Synthesis and evaluation of acetylferulic paeonol ester and ferulic paeonol ester as potential antioxidants to inhibit fish oil oxidation

Synthesis and characterization of 3,4-dihydroxyphenyl acetic acid esters and study of their efficacy in bulk fish oil

Lipophilization of natural antioxidants is a proven strategy to enhance the solubility in bulk oil systems, thereby increasing their efficacy against oxidative degradation. This study aims to synthesize esters of 3,4-dihydroxyphenylacetic acid (3,4-DHPA) using Amberlyst-15 and to study the application of these esters in refined fish oil. Lipophilic esters were synthesized by esterification and transesterification of 3,4-DHPA in various solvent systems. Esters of methanol, butanol and hexanol were obtained with percent conversion of 81.1, 69.3 and 78.8 respectively, and were subjected to molecular characterization and in vitro oxidant assays. The 3,4-DHPA and its methyl ester showed 36% reduction in the TOTOX value over 30 days of storage. The length of the acyl chain in the ester was found to exert a high influence on its efficacy and lipophilicity. This is the first report of 3,4-DHPA and its lipophilic esters studied for enhancing the oxidative stability of fish oil.

Foam-templated oleogels constructed by whey protein isolate and xanthan gum: Multiple-effect delivery vehicle for Antarctic krill oil

To address the limitations of Antarctic krill oil (AKO) such as easy oxidation, unacceptable fishy flavor and low bioaccessibility of astaxanthin in it, a multiple-effect delivery vehicle for AKO is needed. In this study, whey protein isolate (WPI) and xanthan gum (XG) were utilized to construct AKO into oleogels by generating foam-templates. The effects of the concentration of XG on the properties of foam, cryogel and the corresponding oleogels were investigated, and the formation mechanism of oleogel was discussed from the perspective of the correlation between foam-cryogel-oleogel. The results demonstrated that with the increase of the concentration of XG, the foam stability was improved, the cryogel after freeze drying had a more uniform network structure and superior oil absorption ability, and the corresponding oleogel had excellent oil holding ability after oil absorption. The AKO oleogels showed superior oxidative stability compared with AKO. The in vitro digestion experiments demonstrated that the bioaccessibility of the astaxanthin in this oleogel was also considerably higher than that in AKO. In addition, this oleogel had masking effect on the odor-presenting substances in AKO, while retaining other flavors of AKO. The foam-templated oleogel can be considered as a multiple-effect vehicle for AKO to facilitate its application in food products. This study provides theoretical basis and data support for the development and utilization of novel vehicle for AKO, broadening the application of AKO in the field of food science.

Synthesis of lipoic acid ferulate and evaluation of its ability to preserve fish oil from oxidation during accelerated storage

Lipoic acid ferulate (LAF) was synthesized and its anti-free radical ability in vitro was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonicacid) (ABTS) assays. Protective effects of LAF in stabilizing fish oil were tested, compared to antioxidants such as lipoic acid, ferulic acid and tert-butylhydroxyquinone (TBHQ) by measuring peroxide values, thiobarbituric acid reactants, p-anisidine values, nuclear magnetic resonance (NMR) spectra and gas chromatography-mass spectrometry (GC-MS) spectra of fish oil during accelerated storage (12 days, 80 °C). The inhibitory effect of these antioxidants on fish oil oxidation followed the order TBHQ ≧ LAF > ferulic acid > lipoic acid. In addition, the omega-3 polyunsaturated fatty acids were the first to be oxidized. The formation of oxidation products followed a first-order kinetic model, and the addition of LAF effectively reduced the reaction rate constants. Therefore, LAF can effectively slow down the formation of oxidative products and prolong the shelf life of fish oil.

Integrating Multi-Type Component Determination and Anti-Oxidant/-Inflammatory Assay to Evaluate the Impact of Pre-Molting Washing on the Quality and Bioactivity of Cicadae Periostracum

Cicadae Periostracum (CP) is a traditional Chinese medicinal herb derived from the slough that is molted from the nymph of the insect Cryptotympana pustulata Fabricius. Washing with water to remove residual silt is a primary processing method of CP that is recommended by the Chinese Pharmacopoeia, but how washing methods affect the quality and bioactivity of CP is unknown. In this study, the quality and bioactivity of non-washed CP (CP-NW), post-molting-washed CP (CP-WAT), and pre-molting-washed CP (CP-WBT) were comparatively investigated. The quality of these CP samples was evaluated in terms of the UPLC-QTOF-MS/MS-based chemical profiling and semi-quantification of 39 N-acetyldopamine oligomers (belonging to six chemical types), the HPLC-UV-based quantification of 17 amino acids, the ICP-MS-based quantification of four heavy metals, and the contents of ash; the bioactivities of the samples were compared regarding their anti-oxidant and anti-inflammatory activities. It was found that, compared with CP-NW, both CP-WBT and CP-WAT had significantly lower contents of ash and heavy metals. Moreover, compared with CP-WAT, CP-WBT contained lower levels of total ash, acid-insoluble ash, and heavy metals and higher contents of N-acetyldopamine oligomers and amino acids. It also had enhanced anti-oxidant and anti-inflammatory activities. A Spearman's correlation analysis found that the contents of N-acetyldopamine oligomers and free amino acids were positively correlated with the anti-oxidant/-inflammatory activities of CP. All these results suggest that pre-molting washing can not only remove the residual silt but can also avoid the loss of the bioactive components and assure higher bioactivities. It is concluded that pre-molting washing could enhance the quality and bioactivity of CP and should be a superior alternative method for the primary processing of qualified CP.

