真空包装青石斑鱼片在0 ℃贮藏时的品质变化特性

以感官特性、细菌总数、理化参数(基本营养组成、质构、色差、pH、TBA、TMA-N、TVB-N、K值、Ca²⁺-ATPase活性、SDS-PAGE)为指标,考察了真空包装的青石斑鱼片在0 ℃贮藏过程中的品质变化情况。结果表明,青石斑鱼片是一类高蛋白低脂肪的食品;气味和口感与贮藏时间均有显著正相关性(r=0.94和0.98),且口感评分比气味评分增加得快,但未达到阈值3分;细菌总数随贮藏时间呈显著递增(r=0.97),在第12天仍没有超过4 Log CFU/g,保持着一级鲜度,在第15天达到4.34 Log CFU/g,处于二级鲜度;硬度(r=-0.89)、胶黏性(r=-0.73)、咀嚼性(r=-0.87)与时间显著负相关;随着肌肉的老化,L^*值和C^ab值随贮藏时间显著下降(r=-0.91和-0.95),而b^*值与贮藏时间呈显著正相关性(r=0.99),肌肉逐渐呈灰色调、变暗、彩度明显下降;pH、TBA值在贮藏期变化不大,与贮藏时间弱相关,因此,不适合用于作为反映青石斑鱼片品质变化的指标;在贮藏期末,TVB-N与TMA-N与贮藏时间呈显著线性相关(r=0.86和0.99),其含量分别达到12.94 mg N/100 g和0.75 mg N/100 g,均低于腐败水平阈值;SDS-PAGE显示肌动蛋白球重链和肌动蛋白呈连续性的水解;Ca²⁺-ATPase活性下降速度较快,且与贮藏时间显著相关(r=-0.96);K值随贮藏时间延长而显著增加(r=0.98),贮藏末期达到54.91%,呈中等新鲜水平。因此,0 ℃真空包装下,其细菌总数增长缓慢,保持较好的感官品质及延缓TVB-N等理化指标的变化及和蛋白质的水解。感官指标、细菌总数、质构(硬度、粘附性和咀嚼性)、色度(L^*、b^*和C^ab值)、TVB-N、TMA-N、Ca²⁺-ATPase活性和K值在贮藏期内变化显著,且与贮藏时间显著相关,可考虑作为反映青石斑鱼片腐败的合适指标,但货架期的评定,需综合上述参数而定。     

高密度CO2与热处理对凡纳滨对虾肉品质的影响

高密度CO₂(DPCD)是未来非常具有前景的非热加工技术之一,可以实现对食品的杀菌和钝酶,并对其品质产生影响。为了探讨高密度CO₂对凡纳滨对虾肉品质的影响,实验以凡纳滨对虾为研究对象,采用DPCD和热处理,测定虾肉营养成分、质量损失、pH值、持水力、质构、蛋白质组成和呈味成分等的变化。结果显示:与鲜虾相比,DPCD处理会造成虾肉水分和粗脂肪含量显著降低(P<0.05),但粗蛋白含量无显著变化(P>0.05),而经热处理会使虾肉粗蛋白和粗脂肪含量都显著减少(P<0.05);DPCD处理造成虾肉质量损失达16.02%±1.90%,但对虾肉pH值无显著影响(P>0.05);DPCD和热处理都能使虾肉蛋白质发生变性,造成持水力显著下降(P<0.05),从(84.79±5.25) g/100 g分别下降至(65.18±2.06)和(65.58±2.08) g/100 g;DPCD处理对虾肉硬度无显著影响(P>0.05),而热处理则造成虾肉硬度显著升高(P<0.05),从(3.48±0.49) N上升到(7.37±0.76) N,DPCD处理和热处理都显著降低了虾肉弹性(P<0.05),从0.88±0.08分别下降到0.71±0.03和0.78±0.03;除甜菜碱、PO^3-₄、Cl^-,DPCD处理对虾肉主要呈味成分(游离氨基酸、ATP及关联化合物、有机酸、糖原等)无显著影响(P>0.05),而热处理则会造成大部分呈味成分的损失。实验表明,DPCD处理对虾肉品质的影响要小于热处理对虾肉品质的影响。     

