The effect of butterfly pea (Clitoria ternatea L.) and roselle (Hibiscus sabdariffa L.) powder addition on the physicochemical and sensory properties of white chocolate ganache

Ganache is a mixture of chocolate and cream commonly utilized as fillings or glazing. Butterfly pea and roselle are edible flowers with potential bioactive compounds that could improve ganache functionality. This research aimed to understand the effect of butterfly pea and roselle powder addition with various concentrations (1%, 1.5%, and 2% (w/v)) on white chocolate ganache’s physical and sensory properties. The samples were analyzed for their water content, color profile, water activity, total soluble solids, and hedonic scores. Results showed that the butterfly pea-added ganache had a higher water content and activity than the roselle-added ganache. However, the total soluble solid analysis showed a reverse trend. Addition of 2% edible flower powder decreased the moisture content of ganache up to 2%. Increasing the concentration of butterfly pea powder resulted in higher blueness intensity, while in roselle ganache, there was no significant effect on the redness. The hedonic test showed that the difference in edible flower types and concentration resulted in no significant difference in panelists’ acceptance of all tested sensory attributes.


Introduction
Ganache is a processed chocolate product popular in the confectionery and bakery industry.Although until now, there have been no regulations regarding the definition, ingredients, and ganache standards, these products are generally made from a mixture of chocolate and cream.Therefore, ganache is also said to be an emulsion due to the mixture of chocolate and cream.The cream part is considered the water phase because the cream is an oil-in-water emulsion, and chocolate is the oil phase [1].Ganache generally has a thick and soft texture, a glossy appearance, and a slightly bitter-sweet taste typical of chocolate [2].Ganache is commonly used as a filling for truffles, chocolate pralines, cakes, and glazes [3].
Increasing the functionality of white chocolate can be done by incorporating bioactive compounds from edible flowers.The use of flowering plants has been done since centuries ago.Initially, the use of flowers was intended for decoration or fragrance purposes.However, there is an increasing trend of edible flowers, which are safe to consume [4].Edible flowers can be consumed fresh, in brewed drinks, or processed.Edible flowers have attractive colors, tastes, and aromas and contain metabolites or bioactive compounds that can benefit the body.Edible flowers are rich in antioxidant compounds such as flavonoids, anthocyanins, phenolic acids, and carotenoids.Due to these bioactive compounds, certain edible flowers can provide functional effects as antioxidant, immunomodulatory, anticancer, 1324 (2024) 012107 IOP Publishing doi:10.1088/1755-1315/1324/1/012107 2 antibacterial, anti-inflammatory, cardioprotective, and so on [5].The functional properties of the edible flowers may provide protection and improve the immune system.
Among various edible flower species present in the world, butterfly pea (Clitoria ternatea L.) and roselle (Hibiscus sabdariffa L.) are widely available in Southeast Asia.The butterfly pea flower has distinct bright blue petals due to the presence of an anthocyanin pigment called ternatin with a malonylated 3,3',5'-triglucoside structure.In addition to their bright color, anthocyanins, and other bioactive compounds can provide antioxidant, anti-inflammatory, anticancer, and other benefits [6].Roselle has bright red petals and contains high levels of bioactive compounds.Roselle contains flavonoid compounds such as anthocyanins (cyanidin-3-glucoside) which contributes to the red color of the flower and can also act as antioxidants to inhibit free radicals [7,9].Roselle also contains a high concentration of vitamins to boost the human immune system such as ascorbic acid (vitamin C) [8,9].The natural red color of roselle and the blue color of butterfly pea flowers were widely used as natural food colorants.
Previous studies have studied the incorporation of mulberry leaf, black seed oil, aronia, and Porphyra tenera seaweed into chocolate ganache [10][11][12][13].However, there has been no study on the effect of adding edible flowers, namely butterfly pea and roselle on white chocolate ganache.Therefore, this study aimed to determine the effect of the application of butterfly pea and roselle with concentrations of 1%, 1.5%, and 2% (w/v) on white chocolate ganache in terms of physical and sensory properties.

Sample preparation
Food grade edible flowers powder of roselle (H.sabdariffa) and butterfly pea (C.ternatea) were purchased from local commerce.White chocolate ganache base formulation was developed following [3] with modifications and presented in Table 1.Sample preparation of white chocolate ganache began with heating the mixture of whipped cream and inverted sugar until 45 ℃.After reaching 45 ℃, chopped white chocolate couverture was poured into the cream and sugar mixture.Next, unsalted butter was added to the chocolate and cream mixture, and then 0.1% carrageenan was added to the white chocolate emulsion and mixed until homogenous.Afterward, the white chocolate ganache base was added with roselle and butterfly pea powder with concentrations of 1%, 1.5%, and 2% (w/v).Finally, the samples were poured into plastic containers and chilled until physical and sensory analysis.

