Effects of Added Phosphates on Lipid Stability During Salt Curing and Rehydration of Cod (Gadus morhua)

Effects of added phosphates on retardation of lipid oxidation of salted cod during processing, storage and after rehydration were investigated. Lipid hydrolysis progress and development of color, primary and secondary lipid oxidation products and fluorescence intensities were determined. Added phosphates significantly retarded lipid hydrolysis and lipid oxidation progress, resulting in lower free fatty acid , lipid hydroperoxides (PV), thiobarbituric acid-reactive substances (TBARS) as well as fluorescence intensities (δF _or and δF _aq). Significant correlation between the lipid oxidation products (PV, TBARS, δF _or and δF _aq) and yellow/brownish discoloration (b* value) of salted cod was observed. Principal component analysis showed that TBARS, b* value and δF _or were the strongest indicators of lipid oxidation during salting and storage.     

The Inhibitory Effect of Gallic Acid Alkyl Esters on Lipid Oxidation of Intactly Soaked Oyster Meats and Oyster Meat Homogenates during Refrigerated Storage

In this study, the antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate (MG), butyl gallate (BG), octyl gallate (OG), and lauryl gallate (LG) in whole oyster meats and oyster meat homogenates during cold storage are investigated. The oxidation degree of lipid is measured by peroxide value (POV), thiobarbituric acid active substances (TBARS), and polyunsaturated fatty acid (PUFA) percentage. The results show that the lipid oxidation in the two types of samples is inhibited by GA alkyl esters, and the antioxidant effects first increase and then decrease along with the extension of the chain length, among the esters, BG and OG are relatively more effective. Therefore, it is speculated that the antioxidant capacity of GA alkyl esters may be influenced by hydrophobicity and follows a “cut-off effect” in whole oyster meats and oyster meat homogenates. Practical application: Seafood is easily oxidized even under cold storage because it contains more PUFA. Antioxidants are widely used to inhibit lipid oxidation. In this study, the antioxidant capacity of GA alkyl esters in whole oyster meats and oyster meat homogenates is investigated, which improves the selection of suitable antioxidants to strengthen the oxidation stability of oyster samples for cold storage.     

Influence of blanching treatment and drying methods on the drying characteristics and quality changes of dried sardine (Sardinella gibbosa) during storage

The aim of this study is to examine the drying characteristics of blanched and unblanched sardine during indoor and open sun drying processes. Changes in temperature and relative humidity of the air during drying were recorded. The color, peroxide value (PV), thiobarbituric acid reactive substances (TBARS), free fatty acid (FFA) content, fatty acid composition, and sensory attributes of dried samples were also evaluated once a month for 5 months of storage. High drying rates were obtained in all samples at the start of drying and then decreased with increasing drying time. The highest drying rate and effective water diffusivity (D_eff) were observed in blanched sardine during open sun drying. Blanching treatment slowed down the FFA progression during product storage but adversely affected the color, PV, and TBARS content as well as sensory properties. Although sardine dried for a longer time under indoor drying conditions, it attained a stable moisture ratio that was lower than in open sun-dried samples. Indoor drying produced a quality stable product with less lipid oxidation and the desired moisture content, higher polyunsaturated fatty acids and sensory properties. Blanching treatment negatively affected the fish quality and is therefore not recommended for commercial sardine drying.     

Effects of lipid oxidation on fish lipids — amylopectin interactions

The results of studies on fish lipid oxidation effects on lipid‐amylopectin starch interactions are presented. Particular attention is paid to fish lipid availability (extractability from the system) and fatty acid contributions to individual lipid groups after mixing‐provoked interaction and after a 30‐day storage at —18 °C. The study involved model systems containing fish lipids at different levels of oxidation, lipids containing an antioxidant (BHA), and gelatinised amylopectin starch in a 10% aqueous solution. The lipid to starch ratio was 1:1. The test systems were subjected to selective extraction. The extracts were assayed for lipid content, peroxide value, anisidine value, fluorescence, and fatty acid composition. Compared to fresh fish lipids, those lipids, which were oxidised to a higher extent were shown to be more amenable to complexing with amylopectin, but they were also more readily released during frozen storage. On the other hand, addition of BHA stabilised the lipid‐amylopectin starch interaction during storage at —18 °C. In the entire systems tested, polyunsaturated fatty acids, eicosapentaenoic and docosahexaenoic acids in particular, proved to be most susceptible to binding, up to 90% of the latter being complexed.     

