《食品工业科技》F5000论文展播：SPME-GC-MS结合ROAV分析腐乳中的主体风味物质（2022年）

Objectives:Fermented soybean curd is deeply loved by consumers in the market because of its unique taste. Due to different ingredients, the flavor of products is also different. This paper studied the difference of flavor characteristics and components between self-made (M1 and M2) and supermarket(C1 and C2), to compare and analyze the flavor compositions and the key flavor substances of self-made products. The research findings provide basic data for the study of fermented soybean curd's flavor substances and production, as well as a reference for the development of high-quality products. 

Methods: 3 g of sample was transferred into 20 mL vail successively crimp sealed with a PTFE septum cap. The aroma volatiles of the sample were prepared by a SPME method as follows:  heated at 60 ℃ for 10 minutes using an automatic sampling system Gerstel MPS, and extracted with a coated 50/30um DVB/CAR/PDMS fiber for 30 minutes, then the fiber was desorbed for 300 seconds, The injector temperature was set at 250 ℃ and desorption was processed in splitless mode. The separation was carried out in an Agilent DB-5ms capillary column (30 m×250 μm i.d. ×0.25 μm film thickness). The GC oven temperature program started at 35 ℃（held for 5 minutes) and then was ramped to 80 ℃ at 3 ℃/min（held for 5 minutes) and to 200 ℃at 10 ℃/min (held for 20 minutes). The MS transfer line, source, and quadrupole temperature were 280 ℃, 230 ℃ and 150 ℃, respectively. The electron ionization mass spectrometer was operated at 70 eV in full scan mode (mass range: 30-450 amu). The volatile compounds were identified by comparison of their mass spectra with the NIST08 MS library, and using Kovats retention index (RI) based on the retention time of standard n-alkanes, Quantitative analysis was expressed as a relative ratio of the area of the volatile compound in the sample with the whole volatile compounds area of the sample. The main flavor substances were evaluated by combing the aroma threshold and relative odor activity value (ROAV).

Results:There were significant differences in the types and relative contents of volatile substances between the self-made products (M1 and M2) and supermarket products (C1 and C2). A total of 74 volatiles were identified. The number of flavor substances in M1 and M2 was more than those in C1 and C2. A total of 36 volatiles were identified in M1, with the highest relative content being alkenes, among which 3-carene accounted for 43.81%; A total of 31 volatiles were identified in M2, and the highest relative content was ether substances, of which anethole accounted for 44.91%, the content of anethole in M2 was 2~374 times that of anethole in other fermented soybean curd; The contents of hydrocarbons were the most in M1 and M2. A total of 27 and 14 volatiles were identified in C1 and C2, respectively. in which ethanol accounted for 58.70% and 59.45%, respectively. The relative content of esters in C1 and C2 is higher than that in M1 and M2, with a detection rate of 13.03% and 39.93%, respectively. ROAV showed that the key flavor substances were ethanol, phenol, 1-methoxy-4-(1-propenyl)-benzene, caryophyllene, 2-methoxy-3-(2-propenyl)-phenol, methyl salicylate, benzenepropanoic acidmethyl ester, benzenepropanoic acidethyl ester, dihydro-5-pentyl-2(3H)-furanone, decanoic acidethyl ester, hexadecanoic acidethyl ester and ethyl oleate.

Conclusion: The experimental results showed that there were differences in the main flavor substances and their relative contents between self-made fermented soybean curd and supermarket fermented soybean curd, which may be related to the different raw materials and processing technologies used. The research results will provide theoretical support for the formation mechanism of fermented soybean curd’s characteristic volatiles, and optimize production technology. GC-O-MS will expected to be used in future analytical study with a broad capacity for the identification of volatile compounds.