Generation Of Aroma Compounds Research Articles

Lipolysis and aroma generation as mechanisms involved in masking boar taint in sodium reduced fermented sausages inoculated with Debaryomyces hansenii yeast.

The use of boar back fat for processing of fermented sausages may cause the presence of abnormal odours. In dry-cured products, ripening time is essential to develop the sensory characteristics. Yeast has been proposed as an alternative to mask boar taint odour through its metabolic activity but it is necessary to elucidate which mechanisms are involved. The aim is to study the effect of Debaryomyces hansenii inoculation on the lipolysis process and generation of aroma compounds in fermented sausages manufactured with boar back fat at two different ripening times. D. hansenii inoculated sausages had a higher degree of lipolysis as demonstrated by higher content of free fatty acids, ester compounds and branched aldehydes which contribute the fruity odour. The increase in lipolysis produced by D. hansenii inoculation was not followed by an increase in oxidation during processing possibly due to the metabolic activity of yeast. The effect of back fat type was scarcely appreciated whereas ripening time had a stronger effect on sausage. Boar sausages were characterised by a lower polyunsaturated fatty acid profile and lesser lipolysis than gilt sausages. Yeast inoculation with D. hansenii and long ripening time were appropriate strategies to limit the perception of boar taint in dry fermented sausages. © 2017 Society of Chemical Industry.

Screening of Debaryomyces hansenii Strains for Flavor Production under a Reduced Concentration of Nitrifying Preservatives Used in Meat Products.

A total of 15 Debaryomyces hansenii strains from different food origins were genetically characterized and tested on a culture medium resembling the composition of fermented sausages but different concentrations of nitrifying preservatives. Genetic typing of the D. hansenii strains revealed two levels of discrimination: isolation source or strain specific. Different abilities to proliferate on culture media containing different concentrations of nitrate and nitrite, as sole nitrogen sources and in the presence of amino acids, were observed within D. hansenii strains. Overall metabolism of amino acids and generation of aroma compounds were related to the strain origin of isolation. The best producers of branched aldehydes and ethyl ester compounds were strains isolated from pork sausages. Strains from cheese and llama sausages were good producers of ester compounds and branched alcohols, while vegetable strains produced mainly acid compounds. Nitrate and nitrite reduction affected in different ways the production of volatiles by D. hansenii.

Draft Genome Sequence of Lactococcus lactis subsp. lactis bv. diacetylactis CRL264, a Citrate-Fermenting Strain.

We report the draft genome sequence of Lactococcus lactis subsp. lactis bv. diacetylactis CRL264, a natural strain isolated from artisanal cheese from northwest Argentina. L. lactis subsp. lactis bv. diacetylactis is one of the most important microorganisms used as starter culture around the world. The CRL264 strain constitutes a model microorganism in the studies on the generation of aroma compounds (diacetyl, acetoin, and 2,3-butanediol) by lactic acid bacteria. Our genome analysis shows similar genetic organization to other available genomes of L. lactis bv. diacetylactis strains.

Effect of amino acid supply on the transcription of flavour-related genes and aroma compound production during lager yeast fermentation

The objective of this study was to investigate the effect of adding selected amino acids (proline, leucine, cysteine, valine, glutamine and isoleucine) to synthetic wort on the generation of aroma compounds with respect to the transcription levels of specific genes involved in their biosynthetic pathway under brewery fermentation. The results showed that the changes in the selected amino acid levels had no eminent impact on the general course of fermentation. Addition of leucine increased the production of isoamyl alcohol and isoamyl acetate and 2-methylbutyl acetate. Adding valine and isoleucine increased the production of isobutanol and 2-methyl butanol, respectively. Overall, total higher alcohol production increased by amino acid supplementation; this effect could be associated with the upregulation of pyruvate decarboxylases and phenylpyruvate decarboxylase. Amino acid supplementation resulted in a reduction in the final total concentration of esters, especially ethyl acetate. This reduction might have been caused by the downregulation of the genes participating in ester biosynthesis. Our results demonstrate that during lager yeast fermentation, the production of aroma-active compounds can be significantly affected by changing the supply of even one amino acid.

Generation of aroma compounds in a fermented sausage meat model system by Debaryomyces hansenii strains

The ability of seven Debaryomyces hansenii strains to generate aroma compounds in a fermented sausage model system was evaluated. The presence of the yeast, in the inoculated models, was confirmed by PCR amplification of M13 minisatellite. Volatile compounds production was analysed using Solid Phase Micro-Extraction and gas chromatography/mass spectrometry. Forty volatile compounds were detected, quantified and their odour activity values (OAVs) calculated. All volatile compounds increased during time in the inoculated models although significant differences were found amongst them. Ester and sulphur production was strongly dependent on the strain inoculated. D. hansenii P2 and M6 strains were the highest producers of sulphur compounds where dimethyl disulphide and dimethyl trisulfide were the most prominent aroma components identified by their OAVs whereas, M4 showed the highest OAVs for ester compounds followed by the P2 strain. The meat model system has been useful to show the real ability of yeast strains to produce aroma compounds.

