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Research background. Among legumes, peas are characterised by their high protein content, low glycaemic index and exceptional versatility. However, their potential as a food is often compromised by their undesirable off-flavour and taste. Hence, this study focuses on minimising off-flavours through simple pretreatments with the aim of improving the potential for the production of pea milk analogues. Pea milk analogues are a burgeoning type of plant-based milk alternatives in the growing plant-based market. Experimental approach. Pea seeds were subjected to different pretreatments: (i) dry milling, (ii) blanching followed by soaking in alkaline solution and subsequent dehulling and (iii) vacuum. Typical physicochemical properties such as pH, viscosity, colour, titratable acidity and yield were measured to obtain a brief overview of the products. Consumer acceptance test, descriptive sensory analysis, gas chromatography-mass spectrometry and gas chromatography-olfactometry were used to map the complete sensory profile and appeal of the pea milk substitutes. Results and conclusions. The L* values of the pea milk analogues were significantly lower than those of cow’s milk, while a*, b*, viscosity and pH were similar. In the descriptive sensory analysis, sweet, astringent, pea-like, cooked, hay-like, boiled corn and green notes received relatively higher scores. The vacuum-treated pea milk analogues received higher scores for flavour and overall acceptability in the consumer acceptance test. The pretreatments resulted in significant changes in the volatile profiles of the pea milk analogues. Some volatiles typically associated with off-flavour, such as hexanal, were found in higher concentrations in blanched pea milk analogues. Among the applied pretreatments, vacuum proved to be the most effective method to reduce the content of volatile off-flavour compounds. Novelty and scientific contribution. This study stands out as a rare investigation to characterise pea milk analogues and to evaluate the impact of simple pretreatments on the improvement of their sensory properties. The results of this study could contribute to the development of milk alternatives that offer both high nutritional value and strong appeal to consumers. [ABSTRACT FROM AUTHOR]

Research background. Among legumes, peas are characterised by their high protein content, low glycaemic index and exceptional versatility. However, their potential as a food is often compromised by their undesirable off-flavour and taste. Hence, this study focuses on minimising off-flavours through simple pretreatments with the aim of improving the potential for the production of pea milk analogues. Pea milk analogues are a burgeoning type of plant-based milk alternatives in the growing plant-based market. Experimental approach. Pea seeds were subjected to different pretreatments: (i) dry milling, (ii) blanching followed by soaking in alkaline solution and subsequent dehulling and (iii) vacuum. Typical physicochemical properties such as pH, viscosity, colour, titratable acidity and yield were measured to obtain a brief overview of the products. Consumer acceptance test, descriptive sensory analysis, gas chromatography-mass spectrometry and gas chromatography-olfactometry were used to map the complete sensory profile and appeal of the pea milk substitutes. Results and conclusions. The L* values of the pea milk analogues were significantly lower than those of cow’s milk, while a*, b*, viscosity and pH were similar. In the descriptive sensory analysis, sweet, astringent, pea-like, cooked, hay-like, boiled corn and green notes received relatively higher scores. The vacuum-treated pea milk analogues received higher scores for flavour and overall acceptability in the consumer acceptance test. The pretreatments resulted in significant changes in the volatile profiles of the pea milk analogues. Some volatiles typically associated with off-flavour, such as hexanal, were found in higher concentrations in blanched pea milk analogues. Among the applied pretreatments, vacuum proved to be the most effective method to reduce the content of volatile off-flavour compounds. Novelty and scientific contribution. This study stands out as a rare investigation to characterise pea milk analogues and to evaluate the impact of simple pretreatments on the improvement of their sensory properties. The results of this study could contribute to the development of milk alternatives that offer both high nutritional value and strong appeal to consumers.

A method for the rapid identification of off-flavoured raw pork was investigated in this study as the off-flavoured raw pork often found in slaughtering and quarantine and brought the economic loss to the pork industry. The electronic nose (e-nose) was used to analyse the volatile compounds of normal and off-flavoured pork from two cuts (plum and hind legs) and principal component analysis (PCA), linear discriminant analysis (LDA) and random forest (RF) were combined to identify and classify the pork samples. It was also verified by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). The results showed that the PCA, LDA and RF models could effectively differentiate off-flavoured pork from normal pork by using e-nose detection. The test set of hind leg meat showed better classification accuracy than plum meat, which were 91% and 81% respectively. W1S, W5C, W3C, W1C and W2W were the key sensors in the e-nose detection. A total of 50 odour substances were detected by HS-GC-IMS, including 11 ketones, 10 aldehydes, 8 esters, 5 acids, 6 alcohols, 9 other substances (including sulphur and nitrogen containing substances) and 1 uncharacterised substance. Methyl acetate, 2-butanone, 2-hexanone, n-propanol, ethyl isovalerate, and 2-pentylfuran were identified as volatile markers to distinguish between normal and off-flavoured pork screened by using partial least squares discriminant analysis (PLS-DA). The results of the e-nose and HS-GC-IMS measurements were in good agreement, confirming that the e-nose technique could be used for identification and discrimination of off-flavoured raw pork, which would provide a technical reference for the rapid identification of off-flavoured raw pork.

