Changes in lipids and fishy odour development in skin from Nile tilapia (Oreochromis niloticus) stored in ice

Changes in lipids, lipoxygenase activity and fishy odour development in the skin of Nile tilapia (Oreochromis niloticus) during iced storage of 18 days were monitored. Triacylglycerol content of skin decreased with coincidental increases in free fatty acid, monoacylglycerol, diacylglycerol and phospholipid contents during storage (p < 0.05). During iced storage, peroxide value increased at day 9 and subsequently decreased up to 18 days (p < 0.05). Thiobarbituric acid reactive substances values and lipoxygenase activity increased throughout 18 days of iced storage (p < 0.05). With increasing storage time, a progressive formation of hydroperoxide was found as evidenced by the increase in amplitude of peak at 3600–3200 cm⁻¹ in Fourier transform infrared spectra. Those changes indicated that lipid oxidation took place during iced storage. The increase in fishy odour of skin was observed as the storage time increased. The development of fishy odour in Nile tilapia skin during iced storage was mostly governed by lipid oxidation via autoxidation or induced by lipoxygenase. Thus, the extended storage time of whole fish resulted in the pronounced changes in lipids and the increased fishy odour in the skin.     

The antioxidative properties of mustard leaf (Brassica juncea) kimchi extracts on refrigerated raw ground pork meat against lipid oxidation

The efficacy of varying concentration of mustard leaf kimchi ethanolic extracts (MK) in retarding oxidative rancidity was tested with raw ground pork. Freshly ground pork meat was assigned to one of the following five treatments: control (no antioxidants); AC-0.02 (0.02% ascorbic acid); MK-0.05, 0.1, and 0.2 (0.05%, 0.1% and 0.2% MK, respectively). The pH of the samples decreased and the TBARS values and free fatty acids (%) increased considerably (P < 0.05) during storage. The total bacterial count was lower in MK-0.1 and MK-0.2 than the control during storage. The internal L∗ value and a∗ value decreased (P < 0.05) with the addition of MK. The internal b∗ value of MK treatments were higher (P < 0.05) than that for the control and increased incrementally with MK concentration. The TBARS values and free fatty acids (%) of MK-0.02 was lowest among the treatments. The peroxide value of the control increased until 7 days and reached the maximum value at a certain storage time and decreased thereafter. In the other treatments it increased. All treatments had lower concentration of conjugated dienes (P < 0.05) compared to the control sample, after the first day. Mustard leaf kimchi ethanolic extracts exhibited a protective effect against lipid oxidation in raw ground pork.     

Blending of corn oil with black cumin (Nigella sativa) and coriander (Coriandrum sativum) seed oils: Impact on functionality, stability and radical scavenging activity

Blends (10% and 20%, w/w) of black cumin seed oil (BCSO) and coriander seed oil (CSO) with corn oil (CO) were formulated. Oxidative stability (OS) and radical scavenging activity (RSA) of CO and blends stored under oxidative conditions (60 °C) for 15 days were studied. By increasing the proportion of BCSO and CSO in CO, levels of polyunsaturated fatty acids (PUFA) decreased, while monounsaturated fatty acids (MUFA) content increased. Progression of oxidation was followed by measuring peroxide value (PV), conjugated dienes (CD) and conjugated trienes (CT). Inverse relationships were noted between PV and OS at termination of storage. Levels of CD and CT in CO, and blends, increased with increase in time. CO:BCSO and CO:CSO blends gave 12-22% and 26-36% inhibition of DPPH radicals, respectively. Oxidative stability of oil blends were better than CO, most likely as a consequence of changes in fatty acids and tocopherols’ profile, and minor bioactive lipids (e.g., sterols and phenolics) found in coriander and black cumin oils.     

