Analysis Of Volatile Compounds In Chinese Traditional Fermented Flour Paste

Fermented flour paste, with unique flavor, is essential for Chinese cooking and seasoning fin with a history of thousands of years in China. The study of analysis of volatile compounds in fermented flour paste had rarely been published in China and abroad. Almost no published report on the volatiles in Chinese traditional fermented flour paste, studied by gas chromatography and olfactometry (GC-O), electronic nose and electronic tongue, had been found. The extraction method of simultaneous distillation and solvent extraction (SDE) and solid phase microextraction (SPME) were used to extract volatiles of two kinds of fermented flour paste, one was made from wheat and called wheat paste, and another was made from steamed bread and called steamed bread paste. The gas chromatography, installed with DB-5 or DB-WAX capillary column, and mass spectrometry (GC-MS) was used to analysis volatiles of quanlity and quantity. GC-O and aroma extract dilution analysis (AEDA) were used to analysis the active aroma components in wheat paste and steamed bread paste. Electronic nose and electronic tongue were used to compare seven kinds of fermented flour paste, wheat paste, steamed bread paste, five kinds of fermented flour paste with different brands, with cooking and not cooking.The paper's findings include the following four aspects:1. Two kinds of fermented flour paste (wheat paste and steamed bread paste), which was used wheat, wheat flour or steamed bread as main raw materials, according to the process of traditional Chinese fermented flour paste, was made by author. Volatiles in two kinds of fermented flour paste were extracted by SDE and SPME. Optimized SDE extracted conditions were 200g paste sample, 50mL ether and extracted 2 hours; Optimized SPME extracted conditions were 25g paste sample, 50/30μm DVB/CAR/PDMS fiber, adsorption temperature 55℃and adsorption time 45min.2. GC-MS, installed with the weak polar DB-5 or strong polar DB-WAX capillary column, was used to analysis volatiles of quanlity and quantity in wheat paste and steamed bread paste. 44 volatiles extracted by SDE and SPME were identified by GC-MS with DB-5 capillary column from wheat paste, and 59 volatiles were identified from steamed bread paste. 131 volatiles extracted by SDE and SPME were identified by GC-MS with DB-WAX capillary column from wheat paste, and 121 volatiles were identified from steamed bread paste. The same volatiles identified from wheat paste and steamed bread paste included, benzaldehyde, benzene acetaldehyde, furfural, 3-methylbutanal, hexadecanoic, 2-methylbutanal, 5-methyl-2-phenyl-2-hexenal, ethyl hexadecanoate, ethyl linoleate, 2-pentylfuran, 2-acetylfuran, 2-furanmethanol, dimethyl trisulfide, 4-ethyl -guaiacol, 2-methocy-4-vinyl phenol, et al.. Among, the concent of furfural in wheat paste and steamed bread paste was higher, and the concent of furfural identified by GC(DB-WAX)-MS was 20.976μg/g in wheat paste and 218.629μg/g in steamed bread paste. Volatiles with higher content in wheat paste, identified by GC(DB-WAX)-MS, also included 2-methylbutanoic 90.500μg/g, tetramethyl pyrazine 26.032μg/g, 2-methyl -propanoic 19.974μg/g and hexadecanoic 12.536μg/g. Volatiles with higher content in steamed bread paste, identified by GC(DB-WAX)-MS, included 5-methyl-2-phenyl-2 -hexenal 28.538μg/g, 4-ethylguaiacol 24.865μg/g, benzene acetaldehyde 21.744μg/g, 3-methyl -butanal 16.414μg/g, ethyl hexadecanoate 11.386μg/g and ethyl linoleate 10.934μg/g, et al..3. GC-O and AEDA were used to analysis the active aroma components in wheat paste and steamed bread paste. Aromas with log2FD≥5 (FD, Flavor Dilution Factor) included acetic, 3-methylbutanal, furfural, methional, 1-octen-3-ol, dimethyl trisulfide, tetramethyl pyrazine, isovaleric acid, 2-acetylfuran and benzene acetaldehyde, et al.. Furfural log2FD=7 and methional log2FD=8 have the higher FD factor in wheat paste.4. The analysis results of electronic nose show that, before cooking the aroma of the Liubiju and Tianyuan fermented flour paste was similar with discrimination index 44.16%; after cooking the aroma of them are obviously different with discrimination index 99.48%. The aroma of wheat paste and the steamed bread paste was relatively close with discrimination index 46.77% (before cooking) and 56.61% (cooked). Between before and after cooking, the aroma of Shihuyuan and Liubiju fermented flour paste had clear differences with the discrimination index 98.67% and 53.54%. The examine results of electronic tongue show that, before cooking wheat paste and steamed bread paste were obviously different in the taste, the discrimination index for them was 85.34%; after cooking, the taste between wheat paste and steamed bread paste was similar, the discrimination index was 69.34%. The sample of fermented flour paste before cooking, analysed by electronic tongue, with the discrimination index of more than 70% included wheat paste with Liubiju fermented flour paste, wheat paste with Shihuyuan fermented flour paste, steamed bread paste with Wangzhihe fermented flour paste, steamed bread paste with Xinhe fermented flour paste; after cooking, all the discrimination indexes among seven kinds of fermented flour paste were less than 72%, and the difference of Liubuju with Tianyuan was the smallest one, the discrimination index was 3.83%, the second smallest one is the difference of wheat paste with Wangzhihe fermented flour paste, the discrimination index was 5.09%.The innovation of the paper was that using the technology of GC-O, electronic nose and electronic tongue, and combining with the results identified by GC-MS to analysis volatiles in Chinese traditional fermented paste. All these results would offer valuable information for the flavoring and quality control of fermented flour paste in production.