不同宰杀方式对大菱鲆保鲜的影响

通过研究不同宰杀方式对大菱鲆鱼肉鲜度指标的影响,以寻找一种较好的宰杀方式来提高大菱鲆保鲜效果。实验采用4种方式宰杀大菱鲆:脉冲电击,CO2麻醉,放血,打头;宰杀后置于0℃下保藏,测定各组样品的K值、乳酸含量、pH值随时间的变化。实验结果:在保藏过程中,打头致死组K值升高最缓慢,0h时乳酸含量最低为1.5362mg/g(电击组、CO2麻醉组、放血组的乳酸含量分别为1.7415mg/g、2.4646mg/g、1.9912mg/g),0h时pH值最高为7.14(电击组、CO2麻醉组、放血组的pH值分别为6.99、6.78、6.91)。打头致死最有利于保鲜,其次为电击。     

杉木人工林树冠最大重叠系数及适宜经营密度的研究

本文在证明了开化县不同立地条件下松木胸径与冠幅相关规律无显著差异的基础上,建立了全县杉木胸径与冠幅的回归模型InCw=-0.2538 0.48221nD,R=0.9972,S=0.0480,并以此确定了杉木林分处于不同径阶时的基本经营密度指标。通过分析,本文提出了一种估计杉木林树冠最大可重叠系数K值的方法,修正了以往对K值估计偏小的现象。运用该K值计算了杉木人工林的饱和密度,并由此推导出了不同立地条件下郁闭度分别为0.6,0.7,0.8和0.9时的杉木经营密度指标。     

Comparison of 5′-inosine monophosphate and p-nitrophenyl phosphate degrading activities among red,pink, and white muscle fibers of cultured carp

ABSTRACT:   As part of a study to clarify the differences in the temporal change in K -value among fish species, the temporal change in K -value and the 5'-inosine monophosphate (5'-IMP) and p-nitrophenol phosphate (p-NPP) degrading activities in the red, pink, and white muscle fibers in the dorsal muscle of the carp were compared. The temporal change in K -value was fastest in red, followed by pink, and white muscle fibers, at both 0°C and 32°C. Moreover, the 5'-IMP and p-NPP degrading activities were highest in red, followed by pink, and white muscle fibers at near optimum pH concentrations. The 5'-IMP degrading activity at pH 7.0 had a positive correlation with the increasing rate of K -value at 32°C for all types of muscle fibers. These results suggest that differences in increasing rates of K -values between red, pink, and white muscle fibers corresponded to the 5'-IMP degrading activities.     

Change in translucency of squid mantle muscle upon storage

ABSTRACT:   Change in the translucency of squid mantle muscle during itsstorage at 0°C was studied by monitoring L* valueand turbidity. Two indicators showed that squid mantle muscle lostits translucency and reached maximal turbidity within 24 hof storage. Thickness of mantle muscle also increased by 15% in12 h, earlier than the loss of translucency. ATP contentdecreased with storage time and was completely lost in almost 24 h,a similar period to translucency loss, but later than rigor contraction.Development of black color on skin surface by chromatophores wasfully achieved in 24 h. It was thus concluded that ATPcontent was well correlated with a loss of translucency or increasein the turbidity of mantle muscle and development of dark coloron the surface skin of mantle.     

牙鲆在保藏过程中影响ATP关联化合物降解的因素

为了深入了解牙鲆体内ATP关联化合物的变化,尤其是肌苷酸(IMP)降解这一限速步骤,利用高效液相色谱法(high efficiency liquid chromatography,HPLC)测定不同保藏条件下牙鲆体内ATP关联化合物和K值变化,并探讨了影响其变化的因素。结果显示,0°C保藏条件下牙鲆体内ATP在1 d内迅速降解,产生IMP作为初期的主要积累物质,蓄积一段时间(10 d)后迅速降解为次黄嘌呤(Hx),IMP的降解过程呈现二相性;鱼肉制成鱼糜形态保藏,ATP 0 d时几乎降解完全,但IMP的降解过程仍旧呈现二相性;加入抗菌素的鱼肉中微生物的生长得到有效抑制,此时IMP降解缓慢并且呈线性下降,原本的蓄积过程消失,K值的增长速率也随之减慢;加入Tritonx-100破坏细胞膜结构发现,牙鲆体内IMP的降解速率加快,同时K值的增长速率也随之加快。结果表明,牙鲆的保藏形态影响ATP的降解速率,但几乎不影响其他关联产物的降解变化;保藏后期外源微生物产生的酶与内源酶的叠加作用是导致保藏后期IMP加速降解、从而呈现二相性的原因,微生物是影响ATP关联化合物降解的关键因素;表面活性剂通过改变细胞膜结构也能够影响IMP的降解过程。     

Biochemical,Physical, Chemical,and Microbiological Assessment of Blue Shrimp (Litopenaeus stylirostris) Stored in Ice

