Drying Kinetics and Quality Characteristics of Slightly Salted Grass Carp Fillets by Hot Air Drying and Vacuum Microwave Drying

Salted grass carp fillets were dried by hot air drying (HD, at 35 and 45°C) and vacuum microwave drying (VMD, at 1, 4, and 7 W/g) to a final moisture content. Compared with hot air drying, the vacuum microwave drying greatly reduced drying time. The rehydration rate constant of salted grass carp fillets dried by microwave vacuum drying at 7-W/g microwave intensity was significantly higher than that of the hot air drying at 35 and 45°C. Compared with hot air drying, the vacuum microwave dried samples had a higher crude fat content (dry basis). The lightness of the samples dried by vacuum microwave drying was higher, and the yellowness was lower than those dried by hot air drying. The drying methods had no significant effect on the hardness and springiness.     

Functional Properties of Water-Soluble Proteins from Silver Carp (Hypophthalmichthys molitrix) at Different pHs

Water-soluble proteins (WSP) from silver carp muscle are currently underutilized in China and are discarded into waste streams in surimi processing. In order to utilize WSP resources efficiently, this work investigated the effect of pH on the functional properties of WSP. With an increase in pH, the solubility decreased and then increased; the lowest solubility was observed at pH 4.0. Also, heat-stability, emulsifying activity index (EAI), and foamability decreased and then increased with increasing pH; the lowest values were shown at pH 5.0. The better heat-stability, EAI, and foamability were obtained at pH 3.0. An increase in total sulfhydryl content was observed when the pH was 3.0–5.0, and a decrease was obtained at pH 5.0–9.0. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of WSP treated at various pHs showed that molecular weights of the main WSP ranged from 30 to 97 kDa. The WSP was recovered by adjusting the pH to 4.0–5.0, and the functional properties of WSP were greatly affected by pH value.     

Production and Evaluation of Mexican-Style Chorizo Sausage Using Invasive Silver Carp (Hypophthalmichthys molitrix) Meat

In the United States, silver carp (Hypophthalmichthys molitrix) is classified as an invasive fish with no commercial value. The main objective of this study was to develop a Mexican-style fish chorizo sausage with silver carp meat. Four formulations (1) containing vinegar (Wet); (2) Wet plus canola oil (O) and cassava starch/soy protein isolate extenders (E); (3) dry seasoning with no vinegar (Dry); and 4) Dry plus OE were evaluated for physicochemical characteristics (proximate composition, pH value, color, cook loss, and textural hardness) and sensory acceptability using 9-point hedonic and just-about-right scales. The addition of OE did not increase (P > 0.05) physicochemical characteristics nor (P > 0.05) sensory acceptance of the chorizo. In contrast, use of DS increased (P > 0.05) the sensory acceptability. However, panelists indicated a “saltiness” perception in all four formulations. A fifth formulation was processed using DS without salt addition. Sensory acceptability increased for this new formulation (scores between 7, like moderately, and 8, like very much). In conclusion, it is possible to formulate a Mexican-style fish chorizo sausage using silver carp meat with DS and no salt. Fish chorizo has good physicochemical characteristics and sensory acceptance, demonstrating a good alternative use for this otherwise underutilized invasive fish species.     

酶法制备脱脂鱼蛋白的初步研究

采用5种酶对脱脂鲢肉进行水解制备水解鲢蛋白。脱脂鲢肉是分别采用异丙醇、正己烷、乙酸乙酯3种溶剂萃取法进行脱脂后得到。分别用木瓜蛋白酶、枯草杆菌中性蛋白酶、枯草杆菌碱性蛋白酶、胰蛋白酶和复合蛋白酶对3种脱脂鲢肉及未脱脂鲢肉进行水解。试验结果表明,乙酸乙酯对鲢肉脱脂率最高,脱脂率为96．33％。复合蛋白酶为最适酶,乙酸乙酯脱脂鱼肉为最佳底物;在最佳水僻条件下：pH6．5,温度55℃,酶量3500U／g蛋白质,底物浓度（乙酸乙酯脱脂鲢肉：水）1：5,其水解度达到最大,为44．00％。     

