Mechanism of color change in Antarctic krill oil during storage.

Antarctic krill oil (AKO) is reddish-orange in color but undergoes changes during storage. To investigate the color deterioration and potential mechanisms involved, the changes in color, endogenous components (astaxanthin, fatty acids, and phospholipids), and reaction products (aldehydes, α-dicarbonyl compounds, and pyrroles) of AKO upon storage were determined. Although the visual color of AKO tended to darken upon storage, the colorimetric analysis and ultraviolet-visible spectrum analysis both indicated a fading in red and yellow due to the oxidative degradation of astaxanthin. During storage of AKO, lipid oxidation led to the formation of carbonyl compounds such as aldehydes and α-dicarbonyls. In addition, phosphatidylethanolamines (PEs) exhibited a faster loss rate than phosphatidylcholines. Moreover, hydrophobic pyrroles, the Maillard-like reaction products associated with primary amine groups in PEs accumulated. Therefore, it is suggested that the Maillard-like reaction between PEs and carbonyl compounds formed by lipid oxidation contributed to color darkening of AKO during storage.

Effect of boiling on texture of scallop adductor muscles and its mechanism based on label-free quantitative proteomic technique.

The mechanism behind textural changes in scallop adductor muscle during boiling was investigated through proteomic analysis, determination of water holding capacity (WHC) and oxidative indices, as well as observation with scanning electron microscopy and multiphoton nonlinear optical microscopy. The hardness and shear force showed the trend of first rising and then falling in 45 min-boiling time. The results suggested that short-time boiling caused the oxidation, denaturation and aggregation of proteins, resulting in the transverse contraction of myofibers and lateral cross-linked aggregation of muscle fibers and a rise in WHC, which led to the increase in hardness and shear force. While long-time boiling caused the progressive degradation of structural proteins such as fibrillin-1, collagen alpha-2(I) chain, myosin heavy chain, basement membrane-specific heparan sulfate proteoglycan core protein, and paramyosin, resulting in a loose myofibril network and the decrease in WHC, which led to the decrease in hardness and shear force.

Differences in texture and digestive properties of different parts in boiled abalone muscles.

Differences in texture and digestive properties of different parts in 80 °C-boiled abalone muscle (adductor and transition part) after different processing time were investigated. With the extension of boiling time, the shear force and hardness of adductor increased first (6 min) and then decreased (30 min and 240 min), while the two indexes of transition part dramatically decreased after boiling for 6 min and then maintained until 240 min. Meanwhile, for adductor, the degree of protein hydrolysis, protein digestibility, and peptide transport levels declined with the extension of boiling time; While for transition part, those protein digestion and transport indexes significantly decreased first (6 min and 30 min) and then increased (240 min). By contrast, the adductor contained higher myofibrillar proteins content but lower collagen content than the transition part, which contributed to the differences in texture and digestive properties of the boiled samples.

High-intensity ultrasound improved the physicochemical and gelling properties of Litopenaeus vannamei myofibrillar protein.

The effects of high-intensity ultrasound on the physicochemical and gelling properties of Litopenaeus vannamei (L. vannamei) myofibrillar protein (MP) were investigated. MP solutions were subjected to ultrasound treatment (power 100 W, 300 W, and 500 W). It was found that the carbonyl and free amino contents of MP increased significantly with increasing ultrasound power, accompanied by enhanced emulsification properties. The increase of free radical and carbonyl content indicated that ultrasound induced the oxidation of MP. With the increase of ultrasound power, it was found that the total sulfhydryl content of the shrimp MP decreased, but the surface hydrophobicity increased significantly, which might be closely related to the conformational changes of MP. Meanwhile, a significant increase of ß-sheet but a decrease of α-helix in the secondary structure of MP was observed with increasing ultrasound power, indicating that ultrasound treatment induced the stretching and flexibility of MP molecules. SDS-PAGE showed that L. vannamei MP consisted of myosin heavy chain, actin, myosin light chain, paramyosin and tropomyosin. Ultrasound treatment could lead to some degree of oxidative aggregation of MP. The results of rheological properties indicated that ultrasound treatment enhanced the viscoelasticity of MP and further improved the gel strength of MP gel. This study can provide a theoretical basis for the functional modification of shrimp MP and the processing of its surimi products.

