Effects of dietary lipid source on fillet chemical composition, flavour volatile compounds and sensory characteristics in the freshwater fish tench (Tinca tinca L.)

Unraveling the relationship between aroma characteristics and lipid profile of abalone (Haliotis discus hannai) during seasonal fluctuation and thermal processing

Abalone, a highly sought-after aquatic product, possesses significant nutritional value. In this study, the relationship between aroma characteristics and lipid profile of abalone (Haliotis discus hannai) during seasonal fluctuation and thermal processing were profiled via volatolomics and lipidomics. 46 aroma compounds and 371 lipids were identified by HS-SPME-GC-MS and UPLC-Q-Extractive Orbitrap-MS, respectively. Multivariate statistical analysis indicated that carbonyls (aldehydes and ketones) and alcohols were the characteristic aroma compounds of abalone. The fluctuations in the aroma compound and lipid composition of abalone were consistent with the seasonal variation, especially seawater temperature. In addition, based on the correlation analysis, it was found that carbonyls (aldehydes and ketones) and alcohols had a positive correlation with phospholipids (lysophosphatidylethanolamines and lysophosphatidylcholines), while a negative correlation was observed with fatty acyls. These findings suggested that the effect of seasonal variations on the aroma changes of abalone might achieved by modulating the lipids composition of abalone.

Effects of Substituting Tenebrio molitor and Elodea nuttallii as Feed on Growth, Flesh Quality and Intestinal Microbiota of Red Swamp Crayfish (Procambarus clarkii)

This study aimed to evaluate the impact of substituting a portion of feed with Tenebrio molitor (TM) and Elodea nuttallii (EN) on crayfish culture. A total of 270 crayfish (5.1 ± 0.4 g) were fed three different diet combinations (A: 100% feed; B: 80% feed + 10% TM + 10% EN; C: 75% feed + 15% TM + 10% EN) for 12 weeks. The findings demonstrated that group C had an important beneficial impact on the growth performance of crayfish. This was evidenced by a rise in digestive enzyme activity (trypsin, lipase, and cellulase) in the intestinal and hepatopancreas, as well as an upregulation in the expression of growth-related genes (ghsr, igfbp7, mhc, mlc1, mef2, and pax7) in the muscle. Furthermore, the assessment of the flesh quality of crayfish muscle in group C was conducted. The findings indicated a significant increase (p < 0.05) in the energy value (moisture, crude protein, and crude lipid) within the muscle. The levels of delicious amino acids (Glu, Ala, Ser, Gly, and Tyr) and polyunsaturated fatty acids (ARA, DHA) were enhanced, resulting in an improved nutritional profile and flavor of the muscle while maintaining the Σn-3/Σn-6 ratio. The remodeling of the intestinal microbiota (abundance of Proteobacteria and ratio of Firmicutes/Bacteroidota bacteria) also revealed improved growth performance. Additional research is necessary to ascertain whether excessive use of TM or EN feed substitution can have negative effects on crayfish culture.

Improvement in Muscle Fatty Acid Bioavailability and Volatile Flavor in Tilapia by Dietary α-Linolenic Acid Nutrition Strategy

To investigate the modification of muscle quality of farmed tilapia through dietary fatty acid strategies, two diets were formulated. Diet SO, using soybean oil as the lipid source, and diet BO, using blended soybean and linseed oils, each including 0.58% and 1.35% α-linolenic acid (ALA), respectively, were formulated to feed juvenile tilapia for 10 weeks. The muscular nutrition composition, positional distribution of fatty acid in triglycerides (TAGs) and phospholipids (PLs), volatile flavor, lipid mobilization and oxidation were then analyzed. The results showed that there was no distinct difference between the SO and BO groups in terms of the nutrition composition, including crude protein, crude lipid, TAGs, PLs, and amino acid. Although the fatty acid distribution characteristics in ATGs and PLs showed a similar trend in the two groups, a higher level of n-3 PUFA (polyunsaturated fatty acid) and n-3 LC-PUFA (long-chain polyunsaturated fatty acid) bound to the glycerol backbone of TAGs and PLs was detected in the BO group than the SO group, whereas the opposite was true for n-6 PUFA. Additionally, the muscular volatile aldehyde and alcohol levels were higher in the BO group. Moreover, the expression of enzymatic genes and protein activities related to lipid mobilization (LPL, LPCAT, DGAT) and oxidation (LOX and GPX) was higher in the BO group. The results demonstrate that high-ALA diets may improve the fatty acid bioavailability and volatile flavor of tilapia by improving the lipid mobilization and oxidation, which provides new ideas for the improvement of muscle quality in farmed fish.

