Fatty acid composition and sensory characteristics of lamb carcasses from Britain and Spain

Fatty acid composition of intramuscular fat in M. Longissimus was measured in four groups of lambs representing two Spanish breeds: Rasa Aragonesa (RA) and Merino (ME) and two British lamb types: the Welsh Mountain breed (WM), whose carcasses were purchased in Spain and typical early lambs (EL) purchased in Britain. The lambs grown in Spain were concentrate fed and slaughtered at a lighter weight and lower age than those grown in Britain. The British lamb carcasses purchased in Spain were of a similar weight to the Spanish lambs but were lighter than the lamb carcasses purchased in Britain. The British lambs were grass fed. Relationships between fatty acid (FA) composition and sensory attributes were examined following sensory testing of all lambs by both British and Spanish taste panels. The production system was shown to be more important than breed in determining FA composition. British lambs had higher percentages, within total fatty acids, of 18:0, 18:3 (n-3) and long chain polyunsaturated n-3 FA and lower percentages of 18:2 (n-6) and long chain polyunsaturated n-6 FA than Spanish lambs. These differences were due to the different feeding systems used. The amounts of these FA in muscle (mg/100 g) were also different between the British and Spanish groups, not only because the British lambs had more total fat. For both taste panels, odour and flavour intensity were positively correlated with the amounts and percentages of 18:0 and 18:3 and negatively correlated with those of 18:2. This was explained by the fact that both panels gave higher odour and flavour intensity scores to the grass-fed British lamb with high 18:3 levels and lower scores to the concentrate-fed Spanish lamb with high 18:2 levels. However, 18:0 and 18:3 were positively correlated with flavour quality and overall appraisal for the British panel and negatively for the Spanish panel. Conversely, 18:2 was a positive contributor to flavour and overall preference for the Spanish panel and was negative for the British panel. The results show that the production system affects muscle fatty acid composition and the flavour of lamb. However, people's preference is determined to a large extent by their past experience.     

On-line determination of fatty acid composition in intramuscular fat of Iberian pork loin by NIRs with a remote reflectance fibre optic probe

A near infrared spectrometer equipped with a standard 210/210 bundle remote reflectance fibre-optic probe, with a 5×5 cm quartz window type, was used for the determination of fatty acids in the Longissimus dorsi muscle of Iberian breed swine. The fatty acids C14:0, C16:0, C16:1, C17:0, C17:1, C18:0, C18:1, C18:2, C18:3, Σpolyunsaturated, Σmonounsaturated and Σsaturated were determined in samples of intramuscular fat from Iberian breed swine by direct application of the fibre-optic probe onto the loin sample, with no treatment or manipulation of the sample. The regression method employed was modified partial least squares. The calibration results using the fibre-optic probe for 74 loin samples had multiple correlation coefficients (RSQ) for C14:0, C16:0, C16:1, C17:0, C17:1, C18:0, C18:1, C18:2, C18:3, Σpolyunsaturated, Σmonounsaturated and Σsaturated acid of 0.785, 0.798, 0.788, 0.825, 0.762, 0.765, 0.696, 0.859, 0.878, 0.807, 0.943, 0.858, respectively, and standard errors of prediction corrected for the same fatty acids (%) of 0.08, 0.63, 0.26, 0.02, 0.02, 0.51, 0,77, 0.64, 0.05, 1.06, 0.34, 0.70, respectively. The robustness of the method was checked by applying the fibre-optic probe to unknown samples of Iberian breed pork loin in a slaughterhouse, using 15 samples for the external validation.     

Study of proteolysis during the processing of a dry fermented pork sausage

Dry pork sausage was formulated, fermented and dried for 41 days. Gross composition was determined and proteolysis was monitored by assaying the following N fractions: water-soluble nitrogen (WSN), salt-soluble nitrogen (SSN), ultrafiltration (UF) permeates of WSN and SSN, phosphotungstic acid (PTA)-soluble and -insoluble fractions and free amino acids. Meat and sausages, water- and salt-insoluble components, UF-retentates of WSN and SSN were assessed by SDS-PAGE at different stages of ripening.

The amount of WSN, WSN permeate, PTA-soluble N and free amino acids increased during processing, while the SSN and PTA-insoluble N decreased. The electrophoretic studies demonstrated that proteolysis of the heavy myosin chain, -actinin and actin was most prominent. The increased insolubility of meat proteins was confirmed by SDS-PAGE.     