Abstract Background The global market of plant-based milk alternatives is continually growing. Flavour and taste have a key impact on consumers’ selection of plant-based beverages. Unfortunately, natural plant milks have only limited acceptance. Their typically bean-like and grassy notes are perceived as “off-flavours” by consumers, while preferred fruity, buttery, and cheesy notes are missing. In this regard, fermentation of plant milk by lactic acid bacteria (LAB) appears to be an appealing option to improve aroma and taste. Results In this work, we systematically studied LAB fermentation of plant milk. For this purpose, we evaluated 15 food-approved LAB strains to ferment 4 different plant milks: oat milk (representing cereal-based milk), sunflower seed milk (representing seed-based milk), and pea and faba milk (representing legume-based milk). Using GC‒MS analysis, flavour changes during anaerobic fermentations were studied in detail. These revealed species-related and plant milk-related differences and highlighted several well-performing strains delivered a range of beneficial flavour changes. A developed data model estimated the impact of individual flavour compounds using sensory scores and predicted the overall flavour note of fermented and nonfermented samples. Selected sensory perception tests validated the model and allowed us to bridge compositional changes in the flavour profile with consumer response. Conclusion Specific strain-milk combinations provided quite different flavour notes. This opens further developments towards plant-based products with improved flavour, including cheesy and buttery notes, as well as other innovative products in the future. S. thermophilus emerged as a well-performing strain that delivered preferred buttery notes in all tested plant milks. The GC‒MS-based data model was found to be helpful in predicting sensory perception, and its further refinement and application promise enhanced potential to upgrade fermentation approaches to flavour-by-design strategies.

Background: The global market of plant-based milk alternatives is continually growing. Flavour and taste have a key impact on consumers' selection of plant-based beverages. Unfortunately, natural plant milks have only limited acceptance. Their typically bean-like and grassy notes are perceived as "off-flavours" by consumers, while preferred fruity, buttery, and cheesy notes are missing. In this regard, fermentation of plant milk by lactic acid bacteria (LAB) appears to be an appealing option to improve aroma and taste. Results: In this work, we systematically studied LAB fermentation of plant milk. For this purpose, we evaluated 15 food-approved LAB strains to ferment 4 different plant milks: oat milk (representing cereal-based milk), sunflower seed milk (representing seed-based milk), and pea and faba milk (representing legume-based milk). Using GC‒MS analysis, flavour changes during anaerobic fermentations were studied in detail. These revealed species-related and plant milk-related differences and highlighted several well-performing strains delivered a range of beneficial flavour changes. A developed data model estimated the impact of individual flavour compounds using sensory scores and predicted the overall flavour note of fermented and nonfermented samples. Selected sensory perception tests validated the model and allowed us to bridge compositional changes in the flavour profile with consumer response. Conclusion: Specific strain-milk combinations provided quite different flavour notes. This opens further developments towards plant-based products with improved flavour, including cheesy and buttery notes, as well as other innovative products in the future. S. thermophilus emerged as a well-performing strain that delivered preferred buttery notes in all tested plant milks. The GC‒MS-based data model was found to be helpful in predicting sensory perception, and its further refinement and application promise enhanced potential to upgrade fermentation approaches to flavour-by-design strategies. [ABSTRACT FROM AUTHOR]

The flavour of aquatic animal products is distinct from terrestrial foods, facilitating a competitive marketing advantage. However, the flavour of aquatic animals can also be highly variable. Importantly, differences are reported in the flavour of animals from aquaculture and wild‐capture systems. These differences can erode consumer acceptance of aquaculture products and reduce financial returns to producers. Mild 'fish‐like', 'marine', 'crustacean‐like', 'seafood' and 'sweet' odours are desirable. However, overt 'fish‐like', 'fatty' and 'earthy' odours are quality deficits and cause products to become unpalatable. Odorous volatile compounds are responsible for eliciting these characteristic odours. In this literature review, the odorous volatile compounds of 96 aquatic animal samples are reported, revealing 291 different compounds. Generalist compounds that are integral to the odour of aquatic animals are presented in addition to 86 compounds that elicit key characteristic odours. The influence of these compounds on aquatic animal flavour is explored and the specific factors likely to affect their manipulation in aquaculture products are discussed. The culture environment and diet are critical factors affecting volatile profiles of aquatic animals and are the variables that can be controlled by aquaculture producers. The information presented in this review can underpin the development of innovative aquaculture strategies that prevent environmental exposure of aquatic animals to unpalatable volatile compounds and facilitate the development of aquaculture diets that optimise the volatile profile of edible tissues. [ABSTRACT FROM AUTHOR]

