Haitao Chen

Triple-channel comparative analysis of volatile flavour composition in raw whole and skim milk via electronic nose, GC-MS and GC-O

A novel triple-channel comparative analysis of volatile composition in raw whole and skim milk (RWM and RSM) was developed via an electronic nose (E-Nose), headspace solid-phase micro-extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS), and gas chromatography-olfactometry (GC-O). Volatile flavour compounds from RWM and RSM caused the differences in mouthfeel characteristics by the human sensors, and also affected consumer preference. Solid state sensor technology, an E-Nose, was applied to distinguish the differences in volatiles between RWM and RSM. Headspace volatiles adsorbed by HS-SPME fiber (CAR/PDMS) were detected by GC-MS. Aroma compounds were identified by GC-O. Nine and three compounds were found to be aroma-active compounds from RWM and RSM, respectively. Octanoic acid, butanoic acid, and 3-hydroxy-2-butanone were found to be the most important aroma-active compounds in RWM, while the most important aroma-active compound of RSM was octanoic acid.

Rapid Synthesis of Flavor Compound 4-Ethyloctanoic Acid under Microwave Irradiation

Rapid synthesis of 4-ethyloctanoic acid by means of microwave irradiation is described. Diethyl malonate reacted with 2-ethyl-1-bromohexane in the presence of sodium ethoxide to give diethyl (2-ethylhexyl)malonate (1b). 1b was saponified in the solution of ethanol and potassium hydroxide and then acidified to form (2-ethylhexyl)propanedioic acid (1c), and 1c was heated and decarboxylized to give 4-ethyloctanoic acid (1d). The influence of reaction temperature and reaction time on the yield of 1b and the effect of reaction time on the yield of 1c and 1d were investigated in order to optimize the synthetic conditions. The relative optimal conditions for the synthesis of 1b were a mole ratio of sodium to diethyl malonate to 2-ethylhexyl bromide of 0.1:0.11:0.11, a reaction temperature of 80–85 °C, and a reaction time of 2–2.5 h. The yield of 1b was about 79%. 1b was saponified for 30 min and then acidified to form 1c, and the yield of 1c was 96%. 1c was heated for 16 min at 180°C to give 1d, and the yield of 1d was about 90%. The overall yield of 1d is 70% under microwave irradiation. The reaction time was reduced greatly. In order to compare the result of microwave irradiation with that of an oil bath, the reactions were also performed in an oil bath. The structures of intermediates, product and by-product were confirmed by HRMS, 1H NMR, 13C-NMR and IR.

Efficient synthesis of the odourant, 2-nonen-4-olide

A three-step synthesis of 2-nonen-4-olide starting from heptanal is reported. (E)-3-Nonenoic acid, prepared by Knoevenagel condensation of malonic acid and heptanal, was oxidised by performic acid, a process accompanied by lactonisation, to give 3-hydroxynonan-4-olide in 85% yield. This lactone when reacted with MsCl in the presence of Et3N gave, by elimination, 2-nonen-4-olide in 88% yield. The overall yield was 75%. The odour of the product was evaluated by GC-olfactory analysis and sniffing blotter confirming an oily, coconut-like, and rancid odour.

Synthesis and odor evaluation of five new sulfur-containing ester flavor compounds from 4-ethyloctanoic acid.

Five sulfur-containing flavor compounds were synthesized for the first time by the reaction of 4-ethyloctanoyl chloride with sulfur-containing alcohols or mercaptans. The synthesized compounds are 3-(methylthio)propyl 4-ethyloctanoate, 2-methyl-3-tetrahydro-furanthiol 4-ethyloctanoate, 4-methyl-5-thiazoleethanol 4-ethyloctanoate, 2-furan-methanethiol 4-ethyloctanoate and 2-methyl-3-furanthiol 4-ethyloctanoate. These five synthetic sulfur-containing ester flavor compounds all have meaty odor and might be used in foods if approved for this purpose in the future.

Preparation and odour properties of (S)-3-mercapto-1-heptyl acetate

Synthesis of (S)-3-mercapto-1-heptyl acetate was achieved in four steps. Sharpless asymmetric epoxidation of (E)-2-heptenol yielded (2R,3R)-2,3-epoxy-1-heptanol, which was treated with thiourea in the presence of Ti(OPri)4 to give (2S,3S)-2,3-epithio-1-heptanol, reduction of which followed by acetylation afforded (S)-3-mercapto-1-heptyl acetate in 91% ee. The optically active product possessed a tropical fruit aroma reminiscent of mango and passion fruit, with berry, ester-like, sweet, and pepper-like aspects.

Isolation and identification of antibiotic albaflavenone from Dictyophora indusiata (Vent:Pers.) Fischer

A sesquiterpene antibiotic was isolated from the dried fruiting body of Dictyophora indusiata (Vent: Pers.) Fischer by solvent extraction and column chromatography and identified as albaflavenone by FTIR, GC-MS, HR-FIMS and NMR spectra. The content of albaflavenone in the dried fruiting body of Dictyophora indusiata (Vent: Pers.) Fischer (the content of water was 15.63%) was quantified by GC through an external standard method to be about 0.0063%. The compound isolated has an earthy, camphor-like odour.

Characterisation of a by-product formed in the industrial production of γ -nonalactone

Distillation residues from the industrial production of γ-nonalactone, which is accomplished by reaction of hexanol with methyl acrylate initiated by t-butyl peroxide, yielded a by-product which we deduced to be 4-(methoxycarbonylethyl)-g-nonalactone. The possible pathway of formation of this by-product is discussed.

Identification of volatile components in yak butter using SAFE, SDE and HS-SPME-GC/MS

The volatile components of yak butter were isolated by solvent-assisted flavour evaporation (SAFE), simultaneous distillation extraction (SDE; dichloromethane and diethyl ether as solvent, respectively) and headspace solid-phase microextraction (HS-SPME; CAR/PDMS, PDMS/DVB and DVB/CAR/PDMS fibre extraction, respectively) and were analysed by GC/MS. A total of 83 volatile components were identified under six different conditions, including 28 acids, 12 esters, 11 ketones, 10 lactones, 10 alcohols, 4 other compounds, 2 aldehydes, 2 unsaturated aldehydes, 1 furan, 1 sulphur-containing compound, 1 unsaturated alcohol and 1 unsatruated ketone. Among them, 51 were identified by SAFE, 58 by SDE (45 with dichloromethane as solvent and 41 with diethyl ether as solvent) and 40 by HS-SPME (26 with CAR/PDMS; 26 with PDMS/DVB and 32 with DVB/CAR/PDMS). Three pretreatment methods were compared to show that the volatile components obtained using different methods varied greatly, both in terms of categories and in content. Therefore, a multi-pretreatment method should be adopted, together with GC/MS. A total of 25 aroma-active compounds were detected by gas chromatography-olfactometry, among which 20 aroma-active compounds were found by SDE (14 with dichloromethane as solvent and 14 with diethyl ether as solvent) and 17 by SAFE.