The Effect of Curdlan Hydrocolloid on The Characteristics and Sensory of Non-Gluten Noodles

This study aims to determine the effect of the addition of curdlan hydrocolloid on the texture of non-gluten noodles. This research was conducted with 10 treatments (sorghum flour + 0.1% curdlan, sorghum flour + 0.3% curdlan, sorghum flour + 0.6% curdlan, mocaf flour + 0.1% curdlan, mocaf flour + 0.3% curdlan, mocaf flour + 0.6% curdlan, purple taro flour + 0.1% curdlan, purple taro flour + 0.3% curdlan, purple taro flour + 0.6% curdlan, wheat flour + 0% curdlan). Observational data were processed using Two-Way ANOVA, One-Way ANOVA, and Independent T-test. The results showed that the addition of curdlan hydrocolloid and type of flour used had an effect on elongation, rehydration capacity, water holding capacity, carbohydrate content, protein, fiber, and organoleptic results in taste, aroma, color, texture, and overall panelist acceptance with the best formula being purple taro flour + 0.6% curdlan.


Introduction
The 17 Sustainable Development Goals include, among other goals, the goals of achieving zero hunger and good health and well-being.This research was aimed to develop a gluten-free noodle product based on locally available sources.The result of the research was expected to contribute to innovative, healthier food products to fulfill the 2 nd goal, namely zero hunger by developing food based on local sources and to fulfill the 3 rd goal, namely health.and well-being, by developing non-gluten noodle.Gluten is a protein naturally found in some grains including wheat, it helps provide elasticity, structure, and a chewy texture to the dough of bread and noodle.Gluten can also help the formation of tissue in cooked food resulting in a good texture and sensory satisfaction and elimination of gluten in food causes a poor food texture.However, the demand for gluten-free foods is increasing due to the increasing frequency of celiac disease.However, the texture of gluten-free products is usually not as good as products that contain gluten [1].On the other hand, there is an hydrocolloids material known as Curdlan that is potentially used as a substitute of gluten in providing elastic structure in foods.Hydrocolloids are group of long-chain polymers that are easily dispersed, completely or partially soluble, and tend to swell in water [2].Curdlan is a hydrocolloid which at normal temperatures can swell after absorbing water.This hydrocolloid is insoluble in water in temperature of below 54 o C. Curdlan can dissolve in alkaline solutions with a pH above 11.After heating, curdlan can absorb 50 times water to form a gel.When heated at a low temperature of 55-65 o C and then cooled to below 40 o C, a heat-reversible gel is formed.Heating at high temperatures (> 80 o C) can form heat-resistant gels with stronger gel strength.The gel that is formed cannot be changed by heating even after being frozen and heated, the gel strength will remain stable [3].Curdlan gum is a fermented polysaccharide that has a complex tertiary structure.It is a member of the molecule known as (1,3)-ß-glucan.Curdlan is produced from the fermentation of Alcaligenes faecalis var.myxogenes in a medium consisting of glucose, nitrogen source, and small amounts of minerals.The crude curdlan formed in the medium is dissolved in alkali, separated from the microorganisms, purified, and then dried into a powder [4].As a food additive, curdlan can improve the ability to hold moisture in food, the texture of elasticity, stability, and thickness, which can improve mouthfeel.Curdlan is usually applied to meat products, such as meatballs, tofu products, vegetarian products, and bakery products.Curdlan can also serve as a source of fiber and replace fat in food.Curdlan is effective in reducing cooking loss, increasing water absorption, and improving textural properties in food.It is used in tofu, to improve texture during freezing and thawing, used in surimi to increase elasticity and also used in meat products to increase water holding capacity [5].This research will use locally available ingredients such as flour of sorghum (Sorghum bicolor), modified cassava flour (mocaf), and purple taro (Colocasia esculenta) to make gluten-free noodles with the addition of curdlan hydrocolloid.The addition of curdlan hydrocolloid is expected to improve the texture of gluten-free noodles by producing a good chewy texture that is comparable to wheat noodles.This research was caried out to explore the possibility of making non-gluten noodle using taro, sorghum and mocaf flours with addition of curdlan, to get the best formulation in terms of sensory characteristics.

