hydroxypropylated anchote starch (T₁-HYPP), sauce with 1% native anchote starch (T₂-NAS), sauce with 1% heat-moisture-treated anchote starch (T₂-HMT), sauce with 1% hydroxypropylated anchote starch (T₂-HYPP), sauce with 1.5% native anchote starch (T₃-NAS), sauce with 1.5% heat-moisture treated anchote starch (T₃-HMT), and sauce with 1.5% hydroxypropylated anchote starch (T₃-HYPP), respectively.

Figure 4. Ascorbic acid content variations with storage time.

There was no significant difference (P > .05) among sauce samples was shown for the nature of starch added except between the control sauce and sauce concentrated with 1.5% hydroxypropylated anchote starch (T₃-HYPP). However, at various storage durations, a significant change in ascorbic acid content was observed. A small effect of concentration difference was observed except for the sauce sample concentrated with 1.5% native, 1.5% hydroxypropylated, and 1.5% heat-moisture treated anchote starches.

When compared to the other samples, sauce samples concentrated with 1.5% hydroxypropylated and 1.5% heat-moisture treated anchote starches had the lowest ascorbic acid content (14.8 mg/100 g and 15.5 mg/100 g, respectively), while tomato sauce with no added starch (control) had the highest ascorbic acid level (14.5–17 mg/100 g). Generally, a gradual decrease in vitamin C content was observed for all sauce samples concentrated with different percentages of native, heat-moisture treated, and hydroxypropylated anchote starch with 10 days of storage time. This could be due to the presence of oxygen^[47] in the package, which can lead to serious oxidation reactions, and reaction kinetics, which may occur during storage time. Some authors^[48] have noted that the drop in vitamin C content of tomato sauce thickened with starch-based stabilizers could be attributed to low vitamin C content in starches, moisture content of the stabilizers, and a rise in storage temperature. During the production and storage of food products, significant amounts of ascorbic acid might be lost. In reality, ascorbic acid is easily damaged by heat and oxidation, making its preservation challenging.^[49] A similar decrease in the vitamin C content of tomato sauce concentrated with various of thickeners with storage time was reported by.^[31,50]

Rheological properties of tomato sauce

Consistency of tomato sauce

The simplest basic way to measure sauce consistency is to use the Bostwick Consistometer to measure the flow length (in centimeters) of a tomato sauce sample over a set period of time (typically 30 seconds). For the tomato sauce samples thickened with native and modified anchote starches the Bostwick measurement results are shown in Figure 5. According to the findings, the Bostwick consistency of control (T₀) sauce, sauce with 0.5% native anchote starch (T₁-NAS), sauce with 0.5% heat-moisture treated anchote starch (T₁-HMT), sauce with 0.5% hydroxypropylated anchote starch (T₁-HYPP), sauce with 1% native anchote starch (T₂-NAS), sauce with 1% heat-moisture-treated anchote starch (T₂-HMT), sauce with 1% hydroxypropylated anchote starch (T₂-HYPP), sauce with 1.5% native anchote starch (T₃-NAS), sauce with 1.5% heat-moisture treated anchote starch (T₃-HMT), and sauce with 1.5% hydroxypropylated anchote starch (T₃-HYPP) was 3.7 cm, 4.3 cm, 5 cm, 5.3 cm, 5.4 cm, 5.5 cm, 5.5 cm, 5.7 cm, 5.9 cm, and 6.2 cm, respectively. The tomato sauce sample thickened with 1.5% native anchote starch traveled the shortest distance (3.7 cm), while the tomato sauce sample thickened with 0% starch (control) traveled the longest distance (6.2 cm) within 30 seconds.

Figure 5. Bostwick consistency of tomato sauce samples.