岱衢洋和官井洋大黄鱼自交与杂交子代生长性能及杂交优势分析

2007年3月至2008年8月对象山港海区网箱养殖的岱衢洋、官井洋大黄鱼自交以及正反向杂交子代进行生长特性观察。结果表明:整个实验过程(0~526 d),官井洋大黄鱼自交子代(GG)和反交子代(GD)(官井洋♀×岱衢洋♂)大黄鱼较岱衢洋自交子代(DD)和正交子代(DG)(岱衢洋♀×官井洋♂)大黄鱼生长快,到526 d实验结束时,GG和GD体重分别达到330.514 g和336.694 g,而DD和DG则仅为278.975 g和243.297 g。对其各阶段生长速度分析,发现虽然一龄DD生长较慢,但过冬后DD生长明显加快,体长增长速度超过其他各群子代,体重增长也达到GG和GD增长水平,即有后期增长潜能。对比各群子代肥满度发现,526 d时,DD肥满度最低(1.675),GD肥满度(1.779)虽高于DD,但显著小于GG(1.933)。鉴于GD生长速度高于DD,与GG相当,而体型又优于GG,认为GD具有较大的经济养殖和优良品种选育的潜力。拟合各阶段体长体重数据,得出各群体生长曲线公式如下,DD:W=0.0206L^2.9427, R²=0.9949;GG:W=0.0139L^3.0994,R²=0.9785;DG:W=0.0229L^2.9136,R²=0.9905;GD:W=0.0177L^3.0079,R²=0.9949,拟合度较好,可通过体长估算体重,应用于实际生产。     

利用CRISPR/Cas9基因编辑技术敲除团头鲂socs1重复基因

以团头鲂细胞因子信号传导抑制蛋白1（SOCS1）基因socs1a和socs1b为编辑对象,在线分析并筛选出合适的靶点合成向导 RNA (guide RNA, gRNA),然后对1~2细胞期的团头鲂胚胎进行gRNA和Cas9蛋白的混合注射。通过荧光定量PCR技术在转录水平检测socs1a和socs1b的表达,并通过测序平台在DNA水平鉴定基因序列的突变,成功建立了多种socs1的突变品系。与同期野生型(WT)相比,socs1a突变杂合体（SOCS1a^+/-）和socs1b 突变杂合体（SOCS1b^+/-）团头鲂生长性能增强、体质量显著增加,同时炎症因子基因中肿瘤坏死因子α基因(TNF-α)和白细胞介素6基因(IL-6)表达量显著增加,而白细胞介素1β基因(IL-1β)表达无明显变化。注射嗜水气单胞菌后,与野生型不同的是,IL-6和TNF-α在SOCS1a^+/-和SOCS1b^+/-团头鲂肝脏中的表达均有持续显著上升。本实验通过CRISPR/Cas9系统成功敲除了团头鲂socs1a和socs1b,为进一步探讨socs1的作用提供了一定的研究基础,同时为CRISPR/Cas9基因编辑技术在养殖鱼类中的合理应用提供了依据和借鉴。     

