Spicy red pepper paste, locally known as Awaze, is a traditional popular spicy paste consumed in Ethiopia. The objective of this research was to determine the optimum proportion of red pepper, garlic, red onion and ginger in the preparation of Awaze paste. Mixture design was used to establish the appropriate proportion of red pepper, garlic, red onion and ginger. A D-optimal mixture experimental design with 15 runs was generated by design expert software within the constraint: 60–90% red pepper, 10–30% garlic, 5–20% red onion and 5–10% ginger. The physicochemical, mineral content and texture profile of Awaze paste were determined. Significant differences (p < 0.05) existed in color, ash, fiber content, viscosity, antioxidant activity, mineral and texture profile. Linear model for ash content, quadratic model for a* and antioxidant activity, special cubic model for fiber content significantly (p < 0.05) explained the effect of the components on the physicochemical quality of Awaze paste with high predicted R-squared (R2) value. The optimum formula of Awaze paste was a mixture containing 65.66% red pepper, 10% garlic, 19.086% red onion and 5.254% ginger. The optimum formula exhibited an antioxidant activity of 44.64%, ash content of 7.56%, color (a* value) of 18.3 and fiber content of 27.5%. There was a significant difference between Awaze paste produced from optimum formula and control (Household made Awaze).The study indicated that antioxidant activity, color value(a*), viscosity, ash content, fiber content and chewiness of Awaze paste are directly related to the proportion of red pepper, garlic, red onion and ginger.
Research Article
Optimization of functional spicy red pepper paste (Awaze) formulated from red pepper, garlic, red onion and ginger using optimal mixture design techniques
https://doi.org/10.21203/rs.3.rs-3128122/v1
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Awaze
Spice
Mixture design
Antioxidant activity
Ash content
Texture profile
Awaze is a fermented red pepper paste and one of the most important spice based traditional Ethiopian fermented food especially, in the northern part of the country. It is generally used as a sauce for stew (wot) making, with boiled potato and served with Injera during coffee ceremony and as seasoning in spicy foods. Spices are important ingredients of functional foods owing to their beneficial properties for human health. Their benefits are mainly related to the presence of bioactive compounds, antioxidant and anti-inflammatory activities. In Ethiopia, spices are commonly used in cuisine and medicine. The spices that are frequently used as main ingredients for the preparation of traditional spicy red pepper paste (Awaze) are red pepper, garlic, red onion and ginger[1]. These spices exert biological properties that are linked to maintaining good health and treating diseases [2].
Red pepper and red pepper based products possesses a high nutritional value, due to its content of different types of bioactive compounds such as antioxidants, minerals, fiber and vitamin C, specific aroma, flavor and color [3]. Dried and milled red peppers are used in meat, bakery products, instant soup, herb mixes, seasonings, and sauces in the food industry [4]. Garlic is rich source of potassium, phosphorous, magnesium, sodium, calcium, iron and selenium [5]. Garlic also contains vitamins especially thiamin with high bioavailability owing to some specific sulfur containing components. The nutritional, medicinal and sensory quality (taste) of onion makes it a very popular vegetable all over the world. It has high content of flavonoids, macro nutrients and micronutrients [6].
Red onion is a good source of fiber, crude protein, minerals, and antioxidants. Chemical analysis of onion showed high amount of oil(20.4%), fiber(22.4%), crude protein(24.8%), calcium(175/100 mg) and potassium(1010/100 mg) [7]. Ginger has health related properties that include antioxidant, anti-inflammatory, antimicrobial, anticancer, cardiovascular protective, respiratory protective, anti-obesity and anti-diabetic[8].Nutritional, sensorial quality and functional characteristics are important parameters to produce functional foods that possess beneficial effects for health and are accepted by consumers [9].
Mixture design has been applied as an important method for the development and optimization of foods. When several food ingredients are mixed, it is difficult to analyze foods by other available methods, determining their mixing ratio can be difficult. In a food product with several mixed ingredients, a mixture experiment design is used to identify ingredients that affect the product quality and to determine the optimal mixing ratio that maximize or minimize the response level of the ingredients [10].
In Ethiopia there are several traditionally prepared spice based foods such as red pepper paste (Awaze), stew(shero) wot, Mekelesha, Datta, Selejo and Bekolt. Spices used for the preparation of these spice based food are red onion, ginger, garlic, cardamom, fenugreek, clove, cinnamon, kemune, long pepper, coriander, thyme, nutmeg, basil, white cumin, black cumin, white cumin, rue, rosemary, ground pepper, balck mustared, safflowers, bean flour, potted water and salt [11].Different previous studies reported the physicochemical quality of red pepper paste but those studies reported only limited quality characteristics for laboratory made red pepper paste [12]. Only very few studies have reported the microbial quality characteristics of Awaze and Datta [13].
Ethiopian Awaze is a spice based red and thick paste made traditionally at house hold level. The main ingredients for Awaze are red pepper, garlic, red onion and ginger which are added in higher proportion, while cardamom, fenugreek, clove, cinnamon, kemune, long pepper, coriander, thyme, nutmeg, basil, white cumin, black cumin, white cumin, rue, rosemary and ground pepper are added in small proportion during the household preparation.
Health benefit and processing quality are very important factors that should be taken into account in developing functional foods[14]. An optimal mixture design is proved as an efficient tool to determine the best ingredient combination in food formulation. This method widely used to find the optimal formulation in varies food products by considering the best food characteristics [15].
There is lack of scientific information about the optimum proportion of the main gradients that are used for the preparation of Awaze. Many Ethiopian women at household use various proportions of red pepper, garlic, red onion and ginger during the preparation of Awaze. Accordingly, the present research aimed to determine optimal mixing ratio of ingredients by designing mixture experiments for the development of Awaze paste using red pepper, garlic, red onion and ginger as main ingredients.
