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).     

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.     

Use of tea extracts for inhibition of polyphenoloxidase and retardation of quality loss of Pacific white shrimp during iced storage

Green tea and mulberry tea powder with and without prior chlorophyll removal were extracted with water and ethanol (800 mL L⁻¹). Extraction yield and total phenolic content of green tea extract were higher than those of mulberry tea extract, regardless of extraction media (P < 0.05). Extracts from green tea with and without prior chlorophyll removal showed the higher polyphenoloxidase (PPO) inhibitory activity, compared with mulberry tea extract, at the concentration used (0.1, 0.5 or 1 g L⁻¹). Additionally, green tea extracts had the higher reducing power, 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activities and copper chelating activity, compared with mulberry tea extract (P < 0.05). Ethanolic green tea extract with prior chlorophyll removal contained (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCg) and (−)-epicatechin gallate (ECG) at the levels of 242, 33.4, 125.6, 140.6 and 25.2 g kg⁻¹ dry extract, respectively. Whole white shrimp (Litopenaeus vannamei) treated with ethanolic green tea extract with prior chlorophyll removal at concentrations of 5 and 10 g L⁻¹ and stored in ice for up to 12 days had the lower psychrophilic bacterial count and lipid oxidation, compared with the control and shrimp treated with 12.5 g L⁻¹ sodium metabisulfite (SMS) (P < 0.05). Shrimp treated with 5 g L⁻¹ ethanolic green tea extract with prior chlorophyll removal possessed the lower melanosis, compared with the control, and showed similar score to those treated with SMS (P > 0.05). Furthermore, ethanolic green tea extract with prior chlorophyll removal had no adverse impact on sensory attributes of treated shrimp.     

The effect of heating conditions on polyphenol oxidase, proteases and melanosis in pre-cooked Pacific white shrimp during refrigerated storage

Pre-cooked Pacific white shrimp (Litopenaeus vannamei) is an important shrimp product. However melanosis, especially in the cephalothorax including carapace and internal organs, is more likely caused by the remaining polyphenol oxidase (PPO) after pre-cooking. Thus, PPO from carapace and proteases from hepatopancreas of Pacific white shrimp were characterised and the remaining activities of both enzymes were monitored in pre-cooked shrimp during storage at 4 °C. Based on activity staining using L-β-(3,4 dihydroxylphenyl) alanine as a substrate, PPO consisted of two isoforms with apparent molecular weight of 210 and 220 kDa. No difference in activity band was observed when analysed under reducing and non-reducing condition. Proteases from hepatopancreas were able to activate PPO to some degree. For the in vitro study, both enzymes were quite stable when heated at temperature up to 70 °C but the loss in activities increased with increasing heating time (0-120 s). When Pacific white shrimp were pre-cooked to obtain different core temperatures (50-90 °C), different PPO and protease activities were retained. Higher core temperatures were associated with lower PPO and protease activities, but higher cooking loss. When the shrimp were pre-cooked at 80 °C, the residual PPO and protease activities were 3.9% and 5.4%, respectively and cooking yield of 95.6% was obtained. The resulting pre-cooked shrimp possessed lower melanosis score during 7 days of storage at 4 °C. Thus, pre-cooking of shrimp to obtain a core temperature of 80 °C, with a holding time of 30 s, could prevent the severe cooking loss and lower melanosis during subsequent storage.     

Presence of hemocyanin with diphenoloxidase activity in deepwater pink shrimp (Parapenaeus longirostris) post mortem

Polyphenoloxidase and hemocyanin are two proteins which although very similar perform different physiological functions in crustaceans. This paper reports the presence of hemocyanin with diphenoloxidase activity in deepwater pink shrimp (Parapenaeus longirostris) post mortem. Polyacrylamide gels and specific inhibitors and substrates of mono- and diphenoloxidases were used for purposes of recognition, and MALDI-TOF mass spectrometry for identification. Presumptive polyphenoloxidase was found in an inactive form in cephalothorax following capture, subsequently becoming active during storage. Also in the course of storage, hemocyanin acquired the ability to oxidize diphenols. Ascorbic acid, sodium metabisulphite and tropolone inhibited the prooxidant activity of both presumptive polyphenoloxidase and hemocyanin in the gels. 4-Hexylresorcinol did not avoid the appearance of activity bands in the gel corresponding with hemocyanin, maybe because 4-hexylresorcinol is described as slow-binding inhibitor. The acquired prooxidant activity of hemocyanin following capture is especially important because of the rapid development of melanosis in deepwater pink shrimp during storage.     

