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.

Preparation and Hepatoprotective Activities of Peptides Derived from Mussels (Mytilus edulis) and Clams (Ruditapes philippinarum).

Low molecular weight (<5 kDa) peptides from mussels (Mytilus edulis) (MPs) and the peptides from clams (Ruditapes philippinarum) (CPs) were prepared through enzymatic hydrolysis by proteases (dispase, pepsin, trypsin, alcalase and papain). Both the MPs and the CPs showed excellent in vitro scavenging ability of free radicals including OH, DPPH and ABTS in the concentration range of 0.625−10.000 mg/mL. By contrast, the MPs hydrolyzed by alcalase (MPs-A) and the CPs hydrolyzed by dispase (CPs-D) had the highest antioxidant activities. Furthermore, MPs-A and CPs-D exhibited protective capabilities against oxidative damage induced by H2O2 in HepG2 cells in the concentration range of 25−800 µg/mL. Meanwhile, compared with the corresponding indicators of the negative control (alcohol-fed) mice, lower contents of hepatic MDA and serums ALT and AST, as well as higher activities of hepatic SOD and GSH-PX were observed in experiment mice treated with MPs-A and CPs-D. The present results clearly indicated that Mytilus edulis and Ruditapes philippinarum are good sources of hepatoprotective peptides.

Effects of different antioxidants and their combinations on the oxidative stability of DHA algae oil and walnut oil.

Through monitoring Rancimat induction time (RIT), peroxide value (POV), and thiobarbituric acid-reactive substances (TBARS) of docosahexaenoic acid (DHA) algae oil and walnut oil during accelerated storage, the effects of the single and the combinations of seven kinds of antioxidants involving ascorbyl palmitate (AP), phytic acid (PA), vitamin E (VE), antioxidant of bamboo leaves (AOB), rosemary extract, tea polyphenols (TP), and tea polyphenol palmitate (TPP) against lipid oxidation were evaluated. RIT, POV, and TBARS results showed that the DHA algae oil sample containing 600 mg/kg TPP revealed the strongest stability and the walnut oil sample containing 450 mg/kg TPP and 100 mg/kg TP revealed the strongest stability. Then, the shelf lives of two oils were predicted from the extrapolation of the linear regression model between Log RIT and temperature. Our results indicated that the optimal antioxidant could prolong the shelf lives of DHA algae oil and walnut oil by 2.31- and 7.74-fold, respectively.

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.

Simultaneous quantification of 24 aldehydes and ketones in oysters (Crassostrea gigas) with different thermal processing procedures by HPLC-electrospray tandem mass spectrometry.

Aldehydes and ketones are secondary oxidation products resulting from lipid oxidation that occurs during food processing. These small molecule compounds not only have an impact on the quality, odor and flavor of food, but also play a role in the pathogenesis of many human diseases. In this study, a HPLC-MS/MS analytical method was developed and validated for the simultaneous determination of 24 aldehydes and ketones. The coefficients of determination (R2) for all aldehydes and ketones were higher than 0.9975 at the range of 0.2-2000 ng/mL. The recoveries were in the range 71.20-108.13% with RSD < 10%. The method was tested by analyzing lipids from oysters with different thermal processing (boiling, frying, roasting and air frying) procedures; the highest concentration for saturated aldehydes and ketones while the highest content of unsaturated aldehydes in boiling treatment. Meanwhile, fatty acid oxidative decomposition was in agreement with aldehydes and ketones formation. Moreover, principal component analysis, orthogonal partial least-squares discriminant analysis and variable importance in projection value showed that lipid oxidation is positively related to the formation of a variety of aldehydes and ketones.

Chitosan and Derivatives: Bioactivities and Application in Foods.

Chitosan is a biodegradable, biocompatible, and nontoxic aminopolysaccharide. This review summarizes and discusses the structural modifications, including substitution, grafting copolymerization, cross-linking, and hydrolysis, utilized to improve the physicochemical properties and enhance the bioactivity and functionality of chitosan and related materials. This manuscript also reviews the current progress and potential of chitosan and its derivatives in body-weight management and antihyperlipidemic, antihyperglycemic, antihypertensive, antimicrobial antioxidant, anti-inflammatory, and immunostimulatory activities as well as their ability to interact with gut microbiota. In addition, the potential of chitosan and its derivatives as functional ingredients in food systems, such as film and coating materials, and delivery systems is discussed. This manuscript aims to provide up-to-date information to stimulate future discussion and research to promote the value-added utilization of chitosan in improving the safety, quality, nutritional value and health benefits, and sustainability of our food system while reducing the environmental hazards.