Experimental material and sample preparation
Dried red pepper sample was collected from Bure, Amhara region, Ethiopia, the place is known for its high volume production of red pepper as described in [16].Matured red onion, ginger, and garlic were obtained from vegetable improvement center, Holeta Agricultural research center. The other ingredients (spices), cardamom, fenugreek, clove, cinnamon, kemune, long pepper, gewze, coriander, thyme, basil, white cumin, black cumin, rue, rosemary and ground pepper were purchased from Holeta spice market. The collected samples were transported to Holeta Agricultural research center, Food science and Nutrition research laboratory for Awaze paste product development. Analytical grade chemicals and distilled water have been used in various steps of Awaze paste preparation and physicochemical quality analysis.
Preparation of Awaze paste
The processing of Awaze paste ingredients was preformed following the traditional house hold made method as described in [13]. The dry spices were lightly roasted, mixed and milled using laboratory mill (Perten Instruments, Finland). Wet spices were powdered using wooden mortar and pestle, and dried using sun light. The drying took 3 to 5 days depending on the intensity of the sun light. The powder composite blends (independent variables) that contained red pepper, garlic, red onion and ginger were prepared using the formula shown in Table 2. Controlled variables that include 5 g cardamom, 5 g fenugreek, 2.5 g white cumin, 2.5 g basil, 1.25 g black cumin, 1.25 g mekelesha, 1 g rue, 0.5 g coriander, 0.4 g rosemary, 0.4 g thyme, 20 g salt were added constantly for each formulation. Then, Awaze paste was prepared by mixing 100 g composite powder with 150 ml of boiled water as shown in (Fig. 1). Control sample (household made) was collected from Amhara region, areas which the product frequently produced and consumed to compare with the formulated spicy red pepper paste (Awaze).
Experimental design
Maximum and minimum level of independent variables was first investigated by doing a preliminary survey at various household made Awaze paste producers in north west Amhara, areas which the product frequently produced and consumed. Based on the survey of the raw materials (ingredients) that are used in the preparation of Awaze paste, the ingredients that were used in a higher proportion were red pepper, red onion, garlic and ginger. The survey result indicated that above 90% of the respondents responded a maximum of 30% garlic, 20% red onion and 10% ginger is mixed with 90% red pepper to prepare Awaze paste. The respondents indicated that mixing more than 30% garlic and 10% ginger to make Awaze paste results a color change, whereas mixing more than 20% red onion decreases the shelf life of Awaze paste.
Accordingly, D-optimal mixture design within the constrained 60–90% of red pepper, 10–30% of garlic, 5–20% of red onion and 5–10% ginger powders generated 15 runs for mixing proportion. House hold made Awaze paste was used as a control. Fifty formulations were created and response parameters that was selected as best quality criteria for spicy red pepper paste (Awaze) include, color (a* value), viscosity, antioxidant activity, total ash content, fiber and chewiness of the product were evaluated (Tables 1 and 2).
|
Code |
Parameters |
Low level (%) |
High level (%) |
|---|---|---|---|
|
A |
Percentage of red pepper |
60 g |
90 g |
|
B |
Percentage of garlic |
10 g |
30 g |
|
C |
Percentage of red onion |
5 g |
20 g |
|
D |
Percentage of ginger |
5 g |
10 g |
|
Formulation |
Mixture components (%) |
|||
|---|---|---|---|---|
|
red pepper |
Garlic |
red onion |
ginger |
|
|
1 |
60 |
20.22 |
12.01 |
7.77 |
|
2 |
67.28 |
19.37 |
8.28 |
5.07 |
|
3 |
70.13 |
10.00 |
9.87 |
10 |
|
4 |
68.84 |
13.99 |
12.16 |
5.01 |
|
5 |
60 |
30.00 |
5.00 |
5 |
|
6 |
76.39 |
10.00 |
8.60 |
5.01 |
|
7 |
64.55 |
15.46 |
10.17 |
9.82 |
|
8 |
60 |
15.00 |
20.00 |
5 |
|
9 |
68.88 |
16.10 |
5.02 |
10 |
|
10 |
65.27 |
10.00 |
17.70 |
7.03 |
|
11 |
74.39 |
13.33 |
5.00 |
7.28 |
|
12 |
63.27 |
24.68 |
7.03 |
5.02 |
|
13 |
60 |
10.13 |
19.87 |
10 |
|
14 |
64.15 |
20.85 |
5.00 |
10 |
|
15 |
60 |
14.81 |
15.20 |
9.99 |
Evaluation of physicochemical property of Awaze paste
Physicochemical property color (L*, a*, b*) chroma, Hue Angele, ash content, fiber content, viscosity and antioxidant activity of spicy red paste (Awaze) was evaluated according to official methods.
Color Value (L*,a*,b*, chroma and hue angle)
The L*, a*, b* color values of the formulated paste (Awaze) were observed by Aeros Hunter colorimeter following the method described in [17]. The Aeros Hunter colorimeter was calibrated using the manufacturer’s standard white plate. The color scale used was L*,a*,b*,chroma(C*) and hue angle(H*). The coordinate L* measures values between white (100) to black (0). The redness (a*) color value measured values between red (+ 127) to green (-128), while b* measures between yellow (+ 127) to blue (-128). Chroma(C*) and hue angle (H*) were estimated from L*, a*, and b* values by using equations described in [18].
Where, C*= chroma, h*=hue angle, a*= redness, b*=yellowness
Total ash and crude fiber content
Total ash content and crude fiber were determined according to the association of official analytical chemists method[19] no: 923.03 and 962.09 respectively.
Viscosity
A three (3 g) dried powdered Awaze paste sample was dissolved in 5 ml distilled water, and the viscosity of the solution was determined using Brookfeild (model Lv-3, Middleboro, MA 02346, USA) set at 60 rpm and a temperature of 25°C[20].
