Effects of Saccharomyces cerevisiae and Kluyveromyces marxianus on the Physicochemical, Microbial, and Flavor Changes of Sauce Meat during Storage.

Saccharomyces cerevisiae (S. cerevisiae) and Kluyveromyces marxianus (K. marxianus) are often used as fermenters in yogurt and alcohol, and have been less studied within meat products. The yeasts were added to sauce meat, and the uninoculated group served as a control in this study to examine and compare the changing patterns of physicochemical and flavor characteristics of S. cerevisiae and K. marxianus on sauce meat during storage. The changes in moisture content, aw, pH, thiobarbituric acid reactive substances (TBARS), and other flavor characteristics were measured in sauce meat during the first, second, fourth, and sixth months after production. The following factors were examined: moisture content, aw, pH, TBARS, peroxide value (POV), acid value (AV), soluble protein (SP), free amino acid (FAA), and volatile flavoring compounds. With VIP > 1 and p < 0.05 as the screening conditions, the partial least squares model (PLS-DA) was used to assess the distinctive flavor components in the sausages. The findings demonstrated that the three groups' changes in sauce meat were comparable during the first two months of storage but differed significantly between the 4th and 6th months. The moisture content, water activity, and pH of the sauce meat decreased gradually with the storage time; TBARS, AV, and FAA increased significantly; SP decreased significantly from 2.61 to 1.72, while POV increased to 0.03 and then decreased to 0.02. The POV and TBARS values of the yeast-infected meat were substantially lower than those of the control group, and the POV and TBARS values of the meat inoculated with S. cerevisiae were particularly decreased (p < 0.05). The POV and TBARS values of SC (S. cerevisiae group) decreased by 49.09% and 40.15%, respectively, compared to CK (the control group) at the time of storage until June. The experimental group (KM: K. marxianus group) significantly increased the SP and FAA values of the sauce meat (p < 0.05) by 32.4% and 29.84% compared to the CK group, respectively. Esters and olefins as well as alcohols and esters were much greater in meat that had been supplemented with S. cerevisiae and K. marxianus than in meat from the control group. In conclusion, inoculating sauce meat with S. cerevisiae can significantly enhance the quality and flavor of sauce meat while it is being stored.

Si-B Functional Group Exchange Reaction Enabled by a Catalytic Amount of BH3: Scope, Mechanism, and Application.

Functional group exchanges based on single-bond transformation are rare and challenging. In this regard, functional group exchange reactions of hydrosilanes proved to be more problematic. This is because this exchange requires the cleavage of the C-Si bond, while the Si-H bond is relatively easily activated for hydrosilanes. Herein, we report the first Si-B functional group exchange reactions of hydrosilanes with hydroboranes simply enabled by BH3 as a catalyst. Our methodology works for various aryl and alkyl hydrosilanes and different hydroboranes with the tolerance of general functional groups (up to 115 examples). Control experiments and density functional theory (DFT) studies reveal a distinct reaction pathway that involves consecutive C-Si/B-H and C-B/B-H σ-bond metathesis. Further investigations of using more readily available chlorosilanes, siloxane, fluorosilane, and silylborane for Si-B functional group exchanges, Ge-B functional group exchanges, and depolymerizative Si-B exchanges of polysilanes are also demonstrated. Moreover, the regeneration of MeSiH3 from polymethylhydrosiloxane (PMHS) is achieved. Notably, the formal hydrosilylation of a wide range of alkenes with SiH4 and MeSiH3 to selectively produce (chiral)trihydrosilanes and (methyl)dihydrosilanes is realized using inexpensive and readily available PhSiH3 and PhSiH2Me as gaseous SiH4 and MeSiH3 surrogates.

Titanium-Catalyzed Exhaustive Reduction of Oxo-Chemicals.

Catalytic reduction of carboxylic acids and derivatives all the way to their corresponding methyl-compounds is very rare and still challenging for homogeneous transition-metal catalysis. Herein, we report an unprecedented and general catalytic exhaustive reduction of carboxylic functional group straightforwardly to a methyl group. This reaction was achieved using earth-abundant and readily available titanium as a catalyst. Our system has broad functional group tolerance and works for various other types of oxo-chemicals such as alcohols, aldehydes, ketones, lactones, and carboxylates (>100 examples). Preliminary mechanistic studies revealed that the in situ-generated TiIII -H species was vital for this transformation.

Total Nitrogen Sources of the Three Gorges Reservoir--A Spatio-Temporal Approach.

Understanding the spatial and temporal variation of nutrient concentrations, loads, and their distribution from upstream tributaries is important for the management of large lakes and reservoirs. The Three Gorges Dam was built on the Yangtze River in China, the world's third longest river, and impounded the famous Three Gorges Reservoir (TGR). In this study, we analyzed total nitrogen (TN) concentrations and inflow data from 2003 till 2010 for the main upstream tributaries of the TGR that contribute about 82% of the TGR's total inflow. We used time series analysis for seasonal decomposition of TN concentrations and used non-parametric statistical tests (Kruskal-Walli H, Mann-Whitney U) as well as base flow segmentation to analyze significant spatial and temporal patterns of TN pollution input into the TGR. Our results show that TN concentrations had significant spatial heterogeneity across the study area (Tuo River> Yangtze River> Wu River> Min River> Jialing River>Jinsha River). Furthermore, we derived apparent seasonal changes in three out of five upstream tributaries of the TGR rivers (Kruskal-Walli H ρ = 0.009, 0.030 and 0.029 for Tuo River, Jinsha River and Min River in sequence). TN pollution from non-point sources in the upstream tributaries accounted for 68.9% of the total TN input into the TGR. Non-point source pollution of TN revealed increasing trends for 4 out of five upstream tributaries of the TGR. Land use/cover and soil type were identified as the dominant driving factors for the spatial distribution of TN. Intensifying agriculture and increasing urbanization in the upstream catchments of the TGR were the main driving factors for non-point source pollution of TN increase from 2003 till 2010. Land use and land cover management as well as chemical fertilizer use restriction were needed to overcome the threats of increasing TN pollution.