Materials and Methods
The equipment used in the noodle-making process were basins, spatulas, spoons, stoves and LPG gas, scales, and noodle cutters (Re-Noodle).The materials used in the noodle-making process were water, salt, oil, wheat flour (of Cakra Kembar®), sorghum flour, mocaf flour, purple taro flour, and curdlan hydrocolloid from OPAL BIOTECH®.

Sample Preparation
The making of the noodles sample in this study was carried out using the following formulas:

Sensory Evaluation
The sensory test was divided into 5 rounds, namely, sensory test for (1) samples of noodles made of sorghum with curdlan of 0.1%, 0.3% and 0.6%; (2) samples of noodles made of mocaf with curdlan of 0.1%, 0.3% and 0.6%; (3) samples of noodles made of taro with curdlan of 0.1%, 0.3% and 0.6%; (4) samples of noodles made of sorghum, mocaf and taro with curdlan 0.6% and finally; (5) samples of noodles made of wheat flour (control), with the best formula i.e., taro with curdlan 0.6%.The aimed of round 1 st to 4 th was to find the best percentage of curdlan and the best flour type, whereas the round 5 th was to compare the best formula with control.Noodle samples were prepared in the form of raw noodles that had been boiled in boiling water for 2 minutes and drained.This sensory test was carried out by 30 untrained panelists without any specific criteria.The parameters evaluated included taste, aroma, color, texture and overall acceptability, which were all assessed by applying a 5-point hedonic scale: (1 = extreme dislike; 2 = dislike; 3 = neutral; 4 = like; 5 = extreme like) [6].Each round of sensory test was conducted only once.

Analysis of Noodles Elongation
The elongation test was carried out using a texture analyzer (Shimadzu EZ Test).A sample of cooked noodles was wrapped around a probe to test the elongation of the sample.This test was done to see how strong or brittle the noodle strands before broken [7].Analysis of Noodles Rehydration The noodle rehydration capacity test was carried out by finding the difference between the weight of the noodles before cooking and the weight of the noodles after cooking.The calculation results are then divided by the weight of the noodles before cooking and multiplied by 100% [8].

Analysis of Noodles Water Holding Capacity
The water-holding capacity test on the noodle samples was carried out using the centrifugation method.The noodle sample, which has a known weight (1 g), is put into a centrifuge tube and given 40 mL of distilled water.The sample was shaken for 1 hour then centrifuged at 2000 rpm for 30 minutes.The resulting liquid is separated from the solid and the liquid was weighed [9].

Analysis of Carbohydrate, Protein and Fiber
The proximate analysis of the noodle samples was determined by analyzing the levels of carbohydrates, protein and fiber in the samples.The carbohydrate content was determined by using the Luff Schoorl method [10], the protein content was determined by using the Kjeldhal method [11], and the fiber content was determined by using the Gravimetric method [12].

Statistical Analysis
All noodle's characteristics analysis were performed in triplicate and both sensory and characteristics analysis was reported as mean ± Standard Deviation.The sensory result was analyzed by using Two-Way ANOVA since it consisted of 2 variables (types of flour and curdlan concentration), while the noodle characteristics result was analyzed by using One-way ANOVA using IBM SPSS software.

Sensory Evaluation
Sensory evaluations were carried out to compare the taste, aroma, color, texture, and overall, of each sample with 30 untrained panelists.Data from this sensory evaluation were then analyzed using Two-way ANOVA.

Taste
From the type of flours used, there was a significant difference in the preference of the flours while the curdlan concentration did not affect the taste.This is because curdlan hydrocolloid is a neutral polysaccharide that is tasteless [13].It was shown in Figure 2, that the wet noodle that was most liked by the panelists was the noodle sample made from purple taro flour because it had a savory and slightly sweet taste and mocaf, because it had a savory taste of cassava, while sorghum flour was considered to have the least taste preference [14,15].The least preference of sorghum might be caused by tannin compounds contained in sorghum flour.Tannin compounds that gave astringent and bitter tastes which affect the taste of wet noodles [16].