DPPH radical scavenging activity
Methanolic extracts were prepared as reported previously by [21]. 400 mg of ground dried Awaze paste sample was placed in a 15 mL centrifuge tube with 5 mL of the solvent mixture MeOH: H2O (80:20, % v/v). The vials were then placed in a sonicator bath at ambient temperature for 30 min. The mixture was centrifuged and the supernatant was transferred into a 10 mL volumetric flask. The residue was re-suspended in 5 mL of MeOH:H2O (80:20, %v/v), gently mixed manually and sonicated for an additional 30 minute followed by centrifugation. The supernatant was combined with the initial extract and the volume of combined supernatant was made up to 10 mL with the extraction solvent and appropriate aliquots of extracts were filtered and assayed for antioxidant activity. Antioxidant activity was evaluated by measuring the radical scavenging effect of spicy red pepper paste (Awaze) sample methanolic extracts towards the 2,2-diphenyl-1-picrylhydracyl (DPPH) as reported previously by [22]. Five mL of a 0.1 mM methanol solution of DPPH was added to 20 µL of methanol extracts of Awaze paste samples. The tubes were allowed to stand at 27°C for 20 min. The decrease in absorbance at 517 nm was recorded in a spectrophotometer (Shimadzu UV-vis spectrophotometer 1900). Radical scavenging activity was expressed as inhibition percentage and was calculated using the following formula:
(%) Radical scavenging activity = (\(\frac{\text{A}\text{b}\text{s}\text{o}\text{r}\text{b}\text{a}\text{n}\text{c}\text{e} \text{c}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l} –\text{A}\text{b}\text{s}\text{o}\text{r}\text{b}\text{a}\text{n}\text{c}\text{e} \text{s}\text{a}\text{m}\text{p}\text{l}\text{e}}{\text{A}\text{b}\text{s}\text{o}\text{r}\text{b}\text{a}\text{n}\text{c}\text{e} \text{c}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l}}\)) x 100 (3)
Mineral content
The mineral contents (Fe, Zn, K, Ca and Mg) of the formulated sample and control sample were determined by atomic absorption spectrophotometer (Model: Agilent serious, America) by using the method [19]. A sample (0.5 g) was digested by using a muffle furnace at 550 degree centigrade for 5 hours until the residue ash became white. The ash sample was digested by using concentrated HCl. The digested sample was diluted up to 100 ml for mineral analysis.
Mineral content (ppm) = \(\frac{(\text{c}\text{o}\text{n}\text{c}. \text{A}\text{A}\text{S}-\text{b}\text{l}\text{a}\text{n}\text{k}) \text{T}\text{V} \text{d}\text{f} }{\text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{s}\text{a}\text{m}\text{p}\text{l}\text{e} }\) (4)
Where TV = Volume marked by 100ml volumetric flask, df = dilution factor
Texture Profile Analysis (TPA)
The texture profile of Awaze paste was measured through Texture Analyzer (model: TA. XT. Plus (Stable Micro Systems, UK), based on the method described in [23] using P-2 (cylindrical probe having 2 mm diameter) with pre-test speed, test speed were stated as 2,1, 2 mm /sec, respectively. Compression was distance mode of 5 mm and load cell was 50 kg. Two compressions in a raw were applied on the samples. The test produced the hardness, adhesiveness, cohesiveness, springiness, gumminess and chewiness of Awaze paste was measured. The texture profile of Awaze paste was determined using the following approaches:
Hardness (N)–is the maximum height of the first peak on the first compression
Adhesiveness (N.s)- describes the work for overcoming the force of attraction between the area of samples coming in contact each other
Cohesiveness- It is the ratio of the second compression to the first compression positive area
Springiness-is measured by dividing the distance of the detected height of the product on the second compression by the original compression distance.
Gumminess (N) - is the product of hardness and cohesiveness (strength required to chew dawn)
Chewiness(N) - is the product of gumminess and springiness (measure of the energy spent in the chew down process) as per the procedure of [24].
Data analysis
All the formulation values were presented as the mean ± standard deviation. Statistical analysis was performed using SPSS software (IBM, Chicago, IL, USA). One way analysis of variance and Duncan multiple range test (IBM SPSS Version 24) were used to explore the significant difference between the formulations with 95% confidence interval at (p<0.05). Numerical optimization was employed using statistical software Design-Expert 13.0® from Stat-Ease Inc. with criteria of maximum red onion while red pepper, garlic and ginger were kept in range. The contour plot for the selected variables were constructed to determine the best formulations for the chosen response.
Effect of red pepper, garlic, red onion and ginger proportion on color value of Awaze paste
The surface color of Awaze was measured using colorimeter and is presented in Table 3. There is a significant difference at (p<0.05) in L*, a*, b*, chroma, and hue angle for the formulated paste samples. The color values of lightness (L*), redness (a*), and yellowness (b*) of the products and control sample were in the range of 5.3-19.9, 5.85-23.4, 4.15-28.1, respectively. Color is an essential food quality for consumer acceptability and it is highly dependent on the ingredients used. The degree of redness (a*) was found to have a positive value ranged from 5.85- 23.4. The difference in color value of the formulated paste could be attributed to the differences in mixing ratio of the powders. The degree of color value difference in the paste sample is affected by the type of processing, packaging material and storage temperature[25]. Following an analysis of the 15 experimental results, the redness value (a*) reached maximal value of 23.4 for a mixing ratio of red pepper, garlic, red onion and ginger of 74.39, 13.3,5.0, and 7.28% respectively, where as the control sample (household made) had the lowest value (5.85). The low value of the control sample could be due to the long storage period of the product. A previous study on fermented red pepper based product revealed that the color value is associated with the microbial composition, which metabolites the complex and converts it into simple molecules responsible for a unique taste, aroma and color[26]. The color values of Awaze paste that was obtained in this study were in agreement with the study that was conducted on another red pepper based paste product (gochjang) [27]. Similar redness (a*) value for Korean red pepper paste was reported(15.13-31.34) [28]. Generally a higher value of a* indicates the degree of redness color of Awaze paste which is a criteria for best quality product.
