Carotenoid Concentration In Flesh Research Articles

Functional characterisation and in silico modelling of MdPSY2 variants and MdPSY5 phytoene synthases from Malus domestica

Carotenoids are plastid isoprenoid pigments that play critical roles in light harvesting, photoprotection, and phytohormone biosynthesis. They are also vitamin-A precursors and antioxidant molecules important for human nutrition. Apples (e.g. Malus x domestica Borkh), one of the most widely consumed fruits with high nutrient levels, have a very low carotenoid concentration in flesh, compared with other fruits and vegetables. This could be explained by a deficiency in carotenoid synthesis/accumulation and/or accelerated degradation. We analysed the contribution of M. domestica cv. ‘Fuji’ phytoene synthase (PSY) in the biosynthesis of carotenoids and determined that among four MdPSY genes present in the organism, MdPSY2 and MdPSY5 are highly expressed in leaves and during fruit ripening in line with an increment in carotenoid content in fruits. Furthermore, two representative polymorphic MdPSY2 variants were found, one with a Tyr358Phe substitution (MdPSY2_F) and the other that additionally has a six-amino-acid deletion in the signal peptide (MdPSY2_CG). MdPSY2, MdPSY5, MdPSY2_F and MdPSY2_CG are all localised in plastids. Interestingly, the polymorphic MdPSY2_F and MdPSY2_CG variants show lower enzymatic activity than the wild-type form in a heterologous complementation assay, which could be attributed to the Tyr358Phe substitution close to the active-site pocket, as was suggested by 3-D modelling analysis. The presence of polymorphic MdPSY2 variants with lower enzymatic activity could be partially responsible for the low carotenoid content in Fuji apple fruits.

Dietary carotenoid levels affect carotenoid and retinoid allocation in female Chinook salmon Oncorhynchus tshawytscha

This study examined the effect of dietary carotenoid availability on carotenoid and retinoid concentrations in the flesh, plasma, skin and eggs of female Chinook salmon Oncorhynchus tshawytscha. Carotenoid concentrations in all tissues were closely related to dietary availability. Early in the breeding season, carotenoids were stored primarily in the muscle, with a flesh carotenoid concentration of 9.9 microg g(-1) in fish fed a high carotenoid diet compared with 1.9 microg g(-1) in fish fed a low carotenoid diet. During the breeding season, carotenoid reserves were mobilized predominantly to the eggs and also to the skin. By the end of the breeding season, carotenoid concentrations in the eggs were 17.9 microg g(-1) in fish fed a high carotenoid diet and 3.9 microg g(-1) in fish fed a low carotenoid diet. Conversely, egg retinoid concentrations were only c. 20% lower in fish fed a low v. high carotenoid diet, which suggests that retinoid concentrations were not limited by the availability of carotenoid precursors. Egg carotenoid concentrations were not correlated with either skin carotenoid concentration or colouration, which suggests that female carotenoid displays are not a reliable signal that males can use to evaluate egg carotenoid resources.

Bacterial protein grown on natural gas as protein source in diets for Atlantic salmon, Salmo salar, in saltwater

Bacterial protein meal (BPM) produced on natural gas was evaluated with respect to growth, nutrient digestibilities, feed conversion ratios, sensory quality, and histopathological indices in Atlantic salmon in saltwater. In the extruded diets, experimentally produced BPM accounted for 0, 10, or 20% of the ingredients or 0, 17.2, or 33.1% of dietary nitrogen, replacing high-quality fish meal. Each diet was fed to two groups of salmon with a mean initial weight of 1.4 kg for 5 months. The pens were organized in two randomized blocks. One block was located with one side of the pens exposed to the open sea. The other block was completely surrounded by other pens. During the experiment, the salmon increased to approximately 3.6–3.9 kg in weight. Analysis of variance revealed no significant ( P>0.05) differences in growth, but regression analysis showed that fish weights at 2 and 5 months and growth rates for the whole experiment were slightly reduced with increasing content of BPM. No significant effects of diet were seen on dressed-out carcass, liver, or intestine to body weight percentages. Carcass and visceral fat and dry matter contents decreased with increasing dietary BPM. There was a trend (0.10≤ P<0.05) that apparent digestibilities of nitrogen, fat, and energy were reduced when substituting fish meal with BPM, while the nitrogen retention was not significantly affected. Flesh carotenoid concentration and colour were not significantly affected by dietary composition, nor were any differences seen for sensory characteristics related to taste, smell or texture. Histological examination did not reveal abnormalities, or signs of allergic reaction against BPM components, and hematocrit values were within normal ranges. Significant block effects were seen for chemical composition of viscera, and digestibilities of nitrogen, fat, and energy.

