Garcinia binucao is a species of flowering plant in the Clusiaceae family. It is commonly known as binukaw, batwan or batuan, is a species of Garcinia endemic to the Philippines. It is not cultivated, though its edible fruits are harvested from the wild for use as a souring agent in some Filipino dishes.

Batwan, also known as batuan or Garcinia binucao, is a fruit that is commonly used in Filipino cuisine, particularly in the Visayas and Mindanao regions of the Philippines. It belongs to the Garcinia family and is known for its sour taste and unique flavor. Batwan is an essential ingredient in many traditional Filipino dishes, imparting a tangy and citrusy flavor to soups, stews, and sauces.

Here are some examples of how batwan is used in Filipino cuisine:

1. Sinigang:
Sinigang is a popular Filipino sour soup that features a tamarind-based broth. In certain regions, batwan is used as an alternative souring agent in sinigang. The fruit is added to the soup to provide a tangy and acidic taste, balancing the flavors of the meat or seafood and vegetables.

2. Kare-Kare:
Kare-Kare is a traditional Filipino stew made with oxtail, tripe, or vegetables in a rich peanut sauce. Batwan is sometimes added to the dish to enhance the sourness and add a hint of citrusy flavor to the sauce.

3. Pinangat:
Pinangat is a Filipino dish made with fish or shrimp cooked in a sour broth of tomatoes, ginger, onions, and spices. Batwan is often used to provide the souring agent in this dish, resulting in a zesty and flavorful broth.

4. Sinampalukang Manok:
Sinampalukang Manok is a chicken soup dish made with tamarind leaves and other aromatics. In some variations, batwan is used instead of tamarind leaves to achieve the desired sourness.

5. Atchara:
Atchara is a pickled vegetable side dish that accompanies many Filipino meals. It is typically made with grated unripe papaya, carrots, onions, and bell peppers. Batwan is sometimes added to the pickling solution to give the atchara a sour and tangy taste.

In addition to its usage in Filipino cuisine, batwan is similar to other souring agents found in different culinary traditions. Here are some examples:

1. Tamarind:
Tamarind is a tropical fruit widely used as a souring agent in various cuisines around the world. It is commonly used in Indian, Thai, and Mexican cuisine to add a tangy flavor to curries, soups, chutneys, and sauces.

2. Calamansi:
Calamansi is a citrus fruit native to Southeast Asia, particularly the Philippines. It is small and round, similar to a lime, and has a sour taste. Calamansi juice is often used as a condiment or marinade in Filipino cuisine to add a sour and refreshing element to dishes.

3. Kaffir Lime:
Kaffir lime is a citrus fruit widely used in Southeast Asian cuisine, especially in Thai and Indonesian dishes. Its leaves and zest are used to add a tangy and aromatic flavor to curries, soups, and stir-fries.

4. Sumac:
Sumac is a spice commonly used in Middle Eastern and Mediterranean cuisines. It is made from the dried and ground berries of the sumac plant. Sumac has a tangy and slightly fruity flavor, and it is often used as a seasoning or garnish for salads, meats, and dips.

These examples highlight the significance of souring agents in various cuisines worldwide. Batwan, with its distinctive sour taste, adds a unique flavor profile to Filipino dishes, just like tamarind, calamansi, kaffir lime, and sumac do in their respective culinary traditions.

In conclusion, batwan or Garcinia binucao is a sour fruit used in Filipino cuisine, particularly in soups, stews, and sauces. It imparts a tangy and citrusy flavor to dishes, adding a unique taste. Whether it's enhancing the sourness of sinigang, kare-kare, pinangat, sinampalukang manok, or being used in pickled side dishes like atchara, batwan plays a vital role in Filipino culinary traditions. It is similar to other souring agents like tamarind, calamansi, kaffir lime, and sumac, which are used in different cuisines worldwide to provide a tangy and refreshing element to various dishes.