Production Of Aromatic Compounds Research Articles

Evaluation of process involved in the production of aromatic compounds in Gram-negative bacteria isolated from vanilla (Vanilla planifolia ex. Andrews) beans.

The present investigation was aimed at isolating and identifying bacterial strains from cured vanilla beans. Additionally, the study focused on evaluating bacterial processes pertaining to the aromatic compounds production (ACP). Three bacteria were isolated from Vanilla planifolia beans, previously subjected to the curing process. According to morphological, biochemical and 16S rRNA analysis, the strains were identified as Citrobacter sp., Enterobacter sp. and Pseudomonas sp. The polygalacturonase activity (PGA) was determined using the drop, cup-plate and DNS methods. Aromatic compounds production was analysed by cup-plate method using FA as substrate and quantified by high performance liquid chromatography (ppm), the functional groups of vanillic acid (VA) were identified by FT-IR and the aromatic compounds (AC) resistance was determined and reported as minimum inhibitory concentration. Citrobacter sp., Enterobacter sp. and Pseudomonas showed PGA (70·31±364, 76·07±12·47 and 51±10·92Uml-1 respectively), were producers of VA (3·23±0·49, 324±41 and 265·99±11·61ppm respectively) and were resistant to AC. The Gram-negative bacteria isolated from V. planifolia beans were responsible for ACP. This is the first evidence for the role of Gram-negative bacterial isolates from cured Mexican V. planifolia beans in the process related to ACP.

Polyethylene high-pressure pyrolysis: Better product distribution and process mechanism analysis

Pyrolysis is currently an effective way to recycle plastics. High-pressure conditions can change the pyrolysis product component distribution, but the microscopic mechanism has not been well elucidated. To explore the relationship of product distribution versus pressure and explain the microscopic mechanism of polyethylene high-pressure pyrolysis, experiments under a large initial pressure range from 1 bar to 51 bar at initial temperatures of 330–380 °C were carried out in an autoclave. In the process of polyethylene high-pressure pyrolysis, the temperature within the reactor exceeded the set temperature by 100 °C at a rate of 150 °C/min. The thermal runaway phenomenon was caused by the polymerization of concentrated olefins in liquid form, which was initiated by hydrocarbon radicals. As the pressure increased, the reaction peak temperature was risen and more small molecules were produced. Under an initial temperature of 340 °C and high-pressure conditions, polyethylene was completely converted into liquid and gas products. The experimental results also revealed that high-pressure conditions led to the production of aromatic compounds and isoparaffins, as well as more cycloalkanes and fewer olefins in the liquid product, making the product characteristics closer to the fuel standard. Finally, this paper proposes the radical microscopic mechanisms of polyethylene thermal degradation under atmospheric-pressure and high-pressure conditions.

The ability of Lactococcus lactis subsp. lactis bv. diacetylactis strains in producing nisin.

Lactococcus lactis subsp. lactis bv. diacetylactis is a relevant microorganism for the dairy industry because of its role in the production of aromatic compounds. Despite this technological property, the identification of bacteriocinogenic potential of obtained strains can offer the additional positive aspect of biosafety. A panel of 15 L. lactis subsp. lactis bv. diacetylactis strains was characterised for the presence and expression of bacteriocin related genes, and further investigated regarding the nisin operon. Eight strains were positive only for nisA, and one strain (SBR4) presented a full nisin operon, with sequencing that was shown to be similar to nisin Z. Only SBR4 presented inhibitory activity against 16 microbial target strains. The growth curves of selected targets strains confirmed the inhibitory activity of SBR4 and consequently the nisin production. This research has demonstrated the inhibitory potential of L. lactis subsp. lactis bv. diacetylactis strain, SBR4, due to its ability to produce nisin Z. This biopreservative potential, associated to previously characterised technological properties, allow the indication of this strain as a promising candidate to be used by the dairy industry as a starter or adjunct culture.

Diversity of volatile organic compound production from leucine and citrate in Enterococcus faecium.

