Development of a Stable Isotope Dilution Assay for the Quantification of 5-Methyl-(E)-2-hepten-4-one:  Application to Hazelnut Oils and Hazelnuts

Abstract

A stable isotope dilution assay was developed for the quantitation of the hazelnut odorant 5-methyl-(E)-2-hepten-4-one by mass chromatography using synthesized [(2)H](2)-5-methyl-(E)-2-hepten-4-one as the internal standard. Application of the method on two batches of commercial hazelnut oils, processed from either roasted or unroasted nuts, revealed 6.4 microg 5-methyl-(E)-2-hepten-4-one per kg of unroasted oil whereas 315.8 microg per kg was determined in the roasted nut oil. The about 50-fold higher amount of 5-methyl-(E)-2-hepten-4-one in roasted hazelnut oil suggested the necessity of a thermal treatment to generate the flavor compound. Pan frying of raw hazelnuts (9 to 15 min) or boiling of the crushed nut material for 1 h in water led to an increase of 5-methyl-(E)-2-hepten-4-one by factors of 600 and 800, respectively, thereby corroborating that the major part of the nut flavorant is formed during heat treatment from a yet unknown precursor in hazelnuts.

Filbertone as a marker for the assessment of hazelnut spread quality

“…Table 1 shows that filbertone content varied greatly from paste to paste ranging from 304 µg/kg to 584 µg/kg, with a mean of 430 µg/kg and standard deviation ± 105 µg/kg. The results are in a good agreement with the contents of filbertone in hazelnut oils and roasted hazelnuts stated in the literature (Pfnuer et al 1999;Belitz et al 2009) where a high variability with the variety, roasting time, temperature, and storage conditions is mentioned. Moreover, in the case of hazelnut pastes, the undeclared addition of vegetable oils or other extenders can also decrease the filbertone content.…”

“…Hazelnut aroma depends on the cultivar, ripeness, climatic conditions, and roasting conditions. The impact compounds are produced by both biochemical and thermal pathways (Pfnuer et al 1999). More than 70 compounds were detected in roasted hazelnuts, including the most abundant pyrazines (2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine), carbonyl compounds (hexanal, 3-methylbutanal, 3-penten-2-one, 5-methyl-2-hepten-4-one), and furans (2-methyl-3-furanthiol, 2,3,5-trimethylfuran).…”

“…More than 70 compounds were detected in roasted hazelnuts, including the most abundant pyrazines (2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine), carbonyl compounds (hexanal, 3-methylbutanal, 3-penten-2-one, 5-methyl-2-hepten-4-one), and furans (2-methyl-3-furanthiol, 2,3,5-trimethylfuran). Among others, filbertone, (e)-5-methyl-hept-2-en-4-one, has been reported as the primary odorant (nutty roasty, hazelnut like aroma) of roasted hazelnuts (Pfnuer et al 1999;Alasalvar et al 2003).…”

Chemical Characterization of Virgin Almond and Hazelnut Oils and Their By‐Products

“…Table ,b highlights the broad concentration ranges of the volatiles from the different families present in the commercial almond and hazelnut oils, as exemplified by the acids (1.47–21.81 mg kg –1 almonds and 1.44–18.14 mg kg –1 hazelnuts), aldehydes (3.06–7.11 mg kg –1 almonds and 1.86–14.47 mg kg –1 hazelnuts), and alcohols (0.17–4.16 mg kg –1 almonds and 0.00–2.43 mg kg –1 hazelnuts). The high concentration of acids (18.14 mg kg –1 ), as well as the presence of filbertone (5‐methyl‐( E )‐2‐hepten‐4‐one), pyrazines, and furans (data not shown), is probably related to the extraction conditions employed in the commercial oils (mainly high temperatures) and the use of roasted nuts, which contributes to the typical nutty–roasty aroma …”

Comparison of Natural and Roasted Turkish Tombul Hazelnut (Corylus avellana L.) Volatiles and Flavor by DHA/GC/MS and Descriptive Sensory Analysis

“…It contributed 1.75% (208 ( 29 ng/g) and 4.8% (3481 ( 127 ng/g) to the total volatiles present in natural and roasted hazelnuts, respectively. This compound has been reported to exert a significant odor impression even at very low concentrations (15,22). Filbertone concentration has been shown to increase 472-fold after 9 min roasting of hazelnuts (15); however, Silberzahn (14) reported only an 80% increase after roasting.…”