Analysis of Volatile Flavor Compounds of Sardine (Sardinops melanostica) by Solid Phase Microextraction

Creating alternative seafood flavour from non-animal ingredients: A review of key flavour molecules relevant to seafood

This review summarises current knowledge of the molecular basis for flavour profiles of popular seafood types (crustacean (crab, lobster, prawn, etc.), mollusc (oyster, squid, etc.), oily fish (salmon, sardine, etc.) and white fish (barramundi, turbot, etc.)), and provides a foundation for formulating improved plant-based seafood alternative (PBSA) flavours. Key odour-active volatile molecules were identified from a systematic review of published olfactometry studies and taste-active compounds and macronutrient profiles of different seafood species and commercial PBSAs from nutrition databases were compared. Ingredients commonly used in commercial BPSAs and new potential sources of flavouring agents are evaluated. While significant challenges in replicating seafood flavour and texture remain, this review provides some insights into how plant-based ingredients could be applied to improve the acceptability of PBSAs.

Changes in the Quality and Microflora of Yellowtail Seriola quinqueradiata Muscles during Cold Storage

We evaluated the changes in the quality and microflora of yellowtail flesh cold-stored until spoilage. Based on the sensory evaluation, odor palatability was deemed unacceptable for dark muscle (DM) and the dorsal part of the ordinary muscle (OD) after >10 days and 14 of storage, respectively. Log 7 CFU/g in DM as well as OD was obtained on days 10 (Aeromonas spp.) and 14 (Enterobacteriaceae and Pseudomonas spp.) of storage, whereas log 5 (Brocothrix thermosphacta) and 6 (H2S-producing bacteria) CFU/g in them were obtained on day 14 of storage. In these bacteria, the viable bacterial counts of Pseudomonas spp. and Aeromonas spp. in DM were significantly higher than those in OD only at some storage times. Amplicon sequencing revealed that in both muscles, Pseudomonas became predominant after storage, with greater than 90% recorded after more than 10 days of storage. The relative abundances of Acinetobacter, Unclassified Gammaproteobacter, and Shewanella were relatively high in both muscles after more than 10 days of storage; however, these values were less than 5%. Ethyl butyrate in the OD and DM and 2,3-butanedione in the OD were first detected on days 14 and 10 of storage, respectively. Acetoin in the OD increased by 81-fold after 14 days of storage and was significantly increased in the DM after more than 10 days compared with the amount detected pre-storage. Volatiles, such as (E)-2-pentenal in the OD and 1-pentanol in the DM, decreased and increased linearly, respectively, throughout the 14-day storage period. Altogether, these volatile components may cause quality deterioration due to spoilage and/or lipid oxidation during cold storage of the OD and DM.

Recovery of Valuable Aromas from Sardine Cooking Wastewaters by Pervaporation with Fractionated Condensation: Matrix Effect and Model Validation

Due to the lack of studies addressing the influence of real food matrices on integrated organophilic pervaporation/fractionated condensation processes, the present work analyses the impact of the real matrix of sardine cooking wastewaters on the fractionation of aromas. In a previous study, a thermodynamic/material balance model was developed to describe the integrated pervaporation-a fractionated condensation process of aroma recovery from model solutions that emulate seafood industry aqueous effluents, aiming to define the best conditions for off-flavour removal. This work assesses whether the previously developed mathematical model, validated only with model solutions, is also applicable in predicting the fractionation of aromas of different chemical families from real effluents (sardine cooking wastewaters), aiming for off-flavour removals. It was found that the food matrix does not influence substantial detrimental consequences on the model simulations, which validates and extends the applicability of the model.

