Biometric, nutritional and sensory changes in intensively farmed Murray cod (Maccullochella peelii peelii, Mitchell) following different purging times

A period of purging before harvesting is common practice in intensive aquaculture to eliminate any possible off flavours from the fish. The present study was conducted to evaluate the biometrical, nutritional and sensory changes in intensively farmed Murray cod (Maccullochella peelii peelii) after 0, 2 and 4 weeks of purging. After the main biometric parameters were recorded, fish were analysed for proximate, fatty acid composition and flavour volatile compounds. A consumer preference test (triangle test) was also conducted to identify sensorial differences that may affect the consumer acceptability of the product.

Fish purged for 2 and 4 weeks had a significant weight loss of 4.1% and 9.1%, respectively, compared to unpurged fish, whilst perivisceral fat content did not change. The concentration of saturated (SFA), monounsaturated (MUFA) and highly unsaturated (HUFA) fatty acids were not significantly affected by purging time, while polyunsaturated fatty acids (PUFA), n − 3 and n − 3 HUFA were significantly higher (P < 0.05) in purged fish compared to unpurged fish. Consumers were able to detect differences between the purged and unpurged fish (P < 0.05) preferring the taste of the purged fish. However, consumers were unable to distinguish between fish purged for 2 and 4 weeks.

This study showed that a 2 weeks purging period was necessary and sufficient to ameliorate the final organoleptic quality of farmed Murray cod. With such a strategy the nutritional qualities of edible flesh are improved while the unavoidable body weight loss is limited.

The role of omega-3 fatty acids in mood disorders

Research has established that docosahexaenoic acid (DHA), a long-chain omega-3 polyunsaturated fatty acid (PUFA), plays a fundamental role in brain structure and function. Epidemiological and cross-sectional studies have also identified a role for long-chain omega-3 PUFA, which includes DHA, eicosapentaenoic acid, and docosapentaenoic acid, in the etiology of depression. In the past ten years, there have been 12 intervention studies conducted using various preparations of longchain omega-3 PUFA in unipolar and bipolar depression. The majority of these studies administered long-chain omega-3 PUFA as an adjunct therapy. The studies have been conducted over 4 to 16 weeks of intervention and have often included small cohorts. In four out of the seven studies conducted in depressed individuals and in two out of the five studies in bipolar patients, individuals have reported a positive outcome following supplementation with ethyl-eicosapentaenoic acid or fish oil containing long-chain omega-3 PUFA. In the three trials that researched the influence of DHA-rich preparations, no significant effects were reported. The mechanisms that have been invoked to account for the benefits of long-chain omega-3 PUFA in depression include reductions in prostaglandins derived from arachidonic acid, which lead to decreased brain-derived neurotrophic factor levels and/or alterations in blood flow to the brain.

The role of fatty acids in satiation and satiety

Background – Satiation and satiety describe the events which lead to meal termination and the maintenance of hunger induced by physical and metabolic events following food ingestion. Fatty acids, components of dietary fat (triglyceride) may be important, if not essential components of satiation and satiety. Emerging evidence suggests fatty acid now constitutes a sixth taste modality and orally sensed fatty acids mediate unique cephalic and hormonal responses priming the body for fat digestion, and may contribute to sensory specific satiety. Once ingested, fatty acids are sensed in the gastrointestinal tract (GIT) where they cause the release of hormones, stimulate the vagus and enter the blood stream where they act a number of organs (brain, liver) to influence satiety.
Objective – To review the role of fatty acids in sensory and metabolic satiation and satiety.
Design – Literature search and review of papers from the past decade on satiety, satiation, fat taste and fatty acids.
Outcomes – The physiological significance of gustatory fat detection is still unclear, but it may signal the nutritious content of fat similar to the tastes of sweet or umami which signal the presence of carbohydrate or proteins. Like other tastants, fatty acid taste sensitivity is thought to vary in the population and differences in sensitivity may influence dietary choice and fat intake. Fatty acid taste may contribute to sensory specific satiety as foods are eaten. Animal models have observed an inverse relationship between oral fatty acid sensitivity and fat consumption, which leads to obesity. Observations that the obese have heightened preferences for, and consume more fat than lean individuals questions whether such a relationship may also be apparent in humans. At the GIT, fatty acids are sensed by enterocytes and bind to receptors, transporters or ion channels where they initiate gut-brain communication over nutrient status through the vagus and cause the release of satiety hormones which lead to meal termination. Inefficient fatty acid sensing at either or both locations is thought to accompany the aetiology of obesity.
Conclusion – Variations in sensitivity to fatty acids may alter preferences and consumption of fats or hormonal responses to fat ingestion which influence sensory-specific, metabolic and subjective satiety.

