Fermentation Aroma Research Articles

Prediction of the production kinetics of the main fermentative aromas in winemaking fermentations

A novel dynamic model was developed for predicting the synthesis kinetics of the principal aroma compounds produced by yeasts during winemaking fermentations: isobutanol, isoamyl alcohol, isoamyl acetate, ethyl hexanoate and ethyl octanoate. The parameters of the model were identified from nine fermentations performed at temperatures between 18 and 30°C and with different initial nitrogen contents, in the range of 70 to 410mgN/L. The model was validated in six independent experiments with conditions in the same range. Predictions were accurate for these volatile compounds: the mean difference between experimental and estimated values for fermentative aroma synthesis throughout the process was below 10%, for both the fermentations used to build the model and those used for validation. This model is the first to simulate the production kinetics of fermentative aromas and provides new insight into the synthesis of these volatile compounds. It will facilitate the development of innovative strategies for controlling the production of those aromas in winemaking, through management of the principal control factors: assimilable nitrogen content and temperature during the alcoholic fermentation.

A comparative study of the volatile content of Mencía wines obtained using different pre-fermentative maceration techniques

The effects of five pre-fermentative maceration processes (enzymes, refrigerated maceration during 3 and 6 days and cryo-maceration during 3 and 6 days) on volatile composition of Mencía red wines were studied. This study was carried out during three consecutive vintages, and semi-industrial scale effect was also assayed during third one.Cluster analysis revealed that the different pre-fermentative maceration techniques tested led to wines with different volatile composition. Forward stepwise discriminate analysis selected 22 volatiles, mainly corresponding to fermentative compounds showing that the effects of pre-fermentative maceration techniques are mainly related to effects on fermentative aroma precursors. Generally, macerated Mencía wines were richer on alcohols and ethyl vanillate, but poorer on some of the ethyl esters under study. However, the effects of the techniques are quantitatively and qualitatively different, allowing the possibility of obtaining wines specifically adapted to the consumers' taste or wines personalised according to the enologists' preferences.

Minor Volatile Compounds Profiles of ‘Aligoté’ Wines Fermented with Different Yeast Strains

The aroma of wine can be classified accordingly to its origin, in varietal aroma, pre-fermentative aroma, fermentative aroma and post-fermentative aroma. Although a number of flavor components are found in the original grape, the dominant and major compounds contributing to white wines are formed during alcoholic fermentation, in concordance with the yeast strain used. In order to highlight the influence of the yeast strain to the aroma composition of wines, wine samples from ‘Aligoté’ grape variety made with 8 different yeast strains were subjected to stir bar sorptive extraction-gas chromatography-mass spectrometry (SBSE-GC-MS) analyses. Also, a sensorial analysis of the studied wines was performed by a tasting panel consisting of 15 tasters. 38 minor volatile compounds were quantified by SBSE-GC-MS technique. Different concentration of the same compound and different aroma compounds were identified and quantified in wines obtained with different yeast strains. A wine finger printing was obtained by multivariate data analyses of aroma compounds grouped by chemical families. The analytical and sensorial analysis of the wine samples confirms that there are differences in aroma composition of the wines made with different yeast strains.

Combined effects of nutrients and temperature on the production of fermentative aromas by Saccharomyces cerevisiae during wine fermentation.

Volatile compounds produced by yeast during fermentation greatly influence the organoleptic qualities of wine. We developed a model to predict the combined effects of initial nitrogen and phytosterol content and fermentation temperature on the production of volatile compounds. We used a Box-Behnken design and response surface modeling to study the response of Lalvin EC1118® to these environmental conditions. Initial nitrogen content had the greatest influence on most compounds; however, there were differences in the value of fermentation parameters required for the maximal production of the various compounds. Fermentation parameters affected differently the production of isobutanol and isoamyl alcohol, although their synthesis involve the same enzymes and intermediate. We found differences in regulation of the synthesis of acetates of higher alcohols and ethyl esters, suggesting that fatty acid availability is the main factor influencing the synthesis of ethyl esters whereas the production of acetates depends on the activity of alcohol acetyltransferases. We also evaluated the effect of temperature on the total production of three esters by determining gas-liquid balances. Evaporation largely accounted for the effect of temperature on the accumulation of esters in liquid. Nonetheless, the metabolism of isoamyl acetate and ethyl octanoate was significantly affected by this parameter. We extended this study to other strains. Environmental parameters had a similar effect on aroma production in most strains. Nevertheless, the regulation of the synthesis of fermentative aromas was atypical in two strains: Lalvin K1M® and Affinity™ ECA5, which produces a high amount of aromatic compounds and was obtained by experimental evolution.