Analysis
2.2.1.Moisture content.Moisture content of white chocolate ganache was analyzed using gravimetric method [14].The empty aluminium cup was dried in an oven (Memmert UF 260, Germany) at 105 ℃ for 30 minutes before being cooled in a desiccator and weighed.Approximately 5 grams of white chocolate ganache was weighed in a dried aluminium cup and then dried in an oven for 5 hours at 105 ℃.The cup containing the sample was then cooled in a desiccator for 30 minutes and weighed.Drying was repeated until constant weight.Moisture content was calculated using the following formula: where W1 is the weight of a dried empty aluminium cup (g), W2 is the weight of the sample and cup before drying (g), and W3 is the weight of the sample and cup after drying (g).

Water activity.
Water activity was conducted at 25 ℃ using a water activity meter (Aqualab, USA) [3].Approximately 5 grams of white chocolate ganache was poured into a container and measured using an aw meter.

Total soluble solids.
Total soluble solids were analyzed using a refractometer and presented as o Brix [3].To 10 mL of warm water, 5 grams of white chocolate ganache was mixed and then measured using a refractometer.

Statistical analysis.
All analyses were conducted in triplicate and expressed as mean±standard deviation.Data collected was analysed using ANOVA by Minitab at a significance level of 5% to find significant differences (p < 0,05) between the sample means.

Moisture content
The moisture content result of white chocolate ganache showed that adding 1% butterfly pea had no significant difference to the moisture content of 1.5% butterfly pea.Adding 2% butterfly pea decreased ganache moisture content by approximately 2%.As seen in Figure 1, adding roselle powder at all concentrations significantly decreased moisture content.Butterfly pea-added chocolate ganache had a higher moisture content than roselle-added chocolate ganache.Butterfly pea flower has a higher moisture content (92.08%) compared to roselle (89.4% [17,18].The addition of roselle powder could add total solids, which could bind free water, causing lower moisture content compared to ganache without edible flower addition.Increasing the concentration of edible flowers could significantly lower the moisture content of white chocolate ganache.This study result is in accordance with [19], who found that increasing powder concentration decreased moisture content.

Color profile
Color becomes an essential sensory attribute that could influence consumers' acceptance of the product [20].The result in Table 2 showed that the addition of roselle and butterfly pea powders to white chocolate ganache gave a significant difference in the lightness, redness, and blueness of white chocolate ganache.White chocolate ganache with roselle had higher L*, a*, and b* values than butterfly peaadded ganache.White chocolate ganache with roselle powders had lighter colors with red (+a*) and yellow (+b*) color tendency.In low pH, roselle had anthocyanin pigment in the form of cyanidin-3glucoside, which is dominated by flavylium cation, which imparts red color to roselle [21].Despite that, the addition of roselle did not improve the redness intensity of white chocolate ganache compared to the control.On the other hand, increasing the concentration of butterfly pea powder resulted in decreasing lightness and increasing blueness intensity.Butterfly pea contains ternatin, the polyacylated derivative of delphinidin 3,3',5'-triglucoside [22].Increasing the concentration of roselle powders did not significantly affect the redness of white chocolate ganache.However, it caused a significant decrease in the lightness and yellowness intensity of white chocolate ganache.This may be due to the increasing concentration of beta carotene that could impart yellow color [23].Meanwhile, the increasing concentration of butterfly pea was accompanied by decreasing lightness and increasing redness and blueness intensity.This resulted from higher ternatin concentration, which contributed to the dark blue color that lowered the intensity and increased the blueness of the white chocolate ganache.

Water activity
In figure 2, it can be seen that the white chocolate ganache added to the butterfly pea flower has a higher water activity compared to the rosella flower at each concentration tested (1%, 1.5%, 2%).This is because the butterfly pea flower has a higher water content than the rosella flower, which is 92.08% [24].In figure 2 showed that increasing the concentration of each flower decreased the water activity of white chocolate ganache.In addition, it was also seen that the addition of butterfly pea and rosella flowers had lower water activity compared to the control.This is because the flowers are added to the white chocolate ganache in powder form so that the free water contained in the white chocolate ganache is bound to the flower powder thereby reducing the water activity.Therefore, the higher the concentration of flower powder added, the lower the water activity [25].This is also in accordance with the literature which stated that the low water activity is caused by the high concentration of dissolved substances, which in this study were edible flower powder [26].

