Fatty acid composition and oxidative stability of oils recovered from acid silage and bacterial fermentation of fish (Sea bass – Dicentrarchus labrax) by‐products

Lipid quality and fatty acid compositions of fish oils recovered from fish (Sea bass – Dicentrarchus labrax) waste silages produced with formic acid (FA) and five different LAB strains (Lactobacillus plantarum (LP), Pediococcus acidilactici (PA), Enterococcus gallinarum (EG), Lactobacillus brevis (LB) and Streptococcus spp. (ST)) were assessed to ensure for the usage for human consumption. Generally, it was observed that there were no significant differences between PUFA contents (23.27–23.64%). Peroxide (PV) (2.12 meq active O₂/per kg of oil) and TBA values (1.07 mg malonaldehyde (MA) g^?1 oil) of fish oils from acid silage were significantly higher than those of the fermented ones (1.14–1.91 meq active O₂ kg^?1, 0.67–0.81 mgMA g^?1 oil, respectively). Anisidine values (AV) were determined in range of 8.04–11.14 for fermented silages and 13.08 from acid silage. The highest totox value (17.33 ± 0.88) was also detected in acid silage oil whereas fermented groups gave totox value in the range of 10.40–13.88. It can be concluded that the initial lipid quality of fermented fish waste silages was better than the initial lipid quality of acid fish waste silage. Therefore, fish oils recovered from fermented silages can be used as food additives or supplements for animal and human diets.     

Effect of gelatin/agar bilayer film incorporated with TiO2 nanoparticles as a UV absorbent on fish oil photooxidation

This research evaluated the effect of gelatin/agar bilayer film and nanocomposites containing different concentrations of TiO₂ nanoparticles (0.5%, 1% and 2%) as ultraviolet (UV) and oxygen barriers on the oxidative stability of fish oil. Samples of fish oil covered with the bilayer films were stored under UV light or in darkness and with or without lids at 18 °C for 12 days. Oil quality in terms of peroxide values (PV), thiobarbituric acid (TBA), conjugated diene (CD), fatty acids profile and colour change (?E) was monitored during storage. Fish oil photooxidation was hindered by increasing TiO₂ concentration, so that nanocomposite containing 2% of the nanoparticles could control photooxidation, similar to the samples stored in darkness. Furthermore, upon studying both photooxidation and autoxidation, the highest amounts of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as the lowest amount of changes in PV, TBA, CD and ?E, were observed in oils covered with the nanocomposites.     

Oxidative Stability of ω3-rich Camelina Oil and Camelina Oil-based Spread Compared with Plant and Fish Oils and Sunflower Spread

ABSTRACT: The oxidative stability of ω3‐rich oil from Camelina sativa and the storage stability of a camelina oil‐based spread were evaluated. Camelina oil was more stable than fish oil and linseed oil, but less stable than sunflower, corn, sesame, and olive oils, indicated by measuring peroxide values (PV), ρ‐anisidine values (AV), total oxidation values (Totox), thiobarbituric acid reactive substances (TBARS), conjugated diene levels (CD), and conjugated triene levels (CT) during storage at 65 °C for 16 d. The camelina oil‐based spread had higher PV, AV, Totox, TBARS, CD, and CT than the sunflower spread but maintained adequate sensory quality for 16 wk of storage at 4 °C or 8 °C.     

Production of Salmon Oil from Filleting Byproducts—Effects of Storage Conditions on Lipid Oxidation and Content of ω‐3 Polyunsaturated Fatty Acids