The results show that the concentration difference and the nature of the starch added as a thickener affect the consistency of tomato sauce. From a previous study, pasting property profiles of native, heat-moisture treated, and hydroxypropylated anchote starch peak viscosity were reported as native > hydroxypropylated > heat-moisture treated anchote starches.^[14] This could be the primary factor influencing the Bostwick measurement. Tehrani and Ghandi^[51] reported that the presence of starch granules and their fragments, temperature, and extract content all have an impact on the consistency of tomato products. According to^[26] tomato sauce concentrates with total soluble solids ranging from 3.9–8.3 have Bostwick consistencies ranging from 2.5–6.7 cm. When the current study’s results are compared to the literature data, it can be stated that the consistency values of the tomato sauce thickened with anchote starch are within the range of consistency values reported by.^[26]

Viscosity

All tomato sauce samples thickened with anchote starch increased their viscosity as the percentage of anchote starch used increased (Figure 6). The nature of the starch used to thicken the sauce (native, heat-moisture treated, and hydroxypropylated) has a significant effect on the viscosity of tomato sauce. The viscosity profile of the sauce clearly shows the enhancement of the viscosity of tomato sauce with the addition of anchote starch.

Figure 6. Variation in tomato sauce viscosity with temperature.

The sauce sample thickened with 1.5% native anchote starch had the highest viscosity (679 to 10,833) mPa. s, while the control had the lowest viscosity (394.53 to 1234) mPa.s. The fact that tomato sauce thickened with native anchote starch has the highest viscosity could be related to the native anchote starch having the highest peak viscosity. Except for the tomato sauce sample thickened with heat-moisture treated anchote starch, which shows a relatively slight decrease in viscosity with increasing temperature, all sauce samples thickened with different percentages of native and modified starches show an exponential decrease in viscosity with increasing temperature. This shows its stability against high temperature and cooking, which may be due to the relatively low breakdown viscosity of heat-moisture treated anchote starch used as a thickener. The viscosity of fluids is influenced by temperature. When the temperature rises, the sample receives more energy, which reduces intermolecular interactions and internal friction during flow, lowering the system’s viscosity.^[52] Magerramov, Abdulagatov^[53] reported that there is a very strong effect of temperature and concentration on the viscosity of fruit juices. Overall, the high degree of starch polymerization is attributable to the overall rise in viscosity of tomato juice with increasing concentrations of native and modified anchote starch.^[54] The viscosity of Miya tomato sauce was reported to be 10.5 mPa.s by,^[55] which is significantly lower than the current finding. This could be due to differences in tomato sauce varieties, processing conditions, and ingredients and preservatives used during sauce development, as well as the temperature at which the viscosity is measured and the instrument used to measure it.

Flow behavior

Figure 7 depicts the flow behavior of tomato sauce thickened with various amounts of native and modified anchote starch. All sauce samples had a rise in shear stress as the shear rate was increased up to a certain point, after which their shear stress decreased as the shear rate was increased, resulting in a decrease in the apparent viscosity of the sauce. As the shear rate increases, the rate of disruption of the intermolecular entanglements becomes greater than the rate of reformation, leading to the resultant decrease in viscosity.^[56] As seen from the graph, tomato sauce thickened with 0% anchote starch seems Newtonian, as the relationship between shear stress and shear rate is quite linear. This, however, does not imply that it is Newtonian. Rather, it exhibits a quick shift in its viscosity with applied small shear stress, which is the strongest predictor of its poor resistance to external shear.

Figure 7. Flow behavior of tomato sauce samples thickened with anchote starches.

In contrast, the sauce sample concentrated with 1.5% heat moisture treated anchote starch showed the highest shear stress, indicating a high resistance to external shear. In comparison to tomato sauce samples with no starch added (T₀), sauce samples thickened with varying percentages of native and modified anchote starches showed increased shear stress. The amount and nature of starch added (NAS, HMT, and HYPP) had a substantial effect on the shear stress of tomato sauce samples. The improved shear stress of tomato sauce samples containing anchote starch (mostly modified anchote starches) could be attributed to the improved stabilities of heat-moisture treated and hydroxypropylated anchote starches against heating and shearing operations.^[57] Shear-thinning phenomena emerge from the orientation of solid particles of tomato paste along flow lines in products such as ketchup, i.e., a product with the structure of a suspension. The Bostwick consistency value and shear stress had an inverse relationship.^[58] Shear stress was lowest in the sauce sample with the longest flow length (T₀), and vice versa.