Effects of Five Lipid Sources on Growth, Hematological Parameters, Immunity and Muscle Quality in Juvenile Largemouth Bass (Micropterus salmoides)

This study investigated the effects of fish oil (FO), soybean oil (SO), rapeseed oil (RO), peanut oil (PO) and lard oil (LO) on growth, immunity and muscle quality in juvenile largemouth bass. After 8 weeks, the results showed that FO and RO could increase weight gain and serum alkaline phosphatase and apelin values compared with LO (p < 0.05). Except lower crude lipid contents, higher amounts of n-3 polyunsaturated fatty acids (15.83% and 14.64%) were present in the dorsal muscle of the FO and RO groups. Meanwhile, FO and RO could heighten mRNA levels of immune defense molecules (lysozyme, hepcidin, and transforming growth factor β1) compared with PO (p < 0.05). While SO could increase potential inflammatory risk via rising counts of white blood cells, platelets, neutrophils and monocytes, and mRNA levels of interleukins (IL-1β, IL-8, IL-12 and IL-15), FO and RO could improve hardness, chewiness and springiness through increasing amounts of hydroxyproline, collagen and lysyl oxidase, and mRNA levels of collagen 1α2 and prolyl hydroxylase in the fish dorsal muscle. Moreover, FO and RO could improve firmness through increasing glycogen and glycogen synthase 1 levels when compared with LO (p < 0.05). Therefore, these results could provide dietary lipid source references during the feeding process of adult largemouth bass.

Characterization and finding the origin of off-flavor compounds in Nile tilapia cultured in net cages in hydroelectric reservoirs, São Paulo State, Brazil

An increasing demand for fish products has led to an intensive aquaculture production in Brazil, and cultivation of fish constituted 860 × 103 tons in 2022, contributing to the 87% of total fish consumption. Nile tilapia constitutes almost half of the aquaculture production, and most tilapia farms use floating net cages. One of the major constraints of intensive fish production is production of off-flavors. Release of nutrients by the fish leads to deterioration of the water quality and stimulates growth of microorganisms, also including off-flavor producing species. The objective of this study was to determine levels of taste and odor compounds (geosmin, 2-MIB and a selection of volatile compounds) and their impact on the flavor quality of Nile tilapia produced in net cages in reservoirs in São Paulo State, Brazil. GC-MS analysis of fish and water from six different farms showed concentrations of geosmin in the water from 1 to 8 ng/L, while geosmin in fish flesh ranged from 40 to 750 ng/kg. The level of 2-MIB in water was 2 to 25 ng/L, and 0 to 800 ng/kg fish. The GC-MS analysis also revealed presence of more than 100 volatile organic compounds in the fish flesh, consisting of aldehydes, alcohols, benzene derivatives, hydrocarbons, ketones and few other compounds. Geosmin and 2-MIB related flavor notes were detected in all fish by a sensory panel, and a high correlation between the chemical and sensory analyses was found. The potential impact of the volatile organic compounds on the fish flavor is discussed. Analysis of the water quality in the reservoirs indicated that levels of geosmin and 2-MIB levels were highly influenced by the nutrient levels in the water.