Effect of fish (Catla catla) frying on the quality characteristics of sunflower oil

The quality of sunflower oil, as affected by fish (Catla catla) frying at 180 °C for 14 h was investigated. The purpose of the study was to find out the quality deterioration of sunflower oil with respect to time as affected by fish frying and to generate equations that can be used for predicting the quality parameters. The physico-chemical characteristics of sunflower oil were evaluated by drawing out the oil samples (75 ml) from the fryer at an interval of 2 h. The parameters evaluated were refractive index, colour, total polar material, free fatty acids, iodine value and peroxide value. There was a gradual increase in refractive index and colour with time of frying which was found to be significant (P < 0.05) in the latter. Iodine value decreased significantly (P < 0.05) with time of frying. Peroxide value first increased up to 12 h of frying and then decreased. After 10 h of frying, the total polar materials were 26.9%, indicating the need for replenishment or refinement of sunflower oil. Total polar material correlated well (r > 0.97) with colour, free fatty acids, peroxide value and time of frying. Free fatty acids correlated well (r > 0.96) with colour, total polar material and duration of frying. Fit of the equations was determined for total polar material and free fatty acids as a function of the respective correlated parameters.     

Changes of lipids in sardine (Sardinella gibbosa) muscle during iced storage

Changes in lipids of sardine (Sardinella gibbosa) muscle during 15 days of iced storage were investigated. Lipid deterioration, lipolysis and lipid oxidation, occurred throughout the storage. The progressive peroxide formation was monitored by the increase in the absorbance band at 3600–3200 cm⁻¹ in Fourier transform infrared (FTIR) spectra and increased peroxide values were observed in sardine muscle up to 6 days of iced storage, followed by a continuous decrease from then for 9 days (P < 0.05). The increase in thiobarbituric acid reactive substances (TBARS) was noticeable throughout the iced storage (P < 0.05). However, no difference in conjugated diene (CD) of sardine muscle was found within the first 12 days of iced storage (P > 0.05). Marked decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n − 3)) and docosahexaenoic acid (DHA; C22:6(n − 3)) were observed as the storage time increased. Those changes indicated that lipid oxidation occurred in sardine muscle. A gradual increase in free fatty acid formation, with decreases in triglyceride and phospholipid contents, was found during iced storage (P < 0.05), suggesting hydrolysis induced by lipases and phospholipases.     

Deodorisation process variables for croaker (M. furnieri) oil

Fish oil is the major food source of the long-chain omega-3 polyunsaturated fatty acids. Deodorisation represents a critical step of the refining process since it involves high temperature that could induce degradation reactions which affect oil integrity and quality. The present study evaluated the effect of the deodorisation variables (temperature, time and steam) on the croaker (Micropogonias furnieri) oil refining process. The evaluated parameters were Lovibond color (LC), free fatty acids (FFA), peroxide (PV), Iodine (IV) and Saponification (SV) values. The best deodorisation conditions were at 220 °C, 60 min and 5% of steam (based in oil mass), resulting in oil with LC of 0.4 red and 30 yellow, FFA of 0.09%, PV of 0.53 meq/kg. IV and SV were not significantly affected. The obtained fish oil presented high quality and oxidative stability, as well as EPA and DHA contents of approximately 12% of total fatty acids.     

Antioxidative properties of Pandanus amaryllifolius leaf extracts in accelerated oxidation and deep frying studies

The potential uses of Pandanus amaryllifolius leaf extract as a natural antioxidant were evaluated in refined, bleached and deodorized (RBD) palm olein, using accelerated oxidation and deep frying studies at 180 °C from 0 to 40 h. The extracts (optimum concentration 0.2%) significantly retarded oil oxidation and deterioration (P < 0.05), comparably to 0.02% BHT in tests such as peroxide value, anisidine value, iodine value, free fatty acid, oxidative stability index (OSI), polar and polymer compound contents. In sensory evaluation studies, different batches of French fries were not significantly different (P < 0.05) from one another for oiliness, crispiness, taste and overall acceptability when the same oil was used for up to the 40th hour of frying. P. amaryllifolius leaf extract, which had a polyphenol content of 102 mg/g, exhibited an excellent heat-stable antioxidant property and may be a good natural alternative to existing synthetic antioxidants in the food industry.     