Study on Dynamic Progression and Risk Assessment of Metabolic Syndrome Based on Multi-State Markov Model.

Aim: Metabolic syndrome (MetS) coexists with the occurrence and even death of cardiovascular disease and diabetes mellitus. It is essential to study the factors in the dynamic progression of MetS in the interest of prevention and control. Purpose: The aim of this study was to analyze the dynamic progression of Mets and explore the potential factors influencing the progression or reversal of MetS. Patients and Methods: This study involved 5581 individuals from two waves of the China Health and Retirement Longitudinal Study: 2011 and 2015. A multistate Markov model containing 4 states (free of metabolic disorder (FMD), mild metabolic disorder (MMD), severe metabolic disorder (SMD) and MetS) was adopted to study the dynamic progression of MetS and its influencing factors. Results: After follow-up, a total of 2862 cases (50.28% of the total number) had disease state transition. The intensity of transition from MetS to SMD is the same as that from SMD to MMD, and is greater than that from MMD to Mets (0.06 vs 0.05). For the MetS state, a mean of 1/0.08=12.5 years was spent in the MetS state before recovery. The exercise, smoke, drink, BMI level, hyperuricemia had statistically significant effects on progression of MetS status (P<0.05). The obesity or overweight, little exercise, smoke, drink and hyperuricemia increased the risk of forward progression of MetS disease status. There were significant nonmodifiable (age, gender) and modifiable factors (exercise, drink, BMI level, or high HbA1c) associated with reversion of MetS state. Conclusion: The likelihood of progression from MMD to MetS is less likely than that of reversion from MetS to SMD and SMD to MMD. Old females were more resistant to recover from worse states than males. Prevention and intervention measures should be adopted early when MMD or SMD onset occurs.

Effect of phytic acid combined with lactic acid on color and texture deterioration of ready-to-eat shrimps during storage.

To retard the deterioration of texture and color of ready-to-eat (RTE) shrimps during storage, phytic acid (PA) and lactic acid (LA) were used to soak the shrimp prior to cooking. The factors affecting texture (water holding capacity, protein oxidation and degradation, and microstructure) and color (Maillard reaction and lipid oxidation) were determined separately. The free radical and copper ion content were also determined in order to investigate the regulation mechanism of phytic acid and lactic acid on the texture and color of RTE shrimps. It was found that the inhibitor-treated RTE shrimps showed better texture and color properties than the control group, and the compound inhibitor (PA + LA) showed a better inhibition effect than single inhibitor. In addition, PA and LA prevented the oxidation of RTE shrimps by scavenging free radicals and chelating copper ions, which in turn enabled the regulation of color and texture deterioration.

Effects of Boiling Processing on Texture of Scallop Adductor Muscle and Its Mechanism.

The objective of this study was to reveal the effects of boiling processing on the texture of scallop adductor muscle (SAM) and its mechanism. Compared to the fresh sample, all the texture indicators, including the hardness, chewiness, springiness, resilience, cohesiveness, and shear force of 30-s- and 3-min-boiled SAMs increased time-dependently (p < 0.05). As the boiling time increased further to 15 min, the shear force and cohesiveness still increased significantly (p < 0.05), and the resilience and hardness were maintained (p > 0.05), but the springiness and chewiness decreased significantly (p < 0.05). The overall increase in the texture indicators of the boiled SAMs was due to the boiling-induced protein denaturation, aggregation, and increased hydrophobicity, resulting in the longitudinal contraction and lateral expansion of myofibrils, the longitudinal contraction and lateral cross-linked aggregation of muscle fibers, and the loss of free water. However, the decreasing springiness and chewiness of the 15-min-boiled SAMs was due to the significant degradation of proteins (especially collagen), resulting in the destruction of the connective tissue between the muscle fiber clusters. Both from a subjective sensory point of view and from the objective point of view of protein denaturation and degradation, 3-min-boiled SAMs are recommended. The quality improvement of thermally processed products by controlled, moderate cooking is of practical value from the perspective of food consumption.