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.

Improving the oxidative stability and lengthening the shelf life of DHA algae oil with composite antioxidants.

Based on various antioxidant mechanisms, four kinds of antioxidants including ascorbyl palmitate (AP), vitamin E (VE), phytic acid (PA) and one of the polyphenols (antioxidant of bamboo leaves, tea polyphenol palmitate or tea polyphenols (TP)) were used in combination to improve oxidative stability of docosahexaenoic acid (DHA) algae oil. To achieve the best effect, the formulations and mixture ratios of the antioxidant combinations were optimized. The effects were monitored by peroxide value, thiobarbituric acid-reactive substances, acid value, free radicals, Rancimat induction time and fatty acid composition of DHA algae oil undergoing accelerated storage. Finally, the DHA algae oil containing 80 mg/kg AP, 80 mg/kg VE, 40 mg/kg PA and 80 mg/kg TP had the highest oxidative stability. Furthermore, the shelf life of DHA algae oil containing the optimum composite antioxidant was predicted by using accelerated shelf life testing coupled with Arrhenius model, which was 3.80-fold longer than the control sample.

Mechanism of antioxidant action of natural phenolics on scallop (Argopecten irradians) adductor muscle during drying process.

Lipid hydrolysis and oxidation occurred in Argopecten irradians adductor muscle during hot air drying. Using an in vivo imaging system, we found that antioxidants of bamboo leaves (AOB) could diffuse into the adductor muscle upon marinating. Both tea polyphenols (TP) and AOB efficiently retarded lipid oxidation but had a slight effect on lipid hydrolysis during drying process. The in situ antioxidant mechanisms of AOB as well as TP were revealed, including quenching of free radicals detected by electron spin resonance, chelating metal ions determined by confocal laser scanning microscopy and inhibiting lipoxygenase. Less than 8% of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in AOB and TP marinated adductor muscle were decreased compared to more than 28% decrease in control adductor muscle during the drying process. Overall, these natural antioxidants, TP and AOB, efficiently maintained high nutritive value of adductor muscle, especially, their lipid quality.

Hydrolysis and oxidation of lipids in mussel Mytilus edulis during cold storage.

Change in quality of mussels (Mytilus edulis) meat when stored at 4 °C was evaluated by determining volatile basic nitrogen (TVB-N), peroxide value (POV), thiobarbituric acid reactive substance (TBARS), total oxidation (TOTOX), lipid class, fatty acid (FA), phosphatidylcholine (PC) and phosphatidylcholine (PE) content, and glycerophospholipid (GP) molecular species. After 4 days of storage, the percentages of triacylglycerol and polar lipid as well as the contents of PC, PE and major GP molecular species significantly decreased (P < 0.05), while the percentages of free FA and monoacylglycerol significantly increased (P < 0.05), indicating the hydrolysis of lipids. The increase in activities of phospholipase and lipase during storage suggests that they may contribute to the hydrolysis of lipids. The cold storage also resulted in significantly increased POV, TBARS and TOTOX as well as lipoxygenase activity (P < 0.05) but slightly decreased percentage of polyunsaturated FA (PUFA), indicating the occurrence of lipid oxidation.

Stability of resveratrol esters with caprylic acid during simulated in vitro gastrointestinal digestion.

Lipophenols, esterified phenols with fatty acids, have attracted increasing attention because of their better protective effects in lipid-based food matrices from oxidation. However, little is known about their digestion. In this study, the digestive stability of resveratrol (RSV) esters with caprylic acid (RCAPs) in a model gastrointestinal digestion system was evaluated. The results demonstrated that RCAPs were relatively stable without hydrolysis in mouth and gastric phases. However, in the intestinal phase, pancreatic lipase rather than phospholipase A2 could hydrolyze monoester and diesters to free RSV. After 120 min of incubation at 37 °C, 53.68% of monoester and 11.36% of diesters were hydrolyzed. However, no hydrolysis of the triester was noticed. Obviously, the level of hydrolysis of RCAPs was negatively correlated with the degree of substitution. Therefore, it was speculated that RSV in fatty acid ester forms could partially be absorbed by intestinal lumen in the form of free RSV.

