Application of Competitive Adaptive Reweighted Sampling Method to Determine Effective Wavelengths for Prediction of Total Acid of Vinegar

In this paper, near-infrared (NIR) spectroscopy coupled with wavelength selection methods was used to predict total acid of vinegar. Three wavelength selection methods including competitive adaptive reweighted sampling (CARS), Monte Carlo uninformative variable elimination (MC-UVE), and moving window partial least squares (MWPLS) were employed to select the key wavelengths. Five wavelengths including 4,348, 4,694, 5,365, 7,104, and 7,236 cm⁻¹ were selected by CARS method. Least squares (LS) regression model was built on the selected wavelengths. Compared to the partial least squares regression models based on full spectrum and wavelengths selected by MC-UVE and MWPLS, the performance of LS model was better, with higher determination coefficient for test (r ²) of 0.997, and lower root mean square error of prediction of 0.13 g/100 ml. Based on the results, it was concluded that NIR spectroscopy combined with CARS methods seem to be a rapid and effective alternative to the classical methods for the prediction of total acid of vinegar.     

椪柑籽油超临界提取工艺的优化

利用临界CO2萃取技术提取椪柑籽油。在单因素试验的基础上,采用Box-Behnken中心组合设计对椪柑籽油超临界CO2萃取工艺中的时间、温度、压力和流量4因素的最优化组合参数进行定量研究,得到各因素与椪柑籽油得率关系的数学模型。结果表明:最佳的工艺条件为萃取压力34.4MPa、CO2流量25.8L/h、萃取时间147.6min、萃取温度39.3℃。该条件下,椪柑籽油提取得率的理论值为45.95%,实测值为(45.12±1.36)%(n=3),说明回归模型能较好地预测椪柑籽油的提取得率。     

比较基因组揭示广西酸菜乳杆菌碳水化合物活性酶谱

微生物中的碳水化合物活性酶(carbohydrate active enzymes,CAZymes)具有降解植物组织的作用,相对于真菌,目前对于乳杆菌的CAZymes研究还比较少.该研究从广西酸菜中筛选获得了3株产CAZymes的乳杆菌,并通过二代测序技术比较其编码基因.16S rRNA测序结果表明3株乳杆菌分别是La...     

橘皮类黄酮的分离、纯化及结构鉴定研究

柑橘皮内含丰富的类黄酮化合物,具有多种生物学活性,受到医药、食品等行业的关注。本文通过硅胶、聚酰胺及Sephadex HL-20柱对温州蜜桔皮中类黄酮化合物进行反复分离纯化,得到5种类黄酮单体。采用LC-ESI-MS、1H-NMR和13C-NMR及红外光谱等技术对其结构进行鉴定。鉴定结果:化合物A,3,5,6,7,8,3’,4’-七甲氧基黄酮;化合物B,5,6,7,8,4’-五甲氧基黄酮;化合物C,3-羟基-5,6,7,8,3’,4’-六甲氧基黄酮;化合物D,5,6,7,8,3’,4’-六甲氧基黄酮;化合物E,橙皮素芸香糖苷。其中,化合物C是从温州蜜桔皮中首次发现的。     

柑橘全果制汁及果粒饮料的产业化开发

本文介绍了国内外柑橘汁加工业的现状及存在的问题,分析了柑橘全果制汁及果粒饮料的技术现状及产业化应用情况,并对我国全果制汁及果粒饮料的发展前景进行了展望。     

超声波辅助乙醇提取法提取玫瑰色素

采用玫瑰花提油后的花渣提取玫瑰色素,通过单因素试验和正交试验,确定超声波辅助乙醇提取法提取玫瑰色素的最佳条件为乙醇溶液浓度65%(V/V),pH 1,料液比1∶20(m∶V),提取温度70℃,超声波功率400 W,超声提取时间120min,该条件下色素的吸光值最大。     

酶法制备低甲氧基果胶的工艺优化研究

以酸橙皮渣为原料,在酸法提取果胶的基础上,向果胶提取液中加入外源性果胶酯酶,制备低甲氧基果胶.通过单因素试验和Box-Behnken设计以及响应面分析确定酶法制备低甲氧基果胶的最佳工艺参数为加入经1 000倍稀释的果胶酯酶5.39 mL、反应50 min、42.71 ℃、pH 4.61,在此条件下果胶酯化度由67.83%降低至42.55%.     

An ELIME-array for detection of aflatoxin B1 in corn samples

The aim of the present work was the development of an ELIME-array to achieve simple and rapid detection of AFB₁ in corn samples. The system is based on an indirect competitive ELISA format using magnetic beads as immobilisation support and eight magnetised screen-printed electrodes as electrochemical transducers.After an optimisation study, a corn sample treatment, employing an extraction in acetonitrile/water followed by a clean-up step and solvent evaporation, was selected.For the construction of the calibration curve, which was used to evaluate both evaluation of the matrix effect on the performances of the ELIME-array and for the analysis of Certified Reference Materials (CRMs), standard solutions of AFB₁ were added to blank dried corn extracts reconstituted in PBS. The detection limit and the sensitivity of the assay were calculated to be 0.6 ng mL^?1 and 1.5 ng mL^?1, respectively.Precision (11–26%) and recovery (95–114%) data of the ELIME-array, determined by analysing four CRMs, have shown that the proposed system appears suitable as a screening tool for the analysis of AFB₁ in corn samples.     

Revisiting Continental U.S. Hydrologic Change in the Latter Half of the 20th Century

An intensified hydrologic cycle and a large amount of monitoring flow data in the latter half of the 20th century attracted a lot of research on the continental U.S. hydrologic change. However, most previous studies are based on HCDN (Hydro-Climate Data Network) dataset with a period of ~1950s ?1988. This study analyzed hydrologic change in continental U.S. based on MOPEX (international Model Parameter Estimation Experiment) hydrology dataset with a period of ~1950s ?2000 for 302 watersheds (gages) across diverse climate, vegetation and soil conditions. This dataset is more representative of the latter half of the 20th century than HCDN. In contrast with previous studies, this study shows that only 20–30 % of watersheds present increasing trends in flow (streamflow, Q; baseflow, Q_bf; baseflow index, BFI), and most (> 65 %) watersheds presents non-significant trends. Similar to previous studies, the watersheds with increasing trends in Q and Q_bf are concentrated in Midwest and high plain (North-Central area) of USA. Climate contributes more to Q change (61?±?25 % vs. 39?±?25 %) but slightly less to Q_bf change than human activity (49?±?26 % vs. 51?±?26 %) and much less to BFI change than human activity (?5?±?61 % vs. 105?±?61 %). A step change at ~1971 in Q and Q_bf was found for 35–45 % but not for a large proportion of watersheds (50 % or more was reported by previous studies). This study provides new insights on the latter half of the 20th century’s hydrologic cycle for the continental U.S. with a more representative dataset of this period.