Formation Of Volatile Sulfur Compounds Research Articles

Effects of heat treatments on the stability, antioxidant activity and volatiles of milk and whey ultrafiltration permeates

Milk (MP) and whey (WP) ultrafiltration permeates were obtained from different dairy processing plants. The effects of pH (4 or 6) and heat treatments (63 °C, 30 min; or 110 °C, 6 min) on permeate stability were measured by the increase of turbidity, and precipitation of nitrogen and calcium. The antioxidant activity and the production of volatiles compounds, as affected by heat treatments, was also evaluated. WP showed a higher sensitivity to heat treatments than MP. Increasing heating temperature reduced the stability of permeates, with an intensified effect at pH 6. Calcium precipitation was the main factor responsible for the increase in turbidity. Lowering the pH to 4 prior to heating strongly limited the development of turbidity. Sterilisation improved antioxidant activity of both permeates, with a greater effect on WP. Sterilisation had no effect on the concentration of volatile aldehydes but promoted the formation of volatile sulfur compounds, and more significantly in WP.

Impact of Nitrogen and Elemental Sulfur on Formation of Volatile Sulfur Compounds during Fermentation of Pinot Noir Grapes

The influence of yeast assimilable nitrogen (YAN) and elemental sulfur (S0) on the formation of volatile sulfur compounds (VSCs) during fermentation was investigated. Pinot noir fermentations were performed using Saccharomyces cerevisiae strain UCD522 or P1Y2 with an addition of 0, 5, or 15 µg/g elemental sulfur. H2S production during fermentation was measured using lead acetate tubes and additional VSCs measured by GC-PFPD. The addition of S0 resulted in H2S formation during alcoholic fermentation regardless of which yeast strain was used. H2S production was greater in fermentations performed by UCD522 with increasing amounts of S0 resulting in increased production of H2S. Higher S0 resulted in wines containing higher concentrations of methyl thioacetate and glutathione disulfide. Additional experiments examined the impact of nitrogen composition and S0. The addition of diammonium phosphate (DAP) resulted in an increase in H2S formation during fermentation whereas the addition of amino acids did not, whether S0 was added or not. Fermentations where DAP and S0 were both added produced a higher concentration of H2S compared to fermentations where S0 or DAP additions were made individually. VSCs in the wine were also impacted by the addition of nitrogen and/or S0 with the addition of S0 and nitrogen (DAP or amino acids) resulting in elevated concentrations of methyl thioacetate in the wines.

Keterkaitan antara Halitosis dengan Bakteri Penyebab Periodontitis

Halitosis, often known as foul breath, refers to an unpleasant odor that emanates from the mouth cavity when inhaling or talking. Halitosis can have a negative impact on a person's quality of life, including symptoms of depression or anxiety, low self-esteem, embarrassment, prejudice, and social isolation. Bad breath can be caused by both intra oral and extra oral factors. Bacterial growth in the oral cavity is excellent for the production of volatile sulfur compounds (VSC). The posterior dorsum of the tongue, gingival sulcus, periodontal pockets, and gingival embrasures are all places where bacterias can accumulate. Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis, and Treponema dentiocola are known to actively produce VSC through interactions with specific substrates such as cysteine, methionine, tryptophan, arginine, and lysine to produce hydrogen sulfide (H2S) and methylmercaptan (CH3SCH3). However, the presence of VSC does not indicate the presence of periodontitis, as any space in the oral cavity that can cause the retention of bacteria/biofilms can become a site for bacterial decomposition, thereby facilitating the growth of VSC. Tongue cleansing is proven to help reduce the formation of VSC.

EFFECTIVENESS OF RED BITES FRUIT (Beta vulgaris) AS A MOUTH MOUTH TO REDUCE HALITOSIS

Introduction: Halitosis or bad breath is often a problem because it can reduce the fluency of communication which causes embarrassment in socializing so that it has a psychological impact which results in low self-esteem, loss of self-image and can cause stress. This writing aims to determine the role of beets on the level of halitosis reduction. Review: Most of the known causes of halitosis come from food scrap left in the oral cavity which is processed by the normal flora of the oral cavity, and are the result of the production of the activity of bacteria in the mouth that causes the formation of Volatile Sulfur Compounds (VSC) in the oral cavity, which is a sulfur compound that is volatile and smells bad. Since time immemorial, many people believe that natural ingredients are able to treat various diseases because they are considered less likely to cause side effects compared to synthetic drugs. One of the natural ingredients that can be used is beetroot. Beetroot contains several active compounds such as carotenoids, saponins, glycine betanin, betanin, polyphenols, flavonoids, phenols, tannins and alkaloids. Beetroot is thought to be able to reduce the level of halitosis because the compounds in beets contain antibacterial active substances that can reduce bacteria in the oral cavity in reducing the level of halitosis. Conclusion: Beets (Beta Vulgaris) are effective in reducing the level of halitosis because they have antibacterial properties.