This study aimed to explore the potential of a fermentation technology to reduce off-flavour perception and its underlying mechanisms. Results revealed that yeast fermentation (YF) significantly ameliorated the off-flavour of pig liver (p < 0.05). Specifically, YF pre-treatment decreased the relative abundance of α-helix and fluorescence intensity while increasing the surface hydrophobicity and S S level and loosening the microstructure of myofibrillar proteins (MPs) in pig liver. Additionally, the appropriate fermentation treatments enhanced the MP–aldehyde binding capacity by 0.25–1.30 times, demonstrating that YF-induced conformational modifications in pig liver proteins made them more prone to interacting with characteristic aldehydes. Moreover, molecular docking results confirmed that hydrophobic interactions are the primary drivers of MP–aldehyde binding. These findings suggest that YF technology holds immense promise for modulating off-flavour perception in liver products by altering protein conformation. • Yeast fermentation altered the secondary, tertiary structures and microstructure of PLPs. • Yeast fermentation enhanced the binding ability of aldehydes to PLPs. • PLPs bound to 5 characteristic aldehydes via non-covalent interactions. • The flavour regulation of PL could be achieved by fermentation. [ABSTRACT FROM AUTHOR]

Aims: Geosmin is associated with off‐flavour problems in recirculating aquaculture systems (RAS) and represents an economic problem for the aquaculture industry. This study aims at investigating factors influencing the composition of the bacterial microbiota, in particular the presence of geosmin producers and the environmental and farming factors favouring geosmin accumulation. Methods and Results: Several water quality parameters were correlated to the composition of the microbiota with special emphasis on the presence of geosmin producers within 26 different RAS from four European countries. Three novel groups of geosmin‐producing bacteria were quantified to identify potential correlations with geosmin concentration. Conclusions: The microbiome differed significantly between systems. However, phosphate levels, calcium levels and redox potential correlated to geosmin concentration in the water and the presence of the Actinomycetales geosmin‐producers but not with the presence of other groups of geosmin‐producing bacteria. Oxygen levels and conductivity were found to negatively correlate with geosmin concentration. A large proportion of the detected geosmin producers represented novel taxonomic groups not previously linked with this activity. Significance and Impact of the Study: These results improve our understanding of the diversity of microbiota in RAS and the water quality parameters favouring the populations of geosmin‐producing bacteria and the production of geosmin. [ABSTRACT FROM AUTHOR]

Summary: Yeast extract (YE) is a kind of umami additives used in fermented condiments, it also has special yeasty flavour (YF), which is not widely accepted by some consumers. In this paper, the technology of mixed microbial transformation was applied to eliminate or cover up YF during mixed fermentation. FG10, which is produced by Hubei Angel Yeast Co. Ltd, is a kind of YE that has the distinctive YF and has been applied to the market. It had good sensory evaluation after 6 h with Saccharomycopsis fibuligera and Lactococcus lactis. At 6 h, compared with single fermentation, the number of bacteria of L. lactis was enhanced by 34.28%, and the number of bacteria of S. fibuligera was reduced by 47.93%. The yeasty flavoured substances propionic acid and butyric acid were completely removed. The result of GC‐MS showed that acetal, phenyl acetaldehyde, 2,4‐dimethylbenzaldehyde, benzaldehyde, isoamyl alcohol, 5‐methyl‐2‐furan methanol, phenylethanol were generated or increased. Furthermore, the amino acids of YE were significantly different after fermentation by different microorganisms (P < 0.05), The flavour compounds and amino acids in YE before and after fermentation had closely correlation (r = 0.94), the consumption of amino acids in mixed fermentation promoted the variety of corresponding flavour compounds, which boosted the formation of free YF YE. In addition, taste substances lactic acid generated 6.27 ± 0.115 g L−1 and nucleotides improved 15.05%, which were beneficial to natural YF free seasoning with YE as raw material. [ABSTRACT FROM AUTHOR]

The worldwide demand for pulse-based products is increasing in the face of climate change, but their acceptability is limited due to the presence of off-flavours. Off-notes contribute to negative perceptions of pulses (beany notes). Volatile compounds belong to a large variety of chemical classes. They are mainly produced from the oxidation of unsaturated free fatty acids and the degradation of amino acids during seed development, storage, and transformation (dehulling, milling, and starch or protein production). This review aims to provide an overview highlighting the identification of these molecules in different pulses, their potential origins, and their impact on perceptions. However, data on odour-active compounds in pulses are sparse, as they are limited to those of two studies on peas and lupins. A better knowledge of the volatile compounds involved in the off-notes and their origins should allow for drawing efficient strategies to limit their impact on overall perception for more acceptable healthy food design. [ABSTRACT FROM AUTHOR]

Summary: Packages of ready‐to‐eat (RTE) wild rocket and lettuce baby leaves were subjected during 8 days of cold storage to a chronic temperature abuse (CTA) at sub‐optimal storage temperature (10 °C) or to a short‐term (6 h) abuse at ambient temperature (STA) to evaluate the impact of two temperature abuse scenarios on gas composition within the packages, leaf sensory quality and volatile organic compounds (VOCs). In both species, the CTA scenario had a markedly higher impact on gas composition, sensory quality and off‐odour formation than the STA, and the limit of sensory acceptability was reached in the CTA scenario 4 days or more earlier than in the STA. Sulphur compounds were the main responsible for off‐odour perception in both leafy salads. Results from the present study may be useful in the assessment of critical points in the cold chain of RTE fresh produce and in prioritising actions towards improved cold‐chain management. [ABSTRACT FROM AUTHOR]