Inhibition of platelet aggregation by omega-3 polyunsaturated fatty acids is gender specific — redefining platelet response to fish oils

Existence of gender differences in cardiovascular disease (CVD) following long-chain omega-3 polyunsaturated fatty acid (LCn-3 PUFA) supplementation have suggested that sex hormones play a role in cardio-protection. The objective of this study was to determine gender specific responses in the efficacy of LCn-3 PUFA to inhibit platelet aggregation in vitro. Blood was analyzed for collagen-induced platelet aggregation following pre-incubation with LCn-3 PUFA in healthy adults (n=42). Eicosapentaenoic acid (EPA) was significantly more effective in reducing platelet aggregation compared with docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). When grouped by gender, this differential pattern was followed in males only. In females, DHA, DPA and EPA were all equally effective. Between group analyses (LCn-3 PUFA vs. gender) showed that both DHA and DPA were significantly less effective in males compared with females. EPA was equally effective in reducing platelet aggregation in both groups. These findings show that significant gender differences exist in platelet aggregation in response to various LCn-3 PUFA treatments.

Production and bioavailability of calcium and magnesium salts of omega-3 fatty acids

In order to provide an alternative to traditional liquid fish oil gelatin capsules, we developed a solid, powdered form of omega-3 fish oil concentrate by forming calcium- and magnesium-fatty acid salts. These salts were produced using a concentrated fish oil ethyl ester that contained in excess of 60% omega-3 fatty acids. The bioavailability of these omega-3 salts was compared with that of fish oil ethyl ester in mice. Animals were given 8 mg of omega-3 fatty acid ethyl ester concentrate (control), calcium- or magnesium-omega-3 salts daily for three weeks. The omega-3 salt products resulted in omega-3 fatty acid content in serum and red blood cell membranes comparable to that produced by the ethyl ester supplementation. In addition, fecal excretion of omega-3 fatty acids was not increased by the presence of calcium or magnesium. In fact, there was a tendency for less omega-3 fatty acids to be excreted.

Associations between fatty acids in colostrum and breast milk and risk of allergic disease

Background Exposure to n-3 polyunsaturated fatty acids (PUFA) in early life is hypothesized to offer protection against atopic disease. However, there is controversy in this area, and we have previously observed that high levels of n-3 fatty acid (FA) in colostrum are associated with increased risk of allergic sensitization.
Objective The aim of the study was to assess the relationship between FA profile in breast milk and risk of childhood atopic disease.
Methods A high-risk birth cohort was recruited, and a total of 224 mothers provided a sample of colostrum (n = 194) and/or 3-month expressed breast milk (n = 118). FA concentrations were determined by gas chromatography. Presence of eczema, asthma and rhinitis were prospectively documented up to 7 years of age.
Results High levels of n-3 22:5 FA (docosapentaenoic acid, DPA) in colostrum were associated with increased risk of infantile atopic eczema [odds ratio (OR) = 1.66 per 1 standard deviation increase, 95% confidence interval (CI) = 1.11–2.48], while total n-3 concentration in breast milk was associated with increased risk of non-atopic eczema (OR = 1.60, 95% CI = 1.03–2.50). Higher levels of total n-6 FA in colostrum were associated with increased risk of childhood rhinitis (OR = 1.59, 95% CI = 1.12–2.25). There was no evidence of associations between FA profile and risk of asthma.
Conclusion In this cohort of high-risk children, a number of modest associations were observed between FA concentrations in colostrum and breast milk and allergic disease outcomes. Further research in this area with larger sample sizes is needed.

