Effects of microbial growth on the preservation of scallop muscle in a vital state

ABSTRACT:   Adductor muscles dissected from live scallop Patinopecten yessoensis were stored in oxygenated artificial sea water. The initial muscle adenosine triphosphate (ATP) level, approximately 7.5 µmol/g, remained longer at 5°C than at either 0 or 10°C. The pH of sea water decreased continuously and the consumption of dissolved oxygen increased even after muscle ATP was almost exhausted. The number of viable microbes, measured as colony-forming units (c.f.u.) in the muscle, increased to reach a plateau at approximately 10⁷−10⁸ c.f.u./g, while muscle ATP remained at high levels. After this time, muscle ATP sharply decreased. Antibiotics or sorbate added into the oxygenated sea water effectively inhibited both the growth of microbes and the decrease in the pH of sea water. Under these conditions, the retention period of muscle ATP was greatly extended. Thus, it seems most likely that scallop adductor muscle cells are suffocated by the limitation of oxygen supply caused by aerobic microbes grown on the surface of muscle tissue.     

Postmortem Changes in the Adductor Muscle of Scallop (Chlamys tehuelchus) in Chilled and Frozen Storage

Abstract

The effects of freezing and frozen storage on the biochemical properties of scallop adductor muscles stored at 2-4EC were investigated. Glycogen content fell 40% in the first 12 hr of chilled storage and decreased slowly thereafter. ATP content increased for a short time after death and then decreased slowly. Glycogen and ATP degradation was accompanied by a decrease in both pH and 260/250 absorbance ratio of scallop muscle extracts. A significant increase (p < 0.05) in the hypoxanthine (Hx) content was also observed in chilled stored adductor muscles. Adductor muscles showed a significant decrease (p < 0.05) in the 260/250 absorbance ratio of extracts and an increase in the Hx level after freezing. An increase in Hx content was observed during frozen storage of adductor muscles frozen immediately after processing. Expressible juice increased with freezing and frozen storage of the muscles. The results shown in this paper indicate a rapid loss of quality in scallop adductor muscles during storage at 2-4. Freezing and frozen storage enhanced the quality deterioration of the muscles.     

扇贝闭壳肌蛋白对鲢鱼肌肉蛋白凝胶的修饰

以栉孔扇贝闭壳肌蛋白、大豆分离蛋白、谷氨酰胺转氨酶为影响参数,鲢鱼肌肉蛋白凝胶的弹性、咀嚼性和持水性为响应参数,研究这3个因素对鲢鱼肌肉蛋白凝胶的修饰作用.通过单因素方法,分别就扇贝闭壳肌蛋白及大豆分离蛋白各自对鲢鱼肌肉蛋白凝胶的修饰作用进行了研究,结果表明,在一定范围内,添加扇贝闭壳肌蛋白和大豆分离蛋白可以改善鲢鱼肌...     

捕后干露对3种贝类活品品质的影响

为明确经济养殖贝类捕后早期干露耐受性,选取活力良好的菲律宾蛤仔、长牡蛎和虾夷扇贝在4℃条件下进行8 d的无水贮藏,以闭壳肌p H、糖原、腺苷三磷酸(ATP)关联化合物、磷酸精氨酸的含量和奥品脱氢酶活性为指标,研究3种贝类的品质变化规律.试验结果表明,无水贮藏期间,菲律宾蛤仔pH无明显变化(P<0.05),而长牡蛎和虾夷...     

Thermally induced gelation of paramyosin from scallop adductor muscle

ABSTRACT:   Thermally induced gelation of paramyosin from scallop smooth adductor muscle was investigated by dynamic rheological measurements under various conditions. The paramyosin thermal gel was produced at pH 6.5 and 7.2 at temperatures above 30°C through a two-step increase in storage (G') and loss (G') moduli; these values were higher than in gels produced from actomyosin at a high temperature. The thermal gel properties were very firm and brittle. In contrast, one main peak of G' was observed during gelation at pH 8.0. The gel produced at pH 8.0 was more transparent and less soluble in a 6 M urea−0.5 M NaCl solution than those formed either at pH 6.5 or 7.2. These differences in the thermal gel properties are presumed to derive from the pH dependence of the gel matrix-forming process, such as oxidative cross-linking between cysteine residues, rather than from the thermal unfolding of the paramyosin molecules. The thermal gelation profile of chymotrypsin-digested paramyosin showed marked depression of G' at high temperature.     

