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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2022 Apr 29;59(10):3965–3975. doi: 10.1007/s13197-022-05428-x

Effect of partial substitution of tomato for avocado on physico-chemical and sensory aspects of sweet-and-sour sauce

Willias Fabio Silva Pereira 1, Tatiana De Oliveira Lemos 1, Virgínia Kelly Gonçalves Abreu 1, Alana Graziela Duarte de Vasconcelos 1, Rodrigo Anacleto Pinto 1, Ana Lúcia Fernandes Pereira 1,✉
PMCID: PMC9525550  PMID: 36193386

Abstract

This study aimed to develop sweet-and-sour sauces with partial substitution of tomato for avocado. Four sauces formulations containing 0%, 25%, 50%, and 75% avocado pulp were prepared. The pH, titratable acidity (TA), sugar: acid ratio, color, consistency, and syneresis analyses were performed. Sensory acceptance was measured by the hedonic, Just-about-right (JAR), and purchase intent scales. Besides, a check-all-that-apply (CATA) form was applied to obtain description data on the formulations. The results of the color parameters showed that treatments containing avocado had higher (p < 0.05) lightness and yellowness. The avocado addition improved the rheological measurements. There was an increase in the consistency of the sauces when the avocado concentration increased. The opposite was observed for syneresis, which decreased (p < 0.05) as the avocado pulp concentration increased. Sensory evaluation revealed good consumer acceptance, and purchase intent analysis showed that most consumers would buy this product. For JAR data, sauces with 50 and 75% avocado had highest values of consistency in the JAR region. The consumers who reported the formulation with 25% avocado to be “not enough” penalized its acceptance, reducing the overall acceptance. Based on the frequency of terms cited by consumers in the CATA, it was possible to consider specific terms for each formulation. The terms pleasant color, good taste, brightness, and good consistency were associated with high overall acceptance. These terms were mostly used for sauces with 25% and 50% avocado. Therefore, sweet-and-sour sauces based on a combination of tomato and avocado has proven to be a viable alternative to traditional ketchup.

Keywords: Fruits, Blend sauces, Consistency, Syneresis, Penalty analysis, Check-all-that-apply

Research Highlights

  • Sauces containing avocado and tomato are an innovative, and viable alternative to traditional sweet-and-sour sauce ketchup.

  • The sauces with avocado performed higher consistency and slight syneresis.

  • Sauces with 25% and 50% avocado were associated to the pleasant color, good taste, and good consistency terms.

Introduction

Among tomato-derived foods, sauces are widely accepted by consumers, and contribute to economic growth, reducing losses and commercial depreciation of the harvest (Martínez-Huélamo et al. 2015). Ketchup, a sweet-and-sour sauce, and the most widespread tomato-derived sauce is defined as a pasty product obtained from ripe tomato fruits (Lycopersicum esculentum L.), that is a condiment with a tang contributed by vinegar, sugar, salt and spices (Divis et al. 2018).

According to Prakash et al. (2016), the tomato is the main ingredient commonly used ketchup preparation. However, values and apparent functional properties of the ketchup is limited to the nutrients present in tomato. Tomato is known to be rich in vitamins, minerals, lycopene, phenolics, flavonoids, dietary fibers, proteins and a large number of antioxidant compounds that help to be effectively in fighting against many cancer (Mezzomo and Ferreira 2016). A blend of tomato with a fruit richer in phytonutrients could help in enriching the nutritional profile and biological activity of these sauces.

A food source that fits this profile is avocado fruit (Persea americana Mill), which presents high nutritional quality and is well recognized for its health benefits, mainly due to the compounds present in the lipid fraction. Besides, it is also a source of vitamins A, B, and C and minerals such as potassium, phosphorus, magnesium, iron, and a rich source of fiber, proteins, and antioxidants (Santos et al. 2014; Pedreschi et al. 2019). Although many products can be produced from this fruit, such as guacamole, and pasta, it is usually consumed in natura. However, considering its benefits, a more extensive application in the food industry would be expected (González-Fernández et al. 2015; Bhuyan et al. 2019).

The relevance of blend sauces with tomato becomes more evident when considering the bioavailability of carotenoids of this fruit. The processing of this fruit can increase the bioavailability of carotenoids by cell wall rupture and denaturation of proteins complexed with carotenoids (Kamiloglu et al. 2013). Besides, many health and food science and technology studies have approached to improve the conversion of carotenoids from provitamin A to vitamin A (Unlu et al. 2005; Wang et al. 2008; Goltz et al. 2012). Provitamin A carotenoids contain can be enzymatically cleaved to produce vitamin A, an essential micronutrient for human beings (Raghuvanshi et al. 2015).

