Effect of heating on physical properties and microstructure of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) meats

Effects of heating on cooking loss, texture, colour and microstructure of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) meats from different parts were evaluated. Cooking loss increased sharply when the samples were heated for longer time, particularly more than 1 min (P < 0.05). Among all parts, tail part of both shrimps had the highest cooking loss. The shear force of all samples increased markedly when the samples were heated for longer time, especially more than 0.5 min (P < 0.05). Black tiger shrimp and white shrimp meats had the slight differences in shear force either before or after heating. L*, a* and b*‐values increased when heating time increased up to 1 min (P < 0.05). Similar microstructures between raw meats of black tiger shrimp and white shrimp were found. Cooked meats of both species had more compact fibre arrangement with the shrinkage of sarcomere, compared with raw samples. Generally, tail portion showed the denser structure than other parts.     

Importance of conformation for the IgE reactivity of sarcoplasmic calcium-binding protein from the black tiger shrimp Penaeus monodon

Sarcoplasmic calcium-binding protein (SCP) is an EF-hand Ca²⁺-binding protein recently identified as a new crustacean allergen. Some EF-hand Ca²⁺-binding allergens, such as parvalbumin (fish allergen) and Bet v 4 (birch pollen allergen), have been shown to contain conformational-type IgE epitopes associated with the Ca²⁺-chelating. This study was performed to clarify the relationships between IgE reactivity and structure of the black tiger shrimp SCP. When analyzed by ELISA in the absence and presence of EGTA, the IgE reactivity of the black tiger shrimp SCP was found to be considerably reduced by Ca²⁺-depletion. Furthermore, circular dichroism spectral data showed a conformational difference between Ca²⁺-bound and Ca²⁺-depleted forms of the black tiger shrimp SCP. On the other hand, the synthetic 18 peptides spanning the entire amino acid sequence of the black tiger shrimp SCP were all assessed to have little IgE-binding ability by ELISA. Our results demonstrate that the IgE reactivity of the black tiger shrimp SCP is attributable mostly to conformational-type IgE epitopes, at least part of which is maintained by Ca²⁺-chelating.     

Bacteriological quality of individually quick-frozen (IQF) raw and cooked ready-to-eat shrimp produced from farm raised black tiger shrimp (Penaeus monodon)

One thousand, two hundred and sixty four samples of individually quick-frozen (IQF) peeled and deveined raw and 914 samples of cooked ready to eat shrimp samples produced from farm raised black tiger (Penaeus monodon) obtained from a seafood unit working under HACCP concept were analysed for total aerobic plate count (APC), coliform count,Escherichia coli, coagulase positive Staphylococci andSalmonella. The overall bacteriological quality of the product was found to be good. Of the frozen raw shrimp, 96% of samples showed APC below 10⁵while 99% of the frozen cooked ready-to-eat samples showed APC less than 10⁴. The APC ranged from 1.0×10²to 4.2×10⁶cfu/gm in frozen raw shrimp and from 1.0×10²to 6.4×1⁴cfu/gm in the frozen cooked shrimp. Prevalences of coliforms in raw shrimp and cooked shrimp samples were 14.4% and 2.9% respectively. The coliform count in raw products ranged from 1.0×10¹to 2.5×10³cfu/gm and in the cooked products, from 1.0×10¹to 1.8×10²cfu/gm. Although all the cooked shrimp samples were free of coagulase positive staphylococci,E. coliandSalmonella, 1.0, 2.0 and 0.1% of the frozen raw shrimp samples tested positive for coagulase positive Staphylococci,E. coliandSalmonellarespectively. TheSalmonellastrain was identified asSalmonella typhimurium. The results of the present study highlight the importance of implementation of HACCP system in the seafood industry to ensure consistent quality of frozen seafood.     