Pasting properties

Pasting properties of tomato sauces such as pasting temperature, peak, trough, break, final, setback viscosities and peak time, are given in Table 4. The pasting temperature of the tomato sauce samples ranged from 40.88–41.31°C. The pasting temperature of the sauce samples increased with increasing levels of starch used for thickening. According to the data in Table 4, the highest pasting temperature was recorded for the tomato sauce thickened with 1.5% heat-moisture treated anchote starch (T₃-HMT), while the lowest was that of tomato sauce with no starch added (T₀). Tomato sauce concentrated with hydroxypropylated anchote starch had the lowest pasting temperatures compared to tomato sauce concentrated with native and heat-moisture treated anchote starches. This could be attributed to a decrease in the strength of associative bonding within the micellar network during hydroxypropylation of anchote starch and an increase in crystallinity of heat-moisture treated anchote starch during hydrothermal treatment.^[59,60] The peak viscosity, which is the maximum viscosity attained when the sample is heated with excess water also ranged from 7235.70–11287.69 cP. The level and nature (native, heat-moisture treated and hydroxypropylated) of starch used for thickening tomato sauce showed large variations in the peak viscosity of the tomato sauce. When the effects of adding native, heat-treated, and hydroxypropylated anchote starches on the peak viscosity of tomato sauce were compared, tomato sauce concentrated with native anchote starch showed the highest, while tomato sauce concentrated with heat-moisture treated anchote starch showed the lowest. Native anchote starch is preferred to heat-moisture treated and hydroxypropylated anchote starch in terms of their effects on the peak viscosity of the tomato sauce. This could be due to the peak viscosity variation of native, heat-moisture treated and hydroxypropylated anchote starches as reported by.^[14] Peak time, the best indicator of the amount of time needed to reach peak viscosity, increased as the amount of starch used to thicken the tomato sauce increased as well. The maximum peak times for tomato sauce thickened with 1.5% native, heat-moisture-treated, and hydroxypropylated anchote starches were 5.90, 6.96, and 5.88 min, respectively. This indicates that tomato sauce concentrated with hydroxypropylated anchote starch is easier to cook than tomato sauce concentrated with native and heat-moisture treated anchote starch. The breakdown viscosity was another important pasting property parameter evaluated. It varied between 2452.7 and 3513.49 cP. Tomato sauce concentrated with heat-moisture treated and hydroxypropylated anchote starches had the lowest breakdown viscosity when compared to tomato sauce concentrated with native anchote starch, owing to the improved stabilities of heat-moisture treated and hydroxypropylated anchote starches against heating and shearing actions.^[57] Graphical representations of pasting property parameters are provided as supplemental resources in a separate file.

Table 4. Pasting properties of tomato sauce samples.

	Pasting properties
Sauce samples	Pasting T(^0C)	Peak 1 (cP)	Trough V(cP)	Break V (cP)	Final peak(cP)	Setback V (cP)	Peak time(min)
T0	40.88	7235.70	4725.36	2510.34	8680.11	3954.75	4.69
T1-NAS	40.92	9647.70	6644.68	3003.02	11573.60	4928.92	5.35
T1-HMT	41.05	7819.90	5366.20	2452.70	9393.90	4027.70	5.51
T1-HYPP	40.90	9085.96	6257.80	2828.16	10899.72	4641.92	5.20
T2-NAS	41.15	9738.19	6613.53	3031.18	11682.15	4975.14	5.72
T2-HMT	41.17	7917.23	5452.86	2464.37	9497.69	4044.83	5.86
T2-HYPP	41.08	9149.72	6301.71	2848.01	10976.21	4674.50	5.54
T3-NAS	41.27	11287.69	7774.20	3513.49	13540.97	5766.77	5.90
T3-HMT	41.31	8682.84	5980.16	2702.68	10416.13	4435.97	6.96
T3-HYPP	41.20	9602.46	6613.53	2988.93	11519.33	4905.80	5.88

