Fruity Odor Research Articles

Characteristics of lactic acid bacteria and acetic acid bacteria isolated before and after fermentation of cacao beans from Pidie, Indonesia and detection of the flavour compounds

The objectives of this research were to characterise lactic acid bacteria (LAB) and acetic acid bacteria (AAB) which were isolated before and after fermentation of cacao beans, and to detect the flavor compounds in each of these steps. Samples were collected from a farmer in the Pidie District, Aceh Province, Indonesia who supplies the fermented cacao beans for a local chocolate factory located in Pidie Jaya District. The samples were collected before fermentation (F0) and after 5 days fermentation (F5) steps in duplicate. Five LAB and nine AAB were characterised for colony and cell morphology, catalase and oxidase tests, and growth resistance at low pH. The qualitative analysis of flavor compounds of the cacao beans were identified by Gas Chromatography Mass Spectrometry Solid Phase Microextraction (SPME-GCMS). The results showed that all isolates have a negative result on oxidase tests and only one AAB isolate could grow at pH 3. The reduction of phenethylamine during fermentation is desired because it gives off a fishy odor as a result of decarboxylation of amino acids by lactic acid bacteria. The detection of 3-octanyl acetate by its sweet floral fruity odor is expected. It is also interesting to note that a nutty taste and earthy aroma were detected indicating that trimethyl pyrazine and dimethyl pyrazine were present after fermentation even though they were not a major compound.

Impact of malolactic fermentation with Lactobacillus plantarum on volatile compounds of sea buckthorn juice

Malolactic fermentation using sea buckthorn (Hippophaë rhamnoides) juice as raw material was performed with six different strains of Lactobacillus plantarum. Increasing juice pH from 2.7 to 3.5 or adapting cells to low pH (i.e., acclimation) prior to inoculation allowed malolactic fermentation with all tested strains. Moreover, reducing pH of the growth medium from 6 to 4.5 with l-malate had little or no impact on biomass production. Volatile profile of sea buckthorn juice was analyzed with HS-SPME–GC–MS before and after fermentation. A total of 92 volatiles were tentatively identified and semi-quantified from sea buckthorn juice, majority of which were esters with fruity odor descriptors. Esters and terpenes were decreased in both inoculated and control juices during incubation. Microbial activity increased the levels of acetic acid (vinegar like), free fatty acids (cheese like), ketones (buttery like), and alcohols with fruity descriptors. Conversely, aldehydes associated with “green” aroma were decreased as a result of fermentation. Juices fermented with DSM 1055 had the highest acid and alcohol content, while fermentation with DSM 13273 resulted in the highest content of ketones. Compared to inoculation with other strains, fermentation with strains DSM 16365 and DSM 100813 resulted in rapid malolactic fermentation, less production of volatile acids, and lower loss of esters and terpenes important for natural sea buckthorn flavor.

Microbial and Chemical Analysis of Non-Saccharomyces Yeasts from Chambourcin Hybrid Grapes for Potential Use in Winemaking

Native microorganisms present on grapes can influence final wine quality. Chambourcin is the most abundant hybrid grape grown in Pennsylvania and is more resistant to cold temperatures and fungal diseases compared to Vitis vinifera. Here, non-Saccharomyces yeasts were isolated from spontaneously fermenting Chambourcin must from three regional vineyards. Using cultured-based methods and ITS sequencing, Hanseniaspora and Pichia spp. were the most dominant genus out of 29 fungal species identified. Five strains of Hanseniaspora uvarum, H. opuntiae, Pichia kluyveri, P. kudriavzevii, and Aureobasidium pullulans were characterized for the ability to tolerate sulfite and ethanol. Hanseniaspora opuntiae PSWCC64 and P. kudriavzevii PSWCC102 can tolerate 8–10% ethanol and were able to utilize 60–80% sugars during fermentation. Laboratory scale fermentations of candidate strain into sterile Chambourcin juice allowed for analyzing compounds associated with wine flavor. Nine nonvolatile compounds were conserved in inoculated fermentations. In contrast, Hanseniaspora strains PSWCC64 and PSWCC70 were positively correlated with 2-heptanol and ionone associated to fruity and floral odor and P. kudriazevii PSWCC102 was positively correlated with a group of esters and acetals associated to fruity and herbaceous aroma. Microbial and chemical characterization of non-Saccharomyces yeasts presents an exciting approach to enhance flavor complexity and regionality of hybrid wines.