ABSTRACT: Filleting byproducts (heads, frame bones, skin, and down‐graded gutted fish) from farmed Atlantic salmon (Salmo salar) were separated into a solid/aqueous phase and a lipid phase (oil) using a scraped‐surface heat exchanger (90 °C to 95 °C) and a decanter centrifuge (93 °C). Effects of storage temperature (4 °C and 23 °C), atmosphere (air and N₂), and time (0 to 180 d), as well as an additional process step—a separator introduced after the decanter centrifuge, were investigated on the quality and storage stability of the produced oil. Samples were analyzed for the quality parameters peroxide (PV), anisidine (AV), and Totox value (TxV), content of free fatty acids (FFA), content of fatty acid methyl esters (FAME), especially the n‐3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and degradation of EPA and DHA related to the content of hexadecanoic acid (HDA) (ratios EPA/HDA and DHA/HDA). Storage temperature had significant effect on all the investigated quality parameters, especially on AV, PV, and TxV where a high storage temperature (23 °C) caused a 10‐fold, 2.5‐fold, and 4‐fold increase in AV, PV, and TxV, respectively. Storage atmosphere had significant effect on all the investigated parameters, except on the DHA/HDA ratio, where storage under an N₂ atmosphere significantly preserved the quality of the oil compared with storage in air. Generally, no significant effect of storage time on the investigated quality parameters was observed before 120 d of storage. No effect on quality was observed when introducing an additional processing step (separator) after the decanter centrifuge. Salmon oil is a stable product, and even more so when stored at appropriate conditions (under nitrogen atmosphere at refrigerated temperatures).     

Stabilizing Oils from Smoked Pink Salmon (Oncorhynchus gorbuscha)

ABSTRACT:  Smoking of meats and fish is one of the earliest preservation technologies developed by humans. In this study, the smoking process was evaluated as a method for reducing oxidation of pink salmon ( Oncorhynchus gorbuscha ) oils and also maintaining the quality of oil in aged fish prior to oil extraction. Salmon heads that were subjected to high temperatures (95 °C) during smoking unexpectedly produced oils with fewer products of oxidation than their unprocessed counterparts, as measured by peroxide value (PV), thiobarbituric acid reactive substances (TBARS), and fatty acids (FA). Higher temperatures and longer smoking times resulted in correspondingly lower quantities of oxidative products in the oils. Fatty acid methyl ester (FAME) analysis of smoke-processed oils confirmed that polyunsaturated fatty acids (PUFA) were not being destroyed. Smoke-processing also imparted antioxidant potential to the extracted oils. Even when antioxidants, such as ethoxyquin or butylated hydroxytoluene, were added to raw oils, the smoke-processed oils still maintained lower levels of oxidation after 14 d of storage. However, decreased antioxidant capacity of smoke-processed oils was noted when they were heated above 75 °C. Vitamin studies supported the antioxidant results, with smoke-processed oils displaying higher levels of α-tocopherol than raw oils. Results suggest that smoking salmon prior to oil extraction can protect valuable PUFA-rich oils from oxidation. Improved preservation methods for marine oils may extend their usefulness when added as a supplement to enhance levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in foods.     

Carp (Cyprinus carpio) oils obtained by fishmeal and ensilage processes: characteristics and lipid profiles

Fish oil is an important source of long-chain ω-3 polyunsaturated fatty acid. The common carp ( Cyprinus carp ) is a major fish species in world aquaculture production. This study aimed towards obtaining carp viscera oil by ensilage and fishmeal processes. Characteristics of crude oils obtained were also compared with oil extracted by Bligh and Dyer methods. Crude oils obtained by the three processes resulted in significant difference ( P  < 0.05) for free fatty acids, peroxide, thiobarbituric acid and Lovibond colour values; however, iodine and saponification values were not significantly affected ( P  > 0.05). Recovery yield of crude oils was approximately 85% in relation to carp viscera oil. Carp crude oils obtained by the ensilage and fishmeal processes resulted in high unsaturated and polyunsaturated fatty acid contents (67.4%), and ω3/ω6 ratios around 1.15. These oils are applicable in fish diets; however, crude oils require refinement for human consumption.     

Consequence of Commercial Fish Frying on Some Quality Parameters of Oil with Special Reference to Trans Fat