Effect of cinnamaldehyde on melanosis and spoilage of Pacific white shrimp (Litopenaeus vannamei) during storage

BACKGROUND: Shrimp is a very perishable product and postmortem changes occur rapidly. Sulfiting agents were once and are still widely used as a preservative in the shrimp industry. However, the application of sulfite in shrimp may pose a risk to human health. Thus development of a natural preservative as a sulfite alternative to extend the shelf life of Pacific white shrimp is urgently needed. RESULTS: The effects of cinnamaldehyde essential oil (1 and 5 g kg^?1) on the shelf life of Pacific white shrimp stored at 4 °C were investigated. As the concentration of cinnamaldehyde increased, residual polyphenoloxidase (PPO) enzyme activity decreased. Kinetic analysis showed that cinnamaldehyde was a noncompetitive inhibitor for the oxidation of L ‐DOPA (L ‐3,4‐dihydroxyphenylalanine) by PPO of Pacific white shrimp. Based on this study, shrimp treated with 5 g kg^?1 cinnamaldehyde possessed the lowest aerobic plate count, total volatile basic nitrogen, and pH values in all treatments after 10 days of storage. According to the results of L*, cinnamaldehyde showed inhibitory activity toward the formation of melanosis. CONCLUSION: Treatment with cinnamaldehyde could improve the sensory properties and extend the shelf life of Pacific white shrimp to 8 days. Therefore, cinnamaldehyde could be used as a promising natural preservative for inhibiting melanosis and preventing the growth of microbes during the chilled storage of Pacific white shrimp. Copyright © 2012 Society of Chemical Industry     

Effect of temporal variation,gender and size on cuticle polyphenol oxidase activity in deep-water rose shrimp (Parapenaeus longirostris)

Seasonal changes and physiological factors related to sex, size and spawning period may alter polyphenol oxidase (PPO) activity in crustacean decapods. Given the undesirable effects that the enzyme has on the marketability of shrimps, the cuticles of the valuable deep-water rose shrimp were examined. Monthly measurements of PPO activity in cuticles of juvenile and adult males and females were recorded for one year, along with sea-surface temperature (SST) and photoperiod. PPO activity was highest during late summer (August and September) and was lowest between February and March. The rate of enzyme activity in males was double that of females, when corrected for time period. Juvenile shrimp had the highest enzyme activity. Under the conditions tested, our results support that PPO assessment should take into account the sex and size as factors that potentially biasing in tissue enzyme distributions.     

Evidence of an active laccase-like enzyme in deepwater pink shrimp (Parapenaeus longirostris)

This paper demonstrates the presence of an active laccase-like enzyme from deepwater pink shrimp (Parapenaeus longirostris) using polyacrylamide gel electrophoresis. This enzyme was found in all anatomical parts of the deepwater pink shrimp, but particularly in the cephalothorax, and became active during the course of storage. Gel staining with laccase-specific substrates such as ADA, DMP and DAB was used to characterize a protein of around 44 kDa as containing laccase activity. The enzyme was inhibited by a specific inhibitor, CTAB. 4-Hexylresorcinol, a specific inhibitor of polyphenoloxidase (PPO), did not inhibit the laccase-like enzyme. Low concentrations of antioxidants ascorbic acid or sodium metabisulphite were sufficient to inhibit the laccase-like enzyme. ABTS and DMP were subsequently used to characterize the enzyme. Given the evidence of this enzyme in deepwater pink shrimp, new melanosis-inhibiting compounds that are suitable for consumption need to be found to complement specific inhibitors of PPO activity.     

Elemental and structural changes associated with white spot formation in sun-dried Pacific white shrimp shells

Structural and elemental properties of dried Pacific white shrimp (WSS) (Litopenaeus vannamei) shell having the white spots were compared with non-white spot shrimp (NWSS) shell. Based on X-ray diffraction (XRD) analysis, both samples showed two characteristic peaks representing chitin. However, WSS sample had two additional major peaks at 2θ of 26.65 and 29.53º, which were related to quartz and calcite, respectively. Scanning electron microscope coupled with energy-dispersive X-ray spectrophotometer (SEM-EDX) mapping showed the movement of various elements towards the exo- and endocuticle. The Raman spectroscopic study confirmed the formation of calcite crystals in the white spots. The looser chitin matrix was obtained for WSS as compared to that of NWSS as depicted in SEM micrographs. Therefore, the white spots developed in the shell were caused by the formation of calcite, which exhibited different structural arrangements and elemental positioning as compared to shrimp shell without white spots.     