Effect of Various Hot-Air Drying Processes on Clam Ruditapes philippinarum Lipids: Composition Changes and Oxidation Development.

Clam Ruditapes philippinarum was processed by hot-air drying and the changes of its lipids were evaluated by analyzing lipid classes, phospholipid classes, fatty acids, as well as oxidation parameters including peroxide value (POV), thiobarbituric acid-reactive substances (TBARS) value, total oxidation value (TOTOX), and oxidation test (OXITEST). The hot-air drying process reduced the contents of triacylglycerol, phosphatidylcholine, and phosphatidylethanolamine, indicating the hydrolysis of lipids. Meanwhile, the hot-air drying process significantly decreased the proportion of n-6 polyunsaturated fatty acid (PUFA), and consequently increased the PUFA ratio of n-3/n-6. Interestingly, the POV, TBARS and TOTOX decreased after the hot-air drying process. However, significant decline of the induction period for the dried clam tissue at elevated temperatures indicated their higher oxidation level, poor oxidative stability and reduction of shelf-life. Therefore, OXITEST method turned out to be an effective tool for estimating the level of lipid oxidation for hot-air dried clam.

Evaluation of the stability of tyrosol esters during in vitro gastrointestinal digestion.

Lipophenols such as tea polyphenol palmitate derivatives (palmitoyl esters of tea polyphenols) have been classified as non-toxic food additives due to their better protective effects on lipidic food matrices from oxidation, but their digestion and absorption have remained unexplored. In this study, the digestive stability of tyrosol acyl esters (TYr-Es) with fatty acids of different chain lengths and different degrees of unsaturation such as C12:0, C14:0, C16:0, C18:0, C18:1, C18:2, and C22:6 was evaluated using an in vitro simulated gastrointestinal tract model containing various digestive enzymes (pancreatin, pancreatic lipase and phospholipase A2). HPLC-UV measurements demonstrated that only pancreatin and pancreatic lipase, but not phospholipase A2, could hydrolyze TYr-Es to free TYr. The degree of TYr-E hydrolysis negatively correlated with the chain length but positively correlated with the degree of unsaturation of their lipid moiety. In addition, the fact that TYr in fatty acid ester forms could be absorbed by the intestinal lumen, at least partially in the form of free TYr, may explain a sustained release behavior of TYr-Es to TYr during the time-course following the digestion process.

Lipid profiles in different parts of two species of scallops (Chlamys farreri and Patinopecten yessoensis).

Different classes of lipids and phospholipids (PL) as well as fatty acid (FA) compositions, and glycerophospholipid (GP) molecular species in edible parts (adductor muscles) and by-products (gonads and mantles) of scallops Patinopecten yessoensis and Chlamys farreri were characterized. The lipids contained high levels of polyunsaturated FA (PUFA) (20.44-58.81% of total FAs) and PL (54.99-78.26% of total lipids). Among PL, phosphatidylcholine (41.39-51.86 mol%) was dominant. More than 230 GP species belonging to glycerophosphocholine, glycerophosphoethanolamine, glycerophosphoserine, glycerophosphoinositol, lysoglycerophosphocholine, lysoglycerophosphoethanolamine and lysoglycerophosphoinositol were characterized. Individual GP molecular species in different body parts of scallops were also partially quantified. Most of the dominant GP species contained PUFA, especially eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). Considering the high level of PUFA enriched GP, edible parts and by-products (gonads and mantles) of scallops Patinopecten yessoensis and Chlamys farreri provide great potential as health-promoting food for human consumption.

Extraction and detailed characterization of phospholipid-enriched oils from six species of edible clams.