Effect of different sous-vide cooking conditions on textural properties, protein physiochemical properties and microstructure of scallop (Argopecten irradians) adductor muscle.

Among 26 sous-vide cooking conditions of scallop adductor muscle (SAM), 65 °C-5.5 h, 70 °C-1.5 h and 100 °C-5 min were selected by the differential scanning calorimetry analysis. After sous-vide cooking, the shear force, hardness, springiness, cohesiveness, chewiness and recoverability of SAM increased significantly compared to fresh sample. The cooking also changed the secondary structures of the proteins in SAM with the rising ß-sheet and descending α-helix, and the chemical interactions with the rising hydrophobic interactions and disulfide bonds but the descending ionic bonds and hydrogen bonds. These caused the longitudinal shrinkage and transverse aggregation of muscle fibers, and the aggregation and cross-linking between myofibrils which led to the squeeze of immobile water from myofibril network structure. This indicated that the denaturation, oxidation, aggregation and cross-linking of proteins caused by heat treatment changed the microstructure and water distribution, which contributed to the increased textural indicators of sous-vide cooked SAM.

Effect of boiling on texture of abalone muscles and its mechanism based on proteomic techniques.

The precise mechanism of texture changes in abalone muscles during boiling was investigated using quantitative proteomic analysis. A total 353 water-soluble proteins were identified in fresh abalone muscle. The number was decreased to 233 (6 min) and 201 (30 min), and then increased to 271 (240 min) during boiling. The undetectable protein in water-soluble fraction caused by boiling mainly belong to hemocyanins, protein kinases, dehydrogenases, phosphorylases, and transferases, while the newly identified proteins in water-soluble fraction during boiling mainly belong to collagen and myofibrillar proteins (MPs).Additionally, results also showed that boiling caused protein oxidation, denaturation, aggregation, crosslinking and degradation. Combined with the texture changes of abalone muscles during boiling, it was speculated that the oxidation, denaturation, aggregation and crosslinking of proteins led to the increase of shear force, however, the degradation of structural proteins such as MPs and collagen caused the decreases in shear force and hardness.

Effects of antioxidants of bamboo leaves on protein digestion and transport of cooked abalone muscles.

The effects of oxidation on protein digestion and transport in cooked abalone muscles were investigated using a combination of simulated digestion and everted-rat-gut-sac models for the first time. Boiling heat treatments caused protein oxidation in the abalone muscles, reflected by increases in the carbonyl group and disulfide bond contents, protein hydrophobicity and aggregation degree, as well as decreases in the free sulfhydryl group and amino acid contents. Protein oxidation significantly inhibited the degree of hydrolysis, digestion rate, and digestibility of the abalone muscles in the simulated digestion model. The results from the everted-rat-gut-sac model showed that amino acid and peptide transport levels from the digestion products of the cooked abalone muscles were lower than those of the uncooked samples. In contrast, the addition of antioxidants of bamboo leaves mitigated heat-treatment-induced protein oxidation, aggregation and increased hydrophobicity, and consequently improved abalone muscle protein digestibility and transport levels.

Combined effects of ultrasound and antioxidants on the quality maintenance of bay scallop (Argopecten irradians) adductor muscles during cold storage.

The combined effects of ultrasound and the antioxidants of bamboo leaves (AOB) on the quality maintenance of the adductor muscle of scallops (AMSs) during cold storage was investigated. Ultrasound power at 350 W coupled with AOB solution (2% w/v) (UAOB-350) was applied to treat the AMSs according to Taylor diagram analysis. The microstructure, oxidative changes (lipid and protein oxidation), total numbers of colonies, total volatile basic nitrogen, and texture of the AMSs during 6 days of cold storage were analysed. The results indicated that UAOB-350 treatment could effectively retard protein and lipid oxidation and bacterial growth and maintain better microstructure and texture characteristics than AOB solution treatment alone, prolonging the shelf life of the AMSs by 2 days during storage at 4 °C. These results indicate that the UAOB-350 combination method has promising potential to maintain the quality and extend the shelf life of AMSs during cold storage.