The contour plot in Figure 2 indicated that Increasing in the mixing ratio of red pepper and red onion, the degree of redness was significantly increased. In contrast, an increase in garlic and ginger proportion decreased the color value of Awaze paste. The results showed the redness of Awaze paste increases with an increase in mixing ratio of red pepper and red onion.
Table 3. Effect of red pepper, garlic, red onion and ginger on color values of spicy red pepper paste (Awaze) and control sample(household made).
|
FM |
Mixture component (%) |
Color value |
|||||||
|
Red pepper (%) |
Garlic (%) |
Red onion (%) |
Ginger (%) |
Lightness(L*) |
Redness (a*) |
Yellowness (b*) |
chroma |
Hue angle |
|
|
1 |
60 |
20.22 |
12.01 |
7.77 |
13.8± 0.77 cd |
17.2± .49 bcde |
20.9± .85 abc |
27± .97 bc |
50.65± .33 a |
|
2 |
67.28 |
19.37 |
8.28 |
5.07 |
10.7± 0.49 cdef |
17.3± 1.06 bcde |
17.4± .92 bcdef |
24.5± 1.40 bcde |
45.14± .20 abcd |
|
3 |
70.13 |
10.00 |
9.87 |
10 |
13.5± 2.62 cd |
17.7± 1.06 bcde |
19.6± 1.70 bcd |
26.4± 1.97 bcd |
47.98± .73 ab |
|
4 |
68.84 |
13.99 |
12.16 |
5.01 |
18.5± 1.41 ab |
20.9± 1.34 ab |
22.4± 1.98 ab |
30.7± .53 ab |
47.01± 4.50 abc |
|
5 |
60 |
30.00 |
5.00 |
5 |
10.1±.92 def |
15.6± .28 cdef |
14.7± .92 cdef |
21.4± .83 cdef |
43.21± 1.29 abcde |
|
6 |
76.39 |
10.00 |
8.60 |
5.01 |
7.75± .92 fg |
14.7± 1.13 def |
11.6± 1.56 efg |
18.7± 1.85 def |
38.29± 1.50 de |
|
7 |
64.55 |
15.46 |
10.17 |
9.82 |
13.3± .64 cde |
17± .78 bcde |
18.3± 1.20 bcde |
24.9± 1.41 bcde |
47.06± .57 abc |
|
8 |
60 |
15.00 |
20.00 |
5 |
7.45± .21 fg |
14.2± .49 ef |
11.1± .21 efg |
18± .52 ef |
37.95± .50 de |
|
9 |
68.88 |
16.10 |
5.02 |
10 |
14.9± .28 bc |
17.2± .00 bcde |
20.1± .35 bcd |
26.4± .27 bcd |
49.36± .52 ab |
|
10 |
65.27 |
10.00 |
17.70 |
7.03 |
12.7± .57 cde |
18.3± .28 bcd |
18.3± .07 bcde |
25.9± .15 bcde |
44.85± .61 abcd |
|
11 |
74.39 |
13.33 |
5.00 |
7.28 |
19.9± 2.05 a |
23.4± 1.70 a |
28.1± 3.46 a |
36.5± 3.74 a |
50.05± 1.50 ab |
|
12 |
63.27 |
24.68 |
7.03 |
5.02 |
15± 1.27 bc |
19.3± 1.84 abc |
22.7± 4.88 ab |
29.8± 4.90 ab |
49.36± 3.43 ab |
|
13 |
60 |
10.13 |
19.87 |
10 |
8.95± .64 efg |
14± .28 ef |
14.1± 2.40 cdef |
19.9± 1.90 cdef |
44.98± 4.24 abcd |
|
14 |
64.15 |
20.85 |
5.00 |
10 |
8.05± .64 fg |
13.7± 1.13 ef |
12.6± 1.48 def |
18.6± 1.84 def |
42.44± 1.10 bcde |
|
15 |
60 |
14.81 |
15.20 |
9.99 |
5.4± .57 g |
11.6± 1.70 f |
9.7± 1.41 fg |
15.1± 2.2 fg |
40.03± .00 cde |
|
Control |
HF |
HF |
HF |
HF |
5.3± .28 g |
5.85± .06 g |
4.15± .21 g |
7.17± .06 g |
35.35±1.61e |
FM=formulations HF= (household made formulation)
Note: Data are means ± standard devation of the replicates. Values with different lowercase letters in the same column are significantly different (LSD, P<0.05)
Effect of red pepper, garlic, red onion and ginger proportion on ash content of Awaze paste
The ash content of Awaze paste samples showed significant difference for the formulated paste samples (p<0.05) (Table 4).The ash content indicates the mineral content in food samples. In this work, the ash content of the developed products and control sample were ranged 6.32- 9.94%. At a mixing ratio of 68.8% red pepper, 16.1% garlic, 5.02% red onion and 10% ginger, the ash content was the highest. The increase in the ash content may be due to the high amount of red pepper and ginger because red pepper and ginger are good source of minerals compared to garlic and red onion[1].The values in this study were lower than the reported values for commercial red pepper paste (5.1-21.1%)[29]However, lower ash content(2.83-3.1%) were also reported for red pepper paste that was prepared using different milling technique [30]. With an increase in mixing ratio of red pepper and garlic, the ash content of the product was increased (Figure 3).In contrast, increase in red onion and ginger significantly decreases the ash content of the paste.