Kopec et al. (2014) considered that the incorporation of lipids in the diet is a significant factor for carotenoids bioavailability. These authors carried out studies with humans and observed that avocado intake as a lipid source could increase the efficiency of conversion of carotenoids from provitamin A to vitamin A 4.6 times more than the consumption of carotenoids of provitamin A alone.

Therefore, the blend of sweet-and-sour sauce containing tomato and avocado can be an alternative to healthier food. However, it is essential to know the impact that this insertion may provide for the physicochemical characteristics and sensory acceptance by the consumer. Nasir et al. (2014), producing a mixed tomato and date ketchup, reported a reduction of texture and overall acceptance with the increase date pulp addition. Kumar and Ray (2016), in turn, reported on the possibility of ketchup preparation using mushroom pulp with tomato pulp. These authors observed that the formulation prepared with 50% tomato pulp and 50% mushroom pulp was the highest acceptable sensorial.

Moreover, no studies have been carried out to produce a sweet-and-sour sauce with partial substitution of tomato for avocado. Therefore, this study aimed to develop sweet-and-sour ketchup sauces, partially replacing tomatoes with avocados, and characterize them through physicochemical analyses, to evaluate the sensorial acceptance. This study has a patent deposited at the National Institute of Industrial Property in Brazil with a register number of BR10202001145.

Materials and methods

Sweet-and-sour sauces production

In this study, were used commercial tomato pulp (Lycopersicum esculentum Mill) and avocado pulp from freshly harvested ripe fruits of Margarida variety (Persea americana Mill). The sauces were processed following the methodology by Araújo et al. (2013), with modifications.

Four formulations of sweet-and-sour ketchup sauce consisting of tomato and/or avocado as the main ingredient (mixed base—60%) and water (40%) were produced. The tomato/avocado ratio in the mixed base differed from one formulation to another, as follows: T1—100% tomato (control), T2—75% tomato and 25% avocado, T3—50% tomato and 50% avocado, and T4—25% tomato and 75% avocado.

The concentrations of the other ingredients were expressed about the mass of the main ingredients. Therefore, the formulations also contain white vinegar (30%), onion powder (2.6%), garlic powder (0.5%), and the hydrocolloids guar and xanthan gums (0.1%). Brown sugar was added to each formulation. Each formulation was prepared in triplicate and homogenized in an industrial blender for 10 min. Then, the sauces were subjected to pasteurization (90 ºC/60 s) in an induction stove until the mixture to reach concentration of the soluble solids (SS) of 28°Brix. Afterward, each one was cooled in an ice bath until it reached 30.0 ºC and then stored in properly cleaned polypropylene tubes (240 mL). All treatments were submitted to physicochemical analyses (pH, titratable acidity—TA, sugar: acid ratio, color, consistency, and syneresis) and sensory evaluation.

Physicochemical properties

The pH of the sauces was measured by direct-reading using a potentiometer (Biotech, mPa-210, Piracicaba, Brazil) equipped with a combination electrode. TA was determined according to the AOAC official method nº 942.15 by titration with NaOH solution (0.1 M). The results were expressed as g of acetic acid per 100 g of sauce sample (AOAC 2000). The direct-reading measurements of the SS were carried out using a digital refractometer (Hanna Instruments, HI96801, Woonsocket, United States). From the SS and TA values, the SS/TA (sugar: acid) ratio of each sauce was determined.

The color was performed using a spectrophotometer (Minolta, CM2300D, Tokyo, Japan), operating on the CIELAB system. The reflectance instruments determined three color parameters: lightness (L*) redness (a*), and yellowness (b*). The total color difference (ΔE) between the treatments containing avocado and the control (T1) was calculated using Eq. 1.

ΔE=(ΔL2)+(Δa2)+(Δb2) 1

A Bostwick Consistometer measured the consistency of sauces. The method applied consists of measuring the distance a sample flows in a given time interval (30 s). Results were expressed in centimeters per second (cm/30 s) (Juszczak et al. 2013).

