Acrylamide risk and control in roasted hazelnuts

The hazelnut industry contributes over $400 million to the Turkish economy and is the main source of income, especially for the Ordu and Giresun provinces of Turkey, with a total yield of 545,000 t/year. In addition to Turkey, the main worldwide producer, Italy, the USA, Georgia and Azerbaijan produce the rest of the world production.

Consumption of hazelnuts is generally familiar as raw and roasted whole nut, together with flour to use in processed foods, such as bakery and chocolate products. Studies on acrylamide attract attention of the entire scientific community. The acrylamide is listed as a potential human carcinogen by World Health Organization and it occurs naturally during the roasting process, which is the main and the first step in hazelnut processing that significantly enhances their taste, color and texture. Acrylamide formation in roasted hazelnuts has been studied by Polish, Italian and Czech scientists, however, Turkish hazelnuts which meet 70% of hazelnut production in the world, have not been studied in this regard.

The scientists at Giresun University have evaluated the acrylamide content and color formation (CIE L*, a* and b*) of hazelnuts which processed at different roasting temperatures of 130°C, 150°C, 160 °C and 170°C with roasting time for 15 and 30 min.

Acrylamide contents of roasted hazelnuts were measured by Ultra Performance Liquid Chromatography. Acrylamide formation of roasted hazelnuts was undetectable and stayed under the instrument detection level in all treatments with an exception. The only acrylamide formation was detected in treatment of the highest heat (170°C) and longest time (30 min) with the value of 19±2.5 μg/kg which was just below the instrument’s detection limit of 20 μg/kg.

Hazelnuts roasted at 130°C (a), 150°C (b), 160°C (c) and 170°C (d) for 15 min and 30 min in above and below row, respectively.

Also color formation is one of the significant signs of roasting  hazelnuts. Color analyses were performed using computer-aided image processing technology (CIE L*a*b*). Color L* values which show brightness and the degree of roasting ranged from 55.14 to 76.16. The lowest color L* values were calculated from the treatment that detected acrylamide. The color L* values, therefore, may be used as a quick quality control parameter to estimate the sufficient roasting time and temperature in roasting process of hazelnuts.

"The roasting temperature at 170°C and a time of 30 min may be accepted as threshold values to avoid acrylamide formation in the roasting process of hazelnuts, according to findings of the present study. We have proven that no acrylamide occurs under the roasting conditions (145°C for 15 min) generally applied in commercial nut-roasting facilities. Our results confirmed that dietary acrylamide exposure through roasted hazelnut intake is very low and does not pose a carcinogenic risk. This finding is important for not only for public health, but also for the Turkish and world economy as well," the scientists say.

Source: Yalçın Tepe, Ayşegül Çebi, Handan Aydin, 'Acrylamide content and color formation of hazelnuts roasted at different processing temperatures and times', 2020, European Food Research and Technology.

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