Impact of Frying on Changes in Clam (Ruditapes philippinarum) Lipids and Frying Oils: Compositional Changes and Oxidative Deterioration

The current study shows the compositional changes and oxidation development of clam (Ruditapes philippinarum, R. philippinarum) lipids and frying oils when subjected to different processing conditions. Parameters measured include acid value, peroxide value (POV), thiobarbituric acid-reactive substances (TBARS), total oxidation (TOTOX), lipid classes, fatty acid composition, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) contents together with major glycerophospholipid (GP) molecular species. Deep-fat frying increased triacylglycerol (TAG) content and decreased the contents of PC, PE, and GP molecular species in clam in a time-dependent manner. Meanwhile, minor amounts of free fatty acids, diacylglycerols, monoacylglycerols, and polar lipids were detected in frying oils, indicating lipid migration between the clam and frying oils. The time-dependent increase of POV, TBARS, and TOTOX in fried clams and frying oils with concurrent reduction of docosahexenoic acid and eicosapentaenoic acid indicates extensive oxidative degradation of clam lipids. Moreover, the moisture-rich clam aggravated the deterioration of frying oils. Consequently, deep-fat frying significantly altered the lipid profile and decreased the nutritional value of clams.     

Effects of natural antioxidants on the lipid profile of electron beam‐irradiated beef burgers

The purpose of this study was to assess the efficacy of rosemary and oregano extracts in avoiding oxidative changes in beef burgers, and to evaluate the fatty acid profile of these products after electron beam exposition. Extracts, individually or in combination, were added to beef burgers and compared to synthetic antioxidants commonly used in food (butylated hydroxytoluene, butylated hydroxyanisole). The ground beef were submitted to electron beam irradiation at doses of 0, 3.5 and 7 kGy, and stored for 90 days. At regular time intervals, lipid oxidation and fatty acid composition were evaluated through measurement of thiobarbituric acid‐reactive substances (TBARS) and gas chromatography, respectively. The results indicate that, although the irradiation process triggers an increase in the lipid oxidation ratio expressed by TBARS values, great changes in the fatty acid profiles were not observed; instead, they continued to present characteristics very similar to that of non‐irradiated beef. Thus, as irradiation doses of up to 7 kGy for frozen meat can make foods safe from foodborne pathogens, natural antioxidants derived from spices are able to reduce and avoid lipid changes that may cause a deterioration of the sensory quality of these foods, and these natural extracts offer a good choice for replacing synthetic additives.     

Comparative analyses of three dehydration methods on drying characteristics and oil quality of in-shell walnuts

Developing an effective drying method for in-shell walnuts (Juglans regia L.) is a major postharvest processing concern in the nut industry. Three drying methods, including hot air drying (AD), vacuum drying (VD), and hot air-assisted radio frequency drying (ARFD), were experimentally compared and analyzed. The changes in lipid oxidation attributes, fatty acid composition, total antioxidant capacity (TAC), and total phenolic concentration (TPC) of walnuts were determined after dehydration and during storage. The results showed that the drying time required for in-shell walnuts using ARFD was the shortest (138?min), followed by VD (185?min) and AD required the longest time (300?min). Particularly, AD resulted in the highest lipid oxidation, followed by VD and ARFD. The walnuts treated by ARFD contained more unsaturated fatty acid than those treated by AD. Moreover, both the reduced power assay and free radical scavenging capacity tests showed that ARFD and VD had little effect on the TAC and TPC of walnuts during the drying process and storage. Overall, ARFD provides an effective and rapid drying method for in-shell walnuts.     

Stability Profile of Fatty Acids in Yak (<Emphasis Type="Italic">Bos grunniens</Emphasis>) Kidney Fat During the Initial Stages of Autoxidation

Previously, we have shown that the fatty acid composition of yak kidney is of reasonable value and is suitable for further development of possible commercial products. Changes in the fatty acids of yak kidney fat during the initial stages of storage have been investigated. The full period of autoxidation was determined by peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) at 15 ± 1 °C for up to 70 days. The stability profile of the fatty acids identified by gas chromatography demonstrated that saturated fatty acids increased from 49.68 to 55.96% and that polyunsaturated fatty acids and monounsaturated fatty acids decreased from 10.73 to 6.95% and from 37.85 to 28.22%, respectively. Amounts of all the functional fatty acids except conjugated linoleic acid and linoleic acid, started to decrease after 10 days of storage. These results indicated that the initial stage of autoxidation occurred during the first 25 days of storage. It is suggested that development of potential commercial products should be accomplished within ten days, because the functional fatty acids started to decrease after this period of storage. In addition, the good correlation between PV/TBARS values and changes of individual fatty acids could be used as an indicator to monitor the changes of the functional fatty acid during the development process of yak kidney fat-related commercial products.     