Effect of the roasting degree on flavor quality of large-leaf yellow tea

Roasting is crucial for producing large-leaf yellow tea (LYT) as it substantially affects chemical composition and sensory quality. However, the effect of roasting degree on LYT flavor quality is not clear. To investigate the effect of roasting degree on LYT flavor, the odor profiles and sensory evaluations of LYTs produced with small fire, medium fire and old fire roasting (OF) were determined. The OF was essential for the formation of LYT flavor with strong roasted, nutty, woody odors and weak fatty, fruity odors, and retaining high levels of GCG, total volatiles and heterocyclic compounds. Furthermore, the characteristic crispy-rice-like odor was only found in LYT with OF treatment and burnt flavor was missing. 2,3-Diethyl-5-methylpyrazine, trans-β-ionone with odor activity value above 1600 and 39 respectively offered roasted, floral odors, respectively in LYT. The current results provide a scientific basis for understanding the reactions that occur during the conventional production of LYT.

Characteristics of Volatile Compounds and Sensory Properties of Mixed Organic Juices Based on Kiwiberry Fruits

Nowadays, the trend related to healthy eating is constantly growing among consumers. The juices based on kiwiberry containing over 20 vital nutrients may have a potential for usage in developing innovative products targeting health-concerned consumers. The aims of the study were: (1) to identify the volatile compounds of kiwiberry juice and its mixes with basic organic juices; (2) to determine the sensory characteristics and level of liking with regard to the tested samples and (3) to select the juice-mix with the highest sensory quality properties and liking. The measurements of volatile compounds in juices were made using a Heracles Neo ultrafast gas chromatograph (HS-GC). The sensory characteristics of the juices were assessed by Descriptive Quantitative Analysis, whereas the consumers’ overall liking was assessed on a 9-point hedonic scale. It was stated that the examined juices differed in the pattern of volatile compounds as well as in the sensory properties and the level of liking. The increasing addition of apple and pear juice to kiwiberry based juices in different ratios contributed to the exposed volatile compounds responsible for floral, sweet and fruity odours. The juice mixes with higher addition of apple or pear juices were more harmonized in terms of sensory image and represented higher levels of overall liking among consumers.

Identification of Aroma Composition and Key Odorants Contributing to Aroma Characteristics of White Teas.

The identification of aroma composition and key odorants contributing to aroma characteristics of white tea is urgently needed, owing to white tea’s charming flavors and significant health benefits. In this study, a total of 238 volatile components were identified in the three subtypes of white teas using headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOFMS). The multivariate statistical analysis demonstrated that the contents of 103 volatile compounds showed extremely significant differences, of which 44 compounds presented higher contents in Baihaoyinzhen and Baimudan, while the other 59 compounds exhibited higher contents in Shoumei. The sensory evaluation experiment carried out by gas chromatography–olfactometry/mass spectrometry (GC–O/MS) revealed 44 aroma-active compounds, of which 25 compounds were identified, including 9 alcohols, 6 aldehydes, 5 ketones, and 5 other compounds. These odorants mostly presented green, fresh, floral, fruity, or sweet odors. Multivariate analyses of chemical characterization and sensory evaluation results showed that high proportions of alcohols and aldehydes form the basis of green and fresh aroma characteristic of white teas, and phenylethyl alcohol, γ-Nonalactone, trans-β-ionone, trans-linalool oxide (furanoid), α-ionone, and cis-3-hexenyl butyrate were considered as the key odorants accounting for the different aroma characteristics of the three subtypes of white tea. The results will contribute to in-depth understand chemical and sensory markers associated with different subtypes of white tea, and provide a solid foundation for tea aroma quality control and improvement.