Rapid Production of Fish Sauce from the Internal Organs of White Sturgeon, Acipenser transmontanus Richardson, 1836

The internal organs of white sturgeon in Miyazaki Prefecture are discarded during processing. Therefore, we tried to produce fish sauce using a short-term manufacturing method. The minced internal organs were autolyzed by endogenous proteases at 50 °C. During autolysis, the protein contents of the supernatant and precipitate after centrifugation were analyzed by the Kjeldahl method, and the protein size was monitored by SDS-PAGE. This analysis showed that the extraction rate was about 60% after treatment at 50 °C for 24 h. The major bands at 200 kDa, 43 kDa, and 40 kDa detected before the start of the treatment gradually disappeared over time. Fifteen components were detected as the main volatile components. These components increased sharply and then decreased during incubation at 50 °C for 24 h. The fish sauce produced had a good aroma after incubation at 50 °C for 72 h.

Clean Technologies for Production of Valuable Fractions from Sardine Cooking Wastewaters: An Integrated Process of Flocculation and Reverse Osmosis

The increase in environmental consciousness and stricter regulations has motivated industries to seek sustainable technologies that allow valorising wastewaters, contributing to the profitability of overall processes. Canning industry effluents, namely sardine cooking wastewater, have a high organic matter load, containing proteins and lipids. Their untreated discharge has a negative environmental impact and an economic cost. This work aims to design an integrated process that creates value with the costly sardine cooking wastewater effluent. The research strategy followed evaluates coagulation/flocculation technologies as pre-treatment of the sardine cooking wastewater followed by reverse osmosis. Two different added-value products were obtained: a solid fraction rich in proteins, lipids (above 20%), and aromas that might be used for feed/pet/aquaculture applications and, from the processing of the resultant aqueous stream by reverse osmosis, a natural flavouring additive, which can be applied in food/feed. Additionally, the permeate from reverse osmosis presents a much lower organic load than the original raw material, which may be reused in the overall process (e.g., as water for washings) or discharged at a lower cost, with environmental benefits and economic savings.

Metabolomic Effects of the Dietary Inclusion of Hermetia illucens Larva Meal in Tilapia

Black soldier fly (Hermetia illucens) larvae meal have been used as feed protein supplements in fish feed, but few researches have investigated the metabolomic effects of Hermetia illucens larvae meal supplements. Therefore, the metabolic effects on Nile tilapia were investigated by replacing 5%, 10%, and 20% of the dietary soybean meal in the basal diet with Hermetia illucens larvae meal, respectively. This study shows that 20% H. illucens larvae meal feed could promote tilapia average daily gain of upto 5.03 ± 0.18 g (mean ± SEM). It was found that the tricarboxylic acid cycle efficiency was improved by activating the enzymes of mitochondrial isocitrate dehydrogenase, NAD-malate dehydrogenase, succinate dehydrogenase, pyruvate dehydrogenase, and α-ketoglutarate dehydrogenase, which then increased the output of ATP and NADH. Furthermore, amino acid and protein biosynthesis was boosted by enhanced glutamine synthetase and glutamate synthase. In particular, GSH increased with increased H. illucens larvae meal. Unsaturated fatty acid biosynthesis was stimulated by higher levels of fatty acid synthase and acetyl CoA carboxylase. Additionally, there was no significant change in lipase levels. Thus, the higher acetyl Co-A content was primarily involved in fatty acid biosynthesis and energy metabolism. Flavor substances, such as nonanal and 2-methyl-3-furanthiol, also accumulated with the addition of H. illucens larvae meal, which increased the umami taste and meat flavor. Additionally, the flavor of tilapia was improved owing to a decrease in trimethylamine content, which causes an earthy and fishy taste. This study uncovers a previously unknown metabolic effect of dietary H. illucens larvae meal on Nile tilapia.

