The purpose of this study was to modify the amount and composition of volatile components in bovine milk products, in an attempt to create a recombined skim milk product with full-fat milk flavor but with only 0.5% fat. The experimental plan included lipase-catalyzed hydrolysis and esterification reactions using Palatase 20000L (Novozymes, Bagsværd, Denmark). The results, measured by the methods of volatile compositional analysis and sensory evaluation, showed that the flavor profiles of the optimal recombined milk products were effectively modified in this way, possessing intensified characteristic volatile flavor components with rather low level of fat contents, and the sensory characters were quite realistic to natural whole milk flavor.
Kurut is a traditional acid-coagulated cheese from the northwest region of China. Using gas chromatography olfactometry and aroma extract dilution analysis, we identified 21 potent odorants from kurut within the flavor dilution factor range of 8 to 256. We developed a kurut matrix to determine the odor thresholds of key aroma compounds in kurut. The odor activity values of these 21 potent volatile compounds revealed that 18 were present at concentrations above their odor threshold values and therefore contributed to the overall aroma of kurut. The result of aroma recombinant experiments prepared by mixing the 18 most important odorants at the concentrations in which they occurred in kurut showed that the overall aroma profile of the recombinant sample was very similar to that of kurut. Omission experiments indicated that acids, furans, esters, and ketones were the most important volatile compounds in kurut. Some aroma compounds-such as butanoic acid, homofuraneol, ethyl hexanoate, and ethyl butanoate-play the most important roles in the overall flavor profile of kurut. Some odorants with a high flavor dilution factor, such as sulfur compounds, may have little effect. The study of key aroma compounds in kurut could provide important information for researching and developing traditional Chinese cheese products.
Bioaugmentation is an effective treatment method to reduce nitrogenous pollutants from wastewater. A strain of DYTN‐1, which could effectively remove TN from sewage, was isolated from the sludge of a wastewater treatment plant and was identified as Paracoccus denitrificans. The TN in wastewater reduced to <20 mg l−1 within 12 h under optimal conditions by free cells of P. denitrificans DYTN‐1. To enhance the removal of TN, P. denitrificans DYTN‐1 cells were immobilized in sodium alginate (SA) using different divalent metal ions as cross‐linking agents. It was found that the immobilized P. denitrificans DYTN‐1 cells could reduce the TN concentration from 100 to below 20 mg l−1 within 8 h. After the optimization of an orthogonal experiment, the immobilized P. denitrificans DYTN‐1 cells could reduce the TN concentration from 100 mg l−1 to below 20 mg l−1 within 1 h and significantly reduce the fermentation cycle. These findings would provide an economical and effective method for the removal of total nitrogen in wastewater by immobilized cells of P. denitrificans DYTN‐1.
Significance and Impact of the Study
We identified a new Paracoccus denitrificans strain (DYTN‐1) for removal of the total nitrogen in wastewater. The total nitrogen could be removed effectively by P. denitrificans DYTN‐1 within 12 h in wastewater. Using sodium alginate as the carrier and Ba2+ as cross‐linking agent, the immobilized P. denitrificans DYTN‐1 cells could improve the removal efficiency of total nitrogen in wastewater and significantly reduce the fermentation cycle. The assay has provided an economical and effective method for the removal of total nitrogen in wastewater by immobilized cell.
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