Aroma
From the type of flour used, there was a significant difference in the preference, while the curdlan concentration did not affect the aroma.This is because curdlan hydrocolloid is a neutral polysaccharide that has no aroma [13].Figure 3 shown that the aroma that the panelists liked the most was purple taro flour noodles.This was due to purple taro flour had a slightly sweet aroma [14].Mocaf flour has a faint aroma of cassava which was not common in noodle, so panelists did not like the aroma [15].The sorghum flour noodle sample was not liked by the panelists because it had a moist or musty aroma which is characteristic of the aroma of sorghum flour [17].

Color
From the type of flour used, there was a significant difference in the preference of color while the curdlan concentration did not affect the color.This was because curdlan hydrocolloid is a neutral white polysaccharide [13].From Figure 4, it can be seen that the color of mocaf and sorghum flour noodle were not favored by the panelists.This was because the noodle samples with sorghum and mocaf flour had a pale beige color which was less attractive.Whereas the purple taro flour noodle was most preferred by the panelists because it had a light purple color due to the anthocyanin content in purple taro [18].

Texture
From the type of flour used, there was no significant difference of preferences.However, the concentration of curdlan significantly affected the preference.This was because curdlan hydrocolloid interacts with starch contained in flour by inhibiting the swelling and degradation of starch granules resulting in a chewy texture.The type and content of starch in each flour also affected the preference.The difference in texture values for different flours in the same concentration of curdlan is due to the starch content present in each flour, of which, sorghum flour having a starch content of 67.67% -74.82%, mocaf flour of 77.84%, and purple taro flour of 70-80% [19,20,21].Figure 5 also revealed that the concentration of curdlan affected the texture preference of the noodles, of which, the more curdlan added, the better the texture preference.This was because curdlan hydrocolloids can form a gel when heated in water.The results of curdlan gel formation can give a chewy texture to the noodles [5].

Overall
From Figure 6, it can be seen that the noodle sample that had the highest curdlan concentration (0.6%) has the best sensory results in terms of taste, aroma, color, and texture.All samples with 0.6% curdlan concentration were then compared again to determine the best formula.

Determination of the Best Formulation (Curdlan Concentration 0.6%)
The sensory results showed that there were significant differences between taro flour and sorghum and mocaf.From the data above, it can be seen that the purple taro flour noodle sample had the best organoleptic score of 3.53 ± 0.303, which was followed by the mocaf flour noodle sample with score of 2.61 ± 0.320, and the sorghum flour noodle sample with score of 2.37 ± 0.229.The taste of sorghum noodle was of 2.67 as the lowest score.The highest noodle taste was 3.37, namely for purple taro noodles.The highest aroma of noodles was at 3.37, namely purple taro flour noodles, while the aroma of sorghum noodles was 2.20 which was the lowest aroma.The highest noodle color was 3.97, i.e., taro noodle and the lowest was the color of sorghum noodles i.e., 1.90.The highest noodle texture was 3.40 i.e., taro noodle and the lowest was 2.70 i.e., mocaf noodle.In the sensory test of taste, aroma, and texture, it can be seen that the flour of sorghum and mocaf were not significantly different, while the purple taro noodles had significantly different in sensory score.The color and overall formulations of sorghum, mocaf, and purple taro noodles had significantly different properties.This shows that there were differences in one formulation with another formulation in each characteristic of the noodles.The higher the score of organoleptic test, the higher the quality of the noodles [22].

Comparison of Control with Best Formula
The sensory test of taste of the best formula and control samples were not significantly different, but the color, aroma, texture and overall characteristics of the two samples were significantly different.Panelists preferred the aroma and color of purple taro flour compared to wheat flour noodle.However, in terms of texture, the panelists preferred the control noodle compared to the best formula sample.This was because wheat flour noodle samples contain gluten protein which affects the elastic texture of the noodle samples compared to the best formula samples which do not contain gluten protein [23].The addition of curdlan hydrocolloid of 0.6% to the best formula noodle was not able to compensate the elasticity of the wheat flour noodle.

