isobutyl-methoxypyrazine, more properly, 2-isobutyl-3-methoxypyrazine, or IBMP, smells of green or bell peppers and grass and is found in all green matter. The perception threshold in red and white wines is 615 ng/l and the concentration is higher in unripe grapes and in fruit with low sun exposure because it is very sensitive to UV light. This is why it is more often found in late-ripening varieties such as Cabernets Sauvignon and Franc and Carmenère. IBMP is very common in Sauvignon Blanc, where it is not generally considered a fault.