Effect of storage temperature and packaging on quality and shelf‐life of high pressure processed black tiger shrimp (Penaeus monodon)

The effect of high pressure processing (361 MPa/12 min/46 °C) on the quality and shelf‐life of black tiger shrimp was investigated. Changes in physical, biochemical, microbiological, and sensory attributes of samples packed in low density polyethylene (LDPE), ethylene vinyl alcohol (EVOH), and multilayer metalized polyester (MMP) pouches were examined during storage at 4, 15, and 25 °C for 30 days. The estimated shelf‐life of pressure treated samples based on sensory, chemical, and microbiological data was found to be 30 days for EVOH and MMP samples and 18 days for LDPE samples at 4 °C. The control and high pressure samples at 15 °C reach the unacceptable limit by 3rd and 9th day of storage, respectively. However, the samples at 25 °C showed shelf‐life of less than 3 days. Among the packages employed in the study, EVOH film was adjudged to be best in maintaining the quality of shrimp.

Practical applications

In global seafood market, shrimp is a commercially traded important commodity. The conducted study detailed about the quality changes occurred due to microbial activity and biochemical reactions in high pressure processed black tiger shrimp under different storage and packaging conditions and their impact on the shelf‐life. The provided data will be useful in the selection of appropriate conditions to preserve the valuable catch, establish high quality and safety requirements to enhance the marketing potential of shrimp.     

Incidence of vibrios of public health significance in the farming phase of tiger shrimp (Penaeus monodon)

The incidence of some of the human pathogenic vibrios in the cultured tiger shrimp (Penaeus monodon) was evaluated during the farming phase in practice at a commercial semi-intensive shrimp farm off Uttarakannada, Karnataka (India). Possible sources of these human pathogens were also evaluated. Vibrio alginolyticus was found to be the most common Vibrio member (57% incidence). Vibrio cholerae, V parahemolyticus and V vulnificus were the other species encountered. All these occurred in shrimp pond sediment, pond water and the feed used (clam meat and formulated feed). Vibrio mimicus was encountered only in the dam meat used as a shrimp feed. A poor correlation between the faecal coliform level and the occurrence of these pathogenic vibrios was apparent, implying natural occurrence of these vibrios in the brackishwater/shrimp culture environment.     

Preharvest evaluation of coliforms, Escherichia coli, Salmonella, and Escherichia coli O157:H7 in organic and conventional produce grown by Minnesota farmers

Microbiological analyses of fresh fruits and vegetables produced by organic and conventional farmers in Minnesota were conducted to determine the coliform count and the prevalence of Escherichia coli, Salmonella, and E. coli O157:H7. A total of 476 and 129 produce samples were collected from 32 organic and 8 conventional farms, respectively. The samples included tomatoes, leafy greens, lettuce, green peppers, cabbage, cucumbers, broccoli, strawberries, apples, and seven other types of produce. The numbers of fruits and vegetables was influenced by their availability at participating farms and varied from 11 strawberry samples to 108 tomato samples. Among the organic farms, eight were certified by accredited agencies and the rest reported the use of organic practices. All organic farms used aged or composted animal manure as fertilizer. The average coliform counts in both organic and conventional produce were 2.9 log most probable number per g. The percentages of E. coli-positive samples in conventional and organic produce were 1.6 and 9.7%, respectively. However, the E. coli prevalence in certified organic produce was 4.3%, a level not statistically different from that in conventional samples. Organic lettuce had the largest prevalence of E. coli (22.4%) compared with other produce types. Organic samples from farms that used manure or compost aged less than 12 months had a prevalence of E. coli 19 times greater than that of farms that used older materials. Serotype O157:H7 was not detected in any produce samples, but Salmonella was isolated from one organic lettuce and one organic green pepper. These results provide the first microbiological assessment of organic fruits and vegetables at the farm level.     

Prevalence of bacteria of public health significance in the cultured shrimp (Penaeus monodon)

The prevalence of some human pathogenic bacteria, namelySalmonella, Vibriospp. andListeria monocytogenes, in shrimps under different stages of farming operations was determined by using standard methods.SalmonellaandVibriowere present in all samples analysed.Listeriaspp. was absent from all the samples except clam meat analysed during the farming phase and sediment and shrimps at harvest. A poor correlation was observed between the level of indicator organisms (coliforms) and the incidence of these pathogens, indicating that these pathogens are a part of the natural microfauna of the shrimp culture environment.     