Sensory Test
Best Formula (Taro with 0.6% Curdlan) Noodle Elongation The results of the elongation test from the control and the best formula samples showed that there was a significant difference.The control sample had a higher elongation value than the best formula sample.This is because the raw material for the control sample was wheat flour which contained gluten protein than purple taro flour.The high gluten protein content helps the formation of a denser and more continuous starch protein network.Therefore, the best formula sample has a low elongation value which indicated that the noodle strands of the purple taro flour sample was brittle and broken easily [23].

Control
The results of physical characteristic, namely elongation, rehydration and water holding capacity between the best formula and control shown in the following Tabel 3.

3.3.
Noodle Rehydration The results of the rehydration test from the control and the best formula samples showed that there was a significant difference between the two samples.The best formula sample had a higher rehydration value.The rehydration capacity of the noodles not only depends on the protein and starch content of the flour used but also the curdlan added.The higher the protein and starch content of the raw materials used, usually the higher the rehydration [24].The protein content in wheat flour ranges from 8-13% and the protein content in purple taro flour is around 3.9% [25,26].Flour with a high protein content absorbs more water than flour of a low protein content [24].However, the best formulation had higher rehydration capacity compared to the control formulation.This was because apart from the protein content, the starch content in the flour also affects the water absorption capacity of the noodle dough.The starch content in wheat flour is ± 70% and the starch content in purple taro flour is 80% [27,28].If the starch content of the raw materials used is higher, the starch gelatinization process and water absorption will occur more quickly.The number of hydroxyl groups in starch will increase the water absorption of noodle dough when it is cooked [27].

Analysis of Noodles Water Holding Capacity
The results of the water-holding capacity test of the control and the best formula showed that there was a significant difference between the two formulations.The best formula samples have higher water holding capacity.Water binding capacity is generally influenced by protein content.The higher the protein content of the raw materials used, the higher the water-binding capacity of the final product.However, the addition of curdlan hydrocolloid to the best formula helped increase the water-holding capacity of the best formulas.This is because the water-holding capacity of a product is generally influenced by several factors such as hydration, hydrogen bonding, and from hydrophobic interactions to form a gel network where water will be trapped in the heating process.In this experiment, the addition of curdlan hydrocolloid increased the formation of hydrogen bonds and hydrophilic interactions so that the water-holding capacity and rehydration also increased [29].

3.5.
Analysis of Carbohydrate, Protein and Fiber The results of the analysis of carbohydrate, protein, and fiber content from the control and the best formula samples showed that there were significant differences between the two formulations.The best formula sample had a higher carbohydrate content than the control sample.Purple taro flour generally has a carbohydrate content of around 86% while wheat flour generally has a carbohydrate content of around 74% so the formula of purple taro flour had higher carbohydrate content [30,31].The best formula sample had lower protein content than the control sample.This is because purple taro flour generally has a protein content of around 3.9% whereas wheat flour generally has a protein content of around 13% [25,26].The best formula sample has a higher fiber content than the control sample.This is because, generally, purple taro flour has a fiber content of than wheat flour [32,33].The addition of curdlan hydrocolloid also helps increase the fiber content of the purple taro flour noodle sample because curdlan is a additive that has been approved by the FDA as an addition to the fiber content in food [34].

Conclusion
It can be concluded that of the three types of flour used, there were significant differences between taste, aroma, color, and overall.The curdlan concentration affected significantly in the texture and overall sample.However, addition of curdland did not affect significantly in taste, color, and aroma.The noodle sample with purple taro flour with the addition of 0.6% curdlan was the most preferred in sensory test, therefore it was chosen as the best formula.The organoleptic results between the control sample and the best formula were not significantly different in terms of taste but were significantly different in terms of aroma, color, texture, and overall.Physicochemical analysis of the two samples also showed significant differences in elongation, rehydration capacity, water holding capacity, carbohydrate, protein, and fiber content.In term of protein content, the best formula of wet noodle resulted from this experiment did not meet SNI 2987-2015 requirements, namely a minimum protein is 9%.

Tabel 4 .
Comparation of Carbohydrate, Protein and Fiber Content of Best Formula and