微波—红外联合加热对凡纳滨对虾品质的影响

采用微波—红外联合加热技术对凡纳滨对虾进行处理,探讨联合加热条件对对虾品质的影响,为对虾制品的研发奠定理论基础。研究分析对虾在微波—红外加热过程中中心温度的变化,及不同加热条件下虾仁的重量损失率、颜色、质构等品质变化规律。结果显示,在相同微波功率下,红外温度越低,重量损失率越大。在127、179°C红外温度条件下,硬度在200 W时最大,然后随微波功率的增大而下降,1000 W时达到最低值;在75°C下,硬度在400 W时最大。3种红外温度对弹性的影响不显著,当微波功率为400 W时,虾仁的弹性最大,微波功率提高至800 W时,虾仁的弹性明显下降,而弹性在800和1000 W间没有显著差异。在相同微波功率条件下,红外温度75°C时的黏附性与127和179°C时的显著不同。咀嚼性、内聚性在200 W时呈最大,随微波功率增大,并无显著变化。在色差方面,L*、a*、b*和ΔE与红外温度呈负相关。以上结果为联合加热技术在对虾加工中的应用奠定了一定基础。     

二次杀菌条件对凡纳滨对虾软烤虾品质的影响

通过基于栅栏效应的工艺将凡纳滨对虾加工成高水分软烤虾,对产品进行二次杀菌,测定不同杀菌条件下软烤虾的色泽、质构、p H值、感官品质,并判定是否处于商业无菌状态。结果表明,随着杀菌温度的增加,L*值、a*值与b*值均呈现下降趋势,随杀菌时间增加,L*值略有下降,a*值与b*值略有上升。杀菌温度上升,硬度、胶粘性、咀嚼性、弹性在一定范围内先上升再下降;而粘附性一直上升,内聚性一直下降但变化相对较小,最大剪切力的整体趋势也下降。杀菌时间增加,硬度、粘附性与咀嚼性升高,内聚性与最大剪切力下降,胶粘性先下降再上升,而弹性先上升再下降。软烤虾的p H值随着杀菌温度升高变化较复杂,但杀菌时间增加时p H值上升。当杀菌条件为90℃·(30 min)-1时,软烤虾的感官品质最好,并且达到商业无菌状态。     

Effect of temperature decrease on hemocyte apoptosis of the white shrimp Litopenaeus vannamei

This study investigated the effect of continuous temperature decrease on hemocyte apoptosis of the white shrimp Litopenaeus vannamei. In the stress group, water temperature decreased from 26 to 17 °C at a rate of 1 °C/h. Shrimp kept at 26 ± 0.5 °C were used as control group. Total hemocyte count (THC), reactive oxygen species (ROS) production, cytoplasmic free-Ca²⁺ (CF-Ca²⁺) concentration, mitochondrial membrane potential (MMP), apoptotic cell ratio, and caspase-3 activity of L. vannamei hemocytes were determined when water temperature decreased to 23, 20, and 17 °C, respectively. Increased ROS production in hemocytes was observed when water temperature decreased to 20 and 17 °C. Decreased THC and cellular MMP, increased CF-Ca²⁺ concentration, apoptotic cell ratio, and caspase-3 activity were shown when water temperature decreased to 17 °C. These results indicate that water temperature decrease can induce oxidative stress on shrimp hemocytes and then cause mitochondria and caspase-3 mediated hemocyte apoptosis and THC reduction, when water temperature decreased to an unconformable level.     

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.     

Decrease of Lipid Oxidation for Dried Shrimp (Acetes chinensis) Preservation Using Alkaline Lipase Hydrolysis Technology

ABSTRACT

In this study, the degreasing technology using alkaline lipase hydrolysis for Chinese dried shrimp (Acetes chinensis) was investigated, with the purpose of decreasing lipid oxidation during dried shrimp preservation. The salt, moisture, and lipid contents of the shrimp were 6.01, 32.51, and 2.95%, respectively. The optimum enzymatic hydrolysis condition for effective decrease of shrimp lipid was obtained: lipase concentration 40 U/mL, pH 10, soaking time 60 min, soaking temperature 30°C, and shrimp/liquid ratio 1:20 (w:v). Under this optimum condition, the residual lipid of the shrimp was reduced to 2.28%, and the degreasing rate reached 49%. During 30-day preservation, the thiobarbituric acid-reactive substances (TBARS) value (0.185 mg/kg of dried shrimp and 0.131 mg/kg of degreased dried shrimp at Day 30) of degreased shrimp was lower than the shrimp without degreasing, indicating alkaline lipase hydrolysis could effectively prevent lipid oxidation and inhibit oxidative rancidity during dried shrimp preservation.     