Study on the Change of Muscle Proteins During the Half-Dried Salt-Cured Silver Carp (Hypophthalmichthys molitrix) Processing

Changes in the muscle protein during processing of half-dried salt-cured silver carp (Hypophthalmichthys molitrix) was studied. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) assay indicated that hydrolysis of the muscle proteins took place during processing, particularly at the drying stage. Further in vitro assay on the activities of Cathepsins B and L, which are related to the degradation of the myofibrillar proteins, indicated that Cathepsins B and L still had high activity at the last stage. Total soluble nitrogen (TSN) and nonprotein nitrogen (NPN) showed significant decrease (p < 0.05) and then increased during the drying stage (p < 0.05), which may be caused by the degradation of the myofibrillar proteins and other insoluble proteins. Furthermore, the retained enzymatic activity of Cathepsins B and L may contribute to the proteolysis. Our research indicates that heat pump drying is a novel drying method that can produce the traditional flavor of dried aquatic products, and the formation of high-quality flavor may be due to the degradation of the myofibrillar proteins and water-soluble proteins.     

鲢幼鱼非疲劳贴网及姿态转换行为研究

流速是影响鱼类生存与繁衍栖息的重要因子。为了了解鱼类在中等流速区的游泳行为,探究其对水流的适应特征,利用鱼类游泳能力测定装置,以鲢(Hypophthalmichthys molitrix)幼鱼[体重(9.82±3.81) g,体长(8.56±1.11) cm)]为对象,采用递增流速法,分析了游泳过程中的非疲劳贴网行为与姿态转换行为。结果表明,在22℃水温条件下,鲢幼鱼平均相对临界游泳速度(critical swimming speed,U_(crit))相比其体长(body length,BL)为(6.00±0.93)BL/s;其非疲劳贴网速度(no-fatigue impingement speed,U_(imp))与临界游泳速度呈线性正相关,U_(crit)=1.03 U_(imp)+1.26 (R~2=0.86,P0.01);姿态转换速度(gait transition speed,U_(tran))与临界游泳速度呈线性正相关,U_(tran)=0.59 U_(crit)+1.55 (R~2=0.43,P0.01);非疲劳贴网速度与姿态转换速度呈线性正相关,U_(tran)=0.51U_(imp)+2.72 (R~2=0.41,P0.001)。在中等流速范围内(2～4 BL/s),实验鱼摆尾频率(tail beat frequency, TBF)和单次摆尾周期前进距离(stride length, SL)均随流速增加而增大。首次出现非疲劳贴网的流速为4.62 BL/s,流速增至5.08 BL/s时出现姿态转换行为。发生姿态转换后,TBF开始下降,而SL随流速增加快速增大。研究显示,鲢幼鱼非疲劳贴网行为对游泳能力和姿态转换速度有显著影响,且非疲劳贴网行为与姿态转换行为之间也存在相互影响。研究结果可为自然环境中鱼类生态行为研究、鱼类资源保护及渔业管理提供参考。     

Gelation Characteristics of Surimi Gel from Silver Carp (Hypophthalmichthys molitrix) by Application of Acid-Alkali Processes

