Comparative studies on the effect of the freeze–thawing process on the physicochemical properties and microstructures of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) muscle

The effects of different freeze–thaw cycles (0, 1, 3 and 5) on the physicochemical properties and microstructures of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) muscle were investigated. White shrimp had greater exudate loss and higher α-glucosidase (AG), as well as β-N-acetyl-glucosaminidase (NAG) activities, than did black tiger shrimp, especially when the number of freeze–thaw cycles increased (P < 0.05). The decreases in Ca²⁺-ATPase activity, sulfhydryl group content and protein solubility with concomitant increases in disulfide bond formation and surface hydrophobicity were more pronounced in white shrimp muscle, than in black tiger shrimp muscle, particularly after five cycles of freeze–thawing (P < 0.05). The shear force of both shrimps was decreased after five freeze–thaw cycles (P < 0.05). The microstructure study revealed that the muscle fibers were less attached, with the loss of Z-disks, after subjection to five freeze–thaw cycles. Therefore, the freeze–thawing process caused denaturation of proteins, cell disruption, as well as structural damage of muscle in both shrimps. White shrimp generally underwent physicochemical changes induced by the freeze–thawing process to a greater extent than did black tiger shrimp.     

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.     

Seasonal amino acid profiles and mineral contents of green tiger shrimp (Penaeus semisulcatus De Haan, 1844) and speckled shrimp (Metapenaeus monoceros Fabricus, 1789) from the Eastern Mediterranean

The amino acid and mineral contents of green tiger shrimp (Penaeus semisulcatus) and speckled shrimp (Metapenaeus monoceros) from the North Eastern Mediterranean were determined for each season of the year. For both species, the highest protein values were recorded during the summer (p < 0.05). The most abundant amino acids were, in decreasing order, glutamic acid, aspartic acid, arginine, lysine, leucine, glycine and alanine. The ratio of essential to nonessential amino acids (mean value) for green tiger shrimp and speckled shrimp were 0.60 and 0.59, respectively. Mineral contents of the two species varied with season (p < 0.05), except for the Ca content in green tiger shrimp.     

Gelling properties of white shrimp (Penaeus vannamei) meat as influenced by setting condition and microbial transglutaminase

The properties of white shrimp (Penaeus vannamei) gel added with different levels of microbial transglutaminase (MTGase) and subjected to setting at 25 °C for 2 h or 40 °C for 30 min, prior to heating at 90 °C for 20 min were studied. Breaking force of gels with and without setting increased with increasing MTGase amount added (P<0.05). However, no changes in deformation in all samples were noticeable (P>0.05). Directly heated gels showed the lower breaking force than those with prior setting at all MTGase levels added (P<0.05). Generally, gels prepared by setting at 25 °C exhibited the greater breaking force than those set at 40 °C, possibly associated with the appropriate protein structure for cross-linking at 25 °C and greater degradation at 40 °C as evidenced by a greater trichloroacetic acid soluble peptide content (P<0.05). Sodium dodecyl sulfate polyacrylamide gel electrophoretic study revealed that myosin heavy chain (MHC) underwent polymerization to a higher extent in the presence of MTGase, but the strengthening effect on gel was dependent on setting temperature. Regardless of setting condition, microstructure of gel added with MTGase was finer with a smaller void, compared with those of gel without MTGase. Therefore, setting temperature played an essential role in gel property of white shrimp meat added with MTGase.     

