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.     

Setting the Global Context in Discovery and Transformation of Seafood Products

ABSTRACT

The effects of sun drying at ambient temperature in the range of 24°C to 32°C; artificial drying at 35°C, 45°C, or 55°C; or artificial drying at 45°C after treatment with 10% brine, 20% brine, saturated (36%) brine, or dry salt at 28°C for 16 hours on the physical characteristics of the final dried Bombay duck (Harpodon neherius) were studied. Unsalted sundried fish was found unacceptable. Dry salting was more efficient in reducing the moisture level in fish than brining, but was found unsuitable by the panelists due the appearance of a powdered salt crust as the fish dries up. Bombay duck treated with 20% sodium chloride solution, artificially dried at 45°C, and kept in sealed polyethylene pouches was judged superior after sensory evaluation compared to unsalted sundried Bombay duck or unsalted artificial dried Bombay duck at 35°C, 45°C, and 55°C, or artificial dried samples at 45°C after treatment with 10% brine, saturated (36%) brine or dry salt, and kept in sealed polyethylene pouches, respectively, during storage.     

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.     

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.     

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 drying on the viability of the probiotic bacterium Lactobacillus plantarum Lab9 (CPQBA 144‐09 DRM 03) impregnated in the feed for tilapia (Oreochromis sp.)

Drying experiments were conducted at different temperatures and air flux velocities to determine the proper drying conditions for reducing moisture in commercial fish feed impregnated with probiotic lactic acid bacteria and to assess the effect on bacteria viability over time. At temperatures of 45°C, the drying time was shorter, without the air flux velocity under study having a relevant influence. The drying conditions influenced the viability of the bacteria in the feed; the least loss of viability was obtained with a velocity of 0.8 m s^?1 and a temperature of 45°C during 15 min. Using these drying conditions, 5 kg of feed was dried and stored for a month at temperature of 26°C and relative humidity of 75%. The viability of the bacteria and the moisture of the feed were measured every 3 days during the storage period. Loss of viability followed first order kinetics, with a constant k of 0.112 days^?1. Thus, the viability of the bacteria in the feed is less than 10⁶ CFU g^?1 after 43 days.     

Development of Intermediate Moisture Fish Patties from Minced Rockfish Meat (Sebastes sp.)

Abstract

An Intermediate Moisture (IM) fish patty was formulated from rockfish mince (85.7%), sorbitol (6.0%), soy protein isolate (2.0%), tapioca starch (2.0%), chicken bouillon (1.3%), refined salt (2.5%), and dried seasonings (0.5%). The mixture was dehydrated at 40 °C for 10 h and vacuum packaged. The dried product had a moisture content of 33% and a water activity of 0.82. The desorption isotherm was sigmoid in shape indicating water activity of the product at ambient temperature in the Philippines would remain stable. Seasonings were added to improve the taste and possibly the stability of the product. Sorbitol addition improved the texture, as judged by a sensory panel, as well as the rehydration index of the patties. Humectat and seasonings improved the overall acceptability of the patties by a sensory panel. Product was prepared with and without preservatives (potassium sor-bate and TBHQ), dehydrated at 40 °C for 10 h, vacuum packed and held at 38°C or ?20°C for two months. Moisture content, water activity, pH, rehydration index, TEA value, Hunter-Gardner color, texture profile, amino acid composition, sensory properties and microbial growth were determined at storage intervals. Instrumental and sensory tests showed no significant differences (p < 0.05) among samples stored with or without preservative and at ?20°C vs. 38°C.     

包装方式对日本鳀鱼干品质特性的影响

[目的]为探究不同包装对丁香鱼干常温贮藏期间的品质特性影响,[方法] 以空气包装为对照,与真空包装、气调包装和CO2包装做比较,测定贮藏过程中菌落总数、TVB-N、POV、TBA、色差、挥发性风味成分及感官评分的变化。[结果]结果显示,真空、气调、CO2三种包装均能有效抑制丁香鱼干微生物生长,常温25 ℃贮藏8 d后,真空包装组样品TVB-N、POV和TBA值分别较空气包装组降低47.08%、4.13%和25.49%,并且真空包装组样品在减缓样品色泽变化、保护肌纤维结构完整性、保留挥发性风味成分和保持感官特性方面均具有较佳效果,确定了真空包装为丁香鱼干的最佳包装方式。基于Arhenius方程建立了丁香鱼干货架期预测模型,25 ℃和35 ℃下真空包装丁香鱼干的货架期分别为6.07和3.23 d。[意义]本研究成果可为丁香鱼干常温物流过程中的品质控制提供理论依据。     

鲍鱼冷风干燥和自然晾晒试验的比较分析

研究皱纹盘鲍(Haliotis discus hannai Ino)在冷风干燥和自然晾晒两种干燥方式下的干燥速率、色泽、酸性粘多糖和总糖含量,以及微观结构变化的差异,并进行分析比较。在实验室内采用冷风干燥试验机和自然晾晒方式进行鲍鱼干燥试验。结果显示:当鲍鱼样品干基含水率从238%下降到16%以下时,冷风干燥所需时间约为122 h,是自然晾晒的70%;至干燥完成时冷风干燥鲍鱼多糖含量高于自然晾晒样品;冷风干燥样品通透性明显优于晾晒样品;两种干燥样品的微观结构差异性不明显。综合分析得出,与自然晾晒相比,冷风干燥方式具有干燥时间短,干燥过程易于控制,品质和卫生条件好,适合工业化生产等优点,是一种较佳的鲍鱼干制方法。     

