The effect of sorbitol and white sweet potatoes (Ipomea batatas L.) inulin extract application on marshmallow physical, chemical and organoleptic properties

Marshmallow belongs to a high-calorie food that requires a low-calorie substitute for sucrose, one of which is sorbitol. Marshmallow has the potential to become a functional food with the addition of inulin contained within white sweet potatoes. Inulin refers to a type of fructan carbohydrate which contains fiber and has the potential as a prebiotic that is beneficial for the human’s body. This study aims to determine the effect of the addition of white sweet potato (Ipomea batatas L.) inulin extract and sorbitol on the physical, chemical and organoleptic characteristic of marshmallows and to obtain the best marshmallow’s formula through white sweet potato (Ipomea batatas L.) inulin extract and sorbitol addition. The completely randomized design method (CRD) applied in this study consisted of one factor, namely the difference in formulation between the concentration of white sweet potato inulin extract (2% and 3%) and the concentration of sorbitol (25%, 50%, and 75%). The statistical analysis utilized the One Way Analysis of Variance (ANOVA) method using SPSS. The results of this study indicated that the addition of white sweet potato inulin extract and sorbitol had a significant effect on tensile strength, density, moisture content, ash content, total calories, dietary fiber, and organoleptic characteristics of marshmallows. The best formula for marshmallows was formula 4 with the addition of 2% white sweet potato inulin extract and 50% sorbitol.


Introduction
Marshmallow refers to a confectionery product which is snack with soft foam texture in various shapes, aromas and colors. Marshmallow, when eaten, melts in the mouth since it is made from sugar or corn syrup, gelatin, and flavoring ingredients mixture that are whipped until fluffy (Nakai and Modler, 1999). Sorbitol belongs to a natural alcohol sugar with the chemical formula C 6 H 14 O 6 . Generally, sorbitol is in the form of white odorless non-cariogenic crystalline powder with the molecular weight of 182.17 g/mol and pH of around 7, and solubility of 2350 g/L. Its use in the food industry is very broad, including as sweetener, moisturizer, texture forming and softener. Sorbitol can also be used in diets for diabetics since its metabolic pathway is not dependent on insulin (has low energy and cannot be metabolized) (Marques et al., 2016). As a sucrose substitute sweetener, sorbitol has a calorific value of 2.6 kcal/g or equivalent to 10.87 kJ/g. Since it does not have toxic effects, it is safe for human consumption and does not cause dental caries and is very useful as sugar for diabetics and low-calorie diets (BPOM, 2008).
In general, people consume sweets out of liking and not to obtain the functional value of these foods. In marshmallow production, it can be combined with raw materials that will add functional value to the food, for example by using ingredients that naturally contain fiber. One of the food component with high content of dietary fiber and can be utilized in functional food is inulin, which also has the best prebiotic effect compared to other prebiotics (Roberfroid, 2007).
Sweet potato is a potential inulin source that can be utilized. According to Arfiani (2016) who has tested inulin level on several sweet potato varieties, such as white sweet potato, purple sweet potato, and yellow sweet potato, white sweet potato has the highest inulin content of 5.57% but is still in its yield form so that there are possible components other than inulin. Blanching and foam mat drying on white sweet potato inulin extraction has higher yield up to 22.53% , white Sweet Potato inulin extraction with a precipitation ratio of 1:2 for 12 hrs produced the best inulin yield of 7.72% (Yudhistira, Suswanti and Luwidharto, 2020), while the highest yield of yellow sweet potatoes is 8.80% eISSN: 2550-2166 © 2021 The Authors. Published by Rynnye Lyan Resources FULL PAPER with a solvent ratio of 1:3 (deposition time 18 hrs) (Yudhistira, Suswanti and Anindita, 2020). In this research, there are several stages including extraction, isolation, and marshmallows production using sorbitol sweetener and white sweet potato inulin with different concentrations of sorbitol and inulin. The limited research on inulin content in sweet potatoes is the background for choosing this commodity as research material. This study refers to the application of inulin in white sweet potato (Ipomea batatas L.) which is applied in the making of marshmallows as a food product.
Producing marshmallows with sorbitol sweetener with the addition of white sweet potato inulin extract is expected to produce the processed foods that contain natural prebiotics so as to produce food products that have functional value. The goal of this analysis is to establish the effect of the addition of white sweet potatoes (Ipomea batatas L.) inulin extract and sorbitol on the physical, chemical and organoleptic characteristics of marshmallows and to obtain the best recipe for marshmallows by adding white sweet potatoes (Ipomea batatas L.) inulin extract and sorbitol.