The occurrence of garlic with expressed mouldy, musty and cork taint-like off-flavour is of serious concern for the food industry as it may cause significant economic damage. In this study, we investigated a total of 42 garlic samples for their concentrations of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA). The TCA odour thresholds in two garlic matrices were determined to evaluate the impact of the TCA presence on garlic's flavour properties. While TCA was identified in more than 45% of the samples in concentrations of up to 78 µg kg−1, TBA was not detected in any of the samples. In approx. 35% of the garlic samples, the concentrations were higher than the odour threshold. It is noteworthy that garlic preparations that are to be further processed by the food industry, on average, show higher contamination rates than samples drawn from retail. The results of this survey demonstrate that it is of the utmost importance for food processing companies to perform a sensory evaluation of the garlic or garlic formulations prior to their use in order to avoid economic damage and to minimize food waste. [Display omitted] • The occurrence of 2,4,6-trichloroanisole (TCA) leads to off-flavour formation in garlic. • 2,4,6-Trichloroanisole was detected in 45% of the investigated garlic samples. • The odour activity value was higher than 1 in 35% of the samples. • The presence of TCA in garlic is of serious concern for the food industry. [ABSTRACT FROM AUTHOR]

In this study, the effect of different adsorbents on the reduction of off-flavours within a lentil protein isolate (LPI) was examined by isolating volatile compounds using headspace solid-phase microextraction (HS-SPME), and analysing with gas chromatography–mass spectrometry (GC–MS). LPIs were treated with Amberlite-XAD16N, Amberlite-XAD7HP, Amberlite-XAD4, Sepabeads-SP207 and Diaion-HP20 adsorbents, and then total peak areas of each of the flavour compounds were compared with controls. XAD16N, SP207, and HP20 were able to reduce the levels of aldehydes by 32%, 32%, and 41%, respectively. The aldehyde group of compounds (78% being hexanal) represented the major volatile compound within the LPI. All adsorbents significantly reduced 3,5-octadien-2-one by 61–92%. XAD16N and HP20 were found to be the most effective adsorbents in removing alcohols with decreases of 84% and 80%, respectively. Findings from this study could be integrated into the traditional wet extraction process to produce blander plant protein ingredients. [ABSTRACT FROM AUTHOR]

The worldwide demand for pulse-based products is increasing in the face of climate change, but their acceptability is limited due to the presence of off-flavours. Off-notes contribute to negative perceptions of pulses (beany notes). Volatile compounds belong to a large variety of chemical classes. They are mainly produced from the oxidation of unsaturated free fatty acids and the degradation of amino acids during seed development, storage, and transformation (dehulling, milling, and starch or protein production). This review aims to provide an overview highlighting the identification of these molecules in different pulses, their potential origins, and their impact on perceptions. However, data on odour-active compounds in pulses are sparse, as they are limited to those of two studies on peas and lupins. A better knowledge of the volatile compounds involved in the off-notes and their origins should allow for drawing efficient strategies to limit their impact on overall perception for more acceptable healthy food design.

Extensive work on the chemical aspects of off-flavour in wine has been carried out by international researchers, but not as many studies focus on the organoleptic effects. This literature review therefore has a focus on the status of the sensory aspects of compounds associated with specific off-flavours in red wine, viz. three volatile phenols, as well as 2-isobutyl-3-methoxypyrazine and 2,4,6-trichloranisole. The review discusses sources and effects of the selected compounds in red wine, and what previous workers have found pertaining to the mechanisms of the odour perception of aroma compounds, odour detection thresholds, and issues relating to the effects of the matrix. It also considers the factors that have been found to cause differences in olfactory perceptions between panellists/judges, and covers some of the work that has been carried out in characterising perceptual interactions between compounds in wine. Gaps that exist in the current literature are highlighted. [ABSTRACT FROM AUTHOR]

In the ultra-high temperature (UHT) process, milk is subject to temperatures above 135 °C for few seconds giving a product with a shelf-life of several months. The raw milk quality, UHT process and storage conditions affect the stability. In this study, the stability of UHT milk produced in an indirect system was evaluated by studying changes in taste, colour, fat separation, fat adhesion to the package, sedimentation, gelation, heat coagulation time, pH and ethanol stability during storage for up to one year at different temperatures. UHT milk stored at 4 and 20 °C had the longest shelf-life of 34–36 weeks, limited by sediment formation. Storage at 30 and 37 °C considerably decreased the shelf-life of UHT milk to 16–20 weeks, whereby changes in sediment formation, taste and colour were the limiting factors. Our results suggest that the changes observed at the different storage temperatures can be explained by different known mechanisms.

