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.     

即食海参加工工艺的研究

传统工艺加工的海参干制品烹调时需要水发,本试验拟解决由于干制品给食用带来的不便,以冷鲜海参作为研发对象,从原料的特性和功能入手,利用海参特殊的营养结构和组分等特点,采用了科学合理的加工技术,对传统的海参加工方法进行了全面的技术改造,通过正交试验对焖煮、浸渍等关键技术的探讨,成功的研制出即食海参间断式加热焖制工艺,且焖制水温为90℃、焖制时间为4 h、循环次数为3次,加工的成品即食海参不但肉质富有弹性、色泽较好、风味独特,而且最大程度地减少了营养成分损失。     

Changes in the Chemical Characteristics of Gulbi,Salted and Dried Yellow Corvenia,During Drying at Different Temperatures

A few chemical characteristics of Gulbi, a traditional Korean seafood prepared from salted and dried Yellow corvenia (Pseudosciaena manchurica), were investigated during drying at different temperatures. When Gulbi was manufactured by sun-drying (the control), it had the highest thiobarbituric acid reactive substances (TBARS) and volatile basic nitrogen (VBN) values. They increased with increasing drying time at all temperatures in the hot-air drier. The TBARS value of Gulbi was lower when dried at 30 and 35°C than at 40°C and the control. The VBN of the control was higher than that of hot-air dried Gulbi at 30 and 35°C and lower than that of hot-air dried Gulbi at 40°C. The control had a VBN value of 20.8 ± 0.07% and the hot-air dried at 30°C, 18.0 ± 0.06; at 35°C, 18.6 ± 0.06; at 40°C, 23.8 ± 0.08 (p < 0.05), respectively. The salt content of the control and Gulbi dried at 30, 35, and 40°C were 22.9 ± 0.07%, 17.7 ± 0.06%, 18.0 ± 0.06%, and 24.3 ± 0.08%, respectively. The amino nitrogen content was much lower: 63.1 ± 0.80 mg/100 g and 65.5 ± 0.14 mg/100 g at 30 and 35°C than 78.3 ± 0.21 mg/100 g at 40°C. The results of this study also indicate that the Gulbi dried at 30 and 35°C had better chemical characteristics than those dried at 40°C when using hot-air drying and sun drying.     

Effect of Different Thawing Methods and Multiple Freeze-Thaw Cycles on the Quality of Common Carp (Cyprinus carpio)

The effect of different thawing methods—running water, microwave, slack water (25°C), air (25°C), and refrigerator (4°C)—and multiple freeze-thaw cycles (0, 1, 3, and 5) on the quality of common carp were investigated. Microwave thawing showed the lowest score for sensory assessment and the highest cooking loss (p < 0.05), while 4°C refrigerator thawing showed less thawing loss and cooking loss but required the longest thawing time. Ca²⁺-ATPase activity and sulfhydryl content of air thawing were lower (p < 0.05), while no significant differences were observed among other thawing methods. Water loss and the thiobarbituric acid reactive substances (TBARS) value increased (p < 0.05) when freeze-thaw cycles increased. The sensory scores and hardness decreased significantly when the freeze-thaw cycles increased (p < 0.05). A significant decrease (p < 0.05) was observed in salt-extractable protein content after five freeze-thaw cycles. Different thawing methods affected the quality of common carp. Frozen common carp subjected to freeze-thaw cycles resulted in accelerated lipid and protein oxidation and caused mechanical damage to muscle tissues.     

大型海藻干燥技术研究进展

干燥是海藻储存、加工、生产的重要方法之一,不同的干燥方式对海藻脱水效率、能耗和品质影响很大。本文对藻类传统干燥和新型干燥技术的特点、研究及应用现状进行了分析。研究表明,太阳能干燥技术能够充分做到干燥过程中绿色、环保,与空气热泵构成组合干燥模式,可解决太阳能不连续的问题;过热蒸汽干燥效率高、能耗低,藻类干燥后复水性好;真空冷冻干燥产品品质好,能最大限度保持藻类的营养和功能性成分;远红外加热技术对海带进行干燥,与同风速的热风干燥相比,可显著缩短干燥时间,降低能耗;微波真空干燥技术干燥江蓠,在保持品质的基础上干燥时间较热风干燥减少70%。本文同时对藻类干燥技术与设备存在的问题进行了总结,对国内藻类干燥技术及装备的发展趋势进行了展望并提出了措施与建议。     

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.     