不同规格虾夷扇贝捕后耐干露特性比较

为探究商品虾夷扇贝规格与其活品耐藏特性之间的关联,对春季上市虾夷扇贝的规格及质量进行分组,再将各组置于4 ℃下湿布覆盖进行3 d冷却干露贮藏,分别于0、1、2 d和3 d采样进行生化代谢指标分析。试验结果显示,市售春季虾夷扇贝依据壳长大致可分成(105.8±1.5) mm、(98.4± 2.3 ) mm及(90.5±1.7) mm 3个规格组,各规格单贝质量相差20~30 g;(98.4±2.3) mm组扇贝的肥满度及闭壳肌出成率较其他两组高,(90.5±1.7) mm组三磷酸腺苷初始含量最高,表明其捕后胁迫耐力好于较大规格扇贝,(90.5±1.7) mm组扇贝同样表现出更好的耐干露特性,干露3 d 三磷酸腺苷含量和核苷酸能荷均明显优于其他两组;糖原含量各组无明显差异。此外,各组扇贝冷却干露2 d后存活率均为100%,干露至第3 d各组开始出现死亡,其中(90.5±1.7) mm组扇贝耐干露特性最好;各组闭壳肌pH与体腔液pH差异不显著;氨基酸分析结果发现,甘氨酸和精氨酸是扇贝闭壳肌游离氨基酸中含量最丰富的氨基酸,其余游离氨基酸变化趋势不明显;体腔液含氮物中,氨含量较高,其余氨基酸含量均较低并在干露期间无明显变化趋势。     

虾夷扇贝组织中微量元素的分布特性

研究了虾夷扇贝闭壳肌、外套膜、内脏团、瓣鳃和性腺中Cu、Fe、Mn、Zn、Pb和Cd等元素的分布特性。试验结果表明,内脏团中的Cu显著(P<0.05)高于其他各组织,其他各组织间差异不显著(P>0.05);闭壳肌中Zn的含量显著(P<0.05)高于内脏团、外套膜、瓣鳃和性腺中的含量;Fe含量内脏团和瓣鳃中显著(P<0.05)高于性腺、闭壳肌和外套膜;各组织中Mn的分布特性为瓣鳃>闭壳肌>性腺>内脏团>外套膜;Pb的分布特性为内脏团>闭壳肌>性腺>外套膜>瓣鳃;内脏团中的Cd占全贝总量的67%,显著高于其他组织。因此,约占全贝质量10%的内脏团蓄积了较高含量的Cu、Fe、Pb和Cd,尤其是Cu和Cd(分别约占全贝蓄积总量的71%和67%),食用时去掉内脏团,可保证虾夷扇贝的食用安全和较高的食用及营养价值。     

Myosin denaturation in heated myofibrils of scallop adductor muscle

The thermal inactivation of Ca²⁺ ATPase of scallop myofibrils (0.1 M KCl, pH 7.5) was found to be unaffected by the presence of Ca²⁺. Monomeric myosin content and salt solubility decreased much faster than Ca²⁺ ATPase inactivation in both Ca and EDTA media, which was well explained by faster denaturation of the rod portion than subfragment-1 of myosin. In contrast, when the myofibrils were heated at 0.5 M KCl, a slow decrease in salt solubility was observed, which was also explained by slow denaturation of the rod portion of myosin. Myofibrils from scallop smooth muscle showed the same denaturation pattern as those from adductor muscle. These results show that mollusk myosin is not always stabilized by Ca²⁺.     