Characterizing and Decoding the Effects of Different Fermentation Levels on Key Aroma Substances of Congou Black Tea by Sensomics

Fermentation is the key technology for black tea aroma formation. The key aroma substances of black tea at different fermentation stages (unfermented (WDY), underfermented (F1H), fully fermented (F4H), and overfermented (F8H)) were characterized by the methodology of Sensomics. Aroma extract dilution analysis was performed on volatile fractions extracted by using solvent-assisted flavor evaporation and solid-phase microextraction, yielding 93 odor-active areas. Internal standard method plus stable isotope dilution analysis was used for quantitative analysis. The omission experiment identified 23 aroma substances. Further reduction and addition experiments revealed phenylacetaldehyde, (E,E)-2,4-heptadienal, geraniol, linalool, β-damascenone, 2-methylbutyraldehyde, dimethyl sulfide, and isovaleraldehyde with odor activity values (OAV) > 100 as the characteristic aroma components of F4H and also as the main contributors to aroma differences between different fermentation degrees. The green odor of (E,E)-2,4-heptadienal was highlighted in WDY and F1H relative to that in F4H due to the lower contribution of phenylacetaldehyde and β-damascenone in the former two samples. Additionally, excessive OAV increase of fatty aldehydes in F8H masked its similar floral and fruity aroma.

Effects of Dietary Protein and Lipid Levels on Growth, Metabolism, Antioxidative Capacity, and Fillet Quality of Adult Triploid Rainbow Trout Farmed in Net Cage

The research is aimed at investigating the effects of dietary protein and lipid levels on adult triploid rainbow trout growth performance, feed utilization, digestive and metabolic enzyme activities, antioxidative capacity, and fillet quality. Nine diets containing three dietary protein levels (DP) (300, 350, and 400 g kg^-1) and three dietary lipid levels (DL) (200, 250, and 300 g kg^-1) were prepared using a 3 × 3 factorial design. In freshwater cages, 13,500 adult female triploid rainbow trout (3.2 ± 0.1 kg) were cultured for 77 days. Triplicate cages (500 fish per cage) were used as repetitions of each experimental diet. The findings revealed that as DP increased to 400 g kg^-1 and DL raised to 300 g kg^-1, the weight gain ratio (WGR) elevated significantly (P < 0.05). However, when DP ≥ 350 g kg^-1, WGR was similar in the DL250 and DL300 groups. As DP raised to 350 g kg^-1, the feed conversion ratio (FCR) notably decreased (P < 0.05). In the DP350DL300 group, lipids had a protein-sparing impact. High DP diet (400 g kg^-1) generally improved fish health status by increasing antioxidant capacity in the liver and intestine. A high DL diet (300 g kg^-1) showed no harmful effect on hepatic health based on plasma levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and antioxidant capacity in the liver. For fillet quality, a high DP diet could increase fillet yield, improve fillet hardness, springiness, and water-holding capacity values, and inhibit the production of off-flavors caused by n-6 fatty acids. A high DL diet could increase odor intensity, and EPA, DHA, and n-3 fatty acid concentrations decrease the thrombogenicity index value. The maximum fillet redness value was discovered in the DP400DL300 group. Overall, for adult triploid rainbow trout (≥3 kg), the minimum recommended DP and DL according to growth performance were 400 and 250 g kg^-1, respectively; DP and DL based on feed utilization were 350 and 200 g kg^-1, respectively; DP and DL based on fillet quality were 400 and 300 g kg^-1, respectively.

GC-MS-Olfactometric characterization of key odorants in rainbow trout by the application of aroma extract dilution analysis: Understanding locational and seasonal effects

The effect of seasonal and regional differences of rainbow trout on its aroma and aroma-active profile was investigated. Solvent-assisted flavor evaporation (SAFE) procedure was employed for the aroma extraction while Gas Chromatography-Mass Spectrometry-Olfactometry (GC-MS-O) and aroma extract dilution analysis (AEDA) were utilized to assess the aroma-active substances. The olfactometric analysis indicated seasonal and regional differences in the aroma-active compounds contributing to the characteristic odours of the trout samples and the compounds were more intense in autumn and winter. The strongest aroma-actives were hexanal (green), acetoin (buttery, green), limonene (citrus), 2-hexanol (green, pungent) and 1-octen-3-ol (oily, mushroom). The findings of this study can provide useful information for the selection of rainbow trout based on the seasons and locations in terms of marketing and consumer preference.