Quality and shelf life assessment of Pacific white shrimp (Litopenaeus vannamei) freshly harvested and stored on ice

Pacific white shrimps (Litopenaeus vannamei) are an important shrimp aquaculture species worldwide. To quantify the quality and shelf life of untreated shrimp is imperative prior to the application of preservative treatments. In this paper, the quality and shelf life of Pacific white shrimp freshly harvested from three different farms and stored on ice for up to 12 days was investigated. The titratable acidity (TA) of shrimp specimens exhibited significant decreases (P < 0.05) whereas the metric chroma (C), total colour difference (TCD), aerobic plate count (APC), trimethylamine (TMA-N) and total volatile basic – nitrogen (TVB-N), peroxide value (PV) and p-anisidine value (AnV) exhibited significant increases during iced storage (P < 0.05). The TMA-N and TVB-N were significantly correlated whereas temporal TMA-N/TVB-N ratio increased considerably (P < 0.05). While the PV and AnV significantly correlated (P < 0.05), the temporal PV/AnV ratio depicted how primary and secondary lipid oxidation of Pacific white shrimp could relate during iced storage of 12 days. The shelf life of ice stored Pacific white shrimps was determined to be 8 days. The information gained by this study could serve as baseline for preservative treatments applied to fresh shrimps.     

Inhibition of melanosis formation in Pacific white shrimp by the extract of lead (Leucaena leucocephala) seed

Lead (Leucaena leucocephala) seed extract was prepared using distilled water as a medium. An extraction yield of 26.16 g/100 g of seed was obtained after extraction at room temperature for 12 h. Total phenolic and mimosine contents in the lead seed extract powder (LSEP) were 17.4 g GAE/100 g and 8.8 g/100 g, respectively. LSEP at different concentrations (0.05%, 0.1%, 0.25%, 0.5%, and 1%, w/v) showed inhibitory activity towards polyphenoloxidase (PPO) of Pacific white shrimp in a dose dependent manner. When the whole Pacific white shrimp were treated with 0.25% and 0.5% (w/v) LSEP, the shrimp treated with 0.5% LSEP had the lower melanosis score throughout the storage of 12 days and showed a higher score for colour and odour, as well as overall likeness, compared with the control (without treatment) and 1.25% sodium metabisulphite treated samples at day 12 (P < 0.05). Meat of shrimps treated with LSEP at both levels had the increase in mimosine content up to 8 days, suggesting the migration of mimosine into shrimp muscle during extended storage. Therefore, 0.5% LSEP can be used as a novel melanosis inhibitor for Pacific white shrimp.     

Effect of ferulic acid on inhibition of polyphenoloxidase and quality changes of Pacific white shrimp (Litopenaeus vannamei) during iced storage

Effects of ferulic acid (FA) on polyphenoloxidase (PPO) and the quality changes of Pacific white shrimp (Litopenaeus vannamei) during iced storage for 10 days were investigated. Both FA and oxygenated FA (OFA) with different concentrations (0.1%, 0.5%, 1% and 2% (w/v)) showed PPO inhibitory activity in a dose dependent manner. FA was generally more effective in PPO inhibition than was OFA. Based on activity staining, white shrimp PPO with an apparent molecular weight of 210 kDa was inhibited by FA. When whole shrimps were treated with FA solution with concentrations of 1% or 2% and stored in ice for up to 10 days, the increase in psychrophilic and mesophilic bacterial count were retarded, in comparison with the control and those treated with 1.25% sodium metabisulphite (SMS). The coincidental lower rates of increase in pH and total volatile base content were obtained. Additionally, shrimps treated with 2% FA possessed the lowest peroxide value and thiobarbituric acid reactive substances (TBARS) value during the storage. After 10 days of storage, shrimps treated with 2% FA had the lower melanosis score and higher score for colour, flavour and overall likeness, compared with the control and SMS treated shrimps (P < 0.05).     

Influences of sex and seasons on levels of heavy metals in tissues of green tiger shrimp (Penaeus semisulcatus de Hann, 1844)

Seasonal changes in heavy metal (Ag, Cr, Ni, Pb, Cu, Fe, Zn) concentrations in muscle, gill, hepatopancreas and gonad tissues of both male and female green tiger shrimp (Penaeus semisulcatus) from Iskenderun Bay (Northern East Mediterranean Sea, Turkey) were measured for a year period by using ICP-AES. The relationships in various heavy metal concentrations in organs were compared according to sex and seasons. Heavy metal content varied with type of metals, seasons and sex. Accumulations also differed significantly in certain organs. Metal concentrations (as μg g⁻¹ w.w.) were highest in male gonads whereas lowest in the muscle of all shrimp species. From the human consumption point of view, heavy metal concentrations except for copper in male and female green tiger shrimp’s muscle were below the admissible limits. Thus, precautions should be taken on account of higher content of heavy metals as well as in other organs that could be affected by industrial pollution.     