Enterococcus faecium is frequently isolated from fermented food; in particular, they positively contribute to the aroma compound generation in traditional cheese. Citrate fermentation is a desirable property in these bacteria, but this feature is not uniformly distributed among E. faecium strains. In the present study, three selected E. faecium strains, IQ110 (cit-), GM70 (cit+ type I), and Com12 (cit+ type II), were analyzed in their production of aroma compounds in milk. End products and volatile organic compounds (VOCs) were determined by solid-phase micro-extraction combined with gas chromatography mass spectrometry (SPME-GC-MS). Principal component analysis (PCA) of aroma compound profiles revealed a different VOC composition for the three strains. In addition, resting cell experiments of E. faecium performed in the presence of leucine, citrate, or pyruvate as aroma compound precursors allowed us to determine metabolic differences between the studied strains. GM70 (cit+ type I) showed an active citrate metabolism, with increased levels of diacetyl and acetoin generation relative to Com12 or to citrate defective IQ110 strains. In addition, in the experimental conditions tested, a defective citrate-fermenting phenotype for the Com12 strain was found, while its leucine degradation and pyruvate metabolism were conserved. In conclusion, rational selection of E. faecium strains could be performed based on genotypic and phenotypic analyses. This would result in a performing strain, such as GM70, that could positively contribute to flavor, with typical notes of diacetyl, acetoin, 3-methyl butanal, and 3-methyl butanol in an adjuvant culture.

Continuous and green microflow synthesis of azobenzene compounds catalyzed by consecutively prepared tetrahedron CuBr

An environmentally friendly and cross-selective process intensification for the continuous synthesis of symmetric aromatic azo compounds by using self-made cuprous bromide as the catalyst under mild conditions in the microreactor was developed. A novel tetrahedron cuprous bromide catalyst which shows outstanding catalytic activity and satisfactory stability has been synthesized in continuous flow microreactor. The online immobilization of self-made cuprous bromide on the catalyst bed achieved oxidative coupling of aromatic amines (oxygen as oxidant) and high-performance gas–liquid–solid three-phase reaction, which strongly limited the possibility of undesired reaction pathways, improving product selectivity and reducing waste generation. Meanwhile, the yield of azo-coupling reaction was up to 98% under optimized condition. As compared with earlier traditional method (diazotization reaction) for synthesizing azobenzene, the designed micro-flow process displays significant advances in terms of selectivity, waste emissions, sustainability and productivity. The combination of online immobilization of self-made cuprous bromide and precise and safe control through the microreactor provides a green solution for the industrial production of valuable aromatic azo compounds.

Volatile and sensory evaluation of Mexican Fresco cheese as affected by specific wild Lactococcus lactis strains

Lactococcus lactis is the lactic acid bacteria most frequently used for the production of cheese starter cultures, mainly because of their efficient production of aroma compounds. However, commercial cultures do not always produce the typical aroma notes of artisanal raw-milk cheeses. Thus, the objective of this study was to characterize the volatile compounds generated by wild L. lactis strains in Mexican Fresco cheese made with pasteurized milk. Four strains of wild L. lactis were evaluated for their aroma production in Mexican Fresco cheese using sensory and instrumental analysis. The aroma profiles were evaluated by descriptive sensory analysis. Volatiles were determined by solid-phase microextraction and gas chromatography-mass spectrometry. Principal component analysis was applied to interpret analytical and sensory data. Mexican Fresco cheese aroma was described as milkfat, yogurt, yeasty, barny, dirty socks, and Fresco cheese. Cheese with L. lactis strains R7 or B7 were most similar to commercial raw milk Fresco cheese in all aroma descriptors. Volatiles identified in all cheeses were esters, acids, alcohols, ketones, and aldehydes, but the main differences were found for total volatile relative abundance. Also, volatile concentrations (µg/g) in commercial raw milk Fresco cheese and cheeses made with L. lactis R7 or B7 were 4 methyl esters [C4 (4.15 vs. 5.47-13.74), C6 (0.12 vs. 1.53-15.34), C8 (1.06 vs. 0.32-6.65), and C10 (0.62 vs. 0.41-3.74)], 7 acids [C4 (1.92 vs. 0.30-9.29), C6-C10 (0.05-4.48 vs. 0.11-30.45), and C12 (0.13 vs. 0.28-0.30)], 2 alcohols [(3-methyl-1-butanol (3.48 vs. 3.4-13.13) and phenylethyl alcohol (0.10 vs. 0.63-2.04)], and 1 ketone (acetoin; 1.22 vs. 0.28-0.99). The first 3 principal components explained 78.2% of the total variation and clearly distinguished 3 main groups. Cheese made with L. lactis R7 was classified in the same group as key compounds associated with Fresco cheese aroma and show potential as a starter in Mexican Fresco cheese manufacture.