The physical stability (syneresis) of the sauces was evaluated using an accelerated aging test. Aliquots (8.0 g) of the sauces were transferred to the 15 mL test tubes and centrifuged at 2400 g for 15 min (Bortnowska et al. 2016). The syneresis percentage was determined, as shown in Eq. 2:

%syneresis=massofthesupernatantmassofthesample×100 2

Sensory evaluation

Sensory evaluation was performed by 100 untrained judges of both sexes (51% were women and 49% men). The majority were young people, mostly between 18 and 25 years old (81%), followed by the age ranges between 26 and 35 years old (14%), and 36 and 50 years old (5%). The judges were selected by like and consumed sauces. The samples (20 g) were given in a monadic sequential order in standard sensory booths, under artificial daylight type illumination, temperature control (22–24 °C) and air circulation. The sauce samples were served with bread as a vehicle for the product.

Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance. The scale ranged from 1 (dislike extremely) to 9 (like extremely) and with a neutral centre point (5) of ‘‘Neither Like nor Dislike”. A just-about-right (JAR) scale, ranging from 1(Much too weak than JAR) to 9 (Much too strong than JAR), with a neutral centre point (5) of ‘‘Just-about-right” was used to assess consistency, sour, and sweetness. The purchase intent was evaluated using a 5-point scale ranging from 1 (I certainly would not buy) to (I would certainly buy) (Stone et al. 2004; Narayanan et al. 2014).

Consumers also had to answer a Check-all-that-apply question (CATA) with 23 terms related to sensory characteristics of sauces. Consumers were asked to check all the terms that they considered appropriate to describe each sauce (Lado et al. 2010). The terms were selected based on previous researches (Baldwin et al. 2015; Prakash et al. 2016) and included terms with different intensities. The following terms were available: green color, red color, pleasant color, good consistency, low consistency, high consistency, visible liquid phase, brightness, creamy aspect, garlic flavor, vinegar aroma, intense aroma, onion flavor, astringent taste, salty taste, sweet taste, acid taste, bitter taste, strange, good taste, small visible residues, and plastic taste.

Data analysis

Data analysis was performed using the XLSTAT program (Addinsoft Paris, France), with a significance level of 0.05. The physicochemical data were subjected to ANOVA, and the means were compared using the Tukey test. In the sensory data evaluated with the hedonic scale, the treatments were considered as a fixed source of variation and the consumer as a random effect. The attributes were analyzed by Friedman's non-parametric test, with a significance level of 0.05.

The sensory acceptance data evaluated with the JAR scale were grouped as follows: percentages from 1 to 4 was named “not enough region.” The percentage at score 5 was called ‘‘JAR region’’ and the percentages from 6 to 9 of ‘‘too much region’’. For these data, penalty analysis was also used to identify decreases in the overall liking when the attributes were rated as "not enough" or " too much.’’ The parameters with a penalty score above 0.5 with occurrence higher than 20% were considered attributes that decreased the overall liking. For the purchase intention, the percentages of the categories were also divided into three regions: percentages of 1 and 2 were named ‘‘I would buy it’’, percentage at score 3 was called ‘‘Maybe I would but it’’ and the percentages of 4 and 5 of ‘‘I would not buy it’’.

In the CATA data analysis, the frequency of each term was determined by counting the number of consumers who used it to describe each sauce sample, and the treatments were compared to each other through the Cochran Q test. The Chi-square method was used to perform a correspondence analysis to obtain a relationship between samples and terms from the CATA. The principal coordinates analysis was performed on the sensory terms used to describe the samples considering the overall Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance.

Results and discussion

Physicochemical properties

pH did not change (p > 0.05) between treatments (values between 3.49 and 3.76) (Table 1). Torbica et al. (2016), producing a ketchup using tomato pomace and with a high content of natural fiber, also obtained pH values lower than 4.0. These authors concluded which this value is generally considered as a threshold for product stability (Rajchl et al. 2010). Otherwise, there might be a proliferation of unwanted microorganisms, in particular, those that increase the degradation of these products. Thus, the avocado addition in the formulations did not affect microbiological safety from the pH range point of view.

Table 1.

Physicochemical properties of sweet-and-sour sauces with partial substitution of tomato for avocado

