Secondary Oxidation Products Research Articles

Insights into the effects of steaming on organoleptic quality of salmon (Salmo salar) integrating multi-omics analysis and electronic sensory system

The effect of steaming treatment on salmon quality was explored by different multi-omics and electronic sensory system in this study. A comparison between conventional steaming (CS) and anaerobic steaming (AS) was conducted in organoleptic quality of salmon. Twelve key volatile compounds were identified, which contributed to the flavor difference. The concentrations of hexanal, (E)-2-octen-1-al, and decanal in AS salmon were significantly lower than in CS salmon, which account for 68.9–80.5 % of the latter. During steaming, the fatty acids and diacylglycerols decreased significantly by 37.4 % and 57.9 %, respectively. Anaerobic steaming limited the degradation of some oxidized lipids, further reduced some volatile secondary oxidation products. Nucleotides and derivatives, succinic acid, glutamic acid, hydroxyproline and betaine contributed to the saltness, umami, richness of steamed salmon. Metabolomics data revealed that the higher creatinine, Ala-Ala and Ala-Leu provided more umami and less bitterness to AS salmon.

Antioxidants location affects the oxidative stability of spray-dried microcapsules loaded with fish oil

The oxidative stability of fish oil-loaded capsules (∼15 wt% oil load) produced by spray-drying and containing natural antioxidants of different polarity was investigated. For this purpose, three commercial rosemary extracts (e.g., water-dispersible; K1 or oil-soluble; K2, K3) and whey protein concentrate hydrolysate (WPCH), exhibiting surface-active properties, were evaluated. The capsules showed similar physicochemical properties (e.g., morphology, size and encapsulation efficiency >91%), regardless of the formulation. However, the polarity of the antioxidant used significantly influenced the oxidative stability. The microcapsules containing hydrophobic antioxidants showed the lowest peroxide value (PV) after drying, followed by the WPCH-containing capsules, although the PV evolution over storage was similar among the samples. Nonetheless, WPCH was the most effective antioxidant reducing the formation of volatile secondary oxidation products in the capsules. This was attributed to its partition at the oil/matrix interface, resulting in an enhanced protective effect when combined with tocopherols present in the encapsulated oil.

Ultrasound-aided pH-shift processing for resource-smart valorization of salmon and herring side streams

The possibility of reducing the amount of fresh water used during alkaline the pH-shift processing of salmon head (SH) and herring frame (HF) was evaluated with ultrasound (US) as a tool to mitigate its negative effects on protein yield. The role of water ratio and US for homogenate viscosity, mass yield, crude composition, functional properties and lipid oxidation of the SH and HF protein isolates were also investigated. Applying US during the solubilization step of the pH-shift process completely compensated for the reduced protein yield coming from using 3 rather than 6 volumes of water for HF, but not for SH. Using US had no negative effect on the composition and protein functionality of the HF protein isolate. However, it slightly increased its level of secondary lipid oxidation products. Altogether, applying US during the pH-shift processing at low water ratios can be a promising solution for more resource-smart valorization of herring side streams.

Poster 124: Elevated Lipid Metabolites in Stored Clinical OCA Media are Associated with Chondrocyte Death

Objectives: A major limitation of osteochondral allografts (OCA) is the deterioration of cartilage health associated with cell death during prolonged storage. It is well established that chondrocyte viability in OCA is a critical factor for repair and clinical outcomes, but little is known about the mechanisms that contribute to chondrocyte death during storage. Elevated bioactive lipid metabolites and free fatty acids (FFAs) have been associated with cell death and tissue damage for various pathologies through lipotoxicity. However, the levels and effect of FFA accumulation in OCA media during prolonged storage are unknown. The purpose of this study was to determine if bioactive lipid metabolites accumulate in the storage media of OCA and are associated with a loss of chondrocyte viability during prolonged storage. We hypothesized that FFAs will accumulate over time in the storage media of OCA and adversely impact cartilage health during storage. Methods: To elucidate potential mechanisms of cartilage health decline during storage, 21 fresh human hemi-condyle osteochondral allograft tissues and media provided by a US tissue bank were analyzed after 7, 28, and 68 days of prolonged cold storage. Targeted metabolomics analysis measured bioactive FFAs, and primary (lipid hydroperoxide, ROOH) and secondary (malondialdehyde, MDA) lipid oxidation products. Chondrocyte viability was measured using standard LIVE/DEAD assay and confocal microscopy. Results: All fatty acid metabolites in storage media significantly increased with increased storage time (Figure 1; p<0.05). ROOH was significantly higher at Day 28 of storage. No difference in secondary lipid hydroperoxide products in storage media were observed. Chondrocyte viability significantly declined in both the en face and vertical cross-section analysis with increased storage time (Figure 2) and inversely correlated with fatty acid metabolites (Figure 3; p<0.05). Conclusions: It is well established that elevated levels of certain free fatty acids and lipid oxidation products can alter cell function and cause cell death through lipotoxicity and other mechanisms. This work is the first to identify elevated levels of FFA metabolites and primary oxidation lipid product in the storage media from clinical OCA. The concentrations of FFA metabolites were measured at levels (>100µM) known to induce cell death and were directly correlated with chondrocyte viability. These findings provide important targets for understanding why cartilage health declines during storage to better optimize media formulations and improve graft health.

