HAZELNUT KERNEL QUALITY AS AFFECTED BY ROASTING TEMPERATURES AND DURATION

In our efforts to understand the stability and quality aspects during the roasting process of hazelnuts, we have characterized the effects of roasting time and temperature on roast flavors, off-flavors, and other factors related to 'Barcelona' kernel quality, including changes during storage. Since there is continuing concern about oxidative stability of roasted nut oils and potential for rancidity, this study also presents data on roasting temperature effects on peroxide development and vitamin E losses in extracted oils due to roasting.

Barcelona hazelnuts dried to 6% kernel moisture and stored for one month were roasted at temperatures ranging from 95°C (200°F) to 175°C (350°F), in 14°C (25°F) increments, and roasting times were 10, 20, 30, or 40 minutes at each temperature. For the quality aspects of aroma and flavor we used an untrained panel of 30 faculty and graduate students in our department. Panelists were asked to initially smell rancid hazelnut oil and then samples presented to them, rate roast aroma intensity and any rancid aromas and then to taste the samples and rate roast flavor intensity and any rancid flavors. Other evaluations included observations on pellicle removal or blanching, kernel color, texture, and analysis of peroxide value and vitamin E levels 3 days after roasting and again after two months.

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