Physicochemical and Microbiological Changes in Dried Small-Spotted Catshark (Scyliorhynus canicula): Contributing to the Developing an Alternative Shark-Based Salted-Dried Seafood Product

Our aim is to contribute to the valorization and optimization of a salted-dried seafood product prepared from small-spotted catshark (Scyliorhynus canicula) akin to “litão seco,” the high-priced, traditional dried blackmouth catshark (Galeus melastomus). This work focused on studying the changes in physicochemical and microbiological parameters of S. canicula salted (for 3 h or 24 h) and dried (convection oven for 24 h or tray drier for 3 h). As expected, salting and drying reduced the water content and water activity, while chloride content in fillets increased. Also, significant but distinct changes in color, namely CIE L* and b*, were observed. Total viable counts were significantly reduced in the salted-dried shark, but the later still presented Staphylococcus aureus, though at marginally acceptable, non-hazardous levels. The abundance of yeasts was reduced by 3 log(cfu/g) in samples oven-dried for 24 h but only by 0.8 log after 3 h in the tray-drier. From our results, salted-dried S. canicula has the required physicochemical characteristics and microbiological quality to be apt for human consumption and is a suitable candidate for becoming a traditional seafood product comparable to “litão seco.”     

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.     

Equilibrium Moisture Content Isotherms of Codfish (Gadus morhua)

Industrial drying of salted fish is an extremely common practice in the Portuguese industry of codfish processing. The present study aims to obtain sorption isotherms of codfish, which will be useful in designing drying processes and prediction of storage conditions for this product. The equilibrium moisture contents (wet basis) were determined for salted codfish at 15, 18, 20, and 23^ºC at relative humidities ranging from 40 to 70%. Experiments were also carried out for fresh codfish at the temperature of 20^ºC for the same values of relative humidity. The sorption capacity of codfish decreased with an increase in temperature at constant relative humidity. Thirteen models were used to correlate the experimental data analysis of salted codfish: modified BET, Cauri, Chung-Pfost, modified Chung-Pfost, GAB, modified GAB, Halsey, modified Henderson, Kuhn, Oswin, modified Oswin, Smith, and modified Smith. Based on the mean relative percentage deviation, standard error of estimate, randomness of residual, and coefficient of determination, experimental data were well described by all the models. The equilibrium moisture content of salted codfish was best predicted using the modified GAB model, with a coefficient of determination of 0.99.     

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.     

Stability of Krill Meal,Astaxanthin, and Canthaxanthin Color in Cultured Rainbow Trout (Oncorthynchus mykiss) Fillets During Frozen Storage and Cooking

Rainbow trout were pigmented with diets containing synthetic astaxanthin, canthaxanthin, or dried krill meal to 6 mg carotenoid/Kg (wwb) flesh. Vacuum packaged frozen fillets were held at -18°C, -28°C or -80°C for 90 d, 180 d, or 90 d, thawed, and refrozen for an additional 90 d. Tristimulus color (L*,a*,b*), carotenoid concentration, fatty acid composition and TBARS were measured for raw and cooked fillets. We observed no change in pigment content or in a* values after 180 d frozen storage or following a thaw/refreeze cycle compared to fresh fish, even though a higher a* values were seen in fillets from fish fed synthetic astaxanthin or canthaxanthin after 90 d frozen storage suggesting that care should be used when interpreting tristimulus color values for grading programs.     

Anaesthetic effect of eugenol at different concentrations and temperatures on black tiger shrimp (Penaeus monodon)

The anaesthetic effects of eugenol on Penaeus monodon were investigated at the different eugenol concentrations (60, 110, 160 and 210 mg/L), water temperature (21, 26 and 31°C), air exposure time (3, 6, 9 and 12 min) and body weight (2.62 ± 0.27, 6.34 ± 0.36 and 11.43 ± 0.33 g). The anaesthesia and recovery time were recorded. The results showed that the anaesthesia time of the shrimp decreased with the increase in the eugenol concentration and water temperature, and the recovery time increased with the increase of the eugenol concentration and the decrease of water temperature. Under the same eugenol concentrations, the recovery time increased with the increase of air exposure time and body weight. Under the eugenol concentration range of 60–210 mg/L, the recovered rate was 100%. The results indicated that eugenol is a safe and efficient anaesthetic for P. monodon.     

Effect of Genetic Algorithm Optimized Solar Tunnel Dryer on the Quality Attributes of Thin-Layer Dried Fish

ABSTRACT

Studies were undertaken to establish the performance of a genetic algorithm-optimized solar tunnel dryer in drying of fish by comparing quality attributes of fish dried in the optimized solar tunnel dryer with that dried in a nonoptimized solar tunnel dryer and in open sun. A two-way analysis of variance revealed a highly significant difference between moisture ratios for the fish dried under the optimized solar tunnel dryer and the other methods (F = 53.59, F_crit,1% = 4.09). In addition, thiobarbituric acid reactive substances showed that fish dried in the optimized dryer did not develop rancidity (2.30 µg MA/kg), that dried in nonoptimized dryer approached rancid values (5.3 µg MA/kg), while open sun dried fish was slightly rancid (7.95–8.45 µg MA/kg). Further, based on total volatile base nitrogen, fish under the three drying treatments did not develop significant putrefaction. Furthermore, it took 15, 22, and 28 h to dry fish to equilibrium moisture content of 0.12 kg/kg (dry basis), for the optimized and nonoptimized solar tunnel dryers and for the open sun drying, respectively. Thus, the optimized solar tunnel dryer is superior to both nonoptimized solar tunnel dryer and open sun drying in the drying of fish.     