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.     

Biochemical intervention of ergothioneine-rich edible mushroom (Flammulina velutipes) extract inhibits melanosis in crab (Chionoecetes japonicus)

We investigated the effects of decreasing phenoloxidase (PO) activity and prophenoloxidase (proPO) gene expression on the inhibition of postharvest melanosis formation in the red queen crab, Chionoecetes japonicus. The cDNA of proPO from hemocytes of C. japonicus was partially cloned and sequenced. Immersion of live crabs in a 1.0% ergothioneine (ESH)-rich mushroom extract (Flammulina velutipes; ME) solution resulted in significant inhibition of haemolymph PO activity and a reduction of the proPO gene expression in hemocytes that consequently controlled melanosis in the crabs during ice storage. Treatments with a 0.05% w/v sodium sulphite solution or a 0.05% w/v 4-hexyl-1,3-benzenediol solution had similar positive effects as the treatment with a 1.0% ME solution in vivo. In vitro experiments showed that authentic l-(+)-ESH inhibited PO activity and decreased proPO gene expression in crab hemocytes. Thus, the application of ESH-rich ME can be a novel alternative to synthetic melanosis-inhibiting agents to control postharvest melanosis in crabs.     

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.     

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.     

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei): Compositions and deterioration as affected by iced storage

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) stored in ice for up to 6 days were extracted and characterised. The extraction yields of lipids from hepatopancreas (10.65–12.64%) were higher than those from cephalothorax (2.59–2.88%). However, no changes in the extraction yield were observed during the storage (p > 0.05). The carotenoid contents of lipids from cephalothorax and hepatopancreas slightly increased within the first 2 and 4 days of iced storage (p < 0.05), respectively, but decreased thereafter (p < 0.05). With increasing storage time, a progressive formation of hydroperoxide was found as evidenced by the increase in the absorbance band at 3600–3200 cm⁻¹ in Fourier transform infrared (FTIR) spectra, and increased peroxide values (PVs) (p < 0.05). The increases in thiobarbituric acid reactive substances (TBARS), p-anisidine value (AnV) and free fatty acid (FFA) content of lipids were noticeable when iced storage time increased (p < 0.05). Those changes indicated that lipid oxidation and hydrolysis occurred in both samples. Phospholipids (PL) were the major components in lipids from cephalothorax (82.51% of total lipids). Nevertheless, lipids from hepatopancreas contained triglyceride (TG) and PL as the dominant components (45.35% and 38.03% of total lipids, respectively). A decrease in the TG content with a concomitant increase in free fatty acid was observed at the end of storage (day 6) (p < 0.05). Decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n-3)) and docosahexaenoic acid (DHA; C22:6(n-3)) were noticeable at day 6 of storage (p < 0.05). Thus, the extended storage time resulted in the enhanced deterioration of extracted lipids.     

Autolysis of Pacific white shrimp (Litopenaeus vannamei) meat: characterization and the effects of protein additives

ABSTRACT:  Autolytic activity of Pacific white shrimp ( Litopenaeus vannamei ) mince in the absence and in the presence of 2.5%NaCl was investigated. Pacific white shrimp mince exhibited the maximum autolytic activity at 35 and 40 °C in the absence and in the presence of 2.5%NaCl, respectively, as evidenced by the highest TCA-soluble peptide content and the greatest disappearance of myosin heavy chain (MHC). The autolysis was more pronounced in the acidic pH values, followed by alkaline pH ranges. Pepstatin A showed the highest inhibition toward autolysis in the acidic condition, revealing that aspartic proteinase was dominant in shrimp muscle. Nevertheless, soybean trypsin inhibitor effectively inhibited the autolysis at neutral and alkaline pH values, suggesting that serine proteinase was present in shrimp mince but contributed to autolysis at a lower extent in shrimp meat. Autolysis in shrimp meat could be inhibited partially by all protein additives, including bovine plasma protein (BPP), egg white (EW), and whey protein concentrate (WPC). The inhibition of autolysis increased when the level of protein additives increased with the concomitant increase in band intensity of MHC retained. WPC and BPP in the range of 2% to 3% exhibited the highest inhibition toward autolysis of shrimp mince.     