Development of a new high-throughput method for screening large yeast libraries for use in the beverage industry

High-throughput techniques have become crucial for the discovery of new strains suitable for the beverage industry. These approaches allow assessment of critical traits for fermented beverages such as; stress tolerance, growth, viability, vitality and aromatic compound production in a fast and effective manner. The growth rate of 24 Saccharomyces and non-Saccharomyces yeast strains were evaluated in industrially relevant media. High-throughput robotic platforms, the ROTOR HDA and PIXL, were used to pin colonies on solidified synthetic apple juice (SAJ), malt extract (ME), apple juice (AJ) and wort (WO) media. During incubation at 20 and 25 °C for up to 240 hours, the plates were imaged, and analysed via PhenoBooth and the ggplot2 R package. The results were corroborated via liquid growth. Pichia scullata Y-7663 and Hanseniaspora vineae Y-17530 showed the highest growth values in ME, WO and AJ; with final colony diameters double that of the Saccharomyces cerevisiae ESM356-1 control. However, the former two strains displayed defective growth in SAJ. Kluyveromyces lactis Y-1140 exhibited high growth performance, especially in ME and WO. Interestingly, the ale strain S. cerevisiae Y-11875, showed significantly higher growth in SAJ and AJ medium than in ME and WO. Better adaptation to growth in wort conditions was expected. This trial shows that the fitness of yeast strains can be assessed in solid media representing industrial conditions. The method can be up-scaled to a wider format, opening the possibility of screening a thousand-fold libraries of industrially relevant and/or novel yeast isolates in a fast, cost-effective manner.

A study on the performance of coke resistive cerium modified zeolite Y catalyst for the pyrolysis of scrap tyres in a two-stage fixed bed reactor

Catalytic pyrolysis is a useful technique for the conversion of scrap tyres into liquid fuels. Zeolite catalysts were employed in the pyrolysis of scrap tyres for the production of aromatic rich fuel. Deactivation of zeolite catalysts during pyrolysis reaction was investigated which played an important role in the product quality and composition. Herein, the performance of microporous zeolite catalysts and mesoporous MCM-41 catalyst was evaluated in a two-stage fixed bed reactor for the pyrolysis of scrap tyres. Comparative studies showed the increase in the production of aromatic compounds up to 23.7% over zeolite catalyst as compared to 18.7% over MCM-41 catalyst. However, Zeolite Y catalyst exhibited higher coke formation led to the rapid deactivation. The stability of zeolite catalysts is addressed by the incorporation of Cerium metal within the framework of two zeolite catalysts namely Zeolite Y and ZSM-5 through the ion-exchange technique. Parent and spent catalysts were characterised using synchrotron FT-IR spectroscopy, temperature-programmed desorption of ammonia (NH3-TPD), N2 Physisorption, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H2-TPD). A higher percentage of aromatics were produced over the large pore Zeolite Y. Cerium ion-exchange decreased the formation of coke from 8.1% to 5.7% over submicron and large pore Zeolite Y catalyst. Moreover, naphthalene production decreased over both Ce-Zeolite Y and Ce-ZSM-5.

Evaluation of autochthonous cultures to improve the cheese flavor: A case study in hard cheese model.