Integrated transcriptomic and volatilomic profiles to explore the potential mechanism of aroma formation in Toona sinensis

As an important quality determinant of Toona sinensis, the unique aroma largely impacts the purchasing behavior of consumers. However, the underlying formation mechanism of the characteristic aroma of T. sinensis remains poorly understood. In this work, integrative volatile/nonvolatile compounds profiling and RNA sequencing were used to characterize six T. sinensis cultivars. Volatile sulfur compounds (VSCs) and terpenoids were the main volatile organic compounds (VOCs) in T. sinensis, accounting for 36.95–67.27% and 17.75–31.36% of the total VOC content, respectively. Notably, the VOCs originated from terpenoid biosynthesis, and the degradation of unsaturated fatty acids (UFAs) played important roles in reconciling the irritating odor of VSCs. The above differential metabolic profiles are the main sources of the specific aroma of different T. sinensis cultivars. Furthermore, 13 volatile organic compounds were identified as potential biomarkers to distinguish these T. sinensis cultivars by chemometric analysis. Based on the analysis of transcriptomic datasets, the potential biosynthetic pathways of the key VSCs were firstly confirmed in T. sinensis. It was found that 1-propenylsulfenic acid is a crucial precursor in the formation of characteristic VSCs in T. sinensis. Additionally, two potential mechanisms were proposed to explain the differences of the key VSCs among six T. sinensis cultivars. These results provide theoretical guidance for improving the aroma quality of T. sinensis.

Evaluation of oenological tannins for preventing the light-struck taste

The light-struck taste (LST) is a fault occurring in white and rosé wines associated to the formation of volatile sulfur compounds (VSCs) due to the reactions between riboflavin (RF) and methionine (Met). We investigated the possible preventing effect of 15 commercial tannins of different origin in model wine added with RF and Met, under oxic and anoxic conditions, and submitted to standardized light-exposure. All the tannins limited the degradation of Met in comparison to the tannin-free samples. Lower concentrations of VSCs were found in presence of tannins even under anoxia, condition favouring their formation. The sniffing trials evidenced the minor perception of cooked cabbage note with added tannins. The multivariate analysis showed the presence of flavan-3-ols was related to the formation of DMDS and DMTS, while tannic acid was related to MeSH, both the behaviors occurring under oxic condition. The study highlighted the ability of tannins to prevent the LST.

HALITOSIS ASSESSMENT IN PATIENTS WITH ORTHODONTIC APPLIANCE AND THEIR ASSOCIATION WITH BULLYING

Halitosis is the term used to define the unpleasant odor exhaled through exhaled air, which may be signaling a pathological, physiological or adaptive condition. Most individuals who present this alteration experience personal discomfort, social embarrassment and emotional anguish, which can cause serious disturbances of coexistence, especially in the school environment. The etiology of halitosis is multifactorial, but its main cause comes from the formation of volatile sulfur compounds (VSC) resulting from the proteolytic bacterial action on stagnant organic matter in the oral cavity. The use of orthodontic appliances may be an agent related to the development of this alteration, since it favors the accumulation of organic residues, epithelial desquamation, gingival inflammation, in addition to making local hygiene difficult. Therefore, the present study aims to evaluate the breath of patients with orthodontic appliances and also the possible presence of bullying related to such an event, in young adults aged between 18 and 24 years, students at Universidade Paulista de Brasília. Breath assessment was performed using an organoleptic test (gold standard), which is performed by the examiner’s sense of smell, and a Halimeter® portable monitor, and saliva assessment was performed using a sialometry test, in which the amount of saliva was evaluated. The possible relationship with bullying was assessed through a specific questionnaire. Of the twelve students included in the study, seven presented halitosis when evaluated through the organoleptic test, however, of these seven only two presented parameters compatible with halitosis, when evaluated by the Halimeter®. In relation to bullying, this study showed that it was present in the lives of many respondents, but not necessarily because of breath.