第四代凡纳滨对虾抗WSSV选育家系的抗病及免疫特性研究

35个第四代凡纳滨对虾抗WSSV选育家系和未选育对虾按每克体重注射10³拷贝WSSV病毒量,根据选育家系的抗病性能分3个类群:高抗性类群,成活率达24.45%±6.56%;中抗性类群,成活率为10.70%±1.41%;敏感类群,成活率为2.72%±2.76%,各类群间差异显著(P＜0.01)。对分别代表高抗、中抗和敏感类群的12、7和3号家系以及未选育对虾按每克体重注射10²、10³、10⁴和10⁵拷贝 WSSV,高抗性对虾在10²、10³、10⁴及10⁵感染水平下的存活率分别为100%、23.3%±3.5%、7.8%±1.9%和0%;中抗对虾分别为87.7%±3.9%、12.2%±1.9%、0%和0%;敏感对虾分别为54.4%±3.9%、2.2%±1.9%、0%和0%;未选育对虾分别为51.1%±5.1%、0%、0%和0%。在10³拷贝组感染过程中免疫相关因子的变化表明,高抗对虾血液中血细胞数分别比中抗、敏感和未选育对虾提高20.7%(P>0.05),36.7%(P<0.05)和34.4%(P<0.05);PO活力上述三类对虾提高40.0%(P<0.05),76.3%(P<0.05)和63.4%(P<0.05);SOD活力分别比上述三类对虾提高31.1%(P>0.05),58.8%(P<0.05)和32.0%(P>0.05);POD活力分别比上述三类对虾提高29.6%(P>0.05),44.9%(P<0.05)和43.3%(P<0.05);血清蛋白含量分别比分别比上述三类对虾提高31.2%(P>0.05),38.7%(P<0.05)和39.3%(P<0.05),而敏感对虾和未选育对虾之间则无显著差异。结果表明,经四代选育后的高抗对虾免疫性能明显高于其他对虾,表现出良好的抗WSSV性能。     

中华绒螯蟹白壳和绿壳品系成蟹可食率、类胡萝卜素含量和营养组成的比较

为了评估白壳中华绒螯蟹与广泛养殖的绿壳品系成蟹营养品质是否存在差异，本实验通过采集白壳新品系与正常绿壳品系扣蟹在相同池塘中养至性腺发育成熟的商品蟹，测定其可食率、类胡萝卜素含量和营养组成。结果显示，两种色泽中华绒螯蟹组织系数、可食率和肥满度均无显著差异；白壳品系蟹壳湿样和干样亮度值(L^*)显著高于绿壳品系，但红度值(a^*)显著低于绿壳品系，肝胰腺和卵巢色泽参数无显著差异。白壳品系蟹壳总类胡萝卜素和虾青素含量显著低于绿壳品系，但两品系肝胰腺和卵巢中类胡萝卜素含量和组成均无显著差异。两种品系可食组织部分常规生化组成含量无显著差异，但白壳雌蟹肌肉中C20:4n6比例显著高于绿壳，绿壳雌蟹肝胰腺中18:0、18:2n6和DHA/EPA比例均显著高于白壳品系。两品系肌肉中大部分氨基酸组成和必需氨基酸评分均无显著差异，白壳雌体肌肉中异亮氨酸和酪氨酸含量显著低于绿壳雌体。研究表明，白壳和绿壳品系仅蟹壳的色泽和类胡萝卜素含量方面具有显著差异，其可食率、可食组织的常规生化成分、主要类胡萝卜素含量、脂肪酸组成和氨基酸含量接近，说明白壳品系中华绒螯蟹具有较大的推广潜力。研究结果为中华绒螯蟹白壳品系种质资源评价和进一步选育提供理论依据。     

