超高压和热杀菌对黄金贝可消化性和食用品质的影响

以黄金贝为原料,研究超高压和热处理两种杀菌方式对其可消化性以及食用品质的影响。以不同压力、保压温度及保压时间为因素,确定黄金贝的超高压杀菌条件;通过煮沸不同时间确定热处理杀菌条件;比较不同杀菌条件下对黄金贝可消化性、质构、色差和持水性的影响,进一步优化杀菌条件。结果表明,在500 MPa、30 ℃、30 min,400 MPa、40 ℃、30 min和600 MPa、40 ℃、20 min以及沸水处理≥5 min可以彻底杀灭黄金贝中全部微生物。与未处理的鲜贝相比,超高压处理显著提高了贝肉在模拟胃肠液中的消化率,其中500 MPa、30 ℃、30 min和400 MPa、40 ℃、30 min条件下处理的贝肉水解产生氨基酸量保持在较高水平。400 MPa、40 ℃、30 min处理的黄金贝在硬度和咀嚼性方面较未处理组变化最小,同时弹性得到提升。超高压处理可以使黄金贝亮度值增加。400 MPa、40 ℃、30 min条件下高压处理,贝肉的持水率比未处理提高了一倍,而热处理持水率最低,仅有6.25%。因此,400 MPa、40 ℃、30 min超高压处理的黄金贝消化性和食用品质最佳。     

纳豆菌发酵扇贝裙边制备ACE抑制肽的工艺优化

为了开发安全、无副作用的食物源ACE(angiotensin converting enzyme,ACE)抑制肽,本文采用纳豆菌(Bacillus natto)发酵扇贝裙边,以多肽含量和ACE抑制率为指标,通过单因素试验对发酵时间、发酵温度、接种量和液料比等工艺参数进行研究,并采用Box-Behnken响应面分析法优化工艺条件,建立二次多项数学模型。结果表明回归模型能较好地反应各因素水平与响应值之间的关系,各因素对多肽含量的影响顺序为时间液料比接种量温度,各因素对ACE抑制率的影响顺序为时间液料比接种量温度,纳豆菌发酵扇贝裙边制备ACE抑制肽的最佳工艺条件如下:发酵时间38.4 h,发酵温度39.9℃,接种量6.0%,液料比22.5。在上述发酵条件下制备的冻干品多肽含量高达238.91 mg/g,ACE抑制率达到83.70%。本文研究结果为扇贝加工废弃物的高值化利用和食物源ACE抑制肽的研究与开发提供了理论依据。     

Postmortem changes in the adductor muscle of Pacific lions-paw scallop (Nodipecten subnodosus) during ice storage

Postmortem biochemical, chemical, and physical changes of the adductor muscle of Pacific lions-paw scallop were studied during a 15-day storage period at 0 °C (ice). Content of ATP and breakdown products, K value, pH, trimethylamine, total volatile bases, water-holding capacity, colour, and texture changes were examined. K value increased logarithmically (r² = 0.95) from an initial value of 40.3–79.7% on day 15. The spoilage indicators trimethylamine and total volatile bases increased from 15.6 to 30.7 and 1.3 to 6.8 mg N/100 g of sample, respectively, which indicated spoilage at the end of the storage period. Texture, colour, and pH were not affected; however, water-holding capacity decreased significantly, from 96.0% on day 1 to 86.0% on day 15. Overall results indicated that quality of Pacific lions-paw scallop adductor muscle was maintained during at least 12 days of ice storage.     

高动态北斗B1I信号的快速捕获算法研究

高动态环境下,用户接收机接收到的卫星信号存在较大的多普勒频移,而实现定位导航和授时等功能对捕获算法提出了更高的要求.由于传统的时域串行捕获算法与基于FFT的并行码相位捕获算法存在时间复杂度高而造成捕获较慢的问题,本文采用改进的PMF-FFT捕获算法.捕获信号时,取2 ms输入信号与本地载波信号进行模二加后通过64个部分...     