Dynamics and quantitative analysis of the synthesis of fermentative aromas by an evolved wine strain of Saccharomyces cerevisiae.

We performed a dynamic and quantitative analysis of the synthesis of fermentative aromas by an aromatic wine yeast, ECA5, obtained by adaptive evolution. During fermentation at pilot scale on synthetic and natural musts, ECA5 produced volatile compounds (higher alcohols and their acetates, ethyl esters) at higher rates than the ancestral strain, with the exception of propanol. Marked differences in the chronology of synthesis of several compounds were observed between the two strains. Overproduction of phenyl ethanol occurred mainly during the growth phase for ECA5, consistent with its higher flux through the pentose phosphate pathway, which plays a key role in biosynthetic processes. The kinetics of production of isobutanol and isoamyl alcohol were differently affected by different media (synthetic or natural must) and, in particular, according to the nature of the sterols in the media (ergosterol or phytosterols). We also observed differences in the chronology of synthesis of ethyl acetate and isoamyl acetate or ethyl esters, suggesting that the regulation of the synthesis of these compounds in the evolved strain differs from that in the ancestral strain. This study shows that a dynamic analysis of volatile compounds, using high acquisition frequency online gas chromatography, can provide novel insights into the synthesis and regulation of aromas and is thus a potentially powerful tool for strain characterization.

Isolation, selection and evaluation of yeasts for use in fermentation of coffee beans by the wet process

During wet processing of coffee, the ripe cherries are pulped, then fermented and dried. This study reports an experimental approach for target identification and selection of indigenous coffee yeasts and their potential use as starter cultures during the fermentation step of wet processing. A total of 144 yeast isolates originating from spontaneously fermenting coffee beans were identified by molecular approaches and screened for their capacity to grow under coffee-associated stress conditions. According to ITS-rRNA gene sequencing, Pichia fermentans and Pichia kluyveri were the most frequent isolates, followed by Candida Candida glabrata, quercitrusa, Saccharomyces sp., Pichia guilliermondii, Pichia caribbica and Hanseniaspora opuntiae. Nine stress-tolerant yeast strains were evaluated for their ability to produce aromatic compounds in a coffee pulp simulation medium and for their pectinolytic activity. P. fermentans YC5.2 produced the highest concentrations of flavor-active ester compounds (viz., ethyl acetate and isoamyl acetate), while Saccharomyces sp. YC9.15 was the best pectinase-producing strain. The potential impact of these selected yeast strains to promote flavor development in coffee beverages was investigated for inoculating coffee beans during wet fermentation trials at laboratory scale. Inoculation of a single culture of P. fermentans YC5.2 and co-culture of P. fermentans YC5.2 and Saccharomyces sp. YC9.15 enhanced significantly the formation of volatile aroma compounds during the fermentation process compared to un-inoculated control. The sensory analysis indicated that the flavor of coffee beverages was influenced by the starter cultures, being rated as having the higher sensory scores for fruity, buttery and fermented aroma. This demonstrates a complementary role of yeasts associated with coffee quality through the synthesis of yeast-specific volatile constituents. The yeast strains P. fermentans YC5.2 and Saccharomyces sp. YC9.15 have a great potential for use as starter cultures in wet processing of coffee and may possibly help to control and standardize the fermentation process and produce coffee beverages with novel and desirable flavor profiles.

Production of folate in oat bran fermentation by yeasts isolated from barley and diverse foods.