Recovery of Fatty Acid and Volatile Flavor Compound Composition in Farmed Tiger Puffer (Takifugu rubripes) with a Fish Oil-Finishing Strategy

Booming fish farming results in a relative shortage of fish oil (FO) supply, meaning that alternative oils are increasingly used in fish feeds, which leads to reduction of long-chain polyunsaturated fatty acids (LC-PUFAs) and other relevant changes in fish products. This study investigated the efficacy of an FO-finishing strategy in recovering the muscle quality of farmed tiger puffer. An eight-week feeding trial (growing-out period) was conducted with five experimental diets, in which graded levels (0 (control), 25, 50, 75, and 100%) of added FO were replaced by poultry oil (PO). Following the growing-out period was a four-week FO-finishing period, during which fish in all groups were fed the control diet. Dietary PO significantly decreased the muscle LC-PUFA content, whereas in general, the FO-finishing strategy recovered it to a level comparable with that of the group fed FO continuously. The recovery efficiency of EPA was higher than that of DHA. Dietary PO also led to changes of volatile flavor compounds in the muscle, such as butanol, pentenal, and hexenal, whereas the FO-finishing strategy mitigated the changes. In conclusion, the FO-finishing strategy is promising in recovering the LC-PUFA and volatile-flavor-compound composition in farmed tiger puffer after the feeding of PO-based diets.

Evaluation of fatty acid-related nutritional quality indices in processed and raw (Lethrinus lentjan) fish fillets

The Lethrinus lentjan fish is economically and nutritionally important in Iran. Therefore, knowledge of their chemical composition can help in the development of functional foods. In the present study, proximate and fatty acid compositions were determined in fresh and marinated Lethrinus lentjan fish. Fatty acids were identified by gas chromatography. The 24 pieces of fresh L. lentjan fish with an average weight of 470 ± 125 g were prepared. After removing wastes, the fish fillet was placed in a dish containing acetic acid, salt, garlic, and red pepper. The marinade product contained n-6PUFA (7.94%) and n-3PUFA (3.46%). The results showed that moisture content in the marinade sample decreased, while fat, protein, and ash contents increased and carbohydrate content was also decreased compared to the raw sample. The marinating process increased PUFA percentage (19.32%) and ratio of PUFA and SFA (0.61). The fresh and processed samples showed superior nutritional quality and the lowest h/H ratio, but AI and TI ratios were relatively favorable (p < .05). The thrombogenicity index (TI) (0.46) and atherogenicity index (AI) (3.56) were more than the recommended in terms of risk of coronary heart disease. It can be concluded that fresh and processed fish samples represent an excellent source of high-quality fat, demonstrating that this fish species' freshwater can be considered optimal for human consumption.

Does Dietary Lipid Level Affect the Quality of Triploid Rainbow Trout and How Should It Be Assessed?