Total soluble solids
Total soluble solid is a value that states the amount of solids dissolved in the liquid.The more solids dissolved in the liquid, the higher the total soluble solids.In figure 3 it can be seen that the control has a lower total soluble solids compared to the white chocolate ganache added with edible flowers.This is because the flowers added to the white chocolate ganache are in the form of a powder that can soluble in water so that the addition of flower powder can increase the total soluble solids [27].Figure 3 shows that the white chocolate ganache added with rosella flowers has a higher total soluble solids than the butterfly pea flowers.The result may be linked with the crude fiber content of rosella flowers that is lower than that of butterfly pea flowers.Rosella flowers have a crude fiber content of 16.65%, whereas the butterfly pea flower has a crude fiber content of 27.6% [28][29].Crude fiber is a fiber that cannot dissolve in water.Therefore, the more crude fiber, the more insoluble solids in the white chocolate ganache, so the total soluble solids are low.Therefore, the white chocolate ganache added with butterfly pea flowers has lower total dissolved solids than rosella flowers [30].
In Figure 3, it can be seen that the increased concentration of the butterfly pea and rosella flowers increased the total soluble solids of white chocolate ganache.This is because the higher the concentration of butterfly pea and rosella flowers added, the more flower powder that dissolves in the white chocolate ganache so that the total soluble solids of white chocolate ganache increases as the concentration of pea flowers and rosella flowers is added [27].

Hedonic test
Table 3 presents the effect of adding rosella and butterfly pea flower powder with different powder concentrations on the hedonic test results of white chocolate ganache with various attributes.Based on ANOVA analysis, the flower type factor significantly influenced the level of color preference.However, based on statistical analysis, the interaction between the types of edible flowers and the concentration of powder addition did not significantly affect panelists' preference scores on nine sensory attributes.Based on Tukey's further test, the factors of types of butterfly pea and rosella flowers with the concentration of flower powder addition did not have a significant effect on sensory attributes, including overall liking, color, aroma, sweet taste, bitter taste, sour taste, aftertaste, creaminess, and graininess.The panelists' level of acceptance for white chocolate ganache products ranged from a score of 6 to 7 on all the attributes tested, from 'slightly like' to 'like moderately'.This shows that increasing the powder concentration of each type of edible flower does not affect the preference level of the white chocolate ganache.Table 3 shows that the increase in butterfly pea concentration resulted in the decrease of panelists' overall liking score, even though it was not statistically significant.This might be due to the increase of ternatin pigment with malonylated 3,3',5'-triglucoside structure contained in butterfly pea that resulted in darker blue color of the white chocolate ganache and affected the decrease in panelists' overall liking [6].Blue color could affect the propensity to eat, as blue color could lower the appetite which may affect the panelists' liking [31].Table 3 also shows that increasing rosella powder on ganache can increase the panelists' overall liking, even though it was not statistically significant.Rosella contained anthocyanin (cyanidin-3-glucoside) imparting red color on the flower, which also improves the redness intensity on the white chocolate ganache with increasing concentration.Red color could be seen as more appetizing, which might increase the overall liking of roselle ganache with increasing concentration [31].Overall, white chocolate ganache, with the addition of rosella and butterfly pea flowers, has the potential to be a product that increases the use of edible flowers and is also liked by consumers.

Conclusion
Based on this study, the addition of butterfly pea flowers to white chocolate ganache has a higher water content and water activity compared to roselle flowers.However, the addition of butterfly pea flowers has a lower total soluble solid compared to roselle.Increasing the concentration of edible flowers decreases the water activity and water content.However, it increases the total dissolved solids in the white chocolate ganache.From the results of the color test, it can be seen that the ganache of the butterfly pea flower has a tendency to be blue (-b*), while the ganache of roselle has a tendency to be red (+a*) and yellow (+b*).The ganache of the butterfly pea has a darker color than the roselle.In addition, increasing the concentration of the butterfly pea flower in the white chocolate ganache increases the intensity of the blue color and makes the white chocolate ganache darker.Meanwhile, increasing the concentration of roselle powders made the white chocolate ganache darker and did not have a significant effect on the color intensity of the red color.Meanwhile, the results of the hedonic test did not show any significant differences between the treatments with attributes including overall liking, color, aroma, sweet taste, sour taste, bitter taste, creaminess, and graininess.The results of the hedonic test showed panelists' preference for white chocolate ganache with the addition of butterfly peas and roselle flowers, with an average score of 6 (slightly like) to 7 (like moderately).This indicates the opportunity of incorporation of butterfly pea and roselle powder to chocolate ganache.Further analysis on the functional properties of edible flower-added chocolate ganache is required.

4 Note:
Means with different superscript are significantly different (p < 0.05).

Figure 1 .
Figure 1.Results of water activity test of white chocolate ganache with the addition of edible flowers.

Note:
Means with different superscript are significantly different (p < 0.05).

Figure 2 .
Figure 2. Results of water activity test of white chocolate ganache with the addition of edible flowers.

6 Note:
Means with different superscript are significantly different (p < 0.05).

Figure 3 .
Figure 3.Total soluble solids test results for white chocolate ganache with the addition of edible flowers.

Table 1 .
Formulation of white chocolate ganache base.

Table 2 .
Color profile of white chocolate ganache with the addition of edible flowers.
Note: Means within the same column with different superscript are significantly different (p < 0.05).

Table 3 .
Hedonic test results for white chocolate ganache with the addition of edible flowers.