不同养殖模式对斑点叉尾鮰生长和肌肉品质特性的影响

为探究不同养殖模式下斑点叉尾鮰的生长性能和肌肉品质特性,随机选取传统池塘（TP）、高密度循环水系统（HD-RAS）和水泥池塘（CP）养殖模式下的鲜活斑点叉尾鮰,测定其生长状况,以及肌肉营养成分、颜色、持水力和质构特性。结果显示,TP和HD-RAS的斑点叉尾鮰的增重率和特定生长率差异不显著,但均高于CP;CP的肝体比（2.35%±0.22%）显著高于TP和HD-RAS;与TP相比,HD-RAS和CP肌肉的粗脂肪含量更低,粗蛋白和灰分含量更高;HD-RAS肌肉的亮度值（L*）（58.18±3.56）、红度值（a*）（6.05±1.08）最高,CP最低,分别为48.15±6.04和4.81±0.84;传统池塘养殖的斑点叉尾鮰熟肉率最低,离心损失、滴水损失和失水率最高,HD-RAS和CP之间差异不显著;HD-RAS和CP肌肉的硬度、咀嚼性和弹性显著高于TP,但3处理组间的内聚性和回复性没有显著差异。研究表明,与传统池塘养殖模式相比,水泥池塘养殖模式易造成斑点叉尾鮰生长减慢,而高密度循环水养殖模式对斑点叉尾鮰生长性能没有显著影响,并且在该养殖模式下肌肉具有更高的持水力、质构特性,同时呈现高蛋白、低脂肪的营养特点。     

低盐度养殖的凡纳滨对虾体长和体重的增长规律

通过池塘陆基围隔实验，研究了凡纳滨对虾在最适水温、溶氧、pH及低盐度(2～6)养殖环境的生长特性及规律。实验结果，低盐度养殖健康对虾体长和体重平均生长率分别为1.398 mm·d^-1和0.169 g·d^-1，对虾前期体长呈线性生长，中后期体重呈加速增长。非线性拟合结果，对虾体长生长为二次曲线，符合Quadratic模型，体重增长为S型曲线，符合Boltzmann模型，生长观测值与模型拟合相关系数R²均达到0.99；凡纳滨对虾低盐度养殖典型体长和体重生长模型为L=7.843+2.297t-0.0105t²和W=16.541+(-0.621-16.541)/(1+e^{(t-54.809)/15.456})。低盐度养殖，对虾体长与体重呈立方关系，符合幂指数模型W=aL^b，a值范围4.9～9.0×10^-6，b值范围2.9495～3.0716，相关系数R²在0.99以上，典型幂指数模型为W=4.9×10^-6L^3.0716。     

饲料中添加硫酸锌对奥尼罗非鱼幼鱼生长合机体抗氧化功能的影响

试验以硫酸锌为锌源,评价不同锌水平对奥尼罗非鱼幼鱼（Oreochromis aureus♂×Oreochromis niloticus♀）生长和抗氧化能力的影响。体质量为(4.13±0.32)g罗非鱼随机分配在18个水族箱中,每箱20尾,每3个箱为1个处理组,分别以添加锌为0、20、40、80、160和320 mg•kg^-1的6种饲料投喂,日投喂率为鱼体重5%～9%。8周的试验结果表明：20mg•kg^-1锌饲料组的增重率和鱼体蛋白含量显著高于其它各组(P＜0.05),蛋白质效率、饲料转化率也明显高于其它各组;全鱼脂肪含量随着饲料锌水平的升高而升高,但320mg•kg^-1锌饲料组降低;20mg•kg^-1锌饲料组,脊椎骨中锌离子浓度达到最大值且显著高于0mg•kg^-1锌饲料组(P＜0.05);20mg•kg^-1与40mg•kg^-1锌饲料组的血液中红细胞数量显著高于其它各添加组(P＜0.05),20mg•kg^-1锌饲料组的血液中血比容显著高于0mg•kg^-1组(P＜0.05),与其它各组没有显著差异;肌肉中,硫代巴比妥酸反应产物(TBARS)(Thiobarbituricacid reactive substances)的量,锌为0mg•kg^-1饲料组显著高于其它各组(P＜0.05)。综上所述,饲料中锌添加量为20mg•kg-1饲料促进了罗非鱼生长,使鱼体抗氧化功能增强。     

