Effect of roasting on colour and volatile composition of pistachios (Pistacia vera L.)


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Pistachios have been roasted following the Iranian traditional method (soaking in salty water, drying and roasting at 135 °C). Three Iranian pistachio cultivars (Ahmad Aghaei, Akbari and Kaleghouchi) were compared for their volatile compositions, colour and odour intensity. Lightness decreased in the course of roasting, which resulted from Maillard reaction. Raw pistachios had lower concentrations of most volatiles than roasted. A total of twenty-six compounds were detected in roasted pistachios; these included aldehydes, terpenes, alcohols and only two pyrazines and one furan. These mixtures of volatiles implied that the Iranian roasting system is very soft, and samples retained most of the vegetable notes from fresh pistachios and some roasted notes were generated as well (from 2-ethyl-5-methylpyrazine and 2,6-dimethyl-3-ethylpyrazine). Sample from cultivar Akbari presented higher odour intensity than those by the other two cultivars, due mainly to higher concentrations of pyrazines developed during the roasting step.