Effects of bactericides and modified atmosphere packaging on shelf-life of Chinese shrimp (Fenneropenaeus chinensis)

Effects of different bactericides and modified atmosphere packaging (MAP) on aerobic plate counts (APCs), total volatile base-nitrogen (TVB-N) and organoleptic evaluation of overall acceptable score (OA score) of Chinese shrimp (Fenneropenaeus chinensis) during cold storage were investigated. Results indicated that APC in MAP(40%CO₂/30%O₂/30%N₂) shrimp treated with compound bactericide reached 10⁷ cfu/g on the 13th day of storage, while that of ozonated water or water control treatments exceed 10⁷ cfu/g on the 9th day. APC in shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide reached close to 10⁷ cfu/g at day 13, while that of air treatment exceed 10⁷ cfu/g. TVB-N value in MAP(40%CO₂/30%O₂/30%N₂) shrimp treated with compound bactericide was slightly higher than the upper threshold of 30 mg/100 g on the 17th day, while that of ozonated water treatment or water control increased to or over the threshold value on the 9th day. TVB-N value in shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide were significantly lower than that of air control on the 17th day (P ≤ 0.01), with a value of 33.6 mg/100 g and 42-47.6 mg/100 g respectively, compared to 78.4-86.8 mg/100 g in air control. The lowest OA score of MAP(40%CO₂/30%O₂/30%N₂) whole and decapitated shrimps treated with compound bactericide appeared on the 17th and 21th day, respectively, compared with the 9th day in whole shrimp and the 13th day in decapitated shrimps treated with ozonated water and water control. The lowest OA score of whole and decapitated shrimps treated with MAP (40%CO₂/30%O₂/30%N₂) or 100%CO₂ after soaking with compound bactericide appeared on the 17th and 21th day, respectively, compared with the 13th and 17th day in air control. In conclusion, when combined the parameters determined together, the shelf-life of Chinese shrimp at 2 ± 1 °C, either whole or decapitated, treated with MAP (40%CO₂/30%O₂/30%N₂) and 100%CO₂ after soaking with compound bactericide were 13 and 17 days, respectively.     

Inhibition kinetics of catechin and ferulic acid on polyphenoloxidase from cephalothorax of Pacific white shrimp (Litopenaeus vannamei)

Inhibition kinetics and mode of catechin and ferulic acid towards polyphenoloxidase (PPO) from cephalothorax of Pacific white shrimp were investigated. Catechin or ferulic acid inhibited quinone formation catalysed by PPO in a dose dependent manner. Catechin showed mixed type reversible inhibition with K_i value of 1.4 mM, whereas ferulic acid exhibited non-competitive reversible inhibition with K_i value of 37 mM. With increasing concentrations, both catechin and ferulic acid had higher copper (Cu²⁺) reduction and copper chelating capacity (P < 0.05). Catechin or ferulic acid could react with intermediated browning reaction products, thereby preventing dopachrome formation. Thus, catechin or ferulic acid could inhibit melanosis in Pacific white shrimp with different modes of inhibition towards PPO.     

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.     