Differences in flavor characteristics of frozen surimi products reheated by microwave, water boiling, steaming, and frying

This study investigated the effects of different reheating methods (microwave, water boiling, steaming, and frying) on the flavor of surimi gels with untreated sample as control. Electronic nose and electronic tongue results showed that microwave could better maintain the original odor and taste characteristics of surimi gels. Additionally, 43 kinds of volatile aroma compounds were detected in surimi gels, including aldehydes, alcohols, ketones, heterocycles, and esters. The aroma fingerprints of surimi gels were similar between water boiling and steaming and between microwave and the control, whereas frying showed the most unique aroma profile possibly related to the highest TBARS values. The total contents of nucleotides, carnosine and lactic acid were significantly higher in fried samples relative to other samples. In conclusion, all the reheating treatments can alter the flavor of samples, but microwave showed better performance in sensory evaluation and maintaining the original flavor of surimi gels.

Deodorizing effects of rosemary extract on silver carp (Hypophthalmichthys molitrix) and determination of its deodorizing components

Fishy odor in fish products severely influences both eating quality and commercial acceptability, and natural plant extracts, particularly spices, have recently become popular for the removal of fishy odor. This study aimed to explore the potential of rosemary extract for the deodorization of silver carp (Hypophthalmichthys molitrix), as well as to identify the deodorizing components in rosemary extract. Results showed that all of the spice extracts used in this study (ginger, garlic, angelica dahurica, fennel, rosemary, nutmeg, white cardamom, cinnamon, star anise, and bay leaf) significantly reduced the fishy odor value of silver carp, among which rosemary extract was most effective, decreasing the fishy odor value by about 58%. Gas chromatography-mass spectrometry analysis and sensory evaluation showed that the fishy odor value and concentrations of the fishy odor-active compounds were significantly reduced by the application of rosemary extract. However, the lower the total phenolic content of rosemary extract, the poorer the deodorizing effects against silver carp, suggesting that the deodorizing effect was primarily driven by polyphenols. Fourteen phenolic compounds were measured in rosemary extract, and three individual phenolic compounds (rosmarinic acid [RA], carnosic acid [CA], and carnosol [CS]) were chosen for deodorizing experiment. Sensory detection results and changes of contents of volatile showed that these three phenolic compounds are effective at removing the fishy odor. These results suggest that polyphenols are the main deodorizing components, and RA, CA, and CS are the main deodorizing active compounds in rosemary extract. PRACTICAL APPLICATION: The results of this study may provide a new way to determine the deodorizing components of spice extracts. Moreover, it can provide guidance for further research in investigating the deodorizing mechanism of sipce extracts.

New insights into the flavoring potential of cricket (Acheta domesticus) and mealworm (Tenebrio molitor) protein hydrolysates and their Maillard products

Insect proteins have an earthy-like flavor and have not shown great flavor potential for food applications so far. In this study, insect proteins of cricket Acheta domesticus and mealworm Tenebrio molitor larvae were first enzymatically hydrolyzed using two peptidase preparations (Flavourzyme1000L and ProteaseA "Amano"2SD). Xylose was then added to facilitate Maillard reactions (30 min, T = 98 °C, 1% (w/v) xylose). A comprehensive sensory evaluation showed that both the hydrolysis and the Maillard reactions changed the flavor description of the samples significantly to more complex and savory-like taste profiles (27 descriptors for cricket and 39 descriptors for mealworm protein). In addition, 38 odor-active molecules were identified using gas chromatography-olfactometry (1 alcohol, 5 acids, 11 aldehydes, 5 ketones and 16 heterocyclic compounds). The results showed impressively that the flavoring potential of insect proteins was significantly enhanced with respective processing.

Removal of the fishy malodor from Bangia fusco-purpurea via fermentation of Saccharomyces cerevisiae, Acetobacter pasteurianus, and Lactobacillus plantarum

