Characteristics of Soto , an ethnic food that reflects Indonesian diversity: Based on ingredients

Indonesia is highly diverse in culture, ethnicity, religion, and natural resources. The diversity is also obvious in its cuisine. Soto is an example of an iconic Indonesian dish found in many parts of the country. Despite sharing a similar name, the recipes vary according to their place of origin. Until now, how many variants of Soto are in Indonesia is not exactly known. This review aimed to discuss the characteristics of Soto based on ingredients. Soto is a soup composed of spices-flavored broth and various solid ingredients, such as vegetables and protein-and carbohydrate-rich foods. Every region in Indonesia has a different recipe of Soto ; some use non-turmeric soup or coconut milk soup. The carbohydrate ingredients are mainly soun (cellophane noodle) and potato. The protein ingredients are mainly composed of chicken, egg, and beef. Vegetables consist of bean sprouts, tomatoes, and cabbage. Fried garlic, shallot, spring onion, and crackers are added as a garnish. The diversity of the ingredient makes the distinction among Soto : diversity of locality and diversity of ingredients. Approximately 46 types of Soto are reviewed in this article. Most of the Soto recipes use chicken, bean sprouts, soun, boiled egg, garlic, white pepper, red onion, ginger, and bay leaf as the main ingredients. Soto becomes an identity of its geographical origins and has distinction based on the main recipes.

dishes have sweet tastes, for example, a typical warm dish made from the main ingredients of young jackfruit (Gudeg) added with palm sugar (6). Some ethnic groups in the central region of Indonesia, especially those on the coast, such as Makassar and Bugis, have unique dishes made from sea fish, which are added with tamarind. The public believes that the sour taste of food neutralizes the fishy aroma. Meanwhile, the people of Lombok prefer spicier food (7). The spicy taste will add to the enjoyment of cooking and increase appetite. This proves that Indonesian cuisine is rich in variety and taste (8).
In cultural studies, food or cuisine is understood as part of a cultural system. The ingredients used and the taste enjoyed will be determined socially and culturally. This allows for variations in cuisine that depend on a specific culture as the background. Cuisine with its various recipes is a marker of the identity of an ethnicity (9). Every Indonesian region has a culinary wealth that is characteristic or an identity of that region. Local specialties have been around for a long time and still survive, so they are highly valued as cultural heritage (10). The recipe has also been passed down from generation to generation; even the old ways of cooking are still preserved. Despite modifications or variations, the main ingredients and cooking procedures have not changed. For being part of an area, traditional foods are very easy to find (11).
Five types of cuisine represent Indonesia, namely, Soto, rendang, satay, fried rice, and gado-gado (12). Among these five types, Soto most represents the diversity of Indonesia because almost every region has different variants of Soto (13). The choice of using certain protein sources, condiments, and spices might also reflect the preference of local people for cooking materials. Not to mention the highly diverse cooking process each Soto variant requires, the relatively simple cooking process also makes this cuisine available throughout the country. Soto is not distinguishable from other soup food. Soto is defined as broth added with spices, supplements, and filling.
Soto, also known as sroto or tauto, is a broth-based dish filled with ingredients rich in carbohydrates and proteins, vegetables, garnish, and other additives. Going back to the history of how Soto was developed and became a popular dish in Indonesia, Soto has been known since the nineteenth century. During the Dutch colonization (1816-1942), Indonesian people experienced an economic downturn. Immigrants such as the Chinese also became marginalized (14). The term Soto also originated from caudo of China. "Cau" means grass, which refers to spices as seasonings, and "do" means innards (14,15). Preparing the food was very difficult because people did not have much income, or raw materials are difficult to obtain. People who eat low-nutritious foods are only able to eat beef and poultry innards. At that time, Soto was popular. Soto is prepared from leftover protein sources such as beef innards mixed with spices-containing soup (16). In one large pot, Soto can be eaten together by many people. Soto, prepared with cheap ingredients, can meet the food needs of the family.
Almost every Indonesian region has its version of Soto with different and quite often unique ingredients. The rich collection of spices also contributes to the highly diverse Soto repertoire of the country (13). This review has studied 46 soup varieties from many regions in Indonesia. The study aimed to characterize each type of Soto based on its ingredients.