In the present study, the quality of frying oil, as affected by commercial pan fish frying, was investigated. The quality of fresh frying oil, null replenishment (NR) oil, and discarded frying oil were evaluated by drawing out the oil samples from the fryer at the initial stage, just before the addition of new frying oil for level make-up and used oil of the last frying cycle, respectively. The parameters used to assess the quality were the fatty acid composition including trans fatty acid (TFA), free fatty acid, and peroxide values of frying oil. Gas chromatography-mass spectroscopy (GC-MS) was used to examine fatty acids profiles of the frying oils. Trans fatty acid in fresh oils varied from 2.5%–3.8% (except oil-6, which contained 13%), whereas NR oils and discarded oils contained 5.6%–14.8% and 7.3%–20.8% trans fatty acids, correspondingly. Free fatty acid in fresh, NR, and discarded oils were 0.12%–0.24%, 0.22%–1.74%, and 0.80%–3.39%, respectively. Peroxide value in fresh, NR, and discarded oils were determined to be 1.15–3.93, 2.71–7.51, and 2.84–14.68 meq of O₂ /kg oil. It was observed that commercial fryers were not using the proper oil for frying. Furthermore, the last frying cycle just before discarding the oil may be dangerous for the health of consumers due to their significant level of TFA, free fatty acid, and peroxide values.     

Oxidative stability of camelina oil in salad dressings,mayonnaises and during frying

Oxidative stability of omega‐3 rich camelina oil in food products and during frying was evaluated and compared with sunflower oil. Camelina oil‐based salad dressings were of similar oxidative stability to those prepared with sunflower oil, as indicated by predominantly insignificant (P > 0.05) differences in peroxide values (PV), ρ‐anisidine values (AV), total oxidation values (TOTOX), conjugated diene levels (CD) and conjugated triene levels (CT). However, thiobarbituric acid reactive substances (TBARS) were significantly higher (P < 0.05) for camelina oil and salad dressings throughout storage. Camelina and sunflower oils, alone and in salad dressings or mayonnaises, were acceptable to a sensory analysis panel with slightly lower scores for camelina oil. PV, AV and TOTOX values were similar for camelina and sunflower oil during deep frying but while PVs remained low (<10 meq kg^?1), AV and TOTOX values increased quickly. TBARS values were significantly higher in deep‐frying camelina oil and ‘fishy’ odours were observed.     

Evaluation of the effectiveness of a new active packaging film containing natural antioxidants (from barley husks) that retard lipid damage in frozen Atlantic salmon (Salmo salar L.)

Salmon is a perishable fish that contains high level of PUFAs (polyunsaturated fatty acids), which have many positive effects on human health, but which are extremely susceptible to oxidation. The development of new food packaging films by incorporation of antioxidants is expected to improve the shelf life of food and thus increase consumer safety and health. Determination of peroxide value (PV), conjugated dienes (CD), conjugated triene hydroperoxides (TH), free fatty acids (FFA), totox value (TV), thiobarbituric acid index (TBARS) and p-anisidine value (AV) by established methods proved suitable for studying lipid hydrolysis and primary and secondary lipid oxidation in samples of salmon during frozen storage. The results obtained confirm the efficacy of natural antioxidants derived from barley husks (NABH) in slowing down lipid hydrolysis and increasing the oxidative stability of salmon flesh. This study demonstrates the potential usefulness of natural antioxidants extracted from barley husks in the development of active packaging films for food preservation.     

Fish Oil Dietary Effects on Fatty Acid Composition and Flavor of Channel Catfish

A typical channel catfish diet was supplemented with 0, 1.5, and 3% menhaden oil. Fillets were subjected to lipid, fatty acid, and TBA analyses. After 6 mo storage at ?18°C, fillets were again analyzed for TBA value and flavor panel profile. Fillets from catfish fed diets with 1.5 and 3% supplemental fish oil had elevated levels of n-3 fatty acids (P<0.05). TBA number and off-flavor attributes were not affected by treatments. Menhaden oil supplementation up to 3% enhanced the content of n-3 fatty acids in channel catfish fillets without adversely affecting flavor attributes or storage quality.     

Application of NMR to evaluate the oxidative deterioration of brown fish meal

Peroxide value (PV) and acid value (AV) are generally used as indices of deterioration in edible oil. However, they are not always useful for evaluation of oil deterioration in fish meal because the PV rises at the initial stage of oxidative deterioration, reaches a peak and then declines during long term storage of the meal; the AV hardly changes during long term storage. The use of NMR to evaluate oxidative deterioration of the oil in brown fish meal was examined. The ratio of olefinic protons to aliphatic protons (Ro) in brown fish meal oil determined by NMR decreased steadily with increasing storage time. By comparison with data from measurements of PV and AV, the Ro was considered to be useful as an index of oxidative deterioration in the oil in brown meal, especially in oil where the PV is peaking.     