Effect of red pepper, garlic, red onion and ginger on crude fiber content of Awaze paste
The blending ratios resulted in a significant change (p<0.05) in fiber content, with a value in the range of 16.86 to 29.06% (Table 4). The maximal values for fiber content were found for formulation with 76.39% red pepper, 10% garlic, 8.6% red onion, and 5.01% for ginger. The variation in the fiber content of the formulations is due to the difference in the blending ratio of the ingredients (spices).The fiber content found in this study was higher compared to the reported values of sweet red pepper paste(3.61%) [31]. Based on the contour plot, the fiber content of Awaze paste was increased with an increase in mixing ratio of red pepper, red onion and ginger increases as shown in (Figure 4).
Effect of red pepper, garlic, red onion and ginger proportion on viscosity of Awaze paste
The result indicated that the viscosity of the formulated paste was significantly (p<0.05) (Table 4).Viscosity is an important parameter for texture of food products including food and condiment pastes. The viscosity of the formulations and control sample was in the range of 71-125.5 cps. The highest viscosity was observed at a mixing ratio of 64.55% red pepper, 15.46 % garlic, 10.17% red onion, and 9.82% for ginger. This could be due to the relatively higher ratio of ginger and red onion because ginger and red onion had higher viscosity compared to red pepper and garlic[1].The viscosity values found in this study are lower compared to the reported values of onion paste (396-398 cps) [32].
Effect of red pepper, garlic, red onion and ginger on antioxidant activity of Awaze paste
The blending ratio resulted in a significant change (p<0.05) in the antioxidant activity of the formulated paste. Total antioxidant activity is an important parameter in establishing the health functionality of a vegetable product. The antioxidant activity of the formulated product (free radical scavenging activity towards DPPH) was observed at 20 µL concentration (Table 4). The antioxidant activity (free radical scavenging activity towards DPPH) was in the range of 34.24-54.13% (% inhibition) for all formulation at concentration of 20 µL. The highest antioxidant activity of 54.13% was found for formulations that contained 60% red pepper, 20.2% garlic, 12.01% red onion and 7.77% ginger. The lowest antioxidant activity of 34.24% was found for formulations that contained 68.84% red pepper, 13.99% garlic, 12.12% red onion and 5.01% ginger, it may be due to the relatively low proportion of garlic in the formulation. This report is in agreement with the study that reported an antioxidant activity in the range of 30-90% for different spices at different concentration[33]. A previous study obtained an antioxidant activity of hot and sweet red pepper paste in the range 40-90%[34], which is higher than the result of the current study.
As shown in Figure 5, as the mixing ratio of red pepper and ginger increases the percentage of free radical scavenging was significantly increased. As the mixing ratio red onion was increased, the percentage of free radical scavenging was decreased. The percentage of free radical was increased with an increase of the ratio between garlic and red pepper.
Table 4. Effect of red pepper, garlic, red onion and ginger on Physico chemical property of formulated spicy red pepper paste (Awaze) and control sample(household made).
|
FM |
Mixture component (%) |
Physico chemical quality |
||||||
|
Red pepper (%) |
Garlic (%) |
Red onion (%) |
Ginger (%) |
Ash (%) |
Fiber (%) |
Viscosity (cps) |
RSA% at 20 µl |
|
|
1 |
60 |
20.22 |
12.01 |
7.77 |
8.67± 0.22 de |
18.86±0.52 h |
102± 1.4 cd |
54.13± 2.14 a |
|
2 |
67.28 |
19.37 |
8.28 |
5.07 |
6.89± 0.03 h |
24.22±0.33 ef |
110± 2.83 bc |
42.44± 0.08 abcde |
|
3 |
70.13 |
10.00 |
9.87 |
10 |
6.87± 0.04 h |
14.60±0.54 i |
121± 2.83 a |
48.48± 1.91 abcd |
|
4 |
68.84 |
13.99 |
12.16 |
5.01 |
8.25± 0.08 ef |
21.35±0.21 g |
76.5± 2.12 ghi |
34.24± 1.07 e |
|
5 |
60 |
30.00 |
5.00 |
5 |
9.26± 0.06 bc |
18.68±0.27 h |
111.5± 0.7 b |
48.49± 0.37 abcd |
|
6 |
76.39 |
10.00 |
8.60 |
5.01 |
8.80± 0.04 d |
29.06±0.48 a |
89.5± 2.12 ef |
44.98± 0.8 abcde |
|
7 |
64.55 |
15.46 |
10.17 |
9.82 |
7.79±0.03 g |
27.50±0.01 abc |
125.5± 2.12 a |
48.13± 2.36 abcd |
|
8 |
60 |
15.00 |
20.00 |
5 |
7.90± 0.08 fg |
24.16±0.46 ef |
93.5± 0.71 e |
51.10± 1.82 abc |
|
9 |
68.88 |
16.10 |
5.02 |
10 |
9.94± 0.06 a |
22.64±0.47 fg |
91.5± 2.12 ef |
48.51± 0.96 abcd |
|
10 |
65.27 |
10.00 |
17.70 |
7.03 |
7.56±0.07 g |
27.55±0.61 abc |
104.5± 2.1 bc |
44.64± 1.18 abcde |
|
11 |
74.39 |
13.33 |
5.00 |
7.28 |
8.84± 0.02 cd |
27.90±0.83 ab |
78.5± 2.12 i |
44.79± 1.61 abcde |
|
12 |
63.27 |
24.68 |
7.03 |
5.02 |
9.40± 0.03 b |
22.14±0.23 g |
71± 1.41 gh |
40.54± 1.29 cde |
|
13 |
60 |
10.13 |
19.87 |
10 |
6.32± 0.05 i |
19.39±0.10 h |
68.5± 0.71 hi |
33.56± 0.96 e |
|
14 |
64.15 |
20.85 |
5.00 |
10 |
7.86±0.04 fg |
25.12±0.28 de |
76.5± 2.12 ghi |
52.99± 2.68 ab |
|
15 |
60 |
14.81 |
15.20 |
9.99 |
7.81±0.02 g |
26.58±0.49 bcd |
95.5± 2.12 de |
39.14± 1.12 de |
|
Control |
HF |
HF |
HF |
HF |
7.82±0.308 g |
25.90±0.14 cde |
84.5± 3.50 fg |
43.69± 1.44 abcde |
FM=formulations HF= (household made formulation), RSA=free radical scavenging activity
Note: Data are means ± standard deviation of the replicates. Values with different lowercase letters in the same column are significantly different (LSD, P<0.05)
Effect of red pepper, garlic, red onion and ginger proportion on mineral contents of Awaze paste
The result indicated a significant change of mineral contents(Fe, Zn, K, Ca and Mg) for the formulations and control sample (p<0.05) (Table 5).The formulated spicy red pepper paste (Awaze) had mean values of Fe, Zn, K, Ca and Mg in the range of 36.54-108.82, 1.72-26.93, 913.34-2783.32,28.09-92.27 and 73.48-198.6 mg/100g respectively. Formulation 76.39% red pepper, 10% garlic, 8.6% red onion and 5.01% for ginger had highest Fe and Zn content 108.82 and 26.93 mg/100g respectively, this may be due to the high proportion of red pepper and red onion. Formulation 63.27% red pepper, 24.68% garlic, 7.03% red onion and 5.02% for ginger had highest K content with the value 2783.32 mg/100g that is due to the high proportion of red onion. The control sample had higher Ca content 92.27 mg/100g and lower K content (913.4 mg/100g) and Mg content (73.5 mg/100g) compared to the formulations of this study.
