Pungent taste, as is commonly known in hot peppers, chilis, ginger and other hot spices, has a heating effect. Things sour or acid in taste like citrus or products of fermentation like wine, yogurt or pickles, are heating. Fermentation creates combustion, which releases heat. Salt is also heating, which we can experience by the burning sensation it produces on cuts or sores.
Sweet taste is cooling, as sugar counteracts burning sensations in the body. Bitter and cold are often synonymous, as in bitter herbs like gentian and golden seal, which reduce fever and inflammation. Astringent taste has a constricting effect, which is the action of something cold like ice, as in such astringent substances like alum, oak bark or witch hazel.
Heating herbs cause dizziness, thirst, fatigue, sweating, burning sensations and they speed the power of digestion. They increase Pitta, but generally decrease Vata and Kapha.
Cooling herbs are refreshing, enlivening, and promote tissue firmness. They are calming and clearing to Pitta and to the blood, but generally increase Vata and Kapha.
“Heating or cooling energy” means that these substances contain, respectively, the energies of fire or water (agni or soma).
Through their energy the six tastes fall into two groups: 1) pungent, sour and salty cause heat and increase Pitta; and 2) sweet, astringent and bitter cause cold and decrease Pitta. Energy, virya, tells us the effect of an herb on Pitta dosha.
Pungent is the most heating taste, followed by sour and then salty. Bitter is the most cooling, followed by astringent and then sweet.