CHARACTERISTICS OF COMPOSITE FLOUR MADE OF KIDNEY BEAN AND SOYBEAN

. Kidney beans and soybeans have the potential to be developed because they contain good nutrient. Kidney beans and soybeans are sources of vegetable protein. One form of development of legume products is composite flour. The aim of this study was to analyze the physical and chemical characteristics of composite flour made of kidney beans and soybeans. The experiment was designed using Completely Randomized Design with nine treatments and each treatment was replicated three times. The factor investigated was formulation of composite flour made from kidney bean and soybean (90%:10%; 80%:20%; 70%:30%; 60%:40%; 50%:50%; 40%:60%; 30%:70%; 20%:80%; and 10%:90%). The swelling power, solubility, color, white degree, moisture content, ash, protein, fat, and carbohydrate content were analyzed. The results showed that the higher percentage of soybean flour caused a decrease on swelling power, white degree, and redness of composite flour, but it increased the value of solubility, lightness and yellowness of composite flour. Composite flour with higher percentage of kidney bean flour had higher carbohydrate level, while composite flour with higher percentage of soybean flour had higher protein and fat content. The moisture contents of composite flour made of kidney bean and soybean were in accordance with the standard for beans flour products.


Introduction
Kidney beans and soybeans are types of legumes that have the potential to be developed.
Kidney beans production in 2020 was 66,210 tons (Badan Pusat Statistik, 2020), while soybean production in 2019 was 424,190 tons and the number increased to 613,300 tons in 2020 (Setyawan & Huda, 2022). The production of kidney beans and soybeans was quite high, but it was unbalanced with the amount of consumption. According to Badan Ketahanan Pangan (2021), the consumption of nuts in Indonesia has decreased from 26.5 g/capita/day in 2019 to 25.0 g/capita/day in 2020. Setyawan and Huda (2022) stated that the average consumption of soybeans in 2015-2020 was 2,953,022 tons. One attempt to increase the use and consumption of kidney beans and soybeans is processing the kidney beans and soybeans into food products.
Processing legumes product into flour is one way to increase the use of kidney beans and soybeans as food products because flour is more practical to use and has a longer shelf life.
Moreover, kidney bean flour and soybean flour can be processed into composite flour. Composite flour is a mixture of various types of flour (two types of flour or more), which is done with the aim to get flour with better characteristics and higher nutrient content (Sitanggang, 2016). Composite flour could be made from a mixture of tubers flour, legumes flour, cereals flour, fruit, and vegetable flour with or without wheat flour (Astuti et al., 2014;Yuniarsih et al., 2019;Ardiyani et al., 2021;Kambabazi et al., 2022). The mixing of flour is conducted with the same mesh size (Hernawan, 2017).
Composite flour has been used extensively and successfully in food products production (Hasmadi et al., 2020), such as bakery products and pastries (bread, biscuits, cookies, and pasta) (Noorfarahzilah et al., 2014). Composite flour is made from legumes/nuts/beans without addition of other flour, including: composite flour from cowpea-soybean-red bean flour (Mbofung et al., 2002), chickpea-soybean flour (Hemeda et al., 2018), and soybean-mung bean-red kidney bean flour (Ratnawati et al., 2019). In this study, composite flour was made from soybean and kidney bean flour. Composite flour from kidney bean and soybean has the potential to be developed as a raw material for processing food products, such as cake (Astuti et al., 2014), nutrimat bar (Wiranata et al., 2017), and tortilla (Syaiful et al., 2022). Comparison between each flour in making of composite flour will affect the characteristics of the composite flour produced. The aim of this study was to observe the effect of kidney bean flour and soybean flour formulation on the physical and chemical properties of composite flour.

Materials
The materials used in this study were kidney beans, soybeans, water, electric oven, blender, sieve 80 mesh, polypropylene packaging, sealer, digital scale, and basin.

Research Design and Parameters
This study used a non-factorial completely randomized design. The treatment factor was the formulation of composite flour (F). The treatment factor consisted of 9 levels so that 9 treatments were obtained. Each treatment was repeated 3 times. Composite flour made of kidney bean and soybean flour were tested to study their physical and chemical characteristics. Physical characteristics consists of swelling power and solubility (Senanayake et al., 2013), colors including lightness, redness and yellowness (Syafutri et al., 2021), and white degrees (Mawarni & Widjanarko, 2015). Chemical characteristics consists of moisture content, ash, protein, fat, and carbohydrate content (AOAC, 2005). The data obtained were evaluated using analysis of variance (ANOVA) and honestly significant difference test at the 5% level.