Nutritional quality of ensiled gamba grass (Andropogon gayanus) fortified with graded levels of Centro (Centrosema pascourum)

The study was conducted with the field grown gamba grass (Andropogon gayanus) and Centro (Centrosema pascourum) to examine the nutritional quality of gamba grass ensiled with graded levels of Centrosema pascourum. The forages were harvested separately chopped into 2-3cm length manually and mixed thoroughly as follows: (100:0, 90:10, 80:20,70:30, 60:40, 50:50 and 40:60% of Andropogon gayanus: Centrosema pascourum, respectively) and designated as T1 , T2 , T3 , T4 , T5 , T6 and T7 respectively. The treatments were ensiled in a laboratory using bottle silos in triplicates per treatments and kept for 30 days fermentation period. The silages were evaluated for quality characteristics, proximate composition, fibre fractions, volatile fatty acids composition and ammonia nitrogen concentration (NH3 -N) using standard procedure. The results obtained showed that the silages were adequately fermented with pleasant and fruity odour, greenish-yellow colour, firm and dry texture. The pH, ether extract (EE), nitrogen free extract (NFE), organic matter (OM) and Ash contents of the silages were similar across the treatments (P<0.05). However, the crude protein (CP) contents of silages (9.44-14.88%), varied significantly (P<0.05) across the treatments. The crude fibre (CF), cellulose, hemicellulose and fibre fractions (neutral detergent fibre (NDF) and acid detergent fibre (ADF) of the silages differed significantly (P<0.05) except for acid detergent lignin (ADL) which was similar across the treatments. Other parameters such as volatile fatty acids (VFAs), NH3 concentration, temperature (°C) and dry matter (DM) moisture content (MC) differed significantly across the board. The results of this study indicated that ensiled Andropogon gayanus with Centrosema pascourum at varied levels of inclusion improved physico chemical properties of the silages. The inclusion of Centrosema pascourum legume forage also improved the crude protein (CP) contents of ensiled gamba grass significantly. Thus, the study recommends the use of 60% Andropogon gayanus and 40% Centrosema pascourum, which is practicable and obtainable.

볶음쌀을 첨가한 메주 사용이 간장의 품질에 미치는 영향

This study examined the quality characteristics of ‘Ganjang’ prepared with ‘Meju’ containing roasted rice additives (0%, 10%, 30%, 50%) for improving the flavor of traditional ‘Ganjang’. The differences between the flavor-enhanced ‘Ganjang’ and their traditional counterparts were also analyzed. The total nitrogen and amino acid nitrogen contents of the ‘Ganjang’ prepared using ‘Meju’ containing roasted rice additives decreased with increasing amount of roasted rice additives. Reducing sugar content was the highest in ‘Ganjang’ in which 30% roasted rice was added to ‘Meju’ Analysis of the free amino acids in ‘Ganjang’ showed that contents of the amino acids with a bitter tastes during ‘Ganjang’ production decreased upon the addition of roasted rice; among the amino acids with a sweet taste, threonine content was high, and the glutamic acid content with a savory taste was similar. Additionally, E-nose and E-tongue analyses showed that there were differences between ‘Ganjang’ prepared using ‘Meju’ with roasted rice additives and the existing ‘Ganjang’. E-nose analysis suggested that such differences originated due to the fruity odors of ethyl acetate and tert-butyl acetate and the roasting odor of pyrazine in ‘Ganjang’ with roasted rice additives. E-tongue analysis exhibited high SWS sensor values, which responds to sweetness. Therefore, this study confirmed the use of roasted rice for taste improvement, which increased the sweet tastes and, fruity and roasting odors during the production of traditional ‘Ganjang’.

Synthesis of 1,4‐Cyclohexadiene Carboxylates through a Formal [2+4]‐Cycloaddition of Propiolates under Cobalt Catalysis

AbstractA low‐valent cobalt(I) complex, formed from the reduction of CoBr2(dppe) with zinc, acts as catalyst for the efficient [2+4] cycloaddition of β‐alkyl, cycloalkyl and aryl substituted propiolates to dienes. This transformation yields synthetically relevant 1,4‐cyclohexadiene carboxylates in good to excellent yields. Furthermore, the target compounds are novel lead structures for the discovery of fragrance ingredients from the fruity, floral and spicy odor family.