Reutilization of berry press residues in minced Baltic herring (Clupea harengus membras) – Effect on lipid oxidation and sensory characteristics during cold storage

Lipid oxidation is one of the main causes of quality deterioration in dark-muscled fish. This study investigated the effect of berry side streams of juice pressing or oil extraction at different concentrations on lipid oxidation and sensory quality of minced Baltic herring (Clupea harengus membras) stored at 1 °C. Lipid oxidation was assessed by determining the peroxide value and volatile secondary oxidation products. Generic descriptive analysis and gas chromatography-olfactometry were used to investigate the odor, flavor, and odor-active compounds of minces. Based on the peroxide value and formation of hexanal, 1-penten-3-ol, and 3,5-octadien-2-one, a concentration of 1.5 g/100 g of lingonberry-bilberry juice press residue and sea buckthorn juice press and oil extraction residue was sufficient to retard and reduce the extent of oxidation. Furthermore, the addition of these residues inhibited the formation of fishy odors during 3 days of storage. The control mince stored for 3 days showed the highest number and intensities of oxidation products such as (Z)-4-heptenal, 2,3-pentanedione, and (E,Z)-2,6-nonadienal, while their formation was retarded in the mince containing press residue from sea buckthorn. Berry press residues were efficient in controlling lipid oxidation of minced Baltic herring during storage and have the potential to mask potentially unpleasant fishy odor and flavor.

Changes of lipid oxidation, volatile and taste-active compounds during pan-heating of pork belly

This study investigated the mechanisms underlying the evolution and formation of aroma and taste-active compounds of pork belly in representative traditional pork cuisines during pan-heating. The results revealed that as the temperature increased to 110 ℃, the unsaturation of fatty acids decreased from 60.25 % to 58.71 %, while the content of free radicals and secondary oxidation products increased. At the later heating stages, the addition of spices and increased heating temperature (150 ℃) led to continuous increments in the contents (from 958.20 μg/kg to 1511.88 μg/kg) and diversity of volatile compounds in pork belly, imparting the unique aroma. Additionally, the accumulation of low-molecular-weight peptides, free amino acids, and nucleotides not only provided the substrate for thermal reactions and their synergistic effects, but also contributed to the desired taste quality. These findings offered insights into the flavor formation mechanisms of traditional pork cuisines and provided direction for further research.

Conjugation of aminated sugar beet pectin–tannic acid nanoparticles with cinnamaldehyde at the oil–water interface to stabilize a 3D printable high-internal phase emulsion

In this work, we demonstrated the use of aminated sugar beet pectin (SBP–NH2)–tannic acid (TA) nanoparticles (NPs) conjugated with cinnamaldehyde (CA) to form 3D printable high-internal phase emulsions (HIPEs). Unlike the absorption of common stabilizers, the interfacial conjugation of SBP-NH2/TA NPs with CA formed ultra-absorbed NPs at the oil–water interface through electrostatic bonding, hydrogen bonding, hydrophobic interactions, and Schiff base reaction. The addition of CA (2.5 wt%) to the oil phase significantly reduced the mean droplet size of SBP-NH2/TA NPs stabilized HIPE (75 vol% oil; SBP-NH2/TA mass ratios of 1:0.5) from 23.03 to 18.33 μm and greatly improved the stability of HIPEs during a 90-day storage period at 25 °C. Concomitantly, rheological studies indicate that HIPEs with CA had high viscoelasticity up to 3 orders of magnitude, providing HIPE-based inks with exceptional support performance and smooth extrusion features. In particular, TA and CA act as the components of a stabilizer and adsorb onto the oil–water interface, imparting combined antioxidant and antimicrobial dual capabilities to HIPEs. In the SBP-NH2/TA NPs stabilized HIPEs, the addition of CA resulted in 0.34-fold lower amounts of primary and secondary lipid oxidation products and 0.4–0.5-fold higher antimicrobial properties against either E. coli or S. aureus. This work established that the interfacial conjugation of the SBP-NH2/TA NPs with CA advanced the antioxidant and antimicrobial properties, stability, water-holding capacity, and viscoelastic properties of HIPEs. Furthermore, the three-dimensional (3D) printed structure with notable mechanical strength was achieved.

