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Processing methods significantly affect the aroma characteristics of red jujube; however, few studies have explored how. Gas chromatography–tandem mass spectrometric detection, gas chromatography–olfactometry, relative odor activity value and quantitative descriptive analysis were used to investigate the aroma changes of red jujube during typical processing (freeze drying, baking, frying and steaming); furthermore, the formation of aroma-active compounds in processed red jujube was predicted based on untargeted metabolomics. After freeze drying, the total aroma content increased by 0.90 %, while it decreased by 51.59 %, 74.11 % and 78.74 % after baking, frying and steaming, respectively. In addition, ethyl esters dominated the sweet and fruity notes in freeze-dried red jujube, which were formed via combination of fatty acids metabolism, pyruvate metabolism and amino acid catabolism. (E,E)-2,4-Decadienal derived from fatty acid oxidation dominated the fatty note in fried red jujube. 2-Ethyl-3,5-dimethylpyrazine formed via the Maillard reaction dominated the roasty notes of baked red jujube. [Display omitted] • The changes of key aroma of red jujube after different treatments were studied. • Formation pathway of key aroma in red jujube via different treatments was predicted. • Fatty acid oxidation and Maillard reaction led to key aroma changes in red jujubes. [ABSTRACT FROM AUTHOR]

Aroma profile and key aroma-active of red jujube subjected to pilot scale freeze drying (FD) were investigated based on molecular sensory science. After FD, 41 aroma compounds were identified through gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and quantified through calibration curves. The total aroma compounds content was decreased 26.71% compared with raw red jujube, of which ketones and acids contents were decreased 63.33% and 62.88%, while, the esters, lactones and alcohols contents were increased 34.10%, 8.52% and 480.17%, respectively. Through the GC-O-MS, odor active values combined with recombination and omission tests, 14 key aroma-active compounds were identification in freeze-dried red jujube. In which, 2-ethyl-3,5-dimethyl-pyrazine had the highest OAV (2687.00) and dominated the roast note of aroma profile. In addition, ethyl heptanoate, hexyl acetate, 2,3-butanediol, ethyl dodecanoate and 5-heptyloxolan-2-one were newly identified as the key aroma-active compounds in freeze-dried red jujube. [Display omitted] • Investigate the effect of pilot scale freeze-drying on the aroma of "Huizao". • Identify key aroma-active compounds in "Huizao" after pilot scale freeze-drying. • OAV and DFA were synergetic used to identify the aroma active compounds. [ABSTRACT FROM AUTHOR]

Both free and glycosidically bound volatile compounds of Ziziphus jujube cv. Huizao were comprehensively investigated in this study. There were 43 and 17 volatile compounds identified in free and bound fraction of "Huizao", respectively. Green, sweet, floral, fruity, cream, sour/rancid and nut notes could describe the aroma profiles through quantitative descriptive analysis. In terms of free volatiles, 22 compounds with odor activity values ≥ 1 and 21 compounds with detection frequency ≥ 2. 3-Hydroxy-2-butanone, butane-2,3-dione, methyl decanoate, ethyl decanoate, methyl dodecanoate, 5-propyloxolan-2-one, 5-butyloxolan-2-one, 2-ethyl-3,5-dimethyl-pyrazine, (E)-but-2-enoic acid, hexanoic acid, hexanal, 6-methyl-5-hepten-2-one, 3-oxobutan-2-yl acetate, 5-ethyloxolan-2-one, and 3-methyl-butanoic acid were identified as key aroma-active compounds in "Huizao" via recombination and omission tests. Moreover, key aroma-active compounds of 3-hydroxy-2-butanone, 5-ethyloxolan-2-one, (E)-but-2-enoic acid, hexanoic acid and 3-methyl-butanoic acid were also detected in bound fraction, aroma intensity of "Huizao" could be effectively enhanced by enzymatic hydrolysis. • key aroma-active compounds in "Huizao" identified by molecular sensory science. • Extraction and qualification of glycosidically bound volatile compounds of "Huizao". • OAV and DFA were used together to identify the aroma-active compounds. [ABSTRACT FROM AUTHOR]