Comparative evaluation of volatile profile of tomato subjected to hot air, freeze, and spray drying

Tomato (Lycopersicon esculentum Mill.) is an important vegetable crop cherished all over the world for consumption as a raw vegetable or as processed products. They are subjected to various drying processes to increase product stability and decrease postharvest loss. However, this can cause a loss in volatile compounds due to process conditions. Present study aims to gain an insight into the volatile profile of tomatoes when subjected to hot air, freeze, and spray drying processes. In this regard, the analysis of headspace - solid phase microextraction (HS-SPME) in conjunction with gas chromatography–mass spectroscopy (GC–MS) revealed that the volatile profile, namely compounds belonging to aldehydes, alcohols, terpenes, ketones, and furans varied greatly between the fresh and dehydrated tomatoes. The aroma of dehydrated tomato products that retained volatiles followed the following order: freeze-drying >/≥spray drying > hot air drying. An increase in contents of compounds such as dimethyl sulfide, 2-ethyl furan, hydroxymethyl furfural, acetaldehyde, and α-terpineol was found in all dehydrated products. Interestingly, compounds such as 3-methyl furan, hexanol and terpinyl acetate were found to occur only in dehydrated products. The presence of γ-undecalactone (fruity odor note) is identified for the first time in our study in fresh and all dehydrated tomatoes. From the results obtained and with chemometric analysis as principal component analysis and hierarchical cluster analysis on the volatile profile, it could be concluded that dehydrated tomatoes serve suitable products that could be extensively commercialized world-wide to achieve overall consumer acceptability.

Characterization of key odor-active compounds in commercial high-salt liquid-state soy sauce by switchable GC/GC × GC–olfactometry–MS and sensory evaluation

Activity of odor compounds of soy sauces has not been fully determined so far. Herein, a new switchable GC/GC × GC–olfactometry–mass spectrometry system for simultaneous GC × GC–MS analysis and sniffing of each odor-active substance through a single injection was used for the aroma extract dilution analysis of five regular high-salt liquid-state soy sauces (HLS). Methional, maltol, guaiacol, 4-ethylguaiacol, 2-acetylpyrrole, 2-acetylfuran, 2-phenylethanol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone showed high flavor dilution (FD) factors. The FD factors of all odor-active compounds in different odor attributes were summed up (score) to evaluate the odor characteristics of the samples. Cooked potato-like odor was the most important characteristic. The difference in the odor characteristics were mainly reflected in the balance of caramel-like/sweet, roasted/roasted nut-like, spicy/burnt, and unpleasant odor intensity; the fruity odor intensity was the weakest. This study will provide a better understanding of the odor characteristics and key odor-active compounds in Chinese regular commercial HLS.

Discrimination and Identification of Aroma Profiles and Characterized Odorants in Citrus Blend Black Tea with Different Citrus Species

Citrus blend black teas are popular worldwide, due to its unique flavor and remarkable health benefits. However, the aroma characteristics, aroma profiles and key odorants of it remain to be distinguished and cognized. In this study, the aroma profiles of 12 representative samples with three different cultivars including citrus (Citrus reticulata), bergamot (Citrus bergamia), and lemon (Citrus limon) were determined by a novel approach combined head space-solid phase microextraction (HS-SPME) with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). A total of 348 volatile compounds, among which comprised esters (60), alkenes (55), aldehydes (45), ketones (45), alcohols (37), aromatic hydrocarbons (20), and some others were ultimately identified. The further partial least squares discrimination analysis (PLS-DA) certified obvious differences existed among the three groups with a screening result of 30 significant differential key volatile compounds. A total of 61 aroma-active compounds that mostly presented green, fresh, fruity, and sweet odors were determined in three groups with gas chromatography-olfactometry/mass spectrometry (GC-O/MS) assisted analysis. Heptanal, limonene, linalool, and trans-β-ionone were considered the fundamental odorants associated with the flavors of these teas. Comprehensive analysis showed that limonene, ethyl octanoate, copaene, ethyl butyrate (citrus), benzyl acetate, nerol (bergamot) and furfural (lemon) were determined as the characterized odorants for each type.