Avocado concentration (%)
0% 25% 50% 75%
pH 3.49 ± 0.10 A 3.61 ± 0.08 A 3.76 ± 0.14 A 3.76 ± 0.12 A
TA1 1.24 ± 0.01 A 1.21 ± 0.02 A 1.05 ± 0.01 B 1.02 ± 0.02 B
Sugar: acid ratio 16.72 ± 0.13 C 16.81 ± 0.31 C 18.83 ± 0.48 B 20.67 ± 0.21 A
L*2 7.75 ± 1.69 C 23.59 ± 2.88 B 25.28 ± 3.25 AB 30.01 ± 0.78 A
a*3 24.08 ± 0.82 A 19.67 ± 3.92 A 18.25 ± 3.57 A 17.84 ± 0.82 A
b*4 13.21 ± 2.90 C 37.29 ± 2.44 B 36.84 ± 5.75 B 51.11 ± 1.10 A
ΔE5 0.00 ± 0.00 C 29.38 ± 2.98 B 30.57 ± 1.63 B 44.38 ± 1.44 A
Consistency (cm/30 s) 24.00 ± 0.01 A 18.30 ± 0.02 B 15.30 ± 0.01 C 13.50 ± 0.01 D
Syneresis (%) 58.18 ± 0.61 A 33.93 ± 4.70 B 0.54 ± 0.36 C 0.37 ± 0.43 C
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a−b Means followed by different letters in the lines indicate a significant difference between treatments by the Tukey Test (p < 0.05). 1TA = titratable acidity (expressed as g of acetic acid/ 100 g—%); 2L* = lightness; 3a* = redness; 4b* = yellowness; 5ΔE = total color difference

For the titratable acidity, the formulations with 50% and 75% avocado presented the lowest values (p < 0.05) (Table 1). These lower values are due avocado to be classified as a non-acid fruit and compared to other fruit, and it contains deficient amounts of citric and malic acid (Pedreschi et al. 2019). Santos et al. (2016) analyzed the TA of different commercial bottles of ketchup and found values between 1.32 to 1.75% that are similar to those obtained in the present study. This similarity indicates that the partial substitution of tomato for avocado did not cause changes that could make the characterization of acidity unfeasible for this type of product.

The sugar acid ratio was high (p < 0.05) in the treatment with 75% avocado, followed by the 50%, 25%, and, finally, the control treatment (0%) (Table 1). Thus, the results denote a direct proportion between the avocado concentration in the sauces and the sugar acid ratio. This result is related to the lower acidity values in sauces with the highest avocado concentration. Besides, the combination of sugar and acid in these formulations can provide a mild taste, from a sensory perspective since this combination can impact sweetness and influence the taste of the final product (Baldwin et al. 2015). The balance between sugars and acids is a quality indicator for tomato-based products. The sweetness is among the desired features in tomato-based products, which may interfere with whether the product will have a pleasant, or undesirable taste from the sensory perspective (Torbica et al. 2016).

Regarding color parameters, the treatments containing avocado presented greater lightness (L*) than the control formulation (p < 0.05). The color component a* (redness) did not vary (p > 0.05) from one treatment to another, which indicates a balance between the green color of avocado and the red color of the tomato. For the color component b*, the highest values (p < 0.05) were found in the treatment with 75% avocado, followed by the treatments with 25%, 50%, and the control treatment (Table 1). Therefore, the addition of avocado led to a brighter product with and greater yellowness.

Prakash et al. (2016) also reported an increase in lightness with high acerola concentration in blend ketchup from acerola and tomato. According to the authors, the lycopene of tomato provides lower lightness. Therefore, the higher lightness in the formulation containing avocado is resultant of the reduction of tomato, with consequent lycopene reduction. The yellowness increase in treatments with avocado addition is resultant of the incorporation of carotenoid pigments present in this fruit (Wang et al. 2010).

For the total color difference (ΔE), the treatment with 75% avocado presented the highest value (p < 0.05), followed by treatments with 25% and 50% (Table 1). For Torbica et al. (2016), a value of ∆E greater than 3 allows naked eye observation of the color variation. Thus, it can be concluded that avocado concentrations equal to or greater than 25% provided changes in the sauce color that consumers can easily notice. In the present study, the ∆E variation was due to the yellowness increase and lightness decrease provided by the addition of avocado pulp.

The Bostwick consistometer is used to determine the consistency of ketchup, which is used in the measurement of flow length (cm) of tomato ketchup within a given time (Juszczak et al. 2013). A decrease in the flow (p < 0.05), and therefore, an increase in the consistency of the sauces was noticed as the avocado concentration increased (Table 1). Consistency is considered one of the most critical parameters in the analysis of tomato-derived products, and consequently, influences the acceptance of the product (Hui and Evranuz 2015). Komeilyfard et al. (2016) reported that the hydrocolloids addition is used to improve the consistency of tomato ketchup observed by decreased of Bostwick consistency values. Thus, this increase in the consistency observed in the sauces containing avocado was positively perceived by the consumer, illustrated by the higher percentage of consumers that classified the consistency as “just-about-right”, as shown in Fig. 1A.

Fig. 1.