Enzymatic changes in pectic polysaccharides related to the beneficial effect of soaking on bean cooking time

BACKGROUND: Cooking time decreases when beans are soaked first. However, the molecular basis of this decrease remains unclear. To determine the mechanisms involved, changes in both pectic polysaccharides and cell wall enzymes were monitored during soaking. Two cultivars and one breeding line were studied. RESULTS: Soaking increased the activity of the cell wall enzymes rhamnogalacturonase, galactanase and polygalacturonase. Their activity in the cell wall was detected as changes in chemical composition of pectic polysaccharides. Rhamnose content decreased but galactose and uronic acid contents increased in the polysaccharides of soaked beans. A decrease in the average molecular weight of the pectin fraction was induced during soaking. The decrease in rhamnose and the polygalacturonase activity were associated (r = 0.933, P = 0.01, and r = 0.725, P = 0.01, respectively) with shorter cooking time after soaking. CONCLUSION: Pectic cell wall enzymes are responsible for the changes in rhamnogalacturonan I and polygalacturonan induced during soaking and constitute the biochemical factors that give bean cell walls new polysaccharide arrangements. Rhamnogalacturonan I is dispersed throughout the entire cell wall and interacts with cellulose and hemicellulose fibres, resulting in a higher rate of pectic polysaccharide thermosolubility and, therefore, a shorter cooking time. Copyright © 2011 Society of Chemical Industry     

基于FEM-SVM的大坝可靠度分析方法

为解决复杂大坝可靠度分析计算时难以求得显示的功能函数和传统随机有限元计算时间长、工作量大等问题,提出将有限元(FEM)、支持向量机(SVM)和Monte-Carlo法相结合的可靠度分析方法,即采用正交试验设计具有代表性的样本点,通过有限元计算生成学习样本,利用支持向量机具有解决高度非线性、小样本问题的能力,建立结构响应量和输入变量的映射关系,再利用Monte-Carlo法,结合输入变量的概率分布生成随机样本进行结构可靠度计算。实例计算表明,FEM-SVM分析方法具有较好的精度,同时大幅减少了计算时长和工作量。     

基于无网格NS-PIM与有限元法的边坡应变能及位移上下限解研究

为尽可能精确求解边坡应变能及位移的上下限解的问题,结合无网格NS-PIM方法与有限元法,求解出了离散精度不同的边坡模型的应变能及位移,快速确定了精确解的分布范围,并依据工程精度要求,进一步细化模型以使计算结果逼近精确解。实例计算表明,NS-PIM方法、有限元方法可分别得到应变能和总体位移的上、下限解,为位移监测分析和边坡稳定性评价提供了良好思路。     

洪水不可控特性对水库防洪安全的影响

针对洪水进入不可控阶段给水库防洪安全水平带来的影响,主要探讨了水库洪水调度中反映安全水平的调洪最高水位、最快下泄时间两个参数,重点分析了起调水位、入库洪水量级和洪水是否可控的相互关系,提出判别洪水是否可控的条件,在此基础上提炼了最快下泄时间这个影响防洪安全的综合参数,并分析起调水位、洪水量级、调度方式对其影响的变化情况。实例应用结果表明,起调水位较洪水量级对最快下泄时间的影响大,且预泄对其影响也较为显著,为进一步构建水库洪水调度安全度量化评价系统提供了依据。     

防控支流库湾水华的三峡水库潮汐式生态调度可行性研究

三峡水库支流水华问题已成为影响库区生态和民生的重要问题,迫切需要采取有效防控措施。因三峡水库上游流域面积大,流域污染防治工作只能作为长期目标,生态调度可能是目前见效较快,最易接受的水华防控方法。通过总结防控支流库湾水华的生态调度研究进展,重点阐明了潮汐式生态调度对支流库湾水华的防控机理及效果。研究表明,水体分层是支流库湾水华发生的主要诱因;在支流库湾分层异重流背景下,潮汐式生态调度能够通过打破支流库湾水体分层,减小支流库湾水体滞留时间等方式抑制藻类水华;三峡水库调度试验表明,潮汐式生态调度不仅可有效缓解支流水华暴发强度,还能在常规调度的基础上增大三峡水库的综合效益,具有可行性,可作为三峡水库调度的定性指导方法。     

时效处理对Mg-5Sn-1Si合金显微组织和硬度的影响

研究时效温度、保温时间对Mg-5Sn-1Si合金显微组织和硬度的影响,分析时效处理的作用机制。结果表明,保温时间一定时,随温度升高,晶粒球化程度加强,析出相数量逐渐增加。温度一定的条件下,随保温时间延长,合金组织先后经过不连续析出、连续析出与网状析出三种变化,当保温时间较长时,第二相颗粒发生偏聚。合金经过时效处理后,显微硬度得到明显改善,比相应的铸态合金高出20%,随时效温度升高和保温时间延长,合金硬度均出现先升高后降低的趋势。     

三聚氰胺燃煤熔盐炉通过鉴定

山东海化魁星化工有限公司研制开发的三聚氰胺可拆卸式活动外罩燃煤熔盐炉最近通过鉴定,并获得国家专利。 该炉是在原三联双程燃煤熔盐炉基础上自行研制开发的国内首创的可拆卸式活动外罩熔盐炉,有效地解决了该公司6000 t/a三聚氰胺装置先天性供热不足的难题,使装置日产量提高了3 t多,并逐渐实现了稳产增产,年增经济效益161万元。该炉以煤为原料,以无机高温载体熔盐为载热介质,对工艺进行加热,广泛应用于化工、冶金等行业,可在300～1000℃范围内的多种工业领域使用,具有升温快、供热量大、运转平稳、高效节能、维修方便等特点。其外罩和每组膜管螺旋面均可迅速拆开、吊出,有效地解决了炉内维修所带来的困难和不便,并且使热效率和容量得到很大提高,为我国三聚氰胺行业熔盐炉的改造开辟了一条新路。