On the relationship between low winter temperatures and mortality of juvenile scallops, Pecten maximus L., cultured in western Norway

The mortality of juvenile scallops (Pecten maximus L.) cultured at two densities at 8‐ and 15‐m depth was investigated at 17 trial locations along the western Norwegian coast between latitudes 58 and 65°N. During the winter of 1995/1996, scallops suffered high mortality at many sites. The results show a clear relationship between minimum temperature recorded on the sites and scallop mortality. All the scallops died at sites where minimum temperatures were lower than 2°C, while a mortality rate below 30% was only obtained at locations where the minimum temperature was 4–5°C. At temperatures between 2 and 4°C, mortality was intermediate, ranging from 52% to 100%. There were no mortality differences between culture densities, while a significantly higher mortality at 8‐ than at 15‐m depth was shown for two of the four sites with a total mean mortality lower than 30%. The results are discussed in relation to low‐temperature conditions along the Norwegian coast to suggest risk assessments for site selection in scallop culture.     

Biochemical changes in oyster tissues and hemolymph during long-term air exposure

The Pacific oyster Crassostrea gigas is a sessile bivalve that inhabits the intertidal zone and therefore frequently exposed to air during the tidal cycle. It is highly adaptive to hypoxic conditions. We have studied the physiological state of oysters during long-term exposure to air. The oysters became hypoxic when exposed to air or hypoxic seawater. The 50% lethal time of oysters exposed to air at 4, 15 and 20°C was 47.8, 15.9 and 12.2 days, respectively. The hemolymph pH decreased by day 3; however, it showed a slight increase by day 5 at both 4 and 20°C. The adenylate energy charge (AEC) values decreased rapidly on the first day of air exposure in the adductor muscle, mantle, gill and body trunk, and these decreases were accompanied by decreases in ATP concentrations and increases in AMP concentrations. The AEC values in all of the tissues had fallen to below 30% by day 50 of air exposure at 4°C. These data suggest that the energy state of oysters deteriorates rapidly with air exposure. Consequently, AEC values may be useful indices of the physiological state of the oyster during long-term exposure to air.     

Substitution of fish meal with raw or treated cowpea (Vigna unguiculata L Walp,IT86‐D719) meal in diets for Nile tilapia (Oreochromis niloticus L.) fry

Two feeding experiments were carried out to evaluate the effect of partial substitution of fish meal (FM) with raw or heat‐treated cowpea Vigna unguiculata L. Walp var. IT86‐D719 seeds on growth performance, digestibility and pancreas tissue in Nile tilapia (Oreochromis niloticus L.) fry. Experiment 1 involved six isonitrogenous and isocaloric diets: four containing different concentrations of raw, whole cowpea meal (protein basis), a positive control with FM as sole protein source and a negative with cowpea meal as sole protein source. Substitution at up to 200 g kg^?1 had no significant effect on production parameters, although growth was negatively affected in the negative control because of seed antinutritional factor content. Experiment 2 evaluated the effect of heat treatment (oven drying at 48 °C; hot air drying at 70 °C; or autoclaving at 119 °C) and/or seed dehulling using diets containing 200 g kg^?1 cowpea meal presoaked in water. Only autoclaving eliminated trypsin inhibitor and lectin contents, independent of dehulling. Histological analysis indicated no histological changes in pancreas tissue. Raw or treated cowpea meal can replace FM in tilapia fingerling diets at up to 200 g kg^?1 protein content without significantly affecting productive parameters or pancreas tissue.     

Histamine formation in flying fish contaminated with <Emphasis Type="Italic">Staphylococcus xylosus</Emphasis>

Histamine is the main causative agent of scombroid poisoning. However, unlike scombroid fish, histamine poisoning due to consumption of flying fish has never been reported. In this study, the white muscle of flying fish had high levels of free histidine at approximately 423.9 mg/100 g, and was inoculated with Staphylococcus xylosus Q2 isolated from dried flying fish at 5.0 log CFU/g and stored at ?20 to 35°C to investigate histamine-related quality. The histamine contents quickly increased to higher than 50 mg/100 g in samples stored at 25 and 35°C within 12 h as well as stored at 15°C within 48 h. However, bacterial growth and histamine formation were controlled by cold storage of the samples at 4°C or below. Once the frozen flying fish samples stored at ?20°C for 2 months were thawed and stored at 25°C after 24 h, histamine started to accumulate rapidly (>50 mg/100 g of fish). Therefore, flying fish muscle was a good substrate for histamine formation by bacterial histidine decarboxylation at elevated temperatures (>15°C) when it is contaminated with S. xylosus. In conclusion, since the improperly contaminated flying fish muscle with S. xylosus could lead to production of hazardous levels of histamine over time when stored at temperatures >15°C, the flying fish should be stored below 4 °C or below to control proliferation of S. xylosus, and TVBN and histamine production.     