General Characteristics
Soto is a soup that mainly consists of solid and liquid ingredients. Soto is usually served warm with a distinctive broth flavor (17). Currently, Soto has various variations, names, and recipes. Diversity has also been influenced by the food culture where Soto comes from. In Indonesia, 75 types of Soto are available, spreading in Java-Madura, Sumatera, Kalimantan, Sulawesi, Bali, and Nusa Tenggara (13). However, only 46 types of Soto are evaluated in this paper. This is related to the information obtained and the easiness of getting this type of soup in Indonesia. Every region has its characteristic Soto because of the differences in the availability of raw materials and eating habits. Indonesia has varied ways of cooking and eating habits. The spices used are also very diverse; each region has a special spice that marks the identity of that region (18). Differences include variations in the solid and liquid ingredients ( Figure 1). The solid ingredients consist of carbohydrates, protein, vegetables, and garnish. The liquid ingredients consist of broth, herbs, and spices. Thus, each type of Soto must contain these ingredients. Every Soto is unique based on its recipe, and its ingredients include chicken meat, bean sprouts, noodles, tomatoes, soy soup, chicken eggs, cayenne, chili soup, beef, cabbage, potato fritters, red chili, and crackers.
In Indonesia, the abundance of spices offers various choices of typical Indonesian food and drinks (19). Taste is the greatest strength of Indonesian cuisine because Indonesian people like cuisine with a complex taste (19)(20)(21). A plate of food can have various flavors (sweet, salty, sour, spicy, and others) and textures (soft, hard, creamy, crunchy, and others). This cuisine is relatively healthier for using materials with fewer artificial preservatives or long processes. Traditional cooking techniques can allow the absorption of herbs perfectly into ingredients (22).

General Traditional Methods of Cooking Soto
Each variant of Soto has general and common techniques, i.e., making the broth, sautéing the seasoning (liquid ingredients) into the broth, and then filling in the solid ingredients (23).

Broth Extraction
In making the delicious chicken stock, free-range chickens, or "ayam kampung," are generally used, especially the back and claw parts. The chicken is cooked over low heat for a long time to extract optimal broth. Apart from chicken, broth can also be extracted from beef. Beef broth is obtained from boiling beef or bone. To get the maximum taste, beef bones can be added to the broth stew ( Figure 2a).

Spice Refinement
Soto seasoning must be mashed first so that the meat can be soaked easily into it and blended optimally with the broth. However, not all spices must be smoothed, for example, aromatic spices such as bay leaves, orange leaves, and lemongrass and dried herbs such as cloves and nutmeg. Spices are usually left whole and cooked with broth (Figures 2b and 2c).

Spice Sautéing
The seasoning is usually sautéed to reduce the unpleasant scent of raw seasoning. Blended seasonings can be sautéed together with aromatic herbs such as bay leaves ( Figure  2d).

Addition of Ingredients
Carbohydrates and proteins are the main ingredients of Soto. The combination of these ingredients makes Soto a one-dish meal, i.e., a meal served in one dish, already containing carbohydrates, proteins, fats, vitamins, and minerals. These foods can be served for breakfast, lunch, and dinner ( Figure 2e).

Serving
Soto is generally served in a bowl, added with a garnish on top, and served hot (22). Generally, Soto is served when it will be eaten ( Figure 2f). Most Soto is served with rice or rice cake, which are served separately or mixed directly into the soup such as in Soto Kudus. In addition to rice, Soto can be mixed with noodles, like Soto Mie Bogor. Makassar Coto is served with rice cake (24).

Variations of Soto
In addition to naming the majority of Soto types using the name of the region of origin, differences can be observed in the types of sauce, contents, seasonings, and complements. Soto sauce is divided into clear, yellow (turmeric), and coconut milk soup.
Soto variants are spread throughout Indonesia. This paper focused on 46 types of Soto, namely, 8 Soto in Sumatra, 33 in Java, 2 in Kalimantan, 1 in Sulawesi, and 2 in Bali ( Figure 3; the numbering is intended for the ease of writing, which has nothing to do with any ranking). Carbohydrate sources often found in Soto include tubers such as potatoes and cassava. Potatoes are fried, steamed, or mashed. The Indonesian fried mashed potatoes, or perkedel, are flavored mashed potatoes formed into flat rounds and fried. Perkedel (in Indonesian) or potato patties are a source of carbohydrates and very complementary to Soto dish besides rice and noodles. Processed cereals such as glass noodles, vermicelli, noodles, and macaroni are also used as sources of carbohydrates. Noodles, which are generally a source of carbohydrates, are also found in Soto Mie Bogor. As shown in Table 1, the most dominant sources of carbohydrates are glass noodles/vermicelli (44.9%), potatoes (18.4%), and mashed potatoes (16.3%), whereas noodles, cassava, and macaroni are found only in certain types of Soto.