The focus of the research was to identify yeasts from barley kernels in order to study their folate production capability while maintaining high viscosity caused by soluble fibres in oat bran fermentation. The 65 isolated yeasts were characterized by API carbohydrate utilization tests, and assays for extracellular enzyme activities were the following: amylase, beta-glucanase, cellulase or CMCase, lipase, protease and xylanase. Yeasts were identified by partial DNA sequencing of the 25S D1/D2 and ITS1-5.8S-ITS2 regions. They belonged to the genera Aureobasidium, Cryptococcus, Pseudozyma and Rhodotorula. Folate production was determined from supernatant and cells grown in a rich laboratory medium or directly from oat bran solution inoculated with the appropriate yeast. Food yeasts, Saccharomyces cerevisiae, Candida milleri, Kluyveromyces marxianus and Galactomyces geotrichum, were used for comparison. Most of the yeasts isolated from barley destroyed the solid, viscous structure of the oat bran solution, indicating that they degraded the viscosity-generating soluble fibres, considered to be nutritionally advantageous. The best folate producers were S. cerevisiae, followed by Pseudozyma sp., Rhodotorula glutinis and K. marxianus. The yeasts maintaining high viscosity were used together with lactic acid bacteria (LAB) Streptococcus thermophilus or Lactobacillus rhamnosus to ferment oat bran solution. None of the yeasts isolated from barley, contrary to S. cerevisiae and C. milleri, produced together with LAB significant amounts of folate. Fermentative yeasts together with LAB are potential for use in developing novel high folate content healthy foods and snacks from oat bran. High soluble fibre content and high natural folate content but low energy content food and snack products with pleasant fermentation aroma provide possibilities for new developments in the food industry.

Kinetic analysis and gas–liquid balances of the production of fermentative aromas during winemaking fermentations: Effect of assimilable nitrogen and temperature

The impact of temperature and assimilable nitrogen on synthesis of the principal fermentative aromas by yeasts was evaluated with an online GC system. Kinetic parameters and gas–liquid balances were precisely calculated, making it possible to differentiate between the biological and physical consequences of temperature shifts. The lower liquid concentrations of esters at high temperature resulted mostly from large losses by evaporation, with only limited changes in yeast metabolism. Nitrogen availability was the main fermentation parameter affecting the kinetics of higher alcohol and ester synthesis, but the magnitude of this effect depended on temperature. The production of fermentative aromas was closely linked to central carbon metabolism, except for propanol. Indeed, two successive linear production phases (with yields dependent on initial nitrogen content and temperature) were obtained when volatile compound synthesis was plotted against sugar consumption. Overall and specific rates of isobutanol and isoamyl alcohol production were affected differently by nitrogen and temperature, indicating major differences in the regulation of synthesis for these two compounds, despite their partially shared metabolic pathways. Finally, propanol was produced exclusively during the nitrogen consumption phase, and the amount produced increased with initial nitrogen concentration. This compound was, therefore, identified as a quantitative, metabolic marker of the availability of intracellular nitrogen.

Quality characterization of wheat, maize and sorghum steamed breads from Lesotho

In Lesotho, traditional bread covers different types of dumplings prepared with cereal flour, water, salt and sourdough. This study characterized eight steamed breads prepared from wheat, maize and sorghum. Breads were prepared from both commercial and self-milled flours according to the procedures followed in rural and urban areas of Lesotho. Descriptive sensory evaluation was conducted to profile sensory properties of the breads. Flour particle sizes, sourdough properties and bread colour, volume and texture were also characterized. The type of cereal and milling properties of the flour used had substantial effects on the physical and sensory properties of the bread. Steamed wheat breads had greater volume, softer crumb and more bland flavour compared with sorghum and maize breads. Both sorghum and maize steamed breads prepared according to traditional Basotho procedures were characterized by low loaf volume, denser crumb, more complex and strong flavours and aroma, notably sour, musty, malty, dairy sour and fermented aroma. The texture of the non-wheat bread types was heavy, chewy, dry, fibrous and more brittle and needed a higher compression force to deform. This study provided insight on the sensory properties of steamed bread as prepared in Lesotho. Further research is needed to optimize sensory properties of the non-wheat steamed breads by controlling the flour particle size, compositing non-wheat flours with different levels of wheat flour, addition of protein sources and gums, altering the amount of water, improving the pre-gelatinization process and optimizing the steaming method of cooking bread.