Aflatoxin B1 contamination of shrimp feeds and its effect on growth and hepatopancreas of pre-adult Penaeus monodon

A survey of aflatoxin B₁ (AFLB₁) levels in commonly used commercial shrimp finisher feeds in the Philippines showed a various range of values from not detected to 120 μg kg^?1 using high-performance thin-layer chromatography. Six experimental diets were prepared to contain various levels of AFLB₁ based on survey results to determine the effects of such contamination in pre-adult shrimp Penaeus monodon (17.5 ± 0.6 g). Results showed that shrimps fed diets containing AFLB₁ greater than or equal to 73.8 μg kg^?1 gave comparatively poor growth rate and higher susceptibility to shell diseases. No AFLB₁ residues were detected in sampled whole shrimp tissues after 62 days of exposure to AFLB₁ containing diets indicating a low potential for transmission of the toxin from edible shrimp tissues to consumers. Histopathological alterations in the hepatopancreas of shrimp chronically exposed to AFLB, were observed in all samples. The degree of alterations correlated with the level of AFLB₁. Based on growth performance, pre-adult shrimps can tolerate AFLB₁ levels of up to 52.3 μg kg^?1 in the feeds although histopathological changes were already evident in the tissues of shrimps given diets with 26.5 μg kg^?1 AFLB₁.     

Application of ergothioneine-rich extract from an edible mushroom Flammulina velutipes for melanosis prevention in shrimp,Penaeus monodon and Litopenaeus vannamei

This report investigated the melanosis-inhibiting properties of crude water soluble extract from the base and fruiting body waste of an edible mushroom (Flammulina velutipes) containing 9.13 ± 2.03 mg/mL 2-thiol-l-histidine-betaine (ergothioneine, ESH). Immersion of live full-grown black tiger shrimp (Penaeus monodon) and Pacific white shrimp (Litopenaeus vannamei) in a 0.5% w/v solution of mushroom extract for 1 h significantly decreased polyphenoloxidase (PPO) activity in shrimp hemolymph and expression of the prophenoloxidase (proPO) gene in hemocytes. Consequently, the development of melanosis in the treated shrimp during ice storage was prevented. Treatment with a 0.05% w/v solution of sodium sulfite and 4-hexyl-1,3-benzenediol had a similar effect. Enzyme assays showed that ESH is a non-competitive inhibitor. It is proposed that ESH possibly interacts directly with Cu²⁺ at the putative binding sites of PPO and proPO, based on copper-chelating activity analyses, thus preventing melanosis in the shrimp. This study indicated that application of ESH-rich F. velutipes mushroom extract from trimming waste is an effective natural alternative to synthetic melanosis-inhibiting agents to prevent postmortem melanosis in shrimp.     

An evaluation of rapid methods for detecting Escherichia coli O157 on beef carcasses

Numbers of Escherichia coli O157 in food may be low and sensitive techniques are therefore needed for its detection. The objectives of this study were to use carcass meat samples artificially inoculated with various strains of E. coli O157 to compare the sensitivity of enrichment in three different media and to compare immunomagnetic separation followed by culture of magnetic beads to cefixime tellurite sorbitol MacConkey agar with three immunoassays for the detection of E. coli O157 in the enrichment cultures. Duplicate 250, 25 and 2-3 CFU of each of 16 strains of E. coli O157 added to 25-g samples of beef carcass meat were used to compare the sensitivity of (1) enrichment in supplemented tryptone soya broth (sTSB), Reveal 8-h and Reveal 20-h media, and (2) immunomagnetic separation and culture to cefixime tellurite sorbitol MacConkey agar (IMS/CT-SMAC) with Reveal, VIP and STAT immunoassays for detecting the organism. An initial inoculum of 250 CFU/25 g meat was detected in all 32 samples by IMS/CT-SMAC performed on all enrichment media and by Reveal performed on Reveal 8-h and Reveal 20-h media, but in only 30, 19 and 9 samples by Reveal, VIP and STAT, respectively, performed on sTSB medium. An initial inoculum of 25 CFU/25 g meat was detected in 28, 32 and 30 of 32 samples by IMS/CT-SMAC performed on sTSB, Reveal 8-h and Reveal 20-h media, respectively, and in 32 and 30 samples by Reveal performed on Reveal 8-h and Reveal 20-h media, but in only 22, 11 and 2 samples by Reveal, VIP and STAT, respectively, performed on sTSB medium. An initial inoculum of 2-3 CFU/25 g meat was detected in 25, 31 and 28 of 32 samples by IMS/CT-SMAC performed on sTSB, Reveal 8-h and Reveal 20-h media, respectively, and in 25 and 23 samples by Reveal performed on Reveal 8-h and Reveal 20-h media, but in only 14, 1 and 0 samples by Reveal, VIP and STAT, respectively, performed on sTSB medium.     