Fig. 1

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The ‘‘not enough,’’ ‘‘just-about-right,’’ and ‘‘too much’’ regions for the consistency (A), sour (B), sweetness (C), and purchase intent (D) of the sweet-and-sour sauces with partial substitution of tomato for avocado

The opposite was observed for syneresis, which decreased (p < 0.05) as the avocado pulp concentration increased. The syneresis values for the formulations with 50% and 75% avocado pulp did not differ from each other (Table 1). Therefore, it was possible to verify an inverse correlation between syneresis and consistency. Higher flow values indicate that the product is more fluid and therefore has a higher liquid phase. According to Mizrahi (2010), this liquid phase is called syneresis, when it is separated from the products derived from tomatoes, being an undesirable aspect.

The treatments with 50 and 75% avocado pulp showed low water release, behavior that may be related to the starch present in the avocado pulp, which probably acted as a water binding agent and promoted a greater consistency to the final product. This result may represent a new alternative to the use of hydrocolloids, such as tragacanth gum, guar gum, xanthan gum, and carboxymethylcellulose, which are used in sauce formulations to reduce the syneresis phenomenon in the final product (Amiri et al. 2015).

Sensory evaluation

The consumer profile showed that about 91% “like very much” or “like moderately” of ketchup, and 80% said that they “like very much” or “like moderately” of avocado. Therefore, they constitute a public with a high potential for consumption of tomato-derived foods, suggesting that products combining tomatoes and avocados may be well-accepted.

For the hedonic scale, the averages for the sensory attributes and overall acceptance were between 6.12 and 7.75 (Table 2), that is, between the terms “like slightly” and “like very much” on the hedonic scale. Thus, it can be concluded that the sauces had good consumer acceptance. Besides, this result indicates that a product similar to traditional ketchup is well accepted by consumers and thus strengthens the trend towards the development of new products with higher added value, including additional health benefits.

Table 2.

Sensory acceptance for color, appearance, aroma, flavor attributes, and overall acceptance measured by hedonic scale of sweet-and-sour sauces with partial substitution of tomato for avocado

Avocado concentration (%)
0% 25% 50% 75%
Color 7.75 ± 1.09 A 7.14 ± 1.50 B 7.12 ± 1.40 B 6.35 ± 1.77 C
Appearance 7.46 ± 1.22 A 7.00 ± 1.41 B 7.02 ± 1.33 B 6.50 ± 1.71 B
Aroma 6.96 ± 1.47 A 6.57 ± 1.87 AB 6.41 ± 1.84 AB 6.28 ± 1.99 B
Flavor 6.72 ± 2.05 A 6.47 ± 2.19 A 6.31 ± 2.07 A 6.12 ± 2.21 A
Overall liking 6.90 ± 1.61 A 6.72 ± 1.71 A 6.60 ± 1.68 A 6.40 ± 1.73 A
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a−b Means followed by different letters on the lines indicate a significant difference between treatments by the Friedman Test (p < 0.05)

Regarding color and appearance, treatments with 25%, 50%, and 75% avocado pulp in the formulation had lower (p < 0.05) acceptance than the control treatment (Table 2). Some color changes were noticed by the consumers, who expected an intense red color since it is a tomato-based product, just like as in the control formulation.

The wider acceptance of the control treatment may also be related to the yellow color intensity since this formulation presented the lowest b* value (Table 1). This result reveals that the gradual substitution of tomato pulp by avocado pulp produced a color different from the color presented by the control treatment, which negatively affected the acceptance. However, the tasters said they "like moderately" the color and appearance of the treatments containing avocado, except for the formulation with 75% avocado pulp, which they only " like slightly." Prakash et al. (2016), in ketchup from acerola and tomato, reported that the panelists observed that sauces with high acerola concentrations were lighter in color. According to these authors, it is obviously due to the relative lack of lycopene content and the loss of anthocyanins during ketchup preparation. Therefore, in the present study, the reduction of red color affected the acceptance of the sauces negatively.

The aroma of the formulation with 75% avocado scored lower (p < 0.05) than the control treatment (Table 2). For the aroma, Prakash et al. (2016) also reported that the spices could have a synergistic influence of complex aroma of acerola pulp changing the aroma. Therefore, in the present study, the aroma avocado influenced the acceptance when high concentration was used.

Regarding flavor and overall liking, no difference was observed (p > 0.05). This shows that, in general, the sweet-and-sour sauces present sensory properties pleasant to consumers (Table 2). Kumar and Ray (2016) reported that it is possible to produce a mixed ketchup using mushroom pulp with tomato pulp with good acceptance. However, these authors observed the reduction acceptance of flavor and overall Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance with 75% of mushroom pulp. Thus, it can conclude that the results obtained herein were positives because the acceptance of flavor and overall Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance was maintained the same, even with the 75% avocado concentration.