Revisiting delta-6 desaturate regulation by C18 unsaturated fatty acids, depending on the nutritional status

Dietary polyunsaturated fatty acids (PUFA) play a key role in regulating delta-6 desaturase (D6D), the key enzyme for long-chain PUFA biosynthesis. Nevertheless, the extent of their effects on this enzyme remains controversial and difficult to assess. It has been generally admitted that C18 unsaturated fatty acids (UFAs) regulate negatively delta-6 desaturase (D6D). This inhibition has been evidenced in regard to a high glucose/fat free (HG/FF) diet used in reference. However, several nutritional investigations did not evidence any inhibition of desaturases when feeding fatty acids.

Because the choice of the basal diet appeared to be of primary importance in such experiments, our goal was to reconsider the specific role of dietary UFAs on D6D regulation, depending on nutritional conditions. For that, sixteen adult Wistar rats were fed purified linoleic acid, α-linolenic acid or oleic acid, included in one of two diets at 4% by weight: an HG/FF or a high starch base (HS) where the pure UFAs replaced a mixed vegetable oil. Our results showed first that D6D specific activity was significantly greater when measured in presence of an HG/FF than with an HS/4% vegetable oil diet. Secondly, we found that linoleic and alpha-linolenic acids added to HG/FF reduced the specific activity of D6D. In contrast, when pure UFAs were added to an HS base, D6D specific activities remained unchanged or increased. Concordant results were obtained on D6D mRNA expression.

Altogether, this study evidenced the importance of the nutritional status in D6D regulation by C18 UFAs: when used as control, HG/FF diet stimulates D6D compared with a standard control diet containing starch and 4% fats, leading to an overestimation of the D6D regulation by UFAs. Then, UFAs should be considered as repressors for unsaturated fatty acid biosynthesis only in very specific nutritional conditions.

Evaluation of novel dairy fatty acids in inflammatory muscle-wasting conditions

This work examined the effects of a novel dairy fatty acid conjugated linoleic acid (CLA) and its effects on muscle wasting in advanced cancer. Results showed a positive anti-inflammatory role of CLA on the supression of tumour growth and established a model for studying the action of CLA in human muscle-wasting conditions.

Docosapentaenoic acid (22:5n-3) : a review of its biological effects

This article summarizes the current knowledge available on metabolism and the biological effects of n-3 docosapentaenoic acid (DPA). n-3 DPA has not been extensively studied because of the limited availability of the pure compound. n-3 DPA is an elongated metabolite of EPA and is an intermediary product between EPA and DHA. The literature on n-3 DPA is limited, however the available data suggests it has beneficial health effects. In vitro n-3 DPA is retro-converted back to EPA, however it does not appear to be readily metabolised to DHA. In vivo studies have shown limited conversion of n-3 DPA to DHA, mainly in liver, but in addition retro-conversion to EPA is evident in a number of tissues. n-3 DPA can be metabolised by lipoxygenase, in platelets, to form ll-hydroxy-7,9,13,16,19- and 14-hydroxy-7,10,12,16,19-DPA. It has also been reported that n-3 DPA is effective (more so than EPA and DHA) in inhibition of aggregation in platelets obtained from rabbit blood. In addition, there is evidence that n-3 DPA possesses 10-fold greater endothelial cell migration ability than EPA, which is important in wound-healing processes. An in vivo study has reported that n-3 DPA reduces the fatty acid synthase and malic enzyme activity levels in n-3 DPA-supplemented mice and these effects were stronger than the EPA-supplemented mice. Another recent in vivo study has reported that n-3 DPA may have a role in attenuating age-related decrease in spatial learning and long-term potentiation. However, more research remains to be done to further investigate the biological effects of this n-3 VLCPUFA.