Textural characteristics of silver carp surimi gel prepared from acid- and alkali-produced protein isolates were investigated and compared to the surimi gels derived by conventional methods. The acid-aided method showed the most efficiency to recover proteins (86.2%) in comparison to the alkaline-aided (79.8%) and conventional (76.7%) methods. In the washing of fish mince, every step resulted in reduction of sarcoplasmic protein, and consequently the myofibrillar fraction became more concentrated, as shown by the protein patterns in wash water. Some myofibrillar proteins (mainly actin and myosin) were removed along with sarcoplasmic proteins during washing, reducing yield efficiency during the conventional method of making surimi. During the pH shifting process, myosin heavy chain (MHC) was degraded during low (2.5) pH solubilization, whereas there was only a minimal loss of MHC by either hydrolysis or proteolysis during alkaline solubilization. The breaking force and breaking distance of surimi gel prepared in the pH-shifting processes were significantly (p < 0.05) greater than those of surimi gel made by conventional methods, as were expressible moisture, cohesiveness, and springiness. In conclusion, the pH-shifting technique can be considered as an efficient alternative process in recovery of greater quantities of functional protein from silver carp fillet.     

Study on Gel Properties of Silver Carp (Hypophthalmichthys molitrix) and White Croaker (Argyrosomus argentatus) Blended Surimi at Different Setting Conditions

Gel properties of blends of surimi from silver carp and white croaker set for a range of times and at different temperatures were evaluated for breaking force, breaking distance, and whiteness. Total protein content was 12% in all samples, and the concentration of white croaker surimi protein in the blends was designed at 0, 10, 20, 30, and 40%. The blended surimi had greater gel strength than either of the two types of surimi alone. Breaking force and breaking distance after setting were also significantly higher than that of the blended surimi cooked directly without setting. The blended surimi exhibited less modori than either of the two types of surimi alone heated to 50°C. The whiteness values of the blended surimi were significantly higher than that of white croaker alone. These results indicate there are advantages to be gained in utilizing surimi from freshwater silver carp in blends with surimi from marine captured white croaker which is becoming limited in supply.     

不同温度下重复疲劳运动对鲢幼鱼游泳能力及代谢率的影响

在自行设计的鱼类游泳能力测定装置中,采用流速递增法,测定了不同温度(10、15、20、25℃)条件下鲢(Hypophthalmichthys molitrix)幼鱼2次疲劳运动过程中临界游泳速度和耗氧率的变化,探究重复疲劳运动对鲢幼鱼游泳能力和活动代谢率的影响。结果表明,在10~25℃温度范围内,鲢幼鱼临界游泳速度随温度升高而呈线性增加(U_(crit,1)=3.52+0.14T,R~2=0.98,P0.05;U_(crit,2)=3.33+0.09T,R~2=0.97,P0.05),重复运动后的临界游泳速度明显小于第1次。运动最大耗氧量(MMR)和标准代谢率(SMR)均随温度升高而增加,且第1次测试的耗氧率显著高于第2次;运动后过量耗氧率(Excess post-exercise oxygen consumption,EPOC)随着温度升高而增加,与温度相关性显著(P=0.024);第2次测试疲劳后EPOC较第1次低,疲劳运动对EPOC影响不显著(P=0.36);表明适宜温度范围内,温度对游泳能力和活动代谢具有促进作用,疲劳运动对鱼类游泳能力和活动代谢不利,有一定的抑制作用。     

不同鲢密度对千岛湖沿岸池塘浮游植物群落结构的影响

为了进一步检验中营养条件下滤食性鲢（Hypophthalmichthys molitrix）的控藻效应,于2017年5-9月,在浙江省淳安县千岛湖邵家鱼种场选择8口大小、形状等各种条件基本一致的池塘,设置无鱼（CK）0 g/m3、低密度（LD）10 g/m3、中密度（MD）20 g/m3和高密度（HD）30 g/m3共计4个鲢处理组,放养的鲢体重为（61.03±3.70）g、体长为（14.21±0.27）cm,经每月3次浮游植物样品采集和观察,探究不同密度的鲢放养对浮游植物群落结构的影响。结果表明,浮游植物优势种组成在不同处理组池塘间无显著差异。双因素方差分析表明,鲢密度和月份对浮游植物密度和生物量均有显著作用,月份而非鲢密度对其多样性产生显著影响,2个因素对浮游植物生物量有而对其密度和多样性指数无交互作用。3个有鲢处理组池塘藻类总密度和蓝藻密度均有较大幅度下降,它们的蓝藻密度、中高密度组池塘藻类总密度显著低于无鱼组;中、高密度组池塘蓝藻生物量、中密度组池塘藻类总密度均显著低于无鱼组和低密度组。实验结果表明,鲢对浮游植物的抑制作用具有密度效应,随鲢放养密度和水体藻类现存量的变化而变化,鲢中等密度放养能显著遏制浮游植物现存量,密度依赖的鲢滤食量对浮游植物的抑制作用明显大于营养短路和藻类小型化对浮游植物的促进效应。     

