A packet marked “light” or “deep” offers an early clue to the tea inside. Behind those words are choices about ingredients and heat. The aroma of hojicha takes shape through those choices, before the tea reaches the cup.
What heat changes in the tea
A study of bōcha roasting describes volatile compounds forming from amino acids and sugars as the tea is heated. Substances already present in the tea become new compounds that contribute to its aroma.
In this process, the aroma develops from the tea’s own components. Changing how heat is applied can change the result, even when the tea itself is the same.
More than a single toasty note
NARO, the National Agriculture and Food Research Organization, created an aroma profile in a trial on green tea finishing processes. It described the aromas of compounds whose influence increased with roasting as sweet, fruity, green, roasty, spicy, earthy, floral and meaty.
The list makes room for floral and fruit-like notes alongside toastiness. NARO also writes that roasting increases characteristic toastiness and fullness while softening grassy notes. The familiar roasted aroma has several parts to it.
NARO notes that roasting strength varies by consuming region, with differences in toastiness. Its account does not describe every aroma compound increasing uniformly. Which components become more influential depends on the conditions; the balance of aromas is distinct from the amount of any one compound.