Stability of docosahexaenoic acid and eicosapentaenoic acid in breads after baking and upon storage

Wholemeal bread and white bread were prepared by substituting shortening with refined menhaden fish oil (0.5%, 1.0% and 1.5% w/w). The stability of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were evaluated over 5 days of storage through gas chromatography (GC) analysis along with peroxide and anisidine value determinations. Sensory analysis was also performed by evaluating the fishy flavour, palatability and palatability differences compared to the control bread upon storage. The recoveries of EPA and DHA in breads after baking were 68.7%–72.8% with no further significant changes (P < 0.05) upon storage for both types of breads. Results from GC analyses correlated well with peroxide and anisidine value analyses, which showed relatively low values throughout the storage time. Omega‐3‐fatty acids from Menhaden fish oil can be incorporated into breads by substituting the shortening at a fish oil level of 0.5% (w/w) with acceptable palatability even after a 3‐day storage period.     

Effects of dietary replacement of fish oil by conjugated linoleic acid on some meat quality traits of Pacific white shrimp Litopenaeus vannamei

This experiment was conducted to evaluate the effects of fish oil replacement by conjugated linoleic acid (CLA) on body proximate analysis and thiobarbituric acid-reactive substances, fat content, shear force and fatty acid composition in musculature of Pacific white shrimp (Litopenaeus vannamei). Graded levels of CLA (0%, 0.5%, 1% and 2%) were added to the basic diet of shrimp at the expense of fish oil. Results showed that fat content (p = 0.036) and shear force (p = 0.001) in shrimp musculature were enhanced with increasing dietary CLA inclusion. Fish oil replacement by CLA significantly promoted the incorporation of cis-9, trans-11 CLA (p = 0.0001) and trans-10, cis-12 CLA (p < 0.0001) into shrimp musculature; moreover, the polyunsaturated fatty acid was elevated (p = 0.020) and monounsaturated fatty acid was reduced by CLA inclusion (p = 0.024). It was concluded that replacement of fish oil by CLA could improve some meat quality traits of shrimp and 1% CLA was an appropriate amount.     

Production and refinement of oil from carp (Cyprinus carpio) viscera

Carp viscera oil can be obtained by both ensilage and fishmeal processes. This study examined the refinement of carp (Cyprinus carpio) oils obtained by both processes, and compared crude, neutralised, bleached, winterised and deodorised oils’ characteristics and lipid profiles. Refined oils obtained by the two processes did not present significant difference (p > 0.05) for Lovibond colour, free fatty acids, and thiobarbituric acid values. The major fatty acids identified in the carp crude, bleached and refined oils were oleic, palmitic, palmitoleic, linoleic and linolenic, constituting approximately 69.6% of the total fatty acids of the oils. The n − 3/n − 6 ratio was approximately 1.05 for refined oil. Therefore, carp viscera refined oil can be considered a rich source of essential fatty acids of the n − 3 and n − 6 series.     

Oxidative stability of lipid components of mullet (Mugil cephalus) roe and its product “bottarga”

The lipid composition and oxidative stability of mullet (Mugilcephalus) raw roes and cured products (bottarga) from two different fishing areas have been studied and compared to find lipid modifications due to manufacturing procedures. Moreover, n-3 PUFA oxidation in raw roes and cured products was monitored during storage at −20 °C, and in grated sample of bottarga at room temperature. Oxidative degradation of n-3 PUFA was evaluated by conjugated dienes fatty acids hydroperoxides determination. The treatments on mullet roe did not affect the lipid level (fatty alcohols and acids, cholesterol) and the amount of hydroperoxides. No significant difference is observed between n-3 PUFA levels during processing and at different storage conditions. The order of oxidative stability, as calculated by the hydroperoxides determination was: grated bottarga < whole bottarga < raw roe.     