从测量的散乱数据点云直接生成数控刀具路径的研究

提出了一种直接从测量的散乱数据点云用球头刀对自由曲面进行三轴数控加工时生成刀具路径的方法。不同于现有散乱点云基于逆向工程的刀具路径生成方法,本法考虑并估计了曲面加工误差和粗糙度。将散乱数据点云向XY平面投影,以获得的投影边界为刀具路径的主方向,然后根据曲面所需的加工误差和残留高度要求划分该投影数据点云,得到一系列刀位网格单元。通过最小化每个刀位网格单元的加工误差以确定每个刀位网格的节点位置,加权平均相关联刀位网格节点来对齐相邻刀位网格单元的边缘。为了缩短加工时间,裁去刀位路径上多余的线段,最终生成高效合理的数控加工刀具路径。已用实测的数据点云验证了本法直接生成刀具路径的有效性。     

Mesh-based tool path generation for constant scallop-height machining

This paper presents a new approach to mesh-based tool path generation for obtaining constant scallop heights. The mesh surface has recently become the focus of considerable interest, because its geometric computation is simpler and more robust than that of the parametric surface. These advantages make it easy to check and remove interference in the process of tool path generation. The previous tool path generation method based on the mesh surface, however, can generate only one topology of iso-planar type where tool paths have evenly spaced tool path intervals. As constant scallop heights cannot be obtained from evenly spaced tool path intervals, unevenly spaced tool paths based on offset meshes are necessary for reducing the machining time and for easy interference removal. This paper proposes and compares four methods to estimate curvatures from the mesh surface; the curvature is essential for calculating unevenly spaced tool path intervals. This paper also proposes an improved drive surface method to propagate CL-paths unevenly and to generate tool paths with various topologies.     

A CL surface deformation approach for constant scallop height tool path generation from triangular mesh

In this paper, we present a cutter location (CL) surface deformation approach for constant scallop height tool path generation from triangular mesh. The triangular mesh model of the stereo lithography (STL) format is offset to the CL surface and then deformed in accordance with the deformation vectors, which are computed by the slope and the curvature of the CL surface. In addition, the tool path, which is computed by slicing the deformed CL surface, is inversely deformed by those same deformation vectors to a tool path with a constant scallop height. The proposed method is implemented, and a tool path is generated and tested by simulation and by numerical control (NC) machining. The scallop height was found to be constant over the entire machined surface, demonstrating much better quality than that of mesh slicing, under the same constraints for machining time.     

基于分层阈值化的红外弱小目标检测算法

针对红外小目标视频图像信噪比低,小目标没有固定的大小形状等特性,提出了一种基于分层阈值化的红外小目标检测技术.对每一个连通域的形状、大小、边缘特性等进行评估,删除伪目标.对于一些固有的背景干扰,则利用先跟踪后检测的方法去除干扰.实验表明该算法具有良好的适应性,对于低信噪比的图片仍然具有良好的效果.     

不同热风干燥温度对扇贝柱干燥特性及品质的影响

对海湾扇贝贝柱进行了热风干燥试验,研究了在45℃,55℃和65℃等不同热风干燥温度下扇贝柱的干燥特性,并对所得干制品在品质和营养成分上进行了比较分析。结果发现,热风干燥温度越高干燥速度越快,水分活度(Aw)下降的也越快,在较高温度下的干燥时间要比较低温度下的干燥时间至少缩短5 h。但较高热风干燥温度下得到的样品与较低温度下的相比,其黏聚性、咀嚼性增大,样品亮度降低,粗蛋白含量较低,对口感、感官等品质造成不利影响。     

Distribution and spatial trends of PCBs in commercial scallops from Galician littoral (NW, Spain). Possible influence of biometric parameters

Levels and profiles of 10 individual congeners of polychlorinated biphenyls (PCBs) were studied in 3 species of commercial scallops (Pecten maximus, Chlamys varia, and Chlamys opercularis) from several Rías in Galician littoral (NW, Spain). ΣPCBs levels ranged from 2.21 to 41.0 ng/g wet weight for P. maximus, from 13.9 to 24.9 ng/g wet weight for C. varia, and from 1.58 to 24.3 ng/g wet weight for C. opercularis. The possible influence between biometric parameters (lipid content, condition index, and shell size) and PCBs levels were studied using statistical analysis (ANOVA). No relationship between biometric parameters could be established in the studied samples. Multivariate analysis showed there were differences in bioaccumulation of some PCBs congeners. Principal component analysis classifies clearly the 3 studied Rías (Ría de Ferrol, Ría de Arousa, and Ría de Vigo) taking into account PCBs levels found in the shellfish. PRACTICAL APPLICATIONS: We investigated levels and profiles of 10 congeners of PCBs in 3 commercial scallop species from the Galician littoral zone. The influence of 3 biometric parameters on polychlorinated biphenyls (PCBs) levels was also studied in order to assess results from the monitoring programs of production areas. According to PCBs levels, geographical differences were observed in commercial scallops from the 3 studied estuarine bays (Ría de Ferrol, Ría de Arousa, and Ría de Vigo).