基于SiO2荧光纳米粒子快速检测果汁中 大肠杆菌的免疫传感器研究

目的设计一种基于SiO_2荧光纳米粒子快速检测果汁中大肠杆菌O157:H7的新型传感器。方法采用超分子组合法将荧光基团嵌入到SiO_2纳米颗粒中合成SiO_2荧光纳米粒子,然后将抗大肠杆菌O157:H7的单抗偶联到纳米粒子表面,最后通过抗原-抗体反应使纳米粒子与待检细菌结合,使用荧光显微镜观察并统计大肠杆菌O157:H7的个数。结果本方法与革兰氏染色法相比,对大肠杆菌O157:H7计数结果无统计学差异(P=0.930);该方法整个检测过程能够在15 min内完成,检测下限小于10 CFU/mL。结论该方法能增强检测果汁中大肠杆菌O157:H7的灵敏度,缩短检测时间,对其他病原体检测方法的改进具有重要的指导意义。     

Changing in processing yield and physical properties of frozen white shrimp (Penaeus vannamei) treated with lysine and sodium bicarbonate

The objective of this research was to investigate the phosphate alternative use of natural compound, lysine with sodium bicarbonate (NaHCO₃), at low concentration for freezing of white shrimp (Penaeus vannamei). Shrimp were treated with lysine, NaHCO₃ and lysine with NaHCO₃ at various concentrations and frozen in an air‐blast freezer. Thawing yield, cooking yield, colour, texture and nanostructure of the sample were studied compared to the control (nontreated sample) and sodium tri‐polyphosphate (STPP) treated one. Use of lysine/NaHCO₃ each at 1% (w/v) could improve water holding capacity (WHC) of the frozen shrimp, increasing cooking yield to 100.45% (w/w), comparable to the 101.73% (w/w) of STPP‐treated sample. The colour of the noncook‐thawed shrimp was also improved. Microstructure and lipid oxidation of the treated samples were also studied. The combination of lysine and NaHCO₃ indicated high potential use as phosphate alternative for frozen white shrimps.     

Rapid and miniaturized method for detection of hygiene indicators,Escherichia coli and coliforms,in dairy products

Current investigation was aimed to develop colorimetric tests for rapid detection of Escherichia coli/coliforms. These test (s) for E. coli and coliforms were developed using the modified E. coli selective medium (M-ECSM) and coliform selective medium, respectively. The selective media contain a combination of group specific marker enzymes and selective agents. The marker enzymes were screened using chromogenic substrates wherein β-D-glucuronidase and glutamate decarboxylase were found specific for E. coli while β-D-galactosidase for coliforms. The selectivity of the media was achieved using different concentrations of ampicillin and gentamicin. The optimized test procedures enabled sensitive detection of 0.35 ± 0.10 log cfu/ml of E. coli and 0.57 ± 0.15 log cfu/ml of coliforms at 37°C within 14.30 ± 0.45 and 12.15 ± 0.30 hr, respectively. M-ECSM selectively inhibited major Enterobacteriaceae contaminants (Salmonella, Shigella, and Yersinia) up to 6 log cfu/ml. Moreover, better selectivity of M-ECSM was reported against tested commercial chromogenic media. Field evaluation of developed test (s) reported prevalence of E. coli/coliforms as 57.29/88.54% in 96 raw milk and 16.28/51.16% in 43 pasteurized milk samples. Further, test components were vacuum dried in the form of miniaturized point-of-need test for field application in dairy farms and industries with minimal infrastructural requirements.     