The characterization of autochthonous cultures based on their contribution to cheese flavor is an additional selection criterion for their use in cheese making. The objective of the present work was to assess the ability of three strains of mesophilic lactobacilli: Lactobacillus casei 72 (Lc72), L. paracasei 90 (Lp90), and L. plantarum 91 (Lp91), one strain of thermophilic lactobacillus: L. helveticus 209 (Lh209), and the thermophilic-mesophilic combinations, to grow and produce aroma compounds in a hard cheese model. Microbiological counts, pH, and the profiles of carbohydrates, organic acids, and volatile compounds were analyzed during incubation for 14 days at 37 ℃. The population of mesophilic lactobacilli reached levels around 8.0 log CFU ml-1 at three days, but then decreased until ∼7.0 log CFU ml-1 toward 14 days. Thermophilic lactobacillus population reached and maintained levels around 7.7 log CFU ml-1 during incubation. Carbohydrates were absent in the hard cheese model, and so no change in the pH values and in the levels of lactic acid was detected. Mesophilic lactobacilli, inoculated individually or in association with Lh209, metabolized the citric acid and produced ethanoic acid. The profiles of volatile compounds of mesophilic lactobacilli (characterized mainly by butan-2-one, 3-hydroxybutan-2-one, 3-methylbutan-1-ol, hexan-1-ol, 2-phenylethanol, and ethanoic acid) were different from the profile of thermophilic lactobacillus Lh209 (characterized mainly by heptan-2-one, ethyl acetate, isoamyl hexanoate, pentan-1-ol, decanoic acid, and 2- and 3-methylbutanal). Cooperative effects in the production of compounds related to cheese flavor, such as 3-hydroxybutan-2-one, ethyl butanoate, ethanol, pentan-2-ol, hexan-1-ol, benzeneacetaldehyde, 2-phenylethanol, and heptanoic acid, were largely evidenced between Lh209 and Lp91; in a lesser extent, cooperative effects were also found for Lh209+Lp90 for the following compounds: 3-hydroxybutan-2-one, isoamyl acetate, and ethanoic acid. Of the mesophilic lactobacilli strains evaluated, Lp91 and Lp90 would be interesting candidates for its use as adjunct cultures in hard cheeses to improve and diversify the flavor.

Hydrothermal liquefaction of corn straw with mixed catalysts for the production of bio-oil and aromatic compounds

In this study, hydrothermal liquefaction (HTL) of corn straw at different operation temperatures, reaction time and catalyst dosage were investigated, and the main product was heavy bio-oil. Results showed that CuO + NaOH have a synergistic effect in the HTL of corn straw. The product distribution and composition were also studied during the process, in which aromatic compounds achieved the highest proportion in heavy bio-oil. Moreover, the yield of aromatic compounds in hydrothermal products increased under simultaneous action of homogeneous and heterogeneous catalysts. The maximum ratio of aromatic compounds was 89.84% under condition of temperature 230 °C, reaction time 1 h, CuO content 3 g and NaOH 100 mL (1 mol·L−1). GC–MS analysis indicated that the major organic compounds in heavy bio-oil at temperatures between 210 °C and 270 °C were interestingly similar. SEM, XRD, H2-TPR and XPS analysis showed that CuO was completely reduced to copper in the process.

Pyrolysis of oil sludge from the offshore petroleum industry: influence of different mesoporous zeolites catalysts to obtain paraffinic products

ABSTRACT Pyrolysis of oil sludge from the petroleum industry in contact with three mesoporous zeolite catalysts (CBV 720, 760 and 780) was carried out at 450°C to obtain oil rich in paraffin. The properties of the catalysts were characterized by XRD, XRF, NH3-TPD, FT-IR, TGA and nitrogen ad/desorption isotherms, while the pyrolysis oil was analysed by GC-MS. The products obtained in the presence of mesoporous zeolites showed selectivity for conversion of light hydrocarbons with decreased content of aromatic compounds. The homogeneous porosity distribution of the CBV 780 was the determining factor in catalytic pyrolysis. The residue could be treated by pyrolysis using mesoporous zeolite. The use of this catalyst produced 56% oil fraction with the highest yield of light hydrocarbons (96%). Compared with the thermal pyrolysis of this waste, the use of mesoporous zeolitic catalysts increased the production of light hydrocarbons and reduced the production of aromatic compounds in the pyrolysis oil from sludge.