Extraction preparation
The preparation stage for the extraction of fresh white sweet potatoes covered the process of washing, stripping, chopping with a medium size (1-2 mm), drying with a cabinet dryer and flouring (80 mesh sieve) (Kosasih et al., 2015).

Extraction
The results of the extraction preparation were utilized for the extraction process of white sweet potato (white sweet potato flour) then mixed with the flour and aquadest (1: 5), the flour was soaked in aquadest for 1 hour and stirred in a water bath at 80°C for 30 mins, then filtered using double layer, and the water was evaporated with a vacuum rotary evaporator at a temperature of 73°C for 2.5 hrs (speed 60 rpm). The extraction process was carried out twice so that all inulin could be extracted (Kosasih et al., 2015).

Isolation
The total sugar was analyzed by taking 2 mL of the sample which had been diluted beforehand as needed, then added with 0.05 mL of 80% phenol solution and vortexed. The solution was then added with 5 mL of H 2 SO 4 , vortexed and left for 10 mins in the water bath at 25 o C and calibrated at 490 nm wavelength (Lorenz, 1959). The analysis of sugar reduction was started by taking 1 mL of the sample diluted according to the needs into the test tube, plus 0.33 mL of Rochelle salt 40% and 1 mL of DNS reagent, and then heated at 99 o C for 5 mins to form a brownish-red color then cooled at room temperature and with a spectrophotometer at a wavelength of 575 nm (Miller, 1959).

Precipitation inulin extract
The white sweet potato extract was adjusted to 30°B rix, then immersed in 95% ethanol with a ratio of 1: 2 for 12 hrs, deposited with a centrifuge for 15 mins (5000 rpm), and dried using an oven at 60 o C for 6 hrs (Kosasih et al., 2015), is modified by Yudhistira, Suswanti and Luwidharto (2020).

Marshmallow production
Marshmallow was made by 44 grams of gelatin dissolved in water at a temperature of 14-15℃ and left to stand for 10 mins. Furthermore, the white sweet potato inulin extract (2% and 3%) and sorbitol (25%, 50%, and eISSN: 2550-2166 © 2021 The Authors. Published by Rynnye Lyan Resources FULL PAPER 75%) were mixed according to the formulation and boiled for 5 mins. All formulations obtained were F1 = 100% marshmallow sugar, F2 = marshmallow 100% sorbitol, F3 = marshmallow 2% white sweet potato inulin extract: 25% sorbitol, F4 = 2% marshmallow extract white sweet potato inulin: 50% sorbitol, F5 = marshmallow 2% white sweet potato inulin extract: 75% sorbitol, F6 = marshmallow 3% white sweet potato inulin extract: 25% sorbitol, F7 = marshmallow 3% white sweet potato inulin extract: 50% sorbitol, F8 = marshmallow 3% white inulin extract sweet potato: 75% sorbitol. After that, the inulin and sorbitol extracts were mixed with the gelatin mixture in the basin and then stirred with a mixer at medium speed for 12 mins until foam forms, when the foam had formed, strawberry juice was added. The marshmallow was then poured on a skillet covered with cornstarch that had been mixed with icing sugar. After smoothing it, the top surface of the marshmallow was sprinkled with icing sugar that had been mixed with cornstarch. The next stage of marshmallows is brooded for 24 hrs (Jalasena and Anjani, 2015; Sebayang et al., 2016).

Data analysis
Sensory, physical and chemical analysis was statistically carried out using the one-way ANOVA method. If it shows significant results, it is followed by a significant difference test using Duncan's Multiple Range Test (DMRT) at the significant level α = 0.05.

Tensile strength
As seen in Table 1, marshmallow tensile strength value is in the range of 1.980 -4.127 N. The tensile strength value of marshmallow with white sweet potato inulin extract and sorbitol is directly proportional to the addition of white sweet potato inulin extract and sorbitol. The increase in tensile strength values indicates that the texture of marshmallows becomes more viscous and difficult to break during the testing process using Universal Testing Machines (UTM). The high value of tensile strength can indicate that the quality of marshmallows produced is getting better (Yudhistira et al., 2017).
According to Gontard et al. (1992), the factors that influence the tensile strength of a material are the total dissolved solids and the interaction of molecules in them. The difference in the amount, type, and position of sulfate groups also the presence of ions will affect the gel formation process. Kaya et al. (2015) and Desrosier (2008) suggest that gel formation can be influenced by pectin, sugar, acids, and water mixture. The gel formation affects the plastic texture, so this plastic texture makes marshmallows more viscous and not easily broken. Arfiani (2016) states that white sweet potatoes contain fiber including pectin and inulin.
The texture of marshmallows formed is influenced by the mixing process which produces foam in the dough which then becomes marshmallow. Foam in food refers to the continuous dispersion of air bubbles in the liquid to solid or gas phases and is stabilized by active ingredients (Damodaran, 2008 FULL PAPER produced using high sugar syrup and active agents such as protein, which can be combined with polysaccharides (Lees and Jackson, 1973). Sugar, protein, and polysaccharides can interact with each other and will affect foaming capacity, foam stability and rheological properties. The aeration process will affect changes in texture and rheological properties causing different taste and appearance (Campbell and Mougeot, 1999).