Bioavailability of all- E-astaxanthin and Z-isomers of astaxanthin in rainbow trout ( Oncorhynchus mykiss)

Two cold-pelleted diets containing either 36.9 or 35.4 mg kg −1 of predominantly all- E-astaxanthin (97% of total astaxanthin) or a mixture of all- E- and Z-astaxanthin (64 and 36%, respectively), were fed to duplicate groups of rainbow trout ( Oncorhynchus mykiss) in freshwater (initial weight 0.4 kg) for 69 days. Average final weight was ca. 1.0 kg for both groups and the specific growth rate was 1.2–1.3% d −1. The all- E- and Z-isomer mixture of astaxanthin was produced from Carophyll Pink ® by an iodine-catalyzed isomerization. Flesh astaxanthin concentrations increased from 1.7 mg kg −1 in the initial sample to 6–7 mg kg −1 after 31 days. After 69 days, flesh carotenoid concentration of the trout fed all- E-astaxanthin tended to be higher than in trout fed the astaxanthin stereoisomer mixture (10.0 and 8.6 mg kg −1, respectively). At the end of the experiment, the trout fed all- E-astaxanthin had significantly redder (through the color tristimuli analysis CIE [1976], a ∗ tristimuli value) flesh than rainbow trout fed a mixture of all- E- and Z-astaxanthin. Apparent digestibility coefficients (ADC) of total astaxanthin were significantly higher in trout fed all- E-astaxanthin (79%) compared to trout fed the stereoisomer mixture (64%). No significant differences in the ADC of all- E-astaxanthin was observed between the two treatments, indicating a competitive mechanism of uptake of the different stereoisomers. ADC of all- E-astaxanthin was higher than that of 9 Z- and 13 Z-astaxanthin, and the ADC of 13 Z-astaxanthin was significantly higher than that for 9 Z-astaxanthin. This indicates that the Z-astaxanthin isomers are not utilized to the same extent as all- E-astaxanthin for flesh pigmentation. No significant differences were observed in total astaxanthin retention in the flesh. However, the retention of all- E-astaxanthin was higher in trout fed the stereoisomer mixture of astaxanthin than in the group fed all- E-astaxanthin. The better utilization of digestible carotenoids in the trout fed a mixture of all- E- and Z-astaxanthin isomers did not fully compensate for the low digestibility of astaxanthin in this group. No differences in astaxanthin stereoisomer composition in the flesh were observed between treatments. This indicates a selectivity in metabolism of the different stereoisomers of astaxanthin, either during absorption, transport or deposition, or their combinations and suggests that substantial isomerization of astaxanthin Z-isomers occurs in the liver. The retention of dietary astaxanthin in the flesh was as high as 24–32%. No significant differences in ADC were observed for dry matter, protein, fat or energy, while ADC for ash was significantly higher for the group fed the diet containing all- E-astaxanthin. The tendency for higher retention of digestible total astaxanthin in the flesh of trout fed a stereoisomer mixture of astaxanthin suggests that the stereoisomer composition of the dietary astaxanthin may influence the absorption capacity and bioavailability of total astaxanthin, probably by increasing intestinal micellar load of total astaxanthin.

Plasma carotenoid concentration indicates the availability of dietary astaxanthin for Atlantic salmon, Salmo salar

Atlantic salmon with an initial weight of 1.1 kg were fed three extruded diets with different amounts of astaxanthin (5, 51 and 61 mg kg −1) in an experiment lasting for 26 weeks. Availability of astaxanthin was assessed after collection of blood plasma from 2 × 10 fish per pen (three pens per diet; two groups of fish per pen, previously unpigmented and pigmented prior to the start of the experiment). The salmon weighed 2–2.5 kg at the time of blood sampling. Correlations were made between mean values for plasma carotenoid concentration and dietary astaxanthin concentration, flesh carotenoid concentration at 24 weeks of feeding, and the amount of carotenoids (mg) retained in flesh per kg body weight increase. There were no differences observed in plasma astaxanthin concentration between salmon which were pigmented or unpigmented prior to the study. The correlation between plasma astaxanthin concentration and dietary astaxanthin concentration was r = 0.90. Plasma astaxanthin concentration and mg astaxanthin retained in flesh per kg body weight increase were also highly correlated ( r = 0.92), as was the correlation between plasma astaxanthin concentration and flesh carotenoid level ( r = 0.95). Plasma astaxanthin concentrations ranged from 0.5 to 5 μg ml −1.