Modulation of chemical and sensory characteristics of red wine from Mencía by using indigenous <em>Saccharomyces cerevisiae</em> yeast strains

<p style="text-align: justify;"><strong>Aim</strong>: To evaluate the influence of native <em>Saccharomyces cerevisiae </em>strains in red wines from <em>Vitis vinifera</em> cv. Mencía: fermentative ability, inoculation success, and sensory and chemical characteristics of wines.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Indigenous yeast strains (Sc5, Sc11, Sc21 and Sc24) were inoculated in grape musts and their inoculation success was followed by mtDNA-RFLP (mitochondrial DNA-restriction fragment length polymorphism) at different stages of fermentation. The results showed that the added yeast strains fermented in co-dominance with a resident strain, which also controlled the spontaneous processes. Chemical analysis of basic wine parameters using official methodologies showed significant differences among wines for alcohol degree and volatile acidity. Fermentative aroma compounds were determined by gas chromatography. Wines made with different yeast strains varied in higher alcohols, ethyl ester, 2-phenylethanol, ethyl lactate and acetoin content. Sensory analysis indicated that wine from strain Sc24 had the best overall score, whereas that from strain Sc11 achieved the highest scores for colour intensity, structure and fruity character.</p><p style="text-align: justify;"><strong>Conclusions</strong>: The application of selected <em>S. cerevisiae</em> strains allowed us to obtain differentiated wines from both the chemical and sensory points of view.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The results confirmed that indigenous yeasts can be used to elaborate singular wines and may constitute a useful tool to diversify Mencía wines.</p>

Sensory evaluation and consumer acceptance of naturally and lactic acid bacteria-fermented pastes of soybeans and soybean-maize blends.

Fermented pastes of soybeans and soybean–maize blends were evaluated to determine sensory properties driving consumer liking. Pastes composed of 100% soybeans, 90% soybeans and 10% maize, and 75% soybeans and 25% maize were naturally fermented (NFP), and lactic acid bacteria fermented (LFP). Lactic acid bacteria fermentation was achieved through backslopping using a fermented cereal gruel, thobwa. Ten trained panelists evaluated intensities of 34 descriptors, of which 27 were significantly different (P < 0.05). The LFP were strong in brown color, sourness, umami, roasted soybean-and maize-associated aromas, and sogginess while NFP had high intensities of yellow color, pH, raw soybean, and rancid odors, fried egg, and fermented aromas and softness. Although there was consumer (n = 150) heterogeneity in preference, external preference mapping showed that most consumers preferred NFP. Drivers of liking of NFP samples were softness, pH, fermented aroma, sweetness, fried egg aroma, fried egg-like appearance, raw soybean, and rancid odors. Optimization of the desirable properties of the pastes would increase utilization and acceptance of fermented soybeans.

Fining white wine with plant proteins: effects of fining on proanthocyanidins and aroma components

Plant-derived insoluble proteins (wheat gluten, and isolates from pea, lentil, and soybean) were used as fining agents in model white wine (made from Catalanesca grapes) after cold stabilization. Plant proteins were effective in giving a fast and remarkable decrease in turbidity. GC/MS and HPLC/MS approaches indicated that individual proteins had a different impact on the levels of compounds relevant to wine stability. Protein stability of wine was not affected by fining with plant proteins. Lentil proteins and gluten gave the best removal of monomeric and dimeric flavonol. Both caused a decrease in the total content of fermentative aroma compounds, such as ethyl esters, acetate esters, and alcohols. Lentil proteins had the highest impact on the aroma components, giving a marked decrease in aroma components. Gluten may thus be regarded as giving the best balance between fining efficacy and retention of aroma compounds. Also, gluten in the treated wines remained well below the suggested threshold for gluten-free foods. This study provides a methodological frame for thorough characterization of the impact of specific interventions on key wine components.