Purification of transglutaminase from scallop striated adductor muscle and NaCl-induced inactivation

SUMMARY: Tissue type transglutaminase (TGase) was purified from scallop striated adductor muscle with successive chromatographies of DE-52 cellulose, Sephacryl S-300, and Mono Q columns. The yield and purification of the enzymatic activity was 16.6% and 101.9-fold, respectively. The molecular mass of purified enzyme was estimated to be 95 kDa by sodium dodecylsulfate–polyacrylamide gel electrophoresis analysis. Scallop TGase was Ca²⁺-dependent and strongly inactivated by ρ-chloromercuribenzoic acid, N -ethylmaleimide, Cu²⁺, and Zn²⁺, meaning it belongs to the thiol group of enzymes as well as being a mammalian enzyme. When scallop TGase was incubated in 0.5 M NaCl without substrate for 2 h at 20°C and pH 7.5, enzymatic activity decreased to 14.4% of its original. However, a conformational change in the TGase molecule was not detected by either fluorescent, ultraviolet, and circular dichroism spectra analyses compared to the enzyme incubated without NaCl. In addition, the enzyme inactivated by NaCl was partially recovered by the dilution of salt concentration, which means that the NaCl-induced inactivation process is reversible to some extent. These results suggest that NaCl-induced modulation of the TGase molecule occurs via a small conformational change.     

Identification of a resistant protein from scallop shell extract and its bile acid-binding activity

In this study, we showed that feeding rats the organic extract of scallop shells (scallop shell extract) caused a decrease in the weights of white adipose tissues in rats fed a high-fat diet. In addition, the cholesterol concentration in the serum of rats that received a diet containing scallop shell extract was significantly lower than that in the serum of rats on the control diet. Feeding this scallop shell extract to rats increased the fecal weight as well as the fecal excretion of bile acids. The amino acid composition of the feces from rats fed the scallop shell extract was different from that of feces from rats fed the control diet, and treatment of the extract with pepsin and pancreatin identified a protein with a molecular weight of 90 kDa (90-kDa protein) as one of the indigestible proteins. Interestingly the 90-kDa protein was found to be identical to a free radical-scavenging protein we previously identified and showed the ability to bind bile acids. These results suggest that indigestible proteins (resistant proteins) in the scallop shell extract, including the 90-kDa protein, inhibit the absorption of bile acid by binding to it and cause increased excretion of fecal bile acid, which subsequently may decrease the serum cholesterol level.     

Preparation of Water-Soluble Chitosan and its Suppressive Effect on the Denaturation of Scallop Adductor Muscle Myofibrillar Protein During Frozen Storage

ABSTRACT

In the present study, investigated were the preparation of water-soluble chitosan (WSC) by hydrolysis of original chitosan with commercial α-amylase and the suppressive effect of WSC on denaturation of bay scallop adductor muscle myofibrillar protein (Mf) during frozen storage at ?18°C for 12 months. The WSC (2.5- to 10-g dry weight) was added to 100 g of the Mf, and the changes in the Ca-ATPase activity, solubility, and sulfhydryl content were examined during frozen storage. The addition of WSC significantly reduced the denaturation of the Mf Ca-ATPase. Moreover, a significant increase in Mf solubility and sulfhydryl content was observed in the WSC-treated bay scallop adductor muscles compared with the control (p < 0.05) during frozen storage at ?18°C.     

五种海洋生物葡萄糖磷酸变位酶和磷酸葡萄糖异构酶的同工酶分析

采用水平淀粉凝胶电泳方法对虾夷马粪海胆（Strongylocentrotus intermedius）、刺参（Apostichopus japonicus Selenka）、半滑舌鳎（Cynoglossus semilaevis）、文蛤（Meretrix meretrix）和虾夷扇贝（Pecten yessoensis）不同组织中的葡萄糖磷酸变位酶（PGM）和磷酸葡萄糖异构酶（GPI）进行了检测分析。结果发现，虾夷马粪海胆肌肉组织和成熟性腺组织中的PGM有较强的表达活性和表达位点差异，两种组织中GPI活性稍差。刺参的肠道组织和肌肉组织只有PGM和GPI表达活性的差异，而无位点差异。半滑舌鳎肌肉组织检测到两个PGM位点，三个GPI位点。文蛤闭壳肌组织PGM表现出非常高的多态性，而GPI表现为单态。虾夷扇贝闭壳肌组织的PGM和GPI各只检测到一个位点，遗传变异程度比较低。以PGM和GPI为指标，对我国北方5种重要海水养殖品种的同工酶遗传变异水平和其它相关遗传参数进行了分析，对群体遗传结构可能的变化规律以及与某些性状的相关性进行了探讨，这些参数对它们的遗传选育有一定的指导作用。     

