In winegrapes, 3-isobutyl-2-hydroxypyrazine (IBHP) is a likely biosynthetic precursor and degradation product of the herbaceous smelling 3-isobutyl-2-methoxypyrazine (IBMP). However, the relation of IBHP and IBMP in maturing and ripening grapes is poorly understood.  IBHP was extracted by mixed mode cation exchange SPE in the presence of a deuterated standard and silylated prior to GC-TOF-MS analysis, resulting in a detection limit of 20 ng/L for a 100 mL juice sample. The method was then used to quantify IBHP and IBMP uring the growing season at multiple sites. IBHP was detectable soon after fruit set, reached a maximum of >800 ng/L in some samples, and started to decline 2 weeks after veraison. Across sites, maximum IBHP and IBMP were correlated, indicating that IBMP accumulation with Bordeaux cultivars may be dependent on IBHP accumulation.

Behavior of a putative 3-isobutyl-2-methoxypyrazine (IBMP) precursor during grape maturation and ripening

244th National Meeting (2012)

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