Key Aroma Compounds of Dark Chocolates Differing in Organoleptic Properties: A GC-O Comparative Study.

Dark chocolate samples were previously classified into four sensory categories. The classification was modelled based on volatile compounds analyzed by direct introduction mass spectrometry of the chocolates' headspace. The purpose of the study was to identify the most discriminant odor-active compounds that should characterize the four sensory categories. To address the problem, a gas chromatography-olfactometry (GC-O) study was conducted by 12 assessors using a comparative detection frequency analysis (cDFA) approach on 12 exemplary samples. A nasal impact frequency (NIF) difference threshold combined with a statistical approach (Khi² test on k proportions) revealed 38 discriminative key odorants able to differentiate the samples and to characterize the sensory categories. A heatmap emphasized the 19 most discriminant key odorants, among which heterocyclic molecules (furanones, pyranones, lactones, one pyrrole, and one pyrazine) played a prominent role with secondary alcohols, acids, and esters. The initial sensory classes were retrieved using the discriminant key volatiles in a correspondence analysis (CA) and a hierarchical cluster analysis (HCA). Among the 38 discriminant key odorants, although previously identified in cocoa products, 21 were formally described for the first time as key aroma compounds of dark chocolate. Moreover, 13 key odorants were described for the first time in a cocoa product.

Characteristic fruit wine production via reciprocal selection of juice and non-Saccharomyces species.

This study examines the effect of juices and non-Saccharomyces yeasts on physicochemical properties and sensory quality for fruit wines. Here, fruit wines produced from six kinds of fruit juices and eight non-Saccharomyces yeasts were evaluated, and the results show significant phenotypic diversity within these yeasts for wine fermentation on a range of substrates. Substantial variations in indicators such as total acid, sugar content and organic acid content were observed, which were caused by selection of both yeasts and juice types. These differences in characteristics had an impact on consumer preference. Considering overall acceptance by the panelists, correspondence analysis showed that Pichia kluyveri X31-10 (Pk31) was the most suitable strain for apple juice fermentation, and Fuji apple juice was the best substrate for this fermentation. A partial least-squares regression model of aroma characteristics against aroma components revealed that acetate esters were the primary contributors to tropical fruit aroma notes of ciders from Pk31. Additionally, 1-butanol, 3-methyl-, acetate; acetic acid, hexyl ester; and acetic acid, pentyl ester have been implicated as characteristic volatiles associated with Pk31.

Occurrence, profiles, and ecological risks of polybrominated diphenyl ethers (PBDEs) in river sediments of Shanghai, China.

Fifty-two PBDE congeners in river sediments from Shanghai were analyzed in the present study. The concentrations of Σ51PBDEs (defined as the sum of 51 BDE congeners except BDE209) and BDE209 ranged from 0.231 to 119 ng g(-1) and from nd to 189 ng g(-1), respectively. The most abundant BDE congeners in surface sediments were BDE118, 207, 208, 99, 49, 75, 47, 71 and 209, with median values of 1.67, 1.81, 1.83, 1.87, 1.98, 2.52, 2.73, 4.62 and 45.7 ng g(-1) dw, respectively. The concentrations of Σ52PBDEs were significantly correlated with total organic carbon (TOC) content in sediments (p < 0.05). Weak correlations between all PBDE homologues and TOC (r < 0.32) suggest that TOC had a little influence on sediment PBDE transport and distribution patterns in river sediments of Shanghai. Correspondence analysis (CA) showed that PBDEs in sediments in the studied area originated from commercial BDE formulations, combustion emission sources, and debromination of highly brominated PBDEs by aerobic/anaerobic microbes or sunlight. Risk assessment based on risk quotients (RQ) showed that PBDEs in all river sediments collected from Shanghai posed a high potential ecological risk (RQ > 1) to the sediment dwelling organisms, and pentaBDE, decaBDE and tetraBDE were the major ecological risk drivers.