Development of A Low-Alcoholic Fermented Beverage Employing Cashew Apple Juice and Non-Conventional Yeasts

Cashew apples are by-products in the production of cashew nuts, which are mostly left to rot in the fields. Cashew apple juice (CAJ), a highly nutritious beverage, can be produced from them. It is rich in sugars and ascorbic acid, but its high polyphenol content makes it bitter and astringent, and therefore difficult to commercialize. The kingdom of fungi contains more than 2000 yeast species, of which only a few species have been studied in relation to their potential to produce aroma compounds. The aim of this research was to develop a new low-alcoholic fermented beverage to valorize cashew apples. For this purpose, a screening was carried out employing non-conventional yeast species and some species of the genus Saccharomyces for comparison, followed by a more detailed study with four selected strains cultured at different conditions. The production of volatile aroma compounds as a function of the presence of oxygen, temperature, and yeast species was investigated. The results showed that the more diverse aroma profiles appeared at 25 °C under anaerobic cultivation conditions, where Saccharomyces cerevisiae WUR 102 and Hanseniaspora guilliermondii CBS 2567 excelled in the synthesis of certain aroma compounds, such as β-phenylethanol and its acetate ester (rose aroma). Further studies are needed to test consumer acceptance of these new products.

Freeze-Drying of 6-Pentyl-α-Pyrone Produced byTrichoderma harzianumIOC4042 in Solid State Fermentation

Abstract The search for products containing natural ingredients has spurred researchers to develop biotechnological processes for the production of aroma compounds, such as solid state fermentation...

The Changes of the Volatile Compounds Derived from Lipid Oxidation of Boneless Dry‐Cured Hams During Processing

The generation of aroma during processing of boneless dry‐cured hams is investigated by evaluating neutral and acid lipases, phospholipase, lipoxygenase (LOX), thiobarbituric acid reactive substances (TBARS) values, fatty acid composition, and volatile substances derived from lipid oxidation (VCDFLO). It is found that moisture content, acid lipase, and phospholipase decreases in the whole processing, but sodium chloride content and TBARS increase. Neutral lipase, LOX, and total fatty acids increase from raw ham to the end of resting and decrease subsequently. 15 VCDFLO containing six ketones, three aldehydes, three hydrocarbons, one alcohol, one carboxylic acid, and one furan are identified. The total peak area of VCDFLO increases during the entire processing and indicates 39.76–40.75% of total volatile compounds. Hexanal, 1‐octen‐3‐ol, octanal, and nonanal are the major characteristic volatiles of boneless dry‐cured hams. Therefore, VCDFLO formation is associated with lipid‐related enzymes and helpful for the aroma.Practical Applications: The pork that has high intramuscular fat content is usually selected to produce boneless dry‐cured hams, because intramuscular phospholipids, and triglycerides are important precursors to produce aroma compounds. Exploring the formation mechanism of flavor associated with lipid oxidation will be beneficial for improving the quality of hams. Therefore, this study demonstrates the relationship between lipolysis‐oxidation and the generation of flavor compounds during the processing of boneless dry‐cured hams.This study demonstrates that thiobarbituric acid reactive substances (TBARS) values can reveal the changed trend of volatile compounds derived from lipid oxidation (VCDFLO) very well, and that lipid‐related enzymes plays an important role in the development of VCDFLO.

Rational Engineering of Chorismate-Related Pathways in Saccharomyces cerevisiae for Improving Tyrosol Production.

