Volatile components of a beef ½avouring prepared from a thermal reaction model system of enzymatically hydrolysed beef/amino acids/sugars were extracted by simultaneous distillation/extraction (SDE) and dynamic headspace sampling (DHS) methods, then subjected to aroma extract dilution analysis (AEDA) and dynamic headspace dilution analysis (DHDA) methods; 32 and 48 odour-active peaks were revealed from the SDE and DHS isolates, respectively. With the highest ½avour dilution (FD) factors, 2-methyl-3-furanthiol, 3-methylthiopropanal and 2-furanmethanethiol were identi¼ed as the key aroma compounds of the beef ½avouring by both sample preparative methods, SDE and DHS. Moreover, methyl propyl disulphide, ethyl-2-methylbutyrate, allyl methyl disulphide, thiazole, 1-butanol, 1-nonen-3-one, 2-ethenyl-3,5-dimethylpyrazine, (E, E)-2,4-heptadienal and 2-undecenal were also identi¼ed as important aroma components of the beef ½avouring.a Retention indices (RI) on DB-5/DB-Wax column. b Odour description as perceived by panelists during GC-O. c Flavour dilution factors were determined on DB-5/DB-Wax column. d Identi¼ed by comparing it with the reference compounds on the basis of MS spectra, RI, odour quality and authentic compounds. e Identi¼ed tentatively by comparing it with literature data on the basis of RI and odour quality. AROMA EXTRACT DILUTION ANALYSIS OF A BEEF FLAVOURING 189As summarized in Table 2, 48 odour-active compounds were identi¼ed by DHDA; 34 and 33 odour-active regions were perceived on the DB-5 and DB-Wax columns, respectively. The FD chromatograms are shown in Figure 2. On the basis of FD factors, the most potent odour-active compounds were 2-methyl-3-furanthiol (meaty, vitamin, 18′), 2-furanmethanethiol (roast, meaty, 26′) and 3methylthiopropanal (cooked potato, 28′), which were also identi¼ed as the key aroma-active compounds by SDE-c Flavour dilution factors were determined on DB-5/DBWAX column. FD factors of 1, 4, 16, 60 and 240 corresponded to purge volumes of 40 min, 10 min, 2.5 min, 40 s, 10 s respectively. d Compound identi¼ed by comparison with reference compound on the basis of MS spectra, RI, odour quality. e Compound tentatively identi¼ed by comparison with literature data on the basis of RI and odour quality. AROMA EXTRACT DILUTION ANALYSIS OF A BEEF FLAVOURING 1913-Mereapto-2-butanone is an important aroma component reported as character-impact compounds of process ½avouring from several Maillard model systems, such as ribose/ cysteine, 36 glucose/cysteine, 37 rhamnose-cysteine 37 and cysteine/IMP. 34,36 It was also identi¼ed as a key odouractive compound in this study, especially in the case of DHS-DHDA (FD = 3; see Table 2).Moreover, of all aroma-active components identi¼ed in this research, methyl propyl disulphide, ethyl-2methylbutyrate, allyl methyl disulphide, thiazole, 1-butanol, 1-nonen-3-one, 2-ethenyl-3,5-dimethylpyrazine, (E,E)-2,4-heptadienal and 2-undecenal, which have rarely been reported as beef ½avour compounds, were also important aroma components of the beef ½avouring. Fig...

Trends in soil temperature are important but rarely reported indicators of climate change. Based on daily air and soil temperatures (depth: 0, 20, 80, and 320 cm) recorded at the Nanchang Weather Station , this study investigated the variation trend, abrupt changes, and years of anomalous annual and seasonal mean air and soil temperatures. e differences and relationships between annual air and soil temperatures were also analyzed. e results showed close correlations between air temperature and soil temperature at different depths. Annual and seasonal mean air and soil temperatures mainly displayed significant trends of increase over the past 58 years, although the rise of the mean air temperature and the mean soil temperature was asymmetric. e rates of increase in air temperature and soil temperature (depth: 0, 20, and 80 cm) were most obvious in spring; the most significant increase in soil temperature at the depth of 320 cm was in summer. Mean soil temperature displayed a decreasing trend with increasing soil depth in both spring and summer. Air temperature was lower than the soil temperature at depths of 0 and 20 cm but higher than the soil temperature at depths of 80 and 320 cm in spring and summer. Mean ground temperature had a rising trend with increasing soil depth in autumn and winter. Air temperature was lower than the soil temperature at all depths in autumn and winter. Years with anomalously low air temperature and soil temperature at depths of 0, 20, 80, and 320 cm were relatively consistent in winter. Years with anomalous air and soil temperatures (depths: 0, 20, and 80 cm) were generally consistent; however, the relationship between air temperature and soil temperature at 320 cm depth was less consistent. e findings provide a basis for understanding and assessing climate change impact on terrestrial ecosystems.

Using observational data from 2007 to 2010 at the Waliguan and Shangdianzi stations in China, atmospheric CO 2 , its δ 13 C composition, and their potential relationship with sources and sinks are studied.Results suggest that at Waliguan (WLG) station, both CO 2 and δ 13 C possess long-term trends and seasonal cycles that correlate well with each other. CO 2 and δ 13 C interannual variations indicate terrestrial ecosystem source-sink seasonal features in the midlatitude to high-latitude Northern Hemisphere. CO 2 annual means vary from 384.0 ppm to 390.2 ppm and increase in an approximately linear manner with a mean annual growth rate of 2.1 ± 0.1 ppm. The δ 13 C annual means vary from À8.30‰ to À8.35‰ and decrease almost linearly with a mean annual rate of À0.02‰ ± 0.001‰. Under the given conditions of terrestrial biosphere and anthropogenic activities at Shangdianzi (SDZ) station, the CO 2 annual means vary from 385.1 ppm to 390.6 ppm and approximately increase linearly with a mean annual growth rate of 1.8 ± 0.1 ppm. The peak-to-peak annual seasonal amplitude is 23.0 ppm. The δ 13 C annual means vary from À8.27‰ to À8.36‰ between 2009 and 2010. Mean values of À25.44‰ ± 0.72‰ and À21.70‰ ± 0.67‰ for the respective sources are obtained at WLG and SDZ. The estimated δ s values are more negative in winter and spring than in summer and autumn at WLG. While because substantial C 4 photosynthesis taking place in summer and biomass burning strongly contribute in winter, the estimated δ s values at SDZ are unusually heavier throughout the year and more positive than those at WLG.

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