Effect of hydroxyl radical induced oxidation on the physicochemical and gelling properties of shrimp myofibrillar protein and its mechanism.

Protein oxidation is considered as an important factor affecting the texture quality of surimi. In this work, the myofibrillar protein (MP) from shrimp (Penaeus vannamei) was subjected to a hydroxyl radical generating system at various concentrations of H2O2, to simulate the oxidative environment during surimi processing. After the hydroxyl radical oxidation, it was found that the carbonyl content, surface hydrophobicity, and MP aggregation increased. Meanwhile, the a-helix decreased, but ß-sheet increased after oxidation. The moderate oxidation led to a dense network microstructure, increased water holding capacity (WHC) and decreased water mobility, which ultimately enhanced textural (hardness and springiness increased by 0.51- and 0.06-fold, respectively) and rheological properties of MP gel (MPG). However, excessive oxidation could reduce the mechanical properties of MPG. The microstructure, WHC and water distribution played a key role in the mechanical properties of MPG. This study can provide a theoretical basis for processing of shrimp surimi products.

Genetic Variation of Migration Inhibitory Factor Gene rs2070766 Is Associated With Acute Coronary Syndromes in Chinese Population.

Genetic variation of macrophage migration inhibitory factor (MIF) gene has been linked to coronary artery disease. We investigated an association between the polymorphism of MIF gene rs2070766 and acute coronary syndromes (ACS) and the predictive value of MIF gene variation in clinical outcomes. This study involved in 963 ACS patients and 932 control subjects from a Chinese population. All participants were genotyped for the single nucleotide polymorphism (SNP) of MIF gene rs2070766 using SNPscan™. A nomogram model using MIF genetic variation and clinical variables was established to predict risk of ACS. Major adverse cardiovascular events (MACE) were monitored during a follow-up period. The frequency of rs2070766 GG genotype was higher in ACS patients than in control subjects (6.2 vs 3.8%, p = 0.034). Multivariate logistic regression analysis revealed that individuals with mutant GG genotype had a 1.7-fold higher risk of ACS compared with individuals with CC or CG genotypes. Using MIF rs2070766 genotypes and clinical factors, we developed a nomogram model to predict risk of ACS. The nomogram model had a good discrimination with an area under the curve of 0.781 (95% CI: 0.759-0.804), concordance index of 0.784 (95% CI: 0.762-0.806) and well-fitted calibration. During the follow-up period of 25 months, Kaplan-Meier curves demonstrated that ACS patients carrying GG phenotype developed more MACE compared to CC or CG carriers (p < 0.05). GG genotype of MIF gene rs2070766 was associated with a higher risk of ACS in a Chinese population. The GG genotype carriers in ACS patients had worse clinical outcomes compared with those carrying CC or CG genotype. Together with rs2070766 genetic variant of MIF gene, we established a novel nomogram model that can provide individualized prediction for ACS.

Differences in oxidative susceptibilities between glycerophosphocholine and glycerophosphoethanolamine in dried scallop (Argopecten irradians) adductor muscle during storage: an oxidation kinetic assessment.