Growth and oxygen consumption of the juvenile sea cucumber Apostichopus japonicus (Selenka) at constant and fluctuating water temperatures

The effects of thermal amplitudes of diel fluctuating temperature on growth and oxygen consumption of the juvenile sea cucumber Apostichopus japonicus (Selenka) were studied at the average temperatures of 15 and 18°C with three diel different fluctuating amplitudes of ±2, ±4 and ±6°C. The optimum thermal amplitudes for growth of the juvenile sea cucumber at the sizes of this experiment, at average temperatures of 15 and 18°C, were estimated to be ±1.38 and ±1.67°C respectively. In the constant temperature regimes, the growth rate at 15°C was higher than that at 18°C. However, the growth rate at 18±2°C was higher than that at 15±2°C. The results from this study suggested that fluctuating temperatures enhanced the optimum temperature for the growth of sea cucumbers compared with that at constant temperatures. Therefore, accurate predictions of the optimum temperature of sea cucumbers in the natural environment, in which water temperatures fluctuate daily and seasonally, should be made from data obtained at fluctuating temperatures.     

Physical and Sensory Properties of Electrohydrodynamic (EHD) Dried Scallop Muscle

Electrohydrodynamic (EHD) drying was tested as an improved dehydration method for scallop muscle. The scallop muscle was dried in an EHD drying system at 15°C, in an oven at 60°C, and in ambient air at 15°C. The energy consumption of EHD and oven drying, as well as the shrinkage rate, water absorption, solid loss, and sensory properties such as color and anti-crushing durability of the dried scallop muscle were measured. Results showed that the drying rate of scallop muscle significantly improved using the EHD drying system. Under a 45 kV voltage, the drying rate of EHD is 7 times higher compared with that of air drying in the 1st h. Compared with oven drying, EHD drying was more efficient in terms of energy saving. Furthermore, EHD drying cost only 28.67% of the electric energy required for oven drying. The dried scallop muscle by EHD had better sensory qualities and higher anti-crushing durability. EHD drying is very advantageous and can be used as a substitute to the traditional drying method.     

南极磷虾体内主要营养活性物质在热处理过程中的流向

虾粉是南极磷虾最主要的加工产品之一,加工过程中,热处理会造成营养物质的流失和活性物质的破坏,是决定虾粉品质最主要的影响因素。为了掌握虾粉加工过程中主要物质的变化情况及流向路径,通过测定蒸煮、干燥两个涉及到热处理的关键工序中水分、灰分、蛋白质、脂质等主要营养物质的含量变化及脂肪酸、虾青素等功能成分的损失情况,分析各主要物质的流向路径及变化原因。结果显示：水分在蒸煮过程中流失8.49%,干燥过程中水分流失63.5%,大多以蒸发的形式流失;蛋白质在蒸煮过程中流失1.12%,其中流向蒸煮液0.87%,流失部分主要为水溶性蛋白,干燥过程流失6.05%;脂质在蒸煮、干燥过程中分别减少1.11%和1.61%,进一步分析其脂肪酸组成,发现多不饱和脂肪酸含量由45.57%降低至43.65%,其中EPA相对含量在蒸煮、干燥过程中分别减少0.41%和1.16%,DHA相对含量在蒸煮过程中变化不大,干燥过程中减少0.68%;虾青素是热敏性物质,受热处理的影响,在蒸煮、干燥过程中分别减少29.4和58.6mg/kg;灰分含量在蒸煮、干燥过程中分别减少2.85%和0.85%;结果表明蒸煮过程损失的主要物质为蒸煮液中的可溶性物质及少部分的热敏性物质,干燥过程主要造成水分的蒸发和虾青素等热敏性物质的破坏。研究初步掌握了南极磷虾虾粉加工过程中主要物质的含量变化与流向路径,分析了变化原因及主要影响因素,并讨论提出了减少物质流失的方案,可为后续南极磷虾粉加工工艺流程和参数的优化提供理论依据,对提高虾粉品质、促进南极磷虾资源高质化利用具有非常重要的意义。     

Convective Drying Kinetics and Physical Properties of Silver Carp (Hypophthalmichthys molitrix) Fillets

The aim of this work was to investigate drying kinetics of silver carp fillets at the temperatures of 40, 50, 60, and 70°C for two air velocities (0.5 and 1.5 m/s) and to evaluate the effect of drying temperature on the physical properties of the products. From regression analysis of the experimental data, a Two-term model was found to adequately predict the drying process at all conditions tested. Effective moisture diffusivities (D_eff) ranged between 2.47?×?10^?10 m²/s and 5.98?×?10^?10m²/s and increased with temperature and air velocity. Rehydration ratio, hardness, and springiness were significantly affected by drying temperature. Color parameters, except b*, showed no dependence on temperature.     