Proteins
Protein sources of Soto are influenced by the culture and farming commodity of the regions. For example, Palembang is well known for its Pempek (fish cake). Fish, as the main protein source, is reflected in their food culture. Soto protein sources consist of chicken, beef, egg, offal, fish, and seafood. As shown in Table 1, chicken is a popular source of protein widely used in Soto (55.1%) and every dish. The average consumptions of chicken eggs and chicken meat in Indonesia are 2.119 and 0.124 kg per capita/week, respectively. This amount is greater than that of beef consumption, with 0.009 kg per capita/week (25). Therefore, chicken is more widely used than beef (26). Most types of Soto with chicken as the main ingredient are found in Java; approximately 60% of Soto in Java uses chicken meat as the main ingredient, whereas only approximately 14% in Sumatra used chicken meat. Soto types using chicken meat as the main ingredient are Soto Lamongan, Soto Tasikmalaya Apart from chicken, eggs (32.7%) and beef (30.6%) are often added as protein sources (Table 1). Generally, chicken eggs or quail eggs are used. Eggs are usually served as sliced boiled chicken eggs or quail satay eggs.
Fish meatballs are the main protein source in Soto Palembang, besides mushrooms and sedap malam flowers (Polianthes tuberosa). Palembang is very well known for its distinctive fish-processing characteristics such as Pempek Palembang (a savory fishcake delicacy) and Palembang crackers, which used fish as raw materials. Thus, its Soto possibly uses fish as an ingredient. Fish is rarely used as a protein source; however, the natural potential that supports it and consumer preferences resulted in the addition of fish in Soto. Likewise, the typical Soto Tenggiri Jambi adds mackerel as a protein ingredient.  3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45  Soto Kasaran (Kebumen, an area in Central Java) uses duck meat, which is rarely found in another Soto. At Kebumen, many people are engaged in duck farming. Generally, consumers prefer chicken meat to duck meat because of the higher fat content, fishy smell and odor, reddish flesh color, and rough and tough texture; however, they are more expensive, so Soto with duck-based ingredients is rarely found (26).

Vegetable
Vegetables used most commonly are bean sprouts, tomatoes, and cabbage (51%, 34.7%, and 22.4%, respectively, Table 1). Bean sprouts or sprouts are one of the popular vegetables consumed by the Indonesian people, both middle and upper classes because bean sprouts are easy to grow anywhere. Bean sprouts grow from germinated green bean seeds. Bean sprouts are widely used for consumption as vegetables, eaten raw, or mixed with gadogado, meatballs, fried tofu, bakwan, Soto, or other foods. Bean sprouts made from green beans and soybeans, Mung bean (Vigna radiata L.), are one of the plant commodities. Indonesian people also consumed legumes (27). Tomatoes contain lycopene as an antioxidant, and tomatoes are often added to every dish because they give a savory taste in the presence of glutamic acid (28), improving the taste. Fruits and vegetables are excellent sources of antioxidants, which contain vitamins E and C and various carotenoids such as betacarotene and lycopene (29).
Some Soto types have specific ingredients. These types are based on the natural resources in each region, such as radish (13). Radish is used as a flavor remedy for other foods, especially animal foods with high fat (30); thus, beef and offal can be neutralized. Soto Bandung uses radish as an additional ingredient because radish is abundant in Bandung (31). This clear Soto becomes even more delicious when sprinkled with fried soybeans as a topping. Apart from Soto Bandung, radishes are also used in Soto Babat Bali.

Garnish
The term garnish comes from the French word "garnir," which means to decorate or furnish. In the culinary world, garnishes make food an attractive decoration. In Soto, common garnishes include fried garlic (91.8 %), shallot (87.8%), spring onion (63.3%), and celery (59.2%) ( Table 1). Indonesian dishes often add shallot to each meal, whether it is soupy or not, but in soupy foods, spring onion and celery are often used as garnishes. Shallot and fried garlic are very often used in Indonesia; red onion gives a distinctive savory taste to every dish. Garlic also provides a strong taste (32).
Soto types are distinguished based on the additional ingredient. Kerupuk is an Indonesian deep-fried cracker made from starch and other ingredients, which serves as flavoring (33,34). Crackers give a crisp texture to each dish. Other additional ingredients are roll, tofu, and fried tempe, which only exist in certain soups. Soto Mie Bogor is generally added with risol, a pastry containing meat/vegetables, whereas Soto Mie Bogor risoles contains soun or vermicelli, which makes this Soto unique (35).

Liquid Ingredients
The characteristics of Soto soup are influenced by the broth and spice components used. Regarding color, Soto is divided into clear, yellow, white, and red. A clear soup generally does not use turmeric, like that in yellow gravy. A white sauce is generally added with concentrated coconut milk. A red sauce is usually added with chili sauce.