This study investigated the relationship between bacterial counts and volatile organic compound (VOC) formation in 3.9% fat milk. The milk was stored at 7, 10, 13, 15 and 19 (±1 °C). Volatile compounds were measured using solid‐phase microextraction with gas chromatography. Enzyme activity was also monitored throughout the shelf life. Results show that volatile organic compound concentrations increased with higher bacterial counts (5.0–7.0 log10 cfu/mL). Bacterial counts correlated closely with acetaldehyde, butanone, ethanol, hexanal, acetone and fatty acid concentrations. Results indicate that protease and lipase activities increased and correlated closely with VOCs. Formation of VOCs was detectable when protease and lipase activities reached 1.2–1.3 U/mL and 0.32–0.350 meq/mL, respectively. These findings provide a basis for the monitoring of milk quality using chemical sensors that are sensitive to VOCs, particularly under conditions of thermal abuse. [ABSTRACT FROM AUTHOR]

Highlights • Rams have superior production performance than castrates. • Small sensory differences exist between meat from rams and castrates. • Consumers prefer castrate meat but do not dislike ram meat. • More intense flavour and off-flavours are found in meat from older lambs. Abstract Meat from ram lambs is often considered inferior to meat from castrated lambs, especially in older or heavier animals. This study aimed to determine if differences exist in the sensory quality and acceptability of meat from rams and castrates, slaughtered at mean ages of 196 or 385 days. Rams had higher average daily gain, feed conversion efficiency, total weight gain and lower carcass fatness than castrates. A triangle test (n = 81 consumers) showed a difference (P < 0.05) in the sensory quality of meat from rams vs castrates. A 9-point hedonic test involving 100 consumers showed that, although meat from both rams and castrates was 'liked', meat from castrates scored higher (P < 0.05) in Overall Liking, Flavour Liking and Tenderness Liking. Meat from castrates was also rated lower (P < 0.05) in Unpleasant Taste/Off-Flavour Intensity. Flavour Intensity and Unpleasant Taste/Off-Flavour Intensity increased (P < 0.05) with age at slaughter. This consumer study revealed that while meat from castrates was higher in Overall Liking, Flavour Liking and Tenderness Liking and lower in Unpleasant Taste/Off-Flavour Intensity than meat from rams, both meats were 'liked' by consumers. [ABSTRACT FROM AUTHOR]

The microorganisms of spoiled industrial-scale Sichuan paocai (ISSP) were isolated using six types of media, and 16S rRNA and 26S rRNA gene sequence analyses were used to identify the isolates. Meanwhile, the microbial composition was investigated using a culture-independent method through 16S rRNA and ITS sequencing on an Illumina MiSeq platform. The results obtained by these two methods were compared. Furthermore, characteristics of the isolated microorganisms responsible for ISSP spoilage were studied. Sixty-two strains belonging to twenty-three species, including three ammonia-producing genera, two gas-producing genera, two pectinase-producing genera, two cellulase-producing genera, three film-producing genera and one slime-producing genus, were isolated. Lactobacillus , Bacillus , Debaryomyces and Kazachstania were the dominant genera as confirmed through both culture-dependent and culture-independent methods. Bacillus , Paenibacillus , Pichia and Debaryomyces could be the main microorganisms responsible for ISSP spoilage. Bac. licheniformis was closely correlated with the off-flavour of ISSP. Pae. peoriae , Bac. stratosphericus , Bac. toyonensis and Bac. cereus were responsible for tissue softening, and Bac. subtilis , Bac. methylotrophicus , Pic. membranifaciens and Deb. hansenii caused film formation. [ABSTRACT FROM AUTHOR]

(Z)-4-undecenal (Z4-11Al) is the volatile pheromone produced by females of the vinegar fly Drosophila melanogaster. Female flies emit Z4-11Al for species-specific communication and mate-finding. A sensory panel finds that synthetic Z4-11Al has a characteristic flavour, which can be perceived even at the small amounts produced by a single female fly. Since only females produce Z4-11Al, and not males, we can reliably distinguish between single D. melanogaster males and females, according to their scent. Females release Z4-11Al at 2.4 ng/h and we readily sense 1 ng synthetic Z4-11Al in a glass of wine (0.03 nmol/L), while a tenfold concentration is perceived as a loud off-flavour. This corroborates the observation that a glass of wine is spoilt by a single D. melanogaster fly falling into it, which we here show is caused by Z4-11Al. The biological role of Z4-11Al or structurally related aldehydes in humans and the basis for this semiochemical convergence remains yet unclear. [ABSTRACT FROM AUTHOR]

Abstract: The bioconcentration of waterborne geosmin in rainbow trout, Oncorhynchus mykiss (Waldbaum) was assessed. Fifty rainbow trout with a mean (SD) weight of 226.6 (29.0) g and lipid content of 6.2 (0.6) % (w/w) were exposed to geosmin in static water for 0, 2, 4, 6, 8, 12, 24, 36, 48 and 120 hr, with one tank containing five fish for each exposure period. Geosmin concentrations were measured in fish tissue and water samples collected over time. With time the geosmin concentration in the fish increased and decreased in the water. However, the total absolute amount of geosmin in the system declined over time which could be explained by induction of biotransformation. This is in accordance with the decreasing lipid normalized geosmin levels in the liver compared with the liver‐free carcass. Geosmin distribution within rainbow trout clearly is not exclusively governed by the lipid content of tissues. In vivo geosmin bioconcentration in rainbow trout is slower and the body burden reached is lower than the generally accepted theoretical model predicts. [ABSTRACT FROM AUTHOR]