仿刺参肠道潜在益生菌对稚参生长、免疫及抗病力的影响

以稚参期仿刺参为研究对象,探讨了分离自仿刺参肠道的潜在益生菌在稚参养殖中的应用效果。采用16S rDNA序列分析法将3株潜在益生菌分别鉴定为Bacillus sp.(GSC-1)、Bacillus sp.(GSC-2)和Enterococcus sp.(GSC-3)。分别以10³、10⁵或10⁷ CFU/mL的GSC-1、GSC-2、GSC-3或灿烂弧菌浸浴稚参以检验潜在益生菌对稚参期仿刺参的安全性,7 d后各潜在益生菌浸浴组的稚参成活率均高于同浓度的灿烂弧菌处理组;GSC-1和GSC-3在实验浓度下对稚参成活率无显著影响(P>0.05),可作为稚参的潜在益生菌;而10⁷ CFU/mL GSC-2浸浴组稚参的成活率显著低于对照组(P<0.05),因此GSC-2不适合作为稚参的潜在益生菌。将潜在益生菌GSC-1和GSC-3以10⁹ CFU/g的比例与鼠尾藻粉混合后饲养稚参20 d,潜在益生菌处理组的稚参成活率、特定生长率和变色率均高于对照组,其中GSC-1处理组稚参的成活率和变色率显著提高(P<0.05),GSC-3处理组稚参的成活率和特定生长率显著提高(P<0.05);与对照组相比,潜在益生菌GSC-1和GSC-3均有效增加了稚参的总菌数(P<0.05),GSC-1还有效降低了稚参的弧菌数(P<0.05);潜在益生菌GSC-1和GSC-3均可显著提高稚参体组织中的酚氧化酶和溶菌酶活力(P<0.05),GSC-1亦显著提高了其酸性磷酸酶和超氧化物歧化酶活力(P<0.05);GSC-1和GSC-3处理组稚参的抗灿烂弧菌感染能力均高于对照组,其中GSC-3显著降低了灿烂弧菌攻毒后稚参的死亡率(P<0.05)。综上所述,潜在益生菌GSC-1和GSC-3对稚参期刺参安全无毒,能够促进稚参的健康生长并提高其抗病能力,因而GSC-1和GSC-3均可作为益生菌应用于稚参养殖中。     

Quality and Sensory Characteristics of Volutharpa ampullacea perryi (False Abalone) Meat during the Boiling Cooking

Volutharpa ampullacea perryi (false abalone) meats were water cooked at 75–100°C for 5–60 min, and the changes in weight loss, pH, color, in vitro digestibility, texture, microstructure, and sensory characteristics were investigated. The weight rapidly decreased in the initial cooking and decreased slightly with the extension of both heating temperature and time. Obvious differences in color were found compared between the raw and cooked meats with respect to ΔL*, Δa*, and Δb* values. Digestibility was significantly improved with the thermal treatments. Textual properties, such as hardness, springiness, chewiness, and resilience, improved with the increasing of thermal intensity, but reduced with overcooking, and the variations were further confirmed by the scanning electron microscopy analysis. The samples boiled at 90–95°C for 10–15 min and 100°C for 5–10 min acquired better acceptance in the sensory evaluation. The complex relationship among cooking conditions and physicochemical and histological characteristics of meat as well as the consumer perceptions was illuminated by the principal components regression analysis. These results could provide useful information for quality control in V. a. perryi meat cooking.     

Effects of dietary astaxanthin source and light manipulation on the skin colour of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