Olive Oil Benefits from Sesame Oil Blending While Extra Virgin Olive Oil Resists Oxidation during Deep Frying.

Fresh potatoes were deep-fried in olive oil (OO), extra virgin olive oil (EVOO), and their blends with 5%, 10%, and 20% v/v sesame oil (SO). This is the first report on the use of sesame oil as a natural source of antioxidants during olive oil deep frying. The oil was evaluated for anisidine value (AV), free fatty acids (FFAs), extinction coefficient (K232 and K270), Trolox equivalent antioxidant capacity (TEAC), and total phenols (TPs) until the total polar compounds (TPCs) reached 25%. Sesame lignan transformations were monitored through reversed-phase HPLC. While the TPCs in olive oils increased at a steady rate, the addition of 5%, 10%, and 20% v/v SO delayed TPCs' formation for 1, 2, and 3 h, respectively. The addition of 5%, 10%, and 20% v/v SO increased the olive oil frying time by 1.5 h, 3.5 h, and 2.5 h, respectively. The addition of SO to OO reduced the secondary oxidation products' formation rate. The AV for EVOO was lower than OO and all tested blends, even those with EVOO. EVOO was more resistant to oxidation than OO, as measured by the TPCs and TEAC, while the frying time rose from 21.5 to 25.25 h when EVOO replaced OO. The increase in frying time for OO but not for EVOO, after SO addition, points to a niche market for EVOO in deep frying.

Characterization of a fermented dairy, sour cream: Lipolysis and the release profile of flavor compounds

Lipolysis and flavor development during fermentation of sour cream were studied by evaluating the physicochemical changes, sensory differences and volatile components. The fermentation caused significant changes in pH, viable count and sensory evaluation. The peroxide value (POV) decreased after reaching the maximum value of 1.07 meq/kg at 15 h, while thiobarbituric acid reactive substances (TBARS) increased continuously with the accumulation of secondary oxidation products. The Free fatty acids (FFAs) in sour cream were mainly myristic, palmitic and stearic. GC-IMS was used to identify the flavor properties. A total of 31 volatile compounds were identified, among which the contents of characteristic aromatic substances such as ethyl acetate, 1-octen-3-one and hexanoic acid were increased. The results suggest that lipid changes and flavor formation in sour cream are influenced by fermentation time. Furthermore, flavor compounds may be related to lipolysis such as 1-octen-3-one and 2- heptanol were also observed.

A comparison of Echium, fish, palm, soya, and linseed oil supplementation on pork quality.

Long chain n-3 polyunsaturated fatty acids (PUFA) exert positive effects on human health. The long chain n-3 PUFA of pork can be increased by adding fish oil to the diet. Due to the cost and availability of fish oil an alternative source must be found. This study evaluated the effect of five dietary oils on meat quality, fatty acid composition and lipid stability. The five diets contained 1% palm oil (Control), 1% soya oil, 1% linseed oil, 1% fish oil, and 1% Echium oil, respectively. The trial consisted of 60 gilts, randomly allocated to five groups. All color parameters, extractable fat content, fat free dry matter, and moisture content of the m. longissimus muscle were unaffected by dietary treatment. Consumers and a trained sensory panel could not detect a difference between the control samples and the Echium oil sample during sensory analysis. Samples containing higher levels of PUFA (soya, linseed, fish, and Echium oil) had higher levels of primary and secondary lipid oxidation products after refrigerated and frozen storage. However, these values were still well below the threshold value where off flavors can be detected. The Echium oil treatment had significantly higher levels of long chain PUFA than the linseed oil treatment, but it was still significantly lower than that of the fish oil treatment. Echium oil supplementation did not increase the levels of n-3 to the same extent as fish oil did. The result did however suggest that Echium oil can be used in pig diets to improve muscle long chain n-3 fatty acid content without any adverse effects on meat quality when compared to linseed, soya, and palm oil.

