Inactivation effects and kinetics of polyphenol oxidase from Litopenaeus vannamei by ultra-high pressure and heat

Optimizing color enhancement in dried Penaeus vannamei through high-humidity hot air impingement cooking: Enzyme inactivation, reduced drying time, and Maillard reaction inhibition

This study was aimed to evaluate the potential of high-humidity hot air impingement cooking (HHAIC) on Penaeus vannamei, focusing on its drying characteristics, microstructure, water distribution, enzyme activity, astaxanthin content, antioxidant capacity, color, and Maillard reaction. Results demonstrated that a 3 min HHAIC significantly improved the shrimp's color and optimized astaxanthin content with a notable increase in scavenging capacity based on an in-vitro as antioxidation activity evaluation. Compared to the untreated samples, HHAIC could significantly inactivate polyphenol oxidase by 95.76%. Also, it suppressed the Maillard reaction by decreasing 5-hydroxymethylfurfural content and shortened the drying time by 40%. In addition, the low-field nuclear magnetic resonance and microstructure analysis showed alterations in the shrimp muscle fiber structure and water distribution. This study indicated that HHAIC could elevate quality, enhance appearance, and reduce the processing time of dried shrimp, presenting valuable implications for industry progress.

Enzymatic Activity and Its Relationships with the Total Phenolic Content and Color Change in the High Hydrostatic Pressure-Assisted Curing of Vanilla Bean (Vanilla planifolia)

Diverse enzymatic reactions taking place after the killing of green vanilla beans are involved in the flavor and color development of the cured beans. The effects of high hydrostatic pressure (HHP) at 50-400 MPa/5 min and blanching as vanilla killing methods were evaluated on the total phenolic content (TPC), polyphenoloxidase (PPO), and peroxidase (POD) activity and the color change at different curing cycles of sweating-drying (C0-C20) of vanilla beans. The rate constants describing the above parameters during the curing cycles were also obtained. The TPC increased from C1 to C6 compared with the untreated green beans after which it started to decrease. The 400 MPa samples showed the highest rate of phenolic increase. Immediately after the killing (C0), the highest increase in PPO activity was observed at 50 MPa (46%), whereas for POD it was at 400 MPa (25%). Both enzymes showed the maximum activity at C1, after which the activity started to decrease. As expected, the L* color parameter decreased during the entire curing for all treatments. An inverse relationship between the rate of TPC decrease and enzymatic activity loss was found, but the relationship with L* was unclear. HHP appears to be an alternative vanilla killing method; nevertheless, more studies are needed to establish its clear advantages over blanching.

Impacts of high pressure assisted freezing on the denaturation of polyphenol oxidase

The mechanism of enzyme protein denaturation induced by high pressure freezing is complicated and unclear as this process involves Pressure-Factors (pressure and time) and Freezing-Factors (temperature, phase transition, recrystallization, and ice crystal types). In this study, the thermodynamics and conformation changes of mushroom polyphenol oxidase (PPO) under high pressure freezing treatments (HPF, ^{100,150,200,300,400,500MPa}P_-20°C/30min) and high pressure processes (HPP) followed with normal pressure immersion freezing (HPP-IF, ^100-500MPaP_25°C/30min - ^0.1MPaP_-20°C/30min) are investigated as compared with that processed under high pressure processes (HPP, ^100-500MPaP_25°C/30min) and normal pressure immersion freezing process (IF, ^0.1MPaP_-20°C/30min). The results suggested that the treated PPO with the same enzyme activity may have various thermodynamic characteristics and conformations; Pressure-Factors play the main roles in the denaturation of the PPO during the HPF treatment, and Freezing-Factors can weak the effect of Pressure-Factors on PPO denaturation; The treated PPO may be transferred into a partially fold intermediate state.

Effect of low-temperature preservation on quality changes in Pacific white shrimp, Litopenaeus vannamei: a review

Shrimp has been widely accepted as an excellent resource for white meat due to its high-protein and low-fat content, especially low cholesterol. However, shrimps are highly perishable during preservation and retailing procedures due to the activities of enzymatic proteolysis, lipid oxidation, and microbial degradation. With increasing knowledge of and demands for safety, nutrition, and freshness of shrimp products, energy efficient, quality, maintained, and sustainable preservation technologies are needed. Low-temperature preservation, a practical processing method for improving the shelf life of food products, is widely used in the aquatic industry. This review focuses on the effects of low-temperature preservation on the quality changes in Litopenaeus vannamei. It considers physicochemical properties, sensory evaluation, melanosis assessment, and microbiological analysis. The perspectives of non-protein-based techniques on quality analysis of shrimps during preservation are also discussed. © 2019 Society of Chemical Industry.

Effects of Killing Methods on Lipid Oxidation, Colour and Microbial Load of Black Soldier Fly (Hermetia illucens) Larvae

Black soldier fly (BSF) larvae represent a promising alternative ingredient for animal feed. Post-production processing can, however, affect their quality. This project aimed to optimize larval killing by comparing the effects on the nutritional and microbiological quality of 10 methods, i.e., blanching (B = 40 s), desiccation (D = 60 °C, 30 min), freezing (F20 = -20 °C, 1 h; F40 = -40 °C, 1 h; N = liquid nitrogen, 40 s), high hydrostatic pressure (HHP = 3 min, 600 MPa), grinding (G = 2 min) and asphyxiation (CO2 = 120 h; N2 = 144 h; vacuum conditioning, V = 120 h). Some methods affected the pH (B, asphyxiation), total moisture (B, asphyxiation and D) and ash contents (B, p < 0.001). The lipid content (asphyxiation) and their oxidation levels (B, asphyxiation and D) were also affected (p < 0.001). Killing methods altered the larvae colour during freeze-drying and in the final product. Blanching appears to be the most appropriate strategy since it minimizes lipid oxidation (primary = 4.6 ± 0.7 mg cumen hydroperoxide (CHP) equivalents/kg; secondary = 1.0 ± 0.1 mg malondialdehyde/kg), reduces microbial contamination and initiates dehydration (water content = 78.1 ± 1.0%). We propose herein, an optimized protocol to kill BSF that meet the Canadian regulatory requirements of the insect production and processing industry.