A process for the synthesis of PUFA-enriched triglycerides from high-acid crude fish oil

This paper reports a research interest, that aims to establish a feasible industrial process, for the enzymatic production of glycerides with highly concentrated n-3 polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid), from high-acid crude fish oils. The process covers enzymatic deacidification of crude fish oil, alkaline-based synthesis of polyunsaturated fatty acids ethyl esters, concentration of polyunsaturated fatty acids ethyl esters, and enzyme catalyzed synthesis of polyunsaturated fatty acids glycerides. Commercial available immobilized lipase, Novozym 435, was used as the catalyst. The synthesized glycerides contained 5.5% of eicosapentaenoic acid and 74.6% of docosahexaenoic acid, which was 1.21 and 2.71 times more than that in the original fish oil, respectively. The application of the designed process was successfully proved by a 100-fold scale-up reaction.     

不同提取方式下小黄鱼下脚料粗鱼油脂肪酸组成及挥发性风味成分的变化

为提高小黄鱼下脚料的高值化利用，研究以小黄鱼下脚料为试材，将其进行前处理分别制成湿样（Wet Sample，W）和干样（Dry Sample，D），采用索氏提取法（Soxhlet Extractor Method，S）及酶解法[碱性蛋白酶（1）、中性蛋白酶（2）、木瓜蛋白酶（3）]提取粗鱼油，对其理化指标进行评价、并分析其脂肪酸组成及挥发性风味成分。结果表明，7种不同提取方式（DS、D1、D2、D3、W1、W2、W3）制备的粗鱼油其理化指标值均满足水产标准（SC/T 3502-2016）三级的规定。所得粗鱼油中棕榈酸（C16:0）、硬脂酸（C18:0）、棕榈油酸（C16:1）、油酸（C18:1n9）均为主要脂肪酸，其中D1处理组粗鱼油EPA和DHA相对含量最高，为25.59%。不同提取方式所提粗鱼油中共检出99种挥发性风味成分，包括醇类16种、醛类16种、酮类15种、酯类3种、酸类8种、碳氢化合物16种、酰胺类化合物3种、杂环化合物及其他22种，其中DS处理组粗鱼油的风味与酶解法相比较差，表明冷冻干燥前处理在一定程度上改善了粗鱼油的风味。综上，采用冷冻干燥前处理结合酶解法对小黄鱼下脚料进行提取，提取得到的粗鱼油的品质优良，就其脂肪酸组成而言，多不饱和脂肪酸含量较高，因此其营养价值较高，且该处理有效改善了粗鱼油的风味，可为小黄鱼下脚料的高值化利用提供一定的理论依据与参考。     

腌腊鱼传统日晒干制过程中品质变化与香气形成

以腌制后的草鱼为研究对象,基于菌落总数、挥发性盐基氮含量、酸价（acid value,AV）、过氧化值（peroxide value,POV）、硫代巴比妥酸（thiobarbituric acid,TBA）值、色差、质构、脂肪酸组成、挥发性风味物质等指标,研究了腌腊鱼传统日晒干制过程中品质变化与香气形成规律。结果显示,菌落总数和挥发性盐基氮含量均随着日晒时间的延长而升高,日晒4?d时两者均达最大值,分别为4.73（lg（CFU/g））和28.39?mg/100?g,说明产品安全性好。随着日晒时间的延长,AV和TBA值不断增加,而POV呈先上升后下降趋势。色差和质构结果表明,日晒过程中腌腊鱼色泽不断变暗,逐步发红和变黄,同时硬度和咀嚼性上升,形成成品特有的“干香”风味。日晒4?d后,腌腊鱼不同脂质成分中多不饱和脂肪酸（polyunsaturated fatty acids,PUFA）相对含量均明显下降,且下降趋势排序为：游离PUFA＞磷脂PUFA＞甘油三酯PUFA。本研究共从腌腊鱼样品中检出了七大类70?种挥发物,筛选确定了己醛等14?种气味活性物质。日晒结束后,腌腊鱼成品中挥发物气味活性值总和从156.67升高至252.88,表明日晒加工对传统腌腊鱼制品的香气形成十分关键。本研究结果可为传统腌腊鱼加工企业完善生产工艺提供理论参考。     