Establishment of the contribution of volatile compounds to the aroma of fermented sausages at different stages of processing and storage

Abstract The generation of aroma compounds through the curing process of dry fermented sausages was studied. The most important aroma compounds were determined using their odour-activity values (OAVs). The compound quantification in the headspace (HS) was carried out by solid phase microextraction (SPME) and the total concentration in the sausage by multiple headspace SPME (multiple HS-SPME) using gas chromatography and mass spectrometry. The main compounds that contributed to the aroma of dry fermented sausages were those with the highest oil OAVs such as 3-methyl butanal, 2-methyl butanal, octanal, diacetyl and ethyl 2-methyl butanoate that were important from the beginning of the process. Other compounds were important contributors as they were generated at the end of process, including propanal, pentanal, hexanal, ethyl 3-methyl butanoate, 1-octen-3-ol, 3-methyl butanoic acid, 2-methyl propanoic acid, ethyl hexanoate and nonanal. However, the aroma perceived in the HS was due to compounds with the highest air OAVs such as 3-methyl butanoic acid, ethyl 2-methyl butanoate, nonanal and octanal. In many cases, the percentage of the aroma compound released to the HS was around 10–20% of the total concentration in the sausage.

Generation of aroma compounds in sourdough: Effects of stress exposure and lactobacilli–yeasts interactions

The effects of the interaction between Saccharomyces cerevisiae LBS and Lactobacillus sanfranciscensis LSCE1 and of their responses to acid, oxidative or osmotic stress on alcohol and aroma production were assessed. The exposure of S. cerevisiae LBS and L. sanfranciscensis LSCE1 cells to oxidative, acid or osmotic sub-lethal stress gave rise to a common or specific responses. γ-decalactone, 2(5H)-furanones and aldehydes were overproduced by LAB following oxidative stress. The acid stress induced both in yeasts and LAB, as well as in their co-cultures, a relevant accumulation of isovaleric and acetic acids and higher alcohols. A cross-exposure of yeasts and LAB to their preconditioned media, generated in S. cerevisiae a release of esters including esters of long-chain unsaturated fatty acids coming from membrane phospholipids. These esters were excreted also by yeasts following a pressure stress.

Generation of aroma compounds from Ditaxis heterantha by Saccharomyces cerevisiae

Ditaxis heterantha, a plant of the Euphorbiaceae family, is growing wild in the semiarid regions of Mexico. The seed endosperm contains yellow pigments (carotenoids). By high-pressure liquid chromatography the total pigment (TP) was separated into seven fractions: two of them, heterathin (F4) and ditaxin (F5), characterized as apocarotenoids, represent 80% of TP. Both molecules have double bonds, which seem to be the target for degradation and aroma formation. In this work, TP, F4, and F5 were supplied to nine cultures able to degrade lutein. From these strains, only one (identified as Saccharomyces cerevisiae) was able to produce aromas from either TP or F4. Using TP as substrate, the produced aromas were 4-oxo-isophorone (1), isophorone (2), cinnamic aldehyde (6), 3-hydroxy-beta-cyclocitral (7), safranal (8), geranyl (9), 3-oxo-alpha-ionone (10), 3-oxo-alpha-ionol (11), 3-oxo-7,8-dihydro-alpha-ionone (12), and eugenol (13). Of these aromas, only seven were produced from F4: (1), (2), (7), (8), (10), (11), and (12). In both cases, safranal was the main degradation product (30%). The enzymatic activity responsible for this effect was found in the cytosolic fraction and detected only when S. cerevisiae was grown in the presence of TP or F4.

Addition of amino acids to grape juice of the Merlot variety: Effect on amino acid uptake and aroma generation during alcoholic fermentation

The effects of adding selected amino acids (phenylalanine, alanine, aspartic acid and threonine) to grape juice on the generation of aroma compounds and on amino acid uptake were studied. The fermentation kinetics varied according to the quantities of amino acids added. The fermentations finished more quickly in supplemented juices and their alcoholic content was significantly higher than in the control ( p < 0.05). Amino acids were consumed mainly in the first quarter of fermentation. Higher alcohol formation took place at the same time as ethanol formation: with more amino acids present in the medium, more phenyl ethanol ( p = 0.01) and benzyl alcohol were formed while isoamyl alcohol production decreased. The contents of isoamyl and phenylethyl acetates, ethyl hexanoate and ethyl octanoate, as well as most fatty acids increased during the fermentation, reaching a maximum for 10% of ethanol; with higher alcoholic contents, their concentrations decreased.

Bioconversion of lutein using a microbial mixture—maximizing the production of tobacco aroma compounds by manipulation of culture medium

The generation of aroma compounds by carotenoid cleavage in the 9-10 position was studied, due to the importance of these compounds in the flavor and fragrance industry. The bioconversion of the carotenoid lutein to C(13) norisoprenoids utilizing a microbial mixture composed of Trichosporon asahii and Paenibacillus amylolyticus was carried out by a fermentation process. Applying an experimental design methodology, the effects of nutritional factors on the production of aroma compounds present in the tobacco profile were studied. After an assessment of the significance of each nutritional factor, the levels of the variables yielding the maximum response were calculated. Glucose, tryptone, and yeast extract exerted a strong negative effect over the objective function, with glucose being the strongest. Lutein possessed a positive effect over the tobacco aroma production, while sodium chloride and trace elements showed no influence over the process. The yield attained after culture medium manipulation was almost ten-fold higher, compared with the base medium; and the aroma mixture was characterized as: 7,8-dihydro-beta-ionol (95.2%), 7,8-dihydro-beta-ionone (3.7%), and beta-ionone (1.1%).

