GUAR GUM ADDITION ON PHYSICAL CHARACTERISTICS OF EXTRUDED DRY CORN NOODLE FROM MIXTURE OF WET AND DRY

The drying process of corn noodles was an effort to increase the shelf life and it was a form of noodles diversification. The objective of this research was to study and analyze the effect of guar gum addition on the physical quality of the extruded dry corn noodle made from a mixture of wet and dry corn flour. Manufacturing dry corn noodles was conducted using wet corn noodles from a mixture of wet and dry corn flour, which was then dried in a tray dryer at a temperature of 60-70 °C for 1 1.5 hours. The treatments used were a combination of alum levels of 0.01%; moisture content of 80% (dry base); and guar gum concentration of 0%, 1%, and 2%. Physical properties of dry corn noodles included rehydration time, hardness, adhesiveness, suppleness, elongation, and cooking loss. The results showed that the optimum rehydration time for dry corn noodles was about 9 minutes. The addition of guar gum to the physical qualities of dry corn noodles tended not to be significant statistically, but as a score, an increase in guar gum levels tended to increase the elongation of dry corn noodles. While, increasing levels of guar gum tended to reduce the stickiness and cooking loss levels of them.


PENDAHULUAN
Dry noodles, according to SNI 01-2974SNI 01- -1996, are defined as processed products with a typical form of noodles that are dried with the addition of other permitted food ingredients. Dry noodles must have a minimum of 87% solids, which means that the moisture content must be less than 13%. Tan et al. (2009) explained that dry starch noodles should have a moisture content of 10-14.5% related to the prevention of mold growth. The moisture content of less than 10% can cause dry noodles that break easily during the transportation process. Dry noodles have a longer shelf life compared to wet noodles due to lower moisture content, which is for 6-12 months during good storage. The drying process in starch or non-gluten noodles is different from that of wheat-based noodles. Drying can be done by using conventional drying using sunlight or using a dryer at a certain temperature and time. Drying at 20ºC can cause noodles to break easily when cooked due to cracks that form on dry noodles. Inazu et al. (2002) explained the kinetics of drying on Japanese noodles (udon) by gradual drying, which was started at a low temperature (15-20ºC) and then followed by a temperature of 30-35ºC at high RH (70-80%) to a moisture content of 14% produced good noodles without cracking. However, the use of high temperatures can also be done like Baiano et al. (2006), who reported high-temperature drying (90ºC for 5 hours) produced good cooking and sensory quality. Several studies related to the manufacture of dry starch noodles using extruders have been carried out. Charutigon et al. (2008) reported making dry vermicelli from rice flour ingredients, Waniska et al. (1999) made dry corn noodles with a high cooking loss value of 47%, and Muhandri et al. (2019) reported the drying process with a fluidized bed dryer on extruded corn noodles. Also, the use of additives is applied to improve the quality of the noodles. Subarna et al. (2012) added monoglycerides in the manufacture of dry corn noodles where the qualities of hardness and elongation were better despite high levels of cooking loss and adhesiveness. Besides, hydrocolloids were also used in improving the quality of noodles, among others by Muhandri et al. (2013), who reported that the higher the guar gum concentration led to the higher the elongation and the lower the cooking loss of the noodles. Ratnawati and Afifah (2018) used guar gum, CMC, and carrageenan in a mixture of mocaf, rice flour, and cornflour. The manufacturing of these dry and wet starch noodles was made using dry flour, which is added with a certain degree of water. Making the dry noodles from a mixture of the wet and dry flour has never been done.
This study aims to improve the physical qualities of extruded dry corn noodles from a mixture of wet and dry cornflour. They are rehydration time, cooking loss, elongation, and texture profiles by adding different concentrations of guar gum.

The manufacturing process of dry corn noodles
The manufacturing of dry corn noodles was started with the manufacturing of wet corn noodles based on Aminullah et al. (2019). The initial stage was the process of corn flouring by using wet milling with alum treatment of 0.01% of the weight of water. Corn noodles manufacturing consisted of determining the proportion of wet and dry flour (Aminullah et al., 2016) which was mixed until a moisture content of 80% (bk) with the addition of salt (2% by weight of the dough) and guar gum (0%, 1%, and 2% by weight of the dough); steaming the dough at 100 °C for 15 minutes; extruding the dough using a paste extruder; steaming the noodles for 15 minutes at 100 °C. Then, the drying process was carried out using a tray dryer at a temperature of 60-70 °C for 1 -1.5 hours.

Physical analysis of dry corn noodles Determination of the rehydration time of dry corn noodles (Collado et al., 2001)
Five grams of noodles, that have been cut as long as 2-3 cm, were put into boiling water as much as 200 ml. Then, the strands of noodles were taken every minute, which were then placed between two watch glasses and pressed. The optimum cooking time was obtained when all of the noodles absorb water completely or when white dots did not form when the noodles were pressed.