Organoleptic properties and nutritional value are the most important characteristics of fish fillet quality, which can be determined by a series of quality evaluation indexes and closely related to fish nutrition. Systematic organoleptic and nutritional quality evaluation indexes consisting of 139 indexes for physical properties and chemical compositions of triploid rainbow trout were established. Besides, effects of dietary lipid levels (6.6%, 14.8%, 22.8% and 29.4%) on the quality of triploid rainbow trout were analyzed in the study. The main results showed that, for fillet appearance quality, fish fed diets with lipid levels above 22.8% had higher fillet thickness and redness but lower gutted yield and fillet yield (p < 0.05). For fillet texture, fish fed the diet with a 6.6% lipid level had the highest fillet hardness (5.59 N) and lowest adhesiveness (1.98 mJ) (p < 0.05), which could be related to lipid, glycogen, water soluble protein and collagen contents of the fish fillet. For fillet odor, the odor intensity of “green, fatty and fishy” significantly increased with the increase of the dietary lipid level (from 1400 to 2773 ng/g muscle; p < 0.05), which was related to the degradation of n-6 and n-9 fatty acids. For fillet taste, a high lipid diet (≥22.8%) could increase the umami taste compounds contents (from 114 to 261 mg/100 g muscle) but decrease the bitterness and sourness taste compounds contents (from 127 to 106 mg/100 g muscle and from 1468 to 1075 mg/100 g muscle, respectively) (p < 0.05). For nutritional value, a high lipid diet could increase the lipid nutrition level (such as the content of long chain polyunsaturated fatty acids increased from 3.47 to 4.41 g/kg muscle) but decease tryptophan and selenium content (from 2.48 to 1.60 g/kg muscle and from 0.17 to 0.11 g/kg muscle, respectively). In total, a high lipid diet could improve the quality of triploid rainbow trout. The minimum dietary lipid level for triploid rainbow trout should be 22.8% to keep the better organoleptic and nutritional quality.

Effects of dietary α-linolenic acid/linoleic acid ratio on growth performance, tissue fatty acid profile, serum metabolites and Δ6 fad and elovl5 gene expression in silver barb (Puntius gonionotus)

BACKGROUND

Silver barb (Puntius gonionotus) is a medium-sized carp that is promising for freshwater aquaculture in Asia. This study's aim was to investigate the ideal dietary α-linolenic acid (ALA): linoleic acid (LA) ratio for maximizing long-chain polyunsaturated fatty acid (LC-PUFA) synthesis and their deposition in the muscle of silver barb, as that of fish oil based control diet.

RESULT

Fish (with an initial body weight of 11.07 ± 0.12 g) were fed for 60 days with five experimental iso-proteinous, iso-lipidic, and iso-caloric diets, supplemented with linseed oil and peanut oil at varying levels to obtain ALA:LA ratios of 0.35, 0.51, 0.91, 2.04, 2.66. A control diet was prepared by supplementing fish oil. The dietary ALA:LA ratio did not influence the growth performance of fish. With increased dietary ALA:LA ratios, LA content decreased and ALA content increased in the muscle and liver of silver barb. The n-3 LC-PUFA level in muscle and liver was not influenced by feeding different ratios of ALA:LA, whereas n-6 LC-PUFA was decreased in the muscle and increased in the liver with increased dietary ALA:LA ratios. Increasing dietary ALA:LA ratio increased the Δ6fad and elovl5mRNA expression in the liver, muscle, brain, and intestinal tissues of silver barbs.

CONCLUSION

Silver barb possess the ability to elongate and desaturate ALA and LA to their end products EPA and DHA. The highest level expression of Δ6 fad and elovl5 mRNA at the dietary ALA:LA ratio of 2.66 suggests greater affinity of these enzymes towards ALA than LA in silver barb. © 2019 Society of Chemical Industry.

Modification of nutritional values and flavor qualities of muscle of swimming crab (Portunus trituberculatus): Application of a dietary lipid nutrition strategy

Lipid sources as alternatives to fish oil could alter the nutritional value and flavor quality of crab meat affecting consumer preferences. Herein, an 8-week nutritional trial was designed to investigate the effects of dietary lipid sources including fish oil (FO), krill oil (KO), palm oil, rapeseed oil, soybean oil and linseed oil on profiles of amino acids, fatty acids and volatiles in muscle of swimming crab (Portunus trituberculatus). Volatiles of crab muscle were characterized by headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry. Results revealed that crabs fed FO and KO had significantly higher levels of protein, indispensable amino acids, eicosapentaenoic acid and docosahexaenoic acid in muscle. Principal component analysis and hierarchical cluster analysis demonstrated that muscle volatiles of crabs fed different dietary oils exhibited significant variations. Dietary FO and KO significantly increased the relative levels of 3-methylbutanal, heptanal, benzaldehyde and nonanal in muscle, which may produce more pleasant flavors.