Changes in lipid profiles and volatile compounds of shrimp (Penaeus vannamei) submitted to different cooking methods

Herein, the effect of three common cooking methods (boiling, baking and microwaving) on lipids and volatile compounds in shrimp (Penaeus vannamei) was assessed. The results revealed that contents of phospholipid, triglyceride, cholesterol and free fatty acids in the cooked shrimp significantly declined when compared to the raw shrimp. And these decreases occurred especially in the boiling and microwaving treatment. Among free fatty acids, the contents of palmitic acid (C_16:0), oleic acid (C_18:1n9c) and linoleic acid (C_18:2n6c) also decreased greatly in the boiled and microwaved shrimp, while EPA and DHA enhanced in each cooked group (P < 0.05). Furthermore, microwaved samples exhibited higher levels of oxidation parameters, such as acid value (AV) and thiobarbituric acid-reactive substances (TBARS). For volatile compounds, a total of 31 volatile compounds were detected by GC-IMS, and these contents increased after cooking. Aliphatic volatile compounds, including 1-octen-3-one, pentane-1-ol, 1-propanol, octanal, heptanal, pentanal and hexanal, were main flavour contributors in cooked shrimp, with higher contents observed in microwaved shrimp. In addition, the correlation analysis showed that linoleic acid was a substrate for 15 volatile compounds of cooked shrimp meat. These results indicate that microwave cooking exerts more influences on lipid profiles in shrimp and consequently caused more volatile compounds.     

Sensitive detection of Escherichia coli O157:H7 by conventional plating techniques

The direct detection and estimation of concentration of Escherichia coli O157:H7 down to 1 CFU/g of cheese was achieved by conventional plating techniques. Cheese was manufactured with unpasteurized milk inoculated with E. coli O157: H7 at 34 +/- 3 CFU/ml. The numbers of E. coli O157:H7 were monitored during cheese ripening by plating on sorbitol MacConkey agar supplemented with cefixime and potassium tellurite (CT-SMAC) and on CT-O157:H7 ID medium. Using the pour plate method, E. coli O157:H7 colonies could easily be distinguished from non-O157:H7 colonies on CT-O157:H7 ID medium but not on CT-SMAC. Higher numbers of E. coli O157:H7 were detectable with O157:H7 ID medium. Latex agglutination and PCR were used to confirm the identification of typical E. coli O157:H7 colonies, and nontypical colonies as not being E. coli O157:H7. As few as 1 CFU/g of cheese could be detected. E. coli O157:H7 also was detected in deliberately contaminated milk at concentrations as low as 4 CFU/10 ml.     

Bactericidal activity of ozone against Escherichia coli in whole and ground black peppers

The effects of different ozone concentrations and ozonation times on the inactivation of Escherichia coli and on the organoleptic properties of whole and ground black peppers were determined. Black peppers were exposed to three different ozone concentrations (0.1, 0.5, and 1.0 ppm) for different periods (0 to 360 min) at 85% +/- 3% relative humidity (RH) and 25 +/- 0.5 degree C. An approximately 7-log CFU/g reduction of E. coli in whole black peppers was achieved by treating the samples with 0.1, 0.5, or 1.0 ppm of ozone for 360, 240, or 120 min, respectively. E. coli populations in ground black peppers were reduced from an initial count of about 7.5 log CFU/g to 1 log CFU/g after 360 min at 0.1- and 0.5-ppm ozone concentrations, whereas the same microbial reduction was obtained after 240 min at 1.0-ppm ozone concentration. An ozone concentration of 0.1 ppm for 360 min was found to be appropriate to inactivate E. coli in whole and ground black peppers without alteration of the organoleptic properties. No significant differences (P > or = 0.05) were present in the bitterness, flavor, odor, color, or overall acceptability values of the whole and ground black peppers treated with 0.1 ppm of ozone for up to 360 min.     

