Search

Key aroma compounds in Chinese popular fried food of youtiao were characterized by solvent assisted flavor evaporation combined with gas chromatography‐mass spectrometry (GC‐MS) and aroma extract dilution analysis of gas chromatography‐olfactometry (AEDA/GC‐O), quantitation, and aroma recombination and omission. Four samples of youtiao fried with sunflower oil, soybean oil, rapeseed oil, and palm oil, respectively, differing in fatty acid composition, were selected to be investigated. A total of thirty‐five odorants were identified, among which twenty‐two odorants were quantitated by aid of authentic chemicals and with correction of recovery coefficients. Differences in odorants composition and aroma profile were observed among the four samples of youtiao fried with different oils. However, it was demonstrated in common thirteen compounds; that is, 3‐hydroxy‐2‐butanone, 3‐methylbutanal, furfural, 3‐(methylthio)propanal, 2‐furfurylthiol, phenylacetaldehyde, 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone, 2‐ethyl‐3,5‐dimethylpyrazine, 3‐ethyl‐2,5‐dimethylpyrazine, (E,E)‐2,4‐decadienal, 1‐octen‐3‐ol, (E,Z)‐2,6‐nonadienal, and (E)‐2‐nonenal contributed significantly to youtiao aroma. The work can provide some guidance to maintain the preferred youtiao flavor when modifying its preparation technology for safety concerns.

The unique flavor of Beijing Youji (BJY) chicken broth compared with that of commercial broilers (CB) was investigated by solvent-assisted flavor evaporation combined with AEDA/GC-O (aroma extract dilution analysis of gas chromatography-olfactometry), quantitation, and aroma recombination. A total of 71 odorants with almost the same major odorants (≥10 ng/g broth) were found by GC-O in both BJY and CB broths. However, BJY broth had thirty-two more extra odorants than CB broth, indicating the rich fragrance of the former. Aroma recombination and omission experiments demonstrated that 21 versus 17 odorants (with OAV ≥ 1) contributed significantly to BJY and CB broth aromas, respectively. Those key odorants mainly included sulfur-containing compounds and aliphatic aldehydes, such as 2-methyl-3-furanthiol, 3-(methylthio)propanal, ( E, E)-2,4-decadienal, etc. Furthermore, composition analysis of the meat suggested that the better flavor, with rather more odorants, of BJY broth is probably due to higher contents of polyunsaturated fatty acids and water-soluble flavor precursor, including ribose, cysteine, thiamine, etc., present in the BJY meat.

Heat transfer in molten salt in a cylinder tank is studied via simulation and experiment to obtain its natural convection heat transfer in a single energy storage tank. Simulation and experimental results show that the natural convection heat transfer of water in a cylinder tank fits well with Garon’s correlation. However, significant deviations occur when Garon’s correlation is used to predict the natural convection heat transfer of molten salt because of its high viscosity and low thermal conductivity. However, the simulated data of the natural convection heat transfer of molten salt fit well with those of the experimental results. Thus, a correlation that considers the effect of variable physical properties is proposed in this study to predict the natural convection heat transfer of molten salt. The deviation of the present data from the proposed correlation is less than ±20%. The results of this study can serve as a basis for the design of single energy storage tanks.

Volatile compounds formed in model reactions involving synthesized initial Maillard intermediates Gly-Amadori and [13C5]-2-threityl-thiazolidine-4-carboxylic acids ([13C5]-TTCA) in different molar ratios and free cysteine and glycine were investigated by solid-phase microextraction/gas chromatography-mass spectrometry and gas chromatography-olfactometry. The 1:1 ratio composition pattern provided the highest yields of all the sulfur-containing compounds, the potent meaty flavors or their 13C-labeled/unlabeled fractions, indicating a moderate level of glycine relative to cysteine was optimum for maximally yielding meaty flavors in complex meat-like Maillard systems containing cysteine as well as glycine. In addition, the 1:1 ratio composition led to formation of 13C-labeled molecules of some key meaty flavors e.g. 2-furanthiol representing over 70%, indicating TTCA/glycine reaction was better than Gly-Amadori/cysteine to yield meaty flavors. Formation pathways of twenty-nine flavors were elucidated based on the detected isotope distribution patterns. In particular, 2-methyltetrahydrothiophen-3-one, 3-thiophenethiol, 2-ethylthiophene, 2,5-dimethylthiophene, and 5-methylthiophene-2-carboxaldehyde involved a new formation pathway. Thiophene-2-carboxaldehyde and 2-methylthieno[3,2-b]thiophene showed two formation pathways.

In order to obtain the laminar natural convection heat transfer mechanism of molten salt, the natural convection heat transfer of multi-component molten salts around a cylinder with different diameters was studied by simulation. The result showed that the natural convective heat transfer of molten salt in the Rayleigh number range of 1.57×10-2 -2.03×106 cound be predicted by Fand's correlation that took the viscous dissipation into consideration, in addition to Prandtl and Rayleigh numbers. With the increasing in Rayleigh number, the effect of viscous dissipation decreased, so the other correlations that neglected the effect of viscous dissipation cound also predict the natural convection of molten salt well. Those results cound be a foundation for predicting the natural convection heat transfer of molten salt.