泊松过程在用户上下线模型中的应用

提出了基于非齐次泊松过程的宽带拨号上网(ADSL)用户上下线模型.对用户上下线行为进行建模,并基于现网真实数据,使用模型计算用户24 h内的每时刻退出登录的平均概率,将模型的预测值与现网实测数据进行对比,分析了不同用户组退出登录概率一天内的变化和持续在线平均概率的变化.分析结果表明,提出的ADSL宽带用户上下线模型可以有效、量化地描述用户上下线行为,在ADSL宽带用户上下线行为的异常检测和舆情分析等领域具有较好的工程应用价值.     

Synergetic effects of high-pressure carbon dioxide and nisin on the inactivation of Escherichia coli and Staphylococcus aureus

Synergetic effects of high-pressure carbon dioxide (HPCD) and nisin on Escherichia coli and Staphylococcus aureus were evaluated. Changes in morphology, interior structure, and membrane permeability were analyzed by scanning and transmission electron microscopy, and flow cytometry. Synergetic effects were found, especially in S. aureus. HPCD alone or with nisin led to morphological and intracellular alterations in both bacteria, but nisin alone led to these damages only in S. aureus. A positive correlation between membrane damage and inactivation was found, but ratios of inactivation were higher, probably because of viable but non-culturable state. Mechanisms were proposed for synergism: for E. coli, outer membrane was damaged first by HPCD, and then HPCD and nisin jointly acted on and destroyed the cytoplasmic membrane, leading to further intracellular damage by HPCD; for S. aureus, HPCD and nisin acted on the cytoplasmic membrane together leading to cell death.Industrial RelevanceEscherichia coli and Staphylococcus aureus are two common microorganisms, which exist widely in the environment and easily contaminate food such as vegetables and dairy products, respectively. Considering heat treatment may destroy some heat-sensitive quality of the products, this study evaluated synergetic effects of high-pressure carbon dioxide (HPCD) combined with the bacteriocin nisin. The investigations provided evidence for potentially combined application of HPCD and nisin to help keep food safe in the industry.     

Repurposing fish waste into gelatin as a potential alternative for mammalian sources: A review

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, film-forming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13–19°C to 23–25°C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30°C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.     

纳豆激酶的质量与安全评价研究进展

纳豆激酶是纳豆芽孢杆菌在发酵纳豆过程中产生的一种丝氨酸蛋白酶,具有溶解血栓等生理功能。本文就纳豆激酶的溶栓功能及机制做了简要的总结,着重综述纳豆激酶活力测定方法等质量指标及其安全性评价研究进展,展望了纳豆激酶产品开发与质量安全研究方向,以期为纳豆及其制品（含纳豆激酶产品）标准化提供理论基础。     

基于决策树方法的油炸型方便面品质评价研究

本实验以市场占有率为80%～90%的国内主要方便面生产厂家的12个主打品牌的205个油炸型方便面样品为研究对象,首先以8个专家感官评价项目为指标,采用K-均值法对感官品评数据进行了聚类分析;根据聚类分析结果再应用决策树分析方法,以15个物性检测项目为指标,建立感官品评和面条物性指标之间关系模型。结果表明,所建立的决策树模型吻合感官品评聚类结果的精度达到95.61%,实现了表达仪器测量值与感官品评之间关系的目的,可为油炸型方便面品质评价提供一种客观定量化的方法。     

食品相关产品质量安全智慧监管体系的构建思考

利用信息化技术构建食品相关产品的智慧监管体系是促进监管精准化,提升监管效能的重要手段之一。本文通过研究智慧社会下监管的智慧化发展,分析了我国食品相关产品目前监管模式及面临形势,提出了“大数据”食品相关产品质量安全智慧监管体系框架建议,对政府部门在新形势下做好食品相关产品质量安全监管工作提供参考和借鉴。     

Effect of high pressure carbon dioxide on alkaline phosphatase activity and quality characteristics of raw bovine milk

Novel food processing techniques would always be pursuits of researchers and food industry to avoid unfavorable thermal effects, especially in dairy and milk processing. In this study, effects of high pressure carbon dioxide (HPCD) on the activity of alkaline phosphatase (ALP) and main quality indices of raw bovine milk at 20 MPa using a batch system were investigated. A complete inactivation of ALP activity as exposure to HPCD treatment at 50 °C and 20 MPa for 50 min was observed. The protein and lactose content of HPCD-treated bovine milk hold steady, while pH value and total solids content decreased, turbidity and average particle size increased significantly (p < 0.05). Although a significant decrease of viscosity (p < 0.05) was observed, the Newtonian flow behavior of raw bovine milk did not alter. More obvious change of quality characteristics of raw bovine milk were observed as subjected to HPCD treatment at higher temperature or treated for longer period. Therefore, a compromise between controlling endogenous enzymes (and/or spoilage and pathogenic microorganisms) and retention of original/fresh like quality of foods should be introduced due to the nature of HPCD processing. It's suggested to keep raw bovine milk with low ALP activity and great quality treated with a batch HPCD apparatus at 20 MPa and 50 °C for 20 min.     