At mixing ratio of 60% red pepper, 10.13% garlic, 19.87% red onion and 10% for ginger the concentration of Mg had the highest value (198.68 mg/100g). A previous studies on red paper paste reported Fe content in the range of 13-35 mg/100g and zinc content in the range of 3.3-10 mg/100g[29] which is lower than the results of the current study. These findings imply Fe and Zn content in the formulated paste is a good input for the food industry that produces condiment based paste products.
Table 5. Effect of red pepper, garlic, red onion and ginger on mineral contents (mg/100g) of formulated spicy red pepper paste (Awaze) and control sample(household made)
|
FM |
Mixture component (%) |
Mineral content(mg/100g) |
|||||||
|
Red pepper (%) |
Garlic (%) |
Red onion (%) |
Ginger (%) |
Fe |
Zn |
K |
Ca |
Mg |
|
|
1 |
60 |
20.22 |
12.01 |
7.77 |
65.08± 0.14 d |
3.26±0.32 g |
2291.3± 1.28 h |
45.67± 0.8 e |
174.85± 0.63 g |
|
2 |
67.28 |
19.37 |
8.28 |
5.07 |
47.62± 0.59 h |
12.25±0.12 b |
2367.17± 1.16 f |
63.7± 0.53 f |
169.55± 0.49 c |
|
3 |
70.13 |
10.00 |
9.87 |
10 |
61.43± 0.51 f |
11.42±0.08 c |
2496.22± 0.27 e |
49.32± 0.33 b |
194.62± 0.59 f |
|
4 |
68.84 |
13.99 |
12.16 |
5.01 |
49.22± 0.11 h |
4.52±0.03 f |
2191.39± 0.04 k |
40.41± 0.24 i |
157.08± 0.078 j |
|
5 |
60 |
30.00 |
5.00 |
5 |
35.59± 0.12 k |
1.86±0.09 jk |
2270.82± 0.01 i |
42.59± 0.2 k |
143.37± 0.76 hi |
|
6 |
76.39 |
10.00 |
8.60 |
5.01 |
108.82± 0.82 a |
26.93±0.16 a |
2314.15± 0.31 g |
59.24± 0.11 e |
174.79± 0.04 d |
|
7 |
64.55 |
15.46 |
10.17 |
9.82 |
62.82± 0.02 ef |
8.57±0.27 d |
2533.27± 0.06 d |
72.27± 0.09 c |
192.14± 0.32 b |
|
8 |
60 |
15.00 |
20.00 |
5 |
73.83± 0.01 b |
3.11±0.08 gh |
2556.17± 0.14 c |
43.61± 0.41 e |
176.01± 0.06 h |
|
9 |
68.88 |
16.10 |
5.02 |
10 |
63.36± 0.64 e |
5.6±0.12 e |
2142.92± 0.10 l |
28.09± 0.02 g |
164.2± 0.05 n |
|
10 |
65.27 |
10.00 |
17.70 |
7.03 |
45.37± 0.74 i |
1.72±0.09 k |
1991.77± 0.2 m |
42.2± 0.14 c |
132.66± 0.55 i |
|
11 |
74.39 |
13.33 |
5.00 |
7.28 |
59.61± 0.07 g |
3.59±0.12 g |
2580.9± 0.07 b |
35.6± 0.05 h |
161.29± 0.22 l |
|
12 |
63.27 |
24.68 |
7.03 |
5.02 |
71.91± 0.08 c |
2.5±0.01 hi |
2783.32± 0.01 a |
58.07± 0.01 d |
186.81± 0.20 d |
|
13 |
60 |
10.13 |
19.87 |
10 |
72.34± 0.11 bc |
3.58±0.05 g |
2313.4± 0.21 g |
54.28± 0.1 a |
198.68± 0.23 e |
|
14 |
64.15 |
20.85 |
5.00 |
10 |
36.54± 0.47 k |
3.51±0.06 g |
2190.82± 0.06 k |
38.49± 0.43 c |
192.12± 0.72 k |
|
15 |
60 |
14.81 |
15.20 |
9.99 |
41.51± 0.29 j |
2.43±0.08 ij |
2256.32± 0.10 j |
32.12± 0.05 j |
148.13± 0.57 m |
|
Control |
HF |
HF |
HF |
HF |
58.68± 0.48 g |
4.63± 0.13 f |
913.34± 0.19 n |
92.27± 013 m |
73.48± 0.55 a |
FM=formulations HF= (household made formulation)
Note: Data are means ± standard devation of the replicates. Values with different lowercase letters in the same column are significantly different (LSD, P<0.05)
Effect of red pepper, garlic, red onion and ginger proportion on texture profile of Awaze paste
The textural property of Awaze paste is shown in Table 6. The result showed that the blending ratio of the four ingredient powders (red pepper, garlic, red onion and ginger)had a significant (p<0.05) effect on the textural property of Awaze paste. Hardness value of the formulation with 60% red pepper, 14.81% garlic, 15.2% red onion and 9.9% ginger had the highest value(55.09 g) that was due to the highest proportion of garlic and ginger. Cohesiveness indicates the strength of the internal bonds in making of Awaze paste. As seen from Table 6, cohesiveness of the formulation was in the range of 0.40-0.78. The highest cohesiveness score was obtained for formulation with 67.28% red pepper, 19.37% garlic, 8.28% ginger, 5.05% ginger which contained relatively high proportion of red pepper and garlic.