Effect of postruminal supply of linseed oil in dairy cows: 2. Milk fatty acid profile and oxidative stability.

Our objective was to study the effect of increasing postruminal supply of linseed oil (L-oil), as a source of cis-9, cis-12, cis-15 18:3, on milk fatty acid profile and to assess the resulting impact on the development of volatile degradation products during the storage of homogenized milk. Five Holstein dairy cows fitted with a rumen cannula were randomly distributed in a 5 × 5 Latin square design. Abomasal infusion of L-oil was performed at the rate of 0, 75, 150, 300, and 600 ml/d during periods of 14 d. The concentration of cis-9, cis-12, cis-15 18:3 in milk fat increased linearly with L-oil dose. Concentrations of primary (conjugated diene and triene hydroperoxides) and secondary oxidation products (1-octen-3-one, propanal, hexanal, trans-2 + cis-3-hexenals, cis-4-heptenal, trans-2, cis-6-nonadienal trans-2, trans-4-nonadienal) increased during 11 d of storage at 4°C of homogenized milk under fluorescent light. The magnitude of the increase (difference between final and initial measurements) was linearly greater for all nine lipid oxidation products evaluated in response to increasing level of infusion. Results of the current experiment have shown that milk enriched in cis-9, cis-12, cis-15 18:3 via postruminal supply of L-oil is highly prone to oxidative degradation. This low oxidative stability, exposed under controlled experimental conditions, would represent a major obstacle to those who aim to market milk enriched in polyunsaturated fatty acids.

Stabilization of Sunflower Oil with Biologically Active Compounds from Berries.

Sunflower oil (Helianthus annuus) contains a rich concentration of polyunsaturated fatty acids, which are susceptible to rapid oxidative processes. The aim of this study was to evaluate the stabilizing effect of lipophilic extracts from two types of berries, sea buckthorn and rose hips, on sunflower oil. This research included the analysis of sunflower oil oxidation products and mechanisms, including the determination of chemical changes occurring in the lipid oxidation process via LC-MS/MS using electrospray ionization in negative and positive mode. Pentanal, hexanal, heptanal, octanal, and nonanal were identified as key compounds formed during oxidation. The individual profiles of the carotenoids from sea buckthorn berries were determined using RP-HPLC. The influence of the carotenoid extraction parameters ascertained from the berries on the oxidative stability of sunflower oil was analyzed. The dynamics of the accumulation of the primary and secondary products of lipid oxidation and the variation of the carotenoid pigment content in the lipophilic extracts of sea buckthorn and rose hips during storage demonstrated good stability at 4 °C in the absence of light for 12 months. The experimental results were applied to mathematical modeling using fuzzy sets and mutual information analysis, which allowed for the prediction of the oxidation of sunflower oil.

Epicatechin Inhibited Lipid Oxidation and Protein Lipoxidation in a Fish Oil-Fortified Dairy Mimicking System

In this study, a typical tea polyphenol epicatechin (EC) was investigated for its impact on the oxidative stability of whey protein isolate (WPI) in a fish oil-fortified emulsion. The oil-in-water emulsion system consisted of fish oil (1%, w/w), WPI (6 mg/mL), and EC (0.1, 1, and 2 mM), and the oxidation reaction was catalyzed by Fenton's reagent at 25 °C for 24 h. The results showed EC exhibited a dose-dependent activity in the reduction of lipid oxidation (TBARS) and protein carbonylation. A Western blot analysis demonstrated that protein lipoxidation was inhibited by EC via interrupting the covalent binding of lipid secondary oxidation products, MDA, onto proteins. In addition, protein lipoxidation induced a loss of tryptophan fluorescence, and protein hydrolysis was partially recovered by EC. The findings of this study provide an in-depth understanding of the performance of phenolic antioxidants in relieving lipid oxidation and subsequent protein lipoxidation in oil-containing dairy products.

Effects of Two Amphiphilic Diesters of L-Ascorbic Acid on the Oxidative Stability of Rabbit Meatballs

Lipid oxidation involves a cascade of phenomena leading to serious impairments of meat quality during storage. Novel strategies for lipid protection are therefore highly desirable. Herein, two amphiphilic diesters of L-ascorbic acid with myristic (DA) and stearic (DB) acids were synthesised and added at a 0.1% (w/w) to minced rabbit meat before preparing meatballs. Then, pH, colour indexes, weight loss, fatty acid profile and primary and secondary lipid oxidation products were analysed for meatballs treated with DA (n = 16), DB (n = 16), or not treated (C, n = 16), and stored for 80 days at −10 °C. Results showed that DA and DB did not specifically prevent weight loss and lipid oxidation. Nevertheless, the addition of DA on stored rabbit meatballs seemed to prevent colour modification and reduced (p = 0.0613) TBARS levels in the treated stored meat. For these reasons, further investigations on the properties of L-ascorbyl diesters on the oxidative stability of meat will likely be performed.