Fermentative aroma compounds and sensory profiles of Godello and Albariño wines as influenced by Saccharomyces cerevisiae yeast strains

Yeasts responsible for fermentation have an important repercussion on wine quality. This study presents the influence of two autochthonous strains of Saccharomyces cerevisiae (XG1 and XG3), a commercial yeast (QA23) and spontaneous fermentation on the chemical and sensory properties of wines from Godello and Albariño. All the yeasts showed normal fermentative kinetics and were able to lead fermentations; therefore, they were responsible for wine chemical and sensory characteristics. Significant differences were found at the chemical level depending on yeast strain and variety. Albariño wines from XG1 and XG3 presented low total acidity and glycerol content. Godello wines from QA23 had higher total acidity but lower alcohol content than those from XG1, XG3 and spontaneous fermentation. QA23 wines presented a greater amount of higher alcohols and 2-phenylethanol for both grapevine cultivars, whereas XG3 and spontaneous fermentations yielded wines with a higher concentration of esters, mainly ethyl lactate, and fatty acids. These differences were detected at the sensory level; thus, Albariño made with XG3 and Godello from spontaneous fermentation were the most appreciated wines. XG3, an autochthonous strain of S. cerevisiae, constitutes a useful tool to elaborate wines with singular characteristics.

Modulating the Formation of Meili Wine Aroma by Prefermentative Freezing Process

The influence of a prefermentative freezing process on changes of aromatic characteristics and volatile compounds in Meili wines was studied to optimize freezing parameters and reveal the mathematical relationship between aromatic characteristics and volatile compounds. The wines obtained were characterized by sensory evaluation and stir bar sorptive extraction (SBSE) followed by a thermal desorption-gas chromatography-mass spectrometry analysis. A total of 28 aromatic descriptors from 6 categories of wine aroma terminology were identified by judging with high "modified frequency (MF%)". In addition, 19 varietal aroma compounds and 36 fermentation aroma compounds were quantitated, followed by the determination of odor activity values (OAVs). On the basis of the data obtained, principal component analysis (PCA) was used to find the relationship between characteristic aroma terms and different freezing conditions, and then partial least-squares regression (PLSR) was proposed to establish the mathematical relationship between the resulting terms and impact odorants. Natural thawing treatment on frozen must resulted in higher aroma quality with higher extraction of varietal aroma compounds. Lower frozen maceration temperature contributed to higher esters and organic acids. Impact aroma compounds were related to models for floral, sweet fruit, temperate fruit, and vegetal, whereas the model of rose and strawberry contained only varietal volatile compounds, and temperate fruit could be regressed by impact fermentation aroma compounds.

Suplementasi Probiotik (Lactobacillus plantarum) dalam Sari Buah Sebagai Alternatif Produk Pangan Fungsional

Most of probiotic product as functional food were developed from dairy product. However, milk protein content cause allergy and make it limited to non vegetarians only. To solve these problems, some efforts were tried to produce probiotic drink from fruit juice, such as pineaple, tomato, papaya and aple. The aims of this research were to know the quality of probiotic fruit juice organoleptically and the viability of probiotic in it. Lactobacillus plantarum were used as probiotic and the fermentation process were last for 5 days at 30°C. The results showed that the best quality performed by fermented aple juice, with sour taste, pale brown color, aple fermented aroma and good homogenity. The probiotic viability also showed highest number, 1,7x108 cfu/ml. This research can be developed to produce fermented fruit juice with better quality.

Pilot-scale evaluation the enological traits of a novel, aromatic wine yeast strain obtained by adaptive evolution

In the competitive context of the wine market, there is a growing interest for novel wine yeast strains that have an overall good fermentation capacity and that contribute favorably to the organoleptic quality of wine. Using an adaptive evolution strategy based on growth on gluconate as sole carbon source, we recently obtained wine yeasts with improved characteristics in laboratory-scale fermentations. The characteristics included enhanced fermentation rate, decreased formation of acetate and greater production of fermentative aroma. We report an evaluation of the potential value of the evolved strain ECA5™ for winemaking, by comparing its fermentation performance and metabolite production to those of the parental strain in pilot-scale fermentation trials, with various grape cultivars and winemaking conditions. We show that the evolved strain has outstanding attributes relative to the parental wine yeast strain, and in particular the production of less volatile acidity and greater production of desirable volatile esters, important for the fruity/flowery character of wines. This study highlights the potential of evolutionary engineering for the generation of strains with a broad range of novel properties, appropriate for rapid application in the wine industry.