Effects of dietary replacement of fish oil by vegetable oil on proximate composition and odor profile of hepatopancreas and gonad of Chinese mitten crab (Eriocheir sinensis)

Five different diets with different ratio of fish oil to vegetable oil were prepared. The biological index and proximate composition of Eriocheir sinensis fed with different diets were compared, and then sensory analysis, electronic nose (E-nose) and headspace-solid phase micro-extraction combined with gas chromatography-mass spectrometer (HS-SPME-GC-MS) analysis were applied to determine the odor profile of E. sinensis. The results showed that partial replacement (50%-75%) of fish oil by vegetable oil (FO/VO) was beneficial to the weight increment, nutrition accumulation, and odor-active compounds (OACs) formation of E. sinensis. A total of 7 and 11 OACs were detected in the hepatopancreas and gonad, respectively, these OACs contributed greatly to the overall odor profiles of E. sinensis when the dietary replacement levels were at 50% and 75%, respectively. The results could provide the guide for dietary fish oil replacement as well as improving the odor quality of E. sinensis. Practical application The objective of this research is to compare the effects of dietary replacement of fish oil by vegetable oil on proximate composition and odor profiles of E.sinensis. The results obtained from this study would not only chose an optimal dietary replacement level and serve as a useful database for the odor of female and crabs, but also provide some guide for the improvement of Chinese mitten crab aquaculture.

Odorants in Fish Feeds: A Potential Source of Malodors in Aquaculture

Although the microbiota is considered to be the primary source of off-flavors in farmed fish, there is a lack of information about the possible contribution of feeds to fish malodor. For this reason, the current study was designed to perform comprehensive sensory and chemo-analytical characterization of fish feed constituents that can impact the quality of farmed fish, and to determine whether feeds cause malodor accumulation in fish. To this aim, odorants in four commercial fish feeds were extracted using solvent assisted flavor evaporation (SAFE) and characterized by comparative aroma extract dilution analysis (cAEDA) and multi-dimensional gas chromatography-mass spectrometry/olfactometry (MD-GC-MS/O). The odorants in the fish feed samples were correlated with their respective sensory and fatty acid profiles. The cAEDA studies revealed the presence of 81 odorants of which 55 compounds were common to all the samples. Most of these odorants are identified here for the first time in fish feeds, and include skatole, indole, (E,Z,Z)-2,4,7-tridecatrienal, 4-ethyloctanoic acid, and cresols. Additionally, geosmin and 3-isopropyl-2-methoxypyrazine, known for their contribution to fish taint, and other cyanobacterial by-products, dimethyldisulfide and dimethyltrisulfide, were identified in feed samples. The results suggest that fish feed may contribute to fish malodor. Most of these off-flavors were linked to lipid source (fish oil or plant/lard alternatives), unsaturated fatty acids contents, and protein type (plant-based or fishmeal-based sources) in the feed.

Impact of Diets Containing Plant Raw Materials as Fish Meal and Fish Oil Replacement on Rainbow Trout (Oncorhynchus mykiss), Gilthead Sea Bream (Sparus aurata), and Common Carp (Cyprinus carpio) Freshness

The present study aimed to evaluate whether the total or high substitution of fish meal (FM) and fish oil (FO) by sustainable plant raw materials (plant meal and oils) in long-term feeding for rainbow trout, gilthead sea bream, and common carp can result in spoilage alterations during ice storage. These three species were fed throughout their whole rearing cycle with plant-based diets and compared to counterparts that received FM/FO-based diets or commercial-like diets. Sensory QIM schemes adopted for these species and ATP breakdown products (K-value and components) were used to evaluate the freshness. Sensory acceptability of 14, 15, and 12 days was found for rainbow trout, gilthead sea bream, and common carp, respectively. This corresponded to K-values of approximately 80%, 35%, and 65% for rainbow trout, gilthead sea bream, and common carp, respectively. No major effect of dietary history on postmortem shelf life was shown for gilthead sea bream and common carp; neither sensory-perceived nor chemical freshness showed diet-related differences. Rainbow trout fed with the plant-based diet exhibited slightly worse sensory freshness than fish fed with FM/FO-based diets, at the end of shelf life. These findings imply that FM and FO can be successfully substituted without major impacts on shelf life of fish.