Microbiological analysis

During 20 days of refrigerated storage, the microbial load of tomato sauce increased (Figure 8). The nature of the starch (native, heat-moisture treated, and hydroxypropylated) and the amount of starch added had no significant effect on the microbial load, but overall, starch addition decreased the microbial load present in the sauce compared to the control (sauce without any added starch). After 20 days of refrigerated storage, the maximum microbial count (3.24$\times$ 10⁴ CFU/mL) was observed for the control (sauce with no starch), while the minimum microbial count (6.97 $\times$ 10³ CFU/mL) was observed for tomato sauce concentrated with 1.5% hydroxypropylated anchote starch during the first day of sauce production. According to,^[61] the most influential elements influencing fruit juice deterioration are pH and water activity. The small decrease in the microbial count of tomato sauce thickened with native and modified anchote starch could be attributed to decreased water activity as a result of increased concentration. Tomato sauce with a high level of starch added had a lower microbial load, clearly indicating that the water activity of the tomato sauce had a strong influence on the microbiological count over the pH of the tomato sauce. The results showed higher values of colony forming units than the values recommended by,^[62] which were 1000 CFU/mL for the E. coli in unpasteurized fruit and vegetable sauces, even though this was only shown for the E. coli bacteria type. However, colony forming units during the 10 days of refrigerated storage are in the range of the recommended microbial load value applicable in Poland (10³ − 10⁴ CFU/mL). Several authors^[15] reported that increasing stabilizer levels reduced the microbial count in fruit juice.

Figure 8. Microbial load of 20-day old tomato sauce.

The Ethiopian Food and Drug Authority (EFDA) has provided only limited information on the maximum number of colony-forming units that can be acceptable in processed tomato sauces. The total number of microorganisms in fresh fruit and vegetable sauces varies significantly (from 2 to 7 log10 CFU/mL) depending on the technique of sauce production, the kind of fruit and vegetable cultivation, variety, and storage conditions.^[27] The high microbial load after 20 days of storage of tomato sauce could be due to the quality of the water used for dilution, raw materials, tomato sauce preparation equipment, airborne dust, packaging material quality, air entry during packaging (which could create a favorable environment for microbe growth and multiplications), and problems with aseptic conditions during sauce preparations in general.

Sensory analysis

The type of starch employed for thickening the sauce (native, heat-moisture treated, and hydroxypropylated), amount of starch used for thickening, and storage time showed a significant effect (P < .05) on the sensory characteristics of most sauce samples (Figures 9 and 10). Based on the panelist’s response, there were significant differences (P < .05) in mouth feel, which characterizes the interactions of acidity, flavor, and texture, among the tomato sauce samples, with the sauce sample concentrated with 1% hydroxypropylated anchote starch coming in first place (4.88) during the first day after production. However, after fourteen days of cold storage, mouth feel decreased by 18.24% when tomato sauce was concentrated with 1% hydroxypropylated anchote starch on the top. Tomato sauce thickened with various concentrations of native anchote starch received the lowest rank in terms of mouth feel both during the production date and after fourteen days of storage.

Figure 9. Sensory acceptability of tomato sauce on the first day of production.

Figure 10. Sensory acceptability of tomato sauce on the fourteenth day of production.