Formation of volatile sulfur compounds and S-methyl-l-cysteine sulfoxide in Brassica oleracea vegetables

Besides glucosinolates, Brassica vegetables accumulate sulfur-containing (+)-S-methyl-l-cysteine sulfoxide (SMCSO, methiin), mainly known from Allium vegetables. Such (+)-S-alk(en)yl-l-cysteine sulfoxides can degrade to volatile organosulfur compounds (VOSCs), which have been linked to health beneficial effects. In the present study, the accumulation of SMCSO and the formation of VOSCs was investigated in Brassica oleracea vegetables. SMCSO content of commercially available white and red cabbages was monitored over a three-month period and linked with the formation of VOSCs. S-Methyl methanethiosulfinate was the main VOSC released from SMCSO. Upon heating, it degraded to dimethyltrisulfide and dimethyldisulfide, which were less abundant in fresh homogenates. SMCSO made up approximately 1% of the dry matter of cabbages and the overall contents were similar in white and red cabbages (3.2–10.2 and 3.9–10.3 µmol/g fresh weight, respectively). Using proteome profiling it was shown that recovery of VOSCs correlated with abundance of two isoforms of cystine lyase.

Case–control study related to the use of L-cysteine in the differential diagnosis of oral halitosis

Oral halitosis is characterized by a foul, unpleasant breath that emanates from the oral cavity due to local or systemic conditions. Approximately 90% of offensive odors are caused by volatile sulfur compounds (VSCs). L-cysteine, used as a test solution to control bad breath, induces the formation of VSCs and serves as a preliminary rinse. The study aim was to investigate the effectiveness of L-cysteine solution in differentiating the origin of oral halitosis using a gas chromatography apparatus. Methods: In total, 37 patients with an average age of 49.56 years were evaluated and divided into two groups: halimetry before the use of L-cysteine (n = 37) and halimetry after the use of L-cysteine (n = 37). Patients over 18 years of age, without severe systemic health impairment or infectious/contagious diseases, and who did not use medicines that influenced their breath were included. Halimetry was performed using the OralCroma™ device. In the halimetry before the use of L-cysteine group, 5.40%, 5.40%, and 64.86% of the patients had high levels of sulfide, methyl mercaptan, and dimethyl sulfide, respectively. After the use of L-cysteine, 48.64%, 8.10%, and 37.84% of the patients had high levels of sulfide, methyl mercaptan, and dimethyl sulfide. In this study, L-cysteine proved to be important for the assessment of oral halitosis and effective in differentiating the origin of oral halitosis; therefore, this compound could be used for the differential diagnosis of oral halitosis origin using the OralChroma™ device.

Influence of different types of LEDs lights on the formation of volatile sulfur compounds in white and rosé wines

The effect of LEDs light on the formation of volatile sulfur compounds (VSCs) and the final sensory quality of white and rosé wines was evaluated. Thus, different commercial wines were exposed for ten days to three types of lights. All wine samples were analyzed throughout the exposure period to determine the usual oenological parameters together with some other chemical characteristics (color evolution; riboflavin, cysteine and methionine photodegradation), VSC amounts and sensory characteristics. The results showed that the wines exposed to ultraviolet light suffered greater degradation of the aromatic precursors, mainly riboflavin, and had higher concentrations of VSCs. Regarding LED lights, these produced minimal degradative effects. So that we can consider this type of light as an alternative to reduce the economic impact that currently occurs due to the photodegradation of bottled wines.

Light-Struck Taste in White Wine: Protective Role of Glutathione, Sulfur Dioxide and Hydrolysable Tannins.

Light exposure of white wine can cause a light-struck taste (LST), a fault induced by riboflavin (RF) and methionine (Met) leading to the formation of volatile sulfur compounds (VSCs), including methanethiol (MeSH) and dimethyl disulfide (DMDS). The study aimed to investigate the impact of different antioxidants, i.e., sulfur dioxide (SO2), glutathione (GSH) and chestnut tannins (CT), on preventing LST in model wine (MW) and white wine (WW), both containing RF and Met. Both MW and WW samples were added with the antioxidants, either individually or in different combinations, prior to 2-h light exposure and they were stored in the dark for 24 months. As expected, the light induced the degradation of RF in all the conditions assayed. Met also decreased depending on the antioxidants added. The presence of antioxidants limited the formation of LST as lower concentrations of VSCs were found in both MW and WW samples. In the latter matrix, neither MeSH nor DMDS were detected in the presence of CT, while only DMDS was found in WW+GSH, WW+SO2+GSH and WW+CT+SO2 samples at a concentration lower than the perception thresholds. Considering the antioxidants individually, the order of their effectiveness was CT ≥ GSH > SO2 in WW under the adopted experimental conditions. The results indicate tannins as an effective enological tool for preventing LST in white wine and their use will be further investigated in different white wines under industrial scale.