Process of Making Kidney Bean Flour
The process of making kidney bean flour referred to Pangastuti et al. (2013). Kidney beans were soaked (24 hours) in water (1:5). Kidney beans were boiled for 90 minutes, then kidney beans were dried using an oven (55±2 o C) for 18 hours. Dry kidney beans were mashed using a blender, then sieved (80 mesh) to produce kidney bean flour.

Process of Making Soybean Flour
The process of making soybean flour referred to Syaiful et al. (2022). Soybeans were soaked (24 hours) in water (1:5). Soybeans were boiled for 30 minutes, then they were drained for 15 minutes andtheir skin was peeled. Soybeans were dried using an oven (55±2 o C) for 17 hours. Dry soybeans were mashed using a blender, then sieved (80 mesh) to produce soybean flour.

Process of Making Composite Flour
The process of making composite flour referred to Syaiful et al. (2022). Kidney bean flour and soybean flour were weighed (according to treatment; the total weight of flour was 100 g), then they were homogenized using a blender. The mixed flour was sieved (80 mesh) to produce composite flour.

Swelling Power and Solubility
Swelling power and solubility are functional properties of starch which are related to the 122 quality of food products produced. According to Syafutri et al. (2018)  Amylose content of starch is highly correlated with swelling power (Hidayati, 2013). High amylose content will cause a decreasing of swelling power because amylose can block the development of starch. Amylose content of soybean flour was higher than kidney bean flour.
Amylose content of kidney bean flour ranged from 14.93 to 15.00% (Wani et al., 2019), while amylose content of soybean flour ranged from 19 to 22% (Stevenson et al., 2006). The results showed that the increasing of percentage of soybean flour caused the increasing of solubility. Based on preliminary research, the solubility of soybean flour (15.30%) was higher than the solubility of kidney bean flour (11.93%). It was due to the amylose content of each flour.
The amylose content of soybean (19 to 22%) is higher than kidney bean (
The results showed that the composite flour made of kidney bean flour and soybean flour had lightness, redness and yellowness values ranged from 79.00 to 88.60, 7.40 to 9.27, and 9.63 to 19.30, respectively (Figure 3). The analysis of variance showed that the formulation of composite flour had significant effects on lightness, redness and yellowness of composite flour made of kidney bean flour and soybean flour. The results also showed that the redness value of composite flour F1 was higher than other treatments because the proportion of kidney bean flour on composite flour F1 was the highest among other treatments. The composite flour F9 had high yellowness value because the proportion 125 of soybean flour on composite flour F9 was the highest. It was caused by the content of natural pigmen of kidney beans and soybeans. Kidney beans contain anthocyanins and proanthocyanidins (Pangastuti et al., 2013;Han et al., 2015;Wiranata et al., 2017), while soybeans contain carotenoid (Kang et al., 2012;Qin et al., 2017). Anthocyanins and proanthocyanidins are natural bioactive compounds which contributed as red pigmen color, while carotenoid is yellow-orange pigmen color. Both of pigmen colors also has a function as antioxidant. Redness value of composite flour decreased significantly in the treatment F3 (70% of kidney bean flour : 30% of soybean flour), while yellowness value increased significantly in the treatment F2 (80% of kidney bean flour : 20% of soybean flour).

White Degree
White degree is one of the important physical parameters for identifying the color of flour (Pangastuti et al., 2013). was the highest among others. The results of color analysis also showed that lightness value of composite flour F5 was the highest. It stated that the treatment F5 had brighter colors. Figure 4 also showed that white degree values of composite flour with high proportion of soybean flour were higher than composite flour with high proportion of kidney bean flour.

Chemical Characteristics
Analysis of chemical characteristics included moisture content, ash, protein, fat, and carbohydrate content (Table 1). Moisture content of composite flour made of kidney bean flour and soybean flour ranged from 6.48 to 7.94%. The moisture contents of composite flour were in accordance with the SNI 01-3728-1995 or standard for beans flour products (maximal 10%). Table   1 showed that ash content of composite flour ranged from 3.24 to 3.76%. Ash contents of composite flour made of kidney bean flour and soybean flour were higher than standard value of ash for flour products. Kidney bean and soybean were source of mineral. Direktorat Gizi Masyarakat (2018)

Conclusions
Formulation of composite flour had significant effects on swelling power, solubility, color (lightness, redness, yellowness), white degree, moisture content, protein, fat, and carbohydrate, but had no significant effect on ash. Composite flour with higher percentage of kidney bean flour had higher carbohydrate level, while composite flour with higher percentage of soybean flour had higher protein and fat content. The moisture contents of composite flour made of kidney bean and soybean were in accordance with the SNI 01-3728-1995 for beans flour products.