Spraying of 4-hexylresorcinol based formulations to prevent enzymatic browning in Norway lobsters (Nephrops norvegicus) during chilled storage

Effects of a cold plasma-assisted shrimp processing chain on biochemical and sensory quality alterations in Pacific white shrimps (Penaeus vannamei)

In this paper, remodeling the shrimp processing chain and the effects of the transformation on the biochemical and sensory qualities of fresh Pacific white shrimp (Penaeus vannamei) under refrigeration storage were investigated. In the proposed model, a dielectric barrier discharge atmospheric cold plasma pretreatment step using a 60 kV source for 60, 90, 120, and 150 s was introduced after the first and second wash followed by refrigeration storage at 4 ± 1 °C for 12 days. Chemical, biochemical, and sensory attributes of the shrimp were monitored and compared with those of shrimp processed through the traditional method without atmospheric cold plasma pretreatment (control). Incorporating minimal dielectric barrier discharge atmospheric cold plasma pretreatment step had more desirable quality outcomes characterized by low malondialdehyde concentration, low volatile nitrogen products content, and comparable proximate composition. Texture, pH, and color were remarkably retained at 120 and 150 s of atmospheric cold plasma pretreatment and protein degradation was negligible up to 90 s than at 120 and 150 s of pretreatment. We conclude that remodeling the shrimp processing chain through incorporating minimal dielectric barrier discharge atmospheric cold plasma pretreatment with key considerations on operation parameters can maximize the beneficial biochemical and sensory quality outcomes while minimizing the negative impacts associated with traditional shrimp processing.

Quality Evaluation of Shrimp (Parapenaeus longirostris) Treated with Phenolic Extract from Olive Vegetation Water during Shelf-Life, before and after Cooking

The focus of this study was to assess the quality traits and sensory profile of cooked rose shrimps (Parapenaeus longirostris) treated with a phenolic extract, derived from olive vegetation water (PEOVW). To achieve the aim, four different groups of shrimps were analysed, specifically the control (CTRL) group, where the shrimps were soaked in tap water; sulphites (S) group with shrimps soaked in 0.5% sodium metabisulfite tap water solution, phenolic extract (PE) group where a tap water solution containing 2 g/L of phenols was used; and PE+S group where the shrimps were dipped in 0.25% sodium metabisulfite tap water solution containing 1 g/L of phenols. The groups were then stored at 2 °C and analysed on the day of packaging (D0), after 3 (D3), 6 (D6), and 8 (D8) days. On each group, microbiological parameters such as Enterobacteriaceae, mesophilic and psychrotrophic bacteria, and colorimetric indices were investigated on six (n = 6) shrimps before cooking, while the evolution of the phenolic content, antioxidant activity, and sensory analysis during the storage period were evaluated on cooked shrimps. Regarding colour coordinates, there were no noteworthy variations overtime nor between groups, while it is important to note that the microbiological results for the PE group showed at each time interval and for all the considered parameters, significantly lower values than the other groups (p < 0.05). This result is very interesting when considered further in correlation with the sensory analysis, where shrimps mainly in PE and secondarily in PE+S groups were shown to retain the freshness characteristics better than the other groups (α = 0.01), without giving the shrimps any particularly bitter and pungent sensations typical of the olive phenolic compounds. In conclusion, the results obtained in this study give PEOVW the potential to be valorised in the food sector and, above all, it could represent a sustainable solution to reduce the use of synthetic additives.

Halophytes as a potential source of melanosis-inhibiting compounds. Mechanism of inhibition of a characterized polyphenol extract of purslane (Portulaca oleracea)

The market value of crustaceans depreciates during storage due to the appearance of melanosis caused by polyphenol oxidases. Sulfite derivatives are used as melanosis-inhibiting agents, but their unhealthy effects make it preferable to replace them with natural preservatives. In this work, a crude enzymatic extract from whiteleg shrimp (Penaeus vannamei) was characterized and used to test the diphenol oxidase-inhibiting activity of polyphenol extracts of five underutilized halophyte plants, namely crystalline ice plant, seaside arrowgrass, purslane, sea fennel, and seashore aster. The extracts inhibited diphenol oxidase activity more efficiently than sodium sulfite. The purslane extract was rich in isoorientins, isovitexin, and apigenin, and showed the highest inhibiting effect, being this classified as mixed or non-competitive. Hydroxyl groups in the phenyl B ring could be responsible for the inhibitory activity of the extract. The polyphenol extracts tested in this work could be promising melanosis-inhibiting agents of interest for seafood industries.

Effects of metal ions on activity and structure of phenoloxidase in Penaeus vannamei

Phenoloxidase (PO) is a typical metal enzyme, which requires metal ions as prosthetic groups to enable the full exertion of its activity. To study how metal ions affected the activity and structure of PO enzymes, while providing reference materials for in-depth investigations, we examined the effects of different metal ions (Cu²⁺, Zn²⁺, Mg²⁺, Ca²⁺, and Ba²⁺) on their activities. Furthermore, Cu²⁺ and Mg²⁺ were selected for further investigation through UV spectra, intrinsic fluorescence spectroscopy, AFM, and FTIR. It was revealed that Cu²⁺ had a more obvious effect on PO compared to Mg²⁺. The PO could be activated when the concentrations of Cu²⁺ and Mg²⁺ were lower than 10^-3 and 10^-2 mol/L, respectively, and maximum PO activities (182.14% and 141.02%) were observed at 10^-4 mol/L concentrations of Cu²⁺ and Mg²⁺. When the concentrations of Cu²⁺ and Mg²⁺ were higher than 10^-2 and 10^-1 mol/L, the activities PO were inhibited. The results of the UV-vis and fluorescence spectra revealed that Cu²⁺ shaped the tertiary structure of PO, whereas the effect of Mg²⁺ was slight. The AFM results demonstrated that high concentrations of Cu²⁺ and Mg²⁺ resulted in PO aggregation. FTIR analysis indicated that the total content of PO α-helices and β-sheets decreased with higher concentrations of Cu²⁺ and Mg²⁺.