Pigmentation of 1, 2 and 3 year old Arctic charr ( Salvelinus alpinus) fed two different dietary astaxanthin concentrations

Two dietary astaxanthin levels (63 and 114 mg kg −1) were fed to three year classes (1 +, 2 +, 3 +) of Arctic charr in a 25 weeks experiment. Growth were monitored, and at weeks 1, 13 and 25, samples were taken for analysis of total carotenoids in flesh, skin, fins and plasma. The average growth rates were 1.35, 0.73 and 0.44% d −1 for the 1 +, 2 + and 3 + charr respectively. In the 3 + group, growth rate declined towards the end of the experiment, and this was probably a result of sexual maturation. Carotenoid concentrations in the flesh and skin increased throughout the experiment for the 1 + and 2 + fish. For the 3 + fish, which became sexually mature, carotenoid concentration in the flesh increased during the early part of the experiment and then stabilized, whereas the concentration in the skin showed a marked increase. After 13 weeks of feeding, there was an overall tendency ( P = 0.066) towards a higher flesh carotenoid concentration in the fish fed the 114 mg astaxanthin kg −1diet than in the fish fed the 63 mg kg −1 diet, but no significant differences were observed at 25 weeks. Significant differences between year classes were seen in flesh, skin and plasma carotenoid concentrations. After 13 weeks of feeding, the flesh carotenoid concentrations were lowest in the 1 + and highest in the 3 + fish. At the end of the experiment, no differences were seen between the 2 + and 3 + fish, while the 1 + fish were still less pigmented. The carotenoid concentrations in skin after 13 and 25 weeks and in fins after 25 weeks were higher in the 3 + fish than in the other groups. Estimates of astaxanthin deposition in relation to body weight increase revealed that the 1 + group was less efficient at utilizing dietary carotenoids for flesh pigmentation than the older fish. The efficiency with which the dietary astaxanthin was used for flesh pigmentation decreased when the concentration was increased from 63 to 114 mg kg −1.

Strategies for salmonid pigmentation

Well pigmented flesh is regarded second after freshness as one of the most important quality criteria for farmed Atlantic salmon (Salmo salar). The required redness of salmonid flesh has caused a steady increase of astaxanthin concentration in salmonid flesh from about 2–3 mg kg−1 during the 1970s to above 6 mg kg−1 today. An individual variation in flesh pigmentation of more than 100% is experienced under practical as well as experimental conditions. An individual variation of this magnitude makes the precision of carotenoid estimations low, and impairs comparisons of treatments. The present paper discuss the importance of standardisation of the experimental conditions in relation to the level of flesh pigmentation and to variation in populations with the main focus on the effect of fish size, flesh carotenoid concentration and environmental factors.

Pigmentation of rainbow trout from start feeding to sexual maturation

Rainbow trout were fed diets supplemented with either 100 mg astaxanthin/kg [(3 S,3′ S)-, (3 R,3′ S)-, (3 R,3′ R)-optical isomers; 1:2:1], 100 mg canthaxanthin/kg, or without carotenoids added in an experiment lasting for 140 weeks. During the experiment the fish weight increased from 0.13 g to 3 kg. From weeks 23 to 58 after start feeding, astaxanthin was significantly more efficiently utilized for flesh pigmentation than canthaxanthin. The carotenoid concentration in flesh of immature trout fed diets with carotenoids reached a final level of 20 mg/kg. The carotenoid concentration in skin of immature trout fed carotenoids increased during the first 49 weeks and decreased thereafter. The carotenoid concentration in skin of trout fed astaxanthin tended to be higher than that of the fish fed canthaxanthin, while the opposite was found for liver. The total carotenoid contents of sexually mature females and males were 73–79% and 18–19% of that in the immature fish, respectively. The carotenoid content in female gonads increased moderately with sexual maturation, and the carotenoid content in skin of males increased strongly. No significant difference was observed between optical isomer composition of astaxanthin in the flesh and that in feed. Skin of fish fed astaxanthin mainly contained astaxanthin esters and skin of fish fed canthaxanthin contained canthaxanthin and its reductive metabolites. A slight accumulation of the ( 3S,3′S)-isomer of astaxanthin was observed in skin. This was rationalized by accompanied accumulation of ( 3S,3′S)- and ( 3R,3′S)-zeaxanthin.