Hot water immersion lowers survival,shell growth rate and lysosomal membrane stability of oysters Crassostrea virginica (Gmelin)

This study compares the effect of two anti‐fouling treatments, hot water immersion (15 s at 60°C) and air drying (72 h) on the physiological status of the Eastern oyster Crassostrea virginica. The negative impact of hot water immersion was greater than that of air drying, but varied depending on the initial size of the oysters (40 vs. 60 mm shell height) and the time of the year (June vs. August). Groups treated with hot water exhibited a higher proportion of haemocytes with destabilized lysosomal membranes (HDLM; 47.5 ± 3.1%) than those exposed to air drying (37.5 ± 2.9%). This suggests that the oyster immunocompetency may be lowered by hot water immersion. Overall, the large oysters had lower HDLM values (32.9 ± 3.5%) than the small individuals in June (45.7 ± 2.8%) but similar values in August (46.6 ± 3.5%). Small oysters subjected to hot water immersion in June exhibited a 50% reduction in shell growth and a 50% mortality rate after one month. Our results indicate that air drying is more suitable than hot water immersion as an anti‐fouling treatment for <45 mm oysters.     

海参在加工过程中的组分与食品结构变化

海参是我国传统的滋补海洋食品与重要的经济水产品。海参极易自溶的食品原料学特性决定了绝大部分海参原料需要经过加工才能进入市场流通与消费,使得加工成为海参产业链的关键环节。明确海参在加工过程中的组分与食品结构变化,是阐释海参产品品质形成机理的核心,对设计开发海参高品质加工新技术具有重要的理论指导意义,是关乎海参产业发展的关键科学问题。本文概述了海参的组分及食品结构特征,归纳了海参的关键加工环节,以此为背景着重梳理了海参在水煮、干燥、复水、酶解、即食海参加工等过程中组分及食品结构变化的相关研究进展,提出了深入研究的建议,以期加速上述科学问题的解答、推动海参产业的高质量发展。     

Effects of dietary protein levels on the activity of the digestive enzyme of albino and normal Apostichopus japonicus (Selenka)

We evaluated the effects of different proportions of dietary protein (5%, 10%, 15%, 20%, 25% and 30% protein) on the activity of digestive enzymes of normal and albino Apostichopus japonicus. The experimental diets were fed for 60 days, the optimal conditions for digestive enzyme activity in sea cucumbers were studied. The optimal temperature for protease was 29.3°C and the optimal pH was 1.8. The optimal temperature for amylase was 34.3°C and the optimal pH was 6.7. The optimal temperature for cellulase was 56°C and the optimal pH was 5.9. The activity of intestinal protease increased at first and then decreased as the proportion of dietary protein increased, reaching the maximum when the proportion of protein was 19.7%. The activity of protease in the intestine of normal sea cucumber was significantly lower than that of albino sea cucumber, and the activity of amylase was significantly higher than that of albino sea cucumber. This study is expected to provide a basis for further explaining the ecological difference of albino and normal A. japonicus.     

Drying Kinetics and Quality Characteristics of Indian Mackerel (Rastrelliger kanagurta) in Solar–Electrical Hybrid Dryer

The aim of the study was to investigate the drying kinetics and quality characteristics of Indian mackerel dried under solar–electrical hybrid dryer (S-EHD). Fresh Indian mackerel fishes (Rastrelliger kanagurta) were cleaned, cut into butterfly fillets, and salted overnight using a dry salting method (salt-to-fish ratio, 1:3). The salted mackerel was dried in a S-EHD at the air temperature of 45–55°C, relative humidity of 47–62%, and air velocity of 0.60–0.80 m/s. Open sun drying (OSD) of salted Indian mackerel was conducted to compare with S-EHD. The moisture content of the salted mackerel (61.5% w.b.) was reduced to 31.8% (w.b.) under S-EHD and 30.25% (w.b) under OSD in 8 and 32 h, respectively. The drying rate curve showed that mackerel drying occurred under falling-rate drying period in both the drying methods. A drying efficiency of 23.81% was observed for salted Indian mackerel drying under S-EHD. Diffusion approach and two-term models were selected to accurately predict the drying behavior of mackerel under S-EHD and OSD, respectively. Total volatile base nitrogen (TVB-N), trimethylamine, and thiobarbituric acid analysis of dried samples revealed that the mackerel dried under S-EHD was better than OSD. In the sensory analysis, samples dried under S-EHD recorded highest overall acceptability score.     

Lipid Hydrolysis and Oxidation of Mackerel (Scomber scombrus) Mince

Atlantic mackerel was stored at refrigeration or frozen temperatures under vacuum or in air with various treatments to determine lipid hydrolysis and oxidation in the fish muscle. Lipid oxidation in the fish minces occurred continually as long as the samples were exposed to air independent of hydrolytic activity which was deactivated or retarded by cooking the sample or by lowering the storage temperature (-40°C). Lipid oxidation was observed not only in the free fatty acids, but also in the triacylglycerides and the phospholipids extracted from mackerel mince.     