The present study aims to evaluate the deodorization of Bangia fusco-purpurea using microorganism fermentation with commercial starter cultures of Saccharomyces cerevisiae, Acetobacter pasteurianus, and Lactobacillus plantarum. The results showed the fermentation with S. cerevisiae, A. pasteurianus, and L. plantarum resulted in significantly decreases (p < .05) of the fishy malodor in B. fusco-purpurea. Among the three strains, S. cerevisiae was the best for reducing the fishy malodor. The optimal inoculum size and fermentation time were 0.2% and 4 hr, respectively. After the fermentation with the S. cerevisiae, the content of 1-octen-3-ol, (E)-2-octen-1-ol, hexanal, non-(2E)-enal, (E,E)-2,4-decadienal, 3,5-octadien-2-one, and 2-pentyl-furan were hard to be detected in the seaweed, whereas increases were observed in the concentrations of 2-butyl-1-octanol, cedrol, diisobutyl phthalate, and 2,4-di-t-butylphenol. The odor active value analysis indicated the removal of fishy odor was related to the reduction, dehydrogenation, and deformylating oxygenation of hexanal, nonanal, non-(2E)-enal, and (E,E)-2,4-decadienal and esterification of 1-octen-3-ol and (E)-2-octen-1-ol. Our findings provide a technical and scientific basis for the removal of fishy odor from B. fusco-purpurea. PRACTICAL APPLICATIONS: Bangia fusco-purpurea is a seaweed that can reduce the risks of cardiovascular and chronic metabolic diseases in human body. However, the seaweed has a strong fishy malodor, which largely declines consumer's acceptance. In this study, the commercial starters of Saccharomyces cerevisiae, Acetobacter pasteurianus, and Lactobacillus plantarum were shown to reduce the fishy malodor in B. fusco-purpurea via fermentation. After the fermentation with the microorganisms especially with the S. cerevisiae, the fishy malodor significantly reduced, and the overall aroma acceptance of B. fusco-purpurea products greatly improved. Therefore, this study provides a technical basis for the removal of fishy odor from B. fusco-purpurea and processing value-added products from it and facilitating its health benefits for human.

Formation and conversion of characteristic volatile compounds in grilled eel (Astroconger myriaster) during different processing steps

The aroma of grilled eel is affected by three key processing steps: curing, steaming, and grilling.

Fresh and grilled eel volatile fingerprinting by e-Nose, GC-O, GC-MS and GC × GC-QTOF combined with purge and trap and solvent-assisted flavor evaporation

Fresh and grilled eel were investigated with respect to their volatile compounds and different fingerprinting techniques. An electronic nose (e-Nose) was applied to distinguish the odor between fresh and grilled eels. Purge and trap (P&T) and solvent-assisted flavor evaporation (SAFE) method were used to extract volatile compounds and further analyzed by a gas chromatographic combined with quadrupole mass spectrometry (GC-MS) and a two-dimensional gas chromatographic combined with hybrid quadrupole time-of-flight mass spectrometry (GC × GC-QTOF). SAFE extracted more ketone, alcohol and high boiling volatiles in eels than P&T. Considering some distinct compounds extracted by P&T, a P&T and SAFE combined method was chosen. There were 155 volatiles detected in fresh and grilled eels, 93 volatiles were identified. Due to the higher peak capacity, GC × GC-QTOF detected 39 compounds more than GC-MS. The key characteristic volatiles of grilled eel were methyl propyl disulfide, dimethyl trisulfide, heptane, octane, and camphene. Volatile fingerprinting can be a reference benchmark for identification and quality appraisal of fresh and grilled eel products.

The effect of microwave on the interaction of flavour compounds with G-actin from grass carp (Catenopharyngodon idella)

BACKGROUND

In order to investigate the influence of non-thermal effects of microwaves on the flavour of fish and meat products, the G-actin of grass carp in ice baths was exposed to different microwave powers (0, 100, 300 or 500 W); the surface hydrophobicity, sulfhydryl contents, secondary structures and adsorption capacity of G-actin to ketones were determined.

RESULTS

As microwave power increased from 0 to 300 W, the surface hydrophobicity, total and reactive sulfhydryls increased; α-helix, β-sheet and random coil fractions turned into β-turn fractions. As microwave power increased from 300 to 500 W, however, hydrophobicity and sulfhydryl contents decreased; β-turn and random coil fractions turned into α-helix and β-sheet fractions. The tendencies of adsorbed capacity of ketones were similar to hydrophobicity and sulfhydryl contents.