The flavor, which is another excellent attribute of drinking tomato sauce, differed significantly (P < .05) between all sauce samples concentrated with different percentages of native anchote starch, heat-moisture treated anchote starch, and hydroxypropylated anchote starch during the first day and fourteenth days of refrigerated storage. The highest value was awarded for the tomato sauce sample concentrated with 0.5% and 1% hydroxypropylated anchote starch, 4.91 and 3.93, during the first and fourteenth days of storage, respectively. Responses from the panelists also showed a significant difference (P < .05) in taste. The tomato sauce sample concentrated with 0.5% hydroxypropylated anchote starch ranked first (4.5), while the sauce sample concentrated with 1% native anchote starch ranked last (2.25) during the production date, and this value decreased to 3.57 and 2.1 after fourteen days of refrigerated storage for tomato sauce concentrated with 0.5% hydroxypropylated anchote starch and 1% native anchote starch respectively. This could be related to the acid and sugar content of the samples. As the main attribute of tomato sauce, taste is expected not to be too acidic, neutral, or basic.

It is well known that a fundamental determinant of customer preference for drinking tomato sauce is its appearance. Based on the panelists’ responses regarding the appearance of the sauce concentrated with various percentages of native anchote starch, heat-moisture treated starch, and hydroxypropylated starch, it can be concluded that the tomato sauce sample concentrated with various percentages of hydroxypropylated anchote starch displayed the highest preference among the other samples in terms of appearance. Sensory results also revealed that sauce concentrated with various concentrations of hydroxypropylated anchote starch received 1^st rank, with sauce concentrated with heat-moisture treated and native anchote starches second and last, respectively both during the production date and after fourteen days of refrigerated storage. Because the sensory features of tomato sauce are mostly determined by the raw material, processing conditions, and storage period,^[63] the addition of anchote starch produced acceptable sensory results.

During the fourteen days of production, the tomato sauce’s sensory characteristics and general acceptability decreased significantly. The color attribute of the sauce changed from 3.2–4.4 to 2.5–3.2, indicating that the color of the sauce changed during storage, and panelists responded to it. According to the radar chart below (Figure 7), the effect of the addition of starches on mouth feel, flavor and taste is clearly shown and the buffering property of starch helps to prevent excessive variation in acidity of the sauce. Alqahtani, Abdulsalam^[31] reported a similar improvement in the sensory characteristics of tomato paste enhanced with rice flour and a decrease in the sensory characteristics with storage days. Overall, the sensory investigation revealed that adding native and modified anchote starches to tomato sauce improves appearance, mouth feel, flavor, and taste to a degree. However, as the sauce color changed from red to pink, it lost its color acceptability.

Conclusion

The purpose of this study was to reveal the effect of adding native (NAS), heat-moisture treated (HMT), and hydroxypropylated (HYPP) anchote starches to fresh tomato sauce at various concentrations (i.e., 0.5%, 1%, and 1.5%) on its proximate, physicochemical and functional, rheological, microbiological, and sensory acceptance. The addition of native and modified anchote starches to tomato sauce resulted in a significant decrease in moisture and ash content but an increase in crude protein and crude fat content. The peak viscosity increased with the addition of all starch types, reaching a maximum of 11,287.69 cP for tomato sauce thickened with 1.5% native anchote starch. The decrease in the breakdown viscosity of tomato sauce thickened with modified anchote starches was a strong indication of its stability against heating and shearing. With increasing percentages of native, heat-moisture treated, and hydroxypropylated anchote starches added, the Bostwick consistency value was improved, and the viscosity of tomato sauce was enhanced. Tomato sauce thickened with varying quantities of native and modified starches showed no significant difference (P > .05) in microbial load. The sensory acceptability of tomato sauce was also improved by including native and modified starches at various concentrations. The overall findings of this study indicate that, despite some unwanted characteristics, anchote starch (mostly modified) can be used as a stabilizing ingredient in food processing that demands high viscosity, such as tomato sauce production.

Acknowledgments

The authors acknowledge Addis Ababa Science and Technology University’s Department of Food Process Engineering and Central Research Laboratory.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/10942912.2023.2293658

Additional information

Funding

This research was funded by Addis Ababa Science and Technology University, Addis Ababa, Ethiopia.