Molecular identification of the black tiger shrimp (Penaeus monodon), the white leg shrimp (Litopenaeus vannamei) and the Indian white shrimp (Fenneropenaeus indicus) by PCR targeted to the 16S rRNA mtDNA

Polymerase chain reaction-based methodologies have been developed for the identification of three commercially-relevant penaeid shrimp species, these were: Litopenaeus vannamei, Penaeus monodon and Fenneropenaeus indicus in food products. Such three species represent more than 80% of the whole farmed shrimp production worldwide and may be fraudulently replaced by species exhibiting lower value such as Litopenaeus stylirostris, Penaeus semisulcatus and Fenneropenaeus merguiensis, respectively. For it, preliminary sequencing of a mitochondrial sequence of ca. 530 bp in the 16S rRNA/tRNA^Val mitochondrial region was performed in nearly 20 penaeid shrimp species of commercial relevance. Careful analysis of such sequences allowed the design of primers PNVF/PNVR, which allowed the combined identification of P. monodon and L. vannamei, and PNIF/PNIR, which allowed the specific identification of F. indicus. In addition, P. monodon and L. vannamei could be easily differentiated by either restriction with TspE1 or by amplification with novel primers MPNF/MPNR, specific for P. monodon. The proposed specific methods improve current general identification methods of these species based on more general RFLP analyses. In addition, these methods can be easily completed in less than 8 h.     

Proximate composition and extraction of carotenoids and lipids from Brazilian redspotted shrimp waste (Farfantepenaeus paulensis)

The chemical composition of redspotted shrimp (Penaeus paulensis) waste was investigated. The shrimp waste (freeze-dried heads, shells and tails) was found to have high protein (49% d.w.) and ash (27% d.w.) contents, but a low lipid content (4.9% d.w.) although the latter was higher than those found in other kinds of shrimp captured in Brazil. The fatty acid compositions showed that the lipids had a high content of unsaturated fatty acids, mainly EPA (C20:5; n-3) and DHA (C22:6; n-3). In order to establish an efficient and environmentally friendly recovery process for the astaxanthin (principal carotenoid and antioxidant present in the waste), the following processes were examined: traditional solvent extraction (TSE), super-critical fluid extraction (SC-CO₂) and super-critical fluid extraction with co-solvent (SC-CO₂ + ethanol). The temperature and pressure conditions for all the SC-CO₂ extractions were 50 °C and 30.0 MPa. The results showed that the mixture of 60% (v/v) n-hexane:isopropyl alcohol gave the highest (53 mg/kg waste) carotenoid extraction yield as compared to acetone, SC-CO₂ and SC-CO₂ + ethanol. The SC-CO₂ showed the lowest extraction yield of astaxanthin, but the addition of the entrainer (10% w/w) produced an important effect, increasing the astaxanthin extraction to values of 57.9%, similar to extraction with acetone (63.3%).     

The cryoprotectant effect of shrimp chitin and shrimp chitin hydrolysate on denaturation and unfrozen water of lizardfish surimi during frozen storage

Shrimp chitin and shrimp chitin hydrolysate prepared from black tiger (Penaeus monodon), endeavour (Metapenaeus endeavouri) and giant freshwater (Macrobrachium rosenbergii) prawns were added to lizardfish surimi, and it was frozen and stored at −25 °C for 6 months to evaluate freeze-induced protein denaturation. Changes in total Ca-ATPase activity and the amount of unfrozen water in samples were periodically determined during frozen storage. The surimi containing shrimp chitin showed the same freeze-denaturaion rate (K_D) as the surimi without cryoprotectants (control), and the amount of unfrozen water was lower than that of control. However, surimi containing shrimp chitin hydrolysates showed K_D values equal to surimi containing sucrose or glucose but lower than the control, and the amount of unfrozen water was increased compared to control. The results revealed that shrimp chitin hydrolysates retarded the effects on freeze-induced denaturation by stabilizing the hydrated water molecules that surround the protein.     