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...     

Use of Hydrolysates from Silver Carp (Hypophthalmichthys molitrix) Head as Peptone for Vibrio anguillarum and Optimization Using Response Surface Method (RSM)

The objective of this study was to produce fish peptone (FP) from silver carp (Hypophthalmichthys molitrix) heads by Alcalase® hydrolysis in order to use for growing Vibrio anguillarum instead of the standard peptones applied in the commercial media. An optimization of the FP to be used as culture media was also carried out using the response surface method (RSM). According to the results, the degree of hydrolysis and protein percentage after 24 h was 37.68 mg/mL and 20.74%, respectively. The adjustment of the quadratic model with the experimental data was satisfactory. The analysis of variance showed a high coefficient of determination value (0.930). The results of fish protein hydrolysates also showed that fish by-products modified by enzymatic procedures can be used as low cost nitrogen sources for bacterial growth.     

Gel Properties of Surimi from Silver Carp (Hypophthalmichthys molitrix): Effects of Whey Protein Concentrate,CaCl2, and Setting Condition

The effects of setting time, whey protein concentrate (WPC), and calcium chloride (CaCl₂) on textural properties of silver carp surimi were investigated. Response surface methodology was used to evaluate and compare the effects of setting time (30–90 min), WPC (1–9% of protein ratio), and CaCl₂ (1–59 mmol/kg) on the gel strength. Models for breaking force, breaking distance, and gel strength of surimi gel were established. The maximum gel strength was achieved at the setting time of 60 min, WPC and CaCl₂ at 5% protein ratio, and 15–18 mmol/kg. CaCl₂ was the most significant factor affecting the gel strength.     

酯酶和乳酸脱氢酶在人工雌核发育鲢近交F1不同组织中的表达

采用聚丙烯酰胺水平平板电泳法研究了人工雌核发育鲢近交F1Ⅰ系、Ⅱ系、野生鲢、养殖鲢和雄鲤的肝、肾、心、眼和肌肉5种组织的酯酶(EST)和乳酸脱氢酶(LDH)。比较发现:(1)雌核发育鲢近交F1Ⅰ系、Ⅱ系和野生鲢的同工酶谱基本一致,雄鲤明显区别于鲢;(2)从酯酶图谱可发现,雌核发育近交鲢F1Ⅱ系的群体内有多态现象,肝、肾、肌肉的多态位点比例分别为0·6000、0·3333、0·5000,遗传杂合度分别为0·7485、0·6622、0·1139;(3)肝脏的乳酸脱氢酶中出现C带,且C带表现出多态性;(4)没有发现能区别鲢各群体的遗传标记。     

Fish Protein Isolates Recovered from Silver Carp (Hypophthalmichthys molitrix) By-Products Using Alkaline pH Solubilization and Precipitation

ABSTRACT

Fish protein isolates (FPI) were produced from silver carp processing by-products by means of the isoelectric solubilization-precipitation method, and the quality was evaluated. The alkali-aided process led to significantly more lipid reduction (p < 0.05) compared with the acid-aided process. Similar protein types were extracted for the acid and alkali solubilization, and most protein types can be recovered from the raw materials, as observed in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The FPI was higher in total amino acids and essential amino acids (EAAs) compared with the original by-products (p < 0.05). The alkali-aided process yielded a higher nutritional and color quality than the acidic process. Furthermore, we found that alkali-aided protein had higher oxidative stability than the acid-aided protein. Our study indicates that high-quality fish proteins can be efficiently recovered from low-value silver carp processing by-products using isoelectric solubilization/precipitation, particularly the alkali-aided process, and subsequently be used in value-added human foods.     