Phospholipid (PL)-enriched oils were recovered from six species of edible clams, namely Cyclina sinensis, Mactra chinensis Philippi, Mactra veneriformis Reeve, Meretrix meretrix, Ruditapes phliippinarum and Saxidomus purpurata, using a mixture of ethanol and hexane (1:1, v/v). The oils contained a high proportion of polyunsaturated fatty acids (PUFA) (26.78-45.36% of total FAs), especially eicosapentaenoic acid (EPA) (8.17-10.48% of total FAs) and docosahexaenoic acid (DHA) (7.83-21.34% of total FAs). The oils also contained a high percentage of PL (39.86-74.05% of total lipids). Among PL, phosphatidylcholine (37.40-52.19mol%) and phosphatidylethanolamine (34.74-43.10mol%) were dominant. At least 435, 442, 513, 438, 433 and 437 glycerophospholipid (GP) molecular species were characterized, respectively, in lipids from Cyclina sinensis, Mactra chinensis Philippi, Mactra veneriformis Reeve, Meretrix meretrix, Ruditapes phliippinarum and Saxidomus purpurata. Most of the predominant GP molecular species contained PUFA, mainly EPA and DHA, indicating that clam is a potential resource of PUFA enriched GP.

Characterization of glycerophospholipid molecular species in six species of edible clams by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry.

The molecular species of glycerophosphocholine (GPCho), glycerophosphoethanolamine (GPEtn), glycerophosphoserine (GPSer), lysoglycerophosphocholine (LGPCho) and lysoglycerophosphoethanolamine (LGPEtn) from six species of edible clams were characterized by using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. At least 435, 453, 468, 443, 427 and 444 glycerophospholipid (GP) molecular species were characterized, respectively, from Cyclina sinensis, Mactra chinensis Philippi, Mactra veneriformis Reeve, Meretrix meretrix, Ruditapes philippinarum and Saxidomus purpurata. Most of the predominant GP molecular species in clam contained polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), indicating that clam is a potential resource of GP enriched PUFA. According to the amount of the major molecular species containing EPA and DHA, Cyclina sinensis was the best fit species for GPCho, Mactra veneriformis Reeve was the best fit species for GPEtn, Mactra chinensis Philippi was the best fit species for GPSer and LGPEtn, and Saxidomus purpurata was the best fit species for LGPCho.

Effects of long-term intake of Antarctic krill oils on artery blood pressure in spontaneously hypertensive rats.

BACKGROUND: In recent years, there has been a noticeable increase in research on krill oil (KO) for its health benefits. However, the action of KO in lowering blood pressure (BP) has not been studied yet. Therefore the aim of this study was to assess the ability of long-term KO supplementation to lower systolic BP (SBP) in spontaneously hypertensive rats (SHRs) and Sprague Dawley (SD) rats. RESULTS: Compared with the blank control (BC) SHRs administered edible soybean oil, the high-dose (500 mg kg-1 body weight (BW)) KO-supplemented SHRs in the 2nd, 3rd, 4th and 5th weeks following oral administration, the mid-dose (100 mg kg-1 BW) KO-supplemented SHRs in the 4th and 5th weeks following oral administration and the low-dose (20 mg kg-1 BW) KO-supplemented SHRs in the 5th week following oral administration showed significantly lower SBP (P < 0.05). However, supplementation of KO had no significant effect on the SBP of healthy SD rats. Meanwhile, 5 weeks of KO administration significantly increased the serum levels of nitric oxide (NO) and total NO synthase of SHRs (P < 0.05). CONCLUSION: KO has an antihypertensive effect in SHRs that is associated with an NO-related mechanism. © 2016 Society of Chemical Industry.

Identification of glycerophospholipid molecular species of mussel (Mytilus edulis) lipids by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry.

This study was carried out to identify the glycerophosphocholine (GPCho), glycerophosphoethanolamine (GPEtn) and glycerophosphoserine (GPSer) compositions in lipids extracted from mussels using Folch, Bligh-Dyer and methyl-tert-butyl ether (MTBE) methods by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS). The molecular species of GPCho, GPEtn and GPSer were characterized according to the MS and MS/MS information. A semi-quantitative method using internal standard was established to compare the difference in glycerophospholipids (GP) between samples recovered with different methods. At least 212, 230 and 206 GP species were identified, respectively, from lipids recovered by Folch, Bligh-Dyer and MTBE methods. Most of the abundant GP species in mussels contained EPA and DHA. Some GP species with low content were not present in lipids recovered by the Folch and MTBE methods when compared with that recovered by the Bligh-Dyer method. However, for most GP species in lipids recovered by different methods, no quantitative differences existed.