How to modulate the formation of negative volatile sulfur compounds during wine fermentation?

ABSTRACTBeyond the production of positive aromas during alcoholic fermentation, Saccharomyces cerevisiae metabolism also results in the formation of volatile compounds detrimental to wine quality, including a wide range of volatile sulfur compounds (VSCs). The formation of these VSCs during wine fermentation is strongly variable and depends on biological and environmental factors. First, the comparison of the VSCs profile of 22 S. cerevisiae strains provided a comprehensive overview of the intra-species diversity in VSCs production: according to their genetic background, strains synthetized from 1 to 6 different sulfur molecules, in a 1- to 30-fold concentration range. The impact of fermentation parameters on VSCs production was then investigated. We identified yeast assimilable nitrogen, cysteine, methionine and pantothenic acid contents – but not SO2 content – as the main factors modulating VSCs production. In particular, ethylthioacetate and all the VSCs deriving from methionine catabolism displayed a maximal production at yeast assimilable nitrogen concentrations around 250 mg/L; pantothenic acid had a positive impact on compounds deriving from methionine catabolism through the Ehrlich pathway but a negative one on the production of thioesters. Overall, these results highlight those factors to be taken into account to modulate the formation of negative VSCs and limit their content in wines.

Experimental and theoretical study on the formation of volatile sulfur compounds under gas reservoir conditions

Volatile organic sulfur compounds (VOSC) are found in petroleum natural gas and condensates at trace levels. The abundance and δ34S values of VOSC were proposed as a proxy for thermal processes such as oil and gas generation during thermal maturation, thermochemical and microbial sulfate reduction, migration and expulsion. The understanding of VOSC formation and degradation mechanisms is needed to refine the use of δ34S values of VOSC as proxies for thermal processes over geological timescales in the subsurface. We therefore conducted pyrolysis experiments at 360 °C for 4, 12 and 72 h using pentane and H2S or pentanethiol as model compounds to study the formation and degradation pathways of VOSC and associated variations in δ34S values. The main products of these experiments are C1-C4 alkanes along with a variety of thiols and thiophenes, the most dominant VOSC formed. Most thiols were in equilibrium with H2S after 4 h based on their δ34S values. Thiophenes were first 34S depleted relative to H2S and only reached equilibrium at the 72 h experiment. The products and 34S fractionations in the pyrolysis experiment of pentanethiol at 360 °C and 12 h were similar to those of the experiment with H2S and pentane at the same conditions. This similarity suggests that pentanethiol is an intermediate product in the formation of aromatic VOSC during pyrolysis of pentane and H2S. Benzo- and dibenzothiophenes (BTs and DBTs) were formed in the liquid phase and their 34S depleted values relative to H2S indicated that they had not reached equilibrium. Ab-initio calculations of the thermodynamic properties of thiols, thiolanes, thiophenes BTs and DBTs were used to explain the relative abundance of products in the system and predict their abundance and S isotopic signature at reservoir conditions. The thermodynamic data suggests that at equilibrium, only small quantities of thiols and even smaller quantities of thiolanes can exist under our experimental conditions. Unlike thiols, the free energy of formation of thiophenes, BTs and DBTs is negative under these conditions indicating that the formation of these compounds is thermodynamically favored. The result suggests that the δ34S values of thiols are controlled by a very rapid equilibrium isotopic effect (EIE). On the other hand, aromatic sulfur compounds can preserve the δ34S value of the kinetic isotopic effect (KIE) associated with their formation for longer. However, under typical petroleum reservoir conditions, the formation of aromatic VOSC in the gas phase from short alkanes (<C5) and H2S is not thermodynamically preferred and thus their presence is expected to be either as kinetic products or due to influx and charge from a different source where the reactions were thermodynamically favorable. Thus, the abundance and Δ34S between H2S and VOSC can be used as a new approach to evaluate charge history within sulfur containing reservoirs.