Vibrational spectroscopic analysis of hake (Merluccius merluccius L.) lipids during frozen storage

Vibrational spectroscopy (mid FTIR and FT-Raman) was used to monitor lipids extracted from hake fillets during frozen storage. Kramer shear resistance was used as a marker of texture changes and lipid damage was also investigated by following the development of conjugated dienes and free fatty acids by spectrophotometric methods. Results show that the intensity of the free fatty acid carboxylic ν(CO) band measured by ATR-FTIR spectroscopy can be used for monitoring the development of lipid hydrolysis in hake lipids. Changes in the Raman ν(CC) stretching region (1658 cm⁻¹ band), partially attributed to conjugated dienes development, were the only observed spectroscopic alterations related to lipid oxidation of hake lipids during frozen storage at −10 °C. The high correlation of free fatty acids with instrumental texture and the disappearance of the ν_as(PO₂⁻) band are consistent with membrane lipid hydrolysis being one of the factors directly related with toughening of lean fish flesh.     

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei): Compositions and deterioration as affected by iced storage

Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) stored in ice for up to 6 days were extracted and characterised. The extraction yields of lipids from hepatopancreas (10.65–12.64%) were higher than those from cephalothorax (2.59–2.88%). However, no changes in the extraction yield were observed during the storage (p > 0.05). The carotenoid contents of lipids from cephalothorax and hepatopancreas slightly increased within the first 2 and 4 days of iced storage (p < 0.05), respectively, but decreased thereafter (p < 0.05). With increasing storage time, a progressive formation of hydroperoxide was found as evidenced by the increase in the absorbance band at 3600–3200 cm⁻¹ in Fourier transform infrared (FTIR) spectra, and increased peroxide values (PVs) (p < 0.05). The increases in thiobarbituric acid reactive substances (TBARS), p-anisidine value (AnV) and free fatty acid (FFA) content of lipids were noticeable when iced storage time increased (p < 0.05). Those changes indicated that lipid oxidation and hydrolysis occurred in both samples. Phospholipids (PL) were the major components in lipids from cephalothorax (82.51% of total lipids). Nevertheless, lipids from hepatopancreas contained triglyceride (TG) and PL as the dominant components (45.35% and 38.03% of total lipids, respectively). A decrease in the TG content with a concomitant increase in free fatty acid was observed at the end of storage (day 6) (p < 0.05). Decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n-3)) and docosahexaenoic acid (DHA; C22:6(n-3)) were noticeable at day 6 of storage (p < 0.05). Thus, the extended storage time resulted in the enhanced deterioration of extracted lipids.     

Colour,lipid and protein stability of Rhea americana meat during air- and vacuum-packaged storage: Influence of muscle on oxidative processes

Physicochemical characteristics and oxidative stability during storage were determined in Gastrocnemius pars interna (GN) and Iliofiburalis (IF) muscles of Rhea americana. Glycolytic potential (GP) and pH decline of muscles were measured within the first 24 h post mortem. Colour, lipid and protein stability were determined during storage of meat, i.e. 5 days under air-packaging at 4 °C, or 28 days under vacuum-packaging at 4 °C. In parallel, anti-oxidant status of muscles was estimated by measuring α-tocopherol content and anti-oxidant enzyme activities (superoxide dismutase and catalase), while pro-oxidant status was evaluated by determining haeminic iron and long chain fatty acids (especially polyunsaturated fatty acids). The ultimate pH was similar in both muscles, but the GP value was significantly higher in IF than in GN muscle. Haeminic iron and alpha-tocopherol content differed between muscles, with 30% more haeminic iron (p < 0.05) and 134% more alpha-tocopherol (p < 0.001) in IF than GN muscle. The IF muscle presented higher lipid content and lower PUFA/SFA ratio (polyunsaturated fatty acids/saturated fatty acids) than GN muscle. With storage under air-packaging, lipid and protein oxidation of rhea muscles increased up to 275% and 30%, respectively. This increase was more rapidly and marked in IF muscle. The IF also showed high level of metmyoglobin accumulation after 3 days of storage (47%) and was rejected by 1 consumer out of 2 in sensorial analysis. Under vacuum-packaging, both muscles showed a high stability of colour and no oxidation of lipids and proteins.     