Chemical and nutritional quality of silage made from raw or cooked lizard fish (Saurida undosquamis) and blue crab (Portunus pelagicus)

Twelve silages were prepared from uncooked or cooked lizard fish (Saurida undosquamis) and blue crab (Portunus pelagicus) and stored at ambient temperature (30 ± 2 °C) for 60 days. The antioxidative effect of adding ethoxyquin was also investigated. Generally, the nutritional quality of all the silages was stable for up to 60 days of storage and the composition of raw materials was reflected in the composition of the silages. Crab had a lower level of crude protein than fish (85 versus 162 mg kg^?1), but a higher level of ash (96 versus 36 g kg^?1); moreover, there were significant differences in nutritional composition between uncooked and cooked materials. High level of ash in crab required addition of high levels of formic acid in crab‐related silages. At the end of the experiment cooked silages showed a tendency for spoilage; in particular, maggots were observed in cooked crab silages on the last few days of the experiment. Comparison of treatments with or without ethoxyquin showed that only rancidity of fish silage groups was higher without addition of ethoxyquin. Uncooked materials are more suitable for prolonged storage than cooked materials, and it is probably not necessary to add antioxidants to silages made from material with low lipid content. Copyright © 2009 Society of Chemical Industry     

Physicochemical properties of Kalahari melon seed oil following extractions using solvent and aqueous enzymatic methods

The physico‐chemical properties of oil from Kalahari melon seed were determined following extraction with petroleum ether and aqueous‐enzymatic methods. Two different enzymes Flavourzyme 1000 L and Neutrase 0.8 L were separately used during aqueous‐enzymatic method. The free fatty acid, peroxide, iodine and the saponification values of the oils extracted using the methods were found to be significantly (P < 0.05) different. The melting point of the oils extracted was in the range of ?18.7 °C to ?17.5 °C and no significant (P > 0.05) difference between the oil obtained from solvent and aqueous‐enzymatic extractions was observed. Enzyme‐extracted oil tended to be light‐coloured and more yellow in colour compared with solvent‐extracted oil. The predominant fatty acids in the extracted oils were linoleic acid (62.2–63.1%), with some oleic (16.8–17.1%), palmitic (11.4–12.4%), stearic (7.5–8.1%), linolenic (0.7–1.2%) and eicosenoic (0.3%). Phenolic acids in enzyme‐extracted oils were comparable to the solvent‐extracted oil. The oils extracted with these two methods were differed in the composition of their phytosterol and tocopherol contents, but no significant (P > 0.05) difference between the two enzyme‐extracted oils was observed.     

干制方式对腌腊草鱼脂肪氧化和挥发性风味成分的影响

以不同干制方式制得的腌腊鱼（水分质量分数40%）为对象,基于菌落总数、酸价（acid value,AV）、过氧化值（peroxide value,POV）、硫代巴比妥酸（thiobarbituric acid,TBA）含量、总脂含量与总脂肪酸组成、挥发性风味物质、感官评分等指标,探讨了光照和温度对腌腊鱼风味品质的影响。结果显示：冷风避光组腌腊鱼样品的菌落总数最高,而热风光照组最低,分别为4.42、2.91（lg（CFU/g））。光照组腌腊鱼的脂质氧化指标均高于避光组,两者总脂含量无显著差异（P＞0.05）;热风组腌腊鱼的POV和TBA含量均显著高于冷风组（P＜0.05）,AV和总脂含量显著低于冷风组（P＜0.05）。多不饱和脂肪酸含量占腌腊鱼总脂肪酸含量的40%左右。无论是温度还是光照均对以二十二碳六烯酸为代表的n-3系多不饱和脂肪酸有显著影响（P＜0.05）。感官评价结果表明,冷风组和光照组腌腊鱼样品香气得分均显著高于热风组和避光组（P＜0.05）。本研究共从4 种腌腊鱼样品中检出了82 种挥发性物质,筛选确定了2-壬烯醛等14 种气味活性物质。相同温度下,光照组样品的气味活性值总和显著高于避光组（P＜0.05）,表明光照更有利于香气物质的生成。本研究可为腌腊鱼生产企业改善产品品质提供理论依据。     

