Aggregation and conformational change of mushroom (Agaricus bisporus) polyphenol oxidase subjected to atmospheric cold plasma treatment

ANN-GA optimized composite color protectant combined with magnetic field assisted freezing: Effects on the quality of mushroom (Agaricus bisporus)

Due to their high water content, frozen mushrooms (Agaricus bisporus) were greatly affected by ice crystal formation, which can lead to the destruction of tissue structure, serious browning, high juice loss, and difficulty in maintaining good sensory characteristics. In order to improve the quality of frozen Agaricus bisporus, this study employed Artificial neural network and genetic algorithm (ANN-GA) to optimize the amount of composite color protectant, and identified the optimal freezing conditions for freezing Agaricus bisporus by determining the freezing curves under different magnetic field-assisted freezing conditions, the color variance, texture and structure, drip loss, and distribution of moisture. Furthering, using X-ray μCT three dimensional images were taken to characterize the microstructure of the samples. Among them, the 6 mT magnetic field-assisted freezing treatment group was significantly better than the control group, and the results showed that the magnetic field-assisted freezing combined with chemical color protectant as a composite processing technology improved the quality of frozen Agaricus bisporus. This provides a theoretical basis and technical support for enhanced processing of frozen Agaricus bisporus.

Effects of cold atmospheric plasma pre-treatment on maintaining the quality of ready-to-eat drunken red shrimp (Solenocera crassicornis) stored at chilled conditions

This present study investigated the effect of cold atmospheric plasma (CAP) pre-treatment on the quality of ready-to-eat drunken red shrimp (Solenocera crassicornis) during chilled storage. The shrimp were pre-treated with the CAP at 40 kV and 36 kH for 100 s in a plasma generating equipment before the drunken treatment and compared with an untreated control sample. The results showed that the CAP pre-treatment significantly inhibited the total viable count (TVC) values, total volatile basic nitrogen (TVB-N) content, and polyphenol oxidase (PPO) activity of the drunken shrimp compared to the control treatment. Furthermore, the CAP pre-treatment also significantly maintained the myofibrillar protein (MP) content, texture properties, and a more stable histological structure of muscle fibers compared to the control. High-throughput sequencing results confirmed that the CAP pre-treatment significantly reduced the diversity and abundance of several bacteria in the shrimp. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis detected that the CAP pre-treatment effectively maintained the stability of volatile organic compounds (VOCs). These findings provide valuable theoretical support for the processing and storage of drunken shrimp.

Mechanism of Cold Plasma Combined with Glycation in Altering IgE-Binding Capacity and Digestion Stability of Tropomyosin from Shrimp

Tropomyosin (TM) is a major crustacean allergen, and the present studies have tried to reduce its allergenicity by processing technologies. However, most research stopped on the allergenicity and structure of allergens, while information about epitopes was less. In this study, we first investigated the effects of cold plasma (CP) combined with glycation (CP-G) treatment on the processing and trypsin cleavage sites of TM from shrimp (Penaeus chinensis). The results showed a significant reduction in the IgE-binding capacity of TM after CP-G treatment, with a maximum reduction of 30%. This reduction was associated with the combined effects: modification induced by CP destroyed the core helical structure (D137 and E218) and occupied the potential glycation sites, leading to sequent glycation on conserved areas of TM, especially the epitope L130-Q147. Additionally, CP-G treatment decreased the digestion stability of TM by increasing the number of cleavage sites of trypsin and improving the efficiency of some sites, including K5, K6, K30, and R133, resulting in a lower IgE-binding capacity of digestion products, which fell to a maximum of 20%. Thus, CP-G is a valuable and reliable processing technology for the desensitization of aquatic products.