Effects of Heat Pump Drying Parameters on the Volatile Flavor Compounds in Silver Carp

ABSTRACT

Effects of various heat pump drying parameters (temperature, air velocity, bypass air ratio, and drying time) on the volatile compounds in silver carp (Hypophthalmichthys molitrix) were studied. These parameters determined the drying rate and influenced the formation of the volatile flavor compounds. High temperatures strongly promoted the volatile flavor compounds’ formation. Temperature increase from 5 to 35°C induced increase in the total various volatile compounds (including alcohols, aldehydes, ketones, and acids) content, total volatile basic nitrogen (TVB-N), and thiobarbituric acid-reactive substances (TBARS). However, high temperatures (> 35°C) led to many unpleasant volatile odors. Increase in the air velocity (0.35–1.65 m s^?1) and bypass ratio (0.2:1.0) led to increases in the volatile compound contents but decreases in the TVB-N and TBARS values. The TVB-N content was the lowest in all the samples when the bypass air ratio value was 0.6. The drying time had negative effects both on the generation of volatile flavor compounds and TVB-N and TBARS. We found that the optimal temperature, velocity, bypass ratio, and time for our process were 20°C, 1.65 m s^?1, 0.6, and 36 h, respectively.     

白鲢骨骼肌丝氨酸蛋白酶抑制剂的提取、纯化及其特性

从白鲢（Hypophthalmichthys molitrix）骨骼肌中分离纯化到一种丝氨酸蛋白酶抑制剂，该抑制剂的分子晕大约50kD，用PAGE-明胶电泳证明，该抑制剂对胰蛋白酶具有抑制作用；当温度超过60℃时，抑制剂的活性下降70％左右，但在pH3～11的范围内均有活性。用MTT法分析白鲢骨骼肌丝氨酸蛋白酶抑制剂对急性T细胞白血病细胞Jarkat、人骨髓瘤细胞Sp20和人骨瘤细胞MG63生长的影响，结果发现该抑制剂对以上3种肿瘤细胞的增殖都有抑制作用，而且抑制作用呈剂量依赖性。本研究旨为进一步研究白鲢骨骼肌丝氨酸蛋白酶抑制剂的纯化及其抗肿瘤作用提供科学依据。     

4种常用渔药对鲢鱼种的急性毒性试验

研究了硫酸铜、福尔马林、高锰酸钾和敌百虫4种渔药对鲢(Hypophthalmichthys molitrix)鱼种的急性毒性。结果显示:硫酸铜的24 h LC50为7.71 mg/L,48 h LC50为6.11 mg/L,安全浓度为1.15 mg/L;福尔马林的24 hLC50为48.17 mg/L,48 h LC50为36.25 mg/L,安全浓度为6.16 mg/L;高锰酸钾的24 h LC50为3.87 mg/L,48 hLC50为2.75 mg/L,安全浓度为1.74 mg/L;敌百虫的24 h LC50为11.96 mg/L,48 h LC50为9.39 mg/L,安全浓度为0.42 mg/L。结果表明,敌百虫可安全使用,硫酸铜和福尔马林需慎用,高锰酸钾不适宜在鲢鱼种的防病中使用。     

鲢肠道淀粉酶的分离纯化及部分性质研究

以鲢(Hypophthalmichthys molitrix)加工下脚料为原料,分离提纯其中的淀粉酶并对其部分性质进行了研究。结果表明经多级分离,得到了一种相对分子质量约2.15×104的淀粉酶,命名为SCIG1。SCIG1是鲢肠道淀粉酶的一种,酶活性的最适温度为30℃,最适pH5.5。