Characterization of odor-active compounds in cooked meat of farmed obscure puffer (Takifugu obscurus) using gas chromatography-mass spectrometry-olfactometry

The volatile and odor-active compounds in cooked meat of farmed obscure puffer (Takifugu obscurus) were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). The volatile compounds were extracted by the simultaneous distillation-extraction (SDE) method, then separated and identified by GC-MS. Odor-active compounds in the SDE extract were characterized by GC-MS-O. A total of 68 volatile compounds were found, including 23 aldehydes, 10 alcohols, nine ketones, 17 N- or S-containing compounds and aromatics, three acids, three alkanes, and three esters. Of these, 31 odor-active compounds were detected and identified. Trimethylamine (fishy), octanal (grassy, leafy, green), (E)-2-octenal (roast, fatty), 1-octen-3-ol (fishy, fatty, mushroom, grassy), 2-ethyl-1-hexanethiol (cooked fish), (E,E)-2,4-octadienal (cooked meat, sweet), 2-acetylthiazole (meaty, roast, nutty, sulfur), 2-acetylpyrrole (nutty, walnut, bread) were identified as the key odorants in the cooked meat of farmed obscure puffer based on posterior intensity and time-intensity methods.

Effect of two experimental diets (protein and lipid vegetable oil blends) on the volatile profile of Senegalese sole (Solea senegalensis Kaup, 1858) muscle

The aim of this study was to determine differences among volatile compounds composition of Senegalese sole muscle fed with extruded diets containing different plant protein (PP) and vegetable oil (VO) sources. Two set of experiments were performed on growing sole. One growth trial used a control diet containing fish meal (FM) as the main protein source and different PP-based diets. Another growth trial compared a control diet containing fish oil (FO) as the main lipid source and different VO-based diets; after a period, all sole were fed with the FO diet. Results showed that the incorporation of PP sources up to 75% allowed the production of a similar content of major volatile compounds to the control diet. In VO-based diets, some significant differences were found in the levels of some volatile compounds in sole muscle; however, no significant differences were obtained through sensory evaluation.

The effect of a flaxseed oil-enhanced diet on the product quality of farmed brook trout (Salvelinus fontinalis) fillets

The effects of dietary modification with flaxseed oil-enhanced (Flax) feed on the product quality of brook trout fillets were examined. Trout were fed a commercial feed supplemented with fish oil (CD) or flaxseed oil (Flax) for 165 d before harvesting. Proximate composition and fatty acid profile were determined on fillets. Quality parameters of the raw fillets were examined over the storage period by measuring color (L*, a*, b*), muscle pH, and thiobarbituric acid reactive substances test. Evaluations on the cooked fillets included sensory evaluation with triangle tests and a paired preference test. There were no differences in proximate composition between the groups; however, the total omega-3 fatty acids were greater in Flax fillets (P<0.05). Diet and day were shown to interact in their effect on whiteness, pH, and lipid oxidation (P<0.05); however, linear regression did not determine that malondialdehyde concentration was associated with time in either diet type implying that lipid oxidation in the vacuum-packed fish was controlled at storage temperatures (4°C). Sensory panelists were able to choose the odd sample in a replicated triangle test analyzed using the β-binomial model, and there was preference for Flax fillets (P<0.05). Results indicate that a Flax-enhanced diet would have favorable effects on product quality of farmed brook trout.