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.     

Effect of sorbitol on moisture transportation and textural change of fish and squid meats during curing and drying processes

SUMMARY: Atka mackerel (Am) and Japanese common squid (Sq) meats were cured in 0.5–1.5 M sorbitol solutions (pH 7.0) and dried at 30°C (relative humidity, 60%), and the effect of sorbitol on the moisture transportation and textural change during the curing and drying processes was investigated. With an increase in sorbitol permeated through samples, the moisture contents decreased by 52% (Am) and 42% (Sq) by curing in 1.5 M sorbitol solution. When the cured meats were dried, slow moisture vaporization occurred at the initial drying period, and the critical moisture content significantly decreased with an increase in the sorbitol content of the cured meats. Further, the hardening of the dried products was effectively suppressed by sorbitol curing. These effects of sorbitol would contribute to the reduction of drying time and particularly the elimination of the excess hardening of dried fish products.     

Temperature and size effects on the accuracy of estimating postlarval shrimp populations

The common practice in estimating postlarval penaeid shrimp populations for stocking ponds is volumetric subsampling with subsequent extrapolation. This procedure can lead to considerable undercounting, which, if not recognized, will result in overstocking with accompanying underfeeding and depressed growth. Postlarval blue shrimp Penaeus stylirostris counts derived from volumetric subsampling in a container of known volume and shrimp density were checked for accuracy. Counts were made of three sizes of shrimp (4, 6 and 10·5 mm total lengths) at four temperatures (18, 22, 26 and 30°C). Water temperature and shrimp size both had highly significant (p < 0·0001) effects on the mean catch, which tended to decrease with increasing shrimp sizes and water temperatures.The population estimates ranged from 100% of the actual population for 4 mm postlarvae at 18°C to 57% for 10·5 mm postlarvae at 30°C.     

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.     

Effects of food thermal treatment on growth, absorption, and assimilation efficiency of juvenile cuttlefish, Sepia officinalis

The diet of frozen grass shrimp (P. varians) was compared to similar grass shrimp that had suffered either boiling, drying at 60°C, or freeze-drying by lyophilization at −40°C. In experiment 1, cuttlefish fed the frozen shrimp were significantly larger (P < 0.05) at the end of 10 days and at the end of the experiment, compared with those fed the boiled or dried shrimp. Growth rates were also higher for cuttlefish fed the frozen shrimp, compared with the remaining two. Growth rates were also higher for cuttlefish fed the frozen shrimp, compared with the remaining two. In experiment 2, there were no differences in weight (P > 0.05) between cuttlefish fed the frozen or the freeze-dried shrimp, whereas cuttlefish fed the dried shrimp were smaller at the end of the experiment. Growth rates of cuttlefish fed the dried shrimp were lower, compared with those for cuttlefish fed the frozen and freeze-dried shrimp, with no significant differences (P > 0.05) between them. Cuttlefish fed freeze-dried and frozen shrimp showed a higher trypsin activity compared to animals fed boiled and dry (60°C) shrimp. A higher proportion of absorbed energy was channelled into biomass production in animals fed frozen and freeze-dried shrimp (56% and 43%, respectively) than for animals fed oven-dried (60°C) or boiled shrimp. The heat treatment suffered by the shrimp, either dry or wet, negatively affected diet quality, probably due to denaturation, and loss (by boiling) of proteins and amino acids. Additionally, the heating processes may have oxidized the lipids to a large extent, contributing to the loss of the polar lipids (polyunsaturated fatty acids), which are essential for cephalopods as for other organisms. Freeze-drying by lyophilization (negative temperatures) did not affect the nutritional quality of the shrimp.     

Effect of high water temperature on the survival, moulting and food consumption of Penaeus (Marsupenaeus) japonicus (Bate, 1888)

The kuruma shrimp, Penaeus (Marsupenaeus) japonicus (Bate, 1888), is a valuable aquaculture species in Queensland, Australia. The shrimp is supplied live to the Japanese market and must survive emersed transport for up to 36 h. In-transit mortality after harvest from high water temperatures (> 30 °C) has been reported by the industry, and a knowledge of the effects of high water temperature may provide important information for producers on grow-out management, timing of production and farm location. Experiments were conducted to determine the effect of high water temperature on survival, moulting and food consumption in P. japonicus. Replicated groups of 15.6 ± 0.2 g shrimp were acclimated and exposed to five temperatures, between 28 and 36 °C, for up to 28 days. Mortality was highest at 36 °C and equally lowest between 28 °C and 32 °C. Intermoult period was not significantly different for temperatures between 28 and 32 °C (19.8–15.5 days) but was significantly greater above 32 °C (27.4 days at 34 °C and > 104 days at 36 °C). There was evidence of moulting synchrony at 28 °C. Mean daily food consumption was highest at 32 °C at 2.34% of body weight, but decreased to 1.56% at 28 °C and 1.33% at 36 °C. Over the range of water temperatures examined, survival, moulting rate and food consumption were highest at 32 °C.