Inhibition Mechanism of Chitooligosaccharide-Polyphenol Conjugates toward Polyphenoloxidase from Shrimp Cephalothorax

Crustaceans are perishable with a short shelf-life. They are prone to deterioration after capture, particularly during handling, processing, and storage due to melanosis caused by polyphenoloxidase (PPO). Therefore, inhibitory effects of chitooligosaccharide (CHOS) in comparison with CHOS-catechin (CHOS-CAT), CHOS-epigallocatechin gallate (CHOS-EGCG), and CHOS-gallic acid (CHOS-GAL) conjugates on Pacific white shrimp cephalothorax PPO were studied. IC₅₀ of CHOS-CAT (0.32 mg/mL) toward PPO was less than those of all conjugates tested (p < 0.05). CHOS-CAT exhibited the mixed-type inhibition. K_ic (0.58 mg/mL) and K_iu (0.02 mg/mL) of CHOS-CAT were lower than those of other conjugates (p < 0.05). CHOS-CAT showed static fluorescence-quenching, suggesting a change in micro-environment around the active site of PPO. Moreover, CHOS-CAT was linked with various amino acid residues, including Tyr208 or Tyr209 of proPPO via van der Waals, hydrophobic interaction, and hydrogen bonding as elucidated by the molecular docking of proPPO. Although CHOS-CAT had the highest PPO inhibitory activity, it showed a lower binding energy (-8.5 kcal/mol) than other samples, except for CHOS-EGCG (-10.2 kcal/mol). Therefore, CHOS-CAT could act as an anti-melanosis agent in shrimp and other crustaceans to prevent undesirable discoloration associated with quality losses.

Current and Potential Applications of Atmospheric Cold Plasma in the Food Industry

The cost-effectiveness and high efficiency of atmospheric cold plasma (ACP) incentivise researchers to explore its potentials within the food industry. Presently, the destructive nature of this nonthermal technology can be utilised to inactivate foodborne pathogens, enzymatic ripening, food allergens, and pesticides. However, by adjusting its parameters, ACP can also be employed in other novel applications including food modification, drying pre-treatment, nutrient extraction, active packaging, and food waste processing. Relevant studies were conducted to investigate the impacts of ACP and posit that reactive oxygen and nitrogen species (RONS) play the principal roles in achieving the set objectives. In this review article, operations of ACP to achieve desired results are discussed. Moreover, the recent progress of ACP in food processing and safety within the past decade is summarised while current challenges as well as its future outlook are proposed.

Effects of cold atmospheric plasma on endogenous enzyme activity and muscle protein oxidation in Trachinotus ovatus

In this study, we investigated the effects of cold atmospheric plasma (CAP) technology on endogenous enzyme characteristics and muscle protein properties of the golden pomfret (Trachinotus ovatus) under different treatment power and time conditions. Results showed that the enzymatic activity of cathepsin B, L, and calpain in crude protease extracts (CPE) decreased significantly as the treatment power and treatment time of CAP increased (p < 0.05). Oxidative degradation of the CPE after exposure to CAP resulted in significant changes in the structure, total sulfhydryl, and carbonyl content of the CPE (p < 0.05). CAP of an appropriate intensity resulted in significant improvements in the color parameters, hydration properties, and textural property parameters of muscle proteins (p < 0.05). These results suggest that CAP, as a non-thermophysical modification technique, can inhibit the activity of endogenous enzymes as well as alter the protein function in food.

Anti-browning and antibacterial dual functions of novel hydroxypyranone-thiosemicarbazone derivatives as shrimp preservative agents: Synthesis, bio-evaluation, mechanism, and application

To develop new shrimp preservative agents with dual functions of anti-browning and antibacterial, thirteen hydroxypyranone-thiosemicarbazone derivatives were prepared according to molecular hybridization. Thereinto, compound 7j (IC₅₀ = 1.99 ± 0.19 μM) shown the strongest anti-tyrosinase activity and was about twenty-three folds stronger than kojic acid (45.73 ± 4.03 μM). The anti-tyrosinase mechanism of 7j was illustrated through enzyme kinetic, copper ion chelating ability, fluorescence quenching, ultraviolet spectrum, AFM analysis, and molecular docking study. On the other hand, antibacterial assay and time-kill kinetics analysis confirmed that 7j also had good antibacterial activity against V. parahaemolyticus (MIC = 0.13 mM). PI uptake test, SDS-PAGE, and fluorescence spectrometry analysis proved that 7j can affect the bacterial cell membrane. Finally, the shrimp preservation and safety study indicated that 7j has dual effects of inhibiting bacterial growth and preventing enzyme browning, and can be applied to the preservation of fresh shrimp.