Non‐invasive Measurement of Blood Glucose by Breath Analysis

The determination of blood glucose is usually performed in the laboratory or using invasive glucose meters. Unusual, fruity, or bad breath odor can be a sign of metabolic disease. The objective is the estimation of the blood glucose by breath analysis. To do that, we designed a three‐gas prediction model (alcohol, acetone, and propane). We exhaled in front of the three gas sensors and then recorded the concentrations of the three volatile organic compounds (VOCs) in a database. This database included the measurements of 200 volunteer people. We then systematically studied the correlation between the glucose level obtained by blood analysis and each of these three gases. We also studied the different possible combinations of two and three gases. The best correlation was obtained for the non‐diabetic subjects with a correlation coefficient (r = 0.97), for the diabetic subjects (r = 0.35). We implemented these two linear regressions and we used the validation set to estimate the accuracy of the prototype. For the non‐diabetic subjects, the relative error of the measurement of the glycemia was equal to 3.93%. For the diabetic subjects, the error = 13.42%. The results have shown that the determination of glycemia by breath analysis can become a serious alternative. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

What's Hot, What's Not: The Trends of the Past 20 Years in the Chemistry of Odorants

This review is the sequel to the 2000 report on the recent advances in the chemistry of odorants and it summarizes the developments in fragrance chemistry over the past 20 years. Following the olfactory spectrum set out in that report, trendsetting so-called captive odorants (patent-protected ingredients unavailable to the market) are presented according to the main odor families: "fruity", "marine", "green", "floral", "spicy", "woody", "amber", and "musky". The design of odorants, their chemical synthesis, and their use in modern perfumery are illustrated with prominent examples. Featured are new fruity odorants that provide signature in the top note, as well as precursor technology. In the green domain, focus is on leafy notes and green pear. New benzodioxepines and benzodioxoles have modernized the marine family and required a revision of the existing olfactophore models. The replacement of Lilial and Lyral kept the industry busy in the floral domain with a plethora of new "muguets". There was continued activity in the domain of rose odorants, especially in the area of rose ketones. Biotechnology became significant, for example, with Clearwood and Ambrofix, and the principal odorants of vetiver oil in the woody family have been found. Fourth and fifth families of musk odorants were also discovered and populated. Thus, new avenues for further explorations into fragrance chemistry have been opened.

Study of kefir drinks produced by backslopping method using kefir grains from Bosnia and Herzegovina: Microbial dynamics and volatilome profile

Kefir is a well-known health-promoting beverage that can be produced by using kefir grains (traditional method) or by using natural starter cultures from kefir (backslopping method). The aim of this study was to elucidate the microbial dynamics and volatilome profile occurring during kefir production through traditional and backslopping methods by using five kefir grains that were collected in Bosnia and Herzegovina. The results from conventional pour plating techniques and amplicon-based sequencing were combined. The kefir drinks have also been characterized in terms of their physico-chemical and colorimetric parameters. A bacterial shift from Lactobacillus kefiranofaciens to Acetobacter syzygii, Lactococcus lactis and Leuconostoc pseudomesenteroides from kefir grains in traditional kefir to backslopped kefir was generally observed. Despite some differences within samples, the dominant mycobiota of backslopped kefir samples remained quite similar to that of the kefir grain samples. However, unlike the lactic acid and acetic acid bacteria, the yeast counts decreased progressively from the grains to the backslopped kefir. The backslopped kefir samples showed higher protein, lactose and ash content and lower ethanol content compared to traditional kefir samples, coupled with optimal pH values that contribute to a pleasant sensory profile. Concerning the volatilome, backslopped kefir samples were correlated with cheesy, buttery, floral and fermented odors, whereas the traditional kefir samples were correlated with alcoholic, fruity, fatty and acid odors. Overall, the data obtained in the present study provided evidence that different kefir production methods (traditional vs backslopping) affect the quality characteristics of the final product. Hence, the functional traits of backslopped kefir should be further investigated in order to verify the suitability of a potential scale-up methodology for backslopping.