Postmortem changes in blue shrimp (Litopenaeus stylirostris) muscle were studied on the basis of biochemical, chemical, physical, and microbiological changes during an 18 day storage period at 0°C. Adenosine 5′-triphosphate (ATP) content, breakdown products, K-value, pH, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), water holding capacity (WHC), color, and texture (shear force) changes were examined. Also, total mesophilic and psychrophilic bacterial counts were measured. K-value increased linearly (r² = 0.98) from an initial value of 1.37 ± 0.59 to 59.42 ± 6.05% at Day 18. Spoilage indicators TVB-N and TMA-N increased from 29.56 ± 1.33 and 0.69 ± 0.25 to 39.04 and 2.04 ± 0.59 mg of N/100 g at Day 18, respectively; meanwhile, the total viable counts of mesophilic and psychrophilic bacteria increased from 3.48 ± 0.44 and 2.61 ± 0.29 log CFU/g to 6.27 ± 0.21 and 7.14 ± 0.39 log CFU/g, respectively, which indicated spoilage at the end of the storage period. The pH, texture, WHC, and color were affected (p < 0.05) during the storage period. Overall, results indicate that blue shrimp muscle quality was maintained for 12 days of storage in ice.     

黑龙江省土壤可蚀性K值特征分析

土壤可蚀性K值是评价土壤对侵蚀敏感程度和进行土壤侵蚀预报的重要参数,是支撑水土保持监测、预报和规划的重要基础。为了建立基于通用土壤流失方程的土壤侵蚀量估算数据库,需要掌握了解K值特征,该文采用对变量数字特征和离散程度的传统统计,以及克里格插值的地统计方法分析黑龙江省土壤普查相关数据和土壤可蚀性K值特征。结果表明:1)主要土类间土壤质地组分含量具有显著差异性,粗粉粒、细粉粒和黏粒含量服从正态分布且块金效应均大于75%,表现出很弱的空间相关性。2)主要土类K值期望,风砂土最大、白浆土最小,变异系数均小于10%,呈弱变异性。3)土壤质地K值期望,砂壤土最大、中黏土最小,总体上随物理性黏粒含量的增大而减小,随物理性砂粒含量减小而减小,除重黏土变异系数为19.99%,呈中等变异性外,其他土壤质地变异系数均小于10%,呈弱变异性。4)随表层厚度的增加,K值期望呈线性显著(R2=0.83)的平缓递减趋势。5)不同土壤侵蚀类型区域的K值及其分布特征差异较大,类型相同而强度不同的土壤侵蚀区域K值及其分布具有相似的分布规律。6)K值块金效应为73.30%,具有中等的空间相关性,自西向东呈平缓的线性递减分布趋势,由北至南呈上开广口抛物线状分布趋势,其极大值区与风砂土主要分布区,2个极小值区与白浆土、黑土主要分布区,具有空间一致性,此外,水土保持区划中分区的功能定位体现了K值的分布特征。该研究可为黑土资源的保护与修复提供科学依据,对黑土地能够继续、持续地保障粮食生产安全具有积极意义。     

Postmortem Biochemical and Microbiological Changes in Loricariid Catfish (Pterygoplichthys disjunctivus) Muscle During Ice Storage

ABSTRACT

Postmortem biochemical and microbiological changes in loricariid catfish (Pterygoplichthys disjunctivus) muscle were evaluated during ice storage for 20 days. Values of pH remained stable for 15 days (7.4 ± 0.2), and total volatile base-nitrogen (TVB-N) remained under acceptable limits throughout storage, with a final value of 25.2 ± 3.3 mg N/100 g muscle at Day 20. Adenosine-5´-triphosphate (ATP) and derivatives followed a postmortem degradation pattern similar to other species, with the K-value being the best freshness loss indicator. Biochemical and microbiological changes indicated that the shelf life of iced loricariid catfish muscle was 15 days under optimal (0°C) storage conditions.     

Influence of interposition of pink muscle fiber into dorsal ordinary muscle on temporal change of K-value in cultured carp

To clarify the influence of the interposition of pink muscle fiber into dorsal ordinary muscle on temporal change of K-value, using cultured carp, the dorsal muscle was divided into five muscle parts towards depth with the naked eye as follows: the dark muscle part (P-1), the intermediate muscle part (P-2) and three ordinary muscle parts (P-3, P-4, P-5). These were organized from the muscle fiber types as follows: P-1 was only red muscle fiber type. P-2 was only pink muscle fiber type in a thin layer and two muscle fiber types of not only pink muscle fiber but also white muscle fiber of the IIa or IIb subtype in a mosaic pattern. All of P-3, P-4 and P-5 were two muscle fiber types, white muscle fiber (IIa or IIb subtype) and pink muscle fiber. The temporal changes of K-values were remarkably faster in the order of P-1, P-2, and three parts of P-3, P-4 and P-5. The changes did not exhibit a remarkable difference among the three ordinary muscle parts. From these results, it was considered that the interposition of pink muscle fiber into the dorsal ordinary muscle might accelerate the temporal change of K-value.