Oxidative stability and compositional characteristics of oil from microwave irradiated black cumin seed under accelerated oxidation condition

The present work evaluated the impact of microwave pre-treatment on the storage stability, fatty acids and triacylglycerol contents in black cumin seed oil (BCO) during storage at 62 ºC. During storage, the oxidative indicator values (free acidity, peroxide value, p-anisidine value, TOTOX, specific extinctions and thiobarbituric acid) for the oils increased faster in untreated oil samples than in the microwaved samples. The degradation rate of polyunsaturated fatty acids (PUFAs) and triacylglycerol species (LLL and OLL) during storage were higher in untreated samples compared to treated ones, indicating that oxidation proceeded more slowly in the treated samples. During storage, the generation of hydroperoxides, their degradation and the formation of secondary oxidation products as investigated by FTIR, were lower in the treated oils. In conclusion, microwave pre-treatment prior to oil extraction reduced the oxidative degradation of oil samples, thereby increasing the storage stability of BCO.

High Pressure Processing under Mild Conditions for Bacterial Mitigation and Shelf Life Extension of European Sea Bass Fillets

High pressure is an industrially established food preservation process applied for the minimal processing or cold pasteurization of chilled, fresh, or ready-to-eat products. This study aimed to quantify the effectiveness of high pressure on the inactivation of spoilage microflora and the shelf life extension of European sea bass (Dicentrarchus labrax) fillets. Fish fillets were subjected to mild, high pressure conditions (100–400 MPa; 3–25 °C; 5–10 min) and then stored at 0.0 ± 0.2 °C. Their shelf life was evaluated in terms of their microbiological, physicochemical, and sensorial quality. The results indicated that a shelf life extension of 1–5 d at 0 °C was achieved when pressures of 100 MPa were applied, whereas higher pressures resulted in an up to 5-fold increase in the shelf life of the fillets, depending on the applied pressure and temperature. A high pressure treatment combined with vacuum packaging showed an additional effect on the shelf life extension of the fillets, increasing the shelf life by 4–12 d when compared to aerobically stored products. Moreover, the high pressure treatment prevented lipid oxidation throughout the storage period, indicating no formation of secondary lipid oxidation products. The estimated shelf life of the fish fillets based on their sensorial quality was in accordance with the estimation based on the microbiological data.

Changes in fatty acids during storage of artisanal-processed freshwater sardines (Rastrineobola argentea).

For ages, indigenous small fish species have been important in food and nutritional security of poor communities in low income countries. Freshwater fish, in particular fatty fish species are attracting a great attention because they are good sources of health promoting long chain omega-3 fatty acids. Docosahexaenoic acid (DHA, C22:6n-3), Docosapentaenoic acid (DPA, C22:5n-3) and eicosapentaenoic acid (EPA, C20:5n-3) are the main omega-3 PUFAs known to confer health benefits in humans if consumed in required amounts. While nutritionally valued, omega-3 PUFAs in fish are susceptible to oxidative damage during processing, transportation and subsequent storage. Lake Victoria sardines (Rastrineobola argentea), are rich source of chemically unstable omega-3 fatty acids DHA, DPA and EPA. Traditionally, sardines are preserved by sun drying, deep frying and smoking. Sardine products are transported, stored and marketed at ambient temperatures. Generally, uncontrolled and higher temperatures are known to increase vulnerability of polyunsaturated fatty acids to oxidation which in turn results into loss of nutritional and sensory qualities. This study investigated changes of fat acids in sun dried, deep fried and smoked sardines during storage. Lipolysis and the progressive hydroperoxides formation were monitored by free fatty acids (FFAs) and peroxide value (PV) respectively. None volatile secondary products of lipid oxidation were measured by thiobabituric acid reactive substances (TBARS). Fatty acids were analyzed by gas chromatography with a flameionization detector (GC-FID). Deep fried sardines maintained the lowest and apparently stable PV, TBARS and FFAs. Proportions of saturated fatty acids and polyunsaturated fatty acids decreased with time while that of monounsaturated fatty acids increased. Omega-3 fatty acids EPA, DPA and DHA decreased with increase in storage time. In 21 days of storage, DHA was oxidized beyond detectable levels in all sardine products. Gradual increase in FFAs in sun dried sardines was suggestive of lipid hydrolysis induced by enzymes.