Effect of copy number of the spoVA2mob operon, sourdough and reutericyclin on ropy bread spoilage caused by Bacillus spp.

Bacillus spp. cause ropy bread spoilage of bread, which is characterized by a rotten fruity odor, followed by discoloration and degradation of the crumb. Bacillus spp. are wheat grain endophytes and form heat resistant endospores, therefore, process hygiene and heating during baking do not prevent ropy spoilage. This study used 8 strains of Bacillus subtilis and Bacillus amyloliquefaciens to determine whether the presence and the copy number of spoVA2mob operon influences survival after baking; in addition, the spoilage phenotype was correlated with the presence of amylolytic enzymes in genomes of Bacillus spp.. The presence and copy number of the spoVA2mob operon had only a minor effect on survival of Bacillus endospores. Strains of B. amyloliquefaciens caused ropy spoilage faster than strains of B. subtilis, this difference correlated to the number and type of extracellular amylases encoded in the genomes of the strains of B. amyloliquefaciens and B. subtilis. The inhibitory effect of sourdough on ropy spoilage was determined by addition of 3–24% sourdough fermented with L. reuteri TMW1.656. Addition of 12% and 24% sourdough, corresponding to a bread pH of 5.93 ± 0.041 and 5.53 ± 0.040, respectively, delayed ropy spoilage for 2 and more than 5 d, respectively. The comparison of addition of 12% sourdough fermented with the reutericyclin producing L. reuteri TMW1.656 and the isogenic reutericyclin-negative strain L. reuteri TMW1.656ΔgtfAΔrtcN demonstrated that reutericyclin produced in sourdough inhibits growth of Bacillus in bread. In conclusion, sourdough inhibits germination of Bacillus spores in bread and the effect of sourdough is enhanced by reutericyclin.

Quality characteristics and chemical evaluation of Chemlali olive oil produced under dairy wastewater irrigation

The present work aimed to study the effect of using Treated Wastewater (TWW) to irrigate Chemlali olive trees on the quality characteristics and chemical composition of olive oils. This research was conducted in orchards cultivated in the center of Tunisia where olive trees were subjected to different irrigation treatments during two consecutive years; (CT) 0 % ETc, (T1) 20 % ETc and (T2) 40 % ETc. Results showed that irrigation with TWW whatever the level didn’t significantly affect oil standard quality indices (free acidity, K232, K270 and peroxide value) and pigment contents. Furthermore, α-tocopherol amount was maintained stable which may explain the preservation of fatty acids against oxidation after TWW irrigation. Moreover, this last did not induce phenolic compounds contents variation. A decrease of some volatile compounds giving oil undesirable attributes (octanal and acetic acid) and a maintain of those offering good characteristics like the fruity odor were observed.

Changes in the volatile profile of ‘Fantasia’ nectarines [Prunus persica (L.) Batsch, var. nectarina] treated with an enhanced freshness formulation (EFF) containing hexanal