CONCLUSION

The increased adsorbing of ketones could be attributed to the unfolding of secondary structures by revealing new binding sites, including thiol groups and hydrophobic binding sites. The decreased binding capacity was related to the refolding and aggregation of protein. The results suggested that microwave powers had obvious effects on the flavour retention and proteins structures in muscle foods. © 2017 Society of Chemical Industry.

Characterisation of aroma-active and off-odour compounds in German rainbow trout (Oncorhynchus mykiss). Part I: Case of aquaculture water from earthen-ponds farming

Comprehensive analyses were accomplished to explore the odorous molecules responsible for off-odour development in earthen-ponds rainbow trout (Oncorhynchus mykiss) aquaculture farming in Germany. In this part of the study, water odorants were extracted using solvent-assisted flavour evaporation (SAFE); then, extracts were analysed by one- and two- dimensional high resolution gas chromatography coupled with olfactometry and mass spectrometry using two columns with different polarity (DB-FFAP and DB-5). Aroma extract dilution analysis (AEDA) of the solvent extract samples revealed 54 odorants, and 47 of them were identified. In this study, a series of compounds is described for the first time in German earthen-ponds rainbow trout aquaculture water including, amongst others, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (furaneol), vanillin, (E)-4,5-epoxy-(E)-2-decenal, 4-ethyloctanoic acid, 3-methylindole (skatole), 5α-androst-16-en-3-one (androstenone), and 2-(2-butoxyethoxy) ethanol. Moreover, the sensory experiment indicated that (E)-4,5-epoxy-(E)-2-decenal, (E,E)-2,4-octadienal, and 1-octen-3-one are the main contributors to the metallic, cucumber, and mushroom notes of the samples.

Reactivity and stability of selected flavor compounds

Flavor is the most important aspect of food. Based on the complex matrix of the food system and the flavor structure themselves, one important factor that plays a key role in the quality attribute of food is flavor stability. Not surprisingly, there is a large volume of published research investigating the stability of different food flavor compounds, since understanding flavor stability is crucial to creating greater awareness of dietary flavor application. This review presents a variety of factors that are thought to be involved in the stability of several selected important flavor compounds and the approach to improve the stability of different flavors. Some mechanisms of chemical degradation of flavor compounds were also provided.

Detection of flavor compounds in longissimus muscle from four hybrid pig breeds of Sus scrofa, Bamei pig, and Large White

To detect the flavor quality and flavor compounds in raw longissimus muscle from four typical pig breeds: Sus scrofa × Bamei pig named F1 (group A), F1 × F1 (group B), F1 × Bamei pig (group C), and F1 × Large White (group D). The chemical compositions of longissimus muscles from four breeds were examined using headspace solid-phase microextraction/gas chromatography mass spectrometry method. Distinct differences for the same flavor compounds of longissimus muscles between different breeds were analyzed. Totally 64 flavor compounds shared in four groups, and 10 flavor compounds with significant difference among four groups (p &lt; 0.05), including allyl butyrate, (Z)-2-penten-1-ol, 2,2-dimethyl-3-methyl oxirane, 2-pentylfuran, dodecane, 2,4-decadienal, vinylsilane, 3-methyl-1-butanol, (1-methyldecyl)-benzene, and dipropyl phthalate. Totally, 23–41 flavor compounds did not commonly exist in four groups, such as only as dibutyl isophthalate in group A; 6,10-dimethyl-5-9-undecadien-2 one, bis (2-trimethylsilyl) ethyl ester-malonic acid, heptadecane, 2,4,6-trimethyl pyridine, and diisooctyl adipate in group C alone; and 1,3-dimethylcyclopentanol, 2-octanone, and trimethylsilane in group D alone. While, no specific flavor compounds were identified in group B. All these flavor compounds covered 12 types of hydrocarbons, alcohols, aldehydes, hydroxybenzenes, acids, ketones, esters, sulfides, furans, alkenes, and pyrrole. Besides, we analyzed 14 flavor compounds with different flavors combining with previous studies. The flavor compounds in longissimus muscles might be closely related to the breeds, and the hybrid of S. scrofa × Bamei pig had the most flavor compounds in raw longissimus muscle.