BACKGROUND: Phospholipids, the main lipid component in marine shellfish, mainly comprise glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE). GPC and GPE in marine shellfish, especially scallop, carry n-3 long-chain polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), although different types of glycerophospholipids (GP) have different health benefits on human health. Moreover, different GP subclasses such as GPC and GPE have different oxidative susceptibilities in complex food systems. The present study compared the oxidative susceptibilities of GPC and GPE in dried scallop during storage by high-performance liquid chromatography-tandem mass spectrometry and kinetic models, and also investigated the effects of natural phenolic antioxidant on their susceptibilities. RESULTS: The results showed that GPC and GPE molecular species (carrying EPA or DHA) contents in samples continuously reduced during storage at two different temperatures. The first-order kinetic model better reflected the changes of GPC and GPE molecular species (carrying EPA or DHA) in samples than the zero-order kinetic model during storage. According to the oxidation rate (k) obtained from first-order kinetic models, GPE possessed a greater oxidation rate than GPC during storage. Moreover, the results showed that antioxidants of bamboo leaves (AOB, polar polyphenolic antioxidants) significantly decreased the oxidation rates of GPC and GPE molecular species (carrying EPA or DHA) in samples during storage, and GPC could be more effectively protected by AOB compared to GPE. CONCLUSION: The present study provides a practical method for accurately evaluating the oxidative susceptibility of different phospholipid classes in complex food systems. © 2020 Society of Chemical Industry.

Effect of protein oxidation and degradation on texture deterioration of ready-to-eat shrimps during storage.

The impact of protein oxidation and degradation on texture deterioration of ready-to-eat (RTE) shrimps during storage was investigated. The deterioration in texture during storage was manifested by decreased instrumental hardness, elasticity, chewiness, and recoverability. The occurrence of protein oxidation was revealed by a significant increase in the contents of free radicals and carbonyls. The increases in trichloroacetic acid-soluble peptide (TCA-soluble peptide) content and myofibril fragmentation index (MFI) were also observed, suggesting the degradation of protein. Pearson correlation analysis showed that the decreased instrumental texture parameters were negatively correlated with the increased carbonyl content, TCA-soluble peptide, MFI, porosity, and pore size as well as the decreased water-holding capacity (WHC), thus, it was hypothesized that protein oxidation and degradation were responsible for changes in the microstructure and reduction of WHC, which ultimately resulted in texture deterioration of RTE shrimps.

Effects of proteolysis and oxidation on mechanical properties of sea cucumber (Stichopus japonicus) during thermal processing and storage and their control.

The effects of endogenous proteolysis and oxidation on mechanical properties of sea cucumber (Stichopus japonicus) during thermal processing and storage and their control were investigated. The lactic acid (LA) + tea polyphenols (TP)-treated sea cucumbers showed relatively higher values in texture and rheological indicators than the blank control group after thermal processing. By contrast, the (LA + TP)-treated sea cucumbers also had lower values in water-soluble hydroxyproline, glycosaminoglycans and proteins, trichloroacetic acid-soluble peptide content, and more orderly secondary structure of proteins, indicating that the additives affected the mechanical properties of thermally processed sea cucumbers by preventing the proteolysis of proteins. All texture and rheological indicators of thermally processed sea cucumbers decreased time-dependently during chilled storage. The additives (LA + TP) significantly prevented the progressive deterioration in mechanical properties by retarding the changes in microstructure as well as phase state and distribution of water through preventing protein oxidation.

MIF -173G/C (rs755622) polymorphism modulates coronary artery disease risk: evidence from a systematic meta-analysis.

BACKGROUND: Coronary artery disease (CAD) remains one of the major causes of death in humans. Genetic testing may allow early detection and prevention of this disease. This study aimed to investigate the association between the macrophage migration inhibitory factor (MIF) -173G/C (rs755622) polymorphism and susceptibility to CAD based on a meta-analysis. METHODS: We searched several databases to identify observational case-control studies investigating the association between the MIF -173G > C (rs755622) polymorphism and CAD risk published before July 30, 2019. Data were analyzed using the STATA software. RESULTS: Six studies, comprising a total of 1172 CAD cases and 1564 controls evaluated for MIF polymorphisms, were included. The occurrence of CAD was found to be associated with the C allele of the MIF rs755622 SNP in the total population (C/G, OR = 1.489, 95% CI = 1.223-1.813). Further, MIF -173G/C polymorphism was significantly associated with CAD under the allelic model in the Asian (C/G, OR = 1.775, 95% CI = 1.365-2.309) and Caucasian (C/G, OR = 1.288, 95% CI 1.003-1.654) subgroups. The data showed that the risk of CAD was higher in the population carrying the C allele. CONCLUSIONS: We found evidence of associations between MIF -173C/G and CAD susceptibility in the Asian and Caucasian populations.