Generation of aroma compounds during sourdough fermentation: applied and fundamental aspects

Sourdough has been used in bread production for more than 5000 years in order to improve the texture and flavour of baked cereals, and still today sourdough is very important to impart superior flavours to wheat and particularly rye bread. After an introduction into the history of sourdough, results of studies aimed at indicating (i) the influence of the dough and bread recipe, (ii) the regime used in dough fermentation, and (iii) the metabolic activities of sourdough bacteria and yeasts on the final bread aroma are summarized in this review. Based on quantitative results obtained from the same batch of flour, sourdough and rye bread, changes in the concentrations of key bread aroma compounds on the way from flour to bread are highlighted with respect to their contribution to the overall aroma. Based on correlations with the bread recipe, it is discussed how the flour and each technological step influences the final concentrations of selected odorants in the bread.

Furfural-cysteine model reaction in food grade nonionic oil/water microemulsions for selective flavor formation.

The thermal reaction between cysteine and furfural was investigated at 65 degrees C in five-component food grade oil/water (O/W) microemulsions of R-(+)-limonene/ethanol, EtOH/water/propylene glycol, PG/Tween 60 as apart of a systematic study on the generation of aroma compounds by utilizing structured W/O and O/W fluids. The furfural-cysteine reaction led to the formation of unique aroma compounds such as 2-furfurylthiol (FFT), 2-(2-furanyl)thiazolidine (main reaction product), 2-(2-furanyl)thiazoline, and N-(2-mercaptovinyl)-2-(2-furanyl)thiazolidine. These products were determined and characterized by GC-MS. Enhancement in flavor formation is termed "microemulsion catalysis". The chemical reaction occurs preferably at the interfacial film, and therefore a pseudophase model was assumed to explain the enhanced flavor formation. The product internal composition is dictated by process conditions such as temperature, time, pH, and mainly the nature of the interface. Increasing water/PG ratio leads to a dramatic increase in the initial reaction rate (V(0)). V(0) increased linearly as a function of the aqueous phase content, which could be due to the increase in the interfacial concentration of furfural. Microemulsions offer a new reaction medium to produce selective aroma compounds and to optimize their formation.

Sucrose ester microemulsions as microreactors for model Maillard reaction

Thermal reactions of cysteine/furfural mixture were studied as a model system to gain more insight into the influence of structured fluids such as water-in-oil nonionic microemulsions on the generation of aroma compounds. The microemulsion systems were composed of: sucrose ester/water/dodecane+alcohol(1/1), where the sucrose esters are sucrose stearate (S1570) and sucrose laurate (L1695), and the alcohols are medium-chain alcohols (C 2OH to C 6OH). Formation of predominately 2-furfurylthiol (FFT) is obtained in the aqueous cysteine/furfural system. The formation of FFT was enhanced under similar reaction conditions in water-in-oil microemulsions and led to the formation of two new sulfur compounds that were identified as 2-(2-furyl)-thiazolidine and tentatively N-(2-mercaptovinyl)-2-(2-furanyl)-thiazolidine. The reaction rates (furfural conversion or consumption) decrease with the decrease in the water content and the increase in alcohol chain length (C 2 to C 6 were used as cosurfactant) and with the increase of pH from 4 to 8 in the system containing butanol as the alcohol. The rates of reaction increase also with the increase of temperature in the range of temperatures studied from 30 to 60 °C. The kinetic constants ( k) and energy of activation ( E a) were calculated. Microemulsions of W/O are excellent reaction media for the Maillard reaction providing a high selectivity, high conversion rates and specificity.

Structured fluids as microreactors for flavor formation by the Maillard reaction.

Thermal reactions of cysteine/furfural and cysteine/ribose mixtures were studied in model systems to gain more insight into the influence of structured fluids such as L(2) microemulsions and cubic phases on the generation of aroma compounds. Formation of 2-furfurylthiol from cysteine/furfural was particularly efficient in L(2) microemulsions and cubic phases compared to aqueous systems. The reaction led to the formation of two new sulfur compounds, which were identified as 2-(2-furyl)thiazolidine and, tentatively, N-(2-mercaptovinyl)-2-(2-furyl)thiazolidine. Similarly, generation of 2-furfurylthiol and 2-methyl-3-furanthiol from cysteine/ribose mixtures was strongly enhanced in structured fluids. The cubic phase was shown to be even more efficient in flavor generation than the L(2) microemulsion. It was denoted "cubic catalyst" or "cubic selective microreactor". The obtained results are interpreted in terms of a surface and curvature control of the reactions defined by the structural properties of the formed surfactant associates.