Postharvest technologies play a key role in enhancing shelf life and maintaining quality characteristics of tender fruits, such as nectarines (Prunus persica [L.] Batsch var. nectarina). This research investigated the effects of an enhanced freshness formulation (EFF), containing hexanal as the key ingredient, in enhancing the shelf life of field grown nectarines and its effects on the composition of volatile organic compounds (VOCs). ‘Fantasia’ nectarine fruits at two commercial orchards in the Niagara region were subject to preharvest sprays of 2% EFF (15 and 7 days preharvest) and stored at ambient conditions (25 °C) with volatile analyses conducted at 0, 3, 5, 7, and 11 days postharvest. The volatile analysis study indicated for the first time that hexanal is naturally present in nectarine fruit. This was confirmed by GC–MS analysis and validated with standards. GC–EIMS analyses of targeted VOCs validated with standards indicated reduced levels of VOCs associated with fruit ripening and fruity odor, such as lactones, in hexanal-treated fruit, and an increased level of C6 compounds associated with unripe fruit. Principal component analysis biplot with scores and loadings of the fruit VOCs and quality parameters indicated a tight association between TSS and lactones, which was inversely associated with firmness, ground color, acetates, and ester compounds. Pearson correlation coefficients also indicated a very high positive correlation between hexanal and levels of VOCs, such as 1-hexanol, E-2-hexanal, 3-hexanal, hexen-1-ol, and other C6 acetates. These findings may indicate a delay in the ripening process caused by hexanal formulation, which may be associated with modulated expression of key ripening-related volatile pathways, therefore enhancing the shelf life and quality of nectarines.

Effect of fermentation temperature on volatile compounds of Petit Verdot red wines from the Spanish region of La Mancha (central-southeastern Spain)

The aim of this work was to research the relationship between volatile composition of Petit Verdot red wines and the fermentation temperature. Winemaking process was carried out at 17 °C, 21 °C, and 25 °C temperatures. Solid-phase extraction (SPE) and gas chromatography–mass spectrometry (GC–MS) were used to analyse volatile compounds. The odour activity values (OAVs) from the different compounds were classified into seven odorant series that describe the aroma profile (fruity, floral, green/fresh, sweet, spicy, fatty, and other odours). The value of each aromatic series was obtained by adding the OAVs of the volatile compounds to each series. The volatile composition was significantly affected by the temperature of the fermentation. In general, the increase in the fermentation temperature of La Mancha Petit Verdot red wines from 17 to 25 °C produced an increase in the concentration of volatile aroma compounds. The highest aroma contributions to Petit Verdot wine were fruity, sweet and floral series, followed by fatty and spicy series, regardless of fermentation temperature. The highest values of aromatic series were found in wines fermented at 21 °C. The results of this work show that changes in the fermentation temperature of wines can have a significant impact on their volatile compound profile.

Co-fermentation Involving Saccharomyces cerevisiae and Lactobacillus Species Tolerant to Brewing-Related Stress Factors for Controlled and Rapid Production of Sour Beer.

Increasing popularity of sour beer urges the development of novel solutions for controlled fermentations both for fast acidification and consistency in product flavor and quality. One possible approach is the use of Saccharomyces cerevisiae in co-fermentation with Lactobacillus species, which produce lactic acid as a major end-product of carbohydrate catabolism. The ability of lactobacilli to ferment beer is determined by their capacity to sustain brewing-related stresses, including hop iso-α acids, low pH and ethanol. Here, we evaluated the tolerance of Lactobacillus brevis BSO464 and Lactobacillus buchneri CD034 to beer conditions and different fermentation strategies as well as their use in the brewing process in mixed fermentation with a brewer’s yeast, S. cerevisiae US-05. Results were compared with those obtained with a commercial Lactobacillus plantarum (WildBrewTM Sour Pitch), a strain commonly used for kettle souring. In pure cultures, the three strains showed varying susceptibility to stresses, with L. brevis being the most resistant and L. plantarum displaying the lowest stress tolerance. When in co-fermentation with S. cerevisiae, both L. plantarum and L. brevis were able to generate sour beer in as little as 21 days, and their presence positively influenced the composition of flavor-active compounds. Both sour beers were sensorially different from each other and from a reference beer fermented by S. cerevisiae alone. While the beer produced with L. plantarum had an increased intensity in fruity odor and dried fruit odor, the L. brevis beer had a higher total flavor intensity, acidic taste and astringency. Remarkably, the beer generated with L. brevis was perceived as comparable to a commercial sour beer in multiple sensory attributes. Taken together, this study demonstrates the feasibility of using L. brevis BSO464 and L. plantarum in co-fermentation with S. cerevisiae for controlled sour beer production with shortened production time.