Taste is one of the attributes of food. According to ayurvedic text books and principles of ayurveda, tastes are of six types. We all know there are 5 fundamental elements or panchamahabhutas. Each taste has combination of two fundamental elements. The combination of fundamental elements determines the qualities of respective taste or rasa.

Here is the list of tastes and their combination.
Madhura (sweet) = Prithvi ( earth element) + Ambu (water element)
Amla (Sour) = Agni (Fire Element) + Prithvi ( Earth Element)
Lavana (Salt) = Ambu (Water element) + Agni (Fire Element)
Tikta (Bitter) =Akasha (space element ) + Vayu (air element)
Katu (ungent or spicy) = Agni (Fire element) + Anila (Air element)
Kashaya (Astringent) = Prithvi (earth element) + Anila (air element)

Read article at Ayurveda Rasa