Oxidation evaluation of free astaxanthin and astaxanthin esters in Pacific white shrimp during iced storage and frozen storage

BACKGROUND

In this paper, the changes in free astaxanthin (F-AST) and astaxanthin esters (AST-Es) in Litopenaeus vannamei during iced storage and frozen storage were investigated. The liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry method was used to quantify the molecular species of AST-Es in shrimp during storage.

RESULTS

Based on the analysis of autoxidation products, apo-12-astaxanthinal and apo-13-astaxanthinone docosahexaenoic acid (DHA) ester were identified as the major oxidation products of F-AST and AST-Es in L. vannamei during storage. The total astaxanthin (T-AST) content decreased by 34.51% after 7 days in iced storage. In contrast, the content of T-AST decreased by 43.76% after 12 weeks in frozen storage. The content of F-AST decreased by 29.99% while 13-cis-astaxanthin increased after 3 days in iced storage, which indicated that degradation of AST was accompanied by isomerization. Total volatile basic nitrogen and T-AST content showed a significant negative correlation while in frozen storage, where the concentration of T-AST might be one indicator to evaluate shrimp freshness.

CONCLUSION

The correlation coefficients between phenol oxidase, lipoxygenase, apo-12-astaxanthinal, and apo-13-astaxanthinone DHA ester were all greater than 0.97 (P < 0.01). This correlation indicates that phenol oxidase and lipoxygenase were the main internal factors to improve oxygenation of astaxanthin in L. vannamei. These results provide a theoretical basis for further study of oxidation and the degradation mechanism in astaxanthin, as well as a new idea for the development and utilization of astaxanthin compounds in Pacific white shrimp. © 2018 Society of Chemical Industry.

Angioplasty Using 4-Hexylresorcinol-Incorporated Silk Vascular Patch in Rat Carotid Defect Model

The aim of this study was to evaluate and compare the efficacy of 4-hexylresorcinol (4-HR)-incorporated silk as a vascular patch scaffold to that of the commercial polytetrafluoroethylene (PTFE) vascular patch (GORE® ACUSEAL). The expression of the vascular endothelial cell growth factor-A (VEGF-A) after application of 4-HR was studied in RAW264.7 and HUVEC cells. In the animal study, a carotid artery defect was modeled in Sprague Dawley rats (n = 30). The defect was directly closed in the control group (n = 10), or repaired with the PTFE or 4-HR silk patch in the experimental groups (n = 10 per group). Following patch angioplasty, angiography was performed and the peak systolic velocity (PSV) was measured to evaluate the artery patency. The application of 4-HR was shown to increase the expression of VEGF-A in RAW264.7 and HUVEC cells. The successful artery patency rate was 80% for the 4-HR silk group, 30% for the PTFE group, and 60% for the control group. The PSV of the 4-HR silk group was significantly different from that of the control group at one week and three weeks post-angioplasty (p = 0.005 and 0.024). Histological examination revealed new regeneration of the arterial wall, and that the arterial diameter was well maintained in the 4-HR silk group in the absence of an immune reaction. In contrast, an overgrowth of endothelium was observed in the PTFE group. In this study, the 4-HR silk patch was successfully used as a vascular patch, and achieved a higher vessel patency rate and lower PSV than the PTFE patch.

Shelf life extension of whole Norway lobster Nephrops norvegicus using modified atmosphere packaging

Once a nuisance by-catch, today the Norway lobster (Nephrops norvegicus) is a valuable UK fisheries commodity. Unfortunately, the species is very susceptible to quality deterioration post harvest as it quickly develops black spots and also spoils rapidly due to bacterial growth. Treatment with chemicals can stop the blackening and carefully monitored cold storage can result in a sensory shelf life of up to 6.5 days. The high susceptibility to spoilage greatly restricts the extent to which N. norvegicus can be distributed to retailers and displayed for sale. The application of modified atmosphere (MA) could be extremely beneficial, allowing the chilled product to stay fresh for a long period of time, thus ensuring higher sales. In the present study, we identified a gas mix for the MA packaging (MAP) of whole N. norvegicus lobster into 200 g retail packs. Our results show that a shelf life extension to 13 days can be achieved when retail packs are stored in MAP at 1 °C. Effectiveness of the MAP was evaluated by using a newly developed QIM for MA-packaged whole N. norvegicus and also by analyzing bacterial plate counts. Changes in the microflora and effects of different storage temperatures on the quality of the MA packs are also presented. The main specific spoilage organism (SSO) of modified atmosphere packaged Norway lobster is Photobacterium phosphoreum.