Density
Low marshmallow density values indicate better quality compared to marshmallows with high density, since marshmallows with low density are able to trap more air so it is softer and lighter when consumed and has higher volume (Trilaksani et al., 2009). The amount of volume formed is influenced by the presence of pectin, which serves as gel-forming agent and thickener (Hariyati, 2006).
The density test that has been analyzed statistically using one-way ANOVA and DMRT tests shows that marshmallow density values significantly affected by the addition of white sweet potato inulin extract and sorbitol. The results in Table 1 show that density values in the eight marshmallow formulations range from 0.572 -0.839 g/mL. According to SNI, marshmallow density values are 0.454 g/mL -0.772 g/mL (Trilaksani et al., 2009). The results of this study suggested that the marshmallow density value with the addition of white sweet potato inulin extract and sorbitol was greater than SNI. Furthermore, the density value also tended to decrease with the greater sorbitol concentration and increases with the greater concentration of white sweet potato inulin extract. This was because white sweet potato inulin extract belongs to a type of fiber that contains pectin which is a gelatinizing agent that can affect marshmallow products and different textures on marshmallows (Koswara, 2009). Table 1 shows that the addition of white sweet potato inulin extract and sorbitol significantly affected the value of marshmallow water content. Marshmallow water content calculation is in accordance with SNI 3547.2:2008 concerning the standard quality of soft confectionery with the maximum value of 20% (BSN, 2008). Calculation of the highest marshmallow water content was at F2 (19.794%) in the 100% sorbitol formulation and the lowest at F6 (10.549%) in the formulation of 3% white sweet potato inulin extract and 25% sorbitol. The increase in water content is directly proportional to the addition of white sweet potato inulin extract and sorbitol.