Optimization of extraction yield, flavonoids and lycopene from tomato pulp by high hydrostatic pressure-assisted extraction

Tomato pulp is a useful source of antioxidants, which can be extracted by high hydrostatic pressure (HHPE). This study aimed to optimize the individual and interactive effect of operating high pressure and solvent polarity (solvent mixture) on yield extraction, flavonoid and lycopene content from tomato pulp (Solanum lycopersicum) by using response surface methodology (RSM). The results showed that the selected factors (high pressure and solvent mixture) have a significant influence on extraction yield, flavonoid and lycopene content. Extraction at 450 MPa and 60% hexane concentration in the solvent mixture was considered the optimal HHPE condition since it provided the maximum extraction yield (8.71%), flavonoid (21.52 ± 0.09 mg QE/g FW) and lycopene content (2.01 ± 0.09 mg QE/100 g FW). Therefore, HHPE could be a useful tool improve the extraction and release of potentially health-related compounds while providing information on the cumulative effect of solvent polarity and high-pressure extraction on antioxidant compounds of fruits.

Enhanced saccharification of rice straw using combined ultra-high pressure and ionic liquid microemulsion pretreatments

Energy efficiency ratio is significant in completely estimating lignocellulosic biomass pretreatment. In this work, rice straw (RS) was pretreated by ultra-high pressure (UHP), ionic liquid microemulsion (ILM), and a combination of UHP and ILM (ILM + UHP) at mild temperature. The chemical composition, crystalline structure, surface morphology, and enzymatic hydrolysis of untreated and pretreated RS samples were compared. After ILM pretreatment ([Emim]Ac/cyclohexane/Triton X-100/n-butanol = 0.25/0.15/0.45/0.15) at 500 MPa, 50 °C for 4 h, the cellulose content of the regenerated RS increased by 62.5, 66.2% of the lignin was removed, 37.3% of crystallinity index decreased, and the reducing sugar yield of 89.6% was achieved. All results show that the ILM + UHP pretreatments were more effective than sole UHP or ILM treatment at low temperature.

Impact of High Hydrostatic Pressure on the Shelling Efficacy, Physicochemical Properties, and Microstructure of Fresh Razor Clam (Sinonovacula constricta)

The effects of high hydrostatic pressure (HHP) treatments (200, 300, and 400 MPa for 1, 3, 5 and 10 min) on the shelling efficacy (the rate of shelling, the rate of integrity and yield of razor clam meat) and the physicochemical (drip loss, water-holding capacity, pH, conductivity, lipid oxidation, Ca²⁺ -ATPase activity, myofibrillar protein content), microbiological (total viable counts) and microstructural properties of fresh razor clam (Sinonovacula constricta) were investigated. HHP treatments significantly (P < 0.05) increased shelling efficiency, water-holding capacity, pH, conductivity, and lipid oxidation, and HHP-treated razor clam showed lower levels of microorganisms and drip loss than untreated razor clam. Levels of thiobarbituric acid reacting substances (TBA) in HHP-treated razor clam were greatly increased (up to 0.93 ± 0.09 mg MDA/kg at 400 MPa for 10 min) which was caused by the formation of hydroperoxides during HHP treatment. All HHP treatments were found to have adverse effects on the activity of Ca²⁺ -ATPase and the content of myofibrillar protein (MP), which might be due to the substantial damage to the tertiary structure of proteins at high pressure. Moreover, scanning electron microscopy (SEM) revealed the compaction of the muscle fibers and a decrease in the extracellular space with increasing pressure and holding time. This phenomenon was mainly correlated with the compaction of muscle fibers and denaturation, aggregation, and gelation of muscle protein triggered by high pressure. In general, HHP could be applied as a safe and effective nonthermal technology to produce high-quality shelled razor clam.

PRACTICAL APPLICATION

High hydrostatic pressure (HHP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, it has not been widely applied to shell seafood due to its uncertain influence on its quality and shelling property. This study could provide valuable information regarding the shelling efficacy, physicochemical properties, and microstructure of razor clam treated by HHP. And it demonstrated that HHP showed a positive impact on quality of razor clam treated by HHP.

Effect of high hydrostatic pressure on the microbiological, biochemical characteristics of white shrimp Litopenaeus vannamei

Using thermal processing (TP) treatment (100 ℃, 1-8 min) as a control, the effects of high hydrostatic pressure (HHP, 200-500 MPa, 2.5-20 min) on the microbiological and biochemical characteristics of white shrimp Litopenaeus vannamei were investigated. The results showed that the efficiency of polyphenol oxidase (PPO) inactivation and log reduction of total plate count (TPC) by HHP treatment were all significantly lower than by TP treatment (p < 0.05). The rate of inactivation for TPC and PPO all increased with the increase of HHP pressure and holding time (p < 0.05). The inactivation of PPO was in accordance with a first-order kinetics with the HHP treating time. Hardness of HHP-treated samples at the pressure of 300-500 MPa was higher than TP-treated samples, while the yield loss of HHP treatment was significantly lower than with TP treatment (p < 0.05), long time and high pressure of HHP treatment turned the appearance of shrimps slightly pink.