Characterisation and tissue distribution of polyphenol oxidase of deepwater pink shrimp (Parapenaeus longirostris)

Characterisation and tissue distribution of polyphenol oxidase (PPO) was studied in deepwater pink shrimp (Parapenaeus longirostris) post mortem. PPO activity was the highest in the carapace, followed by that in the abdomen exoskeleton, cephalotorax, pleopods and telson. No PPO activity was found in the abdomen muscle and in the pereopods and maxillipeds using the enzymatic assay. Storage of whole shrimps and of the different organs showed that melanosis (blackening) required the presence of the cephalotorax to be initiated, indicating that its development depends on other factors in addition to the PPO levels. Further characterisation was carried out in extracts partly purified using 40–70% ammonium sulfate fractionation. The enzyme had the highest activity at pH 4.5 and was most stable at pH 4.5 and 9.0. No clear maximum was observed in the 15–60 °C range but the higher stability was achieved at 30–35 °C. Apparent kinetic constants in the partly purified PPO from carapace were K_M = 1.85 mM and V_max = 38.5 U/mg of protein, pointing to a high affinity and reactivity of the enzyme when assayed with DOPA. Electrophoretic mobility was studied in native PAGE and non-reducing SDS–PAGE followed by staining with DOPA. Approximate MW of 500 kDa and 200 kDa were observed, respectively. These two forms could correspond to aggregates of minor PPO subunits that could not be resolved in these electrophoretic systems. The peptide mass fingerprinting obtained by MALDI-TOF analysis showed some peptides whose homology with hemocyanins and different PPO subunit precursors has already been demonstrated in the same species.     

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.     

The effects of sodium bicarbonate on conformational changes of natural actomyosin from Pacific white shrimp (Litopenaeus vannamei)

Changes in natural actomyosin (NAM) from Pacific white shrimp (Litopenaeus vannamei) treated with sodium bicarbonate (NaHCO₃) at different concentrations (0–1 M) in the absence or the presence of 2.5% NaCl were studied. Turbidity of NAM solutions decreased with coincidental increase in solubility as the concentration of NaHCO₃ increased. Surface hydrophobicity (S_oANS) and total sulfhydryl content of NAM also increased when NaHCO₃ concentration increased. Greater decreases in Ca²⁺- and Mg²⁺-ATPase activity were found in all NAM as NaHCO₃ concentration increased, suggesting the denaturation of myosin head and the dissociation of actomyosin complex. The zeta potential (ζ) analysis suggested that the surface of NAM became more negatively charged (−12.12 to −26.98) as NaHCO₃ concentration increased. Those changes were more intense in the presence of 2.5% NaCl. Transmission electron microscopy showed that the structure of actomyosin was more dissociated and lost the filamental structure when NaHCO₃ at higher levels was used.     

脂质对凡纳滨对虾热风干制品香气特性的影响

为研究脂质对凡纳滨对虾热风干制品香气特性的影响,通过有机试剂去除虾体中的甘油三酯或磷脂,采用气相色谱-质谱联用技术和感官评价分析脂质对虾干制品香气特性的影响,以气味活性值(odor activity value,OAV)为指标,筛选香气活性化合物,同时采用偏最小二乘回归法(partial least squares regression,PLSR)分析挥发性化合物与感官属性之间的相关性。结果表明:去除甘油三酯对虾干制品整体香气影响较小,烤香味、肉香味和腥味的感官评分稍有减弱,而去除磷脂对主要香气特征有很大影响,烤香味、肉香味、腥味、焦糖香和甜香味的感官评分均大幅度降低;虾干制品中鉴定出16种香气活性化合物,吡嗪类、胺类、杂环类、醛类是其主要成分,其中3-乙基-2,5-二甲基吡嗪、2,5-二甲基吡嗪、三甲胺、3-(甲硫基)丙醛是贡献最大的4种物质;去除甘油三酯和磷脂后,吡嗪类、胺类、杂环类、醛类的OAV值显著下降,而去除磷脂后下降幅度更大,且在去磷脂虾干制品中2-戊基呋喃和3-(甲硫基)丙醛未检出;PLSR结果表明,18种香气活性化合物与感官属性具有较好的相关性。综上所述,脂质对虾干制品整体香气有较大影响,而磷脂对香气特性的作用远大于甘油三酯。该研究为虾类特征香气的形成机制研究提供了理论参考。     

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.