Suppressive actions of eicosapentaenoic acid on lipid droplet formation in 3T3-L1 adipocytes

Background : Lipid droplet (LD) formation and size regulation reflects both lipid influx and efflux, and is central in the regulation of adipocyte metabolism, including adipokine secretion. The length and degree of dietary fatty acid (FA) unsaturation is implicated in LD formation and regulation in adipocytes. The aims of this study were to establish the impact of eicosapentaenoic acid (EPA; C20:5n-3) in comparison to SFA (STA; stearic acid, C18:0) and MUFA (OLA; oleic acid, C18:1n-9) on 3T3-L1 adipocyte LD formation, regulation of genes central to LD function and adipokine responsiveness. Cells were supplemented with 100 μM FA during 7-day differentiation.

Results : EPA markedly reduced LD size and total lipid accumulation, suppressing PPARγ, Cidea and D9D/SCD1 genes, distinct from other treatments. These changes were independent of alterations of lipolytic genes, as both EPA and STA similarly elevated LPL and HSL gene expressions. In response to acute lipopolysaccharide exposure, EPA-differentiated adipocytes had distinct improvement in inflammatory response shown by reduction in monocyte chemoattractant protein-1 and interleukin-6 and elevation in adiponectin and leptin gene expressions.

Conclusions : This study demonstrates that EPA differentially modulates adipogenesis and lipid accumulation to suppress LD formation and size. This may be due to suppressed gene expression of key proteins closely associated with LD function. Further analysis is required to determine if EPA exerts a similar influence on LD formation and regulation in-vivo.

Oral sensitivity to fatty acids, food consumption and BMI in human subjects

Fatty acids are the chemical moieties that are thought to stimulate oral nutrient sensors, which detect the fat content of foods. In animals, oral hypersensitivity to fatty acids is associated with decreased fat intake and body weight. The aims of the present study were to investigate oral fatty acid sensitivity, food selection and BMI in human subjects. The study included two parts; study 1 established in thirty-one subjects (29 (sem 1·4) years, 22·8 (sem 0·5) kg/m²) taste thresholds using 3-AFC (3-Alternate Forced Choice Methodology) for oleic, linoleic and lauric acids, and quantified oral lipase activity. During study 2, fifty-four subjects (20 (sem 0·3) years, 21·5 (sem 0·4) kg/m2) were screened for oral fatty acid sensitivity using oleic acid (1·4 mm), and they were defined as hypo- or hypersensitive via triplicate triangle tests. Habitual energy and macronutrient intakes were quantified from 2 d diet records, and BMI was calculated from height and weight. Subjects also completed a fat ranking task using custard containing varying amounts (0, 2, 6 and 10 %) of fat. Study 1 reported median lipase activity as 2 μmol fatty acids/min per l, and detection thresholds for oleic, linoleic and lauric acids were 2·2 (sem 0·1), 1·5 (sem 0·1) and 2·6 (sem 0·3) mm. Study 2 identified twelve hypersensitive subjects, and hypersensitivity was associated with lower energy and fat intakes, lower BMI (P < 0·05) and an increased ability to rank custards based on fat content (P < 0·05). Sensitivity to oleic acid was correlated to performance in the fat ranking task (r 0·4, P < 0·05). These data suggest that oral fatty acid hypersensitivity is associated with lower energy and fat intakes and BMI, and it may serve as a factor that influences fat consumption in human subjects.