The identification of compounds producing a characteristic off-flavour in fresh beef meat obtained from different locations is essential to avoid consumer rejection. The volatile compounds of fresh beef samples were extracted by solid phase micro extraction (SPME) and their odour was evaluated by using olfactometry analysis (GC-O). The compound responsible for the characteristic off-flavour was identified by using GC-MS and quantified in different beef samples obtained from different locations. The sniffing analysis revealed eight odour active zones being four of them identified as 2,3-butanedione, allyl methyl sulfide, 1-(methylthio)propane and 1-(methylthio)-1-propene (Z). The most potent odorant was 1-(methylthio)propane described as garlic, cabbage, oxidized iron, solvent and rancid odour. All panellists attributed the characteristic off-flavour detected in fresh beef to the odour of 1-(methylthio)propane. A chromatographic method was validated to quantify 1-(methylthio)propane in fresh beef. Several beef samples were characterized by this off-flavour although its origin was not elucidated. [ABSTRACT FROM AUTHOR]

The aim was to study lipase, lipoxygenase (LOX) and peroxygenase (POX) activities in oat and faba bean samples to be able to evaluate their potential in formation of lipid-derived off-flavours. Lipase and LOX activities were measured by spectroscopy, and POX activities via the formation of epoxides. An ultra-high performance liquid chromatography method was developed to study the formation of fatty acid epoxides. The epoxides of esters were measured by gas chromatography. Mass spectroscopy was used to verify the identity of the epoxides. Both oat and faba bean possessed high lipase activities. In faba bean, LOX catalysed the formation of hydroperoxides, whose break-down products are the likely cause of off-flavours. Since oat had low LOX activity, autoxidation is needed to initiate lipid oxidation. Oat had high POX activity, which is able to convert hydroperoxides to epoxy and hydroxy fatty acids that could contribute significantly to off-flavours. POX activity in the faba bean was low. Thus, in faba bean volatile lipid oxidation products could rapidly be formed by LOX, whereas in oat reactions are slower due to the need of autoxidation prior to further reactions. [ABSTRACT FROM AUTHOR]

Yeast extracts is a kind of food ingredient for enhancing flavor, but some yeast extract samples had yeasty odour (off-flavour). The aim of this study was to detect key aroma compounds leading to the yeasty odour. Volatile compounds of 3 yeast extracts (with yeasty odour), FA and FB, LC were extracted by solid phase micro-extraction (SPME) and solvent assisted flavour evaporation (SAFE) respectively, and analysed by gas chromatography-olfactrometry-mass spectrometry (GC-O-MS) and aroma extract dilution analysis (AEDA) techniques. Thirty aroma-active compounds were detected, among them 4-methylphenol, 3-methylpyridine, 3-methylbutanoic acid, propanoic acid with high FD factors (FD = 125, 125, 625, 125, ≥25), were identified as the key off-flavours responsible for yeasty and their accurate quantification were done by external standard method in SIM mode. Calculation of the OAVs revealed 3-methylbutanoic acid, 3-methylpyridine, 4-methylphenol as the key odourants in the extract. For the verification of analyzed off-flavours, sensory evaluations of aroma model were conducted by eight panelists, and the result showed that aroma recombinate had the yeasty odour profile similar with the original yeast extracts. The methods were successful for the detection of off-flavors in yeast extract and the four off-compounds analyzed were mainly responsible for the yeasty flavour. [ABSTRACT FROM AUTHOR]

This study investigated relationships between the volatile profile and balanced flavour of high sensory quality ewe's raw milk commercial cheeses, and those relations between certain volatile compounds and off-flavours in defective cheeses. Commercial cheeses were selected in the routine sensory quality control from 27 farmhouses. High sensory quality cheeses showed a particular desirable balanced flavour and volatile profile. However, an imbalanced composition of volatile compounds was found in off-flavour cheeses. Rancid off-flavour was mainly related to an excessive concentration of n-butanoic and n-hexanoic acids, and their corresponding ethyl esters, generated by strong lipolysis during ripening. Animal off-flavour was associated with the generation of 3-methylbutan-1-ol, 2-phenylethanol and 4-methylphenol originated by amino acid catabolism after intense proteolysis. Finally, acid off-flavour was related to an excessive abundance of acetic acid generated mainly by strong glycolysis at early stages of ripening. [ABSTRACT FROM AUTHOR]

Pork liver has excellent nutritional properties but is a highly perishable product often rejected by consumers due to its strong unpleasant flavour. The objective of this study was to analyze the feasibility of the deodorization and defatting of dried pork liver by means of supercritical CO 2 (SC-CO 2) and conventional vacuum steam distillation (VSD). The results showed that both deodorization techniques were effective at reducing volatile organic compounds (VOCs). Through VSD, the VOC content was reduced by 67.6% UA, while an 81.3% UA reduction was achieved by SC-CO 2 , with respect to dried pork liver. In addition, 3 characteristic compounds of raw pork liver were completely eliminated by applying SC-CO 2 , which could potentially reduce the characteristic mushroom (1-octen-3-ol), fatty and green (1-nonanol), and fishy ((E , E)− 2,4-heptadienal) off-flavours. Therefore, SC-CO 2 could be considered a promising technique for the elimination of VOCs, and furthermore it leads to a reduction in the fat content (24.9%). • Vacuum steam distillation (VSD) reduced VOC content by 67.6%. • Supercritical CO 2 (SC-CO 2) reduced VOC content by 81.3%. • Through SC-CO 2 , 3 VOCs that provide the characteristic odour of liver were eliminated. • SC-CO 2 was an effective technique at reducing the fat content (24.9%). [ABSTRACT FROM AUTHOR]