Comparative studies on chemical composition and thermal properties of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) meats

Chemical composition and thermal properties of meat from two species of shrimps, black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei), were comparatively studied. White shrimp meat had higher protein and ash contents than had black tiger shrimp meat (p < 0.05). Fractionation of nitrogenous constituents revealed that myofibrillar protein was the major component in the muscles; myosin heavy chain (MHC) and actin were the predominant proteins. White shrimp meat comprised higher stromal protein with greater pepsin-soluble collagen and insoluble collagen contents than did black tiger shrimp meat. Muscle proteins from black tiger shrimp, especially MHC, had higher thermal stability than those from white shrimp as indicated by the higher transition temperature (T_max) as well as the lower inactivation rate constant (K_D). Phospholipid was the predominant lipid (72–74%) in both shrimps, followed by triglyceride. Polyunsaturated fatty acids were found as the major fatty acids with the range of 42.2–44.4%. DHA (22:6)/EPA (20:5) ratio in black tiger shrimp (2.15) was higher than that in white shrimp (1.05). Mg was the dominant mineral in both shrimps. Ca and Fe were also found at high concentrations. Arginine was the most abundant amino acid, while leucine, isoleucine and proline were predominant in both shrimps. Glutamic acid and glycine contents were greater in black tiger shrimp meat; however, white shrimp meat had higher hydroxyproline content. Different compositions might govern the different characteristics as well as thermal properties of both species.     

进口黑虎虾中霍乱弧菌的鉴定及其挥发性产物分析

目的对进口黑虎虾中分离的菌株F14-2进行种属鉴定,通过顶空气相色谱-质谱联用法(headspace gas chromatography-mass spectrometry,HS-GC-MS)分析分离菌株液态培养代谢的挥发性产物。方法应用VITEK 2 Compact全自动微生物鉴定系统分析菌株的生理生化特征,利用荧光定量PCR特异性扩增检测病原菌,通过顶空气相色谱-质谱联用法分析分离菌株F14-2的代谢的挥发性产物。结果菌株F14-2为革兰氏阴性菌,生理生化特征与霍乱弧菌(Vibrio cholerae)的相似性为98%,荧光定量PCR检测和血清凝集试验进一步确认为非O1非O139群霍乱弧菌,菌株F14-2在营养肉汤(nutrient broth)中代谢的挥发性产物主要有乙醇、异戊醇、乙酸和2-乙基己醇。结论进口黑虎虾中分离的菌株F14-2鉴定为霍乱弧菌,该菌产生的挥发性产物为霍乱弧菌的鉴定提供参考。     

Effect of reactant concentrations on the Maillard reaction in a fructose–glycine model system and the inhibition of black tiger shrimp polyphenoloxidase

The characteristics and the inhibitory activity towards black tiger shrimp polyphenoloxidase of Maillard reaction products (MRPs), prepared by heating an equimolar mixture of fructose and glycine at various concentrations (0.75–30 mM) at 100 °C for 12 h, were investigated. Increase in the intermediate products was observed with increasing reactant concentration, as evidenced by the increase in A₂₉₄ and fluorescence intensity. Furthermore, development of browning (A₄₂₀) was noticeable when the reactant concentration increased. The inhibitory activity of MRPs towards PPO gradually increased when the concentration of each reactant increased and reached a maximum at 30 mM (80% inhibition). The increase in the inhibitory activity of MRPs was coincidental with the increase in the reducing power, A₂₉₄, fluorescence intensity, as well as browning intensity. Generally, the development of Maillard reaction products was associated with decrease in pH and loss of reducing sugar and free amino groups, with coincidental increase in reducing power and copper-chelating property. MRPs with the reactant concentration of 4.5–30 mM were able to chelate the copper ion. Therefore, the inhibitory activity of MRPs towards browning, induced by PPO, was most likely due to their copper-chelating property as well as reducing power.