Light-induced reactions of methionine and riboflavin in model wine: Effects of hydrolysable tannins and sulfur dioxide

The riboflavin-mediated photo-degradation of methionine in white wine has been related to onset of undesired light-struck taste. This research investigated the effects of different concentrations of riboflavin and methionine, hydrolysable tannins from various sources (nut galls, chestnut and oak woods) and sulfur dioxide on methionine degradation in a model wine exposed to light. Increased methionine concentration resulted in its increased degradation with the consequent formation of volatile sulfur compounds, namely methanethiol, dimethyl disulphide and dimethyl trisulphide. Tannins, especially nut gall tannin, were effective in limiting both methionine degradation and the production of volatile sulfur compounds. Sulfur dioxide enhanced the methionine degradation although the light-struck taste was not perceived when sulfur dioxide concentration was higher than 50 mg/L. In conclusion, the use of hydrolysable tannins can represent a promising tool for protecting white wine against the light-struck taste also limiting the use of sulfur dioxide.

Effects of Weissella cibaria CMU on Halitosis and Calculus, Plaque, and Gingivitis Indices in Beagles.

Weissella (W.) cibaria strain Chonnam Medical University (CMU) has shown oral colonizing ability and inhibitory effects on the formation of volatile sulfur compounds (VSCs) in vitro studies. The present study was conducted to analyze the effects of the W. cibaria CMU on canine oral health. Halitosis, calculus, plaque, gingivitis, and intraoral microbiota were assessed in 3 groups: control (maltodextrin), W. cibaria CMU low concentration (CMU-L, 2 × 107 colony forming unit [CFU]), and high-concentration (CMU-H, 2 × 109 CFU). Halitosis was analyzed using both organoleptic evaluation and measurement of VSCs. Intraoral microbiota were analyzed by real-time polymerase chain reaction. From week 4, the total VSC level in the CMU-H group (4.0 ± 1.30 ng/10 mL) was significantly lower than in the control group (6.3 ± 2.28 ng/10 mL). Significant reduction in methyl mercaptan in the CMU-treated groups was also observed. In addition, the plaque index in the CMU-treated groups was significantly decreased. The CMU-treated groups showed significant decreases in Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia and demonstrated the colonizing ability of W. cibaria CMU in the oral cavity. We demonstrated that W. cibaria CMU suppresses halitosis, colonizes the oral cavity, and inhibits the proliferation of malodor-causing oral bacteria in beagles. According to these results, we expect that W. cibaria CMU could be a new oral hygiene solution by reducing VSC production and inhibiting the growth of oral harmful bacteria in companion animals.

Inactivating Mutations in Irc7p Are Common in Wine Yeasts, Attenuating Carbon-Sulfur β-Lyase Activity and Volatile Sulfur Compound Production.

During alcoholic fermentation of grape sugars, wine yeasts produce a range of secondary metabolites that play an important role in the aroma profile of wines. In this study, we have explored the ability of a large number of wine yeast strains to modulate wine aroma composition, focusing on the release of the "fruity" thiols 3-mercaptohexan-1-ol (3-MH) and 4-mercapto-4-methylpentan-2-one (4-MMP) from their respective cysteinylated nonvolatile precursors. The role of the yeast gene IRC7 in thiol release has been well established, and it has been shown that a 38-bp deletion found in many wine strains cause them to express a truncated version of Irc7p that does not possess cysteine-S-conjugate β-lyase activity. In our data, we find that IRC7 allele length alone does not fully explain the capacity of a strain to release thiols. Screening of a large number of strains coupled with analysis of genomic sequence data allowed us to identify several previously undescribed single-nucleotide polymorphisms (SNPs) in IRC7 that, when coupled with allele length, more robustly explain the ability of a particular yeast strain to release thiols from their cysteinylated precursors. We also demonstrate that allelic variation of IRC7 not only affects the release of thiols but modulates the formation of negative volatile sulfur compounds from the amino acid cysteine. The results of this study provide winemakers with an improved understanding of the genetic determinants that affect wine aroma and flavor, which can be used to guide the choice of yeast strains that are fit for purpose.IMPORTANCE Volatile sulfur compounds contribute to wine aromas that may be considered pleasant, such as "tropical," "passionfruit," and "guava," as well as aromas that are considered undesirable, such as "rotten eggs," "onions," and "sewer." During fermentation, wine yeasts release some of these compounds from odorless precursor molecules, a process that is most efficient when performed by yeasts that express active forms of the protein Irc7p. We show that most wine yeasts carry mutations that reduce activity of this protein, affecting the formation of volatile sulfur compounds that impart both pleasant and unpleasant aromas. The results provide winemakers with guidance on the choice of yeasts that can emphasize or deemphasize this particular contribution to wine quality.