Two experiments were conducted with Australian snapper Pagrus auratus (Bloch and Schneider, 1801). The first was aimed at determining the dietary level of astaxanthin that improved skin redness (CIE a^*values) of farm‐reared snapper. Farmed snapper (ca. 600 g) fed a commercial diet without carotenoids were moved to indoor tanks and fed the same diet supplemented with 0, 36 or 72 mg astaxanthin kg^?1 (unesterified form as Carophyll Pink?) for nine weeks. Skin redness (CIE a^* values) continued to decrease over time in fish fed the diet without astaxanthin. Snapper fed the diet containing 72 mg astaxanthin kg^?1 were significantly more red than fish fed the diet with 36 mg astaxanthin kg^?1 three weeks after feeding, but skin redness was similar in both groups of fish after 6 and 9 weeks. The second experiment was designed to investigate the interactive effects of dietary astaxanthin source (unesterified form as Carophyll Pink? or esterified form as NatuRose?; 60 mg astaxanthin kg^?1) and degree of shading (0%, 50% and 95% shading from incident radiation) on skin colour (CIE L^*a^*b^*) and skin and fillet astaxanthin content of farmed snapper (ca. 800 g) held in 1 m³ floating cages. After 116 days, there were no significant interactions between dietary treatment and degree of shading for L^*, a^* or b^* skin colour values or the concentration of astaxanthin in the skin. Negligible amounts of astaxanthin were recovered from fillet samples. The addition of shade covers significantly increased skin lightness (L^*), possibly by reducing the effect of melanism in the skin, but there was no difference between the lightness of fish held under either 50% or 95% shade cover (P>0.05).     

Quality Changes During Salt-Curing of Cod (Gadus morhua) at Different Temperatures

ABSTRACT

The main aim of this study was to assess the quality changes and their causes during cod salt-curing for up to 76 days at different temperatures and a relative humidity below 80%. Salt-curing made the fish more yellow (L*a*b* scale), a color change that is more easily detected in sensory analysis against a cream color scale. Intense proteolytic breakdown took place at 12 and 18°C, leading to a greater proteolysis degree and a higher pH. A red surface discoloration of the flesh was apparent after 76 days at 18°C due to the high number of red-halophilic bacteria. These bacteria were also responsible for the highest intensity of “off”-odors and mucus obtained under these conditions. Cod salt-curing should be done below 12°C to reduce the spoilage activity of halophilic bacteria and is best done at chill temperature (close to 6°C) to obtain a good quality product.     

Cage colour and post-harvest K+ concentration affect skin colour of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

In an attempt to improve post‐harvest skin colour in cultured Australian snapper Pagrus auratus, a two‐factor experiment was carried out to investigate the effects of a short‐term change in cage colour before harvest, followed by immersion in K⁺‐enriched solutions of different concentrations. Snapper supplemented with 39 mg unesterified astaxanthin kg^?1 for 50 days were transferred to black (for 1 day) or white cages (for 1 or 7 days) before euthanasia by immersing fish in seawater ice slurries supplemented with 0, 150, 300, 450 or 600 mmol L^?1 K⁺ for 1 h. Each treatment was replicated with five snapper (mean weight=838 g) held individually within 0.2 m³ cages. L^*, a^* and b^* skin colour values of all fish were measured after removal from K⁺ solutions at 0, 3, 6, 12, 24 and 48 h. After immersion in K⁺ solutions, fish were stored on ice. Both cage colour and K⁺ concentration significantly affected post‐harvest skin colour (P<0.05), and there was no interaction between these factors at any of the measurement times (P>0.05). Conditioning dark‐coloured snapper in white surroundings for 1 day was sufficient to significantly improve skin lightness (L^*) after death. Although there was no difference between skin lightness values for fish held for either 1 or 7 days in white cages at measurement times up to 12 h, fish held in white cages for 7 days had significantly higher L^* values (i.e. they were lighter) after 24 and 48 h of storage on ice than those held only in white cages for 1 day. K⁺ treatment also affected (improved) skin lightness post harvest although not until 24 and 48 h after removal of fish from solutions. Before this time, K⁺ treatment had no effect on skin lightness. Snapper killed by seawater ice slurry darkened (lower L^*) markedly during the first 3 h of storage in contrast with all K⁺ treatments that prevented darkening. After 24 and 48 h of storage on ice, fish exposed to 450 and 600 mmol L^?1 K⁺ were significantly lighter than fish from seawater ice slurries. In addition, skin redness (a^*) and yellowness (b^*) were strongly dependent on K⁺ concentration. The initial decline in response to K⁺ was overcome by a return of a^* and b^* values with time, most likely instigated by a redispersal of erythrosomes in skin erythrophores. Fish killed with 0 mmol L^?1 K⁺ maintained the highest a^* and b^* values after death, but were associated with darker (lower L^*) skin colouration. It is concluded that a combination of conditioning snapper in white surroundings for 1 day before harvest, followed by immersion in seawater ice slurries supplemented with 300–450 mmol L^?1 K⁺ improves skin pigmentation after >24 h of storage on ice.     