Effect of previous chilled storage on rancidity development in frozen horse mackerel (Trachurus trachurus)

Rancidity development during frozen storage (?20 °C) of an underutilised medium‐fat‐content fish species, horse mackerel (Trachurus trachurus), was studied. Special attention was given to the effect of previous chilled storage (0, 1, 3 and 5 days) on the quality of the frozen fish. For this, chemical (free fatty acid and conjugated diene contents; peroxide value, PV; thiobarbituric acid index, TBA‐i; fluorescent compound formation) and sensory (rancid odour and taste) analyses were carried out. Hydrolytic rancidity showed an increase with frozen storage time; however, no effect of previous chilling time was observed on the frozen product. Oxidative rancidity measured by chemical (PV, TBA‐i and fluorescence) and sensory (odour and taste) indices increased with frozen storage time and also with previous chilling time. Satisfactory quality was maintained up to 7 months of frozen storage of horse mackerel provided that a short chilling time (not longer than 3 days) was employed. © 2002 Society of Chemical Industry     

Chemical composition and thermal properties of Tilapia oil extracted by different methods

Fish oil is beneficial to health and its quality is significantly impacted by the extraction method. To determine the effect of various methods used to extract the oil on its chemical composition and thermal properties, tilapia oil extracted by dilute alkali hydrolysis, enzymatic hydrolysis, and microwave-assisted methods were investigated in this study. Nutrient analyses showed that freeze-dried tilapia contained fat (36.69 g/100 g freeze-dried tilapia), protein (49.95 g/100 g freeze-dried tilapia), ash (12.04 g/100 g freeze-dried tilapia) and moisture (1.21 g/100 g freeze-dried tilapia). Chemical analysis showed that the fish oil extracted by dilute alkali hydrolysis had the lowest acid value (AV) and peroxide value (POV) (AV: 0.77 mg KOH/g oil and POV: 3.76 mmol/kg oil) compared to the oil extracted using the other methods. The main fatty acid components were palmitic acid (22.78–23.16%), oleic acid (25.73–26.19%), and linoleic acid (15.69–15.98%). Furthermore, the oil extracted by dilute alkali hydrolysis showed significantly higher content of DHA+ EPA (2.30%). The thermal behaviors indicated that the aforementioned oils had significantly different crystal structures. The main endothermic peaks of fish oil extracted by dilute alkali hydrolysis, enzymatic hydrolysis and microwave-assisted methods were located at ?2.03℃, ?3.20℃ and ?4.37℃, respectively. However, infrared spectroscopic analyses indicated them had the same characteristic functional groups. Consequently, different extraction methods significantly affect the oil’s physical and chemical properties without affecting spectral characteristics. Furthermore, these results advocated the use of alkali hydrolysis for fish oil extraction.     

Oxidative stability of oil from blubber of harp seal (Phoca groenlandica) as assessed by NMR and standard procedures

Oils from seal blubber and cod liver were extracted, refined and bleached in a laboratory scale process. Oxidative stability of oils was evaluated over a 16-day period under accelerated oxidation conditions at 65°C. Peroxide value (PV), contents of conjugated dienes (CD) and trienes (CT), 2-thiobarbituric acid reactive substances (TBARS) and p-anisidine values (AnV) were determined. In addition, NMR spectroscopy was used to monitor relative changes in the proton pattern of the fatty acids of oils during storage. Cod liver oil showed higher PV, CD, CT and TBARS values as compared with seal blubber oil. The ratio of aliphatic to olefinic protons in both oils determined by NMR spectroscopy increased steadily over the entire length of the storage period, indicating progressive oxidation of unsaturated fatty acids in both oils. A significant correlation (P ≤0·05) was found between these ratios and TOTOX values (2PV + AnV) for both oils, thus suggesting that NMR methodology can be used as an effective means to simultaneously estimate both primary and secondary oxidation changes.