Tyrosol is extensively used in the pharmaceutical industry as an important natural product from plants. In this study, an exogenous pathway involved in catalyzing tyrosine to tyrosol was introduced into Saccharomyces cerevisiae. Furthermore, The pyruvate decarboxylase gene pdc1 was deleted to redirect the flux distribution at the pyruvate node, and a bifunctional NAD+-dependent fused chorismate mutase/prephenate dehydrogenase from E. coli (EcTyrA) and its' tyrosine inhibition resistant mutant (EcTyrAM53I/A354V) were heterologously expression in S. cerevisiae to tuning up the chorismate metabolism effectively directed the metabolic flux toward tyrosol production. Finally, the tyrosol yield of the engineered strain GFT-4 was improved to 126.74 ± 6.70 mg/g DCW at 48 h, increased 440 times compared with that of the control strain GFT-0 (0.28 ± 0.01 mg/g DCW). The new synergetic engineering strategy developed in this study can be further applied to increase the production of high value-added aromatic compounds derived from aromatic amino acid or shikimate in S. cerevisiae.

Preparation of mesoporous ZSM-5 catalysts using green templates and their performance in biomass catalytic pyrolysis

The micropores present in ZSM-5 are beneficial to the production of aromatic compounds in biomass catalytic pyrolysis, although the small pore size leads to severe coke deposition on the catalyst. In this study, a micro-mesoporous structured ZSM-5 zeolite catalyst was synthesized and modified with green templates (sucrose, cellulose, and starch) to introduce additional mesopores. It was found that the catalysts modified using the sucrose and cellulose templates only exhibited a slight increase in their micropore volumes, while the mesopore volume of ZSM-ST (modified with the starch template) reached up to 0.359 cm3/g. This increase promoted the cracking of bulky oxygenates and suppressed the polymerization reaction on the ZSM-5 surface, thereby producing a greater number of aromatic products. Moreover, the benzene, toluene, and xylene (BTX) yields exhibited a positive correlation with the catalyst mesopore volume, with the highest BTX yield of 91.84 mg/g being obtained with 10% starch addition.

A tiered analytical approach for target, non-target and suspect screening analysis of polar transformation products of polycyclic aromatic compounds

Polycyclic aromatic compounds (PACs) possess toxicity towards humans, and their presence in the environment is unwanted. Polar transformation products (TPs) are more mobile, and can be considered emerging contaminants, as they represent a more bioavailable carrier of the same toxic properties. Acidic TPs has been proposed as an important class of polar TPs. This study presents a tiered analytical approach to investigate acidic and polar PAC TPs in environmental conditions. The tiered approach exploits target analysis for quantification of acids; suspect screening for tentative identification based on retention time and spectral matching using databases; and finally non-target analysis based on chromatography and data independent broadband MS to highlight potentially unknown analyte peaks. The approach includes a mixed-mode anion exchange solid phase extraction (MAX-SPE) to fractionate neutral and acidic compounds, and is applied to three cases: I) Photo-oxidation of six PACs generated suspected hydroxylated-, carbonylated- and carboxylated PACs but also proposed the presence of mono- and dicarboxylic acids, which have not been reported elsewhere. For a subset of four acids, conversion rates were determined. II) Recovery of spiked acids from diesel spilled harbor water was 80% by LC-MS, and diesel spill weathering was evaluated from the neutral fraction by GC-MS. III) By non-target analysis sulfonated PACs, presumable derived from photo-oxidation, were detected in run-off basins of an arctic landfarm, alongside hypothesized naturally occuring fatty acids. The tiered approach is a sensitive and versatile tool to extract information on PACs and their polar TPs from polluted environmental sites.

Specific molecular interactions between Vitis vinifera and Botrytis cinerea are required for noble rot development in grape berries