Broth
Bone broth, which is considered one of the most ancient and extraordinary nutrients, is made from boiled animal bones. Bone broth greatly contains amino acids, collagen, gelatin, and essential minerals, many of which are not obtained easily from other common foods (36). As shown in Table 2, chicken broth is the most widely used in various types of Soto (32.6%). Beef broth (17.4%) is also commonly used in Soto. Other components are salt (97.8%), sugar (91.3%), and vegetable oil (63.0%).
Soto with yellow soup is Soto Lamongan. This Soto has a savory taste and is often added with chicken feet as a protein source. Interestingly, this Soto is usually served with a sprinkle of shrimp cracker powder, often called koya powder. Turmeric is widely used in various Soto in Indonesia (37).
Unlike the yellow soup, the coconut milk soup is used in Soto Jakarta and Soto Betawi, which have similarities owing to the use of milk or coconut milk soup, beef or offal, and chips (melinjo chips). The use of rambak crackers, crackers, bay leaves, koya, coconut milk, fried tempeh, turmeric, and shallots are influenced by Javanese tradition. The use of turmeric in soup is influenced by Indian cuisine. Indians use turmeric in their curry dishes. Curry is used in Soto Sulung, Soto Betawi, and Soto Madura. Meanwhile, ingredients and spices such as tomatoes, celery, cabbage, and processed cakes are Western influences.

Herbs and Spices
Spices are the key to the richness of Soto's taste. Some Soto types are recognized by their specific aroma and flavor of the spices. Spices are natural food additives that contribute to the taste of foods. Spices possess medicinal and nutritional properties (38). Coto Makassar is known for its 40 ingredients called "Patang Pulo," which means that this soup contains huge amounts of seasoning. Coto Makassar is one of the oldest Makassar culinary foods in Indonesia. Coto Makassar is a traditional heritage that has become a favorite of the community and can be found in most regions in South Sulawesi (39).  3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29  As shown in Table 2, the main herbs and spices found in Soto include white pepper, lemongrass, ginger-lime leaves, bay leaf, turmeric, candlenut, galangal, coriander, clove, cumin, cinnamon, nutmeg, cardamom, kencur (Kaempferia shipyard), mace flower, curry leaves, and kluwek. Three types of spices, namely, white pepper, lemongrass, and ginger, are always used in every soup dish. As for the specific types of soup ingredients, cardamom is used in Soto Kalimantan and Sumatra. Nutmeg is only used in Soto Sumatra.
Meanwhile, lime is used in Soto Betawi and West Java. Soybean soup, coconut, peanut soup, and taoco sauce are used in Central Java and Yogyakarta. Each culinary area has its unique flavoring ingredients (8).
White pepper provides flavor and aroma to the dish. Consumption of this spice induces a warm feeling. Apart from providing nutrition, this spice can be also used in medicine. Indonesia is the world's second-largest producer of white pepper after Vietnam (40). dish.
Lemongrass gives a fresh taste to the cuisine, and this is often used in Indonesian, Malay, or Thai cuisine (41). The stem leaf section is used. In addition, ginger can be added to the Soto. Ginger is very popularly used as a spice and medicine. It has a slightly spicy taste because it contains zingerone ketone (42). This ginger gives a warm taste to every dish. Usually, it is used by rubbing or pounding it with spices.
Three other types of herbs that are often used are spring onion, candlenut, and turmeric. Celery, lime leaves, galangal, bay leaf, sugar, and coriander are also used in some Soto types. Palm sugar, cumin, coconut milk, and tauco are very rarely used.
A Soto variant in East Java is the most diverse. This Soto uses 5-16 types of spices. While Soto variants in Aceh, Banjarmasin, Lampung, Minahasa, and Jambi used the least number of spices, with only 6-7 spices.
Bay leaf, ginger, and lemongrass are popular herbs and spices used in Soto. However, several Soto variants are prepared without bay leaf (39%), ginger (21.7%), and lemongrass (21.7%). The similarity of Indonesian Soto types was clustered using the unweighted pair group method with arithmetic mean based on 51 characters (Tables 1 and 2).  Clustering analysis also reveals eight Indonesian Soto groups ( Table 3). The result shows the ingredients that can be used to determine similarities and differences in Indonesian Soto types. However, these data should be supported by ethnic, culture, and anthropological aspects to explore each similarity group deeply, which can be a promising research topic about Indonesian Soto.
Soto is one of the dishes that have a high diversity in Indonesia. The cuisine represents the Indonesian nation because of the diversity of types in each region. Soto has no specific definition, and Soto cannot be classified scientifically from other cuisines such as soup. Each Soto name was based on the name of the community it originates. The variety of spices used gives different tastes. Various solid and liquid ingredients are used. Solid ingredients include carbohydrates, proteins, vegetables, garnish, and additional ingredients. Liquid ingredients consist of broth, herbs, and spices. Most Soto recipes use chicken, bean sprouts, soun, boiled egg, garlic, white pepper, red onion, ginger, and bay leaf as the main ingredient.

Author Contributions
LC has written the entire script. A.A.R., N.A., W.D., and H.P. have contributed to analyzing content and writing procedures. K.R. has conducted analysis compilation, outline writing and abstract writing correction, A.S.M. has made dendogram analysis, FH analyzes from an anthropological perspective.

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