For JAR data, the consistency evaluation (Fig. 1A) indicated that the sauces with the highest avocado concentrations (50 and 75%) showed the highest values in the JAR group, 58 and 62%, respectively. The control treatment and the formulation with 25% avocado showed the highest values in the not enough region, 70 and 58%, respectively.

This result agreed with the behavior verified by Bostwick readings during the physicochemical analysis (Table 1). Besides, the formulations with higher avocado concentrations performed better on the consistency evaluation through a JAR scale (Fig. 1A). This means that the consistency acceptance by consumers was enhanced as the avocado concentration increased, which is a positive result since consistency is an essential factor in determining the acceptability of tomato products (Kumbar et al. 2019).

The penalty analysis was applied to identify the effect of the attribute consistency, acidity, and sweetness on the overall Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance of the sweet-and-sour sauces with partial substitution of tomato for avocado (Table 3). This information is important, as it shows how many points have been lost on the overall acceptance due to deviations from JAR.

Table 3.

Penalty analysis of the just-about-right (JAR) compared to the overall acceptance measured by the hedonic scale (percentage of consumers and mean decreases) of sweet-and-sour sauces with partial substitution of tomato for avocado

Avocado concentration (%) Consistency Sour Sweetness
Not enough Too much Not enough Too much Not enough Too much
0 –1 –1 –1 40%2 (0.854)3 21%2 (1.044)3 –1
25 58%2 (0.767)3 –1 –1 42%2 (1.078)3 23%2 (1.179)3 –1
50 –1 –1 –1 –1 –1 –1
75 –1 –1 –1 –1 –1 –1
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1– Indicates that less than 20% of consumers chose the JAR category

2Percentage of consumers who considered consistency, sour, and sweetness to be not enough or too much for JAR

3The number in parentheses is the difference in the mean compared with the consumer response score for overall acceptance

Based on the consistency data, it was observed that the consumers who reported the formulation with 25% avocado to be “not enough” (Table 1) penalized its acceptance, reducing the overall Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance score. Therefore, low consistency negatively affected the acceptance of the product. Nasir et al. (2014) observed a reduction of texture acceptance of mixed tomato and date ketchup. However, different from the present study, the reduction occurred when the date pulp increased. Therefore, it can conclude that avocado has a positive effect in consistency.

For sour, the highest percentages of all treatments were in the JAR region. The control had the highest value (56%), followed by treatments with 25%, 50%, and 75% of avocado, with 49%, 48%, and 47%, respectively (Fig. 1B). However, the consumers who rated the sour of the control treatment and the formulation with 25% avocado as too much than JAR penalized its acceptance. Singh et al. (2014) reported that the acceptability of tomato ketchup is dependent on flavor, consistency, and desired sourness. These authors also observed that overall acceptability score showed a declining trend.

In tomato ketchup with increase in acid level. Therefore, the highest TA values (Table 1) negatively affected the product acceptance, which indicates that the addition of avocado can improve this sensory attribute.

Regarding sweetness, the majority of the panelists considered the formulations as JAR, especially the control treatment (64%), followed by treatments with 25% (56%), 50% (53%), and 75% (52%) avocado (Fig. 1C). These results point to a strong tendency to accept this sensory attribute since the results revealed that more than 50% of the panelists affirmed that the variants of the sweet-and-sour sauces presented an ideal sweetness. The consumers who considered the sweetness of the control treatment and the formulation with 25% avocado, not enough penalized their acceptance, reducing the overall liking score. These results indicate that the lower sugar: acid ratio obtained from the physicochemical properties of these formulations (Table 1) reduced consumer acceptance.

Regarding purchase intent, all formulations showed highest percentages in the “would buy” group, especially the control treatment and the formulation with 25% avocado (52%), followed by the formulation with 75% avocado (50%), and finally, the treatment with 50% avocado (45%) (Fig. 1D). These results show that the four formulations present a good sales prospect, especially the treatment with 25% avocado, as it reached the same percentage in the “I would buy it” region as the control treatment.

For CATA data, according to the Cochran’s Q test, there was a significant difference in frequencies of 9 out of the 22 descriptors, which suggests that consumers perceived differences in the sensory attributes of the sweet-and-sour sauces containing avocado. Such descriptors can be considered the most adequate in the description of the samples by the consumers (Table 4).