Jujube is widely consumed fresh or used as ingredient in food industry, especially in China. Processed red jujube is characterized by a caramel-like and roasted aroma which contrasted with the sweet and fruity aroma of raw red jujube. The characteristic volatiles that contribute to this aroma have never been elucidated. The volatile organic components (VOCs) of baked and raw red jujubes were determined based on molecular sensory science including gas chromatography-mass spectrometry-olfactometry (GC-MS-O), aroma extract dilution analysis (AEDA), odor activity value (OAV), recombination, and omission experiments. Results revealed that 1-(2,6,6-trimethyl-1,3-cyclohexadien-1-yl)− 2-buten-1-one, 5-butyltetrahydro-2-furanone, and hexanoic acid were the common key odor active compounds in raw and baked red jujube. However, the baking process triggered the formation of aromatic hydrocarbon molecules in red jujube including 1 H -pyrrole-2-carboxaldehyde (0.21 μg/g), 3,5-dihydroxy-6-methyl-2,3-dihydro-4 H -pyran-4-one (34.15 μg/g), 5-methyl-2-furancarboxaldehyde (0.36 μg/g), and benzaldehyde (0.11 μg/g). [Display omitted] • The baking induced changes in key odorants of red jujube were investigated. • Caramel-like and roasted aroma were newly evaluated in the baked red jujube. • Aromatic hydrocarbon molecules were newly formed in the baking process. • The caramel-like and roasted aroma related odor compounds of baked red jujube were identified. [ABSTRACT FROM AUTHOR]

Haloarchaea with the capacity to degrade alkanes is promising to deal with petroleum pollution in hypersaline environments. However, only a limited number of haloarchaeal species are investigated, and their pathway and mechanism for alkane degradation remain unclear. In this study, Halogranum rubrum RO2-11, a haloarchaeal strain, verified the ability to degrade kerosene and hexadecane in 184 g/L NaCl, with 53% and 52% degradation rates after 9 and 4 days, respectively. Genome sequencing and gene annotation indicated that strain RO2-11 possesses a complete potential alkane-degrading pathway, of which alkane hydroxylases may include CYP450, AlmA, and LadA. Transcriptome and metabolome analyses revealed that the upregulation of related genes in TCA cycle, lysine biosynthesis, and acetylation may help improve hexadecane degradation. Additionally, an alternative degrading pathway of hexadecane based on dual-terminal β -oxidation may occur in strain RO2-11. It is likely to be the first report of alkane degradation by the genus Halogranum , which may be helpful for applications of oil-pollution bioremediation under high-salt conditions. [Display omitted] • Halogranum rubrum RO2-11 possesses a complete potential alkane-degrading pathway. • Hexadecane-degrading enzymes keep high activities even in the absence of alkane. • The degradation pathway involves alkane oxygenation and dual-terminal β -oxidation. • Upregulation of TCA cycle, lysine synthesis & acetylation may help for degradation. [ABSTRACT FROM AUTHOR]

Potato starches were pretreated with 600 W microwave and then acetylation was carried out with acetic anhydride and glacial acetic acid (1:1 in volume). The microwave-pretreated-acetylation remarkably modified the physicochemical properties of starch compared with the single acetylation method. The starch granules exhibited rough surfaces but maintained integrity and the crystal structure changed to C-type after microwave-pretreated-acetylation. Meanwhile, the microwave-pretreated starch esters exhibited the higher substitution degree, the higher infrared absorption peak intensity and the lower relative crystallinity compared to un-microwave-pretreated ones. The solubility of microwave-pretreated starches was higher at 80–90 °C than un-pretreated samples, while the swelling power of microwave-pretreated starches was lower at 60–90 °C under a same esterification level. Particularly, the solubility of microwave-pretreated samples at 90 °C was 2.11 times higher than un-pretreated ones, while the swelling power of microwave-pretreated starches exhibited 52.8% lower than un-pretreated samples at 90 °C under the 12 mL/100 g esterification level. The peak viscosity and the gelatinization enthalpy of microwave-pretreated starches were lower than un-pretreated ones under the same esterification level. Particularly, these values of microwave-pretreated starches were 2332 mPa s lower and 8.46 J/g lower than un-pretreated ones at the 12 mL/100 g esterification level, respectively. [ABSTRACT FROM AUTHOR]