Review. Sulfur-containing volatile compounds in seafood: occurrence, odorant properties and mechanisms of formation

An inventory of the most part of sulfur-containing volatile compounds (SCVCs) present in seafood was carried out. These molecules constitute key compounds to understand and improve seafood quality. According to their nature, concentration and environmental parameters (temperature), they can move the overall seafood odor from desirable to rotten. Sulfury odors can also indicate problems in sanitary quality. Thus, it is essential to monitor the generation of these compounds to better control the organoleptic and sanitary quality of seafood. SCVC were divided in two categories: aliphatic compounds and cyclic compounds. Among cyclic SCVC, several families of compounds can be distinguished as thiophenes, thiazoles and their respective derivatives. The main pathways of formation of SCVC in seafood are investigated in order to better understand their presence in seafood aroma. Microbial mediated enzymatic reactions are mainly implied in the generation of aliphatic SCVC whereas Maillard reactions are involved in the generation of cyclic SCVC. A small part of SCVC could also derive from the environment by direct bioaccumulation of S-containing molecules or precursors. Then, the occurrence of SCVC in seafood is discussed according to the extraction methods, analysis methods - sometimes olfactometric methods and the species - the state and the average biochemical composition of the seafood matrix in which they were recovered. Finally, among the identified SCVC, the odorant properties of odor-active volatile compounds were investigated. Aromatic notes and odorant thresholds for odorant SCVC of seafood aroma are listed. Both pathways of formation and lists of SCVC linked to their odorant properties constitute important indicators to optimise seafood quality from an organoleptic and sanitary point of view.

Quality Changes of Marinated Tench (Tinca tinca) during Refrigerated Storage

The quality control of marinated tench with sauce stored at 4 °C was investigated in terms of sensory, chemical (total volatile basic nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric values (TBA), peroxide value, free fatty acids, biogenic amines, fatty acids, and pH and microbiological parameters (total aerobic count, coliform, Escherichia coli, and Salmonella) during 6 months of storage. The use of alcohol vinegar and salt in marinated tench caused the TVB-N, TMA to decrease. The maximum TVB-N and TMA values were found to be 12.77 mg/100 g and 4.68 mg/100 g after 150 days and 180 days storage period, respectively. Oxidative rancidity in marinated tench was found to be low (2.81 mg MA/kg) and rancid flavor was not detected even after a storage period of 180 days. As storage time progressed, putrescine, cadaverine, and serotonine became the dominant amines. Salmonella, coliform, E. coli, and Staphylococcus aureus were not detected during the storage period of 6 months. Total bacteria count increased to 4.3 log CFU/g at the end of the storage period. Data obtained from this study showed that marinated tench can be stored for more than 6 months.

Effects of starvation and water quality on the purging process of farmed Murray cod (Maccullochella peelii peelii)

The aim of this study was to determine the effects of starvation and water quality during the purging process on the biometric parameters, fatty acids, and flavor volatiles of Murray cod farmed in a recirculation system. Market size Murray cod, at the end of the grow-out stage, were divided into eight treatments. The treatments were either fed/starved (F or S) and kept in clean water (CW: CWF2, CWS2, CWF4, and CWS4) or fed/starved and kept in recycled water (RW: RWF2, RWS2, RWF4, and RWS4) for either 2 or 4 weeks. Fish were sampled at 0, 2, and 4 week intervals. Food deprivation was responsible for a significant (P < 0.05) weight loss compared to that of fed treatments. The same was observed for the condition factor (K), hepatosomatic index (HSI), and dress-out percentage (DP). No significant changes were, however, observed in the visceral fat index (VFI). Saturated fatty acids (SFA) were highest in RWF4 and lowest in CWS4 (P < 0.05), while monounsaturated fatty acids (MUFA) were lowest in CWF4 (P < 0.05). Starvation did not affect the flavor volatile compounds, which were mainly affected by changes in water quality. Specifically, total aldehyde (% w/w) content was significantly (P < 0.05) affected by water quality, but the time of purging was not responsible for any noteworthy differences. This study was able to separate the effects of starvation and water quality, in the purging process, on the final eating quality of farmed market size Murray cod. It is concluded that because of the inevitable weight loss during starvation, Murray cod should be fed during the purging stage but kept in clean water and deprived of food only for the time necessary to empty the gastro-intestinal tract.