Changes in lipids and their contribution to the taste of migaki-nishin (dried herring fillet) during drying

This study was conducted to investigate the changes in lipids and their effect on the taste of migaki-nishin during drying. Lipid was extracted from herring fillets following different drying stages to measure the degree of lipid oxidation and changes in lipid composition, and fatty acid profile. Peroxide value, carbonyl value and acid value of the lipids were significantly increased (P < 0.05) during the drying period. Marked increase in free fatty acids, with decreases in triglyceride and phospholipid content were observed in proportion to drying time and this result suggested that hydrolysis was induced by lipases and phospholipases. The decreases in polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were observed in the total lipids and phospholipid fraction. In addition, significant increase in PUFAs especially DHA was found in the free fatty acid fraction. Sensory evaluation showed that an addition of DHA to mentsuyu significantly (P < 0.05) enhances the intensities of thickness, mouthfulness and continuity. These results suggest that during drying period lipid oxidation was not only occurred but also lipolysis predominantly released DHA, which might have a contribution to kokumi enhancement of migaki-nishin.     

Fatty acid contents evolution and cholesterol oxides formation in Brazilian sardines (Sardinella brasiliensis) as a result of frozen storage followed by grilling

Brazilian sardines (Sardinella brasiliensis) are the main fishery resource commercialized in Brazil. The traditional forms of storage and cooking (frozen and grilling) and its relation to changes of the fatty acids, cholesterol and cholesterol oxidation products (COP) formation were evaluated. Fresh sardines presented an important content of PUFA n-3 fatty acids (11.4±0.5 of eicosapentaenoic acid (EPA) and 16.7±0.3 of docosahexaenoic acid (DHA), g/100 g of the oil), that decreased significantly during processing, as well as the total cholesterol amount, with concomitant formation of cholesterol oxides. The cholesterol oxides determined in sardine samples were 19-hydroxycholesterol, 22(S)-hydroxycholesterol, 24(S)-hydroxycholesterol, 25-hydroxycholesterol, 25(R)-hydroxycholesterol and 7-ketocholesterol, being the main product the 19-hydroxycholesterol. High variations of the total COP contents (19.4±0.4-177.9±1.2 μg/g) was found during the experiment. Cholesterol oxides levels showed a negative correlation (r?0.84) with cholesterol, DHA and EPA content by principal components analysis, whereas cholesterol oxides levels increased while cholesterol, EPA and DHA values decreased in sardines grilled or storage for 120 days.     

Shelf-life prediction of olive oils using empirical models developed at low and high temperatures

Induction period of the formation of hydroperoxides and conjugated dienes at 50 °C and oxidative stability index at 100–130 °C as the oxidative stability measures of different types of olive oils with a wide range of chemical compositions were determined. Regression models (R² ? 0.95) developed at low and high temperatures showed different contributions of compositional variables (the ratio between monounsaturated and polyunsaturated fatty acids, the content of total tocopherols and phenolics, peroxide value, acid value, and total polar compounds content) to the oxidative stability measures. To estimate the shelf-life of olive oils at low temperature, three empirical models with errors of ±1.5%, <±10%, and ±21.2% were developed.     