Effects of physicochemical parameters on volatile sulphur compound formation from l-methionine catabolism by non-growing cells of Kluyveromyces lactis

The present study investigated for the first time the effects of various physicochemical parameters on the production of volatile sulphur compounds (VSCs) by non-growing cells of Kluyveromyces lactis supplemented with l-methionine. The results showed that the production of VSCs positively correlated with the cell biomass, but it seemed that no clear relationship with l-methionine concentration existed. Temperature and pH significantly affected the formation of VSCs with more production at 30 °C and pH 5, respectively. Nitrogen supplementation (in the form of diammonium phosphate, DAP) repressed the production of VSCs. It is interesting to note that DAP and yeast extract supplementation induced the production of methional, but not Mn2+ supplementation. The presence of Mn2+ improved the production of methionol and dimethyl disulphide, but inhibited the formation of S-methyl thioacetate. The study indicated that optimization of physicochemical conditions and media composition would be crucial for producing l-methionine-derived VSC bioflavor.

Técnica de medição de saliva utilizada no CECOM em pacientes com halitose

A saliva é um fluido aquoso e transparente secretado pelas glândulas salivares diretamente na cavidade bucal. É composta, principalmente, de água (99%) e componentes orgânicos e minerais. Uma de suas principais funções é a autolimpeza da boca. Quando há diminuição do fluxo salivar, observa-se maior estagnação de matéria orgânica sobre a língua, como células epiteliais descamadas e bactérias, formando a Saburra Lingual. A degradação da Saburra Lingual pelas bactérias provoca a formação de compostos sulfurados voláteis que causam o mau hálito. Uma boa quantidade de saliva é um dos fatores importantes para manter o hálito agradável. Neste trabalho, vamos demonstrar a técnica de medição de saliva que utilizamos no Cecom para tratamento da Halitose. Para esta técnica, utilizamos um tubo de Proveta com medições, um tubete de silicone de 1,5 cm de comprimento e um cronômetro. O paciente deve mastigar o tubete de silicone, durante 5 minutos, e ir cuspindo toda a saliva que for sendo produzida para dentro do tubo de Proveta. Ao final dos cinco minutos, medimos a quantidade de saliva dentro do tubo e dividimos este valor por 5. Desta maneira, obtemos o fluxo salivar do paciente. Com a saliva dentro do tubo de Proveta, avaliamos os padrões salivares do paciente, como quantidade, coloração, turbidez e viscosidade. Se for encontrada alguma alteração, realizamos o tratamento adequado para reestabelecer os padrões normais, através de Sialogogos, que estimulam a produção da saliva de diversas maneiras.

Temperature phased anaerobic digestion of municipal sewage sludge: a Bardenpho treatment plant study

The disposal of waste sludge generated from wastewater treatment plants (WWTPs) is a growing problem worldwide, and contributes to over 50% of the operating costs of current WWTPs. In this study, temperature-phased anaerobic digestion (TPAD) and conventional (single-stage) mesophilic anaerobic digestion were investigated in order to determine the most beneficial process for the intended digester facility to be constructed for the fermented primary and secondary sludge from a Bardenpho type biological nutrient removal plant. This was accomplished by considering several operational control parameters for three different sludge retention times. This study has shown that the TPAD system had significant improvement in biogas and methane production; solids and organic removal; pathogen reduction and dewaterability over the conventional digestion. In terms of overall volatile sulphur compounds formation normalized per volatile solids added, no significant effects were observed between TPAD and control digester.

The effects of pH and copper on the formation of volatile sulfur compounds in Chardonnay and Shiraz wines post-bottling

The effects of pH and Cu2+ treatment on the formation of volatile sulfur compounds (VSCs) were investigated in Chardonnay and Shiraz wine samples. Four VSCs were significantly affected by pH, with lower wine pH associated with decreased hydrogen sulfide (H2S), methanethiol, dimethyl sulfide, and carbon disulfide concentrations. The effects of pH and Cu2+ on H2S formation from known precursor compounds were subsequently studied in a model wine system. In samples treated with cysteine and glutathione lower pH produced less H2S. Nanoparticle tracking analysis was used to study the effects of variable pH concentrations in a model system containing Cu2+, tartaric acid, and H2S. Differences in Cu2+–tartrate complexes particle size and concentration were measured as a function of pH and H2S addition, suggesting the type of complexes formed may affect the binding sites of Cu2+ available to catalyse the formation of VSCs such as H2S.