克氏原螯虾虾头酶解物挥发性风味成分分析

采用同时蒸馏萃取(SDE)和固相微萃取(SPME)两种方法提取克氏原螯虾虾头酶解物挥发性成分,通过气相色谱-质谱联用仪对挥发性成分进行分离鉴定,共得到了10类85种化合物,其中酮类最多达15种,其次是烃类和醛类各14种,醇类13种,另外酸类、酯类、酚类、含硫类、含氮类和含氧杂环类分别是6、7、2、3、5、5种。结果表明,克氏原螯虾虾头酶解物所特有的香气并非由一种或一类化合物单独形成。通过比较SDE和SPME法两种提取挥发性成分的方法可知,SPME法主要检出香气组分中的易挥发性化合物,它们代表了风味物质的"香气";SDE法则体现了"香味",它检测所得的化合物平均分布于整个检测区域。只有将两种方法结合起来,才能对产品的挥发性物质进行全面评价,为更好地开发和利用克氏原螯虾的废弃物提供了依据。     

小龙虾壳中虾青素的提取纯化工艺研究

目的优化纯化粗提品中虾青素的工艺,提高游离虾青素含量和提取率。方法以碳酸钠水溶液洗涤虾青素粗提品为去除杂质的最佳方法。结果洗涤条件是碳酸钠洗涤浓度0.025 g/mL,温度25℃,时间6 min,以虾青素的提取量和杂质沉淀量评价提取纯化工艺,提取量为375μg/g,杂质沉淀量为199μg/g。结论此法提高了虾青素的提取量,减少了杂质含量。     

油炸过程中淡水小龙虾理化性质与品质变化

研究分析油炸工艺（油炸温度（140、160、180、200 ℃）和油炸时间（15、30、45、60 s））对淡水小龙虾（虾壳、虾肉、虾黄）理化性质及品质的影响。测定淡水小龙虾中心温度、油炸损失率、色泽、质构特性、挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARs）值以及菌落总数（total plate count,TPC）的变化。结果表明：油炸温度对虾肉中心温度影响不显著,而油炸时间对虾肉中心温度影响显著（P＜0.05）;油炸温度180 ℃、油炸45 s时,虾肉中心温度可达到肌肉熟制标准温度;随着油炸温度升高及油炸时间延长,小龙虾油炸损失率显著上升（P＜0.05）;虾壳、虾肉、虾黄亮度值、红度值均呈上升趋势,而黄度值呈下降趋势;虾肉硬度、回复性、弹性、黏性、咀嚼性均显著增加（P＜0.05）;油炸过程中,虾肉TVB-N含量显著增加（P＜0.05）,但均低于10 mg/100 g,表明虾肉油炸后保持较好的新鲜度;虾肉TBARs值随油炸温度升高、油炸时间延长而增加,其中油炸时间对TBARs值影响较明显;新鲜虾肉初始带菌量非常高,油炸处理后虾肉TPC显著降低（P＜0.05）,油炸时间对虾肉TPC影响不明显。     

Crayfish assemblages correlate with dam-induced effects on abiotic factors and predatory fish assemblages in Alabama streams

Stream faunal assemblage structure is tied closely to hydrology and associated physiochemical properties. By altering natural flows, dams and their impoundments impact faunal assemblages over long distances. Although numerous studies have assessed the effect of dams on stream fauna, information is lacking for crayfishes. In this study, we characterized the effects of relatively large storage dams on crayfish assemblage structures. Over 2 years, we sampled three impounded and two unimpounded streams across two drainages in Alabama, United States, to identify biotic and abiotic factors correlated with crayfish assemblage metrics. Compared to impounded streams, unimpounded streams had greater habitat complexity (e.g., aquatic vegetation and woody debris), fewer predator fishes, lower minimum temperatures, and more variable discharges. These characteristics correlated with a higher density and diversity of crayfishes and smaller adults in impounded compared to unimpounded streams. Crayfish species assemblages differed between drainages, as did the biotic and abiotic factors affecting crayfish assemblages in each drainage, suggesting that these factors were species-specific in their effects. Additionally, analysis of land uses suggested that factors other than dams may have also contributed to the observed differences in assemblage structures between impounded and unimpounded streams. For instance, in the more urbanized drainage, crayfish assemblages were more similar between up and downstream sections in all streams, regardless of impoundment. Our results indicate that large dams alter stream crayfish assemblage structure, with potentially cascading effects in trophic and organic matter dynamics both up and downstream.