Extraction and characterisation of lipids from Antarctic krill (Euphausia superba)

There is significant commercial interest in oil extraction from krill because it is rich in omega-3 polyunsaturated fatty acids (n-3 PUFA) such as eicosapentaenoic (EPA, 20:5n3) and docosahexaenoic (DHA, 22:6n3) acids. The objectives were to determine oil extraction efficiency using different solvent systems and the composition of extracted oil and spent krill following extraction. Extraction efficiency was the highest (P < 0.05) for one-step extraction using freeze-dried krill with 1:12 or 1:30 krill:solvent ratio (w:v) compared to Folch, Soxhlet, and conventional two-step extraction. Extracted oils contained predominantly phospholipids (20–33%), polar non-phospholipids (64–77%), and minor triglycerides (1–3%). Triglycerides contained much less (P < 0.05) total n-3 (4.0%), DHA (1.1%), and EPA (2.3%), but more (P < 0.05) saturated FA (38.7%) than phospholipids (total n-3-47.4%, DHA-18.0%, EPA-28.2%, saturated FA-23.5%). Antioxidant capacity of krill oil extracted by one-step extraction (9.4–14.2 μmol Trolox Equivalents/ml oil) was generally similar to antioxidant capacity of krill oil extracted by ethanol (22.9), but greater (P < 0.05) than antioxidant capacity of krill oil extracted by acetone (1.2) and Folch method (1.5). The spent krill following oil extraction contained protein (72.9–75.8%, dry basis). Based on the extraction efficiency and composition of the extracted oil, the one-step extraction using 1:12 krill:solvent ratio is recommended.     

Chemical analysis and preliminary toxicological evaluation of Garcinia mangostana seeds and seed oil

The chemical analysis and preliminary toxicological evaluation of Garcinia mangostana seeds and seed oil have been investigated in order to determine the possibility of using them for human and/or animal consumption. Proximate analysis showed that the seeds had high amount of carbohydrate and were rich in oil (21.68 ± 6.18%) but have a low protein content. The physical properties of the oil extracts showed the state to be liquid at room temperature (25 ± 1 °C) and the colour of the oil golden-orange. The specific gravity of the oil was 0.98 ± 0.01. Among the chemical properties of the oil extracts, acid value, saponification number, iodine value, percent free fatty acid and peroxide value compared well with those of conventional edible oils. The seed flour was found to be a good source of minerals. It contained considerable amounts of potassium (7071 mg/kg), magnesium (865 mg/kg) and calcium (454 mg/kg). Fatty acid composition of the seed oil indicated that the oil contained one essential fatty acids small proportions: linoleic acid (1.30%). The most prevalent fatty acids were palmitic acid (49.5%) and oleic acid (34.0%). Weanling albino rats appeared to suffer no toxicological effects when fed with G. mangostana seed oil in their diet for 8 weeks. Weekly monitoring of the rats showed good physical appearance and steady weight increase. Histological examination of sections of the heart, liver, kidney, spleen and lung revealed that the kidney of some of the rats had some degrees of pathology which included diffuse glomerular and tubular degeneration. No lesion was found in the heart and liver of the rats. The seed oil could be useful as an edible oil and for industrial applications.     

Antioxidative effect of added dried Holy basil and its ethanolic extracts on susceptibility of cooked ground pork to lipid oxidation

Efficacy of varying concentrations of dried Holy basil powder and its ethanolic extracts in retarding oxidative rancidity was tested with cooked ground pork. The development of lipid oxidation products during 14 days refrigerated storage (5 °C) was evaluated by means of thiobarbituric acid-reactive substances (TBARS) value, peroxide value (POV), conjugated diene and hexanal content. In the amounts studied, dried Holy basil powder and its ethanolic extract significantly (P < 0.05) inhibited the formation of TBARS, peroxide, conjugated dienes and hexanal in a dose-dependent manner. The oxidation process was significantly (P < 0.05) influenced by the type of antioxidant and its concentration. Addition of dried Holy basil powder to cooked ground pork was more effective in inhibiting lipid oxidation than its ethanolic extracts. Additionally, TBARS values and hexanal contents in cooked ground pork were highly correlated (r² = 0.95; P < 0.05) with each other.