Fortification of foods with omega-3 polyunsaturated fatty acids

A $600 million nutritional supplements market growing at 30% every year attests to consumer awareness of, and interests in, health benefits attributed to these supplements. For over 80 years the importance of polyunsaturated fatty acid (PUFA) consumption for human health has been established. The FDA recently approved the use of ω-3 PUFAs in supplements. Additionally, the market for ω-3 PUFA ingredients grew by 24.3% last year, which affirms their popularity and public awareness of their benefits. PUFAs are essential for normal human growth; however, only minor quantities of the beneficial ω-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are synthesized by human metabolism. Rather PUFAs are obtained via dietary or nutritional supplementation and modified into other beneficial metabolites. A vast literature base is available on the health benefits and biological roles of ω-3 PUFAs and their metabolism; however, information on their dietary sources and palatability of foods incorporated with ω-3 PUFAs is limited. DHA and EPA are added to many foods that are commercially available, such as infant and pet formulae, and they are also supplemented in animal feed to incorporate them in consumer dairy, meat, and poultry products. The chief sources of EPA and DHA are fish oils or purified preparations from microalgae, which when added to foods, impart a fishy flavor that is considered unacceptable. This fishy flavor is completely eliminated by extensively purifying preparations of n-3 PUFA sources. While n-3 PUFA lipid autoxidation is considered the main cause of fishy flavor, the individual oxidation products identified thus far, such as unsaturated carbonyls, do not appear to contribute to fishy flavor or odor. Alternatively, various compound classes such as free fatty acids and volatile sulfur compounds are known to impart fishy flavor to foods. Identification of the causative compounds to reduce and eventually eliminate fishy flavor is important for consumer acceptance of PUFA-fortified foods.

Characterization of the key aroma compounds in Turkish olive oils from different geographic origins by application of aroma extract dilution analysis (AEDA)

The aroma and aroma-active compounds of olive oils obtained from Nizip Yaglik (NY) and Kilis Yaglik (KY) cultivars and the effect of the geographical area (southern Anatolian and Aegean regions) on these compounds were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). For this purpose, two oil samples were obtained from their native geographical area including NY from Nizip province and KY from Kilis province (southern Anatolian region of Turkey). Another two oils of the same cultivar, NY-Bornova (NY-B) and KY-Bornova (KY-B), were obtained from the Olive Oil Research Center-Bornova, Izmir province (Aegean region of Turkey) to compare geographical effect on aroma and aroma-active compounds. Simultaneous distillation and extraction (SDE) with dichloromethane was used for extraction of volatile components. SDE gave a highly representative aromatic extract of the studied olive oil based on the sensory analysis. Totals of 61, 48, 59, and 48 aroma compounds were identified and quantified in olive oils obtained from NY, NY-B, KY, and KY-B cultivars, respectively. The results of principal component analysis (PCA) showed that the aroma profile of native region oils was discriminately different from those of Bornova region oils. Aldehydes and alcohols were qualitatively and quantitatively the most dominant volatiles in the oil samples. Aroma extract dilution analysis (AEDA) was used for the determination of aroma-active compounds of olive oils. The number of aroma-active compounds in native region oils was higher than in Bornova region oils. Within the compounds, aldehydes and alcohols were the largest aroma-active compounds in all olive oils.