Photoelectrochemistry and spectroscopy of substituted polyanilines

The properties of four substituted polyanilines, poly(N-methylaniline), poly(m-methylaniline), poly(o-methoxyaniline), and poly(o-ethoxyaniline) have been examined by photoelectrochemical and spectroscopic techniques (Raman and XPS). The middle peak in cyclic voltammograms for poly(N-methylaniline) was ascribed to hydrolysis products such as benzoquinone, and in the case of poly(o-methoxyaniline) to branched forms. The photocurrent profiles of the substituted polyanilines resembled those of polyaniline to a large extent, with prolonged cathodic and anodic photocurrents given for the polymer in a state of high conductivity. With poly(o-ethoxyaniline) only short-lived photocurrents were obtained pointing to a more highly insulating material, also shown by the limited growth of this polymer. Raman spectra of the substituted polyanilines taken in situ revealed typical polyaniline Raman bands, while the largest shift in the υ_CN band (35 cm⁻¹) occurred with poly(N-methylaniline). A deconvolution of the N 1s signal in XPS scans showed nitrogens consistent with oxidised forms of the polymers: a high proportion of positively charged nitrogens for poly(N-methylaniline) and of imine nitrogens for poly(m-methylaniline).     

基于菠菜品质变化的冰箱冷藏保鲜效果综合评价

本文针对目前家电行业缺乏科学规范的冰箱冷藏保鲜效果评价方法及标准的问题,开展了基于品质多维解析及其衰变规律分析的冰箱冷藏食品保鲜效果评价方法研究。以典型冷藏食品——菠菜为代表,研究了冷藏天数(0、2、4、6、8 d)、冰箱不同储藏层数对冷藏菠菜理化、感官指标的影响。结果表明:失重率(X₁)、总色差(X₂)、叶绿素含量损失率(X₃)和维生素C含量损失率(X₄)体现了菠菜新鲜度的主要理化特性,主成分分析提取出前两个主成分,其贡献率分别为54.694%、29.732%,累计贡献率为84.426%。理化特性的评价公式为:F=0.648×(0.572X₁+0.075X₂+0.559X₃+0.595X₄)+0.352×(0.229X₁+0.883X₂-0.356X₃-0.064X₄)。多元统计分析筛选得出,光泽度(S₁)、硬度(S₂)、生青味(S₃)和总体印象(S₄)可作为菠菜新鲜度感官品质表征的主要指标。感官特性的评价公式为P=(0.352,0.101,0.049,0.498)×(S₁,S₂,S₃,S₄)×(95,85,75,65,30)T。综合理化、感官指标及其权重得出,总新鲜度的评价公式为G=P/F。本文构建了评价冰箱冷藏食品新鲜度的综合评价体系,并进行方法应用验证,为科学评价家用冰箱"实效"提供技术支撑与方法依据。     

青花椒香气快速气相电子鼻响应特征及GC-MS物质基础分析

利用HeraclesⅠ快速气相电子鼻采集我国主要产地青花椒电子鼻响应信号,运用主成分分析和显著响应信号筛选对不同产地青花椒进行挥发性物质模式分类与特征分析,结果显示,8 个产地青花椒分为3 类,表现为明显有差异的六维蛛网图谱特征。进一步采用气相色谱-质谱联用仪对其物质构成进行定性定量分析,共检测出68 种化合物,其中39 个成分为8 个产地3 类青花椒所共有。这些成分主要为烯类、醇类、酯类及少量其他化合物。烯烃和醇类化合物为主要构成物质,占青花椒挥发性物质总相对含量的89%以上,而烯醇比则是3 类青花椒主要物质构成差异所在,分别表现为顶坛青花椒烯醇均衡型（烯醇比1∶1）、沂蒙山青花椒显著高烯低醇型（烯醇比2.5∶1）,重庆、江津、金阳、洪雅、汉源、昆明高烯低醇型（烯醇比约2∶1）。研究结果对青花椒产地区分、香气分类与特征解析等技术研究与应用具有重要的意义。