Enzymatic browning and polyphenol oxidase control strategies

Significant amounts of fresh and fresh-cut fruits and vegetables are wasted every year due to enzymatic browning. Polyphenol oxidase (PPO) is the key enzyme involved in the enzymatic browning. In the past decades, various methods have been developed to inhibit browning of various fresh produce items. However, for most fresh horticultural produce, ideal measures accepted by industries and consumers are still scarce. This review provides up-to-date knowledge of browning control technologies, including physical methods, chemical methods such as natural inhibitors, molecular biotechnology, and nanotechnology. In addition, we propose some ideas to improve the efficacies of these strategies with fewer side effects. To better inhibit tissue browning, new research directions are also discussed, for example, regulation of PPO substrate techniques.

Assessment of flavor characteristics in snakehead (Ophiocephalus argus Cantor) surimi gels affected by atmospheric cold plasma treatment using GC-IMS

The gel formation ability of freshwater surimi is weak, resulting in its poor flavor and quality. Atmospheric cold plasma (ACP), a widely developed non-thermal processing technology in the food industry, is considered to have potential applications in maintaining and improving the flavor characteristics of surimi gels. In this study, the effect of ACP on snakehead surimi gels flavor at different treatment times was investigated by sensory evaluation and gas chromatography-ion mobility spectrometry (GC-IMS) analysis. The results showed that ACP could better maintain and improve the original appearance and tissue state characteristics of surimi gels, scoring about 1-2 points higher than the ACP-untreated group. GC-IMS analysis demonstrated the obvious difference in the volatile organic compounds (VOCs) among the treatment groups. Specifically, the samples treated for 120 s with ACP exhibited the most unique aroma characteristics, which probably related to the highest thiobarbituric acid reactive substances values (73.28 μmol MDA/kg sample). Meanwhile, the reduced TCA-soluble peptides content indicated that ACP could inhibit protein degradation to maintaining the tissue state and flavor characteristics of the surimi gels. In conclusion, the advantages of ACP treatment, such as little damage to nutrients, and maximum retention of original sensory properties, provide new ideas for its application in the flavor characteristics of the snakehead surimi gels.

Changing the IgE Binding Capacity of Tropomyosin in Shrimp through Structural Modification Induced by Cold Plasma and Glycation Treatment

Tropomyosin (TM) is the major allergen of shrimp (Penaeus chinensis). Previous studies showed that separate cold plasma or glycation have their drawback in reducing allergenicity of TM, including effectiveness and reliability. In the current study, a new processing combining cold plasma (CP) and glycation was proposed and its effect on changing IgE binding capacity of TM from shrimp was investigated. Obtained results showed the IgE binding capacity of TM was reduced by up to 40% after CP (dielectric barrier discharge, 60 kV, 1.0 A) combined with glycation treatment (4 h, 80 °C), compared with the less than 5% reduction after single CP or glycation treatment. Notably, in contrast to the general way of CP prompting glycation, this study devised a new mode of glycation with ribose after CP pretreatment. The structural changes of TM were explored to explain the decreased IgE binding reactivity. The results of multi-spectroscopies showed that the secondary and tertiary structures of TM were further destroyed after combined treatment, including the transformation of 50% α-helix to β-sheet and random coils, the modification and exposure of aromatic amino acids, and the increase of surface hydrophobicity. The morphology analysis using atomic force microscope revealed that the combined processing made the distribution of TM particles tend to disperse circularly, while it would aggregate after either processing treatment alone. These findings confirmed the unfolding and reaggregation of TM during combined processing treatment, which may result in the remarkable reduction of IgE binding ability. Therefore, the processing of CP pretreatment combined with glycation has the potential to reduce or even eliminate the allergenicity of seafood.