超临界CO_2流体萃取兔肉腥味物质

The Odor of Rabbit Meat Extracted by Supercritical Carbon Dioxide Fluid Extraction

【目的】探讨超临界CO_2流体(SFE-CO_2)萃取兔肉腥味物质的条件,确定腥味物质的种类、组成和含量,为兔肉脱腥以及加工提供理论基础。【方法】采用超临界CO_2流体对兔肉腥味物质进行萃取,以提取率为指标,在单因素试验基础上进行Box-Behnken响应面分析;定量加入内标物质2,4,6-三甲基吡啶(TMP),通过气相色谱质谱仪(GC-MS)对兔肉腥味物质进行分析鉴定。计算气味活度值(OAV),结合气相色谱-嗅闻(GC-O)和感官评价,确定兔肉腥味物质主体成分。【结果】单因素试验结果表明,当萃取温度为40℃时,提取率最高达到97.91%,峰面积为1.58×10~9;当萃取时间为4 h时,提取率最高,为97.83%,峰面积为2.42×10~9;萃取压力为25 MPa时,最高提取率为97.78%,峰面积3.78×108。其中,萃取温度和萃取压力不仅影响溶质扩散系数,还影响CO_2流体密度。温度增加时,尽管扩散系数增大,由于CO_2流体密度下降,提取率随之减小。虽然CO_2流体密度在高压下较大,但随着压力增加,可压缩性随之减小,由于扩散系数降低,溶质溶解度下降,因而提取率降低。当萃取时间过长时,一些非挥发性物质被溶出,使得萃取物质总量增加,降低了挥发性风味物质的比重。根据响应面分析,得出最优萃取条件为:萃取温度40.67℃、萃取压力25.67 MPa、萃取时间3.13 h,提取率为98.01%。而实际操作时,提取条件修正为萃取温度40℃、萃取压力25 MPa、萃取时间3 h,在此条件下提取率为98.11%。通过定量加入内标物质TMP,GC-MS定性定量分析得到兔肉挥发性风味物质5类,包括醛类、酸类、酯类、杂环类化合物和烃类,共计38种风味化合物。其中,酸类((1 394.25±3.45)μg·kg^(-1))>酯类((569.26±1.23)μg·kg^(-1))>烃类((471.82±1.11)μg·kg^(-1))>醛类((168.46±0.97)μg·kg^(-1))>杂环类((86.71±0.64)μg·kg^(-1))。通过计算得到兔肉挥发性风味物质中戊醛、己醛、己酸和2-戊基-呋喃的OAV值均大于1,且己酸>己醛>2-戊基-呋喃>戊醛,表明这4种物质对兔肉腥味有重要贡献,而己酸对兔肉腥味的贡献最大。同时,气相色谱-嗅闻(GC-O)分析认为这4种物质均具有不同程度异味,包括肝脏腥味、草腥味、羊膻味和豆腥味等,感官分析表明萃取物有明显兔肉腥味。【结论】超临界CO_2流体萃取兔肉腥味物质可行,为研究兔肉腥味提供了新的提取方法。其最佳萃取条件为:时间3 h,温度40℃,压力25 MPa。戊醛、己醛、己酸和2-戊基-呋喃初步确定为兔肉腥味的主体成分。

【Objective】The aim of this study was to explore the conditions for extracting the odor of rabbit meat by supercritical carbon dioxide fluid extraction（SFE-CO_2）, to determine the species, components and contents of rabbit meat odor and to provide the database for further deodorization and processing industry. 【Method】 SFE-CO_2 technology was employed to extract the odorants in rabbit meat with Box-Behnken response surface analysis based on single factor experiments, using extraction yield as a target. The odorants of rabbit meat were detected by gas chromatograph in tandem with mass spectrum, with 2, 4, 6-trimethylpyridine（TMP） as an internal standard. Calculating odor active value（OAV） of the detected matters, and combining with gas chromatography olfactory（GC-O） and sensory evaluation, the main contents of rabbit meat odor was determined.【Result】The results of single factor experiment indicated that the extraction yield could reach 97.91% and the peak areas were 1.58×10^9 when the extraction temperature was 40℃. When the extraction time was 4 hours, the extraction yield and peak areas were 97.83% and 2.42×10^9, respectively. The extraction rate reached 97.78% with peak areas of 3.78×10^8 when the extraction pressure was 25 MPa. Among the three factors, the extraction temperature and extraction pressure not only affected the solute diffusion coefficient, but also the density of CO_2 fluid. The diffusion coefficient increased when the extraction temperature was raised, but the extraction yield decreased due to the decreased CO_2 fluid density. Although the density of CO_2 fluid was larger at higher extraction pressure, the compressibility decreased. Hence, the extraction yield decreased due to the reduction of diffusion coefficient and solubility. When the extraction time was too long, the proportion of the odorants was reduced, for some non-volatile compounds were extracted, with the total amount increased. According to the response surface analysis, it was concluded that the optimal extraction temperature, extraction pressure and extraction time were 40.67℃, 25.67 MPa and 3.13 h, respectively, with extraction yield reached 98.01%. And the actual operation showed that the extraction temperature, extraction pressure and extraction time were 40℃, 25 MPa and 3 h, respectively. Under these conditions, the extraction yield was 98.11%. Through quantitatively adding internal standard substance TMP, GC- MS quantitatively analyzed for rabbit meat volatile flavour compounds of five classes, including aldehydes, acids, esters, heterocyclic compounds and hydrocarbons, a total of 38 kinds of flavor compounds. Comparing the five types of matter content： acids（（1 394.25±3.45） μg·kg^-1） esters（（569.26±1.23） μg·kg^-1） hydrocarbon（（471.82±1.11） μg·kg^-1） aldehyde（（168.46±0.97） μg·kg^-1） heterocyclic（（86.71±0.64） μg·kg^-1）. The key odorants of rabbit meat odor were pentanal, hexanal, hexanoic acid and 2-pentyl furan via calculating OAV. Those four materials with liver off-flavor, grass odor, muttony odor and beany odor respectively were regarded as the main bodies of odor in rabbit meat by GC-O. In addition, the extractant showed rabbit meat odor obviously through sensory evaluation.【Conclusion】The method of SFE-CO_2 which provides a new extraction way for researching rabbit meat odor is feasible. The optimal extraction temperature, extraction time and extraction pressure was 40℃, 3 h, 25 MPa. Pentanal, hexanal, hexanoic acid and 2-pentyl furan were preliminarily regarded as the main bodies of rabbit meat odor.