Effect of cage colour and light environment on the skin colour of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

A two‐factor experiment was performed to evaluate the effects of cage colour (black or white 0.5 m³ experiment cages) and light environment (natural sunlight or reduced level of natural sunlight) on the skin colour of darkened Australian snapper. Each treatment was replicated four times and each replicate cage was stocked with five snapper (mean weight=351 g). Snapper exposed to natural sunlight were held in experimental cages located in outdoor tanks. An approximately 70% reduction in natural sunlight (measured as PAR) was established by holding snapper in experimental cages that were housed inside a ‘shade‐house’ enclosure. The skin colour of anaesthetized fish was measured at stocking and after a 2‐, 7‐ and 14‐day exposure using a digital chroma‐meter (Minolta CR‐10) that quantified skin colour according to the L^*a^*b^* colour space. At the conclusion of the experiment, fish were killed in salt water ice slurry and post‐mortem skin colour was quantified after 0.75, 6 and 22 h respectively. In addition to these trials, an ad hoc market appraisal of chilled snapper (mean weight=409 g) that had been held in either white or in black cages was conducted at two local fish markets. Irrespective of the sampling time, skin lightness (L^*) was significantly affected by cage colour (P<0.05), with fish in white cages having much higher L^* values (L^*≈64) than fish held in black cages (L^*≈49). However, the value of L^* was not significantly affected by the light environment or the interaction between cage colour and the light environment. In general, the L^* values of anaesthetized snapper were sustained post mortem, but there were linear reductions in the a^* (red) and b^* (yellow) skin colour values of chilled snapper over time. According to the commercial buyers interviewed, chilled snapper that had been reared for a short period of time in white cages could demand a premium of 10–50% above the prices paid for similar‐sized snapper reared in black cages. Our results demonstrate that short‐term use of white cages can reduce the dark skin colour of farmed snapper, potentially improving the profitability of snapper farming.     

壳白长牡蛎品系生长和壳色性状遗传参数估计

以经过连续4代家系选育获得的壳白长牡蛎(Crassostrea gigas)选育系为亲本,通过巢氏平衡设计建立了30个全同胞家系混合养殖,采用微卫星多重PCR技术进行家系鉴定,基于REML法估算24月龄壳白长牡蛎的生长性状和壳色性状的遗传参数。结果表明,壳白长牡蛎品系壳高、壳长、总重、壳重、L~*(明度)、a~*(红绿轴色品指数)和b~*(黄蓝轴色品指数)的遗传力为中高等水平,依次为0.35±0.13、0.18±0.09、0.20±0.09、0.16±0.08、0.16±0.08、0.27±0.11和0.19±0.08,壳宽、肉重、出肉率、壳型指数A和壳型指数B的遗传力为低等水平,依次是0.07±0.02、0.11±0.06、0.02±0.03、0.08±0.06和0.11±0.06。壳高、壳长、壳宽、总重、壳重和肉重之间的遗传相关和表型相关均为正相关,其中,壳高、壳宽和总重与其他生长性状的相关性较高,分别为0.40±0.65~0.90±0.14、0.39±0.55~0.97±0.24和0.50±0.66~0.99±0.02。壳型指数A和壳型指数B与壳高均为较高的负相关,分别为–0.94±0.16和–0.77±0.19,表明仅以壳高性状为选育目标时,可能不会对长牡蛎壳型改良产生作用。壳白长牡蛎壳色参数与生长性状之间的遗传相关范围为–0.09±0.42~0.91±0.74,不同性状间的遗传相关差异很大,其中L~*与生长参数遗传相关较高,为0.49±0.29~0.91±0.74,表明以壳高、壳长、总重和L~*任一个为选育目标时,其他生长性状都可以获得提高。壳色参数间L~*与a~*负的相关性最高,为–0.96±0.04,L~*与b~*和a~*与b~*相关性较低,分别为–0.08±0.36和0.21±0.31,表明以L~*为选育目标时,可间接降低a~*值。本研究为合理制定壳白长牡蛎新品系育种方案和选择反应预测提供了参考依据。     