Induced triploidy in the bay scallop, Argopecten irradians, and its effects on growth and gametogenesis

Triploidy was induced in the bay scallop, Argopecten irradians, by treating newly fertilized eggs with cytochalasin B. Treatment for 20 min duration 10 min after fertilization resulted in 66% triploidy of scallops in the 0.05 mg/l cytochalasin treatment group and 94% triploidy of scallops in the 0.1 mg/l cytochalasin treatment group, detected by measuring the relative DNA content of scallop granulocytes using flow cytometry. Individually labelled scallops of known ploidy were grown in the Damariscotta River estuary in south-central Maine, U.S.A. from May 24 to September 15, 1982. Mean adductor muscle weight in triploid scallops was 73% greater than that of diploid controls and mean total body tissue wet weight was 36% greater. Shell inflation was significantly greater in triploids, while shell height and length were unaffected. The indexes of weight and glycogen content of the adductor muscle were significantly greater in triploids at the end of the growing season. The majority of triploid scallops failed to ripen during the summer months, while diploid scallops ripened and spawned.     

捕后暂养对虾夷扇贝闭壳肌硬化的影响

虾夷扇贝的捕后处置对闭壳肌的硬化产生重大影响,而硬化又是影响闭壳肌生食品质的重要因素。为延长虾夷扇贝死后硬化发生时间,通过宰杀前暂养,缓解捕后胁迫对后期闭壳肌贮藏特性的影响。将采捕后的虾夷扇贝分为3组(对照组、暂养3 d组和暂养7 d组),然后去壳取闭壳肌进行0~7 d冰藏,分析闭壳肌在贮藏过程中的僵直情况、ATP关联物、K值、p H值、糖原及水溶性蛋白等指标的变化。结果显示,不论是否经过暂养,冰藏3 d内K值均低于5%,可以满足生食要求。经过暂养,闭壳肌中ATP的含量略有升高,暂养7 d组暂养3 d组对照组。在贮藏0~2 d内,暂养组的ATP含量基本保持不变,可抑制肌肉收缩并减少汁液流失。暂养组的糖原含量和水溶性蛋白含量低于对照组。研究表明,30 ku蛋白在暂养组中的消失时间比对照组提前了1~2 d。扇贝采捕过程中应尽可能减少胁迫,采捕后应尽快加工,以免影响商品的品质及货架期。     

Antibrowning of the Adductor Muscles of Bay Scallop by Glutathione During Hot Air Drying

ABSTRACT

Browning in the adductor muscle of bay scallop (Argopecten irradians) tends to occur during hot air drying due to polyphenoloxidase (PPO) and Maillard reaction and decreases the sensory quality and commercial value of bay scallop adductor muscles (BSAM). In the present study, the effects of glutathione on the browning inhibition of BSAM were evaluated. The PPO activity in BSAM was inhibited by 97.8 with 0.08% glutathione. The browning of BSAM pretreated with glutathione was evaluated during hot air drying. Compared with the control, BSAM pretreated with glutathione resulted in less drying time and browning during hot air drying. The results indicate that pretreatment with glutathione may be a promising method of BSAM browning inhibition during hot air drying.     

Development of myofibrillar ATPase assay system on pH stat

The ATPase assay system on pH stat apparatus was developed. For the ATPase activity measurement, hydrogen ion (H⁺) concentration delivered from inorganic phosphate (Pi) as a hydrolysis production of ATP was estimated by titrating with 20 mM NaOH solution instead of colorimetric measurement of Pi. Inclusion of 0.5 M KCl in the ATP stock solution and 2 mM Tris-maleate (pH 7.0) buffer in the reaction medium reduced the extent of pH change upon addition of ATP to initiate the ATPase reaction. The amount of H⁺ liberated from Pi was strongly affected by the set pH for the ATPase assay with a promotion at alkaline pH. Thus, it was required to estimate the coefficient to convert H⁺ to a Pi concentration at a specific pH. The specified coefficient at pH 7.0 was 1.248. ATPase assay on pH stat allowed us to follow the ATP hydrolysis by myofibrils continuously showing a curvature profile at low salt medium (≤0.2 M KCl) or a linear profile at high salt (≥0.3 M KCl).     