The range of springiness score of the formulations was 0.22-1.5. Formulation with 60% red pepper, 15% garlic, 20% red onion, and 5.0% ginger had the highest springiness score(1.5) that corresponded to high proportions of red pepper and ginger during preparation of Awaze paste. Gumminess score of the formulation were in the range of 5.23-17.32 g, whereas the highest gumminess value was obtained for formulation with 63.27% red pepper, 24.68 % garlic, 7.03% red onion, and 5.02% ginger which was prepared from high proportion of red onion and ginger. Chewiness is a function of hardness. As seen from Table 6, chewiness score of formulation with 60% red pepper, 15% garlic, 20% red onion and 5% ginger was the highest (17.62 g).
Another study report on the texture profile for miser paste [35],observed higher values compared to the texture profile of red pepper paste (Awaze) of the current study
Table 6. Effect of red pepper, garlic, red onion and ginger on texture profile of formulated spicy red pepper paste (Awaze) and control sample(household made).
|
FM |
Mixture component (%) |
Texture profile |
|
|||||||
|
Red pepper (%) |
Garlic (%) |
Red onion (%) |
Ginger (%) |
Hardness (g) |
Adhesiveness (g.s) |
Cohesive ness |
Spring iness |
Gumminess (g) |
Chew iness(g) |
|
|
1 |
60 |
20.22 |
12.01 |
7.77 |
8.88±.19 fg |
-6.06±.36 a |
.68±.06 ab |
0.95±. 007b |
6.63±.16 b |
6.30±.10 bc |
|
2 |
67.28 |
19.37 |
8.28 |
5.07 |
8.48±.37 g |
-6.56±.08 abc |
.78±.02 a |
0.88±.03 bc |
7.39±.30 b |
6.54±.52 bc |
|
3 |
70.13 |
10.00 |
9.87 |
10 |
13.36±.77 def |
-7.49±.35 abcd |
.57±.01 bcd |
0.5±.028 def |
5.23±.28 b |
2.63±.30 c |
|
4 |
68.84 |
13.99 |
12.16 |
5.01 |
11.35±.64 efg |
-6.29±.73 ab |
.56±.04 bcd |
0.7±.1 bcde |
6.50±1.54 b |
4.70±2.02 c |
|
5 |
60 |
30.00 |
5.00 |
5 |
13.62±1.22 de |
-8.55±.47 bcd |
.63±.02 abc |
0.7±0.007 bcde |
7.90±.25 b |
5.54±.69 c |
|
6 |
76.39 |
10.00 |
8.60 |
5.01 |
14.43±.69 de |
-9.07±.47 d |
.63±.06 abc |
0.7± 0.007 bcde |
8.43±1.41 ab |
6.03±1.65 c |
|
7 |
64.55 |
15.46 |
10.17 |
9.82 |
10.11±.55 efg |
-6.31±.21 ab |
.63±.05 abcd |
0.83±.007 bcd |
6.95±.53 b |
5.82±.52 c |
|
8 |
60 |
15.00 |
20.00 |
5 |
16.33±.04 d |
-7.78±1.21 abcd |
.48±.08 de |
1.5±.0.03 a |
11.69±.72 ab |
17.62±1.44 a |
|
9 |
68.88 |
16.10 |
5.02 |
10 |
12.57±.13 defg |
-7.37±.27 abcd |
.59±.03 bcd |
0.53±.08 cdef |
5.23±1.17 b |
2.84±1.08 c |
|
10 |
65.27 |
10.00 |
17.70 |
7.03 |
23.59±1.29 c |
-13.15±.30 ef |
.56±.04 bcd |
0.54±0.10 cdef |
11.89±1.93 ab |
6.57±2.25 bc |
|
11 |
74.39 |
13.33 |
5.00 |
7.28 |
28.68±2.08 b |
-16.34±.73 g |
.57±.01 bcd |
0.41±0.12 ef |
10.20±2.63 ab |
4.34±2.37 c |
|
12 |
63.27 |
24.68 |
7.03 |
5.02 |
25.41±1.73 bc |
-14.01±1.28 f |
.55±.01 bcd |
0.76±0.07 bcd |
17.34±2.69 a |
13.41±3.45 ab |
|
13 |
60 |
10.13 |
19.87 |
10 |
21.71±.24 c |
-11.48±.30 e |
.53±.02 cde |
0.64±.02 bcde |
11.01±.39 ab |
7.05±.56 bc |
|
14 |
64.15 |
20.85 |
5.00 |
10 |
15.96±.90 d |
-8.66±.07 cd |
.55±.02 bcde |
0.62±.17 bcde |
7.58±2.83 b |
4.96±3.10 c |
|
15 |
60 |
14.81 |
15.20 |
9.99 |
55.09±2.78 a |
-21.77±.22 h |
.40±.02 e |
0.22±0.14 f |
10.79±6.83 ab |
2.87±3.04 c |
|
Control |
HF |
HF |
HF |
HF |
14.12±.06 de |
-7.34±.30 abcd |
.52±.03 cde |
0.63±.0.02 bcde |
5.34±.05 b |
3.41±.15 c |
FM=formulations HF= (household made formulation)
Note: Data are means ± standard devation of the replicates. Values with different lowercase letters in the same column are significantly different (LSD, P<0.05)
Model development
Independent and dependent variables were fitted to linear, quadratic and special cubic models (Table 7). To check goodness of model fit, residual plots were created. The best model has low standard deviation, high predicted R-squared (R2), low predicted sum of square and lack of fit (P>0.05)[36].Linear model was found to be the best fit for ash content and chewiness. Quadratic model was found to be the best fit for color (a*) and free radical scavenging activity. Special cubic model was found to be the best fit for fiber content (R2=0.98) (Table 7).