The Effect of Cooking Conditions on Aluminum Concentrations of Seafood,Cooked in Aluminum Foil

ABSTRACT

Sea bass was wrapped in aluminum foil, then baked, grilled, or pan-broiled at 200°C for 20 min to determine the possible effect of cooking conditions on aluminum leaching. Negligible increase (p >0.05) in aluminum concentration was observed after cooking. The use of different cooking methods did not result in different levels of aluminum leaching from the foil. The aluminum leaching in whole sea bass, mussels, and shrimp was compared with that of skinned/shelled samples after baking in foil, and no significant difference (p?0.05) was determined between them. There was no barrier effect of skin or shell on aluminum leaching from aluminum foil during baking. For all trials, aluminum intake was well below the tolerable weekly intake value. The target hazard quotient (THQ) was below 1, indicating insignificant health risk. Negligible leaching of aluminum could be associated with the high-protein, non-acidic nature of seafood, as well as the absence of salt or organic acid during cooking.     

Comparison of Postmortem Changes in Blunt-Snout Bream (Megalobrama amblycephala) During Short-Term Storage at Chilled and Partial Freezing Temperatures

In order to obtain more information about the consumption and process of blunt-snout bream, this study investigated postmortem changes of pH, cooking loss, texture properties (hardness, cohesiveness, springiness, and gumminess), and adenosine triphosphate (ATP)-related compounds in blunt-snout bream during short-term storage at 4 and ?3°C. The pH value declined quickly within 12 h postmortem, and those samples stored at ?3°C were lower than 4°C. High values of cooking loss occurred within 2–4 h postmortem, with maximum values of 20.94% (4°C) and 27.64% (?3°C), respectively. The cooking loss rapidly decreased to 13.59% (4°C) and 17.62% (?3°C) at 8 h postmortem, respectively. Texture properties (hardness, cohesiveness, springiness, and gumminess) decreased with storage time at both temperatures. Fish stored at ?3°C had a higher level of inosine monophosphate (IMP) compared with 4°C and was more than 15 μmol g^?1 during 8–24 h postmortem. The overall results indicated that it is better to preserve blunt-snout bream at ?3°C for short-term storage and utilize the fish within 8–24 h postmortem.     

Combined effects of acute thermal and hypo-osmotic stresses on osmolality and hsp70, hsp90 and sod expression in the sea cucumber Apostichopus japonicus Selenka

The combined effects of acute temperature and salinity on osmolality, expressions of heat shock proteins mRNA (hsp70, hsp90a and hsp90b) and superoxide dismutase mRNA (sod) were investigated in the sea cucumber Apostichopus japonicus Selenka. There were 12 treatments (combinations of temperature at 16, 20, 24 and 28 °C and salinity at 22, 27 and 32 ppt). In low salinity environments, the osmolality of the sea cucumber’s coelomic fluid decreased immediately and reached osmotic balance within 6 h. The decline of osmolality after 2 h of hypo-osmotic stress was faster at high temperatures (28 °C) than that at low temperatures (16 and 20 °C). Cellular level stress was indicated by up-regulation of hsp70, hsp90s and sod mRNA, and the maximal expression of all genes occurred at 6 h after stresses. The up-regulation of hsps and sod mRNA indicated the emergence of protein denaturation and oxidative damage and also suggested an increase in energy consumption at high temperature and low salinity. These results indicated that high temperature and low salinity could change biochemical pathways and energy budgets and then potentially impair the osmoregulation of the sea cucumber. Therefore, effective ways should be taken (e.g., draining off the upper freshwater, exchanging water and adding man-made sea water) to prevent the damage to sea cucumber culture caused by low salinity induced by rainstorms, especially at high temperature.     

Purification and characterization of a cysteine-like protease from the body wall of the sea cucumber <Emphasis Type="Italic">Stichopus japonicus</Emphasis>

The sea cucumber (Stichopus japonicus) is able to undergo autolysis in response to a variety of environmental and mechanical cues. Within the framework of a long-term study of this phenomenon we have purified a protease from the body wall of the sea cucumber by means of ion-exchange chromatography with DE-52 cellulose and gel filtration chromatography with Sephadex G-100. The final enzyme preparation was nearly homogeneous on polyacrylamide gel electrophoresis, and its molecular weight was estimated to be approximately 35.5 kDa. The purified enzyme exhibited a maximum activity for the hydrolysis of casein at pH 7.0 and 50°C and a remarkable stability at pH 4.0–7.0 and 40–60°C. Based on the inhibition and activation profiles obtained with numerous specific protease inhibitors and an activator, the protease purified from the body wall of the sea cucumber was defined to be a cysteine-like protease.