中国对虾与海湾扇贝投饵混养的实验研究

用放在海水池塘中的8个陆基围隔(5.0m×5.0m×1.8m),研究中国对虾(Penaeuschinensis)与不同密度海湾扇贝(Argopectenirradians)投饵混养的放养方式、生产力和极限放养量.对虾体长(2.85±0.16)cm,扇贝壳长(1.10±0.12)cm,放养密度分别为6.0尾/m2和0,1.5,4.5,7.5粒/m2,用投饵和施肥(鸡粪和化肥)饲养.结果表明,扇贝密度为0和1.5粒/m2时,对虾的成活率无显著差异.混养(扇贝1.5粒/m2)时对虾的出塘体长、体重和产量分别比单养高2.5%,3.8%和6.5%;当扇贝密度高于1.5粒/m2时,对虾的平均体长、体重和产量随扇贝密度的增加而显著减少(P＜0.05).扇贝密度为1.5和7.5粒/m2时,其产量由470kg/hm2增至1236kg/hm2;当扇贝密度高时,去壳后湿重占体重的百分数从(42.84±3.44)%降至(37.88±4.26)%.扇贝的极限放养量为600～800kg/hm2,适宜放养密度为1.0～1.5粒/m2.     

栉孔扇贝不同组织中镉的微区分布特征及其变化规律

为阐明扇贝特异性富集镉(Cd)的机理,研究了栉孔扇贝不同组织中Cd的微区分布特征,并结合Cd的生物动力学实验研究了其变化规律。结果显示空白对照组栉孔扇贝内脏、鳃和性腺组织的Cd主要分布在类金属硫蛋白(MTLP)和细胞器中,闭壳肌组织中Cd主要分布在MTLP(占84.6%)。在Cd的富集实验中,内脏和鳃组织中MTLP和富含金属颗粒(MRG)中Cd的含量和所占百分比升高最显著,而细胞器中Cd的百分比明显下降;性腺组织中MTLP、细胞器和MRG组分中Cd的含量均明显升高,其中MRG中Cd的百分比升高,MTLP和细胞器中Cd的百分比逐渐下降;闭壳肌组织中MTLP和MRG中Cd的含量均显著上升,其中MRG组分中Cd的百分比显著升高。在释放Cd的实验中,内脏和鳃组织的MTLP中Cd的含量显著下降,而细胞器、热敏感蛋白(HSP)和MRG中Cd的含量和所占百分比逐渐升高,性腺组织各亚细胞组分中Cd含量均明显下降,但各亚细胞组分中Cd的百分比变化不明显;闭壳肌组织MTLP和MRG中Cd的含量下降,且MRG组分中Cd所占的百分比不断下降。本研究首次表明栉孔扇贝不同组织中Cd在亚细胞组分中的分布特征不同,并且在富集和释放Cd的过程中,内脏和鳃组织中的Cd在各亚细胞组分中不断发生调节和重新分配。     

黄海北部虾夷扇贝吊耳养殖技术研究

2010年进行了虾夷扇贝吊耳养殖试验研究。吊耳养殖分为一针四贝及一针二贝2种模式,经过6个月的对比试验,结果显示,与笼养方式相比,吊耳养殖扇贝的壳高增长率、单贝质量、贝柱质量、台产量、台产值等指标具有较大优势,存活率、肥满度、出丁率等指标互有优劣。在吊耳养殖模式下,虾夷扇贝壳高的生长优势明显,其中一针四贝模式的生长优势最大。本试验中吊耳养殖扇贝的总体生长情况优于传统的笼养方式;综合对比2种吊耳养殖模式,一针四贝模式的养殖效果好于一针二贝模式。