Characterization of triglycerides photooxidation under solar radiations: A stepwise Raman study.

Triglycerides (TGs) are one of the main components of the glycerolipid family. Their main task in cells is to store excess fatty acids. TG energy storage is mainly concentrated in adipocytes. TGs and free fatty acids constitute the majority (57.5%) of the skin surface lipids (SSLs). TGs are essential for the formation of the skin water barrier. This work is the second part of a global study that aims to evaluate the effect of solar radiations on SSLs using vibrational spectroscopy. In the first part of this work, a stepwise characterization of free fatty acids was performed, and different spectral descriptors were used to follow the different structural modifications during the photo-oxidation process, that is hydrogen abstraction, formation of hydroperoxides and peroxyl radicals as primary oxidation products and the formation of aldehydes, ketones, alcohol as secondary products. In this second part, the photo-oxidation of TGs was evaluated using Raman spectroscopy. A decrease in the CH2/CH3 stretching bands ratio that confirmed the hydrogen abstraction, an increase in the 1165/1740cm-1 ((δ(OH) and υ(C-O))/ν(C=O) (ester)) ratio indicated the formation of secondary oxidation products such as hydroperoxides. And finally, an increase in the 1725/1740cm-1 (υ(C=O) (ald.)/υ(C=O) (ester)) ratio and the trans ν(C=C)/cis ν(C=C) ratio highlighted the formation of aldehydes, alcohols, ketone, trans secondary products and others.

EVALUATION OF LEVEL OF RANCIDITY OF EDIBLE OIL IN SOME FRIED SNACKS FOOD

This work evaluated the level of rancidity of edible oil in six (6) fried snacks food, namely, beans cake (Akara), groundnut cake (Kuli-kuli), bread buns, fried fish, fried yam chips and fried potatoes chips, purchased from hawkers in Wukari, Taraba State, Nigeria.. The rancidity indicators and their ranges in the samples obtained, include, Acid Value (4.10 – 6.90 mgKOH/g), Free Fatty Acid (2.05 – 3.45 mgKOH/g), Peroxide Value (12 – 46.60 mEq/kg), Moisture Content (4.00 – 44.30 %), Conductivity (0.14 – 1.58 µS/cm) and Viscosity (26.20 – 56.50 mm2/S). The results obtained suggested that the fried snacks foods contain hazardous secondary oxidative products, an implication that the oil in the food sample has become rancid and as such, unsafe for human consumption. The reason given for this is that the oil has been used for frying for too many times instead of the recommended two times. The values obtained in this study far exceeded the stipulated standard acceptable ranges given by WHO, FAO and INSO. It is therefore recommended that the public should be advised and educated that oil that has been used for frying twice should be discarded and not used again. Also, Policy makers and relevant authorities should develop a device for in-situ determination for checking of the quality of oil used for fried snacks food in restaurants without going to the laboratory.

Development of Hydrophobically Modified Casein Derivative-Based Delivery System for Docosahexaenoic Acids by an Acid-Induced Gelation.

Although omega-3 fatty acids including docosahexaenoic acid (DHA) contain various health-promoting effects, their poor aqueous solubility and stability make them difficult to be induced in dairy foods. The aims of this research were to manufacture casein derivative-based delivery system using acid-induced gelation method with glucono-σ-lactone and to investigate the effects of production variables, such as pH and charged amount of linoleic acid, on the physicochemical properties of delivery systems and oxidative stability of DHA during storage in model milk. Covalent modification with linoleic acid resulted in the production of casein derivatives with varying degrees of modification. As pH was reduced from 5.0 to 4.8 and the charged amount of linoleic acid was increased from 0% to 30%, an increase in particle size of casein derivative-based delivery systems was observed. The encapsulation efficiency of DHA was increased with decreased pH and increased charged amount of linoleic acid. The use of delivery system for DHA resulted in a decrease in the development of primary and secondary oxidation products. An increase in the degree of modification of casein derivatives with linoleic acid resulted in a decrease in the formation of primary and secondary oxidation products than of free DHA indicating that delivery systems could enhance the oxidative stability of DHA during storage in model milk. In conclusions, casein derivatives can be an effective delivery system for DHA and charged amount of linoleic acid played a key role determining the physicochemical characteristics of delivery system and oxidative stability of DHA.