Under peculiar climatic conditions, the beneficial form of the necrotrophic fungus Botrytis cinerea can develop on grape berries as a latent infection, known as noble rot, which induces positive biochemical and metabolic changes in the berries, including an increase in the sugar content and the production of aromatic compounds that improve wine quality. The infected berries undergo rapid withering, which is required to produce famous sweet white wines such as Sauternes and Tokaj. To gain insight into the molecular interactions between grapevine berries (Vitis vinifera) and B. cinerea during the establishment of noble rot, we prepared a large-scale transcriptomics dataset representing noble rot development and carried out a comparative meta-analysis with gray mold infection and natural post-harvest withering. In particular, we artificially induced berry botrytization of two grape varieties (Garganega and Möller-Thurgau) and sampled them at different stages of noble rot for comparative whole-transcriptome analysis, highlighting important common transcriptional reprogramming in both varieties reflecting an accelerated withering process. Simultaneously, we analyzed the modulation of B. cinerea genes and compared the expression profile during noble rot development with the previously reported gray mold infection profile, revealing the onset of an infection process by the fungus in its beneficial form associated with reduced virulence. This, together with the restrained plant defense response observed in botrytized berries, may favour the development of noble rot instead of gray mold. Finally, the comprehensive meta-analysis of gene expression during noble rot infection, gray mold and post-harvest withering led to the identification of key genes specifically modulated during noble rot infection.

Methyl jasmonate-induced compositional changes of volatile organic compounds in Polygonum minus leaves

Polygonum minus Huds. is a medicinal aromatic plant rich in terpenes, aldehydes, and phenolic compounds. Methyl jasmonate (MeJA) is a plant signaling molecule commonly applied to elicit stress responses to produce plant secondary metabolites. In this study, the effects of exogenous MeJA treatment on the composition of volatile organic compounds (VOCs) in P. minus leaves were investigated by using a metabolomic approach. Time-course changes in the leaf composition of VOCs on days 1, 3, and 5 after MeJA treatment were analyzed through solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC–MS). The VOCs found in MeJA-elicited leaves were similar to those found in mock-treated leaves but varied in quantity at different time points. We focused our analysis on the content and composition of monoterpenes, sesquiterpenes, and green leaf volatiles (GLVs) within the leaf samples. Our results suggest that MeJA enhances the activity of biosynthetic pathways for aldehydes and terpenes in P. minus. Hence, the production of aromatic compounds in this medicinal herb can be increased by MeJA elicitation. Furthermore, the relationship between MeJA elicitation and terpene biosynthesis in P. minus was shown through SPME–GC–MS analysis of VOCs combined with transcriptomic analysis of MeJA-elicited P. minus leaves from our previous study.

Wine chemical, sensory, aroma compound and protein analysis of wines produced from chemical and biological fungicide treated Chenin blanc grapes

Fungal diseases in vineyards are one of the main causes leading to economic losses within the viticulture sector and are continuously increasing with time. The most common of these fungal diseases are powdery mildew, downy mildew and grey mould which are controlled by the use of fungicides. However, fungicide residues can alter the fermentation process and prevent some biochemical pathways of yeast metabolism involved in phenolic and/or aroma compound production that are critical for sensory quality. In this study, Chenin blanc grapes treated with chemical and natural fungicides were used to produce small-scale wines and laboratory-scale fermentations. Treatments consisted of a control (an approved chemical used in industry), a 1x and 2x treatment (new formulations). Laboratory-scale fermentations were conducted in duplicate using the commercial Saccharomyces cerevisiae (S. cerevisiae) Active Dry Wine Yeast (ADWY) strains VIN 13 and VIN 7. The fermentations were monitored by weighing frequently until they stabilised (CO2 weight loss). Small-scale wines were made according to the standard Nietvoorbij experimental wine making procedure. At the end of fermentation, lees samples were subjected to CHEF gel electrophoreses to confirm that the inoculated yeast strain completed the fermentations. Moreover, fermenting wine samples, collected at the start and end of the fermentation, were subjected to protein extraction, quantification and characterisation the yeast proteins expressed at the various stages of fermentation. Resultant wines were subject to chemical and sensory evaluations five months after bottling. From the results obtained in the above study, it was concluded that the inoculated yeast strains used for wine making completed the fermentations at a similar rate to their respective controls (registered fungicide). In addition, small-scale cellar fermentations showed that the fungicide treatments (1x the recommended dosage [Treatment 1] and 2x the recommended dosage [Treatment 2]) compared to the controls had no notable negative effects on wine aroma and sensory profiles although differences were observed in the proteins expressed after the fermentation. The chemical and biological fungicides had no notable effects on the wine making procedure and quality of resulting wines compared to the registered fungicide.