Table 4.

Frequency (%) of each term used by the consumers in check-all-that-apply method for sweet-and-sour sauces with partial substitution of tomato for avocado

Atributtes p-value 0% 25% 50% 75%
Avocado concentration (%)
Red color 0.000 74 a 41 b 28 b 11 c
Green color 0.000 0 b 2 b 7 b 21 a
Pleasant color 0.037 49 ab 58 a 52 ab 40 b
Good consistency 0.000 27 b 39 ab 53 a 54 a
Low consistency 0.000 58 a 47 a 29 b 26 b
High consistency 0.013 2 a 1 a 4 a 9 a
Visible liquid phase 0.000 27 a 18 ab 5 c 11 c
Brightness 0.142 39 a 39 a 31 a 32 a
Creamy aspect 0.000 6 c 3 c 20 b 38 a
Garlic flavor 0.427 16 a 14 a 10 a 14 a
Vinegar aroma 0.867 35 a 33 a 35 a 31 a
Strong aroma 0.348 26 a 34 a 32 a 27 a
Onion flavor 0.428 23 a 20 a 17 a 17 a
Astringent flavor 0.697 13 a 11 a 15 a 12 a
Salty flavor 0.202 17 a 15 a 11 a 10 a
Sweet flavor 0.898 27 a 26 a 29 a 29 a
Acid flavor 0.847 42 a 40 a 37 a 40 a
Bitter flavor 0.283 8 a 12 a 13 a 15 a
Strange flavor 0.000 15 b 22 ab 30 a 36 a
Good taste 0.015 48 a 43 ab 38 ab 30 b
Small visible residues 0.392 2 a 2 a 2 a 1 a
Plastic flavor 0.392 0 a 0 a 1 a 1 a
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a−bMeans followed by different letters in the lines indicate a significant difference between the formulations by the Cochran Test (p < 0.05)

The "red color" term was mostly used to describe the control treatment (no avocado pulp), followed by those containing 25% and 50%, and finally, the treatment with 75% avocado. Contrarily, the "green color" term was mostly used to describe the treatment with 75% avocado, followed by those with 50% and 25%. Reports on color change were already expected in the formulations containing avocado since the red from the tomatoes, and the green from avocados combined provided a product with a more yellowish color. However, despite the change in color, the frequency of the "pleasant color" term for the control treatment did not differ from what was reported for treatments containing avocado. Thus, this factor did not affect product evaluation negatively.

The formulations with 75% and 50% avocado pulp were reported to present “good consistency” more frequently than the control treatment (p < 0.05). Differently, the formulations with 0% (control) and 25% avocado were more frequently reported to present “low consistency” (p < 0.05). The term "visible liquid phase" was mostly used to describe for the control treatment and the formulation with 25% avocado (Table 4). The separation of solid and liquid content is one of the most important problems in conventionally processed tomato products, and it affects both product quality and hence consumer acceptability negatively. To reduce this problem, hydrocolloids are added to tomato ketchup (Komeilyfard et al. 2016). Thus, the less presence of visible liquid phase in formulations with high avocado concentration shows an advantage of using this raw material in the sauce’s formulations.

The term “creamy aspect” was mostly used (p < 0.05) to describe the treatments with 75% and 50% avocado, respectively (Table 4). These results are in agreement with the Bostwick consistency (Table 1) and with the evaluation of the consistency of the sauces using a JAR scale (Fig. 1A), where it was confirmed that the treatments containing avocado revealed low water release and, consequently, presented a creamier aspect.

The formulations with 75% and 50% avocado were the ones most described as having a "strange taste" (p < 0.05) (Table 2). It is important to emphasize that the term "strange taste" refers to the fact that these samples with these characteristics are not familiar to the consumer. The term does not have a negative connotation. This result was expected for samples with higher concentrations of avocado, as consumers are used to consuming sauces only with tomatoes.

It was also found that the term "good taste" was used mostly for the control treatment (p < 0.05) (Table 4). However, despite the difference between these terms, the flavor attribute measured using the hedonic scale showed no difference from one treatment to another (Table 2). There was no significant difference (p > 0.05) between the formulations regarding the following descriptors: vinegar aroma, strong aroma, brightness, acid taste, bitter taste, sweet taste, salty taste, high consistency, astringent flavor, garlic flavor, onion flavor, plastic flavor and small visual residues (Table 4).