Gas-phase ion migration spectrum analysis of the volatile flavors of large yellow croaker oil after different storage periods

The large yellow croaker, a species of fish found in the northwestern Pacific, is favored by consumers because of its prevalence in saltwater bodies, golden yellow abdomen, high calcium content, high protein, high fat content, and a flavor that originates from its lipids and volatile components. Volatile organic compounds significantly affect the aroma of food. In this work, electronic nose and headspace gas chromatography-ion mobility spectrometry were applied to analyze the flavor differences in fish oil durations. Through electronic nose system analysis, sensors W1C, W3S, W6S, and W2S directly affected fish oil flavor, and their flavor components were different. Gas chromatography-ion mobility spectrometry identified 26 volatile components (19 aldehydes, 3 ketones, 2 alcohols, 1 furan, and 1 olefin). (E,E)-2,4-hexadienal (D), (E,E)-2,4-hexadienal (M), 2,4-heptadienal (M), (E)-2-octenal, 2-propanone, 2-heptanone (M), 3-pentanone (D), and 1-octen-3-ol were the key flavor components of the fish oil. In conclusion, the combination of GC-IMS and PCA can identify the differences in flavor changes of large yellow croaker oil during 0–120 days storage. After 60 days storage, the types and signals of 2-propanone, 2-heptanone (M) components increase significantly. When 120 days storage, at this time, (E,E)-2,4-hexadienal (D), (E,E)-2,4-hexadienal (M), 2,4-heptadienal (M), (E)-2-octenal,(E)-2-octenal significantly. It has become the main flavor substance of fish oil. In summary, as the storage period increases, the components increase, and the oxidizing substances will increase, resulting in the deterioration of fish oil.

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The oxidation state of Large yellow croaker oil in different storage periods was investigated.

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The volatile compounds of Large yellow croaker oil were studied by GC-IMS.

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The effects of storage period on the composition of large yellow croaker oil samples were tested.

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We believe GC-IMS will play a crucial role in controlling the flavor of fish oil.

Changes of Volatile Flavor Compounds in Large Yellow Croaker (Larimichthys crocea) during Storage, as Evaluated by Headspace Gas Chromatography-Ion Mobility Spectrometry and Principal Component Analysis

The large yellow croaker is one of the most economically important fish in Zhoushan, Zhejiang Province, and is well known for its high protein and fat contents, fresh and tender meat, and soft taste. However, the mechanisms involved in its flavor changes during storage have yet to be revealed, although lipid oxidation has been considered to be one important process in determining such changes. Thus, to explore the changes in the flavor of large yellow croaker fish meat during different storage periods, the main physical and chemical characteristics of the fish meat, including the acid value, peroxide value, p-anisidine value, conjugated diene value, and identities of the various flavor substances, were investigated and analyzed by multivariable methods, including headspace gas chromatography-ion mobility spectrometry (GC-IMS) and principal component analysis (PCA). It was found that after 60 d storage, the types and contents of the aldehyde and ketone aroma components increased significantly, while after 120 d, the contents of ketones (2-butanone), alcohols (1-propanethiol), and aldehydes (n-nonanal) decreased significantly. More specifically, aldehyde components dominated over ketones and lipids, while the n-nonanal content showed a downward trend during storage, and the 3-methylbutanol (trimer), 3-methylbutanol (dimer, D), 3-pentanone (D), and 3-pentanone (monomer) contents increased, whereas these compounds were identified as the key components affecting the fish meat flavor. Furthermore, after 120 d storage, the number of different flavor components reached its highest value, thereby confirming that the storage time influences the flavor of large yellow croaker fish. In this context, it should be noted that many of these compounds form through the Maillard reaction to accelerate the deterioration of fish meat. It was also found that after storage for 120 d, the physical indices of large yellow croaker meat showed significant changes, and its physicochemical properties varied. These results therefore demonstrate that a combination of GC-IMS and PCA can be used to identify the differences in flavor components present in fish meat during storage. Our study provides useful knowledge for understanding the different flavors associated with fish meat products during and following storage.