Isolation, expression, and characterization of a hydroperoxide lyase gene from cucumber

A full-length cDNA coding for hydroperoxide lyase (CsHPL) was isolated from cucumber fruits of No. 26 (Southern China type) and No.14-1 (Northern China type), which differed significantly in fruit flavor. The deduced amino acid sequences of CsHPL from both lines show the same and significant similarity to known plant HPLs and contain typical conserved domains of HPLs. The recombinant CsHPL was confirmed to have 9/13-HPL enzymatic activity. Gene expression levels of CsHPL were measured in different organs, especially in fruits of different development stages of both lines. The HPL activities of fruit were identified basing on the catalytic action of crude enzyme extracts incubating with 13-HPOD (13-hydroperoxy-(9Z,12E)-octadecadienoic acid) and 13-HPOD + 9-HPOD (9-hydroperoxy-(10E,12Z)-octadecadienoic acid), and volatile reaction products were analyzed by GC-MS (gas chromatography-mass spectrometry). CsHPL gene expression in No. 26 fruit occurred earlier than that of total HPL enzyme activity and 13-HPL enzyme activity, and that in No. 14-1 fruit was consistent with total HPL enzyme activity and 9-HPL enzyme activity. 13-HPL enzyme activities decreased significantly and the 9-HPL enzyme activities increased significantly with fruit ripening in both lines, which accounted for the higher content of C6 aldehydes at 0–6 day post-anthesis (dpa) and higher content of C9 aldehydes at 9–12 dpa.

Respiratory and olfactory cytotoxicity of inhaled 2,3-pentanedione in Sprague-Dawley rats

Flavorings-related lung disease is a potentially disabling disease of food industry workers associated with exposure to the α-diketone butter flavoring, diacetyl (2,3-butanedione). To investigate the hypothesis that another α-diketone flavoring, 2,3-pentanedione, would cause airway damage, rats that inhaled air, 2,3-pentanedione (112, 241, 318, or 354 ppm), or diacetyl (240 ppm) for 6 hours were sacrificed the following day. Rats inhaling 2,3-pentanedione developed necrotizing rhinitis, tracheitis, and bronchitis comparable to diacetyl-induced injury. To investigate delayed toxicity, additional rats inhaled 318 (range, 317.9-318.9) ppm 2,3-pentanedione for 6 hours and were sacrificed 0 to 2, 12 to 14, or 18 to 20 hours after exposure. Respiratory epithelial injury in the upper nose involved both apoptosis and necrosis, which progressed through 12 to 14 hours after exposure. Olfactory neuroepithelial injury included loss of olfactory neurons that showed reduced expression of the 2,3-pentanedione-metabolizing enzyme, dicarbonyl/L-xylulose reductase, relative to sustentacular cells. Caspase 3 activation occasionally involved olfactory nerve bundles that synapse in the olfactory bulb (OB). An additional group of rats inhaling 270 ppm 2,3-pentanedione for 6 hours 41 minutes showed increased expression of IL-6 and nitric oxide synthase-2 and decreased expression of vascular endothelial growth factor A in the OB, striatum, hippocampus, and cerebellum using real-time PCR. Claudin-1 expression increased in the OB and striatum. We conclude that 2,3-pentanedione is a respiratory hazard that can also alter gene expression in the brain.

Change of volatile compounds in fresh fish meat during ice storage

The change of volatile compounds in fresh fish meat during 3- to 4-d ice storage was investigated for several fishes using an electronic nose system and a gas chromatography-mass spectrometer (GC/MS) with headspace solid-phase micro-extraction (SPME). Principal component analyses for samples using the electronic nose system revealed that the increase of some volatile compounds during storage was rapid in sardine (Sardinops melanostictus), jack mackerel (Trachurus japonicus), and chub mackerel (Scomber japonicus); moderate in yellowtail (Seriola quinqueradiata), skipjack (Katsuwonus pelamis), and young oriental bluefin tuna (Thunnus thynnus). In contrast to these fishes, the change was little in "white meat" fishes such as red seabream (Chrysophrys major), Japanese seabass (Lateolabrax japonicus), flatfish (Paralichthys olivaceus), puffer (Lagocephalus wheeleri), and bartail flathead (Platycephalus indicus). SPME-GC/MS analysis showed that some aldehydes and alcohols such as 1-heptanol, (E)-2-octenal, (E)-2-hexenal, 1-pentanol, (E,E)-2,4-heptadienal,2,4-hexadienal, 1-hexanol, 4-heptenal, and so forth increased rapidly in jack mackerel and chub mackerel, slowly in skipjack, and a little in red seabream and puffer during the storage. The increase of these compounds was considered to have an effect on the change of electronic nose response. Hexanal was a dominant compound increased from the beginning of the storage in jack mackerel. The increase of volatile compounds was little in red seabream and puffer. The increase of these aldehydes and alcohols was thought to be an appropriate marker for monitoring the freshness of "fresh" fish except for white meat fish.