Analysis of texture profiles (hardness and stickiness) (Chen et al, 2002)
Hardness analysis using the Texture Analyzer type TA-XT2i. The probe used was cylindrical with a diameter of 35 mm. The Texture Analyzer settings were as follows: pre-test speed of 2.0 mm/s, test speed of 0.1 mm/s, rupture test distance of 75%, measure force in compression mode, and force of 100 g. A rehydrated noodle strand with a length that exceeds the probe diameter was placed on the runway and then pressed by the probe to 75% strain. The result was a curve that showed the relationship between the required force for compression and time. Hardness value was indicated by absolute (+) peak, which was a maximum force, and stickiness value was indicated by absolute (-) peak. The unit of these parameters was gram force (gF).

Analysis of elongation percentage (Inglet et al., 2005)
A rehydrated noodle strand was wrapped around the probe with a distance between the probes of 2 cm and the probe speed of 0.3 cm/s. Elongation percentage was calculated according to equation (1). (1)

Analysis of cooking loss (Oh et al., 1985)
Five grams of dry noodles were boiled in 150 ml of boiling water during the rehydration time of dry corn noodles, then drained the noodles. After that, dried at 100 °C until the weight was constant, then weighed again. The cooking loss value was calculated using equation (2).

Data analysis
The resulted data were analyzed using Analysis of Variance (ANOVA) and Duncan post hoc test when p<0.05 via Statistical Product and Service Solutions (SPSS) software version 23.

Rehydration time of dry corn noodles
Rehydration time is the required time of the material to re-absorb water for obtaining a homogeneous texture. Table 1 shows that the noodles are still rather hard, and there are spots in the middle of the noodles in the 6 th to 8 th minutes. At 9 th minute, the noodles become soft and there is no spot in the middle of the noodles, whereas, at the 10th minute, the noodles are too 42 Aminullah et, al.
Penembahan Guar Gum sifat fisik mie soft. Based on these data, the selected rehydration time of dry corn noodles is 9 minutes. This selected rehydration time is by following Muhandri et al (2018) and Subarna et al. (2012), who reported the rehydration time of dry corn noodles, respectively, around 10 and 8 minutes. However, the length of the rehydration time is due to the consistency of dry corn noodles, that is more compact than dry wheat noodles, where the optimum rehydration time of dry wheat flour noodles are in the range of 3-5 minutes. Also, Subarna and Muhandri (2013) reported that dry corn noodles with the calendering process required rehydration time of about 4 minutes. This calendering process is a method used in the manufacturing process of wheat noodles. The noodles are still a bit hard, and there are spots in the middle of the noodles 7 8 9 The noodles are soft, and there are no spots in the middle of the noodles 10 The noodles are too soft

Hardness profile
Hardness is defined as an absolute (+) peak, which is the maximum force, which describes the force of the probe to suppress mi. The higher the peak (peak of the curve) shown by the curve, the higher the hardness of the materials.

Stickiness profile
Stickiness or adhesiveness is defined as an absolute (-) peak, which describes the amount of effort to pull the probe off the sample. The greater the negative area shown by the curve, the higher the stickiness value of the noodles. Based on the stickiness score, Figure 2 shows that the higher the guar gum concentration used tends to reduce the stickiness value, although it does not affect the stickiness value of the noodles statistically. It can be seen that the lowest stickiness value occurs at a 2% guar gum level, which is -1176.64 gF. While the highest adhesiveness at 0% guar gum content with a value of -1234.88 gF. Fadlillah (2005) and Kusnandar (1998) reported that the addition of guar gum can reduce the stickiness value of wet noodles.

Elongation profile
Percent of elongation shows the maximum length of the noodles that experience a pull before breaking up. Elongation is expressed in units of percent (%).  Figure 3 shows that the addition of guar gum on dry corn noodles does not affect statistically at α of 0.05. However, elongation score shows that increasing levels of guar gum can relatively increase the elongation of dry corn noodles. The highest elongation percentage is obtained with the addition of 2% guar gum, which is 232.73%. The addition of guar gum 0% produces dry noodles with elongation of 211.45%, while the addition of guar gum 1% give the elongation of 222.89%. Increasing levels of guar gum cause the binding capacity of the water to be higher, which causes a decrease in the hardness of the noodles, or the noodles become softer means that softer noodles do not break easily. This elongation value is by following Taqi

Cooking loss profile
Hou and Kruk (1998) stated that cooking loss was the most important parameter for wet noodle products, that are traded in the cooked form. The desired cooking loss value is relatively small. The lower cooking loss value indicates that the noodles have a good and homogeneous texture. Figure 4 shows that the higher the level of guar gum used, the lower the obtained cooking loss value. Increasing the concentration of guar gum to a certain concentration can reduce the cooking loss of the noodles because guar gum has a function as a water binder (Sozer, 2009), which distributes the water distribution in the material so that the bond between starch granules becomes stronger (Sivaramakrishnan et al., 2004). This is in line with Muhandri et al. (2013), who reported guar gum addition as much as 2% can reduce the cooking loss of wet corn noodles. The cooking loss value in this study is consistent with the research of Muhandri et al. (2013), who