Role of sorbitol in manufacturing dried seafood from heated squid meat

SUMMARY: Japanese common squid meat was heat-treated at 80°C for 1 min, cured with 1.0 M sorbitol solution (pH 7.0) at 4°C for 18 h, and dried further at 30°C (60% relative humidity) for 16 h. Osmotic dehydration during the sorbitol curing process and slow moisture vaporization at the initial drying period were observed regardless of the heat denaturation of muscle protein. Simultaneously, lowering the amount of moisture vaporized in the falling rate of the drying period caused a shortening of the total drying time. Furthermore, the shear force of the dried product from heat-treated meat was kept at a lower value by sorbitol curing, although the suppression effect of sorbitol on the hardening of dried meat was lost by protein denaturation. These results are useful for understanding the role of sorbitol in reducing drying time and in eliminating excess hardening of dried squid products.     

Influence of water temperature on food intake,food efficiency and gross composition of juvenile sea bass,Dicentrarchus labrax

The optimum ration in relation to water temperature has been determined for juvenile sea bass (Dicentrarchus labrax). Fish were reared at 15 and 20°C. The spontaneous food intake was positively related to temperature. Four daily rations were tested at both temperatures. The optimum rations were 1.7% at 20°C and 1.2% at 15°C for fish weighing 20–30 g. The influence of temperature on growth rate, body composition and food conversion was studied. Increasing the temperature improved growth rate and gross conversion efficiency but not gross protein efficiency. The results are discussed in terms of energy utilization.     

The effect of size on the response of Pacific oysters (<Emphasis Type="Italic">Crassostrea gigas</Emphasis>) to changes in water temperature and air exposure

To further improve the technology used in Pacific oyster farming, information is required on the response of different sized and aged oysters to various environmental changes. In this study a neutral red retention (NRR) assay was used to investigate the effects of size and age on the response of Pacific oysters to changes in water temperature and their recovery after exposure to different air temperatures. Results from moving oysters directly between water temperatures of 5°C and 15°C, 10°C and 20°C and 15°C and 25°C demonstrated that different water temperature change affect the lysosomal membrane integrity differently. The NRR times of large and small oysters transferred directly between 10°C and 20°C initially decreased significantly, and then increased to levels corresponding to the new temperature. In addition, NRR times in large oysters responded at a significantly slower rate than small oysters when they were transferred from 5°C and 25°C to 15°C water and between 10°C and 20°C water. Results from the air exposure experiments showed that, after exposure to air temperatures of 5°C, 15°C or 25°C, the lysosomal membrane integrity of large oysters recovered at a slower rate in 15°C water compared to small oysters. It therefore appears necessary to develop different management strategies for large (old) and small (young) oysters. Results from this and previous research also indicate that the NRR assay could potentially be used to develop a model to monitor and predict the performance of oysters on farms.     

Effect of temperature and relative humidity on the tolerance of the Japanese clam, Ruditapes philippinarum (Adams & Reeve), to air exposure

Laboratory studies showed that higher relative humidity (RH) and lower air temperature increase the tolerance of the Japanese clam, Ruditapes philippinarum (Adams & Reeve), to exposure. Aerial respiration of the clam was also measured. At high RH, the exposure time which gave 50% survival (LT₅₀) was 1.97 and 1.75 times longer than in low RH at air temperatures of 15 and 25 °C, respectively. At 15 °C, all clams previously acclimatized at 15 °C survived for 58 h at low RH and 102 h at high RH. These differences can potentially be exploited to improve the shipment of clams. The aerial respiration experiment showed that the increase of the oxygen consumption rate at 25 °C was greater than that at 15 °C, following an increase in exposure time. The aerial respiration rates of the clams were ≈ 41.6% and 50.0% of those in water at 25 and 15 °C, respectively. The survival of the clams in air was dependent on aerobic rather than anaerobic respiration.     

不同干燥方式对封鳊鱼品质的影响

为探明不同干燥方式对封鳊鱼品质及鱼肉理化性质的影响,试验采用自然、冷风、冷冻、冷风—热风联合和热泵5种干燥方式对封鳊鱼进行干燥,研究不同干燥方式对鳊鱼质量损失、干燥速率、硫代巴比妥酸值、挥发性盐基总氮、水分活度、复水率、质构特性和微观结构的影响。试验结果表明,自然干燥的干燥速率低、鱼肉复水率差、氧化最严重、腐败程度较高,但弹性和咀嚼性较好;冷冻干燥的干燥速率最快,鱼肉复水率最高,氧化和腐败程度最低,但弹性和咀嚼性差;冷风干燥的干燥速率低,但鱼肉复水率较好,仅低于冷冻干燥,氧化和腐败程度也仅高于冷冻干燥,且弹性和咀嚼性最好;热泵干燥的干燥速率较高,但鱼肉复水率低、氧化和腐败程度均较高、质构特性较差;联合干燥的干燥速率较快,但鱼肉复水率最低、腐败最严重、质构特性差。     

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.     

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.