欧姆加热对豆浆风味物质的影响

为研究欧姆加热对豆浆挥发性物质的影响,采用顶空固相微萃取结合气相色谱-质谱联用技术,对豆浆的风味物质进行分析,利用内标法对各风味物质成分定量分析。通过对比50/30μm二乙基苯/碳分子筛/聚二甲基硅氧烷(divinylbenzene/carboxen/polydimethylsiloxane,DVB/CAR/PDMS)、100μm PDMS、65μm PDMS/DVB 3种萃取头对豆浆风味物质的萃取效果,筛选出最佳的萃取头,并在最适条件下分析豆浆的风味物质成分,为排除热效应对实验结果的影响,2种热处理历程尽可能保持一致。结果表明:65μm PDMS/DVB纤维萃取头较100μm PDMS和50/30μm DVB/CAR/PDMS纤维萃取头更适宜豆浆风味物质的测定;从豆浆样品中共检测到35种挥发性物质,其中醛类物质16种,醇类物质5种,酮类物质3种,酯类物质1种,杂环烃类物质10种,主要包括己醛、(E)-2-庚烯醛、1-辛烯-3-醇等,这些物质共同组成豆浆的特征香气;不同加热处理对豆浆风味物质种类的影响不大,但是对特征香气含量有显著影响(P0.05);欧姆加热处理组样品中己醛、1-辛烯-3-醇、(E)-2-辛烯醛的含量分别比传统加热处理组约低45.55%、58.60%、25.56%,且在欧姆加热处理样品组中未检测到(E)-2-己烯醛和正己醇,而这些物质是豆腥味的主要组成成分。因此,利用欧姆加热方式加热豆浆可以显著降低豆浆的豆腥味。本研究可以为欧姆加热技术在豆浆加工业中的应用提供理论依据。

Effects of Ohmic Heating on the Volatile Compounds of Soymilk

This study aimed to investigate the effect of Ohmic heating on the volatile compounds of soymilk. Headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was employed to analyze the volatile compounds of samples. The extraction efficiencies of three types of SPME fibers (100 μm PDMS, 65 μm PDMS/DVB and 50/30 μm DVB/CAR/PDMS) were compared. The optimal conditions were determined for the analysis of volatiles in soymilk samples. To eliminate the influence of thermal effects, the Ohmic heating and the traditional heating process were kept as consistent as possible. The results showed that 65 μm PDMS/DVB fiber had a greater sensitivity to a more diverse range of volatile compounds in soymilk, followed by 50/30 μm DVB/CAR/PDMS and 100 μm PDMS fiber. A total of 35 volatile compounds were identified in soymilk, including 16 aldehydes, 5 alcohols, 10 heterocycles (hexanal, (E)-2-heptenal and 1-octene-3-alcohol), 3 ketones and 1 ester. These volatiles contributed to the characteristic flavor of soymilk. Different heating methods had no considerable effect on the types of volatile compounds but significantly affects the contents of the characteristic aroma compounds (P < 0.05). In comparison with the conventional heating group, the contents of hexanal, 1-octen-3-ol and (E)-2-octenal were decreased by 45.55%, 58.60%, and 25.56%, respectively, in the Ohmic heating group. (E)-2-heptenal and 1-hexanol, the major odor compounds of soymilk, were not detected in the Ohmic heating group. Thus, it was concluded that the contents of beany flavor compounds in soymilk could be reduced significantly by Ohmic heating. This research can provide a theoretical basis for the application of Ohmic heating in soymilk processing.