Transforming salmonid aquaculture from a consumer to a producer of long chain omega-3 fatty acids

Recommendations to endorse the sustainability of wild fish stock utilisation, supporting the health of marine ecosystems, are clashing with those to increase omega-3 fatty acids (n−3 LC-PUFA) consumption and promoting human health.

The objective of this study was to evaluate the role of salmonid aquaculture as a user or supplier of n−3 LC-PUFA, as a means of understanding the potential of the sector in conserving or depleting wild fisheries. A case-study feeding trial was implemented on rainbow trout up to commercial size, in which fish were fed a fish oil- or a linseed oil-diet. Harvested fish were analysed for fatty acid composition and difference and liking using consumers. The n−3 LC-PUFA input/n−3 LC-PUFA output ratio was computed. Consumers showed no preference, but were able to distinguish between samples. The fatty acids of the fillets were significantly modified by the diets. On the input side, for the production of 100 g of fish fillet, it was necessary to use 8.6 g of n−3 LC-PUFA to produce an output of 1.9 g of n−3 LC-PUFA in the fish oil-fed fish; in contrast it was only necessary to use 270 mg of n−3 LC-PUFA to produce 560 mg of these fatty acids in the linseed oil-fed fish. It was showed that the substitution of fish oil with linseed oil in aquafeed is an easily implemented tool to transform salmonids farming from a consumer into a net producer of health promoting n−3 LC-PUFA and accomplish its role in conserving wild fisheries in the future.

Docosapentaenoic acid : its metabolism and effect on lipogenic gene expression

This thesis found that the omega-3 fatty acid, docosapentaenoic acid (DPA) down-regulates the expression levels of key lipogenic genes and proteins in vitro. In vivo studies with labelled DPA showed that, like docosahexaenoic acid, DPA is more conserved from oxidation compared with eicosapentaenoic acid.

Dietary omega-3 fatty acids and depression in a community sample

To evaluate the association between omega-3 polyunsaturated essential fatty acids and depression, data regarding prevalence rates of self-reported depression and median daily dietary intakes of these fatty acids were obtained from an age-stratified, population-based sample of women (n = 755; 23-97 year) in the Barwon Statistical Division of south-eastern Australia. A self-report questionnaire based on Diagnostic and Statistical Manual-IV criteria was utilised to determine 12-month prevalence rates of depression in this sample, and data from biennial food frequency questionnaires examining seafood and fish oil consumption over a 6-year period were examined. Differences in median dietary intakes of omega-3 fatty acids between the depressed and nondepressed cohorts were analysed and results were adjusted for age, weight and smoking status. No significant differences in median intakes were identified between the two groups of women (median, interquartile range; depressed = 0.09g/day, 0.04-0.18 versus nondepressed = 0.11 g/day, 0.05-0.22, p = 0.3), although overall average intakes of omega-3 fatty acids were lower than recommended and rates of depression within this sample higher than expected, based on previous data. Further research that takes into account ratios of omega-6 to omega-3 polyunsaturated essential fatty acids, as well as other dietary sources of omega-3 fatty acids, is warranted.

Solubilization of selected free fatty acids in palm oil by biodegradable ethoxylated surfactants

The solubilization of three major components, viz., palmitic, oleic, and linoleic acids, in palm oil by ethoxylated surfactants was investigated. The results were analyzed in terms of the molecular properties of surfactants and free fatty acids (FFAs). It was found that the solubilities of these FFAs in various micellar solutions depend not only on their octanol−water partition coefficients (Kow), but also on their physicochemical properties. The study on the solubilization kinetics was conducted by choosing palmitic acid as a model solubilizate and Tergitol 15-S-7 as the model surfactant. A first-order film diffusion model, which accounts for the direct uptake of organic molecules at a solid surface into surfactant micelles, was adopted to analyze the effect of surfactant on dissolution of palmitic acid. It was observed that the presence of surfactant reduced the mass-transfer coefficient. Instead, the overall mass-transfer rate was enhanced because of the much higher driving force from the increased solubilization capacity.