Effects of gallic acid alkyl esters and their combinations with other antioxidants on oxidative stability of DHA algae oil.

The most effective composite antioxidants for DHA algae oil were optimized by combining the selected gallic acid (GA) alkyl ester with other commonly used antioxidants. Results of Rancimat induction time, peroxide value, thiobarbituric acid-reactive substances, and free radical generation indicated that octyl gallate (OG) was the best one in DHA algae oil among GA alkyl esters with various chain lengths. Therefore, OG was used to combine other antioxidants (antioxidant of bamboo leaves, rosemary extract, tea polyphenols, tea polyphenol palmitate (TPP), ascorbyl palmitate, vitamin E, phytic acid and phospholipid) for further improving the oxidative stability of DHA algae oil. The combination of OG + TPP showed the best antioxidant effect among the composite antioxidants of two and three components. Through optimization of mixture ratio, the combination of 53.20 mg/kg OG + 360 mg/kg TPP demonstrated the best antioxidant capacity, which prolonged the shelf life of DHA algae oil by 4.24 folds.

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.

Formation and disappearance of aldehydes during simulated gastrointestinal digestion of fried clams.

The formation and disappearance of aldehydes during simulated gastrointestinal digestion (SD) of fried clams was investigated in order to shed light on the underlying mechanism. Results from the thiobarbituric acid reactive substance (TBARS) and fluorometric assays using a specific aldehyde probe indicated that the SD (with lipase) of fried clams initially reduced (at the gastric stage), but subsequently increased (mainly at the intestinal stage) the contents of total aldehydes. Meanwhile, eight specific aldehydes including propanal, acrolein, trans-2-pentenal, hexanal, trans,trans-2,4-octadienal, trans,trans-2,4-decadienal, 4-hydroxy-hexenal and 4-hydroxy-nonenal in the digested meal were determined by using a high-performance liquid chromatography-tandem electrospray ionization mass spectrometry (HPLC-ESI-MS/MS) method. Results indicated that the changes in the trend of the contents of the eight aforementioned aldehydes were similar to those of total aldehydes during SD (with lipase) of fried clams. However, a similar SD process without lipase time-dependently reduced the contents of total and individual aldehydes. Moreover, lipid classes and free fatty acids (FFAs) in the digested meal were determined to reveal the degree of hydrolysis of lipids during the SD process. Results indicated that the SD (with lipase) of fried clams significantly hydrolyzed triacylglycerols (TAG) and polar lipids (PL) and produced FFAs, but the SD process without lipase resulted in negligible lipid hydrolysis. Thus, our results demonstrated a positive correlation between lipid hydrolysis and aldehyde generation during the SD of fried clams. Alternatively, unsaturated FFAs instead of TAG and PL could have served as the main precursors for aldehyde generation due to their high oxidative susceptibility.

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.

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).

Lipid Profile and Glycerophospholipid Molecular Species in Two Species of Edible Razor Clams Sinonovacula constricta and Solen gouldi.

Total lipids were extracted from razor clams Sinonovacula constricta and Solen gouldi, and the molecular species of glycerophospholipid (Gpl) including choline glycerophospholipid (ChoGpl), ethanolamine glycerophospholipid (EtnGpl), serine glycerophospholipid (SerGpl), inositol glycerophospholipid (InsGpl), lysoChoGpl, lysoEtnGpl, and lysoSerGpl were characterized using a direct-infusion tandem mass spectrometric method for the first time. Meanwhile, the lipid class composition and phospholipid (PL) class composition as well as the fatty acid (FA) composition of total lipids, triacylglycerol (TAG), and PL were also investigated. About 238 and 235 molecular species were characterized, respectively, in Sinonovacula constricta and Solen gouldi. The majority of the dominant Gpl molecular species contained n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Also, razor clam lipids contained a high-proportioned PL (52.19-65.41% of total lipids) and PUFA (47.94-54.81 mol%). Furthermore, PL contained a higher proportion of PUFA (63.05-67.13 mol%), especially DHA (20.04-22.47 mol%) and EPA (16.27-21.46 mol%) than TAG (the corresponding values being 33.73-34.45, 11.95-12.27, and 8.13-0.8.99 mol%, respectively). Meanwhile, phosphatidylcholine (44.38-46.21 mol%) and phosphatidylethanolamine (38.84-39.95 mol%) were dominant among PL. In consideration of the high proportion of PUFA-enriched Gpl, razor clam plays a great role in promoting human health.

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.