Identification and characterization of potent odorants in selected beet root (Beta vulgaris) products

Beet root;beet colorant;gas chromatography-olfactometry;aroma extract dilution analysis;static headspace

Richardson, Bethany ; Cadwallader ; Keith R.

关键词: Beet root;    beet colorant;    gas chromatography-olfactometry;    aroma extract dilution analysis;    static headspace;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/45435/Bethany_Richardson.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The beet, in its various forms, has been an important agricultural commodity for millennia; it was first mentioned in writing in 8th century BC Mesopotamia.Although the sugar beet contributes to a quarter of sugar production worldwide, the red beet root is an equally, if not more, important product.Not only is the beet root consumed in a culinary setting, it is highly valued for its betalain pigments, which provide a natural source of colorant for food and pharmaceutical use.Despite the beet’s impact on our food supply, the majority of the flavor research on beets concentrates on contaminating aromas in beet sugar.A small number of studies have been performed on beet roots themselves; however, the focus is solely placed on the volatile compounds, which may or may not be aroma-active or impactful to the overall product.In order to fill these gaps in our understanding, a complete aroma analysis of the beet root was performed in the present study.Potent odorants were characterized by the use of aroma extract dilution analysis (AEDA) coupled with gas chromatography-olfactometry (GCO), as well as supported analytically by the use of gas chromatography-mass spectrometry (GC-MS). Initial analyses were performed on four different types of beets: boiled, oven-roasted, canned, and colorant.Extraction of the aroma-active components was accomplished by direct solvent extraction (DSE) with ether as solvent, paired with solvent-assisted flavor evaporation (SAFE).Extracts were fractionated into acidic and neutral-basic components to improve accuracy of identification.During screening analyses using the four different beet preparations, twenty-one different compounds were detected, one of which was unidentified.Canned beets served as the primary focus in each subsequent analysis because they provided the most odor-active and consistent samples. Forty-one aroma compounds were identified and characterized by the use of AEDA, with some of the most important being 2-acetyl-1-pyrroline, geosmin, methional, furaneol, p-vinylguaiacol, and vanillin due to their very high odor potency. Three 3-alkyl-2-methoxypyrazines (isopropyl, sec-butyl, and isobutyl), as well as 1-octen-3-one, phenylacetic acid, and eugenol, were also identified at moderate odor potencies.To detect compounds that might have otherwise been lost during extraction or co-eluted with ether during GCO, a static headspace technique for odor analysis was used.Decreasing volumes of headspace from gently heated canned beet mixtures were analyzed using GCO.Some compounds detected, such as geosmin and methional, were found in previous odor analyses.However, two potent compounds that were previously undetected, including methanethiol and dimethyl sulfide, which was a particularly potent odorant.This technique enabled the discovery of previously undetected compounds, which may be important for subsequent creation of a beet odor model system.However, knowledge of the specific compounds in the beets does not provide complete information for the understanding of the beet’s odor profile.Therefore, it was necessary to perform quantification of compounds both in the solvent extract and headspace of the canned beets, using the technique stable isotope dilution analysis (SIDA).In the headspace, methanethiol and dimethyl sulfide were targeted for quantification using headspace solid-phase microextraction (HS-SPME).Twenty-four individual aroma-active compounds were selected for analysis by DSE-SAFE.After using SIDA to determine the concentration for each individual compound, odor activity values (OAVs) were determined.OAVs were calculated by dividing the concentration of a compound by its odor threshold. An OAV provides an estimate of a compound’s odor potency and its potential importance to the overall aroma of the product.Of the 26 aroma compounds analyzed in the headspace and solvent extracts, dimethyl sulfide, geosmin, E-4,5-epoxy-[E]-2-decenal, methanethiol, p-vinylguaiacol, and β-damascenone possessed the highest OAVs and, therefore, contributed the most to the overall aroma profile of the canned beets.Meanwhile, octanal, Z-1,5-octadien-3-one, nonanal, acetic acid, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-sec-butyl-3-methoxypyrazine, E, Z-2,6-nonadienal, and vanillin were ofmoderate odor potency.