Action of endogenous proteases on texture deterioration of the bay scallop (Argopecten irradians) adductor muscle during cold storage and its mechanism.

Texture deterioration occurs in adductor muscle of scallop (Argopecten irradians) (AMS) after 5 d of cold storage. Principal component analysis indicated the texture deterioration resulted in significant decrease of hardness, springiness, adhesiveness and chewiness, but significantly increased cohesiveness. Endogenous proteases degraded structural proteins, among which cysteine proteases were mainly responsible for myofibrillar proteins (MPs) degradation, while serine proteases degraded both MPs and connective tissue proteins. Pearson coefficient analysis showed that texture indicators significantly correlated with structural protein indicators in AMS. To be more specific, the hardness, springiness, adhesiveness and chewiness negatively correlated with myofibrillar fragmentation index, soluble hydroxyproline (Hyp) and soluble glycosaminoglycans, but positively correlated with solubility of MPs and water holding capacity. Meanwhile, the cohesiveness positively correlated with soluble Hyp. The Taylor diagram and Hierarchical cluster analysis confirmed that the inhibitors of cysteine and serine proteases could effectively retard textural deterioration of AMS during 5 d of cold storage.

Impact of different drying processes on the lipid deterioration and color characteristics of Penaeus vannamei.

BACKGROUND: Fresh shrimp (Penaeus vannamei) deteriorates easily and the drying process is an important processing method for prolonging the shelf life of shrimp. The traditional drying method is hot-air-drying (HD), which can cause some problems such as nutrient loss, discoloration and lipid oxidation. In recent years, freeze-drying (FD) has been popular for removing moisture from food at lower temperatures, maintaining the structure of raw materials, and improving storage stability of products. In the present study, the effects of HD and FD on lipid and color of P. vannamei and the mechanisms involved were investigated. RESULTS: FD caused less lipid oxidation compared to HD; consequently, FD-processed shrimps had lower levels of primary and secondary oxidation products, as well as acid value, and higher contents of triacylglycerol, phosphatidylcholine, phosphatidylethanolamine, eicosapentaenoic acid and docosahexaenoic acid compared to HD-processed samples. Lipase and lipoxygenase played a role in the oxidation and hydrolysis of lipids during drying process. FD-processed shrimps had lower yellowness value and chromatic aberrations but a higher whiteness value compared to HD-processed samples. Correlation analysis showed that lipid oxidation, astaxanthin degradation and the Maillard reaction contributed to the changes of color. Principal component analysis indicated that FD caused less deterioration in quality compared to HD. CONCLUSION: In the present study, FD is recommended for preserving shrimp color and lipid nutrition in terms of lipid oxidation control. © 2020 Society of Chemical Industry.

Effects of temperature and heating time on the formation of aldehydes during the frying process of clam assessed by an HPLC-MS/MS method.

This study aimed at investigating the formation and accumulation of 16 reactive aldehydes in clam (Ruditapes philippinarum) during oil frying in both the tissue and the oil using an HPLC-ESI-MS/MS methodology. After processing, the accumulation of acrolein, crotonaldehyde, pentanal, trans-2-hexenal, hexanal, trans, trans-2,4-heptadienal, heptanal, nonanal, trans, trans-2,4-decadienal and 4-hydroxy-2-nonenal was most noticeable in both fried clam and frying oil. Most of the aldehyde species showed a time- and temperature-dependent manner of formation and accumulation during frying due to continuous oxidative degradation under conditions employed. However, several species of aldehyde such as acrolein and trans-2-pentenal slightly decreased at higher temperatures and/or longer frying times, which may be due to the imbalance toward disappearance of aldehydes resulting from their evaporation under the extreme conditions. Presence of natural polyphenols in bamboo leaves significantly prevented the formation of aldehydes in both fried clam and frying oil due to their antioxidant activity (P < 0.05).