Water content
Higher water content was caused by sorbitol being hygroscopic and able to bind free water in the product. The higher the addition of sorbitol in food, the more free water is bound (Aini et al., 2016). When sorbitol is added to food products, it has a hydroxyl group that functions to bind free water outside and forms hydrogen bonds with water, while the effect of adding white sweet potato inulin extract is the increase of water content due to the nature of inulin that dissolves in water (Karimi et al., 2015). Table 1 shows the results of the ash content from the 8 marshmallow formulations with white sweet potato inulin extract and sorbitol. The results showed that marshmallow ash content with the addition of white sweet potato inulin extract and sorbitol did not deviate from SNI 3547.2:2008 regarding the standard quality of soft confectionery which is a maximum of 3% (BSN, 2008). One-way ANOVA and DMRT statistical test results showed the addition of white sweet potato inulin extract and sorbitol on marshmallow significantly affected the ash content. Sartika (2009) states that the lower ash content the better quality of marshmallows produced, based on this theory the best marshmallow formulation is at F5 (0.329%). From the results of this study, the marshmallow ash levels were getting higher with increasing white sweet potato inulin extract and sorbitol. This was because the inulin extract derived from white sweet potato and sorbitol contains various minerals. Bradbury and Halloway (1988) state that sweet potato (Ipomoea batatas L.) is one of the agricultural products that contain carbohydrates and high-calorie vitamins (A, C, B1, and B2), minerals (Fe, P, and Ca), protein, fat, and fiber source. Sweet potatoes contain water (71.1%), starch (22.4%), protein (1.4%), fat (0.2%), vitamin A (0.01-0.69/100 g), and an adequate mineral source. These minerals will increase the ash content of the product. Ash content associated with minerals of a product and the addition of additional inorganic materials to the product will increase the ash content of the product (Suhardi et al., 2003). Table 1 shows the results of total calorie tests on marshmallows with white sweet potato inulin extract and sorbitol using the bomb calorimeter method. One-way ANOVA and DMRT statistical tests showed that the addition of white sweet potato inulin extract and sorbitol significantly affected the calorie value of marshmallows. The results showed that the greater the percentage of white sweet potato inulin extract and sorbitol added, the greater the caloric content. (BPOM, 2008) states that the calorific value is 2.6 kcal / g or equivalent to 10.87 kJ/g. According to the previous statement, marshmallow with a greater percentage of sorbitol should have the lower calorie content. However, the addition of sweet potato inulin extract affects the amount of calories in marshmallows due to measurement that often provides incorrect information when distinguishing between carbohydrate types that are available and non-available (Southgate, 1975). Chemically, inulin is a mixture of oligomeric and polymers chain with several fructose molecular variables that join β-2,1 glycoside bonds and usually includes glucose molecules at the end of the chain (Gao et al.,2016). Thus, based on this theory it can be assumed that white sweet potato inulin extract on marshmallows is read by the test equipment as calories in marshmallows causing calorie content on marshmallows with the addition of white sweet potato inulin extract increases. Therefore, further studies on testing calories in marshmallows by the addition of white sweet potato inulin extract and sorbitol with other methods than bomb calorimeter are needed. Table 1 shows the results of the analysis of dietary fiber content on marshmallows white sweet potato with inulin extract and sorbitol. The highest dietary fiber content is in F5 (2.805%) with a formulation of 2% white sweet potato inulin extract and 75% sorbitol. The results showed that the addition of a percentage of white sweet potato inulin extract and sorbitol increased dietary fiber content in marshmallows. This is because the fiber content in white sweet potato inulin extract causes the fiber content in marshmallows to be higher. Inulin refers to a natural oligosaccharide produced by many plants. Inulin in plants is stored in roots or tubers (Hidayat, 2006). Inulin is also a natural polymer with fructose monomers. The amount of fructose monomers in a polymer chain varies depending on the source. Inulin is a type of fructose or fructose polymer (fructose monomer combined chain) which mostly contains about 35 fructose units connected to each other in straight chain by β-2,1 glycoside bond (Gao et al., 2016).

Color
Marshmallows are generally white, but can also be of other colors if additional food coloring is added according to consumer's preference. In this study, no food coloring was added on marshmallows with the addition of white sweet potato inulin extract and sorbitol. Based on the results, all marshmallow formulations had the dominant white color, which means the addition of white sweet potato inulin extract and sorbitol had no effect on the color of the marshmallows produced. Table 2 shows that panelists assess all marshmallow formulation color parameters at preference level of 3.18 -3.98 or equivalent to neutral-like. According to panelists, the increase of white sweet potato inulin extract and sorbitol percentage had no effect on the color of marshmallows produced, as shown by only F1 formulation with 100% sugar which was in a different subset than the other formulations. This was because F1 was a formulation that contained the most sugar, thus the heating process could cause a Maillard reaction between sugar and amino acids contained in the sugar so that it produced a brown color.

Aroma
Other ingredients besides inulin extract of white sweet potato and sorbitol used in marshmallows production in this study consisted of sugar, gelatin, cornstarch, icing sugar, water, and strawberry essence. Out of these ingredients, some that have specific aroma is gelatin, the characteristic aroma of gelatin, icing sugar, the sweet aroma, and strawberry flavor essence, the aroma of strawberry. The aroma of these ingredients will affect the panelists' evaluation of marshmallows with the addition of white sweet potato inulin extract and sorbitol.
Based on one-way ANOVA and DMRT statistical tests, the addition of white sweet potato inulin extract and sorbitol significantly affected the aroma of marshmallow. Table 2 shows the aroma parameter values on marshmallows at the neutral-like level (3.60 -4.22). The formulation whose aroma was most preferred by panelists was F3 (4.22) with 2% white sweet potato inulin extract and 25% sorbitol. This shows that panelists dislike marshmallows that use high concentrations of white sweet potato inulin extract and sorbitol because, with the increase in the use of white sweet potato inulin extract and sorbitol, the distinctive aroma of white sweet potato inulin extract and sorbitol also increases. Table 2 shows the results of panelists' preference for taste parameters of marshmallow with the addition of white sweet potato inulin extract and sorbitol at values of 3.18 -3.95. The addition of sorbitol has an effect on taste because the more sorbitol is used, the marshmallow will be sweeter. The higher the percentage of sorbitol used, the higher the level of panelists' preference. This shows the success of using sorbitol as a sucrose substitute sweetener, with the advantage of sorbitol having a lower sweetness level compared to sucrose. The sweetness level of sorbitol is 0.5-0.7 times of sucrose with a calorific value of 2.6 kcal/g or equivalent to 10.87 kJ/g (BPOM, 2008).