Textural and Sensory Properties of Herring (Clupea harengus) Cubes in Chinese-Type Paste as Affected by Prefrying Methods

The aim of this study was to determine the textural and sensory properties of herring (Clupea harengus) cubes prefried by deep frying (DF), mild frying (MF), and vacuum frying (VF) in Chinese-type pastes stored for 25 days at 13–15°C. Three groups of fish cubes in every Chinese-type paste were compared for texture, physical, and sensory properties by carrying out texture profile analysis (TPA), moisture content, color, and sensory analyses; and two types of Chinese-type pastes were investigated, oily Paste (A) and light Paste (B). The results showed that L* of fish cubes decreased significantly (p < 0.05), and a* and b* increased significantly (p < 0.05) in two kinds of Chinese-type pastes. Fish cubes prefried by DF and MF had higher sensory scores in Chinese-type Paste A, while those prefried by DF and VF had higher sensory scores in Chinese-type Paste B.     

Supplementation of sodium chloride in diets to improve the meat quality of Pacific white shrimp,Litopenaeus vannamei,reared in low‐salinity water

To investigate the effect of dietary sodium chloride (NaCl) on meat quality of white shrimp (Litopenaeus vannamei) reared in low‐salinity (2 g L^?1) water, shrimp were distributed into four groups (treatments T‐1, T‐2, T‐3 and control) with three replicates. All shrimps were completely randomised stocked into 12 tanks at an initial density of 40 shrimps per tank. Diets for the control, T‐1, T‐2 and T‐3 groups consisted of the basal diet supplemented with 0 g kg^?1, 10 g kg^?1, 20 g kg^?1 and 40 g kg^?1 of NaCl respectively. After 50 days, shrimps in T‐3 showed significantly better (P < 0.05) moisture, crude protein and ash than those of the control and T‐1. Higher muscle Na content was observed (P < 0.05) in T‐3 than that of the control. Significant increases (P < 0.05) in contents of inosinic acid, total free amino acid (TFAA) and essential free amino acid (EFAA) were also found in T‐3. Texture assays showed significant differences (P < 0.05) in hardness, adhesiveness and springiness between group T‐3 as compared with those of T‐1 and control. It indicated that dietary supplementation of NaCl appeared to be a promising practice to improve meat quality of white shrimp reared in low‐salinity waters.     

Change in flesh quality associated with early maturation of Atlantic halibut (Hippoglossus hippoglossus)

To determine the effect of maturation on flesh quality, 20 Atlantic halibut (Hippoglossus hippoglossus) consisting of mature and immature fish of both sexes were killed on site, exsanguinated and stored on ice. After 6 days of storage, the fish was gutted and filleted before colour, texture hardness and shear force were evaluated to determine the effect of maturation. Results show that mature males excreted black mucus from the skin during ice storage, while a greyish mucus was observed from immature fish. Mature fish had approximately 2% lower slaughter yield and 6% lower fillet yield compared with immature fish. The fillets from mature males were significantly harder compared with fillets from immature fish and the muscle structure proved to be stronger as an increased fracturability was observed in mature fish. In colour, fillets from mature fish proved to have a whiter appearance (L^*) than immature fish, while no difference was seen in a^* and b^* values. We conclude that the physiological changes associated with maturation affects the end quality, and may be related to slower growth.