Retardation of quality changes of Pacific white shrimp by green tea extract treatment and modified atmosphere packaging during refrigerated storage

The effect of modified atmosphere packaging (MAP) on the quality changes of Pacific white shrimp (Litopenaeus vannamei) treated with or without green tea extract (1 g/L; GTE) in combination with or without ascorbic acid (0.05 g/L; AA) during refrigerated storage of 10 days was investigated. Shrimp without treatment stored under MAP had lowered psychrotrophic bacteria, enterobacteriaceae and H₂S-producing bacteria count (P < 0.05) but similar lactic acid bacteria count (P > 0.05), in comparison with shrimp stored in air (control). The coincidental lowered rate of increase in pH, total volatile base (TVB) content and thiobarbituric acid reactive substances (TBARS) were obtained in shrimp stored under MAP (P < 0.05). However, MAP slightly lowered melanosis formation and improved likeness score to some extent. When shrimp were treated with GTE and stored under MAP, the lower microbiological and chemical changes as well as the lowest melanosis formation were observed, compared to shrimp kept under MAP without treatment and the control (P < 0.05). GTE treatment in combination with MAP could retard chemical changes and melanosis formation, regardless of AA incorporation (P > 0.05). Nevertheless, GTE in combination with AA had higher inhibition on microbial growth and yielded the shrimp with higher likeness, compared with the other treatments (P < 0.05). Therefore, shrimp treated with GTE in combination with AA prior to MAP had the lowest losses in quality during refrigerated storage.     

Inactivation of polyphenol oxidase from Pacific white shrimp by dense phase carbon dioxide

The inactivation of polyphenol oxidase (PPO) from Pacific white shrimp exposed to dense phase carbon dioxide (DPCD) treatment was investigated. PPO activity showed a dramatic loss at 4–25 MPa and 37 °C. At the lower pressure (4–15 MPa), the experimental data of inactivation followed the first-order reaction kinetic model, the pressure sensitivity (Z_P) of the kinetic parameters was 49.02 MPa and the activation volume (△ V^≠) was − 120.88 cm³/mol. At the higher pressure (20 and 25 MPa), the experimental data of inactivation followed the biexponential kinetic model. The kinetic rate constant k_F and k_S of fast and stable fractions were 2.45 and 0.08 min^{− 1}, respectively. The decimal reduction time D_F and D_S were 0.94 and 29.43 min at 25 MPa and 37 °C, respectively. After DPCD treatment, the loss activity of PPO had no restoration storing for 6 days at 4 °C. The results of SDS-PAGE and activity staining also showed that DPCD treatment had the obvious inhibitory effect on PPO from Pacific white shrimp. The PPO activity in vivo was easier to be inactivated than that in crude PPO extracts under the same DPCD treatment conditions.

Industrial relevance

There is a growing interest in non-thermal pasteurization methods, which could retain food's freshlike physical, nutritional, and sensory qualities. Pacific white shrimp accounts for 90% of the global aquaculture shrimp production, they are becoming increasingly popular. However, enzymatic browning of shrimp has been of great concern to food scientists and food processors. Dense phase carbon dioxide (DPCD) may be an adequate tool to obtain high quality since PPO activity could not be inactivated totally by high pressure under 400 MPa yet. The present work deals with the inactivation of PPO from Pacific white shrimp exposed to DPCD treatment in order to explore the feasibility of shrimp by DPCD process.     

Nutritional value of cowpea (Vigna unguiculata L. Walp) meals as ingredients in diets for Pacific white shrimp (Litopenaeus vannamei Boone)

The nutritional value of cowpea (Vigna unguiculata L. Walp) meals, as ingredients in diets for Litopenaeus vannamei, was evaluated. Five experimental meals were prepared in the laboratory: whole raw cowpea (WRC), dehulled (DC), cooked (CC), germinated (GC) and extruded (EXC). The crude protein content of WRC (26.1%) increased after germination (29.5%). Carbohydrates ranged from 69.4% to 85.9%. The trypsin inhibitor activity of WRC meal was low (7.52 U/mg dry matter), and was reduced or eliminated by cooking and extrusion. Apparent digestibility of dry matter, protein and carbohydrate of the diet containing whole raw cowpea meal (71.1%, 85.9% and 76.7%, respectively) was similar to the control diet. Cooking and extruding of cowpea significantly increased dry matter, protein and carbohydrate digestibility in the diets. The results suggest that cowpea meals are good sources of nutrients and can be used as ingredients in diets for L. vannamei.