Changes in Bacterial Composition of Zucchini Flowers Exposed to Refrigeration Temperatures

Microbial spoilage is one of the main factors affecting the quality of fresh fruits and vegetables, leading to off-flavor, fermented aroma, and tissue decay. The knowledge of microbial growth kinetics is essential for estimating a correct risk assessment associated with consuming raw vegetables and better managing the development of spoilage microorganisms. This study shows, for the first time, that only a part of total microbial community, originally present on fresh harvested female zucchini flowers, was able to adapt itself to refrigerated conditions. Through the study of microbial growth kinetics it was possible to isolate forty-four strains belonging to twenty-two species of the genera Acinetobacter, Arthrobacter, Bacillus, Enterobacter, Erwinia, Klebsiella, Pantoea, Pseudoclavibacter, Pseudomonas, Serratia, Staphylococcus, and Weissella, suggesting Enterobacteriaceae as potentially responsible for pistil spoilage.

INFLUENCE OF FRUIT MATURATION, MODIFIED ATMOSPHERE PACKAGING AND STORAGE TEMPERATURE ON PHYSICO-CHEMICAL QUALITY ATTRIBUTES OF FRESH-CUT WEST INDIAN LIME (CITRUS AURANTIFOLIA)

ISHS International Conference on Postharvest and Quality Management of Horticultural Products of Interest for Tropical Regions INFLUENCE OF FRUIT MATURATION, MODIFIED ATMOSPHERE PACKAGING AND STORAGE TEMPERATURE ON PHYSICO-CHEMICAL QUALITY ATTRIBUTES OF FRESH-CUT WEST INDIAN LIME (CITRUS AURANTIFOLIA)

Effect of aromatic precursor addition to wine fermentations carried out with different Saccharomyces species and their hybrids

This work explores the ability of different yeast strains from different species of the genus Saccharomyces (S. cerevisiae, S. uvarum and S. kudriavzevii) and hybrids between these species to release or form varietal aroma compounds from fractions of grape odourless precursors. The de novo synthesis by the yeasts of some of the varietal aroma compounds was also evaluated. The study has shown that de novo synthesis affects some lipid derivatives, shikimic derivatives and terpenes in all species and hybrids, with some remarkable differences amongst them. The release or formation of aroma compounds from precursors was found to be strongly linked to the yeast or hybrid used, and the triple hybrid S. cerevisiae × S. bayanus × S. kudriavzevii in particular and secondarily the hybrid S. cerevisiae × S. bayanus were highly efficient in the production of most varietal aroma compounds, including γ-lactones, benzenoids, volatile phenols, vanillin derivatives and terpenols. The presence of precursors in the fermenting media caused a surprising levelling effect on the fermentative aroma composition. Altogether, these results suggest that it is possible to modulate wine aroma by employing different yeast species in order to create new wines with different aromatic notes.

Fungicide residues in grapes determined the dynamics of Saccharomyces cerevisiae strains during spontaneous wine fermentation

Impact of three fungicides against B. cinerea (iprodione, pyrimethanil and f ludioxonil plus cyprodinil) on the population of Saccharomyces cerevisiae strains during the spontaneous alcoholic fermentation was studied. With regard to the use of fungicides in the vineyard at two stages of the grapevine growth we followed four different spontaneous fermentations: control, iprodione, pyrimethanil and f ludioxonil plus cyprodinil. The fungicide residues in the grapes were determined by GC/MS system and the fermentations were followed by changes in yeast, sugar, and ethanol concentrations using colony counting and HPLC. The karyotype analysis of 473 isolates was done by pulsed-field gel electrophoresis. The fungicide residues in the grapes at the harvest were below the maximum residue limits. Isolates of S. cerevisiae were classified into 15 karyotype groups. The duration of the processes and the populations of the karyotypes differed between the fermentations. The iprodione and control fermentations lasted 36 days with the prevalence of karyotype A while the fludioxonil plus cyprodinil fermentation lasted 50 days and karyotype D led the process. In the pyrimethanil fermentation, none of the karyotypes prevailed in the must and the fermentation lasted much longer than others did (68 days). The results showed that the fungicide residues have an influence on the fermentation kinetics and selection of S. cerevisiae strains during the spontaneous alcoholic fermentation and therefore should be considered as an important factor that may indirectly influence the formation of fermentation aroma in the wine produced by such process.