Texture
In Table 2, the most preferred texture of marshmallow with white sweet potato inulin extract and sorbitol is F4 with 2% white sweet potato inulin extract and 50% sorbitol. The higher addition of sorbitol will produce a non-crisp texture that is less preferred by panelists. Sorbitol belongs to a very hygroscopic sweetener that has the ability to bind free water. The higher the addition of sorbitol, the more free water is retained (Aini et al., 2016). Texture parameter is also related to the physical properties of marshmallows, which is tensile strength. As previously explained, marshmallow tensile strength value with the addition of white sweet potato inulin extract and sorbitol tends to increase with the greater concentration of white sweet potato inulin extract and sorbitol used. The high value of tensile strength can indicate the quality of marshmallows produced is getting better. If the tensile strength parameter, the best formulation is with the highest tensile strength, but in organoleptic test texture parameters, panelists tend to prefer marshmallows which break easily or in other words have low tensile strength values.

Overall
The most preferred formulation by the panelists was F4 (3.78), namely marshmallow with white inulin extract formula 2% sweet potato and 50% sorbitol. The statistical test results also showed that the addition of white sweet potato extract and sorbitol inulin extract had a significant effect on the overall parameters.

Best formula determination of marshmallow with white sweet potato (Ipomea batatas L.) inulin extract and sorbitol
The determination of the best treatment is used to determine which treatment is best from a process. Determination of the best treatment is done by using a scoring test with the effectiveness index method. The principle of this test is to give a value in accordance with the contribution of a parameter to the product produced (De Garmo et al., 1984). Each parameter is given a value of 0-1. The greater effect of a parameter on the expected results, the greater score will be given to these parameters and vice versa.
The parameter that was given the highest value or equal to 1, is the total calorie and dietary fiber parameters because this study applied sorbitol which has a lower sweetness and calorie level than sucrose. By testing, the total calories in all formulations were compared to the calorific value of marshmallows which applied sucrose sweeteners. Furthermore, the parameters of dietary fiber were also given the highest rating because of the addition of white sweet potato inulin extract to marshmallows in this study. In line with the research by Arfiani ( 2016), white sweet potato contains inulin which is a type of carbohydrate that contains fiber and is classified as a prebiotic. Therefore, testing of dietary fiber in all formulations in this study is needed to determine how much the influence of dietary fiber with the addition of sweet potato inulin extract.
Scoring test results on marshmallows with white sweet potatoes inulin extract and sorbitol can be seen in Table 3, where the best treatment has the highest yield value (NH) among other NH formulations. In Table 3, the highest NH is in F4 (66.225), so it can be concluded that F4 is the best treatment of all the formulations in this study. Characteristics of marshmallow with F4 formulation of 2% white sweet potato inulin extract and 50% sorbitol are tensile strength value of 2.880 N; density of 0.573 g/mL; water content of 17.094%; ash content of 0.510%; total calories of 2664.949 cal/g; and dietary fiber of 1.184%. Whereas, the sensory test has a color value 3.250; aroma of 4.125; taste of 3.950; texture of 3.600; and overall, of 3.775.

Conclusion
The addition of white sweet potato (Ipomea batatas L.) inulin extract and sorbitol significantly affected physical properties (tensile strength and density), chemical (water content, ash content, total calories and dietary fiber), and organoleptic (color, aroma, taste, texture, and overall) of marshmallows. F4 is the best of all formulations in this study. The overall parameter eISSN: 2550-2166 © 2021 The Authors. Published by Rynnye Lyan Resources FULL PAPER showed the overall results of all marshmallow formulations with white sweet potato inulin extract and sorbitol according to panelists. The most preferred formulation by panelists was F4 (3.78), marshmallows with 2% white sweet potato inulin extract and 50% sorbitol. Statistical test results also showed that the addition of white sweet potato and sorbitol inulin extract significantly affected the overall parameters.
Characteristics of F4 formulation marshmallow with 2% white sweet potato inulin extract and 50% sorbitol are tensile strength value of 2.880 N; density of 0.573 g/ mL; water content of 17.094%; ash content of 0.510%; total calories of 2664.949 cal/g; and dietary fiber of 1.184%. Whereas the sensory test has a color value of 3.250; aroma of 4.125; taste of 3.950; texture of 3.600; and overall, of 3.775.