Fatty acid composition and oxidation of lipids in Korean catfish

This study determined the lipid content and FA composition of muscle and a mixture of muscle and viscera from Korean catfish as well as lipid oxidation and hydrolysis. Lipid content and FA compositions in Korean catfish, which were purchased every month or two during September 1999–July 2000, were analyzed. Lipid oxidation and hydrolysis were determined as PV, thiobarbituric acid value, and FFA in the muscle and the mixture during storage at 2°C for 12 d and −14°C for 9 wk. Lipid contents of the muscle and the mixture were 3.2 (w/w) and 5.4%, respectively. Oleic acid was the most abundant FA in the catfish lipids, constituting 28.0% (w/w) of total FA in the muscle and 25.6% in the mixture, followed by palmitic acid and linoleic acid, amounting to 20.2 and 12.2%, respectively, in the muscle and 20.2 and 12.5% in the mixture. EPA and DHA were 3.2 and 6.8%, respectively, in the muscle and 3.5 and 8.1% in the mixture. Seasonal variation in lipid contents and FA composition was minimal in catfish. Lipids in minced catfish oxidized and hydrolyzed readily at 2°C. Inclusion of viscera into the muscle increased lipid oxidation and hydrolysis. Frozen storage at −14°C and addition of ascorbic acid both reduced lipid oxidation. Frozen storage retarded lipid hydrolysis in catfish.     

Influence of Radiation Processing of Cooked Beef Sausage on Its Lipids

The effect of gamma irradiation on fatty acid composition and lipid oxidation in emulsion-type cooked beef sausages was investigated. Vacuum-packaged sausages were irradiated at 2, 4, 6 and 8 kGy and stored at 4 °C for 4 weeks. Samples were analyzed for fatty acid composition at 0 and 4 weeks and lipid oxidation after 0, 1, 2, 3 and 4 weeks of storage. Irradiation reduced the content of oleic acid and linoleic acid, and the effect was intensified during storage. Elaidic acid content increased at doses of 6 and 8 kGy. The results indicated that irradiation at 6 and 8 kGy increased lipid oxidation, measured as the thiobarbituric acid reactive substances value. Based on the results, cooked beef sausages could be irradiated at 2 and 4 kGy without affecting the molecular structure of lipids.     

Effect of advanced chilling methods on lipid damage during sardine (Sardina pilchardus) storage

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its effect on lipid damage (hydrolysis and oxidation) was evaluated during the chilled storage of a fatty fish species, sardine (Sardina pilchardus). Slurry ice treatment was checked alone and in combination with ozone and compared to traditional flake icing during a 22‐day storage. Different lipid damage indices (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA‐i; fluorescent compounds, FR) were checked and compared to sensory assessment and nucleotide degradation (K value). According to lipid hydrolysis (FFA) and oxidation (PV and FR) developments, slurry ice showed an inhibitory effect (p <0.05) on lipid damage during storage, as well as an inhibition of nucleotide autolytic degradation. Ozonised slurry ice did not provide differences (p >0.05) from slurry ice alone when considering lipid hydrolysis, nucleotide degradation and some lipid oxidation indices (PV and FR), although a higher (p <0.05) TBA‐i was observed at day 22 of storage when compared to flake ice and slurry ice treatments. However, a lower (p <0.05) fluorescence development was observed for fish treated under ozonised slurry ice when compared to traditionally iced fish. Sensory assessment showed a higher shelf life for fish samples treated under ozonised slurry ice than for their counterparts under slurry ice (15 d versus 12 d), while flake icing led to a far shorter shelf life (5 d). According to sensory and biochemical (lipid matter and nucleotide) analysis, slurry ice has proved to be a promising technology for damage inhibition and quality retention in a fatty fish species such as sardine. Ozonised slurry ice was also shown to be useful, since a longer shelf life was obtained in the present experiment and a pro‐oxidant effect of ozone on sardine lipids was not proved.     