Acetaldehyde and ethanol are already present in detectable levels at the time of harvest, under aerobic conditions and in healthy, undamaged fruit. Both metabolites can be detected, at different concentrations, in all cultivars. Several hours after harvest, the levels of acetaldehyde in cultivars Summit, Techlovan and Kordia were 6.41, 9.78 and 22.00 mg/l, respectively. Both ethanol and acetaldehyde accumulate to significant levels in anaerobically stored cherries, particularly in atmospheres with high levels of CO2. The highest levels of ethanol observed, after 31 days of exposure to anaerobic conditions, were in the cultivars Techlovan (1,159 mg/l) and Summit (1,168 mg/l); both concentrations are are broadly similar. The metabolites decreased after a return to aerobic conditions, but remained higher than the levels first observed. Sweet cherries stored in anaerobic conditions are also sensitive to the development of off-flavours in the first 24 hours after opening the storage box. The very slow ripening of the fruit under anaerobic conditions was satisfactorily quantified by measuring the higher degree of fruit firmness, when the usual, visual attributes of ripeness were almost undetectable. Stems also remained green, in contrast to the usual browning that occurs under normal atmospheres. Discrimination analysis of various parameters observed gave a good resolution of different cultivars.

Defatting soybean by sophisticated oil extraction method utilising supercritical CO 2 resulted in a significant decrease in the residual phospholipids (PLs) compared with soymeal obtained by conventional cold percolation method utilising hexane as the extraction solvent. Interestingly, the levels of residual PLs showed a proportionate relationship with thiobarbituric acid (TBA) number, an indicator of lipid peroxidation responsible for off-flavour generation. Furthermore, two oleosins (18 and 24 kDa) were isolated from the oil bodies extracted from soybean seeds and positively characterised for phospholipase A 2 (PLA 2 ) activity, suggesting their plausible involvement in off-flavour generation in soymeal. The treatment of soybean seeds, before oil extraction, with different concentrations of biotic elicitors such as chitosan and jasmonic acid also significantly reduced the levels of residual PLs as well as the TBA number. The biotic elicitor treatment could thus prove to be an important strategy for the reduction of off-flavour in protein-rich soymeal. [ABSTRACT FROM AUTHOR]

Characteristic off-flavours may occur in uncastrated male pigs depending on the accumulation of androstenone and skatole. Feasible processing of strongly tainted carcasses is challenging but gains in importance due to the European ban on piglet castration in 2018. This paper investigates consumers' acceptability of two sausage types: (a) emulsion-type (BOILED) and (b) smoked raw-fermented (FERM). Liking (9 point scales) and flavour perception (check-all-that-apply with both, typical and negatively connoted sensory terms) were evaluated by 120 consumers (within-subject design). Proportion of tainted boar meat (0, 50, 100%) affected overall liking of BOILED, F (2, 238) = 23.22, P < .001, but not of FERM sausages, F (2, 238) = 0.89, P = .414. Consumers described the flavour of BOILED-100 as strong and sweaty. In conclusion, FERM products seem promising for processing of tainted carcasses whereas formulations must be optimized for BOILED in order to eliminate perceptible off-flavours. Boar taint rejection thresholds may be higher for processed than those suggested for unprocessed meat cuts. [ABSTRACT FROM AUTHOR]

Sales of bottled drinking water have shown a large growth during the last two decades due to the general belief that this kind of water is healthier, its flavour is better and its consumption risk is lower than that of tap water. Due to the previous points, consumers are more demanding with bottled mineral water, especially when dealing with its organoleptic properties, like taste and odour. This work studies the compounds that can generate obnoxious smells, and that consumers have described like swampy, rotten eggs, sulphurous, cooked vegetable or cabbage. Closed loop stripping analysis (CLSA) has been used as a pre-concentration method for the analysis of off-flavour compounds in water followed by identification and quantification by means of GC-MS. Several bottled water with the aforementioned smells showed the presence of volatile dimethyl selenides and dimethyl sulphides, whose concentrations ranged, respectively, from 4 to 20 ng/L and from 1 to 63 ng/L. The low odour threshold concentrations (OTCs) of both organic selenide and sulphide derivatives prove that several objectionable odours in bottled waters arise from them. Microbial loads inherent to water sources, along with some critical conditions in water processing, could contribute to the formation of these compounds. There are few studies about volatile organic compounds in bottled drinking water and, at the best of our knowledge, this is the first study reporting the presence of dimethyl selenides and dimethyl sulphides causing odour problems in bottled waters. [ABSTRACT FROM AUTHOR]