Fluctuation disturbance of organic loading rate (OLR) is common in actual anaerobic digestion (AD), but its effects on AD of municipal sludge gets little attention. This study investigated the responses of reactor performance and active microbial community in mesophilic and thermophilic AD of municipal sludge before, during and after OLR periodic fluctuation disturbance. The performance of both reactors were similar before and after disturbance although some parameter values changed during the disturbance, which indicated their enough buffer capacity to OLR periodic fluctuation. Different microbial community at RNA level was observed in the two reactors. When the OLR disturbance commenced, the microbial community changed greatly in thermophilic AD. Error and attack tolerance of the microbial network was analyzed in order to learn the response mechanisms to OLR disturbance. The results assisted that the thermophilic microbial community was more vulnerable, but the reactor performance of which could be maintained using the functional redundancy strategy under OLR fluctuation disturbance. • Thermophilic AD of sludge showed higher performance than mesophilic AD. • Both reactors showed enough buffer capacity during the OLR disturbance period. • AD performance could recover to former situation after the OLR disturbance finished. • Microbial network of thermophilic AD was more susceptible to node removal. • Functional redundancy of thermophilic community could keep the reactor stable. [ABSTRACT FROM AUTHOR]

Chinese liquor fermentation is a typical solid-state fermentation process driven by various natural microflora, which is susceptible to ambient influence. A new-type sealing method using stainless steel as the pit cover was adopted as an alternative solution to mitigate the influence. In this study, we investigated the microbial consortia and the flavor metabolites in both the new-type sealing pit (NSP) and the traditional sealing pit (TSP). The study found the concentrations of most flavor metabolites (39 out of 58) in NSP were higher than TSP, and most of them concentrated at the bottom of both pits. The comparison revealed the diversities of microbes in different layers of pits were different (p < 0.05). The compositions of microbiota in different pits were different, albeit Lactobacillus was the absolute dominant genus in both pits. There were 13 dominant genera in NSP and seven in TSP. Therefore, more correlations between microbes were found in NSP, in which the microbial community was more stable. The interplay between different microbes and metabolites consequently resulted in different association patterns in different pits. These findings elaborate on the reasons behind the preference of the new-type sealing method and are instrumental to the optimization of the fermentation process. • The new-type sealing method could promote the production of flavor metabolites. • The new-type sealing method could improve the diversity of microbial community. • The microbial community in the new-type sealing pit has higher stability. • The association between microbes and metabolites are different between pits. [ABSTRACT FROM AUTHOR]

To explore the mechanism of heat-moisture treatment on starches and innovate the starch modification method, the wheat starch-water suspensions were subjected to repeated and continuous heat-moisture treatment (RHMT and CHMT) and investigate the changes and connections of molecular, morphological and physicochemical properties. The results showed that treated starches had many scallops but their shape unchanged compared with native starch. Primarily, the molecular weight emerged an increasing trend of modified starch as the time prolonged, which induced the changes of physicochemical properties. The crystal form of treated starches did not change but their crystallinity decline. The viscosities and swelling force of modified starch decreased while solubility, pasting temperatures and in vitro digestibility increased than that of native starch. The RHMT exhibited a more obvious effect in molecules rearrangement and the RHMT starch had a lower molecular weight, which could be used as a great potential to modify the starch physicochemical and functional properties. • Heat-moisture treatment increased the pasting temperature and digestibility of starch. • Heat-moisture treatment reduced crystallinity, viscosity and swelling power of starch. • Repeated heat-moisture treated starch had a more stable structure than continuous ones. • Repeated heat-moisture treatment had a better effect in rearranging starch molecules. [ABSTRACT FROM AUTHOR]