PRACTICAL APPLICATION

The results of this study are ready to apply for preventing fishy off-flavor of fisheries products. Lipid oxidative derivatives other than trimethylamine contributed to fresh fish flavor; therefore, to prevent lipid oxidation seemed important.

Characterization of the key aroma compounds in cooked grey mullet (Mugil cephalus) by application of aroma extract dilution analysis

Aroma and aroma-active compounds of wild grey mullet ( Mugil cephalus ) were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). According to sensory analysis, the aromatic extract obtained by simultaneous distillation and extraction (SDE) was representative of grey mullet odor. A total of 50 aroma compounds were identified and quantified in grey mullet. Aldehydes were qualitatively and quantitatively the most dominant volatiles in grey mullet. Aroma extract dilution analysis (AEDA) was used for the determination of aroma-active compounds of fish sample. A total of 29 aroma-active compounds were detected in aromatic extract of grey mullet, of which 24 were identified. On the basis of the flavor dilution (FD) factor, the most powerful aroma active compounds identified in the extract were (Z)-4-heptenal and nonanal, which were described as the strong cooked fish and green-fruity odor, respectively.

Oxidative stability of microencapsulated fish oil powders stabilized by blends of chitosan, modified starch, and glucose

Various indices of lipid oxidation were used to assess the oxidative stability of microencapsulated fish oil powders prepared from tuna oil-in-water emulsions (pH 4.9 or 6.0) containing chitosan, an emulsifying starch, and glucose. There were good agreements among the induction period for oxidation under accelerated conditions (80 degrees C, 5 bar oxygen), the development of oxidation volatile markers from fish oil (namely, propanal, 1-penten-3-ol, 1-penten-3-one, 2,4-(Z,E)-heptadienal, and 2,4-(E,E)-heptadienal), and the loss of eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) over four weeks of storage at 25 degrees C. All indices of oxidation showed that powders prepared from emulsions at pH 6.0 were more stable to oxidation than corresponding formulations at pH 4.9. It is suggested that the increased electrostatic interactions between the chitosan and emulsifying starch at the higher pH contributed to the increased stability of the microcapsule powders.

Effects of sulfur dioxide on formation of fishy off-odor and undesirable taste in wine consumed with seafood

In order to evaluate sensory compatibility of alcoholic beverages with food, beverages and dried squid, namely, "surume", a common Japanese accompaniment, were consumed together. White wine and dried squid pairings had a more undesirable taste and more fishy off-odor than sake and dried squid pairings. The undesirable taste and fishy off-odor appeared to be caused by degradation of unsaturated fatty acids (e.g., docosahexaenoic acid (DHA)), which are found in fish and squid. Upon addition of DHA to the beverage, bitterness intensity, measured by instrumental taste sensor analysis, and the concentration of certain aldehydes reported to contribute to fishy flavors, increased in white wines, whereas they remained largely the same in sake. Among the major chemical constituents that distinguish wine from sake, only wine-specific sulfite markedly increased bitterness intensity and aldehyde levels upon addition of DHA. These results suggest that sulfur dioxide in wine participated in degradation of unsaturated fatty acids, causing an increase in undesirable taste and fishy off-odor in wine and seafood pairings.