One of the most common taints in foods is a musty or earthy odour, which is commonly associated with the activity of microorganisms. Liquid foods, particularly wine and water, can be affected by this defect due to the presence of certain aromatic organic compounds at very low concentrations (ng/L) consistent with human threshold perception levels. The volatile compounds responsible for a mouldy off-aroma include approximately 20 compounds, namely, haloanisoles, geosmin, 2-methylisoborneol, several alkyl-methoxypyrazines, 1-octen-3-ol, 1-octen-3-one, trans-octenol, 3-octanone, fenchol and fenchone. Methods for determining these very low concentrations of odour compounds must be extremely sensitive and selective with efficient preconcentration treatments. A number of extraction techniques based on LLME (liquid–liquid microextraction), SPME (solid-phase microextraction) or SBSE (stir-bar sorptive extraction) can be applied and should be selected on a case-by-case basis. Moreover, recent developments in GC instrumentation coupled to different detection systems can effectively increase the selectivity and sensitivity of the analysis of target compounds. [ABSTRACT FROM AUTHOR]

Lezzet gıdanın beğenisini belirleyen başlıca faktördür ve aynı zamanda tüketici tercihlerini de etkilemektedir. Bundan dolayı, lezzet problemleri genellikle tüketici şikayetleri olarak geri dönmektedir ve gıdalardaki lezzet kusurları süt ve süt ürünlerinin de içinde bulunduğu gıdaların tüketiciler tarafından kabul edilmemesinin başlıca nedenidir. Süt ve süt ürünlerinde lezzet ve istenmeyen lezzet son on yılın ilgi çeken araştırma konusu olmuştur; bu bağlamda da lezzet gelişiminin takibi için kullanılan analitik teknikler gelişmiştir ve birçok süt ve süt ürünündeki istenmeyen lezzet bileşikleri halen araştırılmaktadır. Süt ve ürünlerindeki istenmeyen lezzete neden olan kimyasallar; çevresel kaynaklardan bulaşma, hayvan beslenmesi, gıda içinde meydana gelen kimyasal reaksiyonlar ve diğer kaynaklar orijinli olabilir. Bu makalenin amaçlarını, tanımlamaların ardından, istenmeyen lezzet için muhtemel kaynakların ve kimyasal bileşiklerin özetlenmesi ve süt ve süt ürünlerindeki istenmeyen lezzet kavramı ile ilgili farklı yaklaşımların tartışılması oluşturmaktadır.

Cork shows an active role in the sorption of volatile phenols from wine. The sorption properties of 4-ethylphenol and 4-ethylguaiacol phenols in hydro-alcoholic medium placed in contact with suberin extracted from cork were especially investigated. To that purpose, suberin was immersed in model wine solutions containing several concentrations of each phenol and the amount of the compound remaining in the liquid phase was determined by SPME–GC–MS. Sorption isotherms of 4-ethylguaiacol and 4-ethylphenol by suberin followed the Henry’s model. The solid/liquid partition coefficients ( K SL ) between the suberin and the model wine were also determined for several other volatile phenols. Suberin displayed rather high sorption capacity, which was positively correlated to the hydrophobicity of the volatile. Finally, the capacity of suberin to decrease the concentration of 4-ethylphenol and 4-ethylguaiacol was also tested in real wines affected by a Brettanomyces character. It also lead to a significant reduction of their concentration in wine. [ABSTRACT FROM AUTHOR]

The unpleasant odor of an off-flavor is mostly caused by only one or, sometimes, several volatile compounds with very low odor threshold values giving the typical unpleasant odor taint of the spoiled food product. 2-Aminoacetophenone is an aroma compound which causes the untypical aging off-flavor in Vitis vinifera white wines. Ultrasound assisted headspace solid phase microextraction ( UA-HS-SPME) and direct immersion solid phase microextraction ( DI-SPME) coupled with gas chromatography-mass spectrometry ( GC-MS) were tested and optimized for determination of 2-aminoacetophenone in Riesling wines fermented by different yeast strains. [ABSTRACT FROM AUTHOR]

Recirculation aquaculture systems ( RASs) are increasingly considered as production systems of the future with a minimum ecological impact for the production of aquatic food. To maintain a good water quality and to produce quality and healthy fishery products, the systems depend on a diverse microbial community involved in different processes of water purification but also in unwanted effects. The article reviews the present knowledge on microorganisms in RAS, their relative distribution within the system compartments and their role in system performance. The system possesses different microniches in which microorganisms retrieve their preferential conditions for oxygen and nutrients. Ammonia and nitrite are oxidized under aerobic conditions into less toxic compounds. Anaerobic ammonium oxidizers in the biofilm oxidize anaerobically both ammonia and nitrites into less harmful dinitrogen gas. Heterotrophic bacteria mineralize organic matter derived from uneaten feeds, dead bodies and excreta of fish. Under conditions of high organic load and high C/N content, nitrifiers are overgrown by heterotrophs with negative effects to the nitrification process. For not yet understood reasons, the presence of off-flavour-producing microorganisms occurs also in RAS. Microbial management and management of inputs to the systems to prevent the proliferation of pathogens are discussed and possible management techniques of off-flavours are also presented. Research orientations are given to explore further the potential of heterotrophic bacteria in microbial management and intensive aquaculture production in systems other than RAS. [ABSTRACT FROM AUTHOR]