Antioxidant Activity of Sesamin in Canola Oil

The present study presents the antioxidant activity of sesamin in canola oil compared with that of butylated hydroxytoluene (BHT) by monitoring the oxygen consumption and the decrease in linoleic acid and α-linolenic acid. The oxidation of canola oil was conducted at 35, 60, 90, 120 and 180 °C with addition of 50–400 ppm sesamin. Results from the oxygen consumption test showed that sesamin dose-dependently inhibited the oxidation of canola oil at concentrations of 50–200 ppm at temperatures of 60–180 °C, however, sesamin lost its antioxidant activity at a low temperature of 35 °C. The fatty acid analysis also demonstrated that sesamin at 50, 100 and 200 ppm dose-dependently prevented the oxidation of linoleic acid and α-linolenic acid in canola oil. Both the oxygen consumption and the fatty acid analysis demonstrated sesamin was less effective than BHT as an antioxidant at temperatures of 60–180 °C. It was therefore concluded that sesamin could prevent the lipid oxidation of frying fats and oil, however, its antioxidant activity was not as potent as that of BHT.     

Effect of microencapsulation and spray drying on oxidative stability of flaxseed oil and its release behavior under simulated gastrointestinal conditions

Flaxseed oil is one of the richest sources of omega-3 fatty acid (α-linolenic acid, ALA). It contains high amounts of polyunsaturated fatty acids, making it extremely susceptible to oxidation. In the present study, flaxseed oil was stabilized using microencapsulation followed by spray drying and studied for its oxidative stability in terms of peroxide value (PV), thiobarbituric acid, and p-anisidine value at room temperature (35 ± 1°C) and low temperature (4–7°C) storage for 6 months. Results revealed that the developed flaxseed oil powder was stable throughout the storage period and PV remained below to the maximum permissible limit (≤5 mEq/kg oil) prescribed by the Codex Alimentarius Commission. The fatty acids profile measured by gas–liquid chromatography indicated a 14.28–15.13% decrease in ALA content in flaxseed oil as a result of microencapsulation and storage at room temperature. In vitro digestion behavior of microcapsules showed 4.39 ± 0.53 to 19.87 ± 0.47% release of flaxseed oil under simulated gastric continued, whereas under gastrointestinal conditions it was 20.00 ± 3.66 to 59.99 ± 9.29%.     

Stability of the lipid fraction of milk‐based infant formulas during storage

A study is made of the effects of storage (time and temperature) on the lipid fraction of four milk‐based adapted infant formulas with basically the same composition, though differing in the iron salt added (lactate or sulfate) and/or the vitamin E source (α‐tocopherol or α‐tocopherol acetate). Peroxide value, hydroperoxide C₁₈ percentage and thiobarbituric acid‐reactive substance (TBARS) content were used as indicators of lipid peroxidation. Fat contents remained stable throughout storage. Peroxide values increased from the first storage month and were affected by storage time, although they exhibited irregular behavior. Storage time and temperature affected hydroperoxide percentage, which was seen to be the earliest indicator of lipid oxidation, being measurable in newly manufactured formulas. TBARS values were only affected by storage time. No statistically significant differences were found among the four infant formulas for any of the lipid oxidation indicators.     

Development of Lipid Changes Related to Quality Loss During the Frozen Storage of Farmed Coho Salmon (<Emphasis Type="Italic">Oncorhynchus kisutch</Emphasis>)

Lipid changes related to quality loss were evaluated during frozen storage of coho salmon for up to 15 months. Biochemical indices concerning lipid hydrolysis (free fatty acids, FFA) and oxidation (peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescent compounds, FR; polyene index, PI) were determined and compared to sensory (odor and taste) and endogenous antioxidant (tocopherol isomers and astaxanthin) assessments. As a result of the frozen storage, lipid hydrolysis was shown to develop according to the increase in FFA content (p < 0.05). However, most biochemical lipid oxidation indices (PV, TBA-i and FR) led to a low degree of rancidity development (p < 0.05) when compared to other fatty fish species under similar frozen storage conditions. The PI value decreased (p < 0.05) at month 10 but then remained unchanged until the end of the experiment. Rancid odor and taste development were shown to be low throughout the experiment, according to the biochemical indices mentioned above. However, a progressive decrease (p < 0.05) in the original fresh odor and taste of salmon fish flesh occurred with increasing frozen storage time, such that fish samples had the poorest scores by month 15. Endogenous antioxidants were remarkably stable throughout the experiment and which might contribute to the oxidative stability of frozen farmed coho salmon lipids.     