Figure 2 presents the results of the correspondence analysis carried out on the data on the sweet-and-sour sauces containing avocado, in which dimensions 1 and 2 explained 97.78% of the variance. It was observed that the formulations were similarly described in general terms. The control treatment (0% avocado) was described by the terms "red color," "low consistency," and "visible liquid phase." The treatment with 25% avocado was defined by the terms "pleasant color," and "good taste." The formulation with 50% avocado was characterized by the terms "good consistency" and "strange taste." Finally, the terms used to describe the treatment with 75% of avocado were "high consistency," "green color," and "creamy aspect."

Fig. 2.

Fig. 2

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Representation of sweet-and-sour sauces with partial substitution of tomato for avocado and the terms used in the first and second dimensions of the Correspondence Analysis on the CATA form data

Figure 3 shows the results of the principal coordinates analysis of the descriptors and the overall Consumer acceptance was measured for a hedonic scale using the attributes color, appearance, aroma, flavor, and overall acceptance. It was observed that a wider acceptance is associated with the terms "pleasant color," "good taste," "brightness," and "good consistency." These terms were mostly used for sauces with 25% and 50% avocado. It is also noteworthy that the presence of avocado pulp in the formulations provided a new sensory feature since it is an innovative combination. However, all sweet-and-sour sauces were well-accepted by consumers.

Fig. 3.

Fig. 3

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Sensory terms used to describe the sweet-and-sour sauces with partial substitution of tomato for avocado in the first two dimensions of the CATA count, considering the overall acceptance

It is noteworthy that the development of new food products from raw materials aiming to obtain better nutritional properties and sensory attributes represents a current market trend. Besides, the sauces are among the foods that will be most consumed away from home in the coming years (Mansouripour et al. 2017).

Conclusion

The results obtained in this study lead to the conclusion that it is possible to develop sweet-and-sour sauces with partial substitution of tomato for avocado. Regarding the characterization of the sauces, the avocado addition reduced the acidity of the sauces. The avocado provided sauces with more lightness and yellowness. The sauces with avocado performed higher consistency and slight syneresis, showing that this partial substitution can contribute to minimizing problems related to these parameters.

Sensory evaluation revealed good consumer acceptance, and purchase intent analysis showed that most consumers would buy this product. For JAR data, sauces with 50 and 75% avocado had highest values of consistency in the JAR region. For sour and sweetness, the highest percentages of all treatments were in the JAR region. For CATA data, nine terms (red color, green color, pleasant color, good consistency, low consistency, visible liquid phase, creamy aspect, strange flavor, and good taste) of the twenty-two available were considered the most appropriate to describe the formulations. The correspondence analysis revealed that widest acceptance was associated with the terms “pleasant color,” “good taste,” “brightness,” and “good consistency.”

Author contributions

WFSP, AGDV and RAP collected test data and wrote the initial draft of the manuscript. TOL, and VKGA designed the study and made all necessary corrections and carried out the final editing of the manuscript. ALFP designed the study and gave the final approval for publication.

Funding

This research was supported by the Agency for Innovation, Entrepreneurship, Research, Postgraduate, and Internationalization (AGEUFMA), Federal University of Maranhão, Brazil. This research also was supported by the National Institute of Tropical Fruits (INCT-FT (303791/2016–0)), National Council for Scientific and Technological Development (CNPq (486745/2013–9)), Technological Development of Maranhão (FAPEMA (885/15)) and Coordination of Improvement of Higher Education Personnel – Brazil (CAPES, Financial Code 001) with the financial support and scholarships.

Data availability

The datasets generated and/or analysed during the current study is not publicly available due to privacy concerns but are available from the corresponding author upon reasonable request.

Code availability

Not applicable.

Declarations

Ethics approval

Not applicable.

Consent to participate

Not applicable.

Consent for publication

Not applicable.

Conflict of interest

The authors that they do not have any conflicts of interest to declare.

Footnotes

Publisher's note

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Contributor Information

Willias Fabio Silva Pereira, Email: williasfabio@hotmail.com.

Tatiana De Oliveira Lemos, Email: tatiana.lemos@ufma.br.

Virgínia Kelly Gonçalves Abreu, Email: vkellyabreu@gmail.com.

Alana Graziela Duarte de Vasconcelos, Email: alanagraz@hotmail.com.

Rodrigo Anacleto Pinto, Email: rodrigoanacleto1997@gmail.com.

Ana Lúcia Fernandes Pereira, Email: anafernandesp@gmail.com.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The datasets generated and/or analysed during the current study is not publicly available due to privacy concerns but are available from the corresponding author upon reasonable request.

Not applicable.

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