Table 7. The predicted models to experimental data in D-optimal mixtures design for the dependent variables of spicy red pepper paste (Awaze)
|
Response |
model |
F-value |
Lack of fit(p>0.05) |
R2 |
|
Ash content |
linear |
2.73 |
0.0944 |
0.42 |
|
Chewiness |
linear |
4.23 |
0.0323 |
0.535 |
|
Color(a*) |
quadratic |
2.88 |
0.1571 |
0.83 |
|
Percentage of free radical scavenging activity |
quadratic |
2.66 |
0.1118 |
0.82 |
|
Fiber content |
Special cubic |
6.44 |
0.2366 |
0.98 |
Optimization
An optimization of Awaze paste formulation was using the method of [37]. The optimization was done to develop a high quality Awaze paste with the selected important parameters, including color (a* value), antioxidant activity, viscosity, ash content, fiber content and chewiness (Table 8). During numerical optimization an attempt was made to maximize all the response. The ingredient red pepper, garlic and ginger was set to the range while red onion was set to the maximum. High relative importance of “5” was assigned to antioxidant activity and color (a*). High relative importance of “3” was assigned to ash content. High relative importance of “2” was assigned to viscosity, fiber content and chewiness. The numerical optimization showed that Awaze paste made from 65.66% red pepper, 10% garlic, 19.086% red onion and 5.254% ginger achieved the best desirability (0.561).The predicted response values for color(a* value), viscosity, ash, fiber, chewiness, and antioxidant activity for this optimal formulation were 21.56, 94.36 cps, 8.3%, 24.03%, 6.88 g, and 44.3% respectively (Table 8).
Verification of the model
The predicted optimum formulation was verified using an independent real formulation study. The comparison between the predicted (expected) and real values of Awaze paste for the selected parameters are shown in (Table 8). The real product is shown in (Figure 6). The predicted and verified values of the analyzed responses did not differ statistically as the verified values were included in 95% confidence interval and prediction interval range.
Table 8. Predicted and verified values of spicy red pepper paste (Awaze) optimized formula.
|
Response |
Optimum formula |
|
|
|
Desirability |
|||||
|
65.66% red pepper + 10% garlic + 19.086% red onion+ 5.254% ginger |
|
|||||||||
|
Predicted value |
Verified value |
Low 95% CI |
High 95% CI |
Low 95% PI |
High 95% PI |
0.561 |
||||
|
Color(a*) |
21.57 |
18.30 |
17.96 |
25.17 |
15.23 |
27.91 |
||||
|
Antioxidant activity (%) |
44.31 |
44.64 |
36.64 |
51.99 |
30.83 |
57.80 |
||||
|
Viscosity |
94.37 |
104.50 |
84.42 |
104.31 |
54.58 |
134.15 |
||||
|
Ash content (%) |
8.30 |
7.56 |
7.77 |
8.83 |
6.32 |
10.28 |
||||
|
Fiber content (%) |
24.03 |
27.55 |
2.34 |
50.40 |
10.02 |
58.08 |
||||
|
Chewiness(g) |
6.88 |
6.57 |
4.99 |
8.77 |
0.16 |
13.93 |
||||
This study demonstrated for the first time that the optimal mixture design can be used to optimize Awaze paste formulation by selecting the best quality parameters that include antioxidant activity, color(a*) value, viscosity, ash, fiber content and chewiness. D-optimal mixture design was used to optimize the formulation of Awaze paste by red pepper, garlic, red onion and ginger. The optimum formula obtained was 65.66% red pepper, 10% garlic, 19.086% red onion and 5.254% ginger with a desirability of 0.561. The formulated Awaze paste had higher antioxidant activity, ash content, fiber content, color value (a*), viscosity and chewiness compared to the control (household made Awaze paste ) sample. The finding of the study will provide a guide for commercial Awaze producers and household makers to produce quality product.
Acknowledgment The authors would like to thank Ethiopian Institute of Agricultural research (EIAR), Bahir Dar university- Institute of Technology for their administrative, financial, and resource support for the project.
Author Contribution Conceptualization, methodology, writing, original draft preparation: Biadge Kefale, Mulugeta Admasu, Solomon Workneh, Solomon Abate; Writing-review and editing, supervision: Biadge Kefale, Mulugeta Admasu , Solomon Workneh , Solomon Abate; All authors have read and agreed to the published version of the manuscript.
Data Availability Data will be available upon request
Funding The source of fund for the project work were Ethiopian Institute of Agricultural research (EIAR) and Bahir Dar university- Institute of Technology
Conflict of interest There is no any conflict of interest
Ethical approval Not applicable
Consent to participate Not applicable
Consent for publication All author consent for publication
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No competing interests reported.