Rancidity development during the chilled storage of farmed Coho salmon (Oncorhynchus kisutch)

Coho salmon (Oncorhynchus kisutch) is a fatty fish species whose farming production has greatly increased in recent years. Lipid damage produced during Coho salmon chilled storage was studied for up to 24 d. Lipid hydrolysis (free fatty acids, FFA) and oxidation (conjugated dienes; peroxide value, PV; thiobarbituric acid index, TBA‐i; fluorescent compounds formation, FR; browning development) were determined and compared to lipid composition (polyene index, PI; astaxanthin, AX) changes and sensory assessment (rancid odour development) results. Most lipid damage indices developed slowly during storage; thus, values obtained for FFA, PV, TBA‐i and FR were in all cases under 1.5 g/100 g, 4.0 meq oxygen/kg lipid, 0.40 mg malondialdehyde/kg muscle and 0.40, respectively. Odour assessment showed a significant (p <0.05) rancidity development at day 10, when compared to starting fish material; then, non‐acceptable values were obtained at days 19 and 24. The PI analysis showed not many differences during the storage time, with the lowest mean value at day 19. AX analysis indicated a relatively high content in the white muscle, which was maintained till the end of the experiment. A low oxidation development is concluded for Coho salmon lipids when compared to other fatty fish species under the same chilling conditions. AX was found to contribute to the oxidation stability of Coho salmon lipids, due to its free radical scavenger properties.     

Impacts of Oil Types and Storage Conditions on Milk Fat Quality of Strained Yogurt Immersed in Oil

To maintain strained yogurt freshness, it was shaped into balls (3–3.5 cm diameter), completely immersed in oil, and stored at refrigerated or ambient temperature for 6 months. The impacts of immersing strained yogurt in oil on the topped oil and product's final quality of lipids including fat oxidation, lipolysis, cholesterol oxidation, and conjugated linoleic fatty-acid content (CLNA) (i.e., as freshness indicators), during storage under various storage conditions, were evaluated. Peroxide value (PV), 7-keto-cholesterol, free fatty acids (FFA), and CLNA content were also determined. When stored in light, FFA of strained yogurt immersed in olive or corn oil increased from 0.44 to 1.29 and from 0.12 to 0.58, respectively. Olive oil-topped and corn oil-topped samples exposed to light had 48.9 and 7.9 (meq O₂ kg⁻¹) PV, respectively. Similar trends were reported for strained yogurt fat during storage for up to 6 months. Storage conditions showed little to no effects on the rate of fat and cholesterol oxidation, fat lipolysis, and CLNA content. Strained yogurt freshness indicators were maintained during the extended storage duration without refrigeration. The freshness indicators have a significant impact on enhancing consumer preference of strained yogurt.     

Effects of antioxidants and humidity on the oxidative stability of microencapsulated fish oil

The effects of various antioxidants and RH on the oxidative stability of microencapsulated fish oil powder were investigated using PV and thiobarbituric acid tests. The micorencapsulation process provided high encapsulation efficiency (≥88% of extractable fish oil). Without antioxidants, the encapsulated fat was 10 times more stable against oxidation than the surface fat, as determined by PV. α-Tocopherol, which is a lipophilic antioxidant, showed a greater antioxidative effect in both surface and encapsulated fats than ascorbyl palmitate, which is an amphiphilic antioxidant. According to TBARS values, the longest lag period was observed at 0% RH. Addition of >200 ppm α-tocopherol in a 10–30% RH range prolonged the oxidative stability of the microencapsulated fish oil powder.     

Dietary cyanidin 3-O-β-d-glucoside increases ex vivo oxidation resistance of serum in rats

The effect of dietary cyanidin 3-O-β-d-glucoside (C3G), a typical anthocyanin pigment, on the generation of thiobarbituric acid reactive substances (TBARS) during serum formation ex vivo and susceptibility of serum to further lipid peroxidation was studied in rats. Rats were fed a diet containing C3G (2 g/kg) for 14 d. Feeding C3G resulted in a significant decrease in generation of TBARS during serum formation. The serum from the C3G-fed group showed a significantly lower susceptibility to further lipid peroxidation provoked by 2,2′-azobis (2-amidinopropane)hydrochloride or Cu²⁺ than that of the control group. No significant differences were observed in serum phospholipid, triglyceride, esterified cholesterol, and free fatty acid concentrations between the control and the C3G-fed groups. Concentrations of endogenous antioxidants remaining in the serum after blood coagulation were not affected by the C3G feeding. These results demonstrate that feeding C3G increases the ex vivo oxidation resistance of the serum without affecting serum endogeneous antioxidant levels, and reduces the TBARS generated during serum formation without changing the concentrations of serum lipids.