Acetaldehyde Concentrations Research Articles

Polycarbazole-multiwalled carbon nanotubes based nanocomposite: Synthesis, spectral, biocidal and Acetaldehyde sensing studies

We herein report the functionalization of multi-walled carbon nanotubes (MWCNT) via oxidation method using a concoction of concentrated H2SO4 and HNO3. The electrically conducting polycarbazole-multiwalled carbon nanotubes nanocomposite (PCz/MWCNT) has been prepared by in-situ oxidation polymerization of monomer of carbazole (Cz). Several spectral techniques like FTIR, SEM/EDS, TEM, XRD and TGA were used to characterize PCz/MWCNTs nanocomposite. The spectroscopic data ascertains a strong interaction between PCz and MWCNTs. The nanocomposite exhibits high thermal stability as compared to the pristine PCz. The nanocomposite demonstrated better electrical conductivity and isothermal stability with respect to DC electrical conductivity retention under normal conditions below 100°C. The PCz/MWCNT based sensor was designed for the detection of acetaldehyde. It was observed that the resistivity of the PCz/MWCNT enhances on exposure to acetaldehyde at 25°C, and showed a direct relationship between the response and concentration of acetaldehyde. Moreover, PCz and PCz/MWCNT were also tested for their plausible biocidal activity.

Comparison of MCFA and Other Methods of Terminating Alcohol Fermentation and Their Influence on the Content of Carbonyl Compounds in Wine.

This study deals with the effects of the use of a mixture of medium-chain fatty acids (MCFA) at the end of the alcohol fermentation process on the content of carbonyl compounds in wine. During the experiment, the effects of the addition of MCFA at doses of 10 and 20 mg/L were compared to the termination of alcohol fermentation using cross-flow filtration and chilling treatments. Individual carbonyl compounds were determined by HPLC analysis. The experiment showed that the addition of MCFA caused a reduction of the acetaldehyde content compared to the chilling process, and a reduction of the diacetyl content compared to cross-flow filtration. Throughout the experiment, a lower level of total carbonyl compounds was observed after the addition of MCFA.

Determination of formaldehyde and acetaldehyde levels in poly(ethylene terephthalate) (PET) bottled mineral water using a simple and rapid analytical method

A simple and rapid analytical method was developed for the determination of formaldehyde (FA) and acetaldehyde (AA) contents in water. FA and AA were derivatized by 2,4-dinitrophenylhydrazine in an LC vial for 20 min at room temperature, about 25 °C, and analyzed using LC–MS/MS. The calibration curve exhibited excellent linearity for FA and AA concentrations of 2–150 ng/mL. Recovery tests using ultra-pure water and commercially available PET-bottled mineral water samples showed good trueness and precision. We determined the FA and AA contents in 105 PET-bottled mineral water samples on the Japanese market using this method. FA was detected in 61% of the samples at levels from 2.6 to 31.4 ng/mL, while AA was detected in 68% at levels from 5.3 to 143.5 ng/mL. These results demonstrate that the concentrations of FA and AA in PET-bottled mineral water on the Japanese market have not changed significantly over the last decade.

Effect of Reaction Products on the PEFC Catalyst Ink Property and Catalyst Layer Quality

The catalyst layer (CL) is a critical component that determines the performance of proton exchange membrane fuel cells, and the production process of CL is important issue. A CL is fabricated from a catalyst ink mixed with platinum-supported carbon (Pt/C), ionomer solution, and a solvent. When the catalyst ink is coated on the sheet and dried, the CL is formed. By transferring the CL to the membrane, catalyst coated membrane can be made [1]. The process from the initial characteristics of the catalyst ink to the drying process determines the structure of CL and dominates the characteristics of the fuel cell. Thus, quality control of the catalyst ink is important to form a high performance and uniform CL [2].We have reported that alcohol oxidation reaction and condensation reaction, as catalyzed by platinum, occurred in the catalyst ink fabrication process [3]. Several reaction products, aldehydes, acids, and esters, were detected by gas chromatography mass spectrometry (GC/MS) [4]. In this study, concentration of those reaction products were measured quantitatively, and the effect of those reaction products on the catalyst ink property and CL quality was investigated.Catalyst ink was prepared by using the mixture of water and ethanol as a dispersant. We used platinum catalyst supported on carbon black and Nafion dispersion. The solvent was composed of ethanol and water. The weight ratio between ethanol and water was set to 46:54 or 60:40. Nonvolatile content was 10 wt%. Weight ratio between Nafion and the carbon support was 0.75. As a mixing process, a high-speed rotary type mixer was used, and mixing time was set to 10 min. The quantitative concentration of reaction products in each ink were analyzed by GC/MS. After concentration measurement, CL was fabricated using each ink. The crack formation was observed, and the correlation with the initial composition of the ink and the concentration of the reaction product was investigated.As a result of GC/MS, several reaction products (acetaldehyde, acetic acid, and ethyl acetate) were detected in the catalyst ink. Table 1 shows quantitative concentration of reaction products. Comparing the both catalyst inks, the concentration of acetaldehyde increased remarkably when the ethanol concentration increased. CLs were fabricated with using those catalyst inks and observed by microscope (Figure 1). There was no crack in the low ethanol concentration ink, and cracks occurred in the high ethanol concentration ink. Those results suggest that acetaldehyde may be a factor in causing cracks in the CL.To clarify the effect of acetaldehyde, acetic acid, and ethyl acetate on the crack formation in the CL, each substance was artificially added to the low ethanol concentration catalyst ink. In actual catalyst ink, it is considered that ethanol reacts to produce a reaction product. Therefore, in the modified catalyst ink, the amount of ethanol was reduced according to the amount of added substance. The CL was fabricated by using those catalyst ink and the observation results were shown in Figure 2. When the same amount of acetaldehyde contained in the high ethanol concentration catalyst ink was added, many cracks were generated in the CL. Several cracks occurred when ethyl acetate was added, but the required amount was significantly higher than the ethyl acetate concentration detected in the actual catalyst ink. No cracks were generated even if a large amount of acetic acid was added to the catalyst ink. These results indicate that the acetaldehyde is a factor of crack in the CL. It is considered that when the generated acetaldehyde exceeds a certain concentration in the catalyst ink, crack is caused in the CL. Acknowledgment: This study is based on the results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Chemical changes in thirdhand smoke associated with remediation using an ozone generator

Ozonation is a common remediation approach to eliminate odors from mold, tobacco and fire damage in buildings. Little information exists to: 1) assess its effectiveness; 2) provide guidance on operation conditions; and 3) identify potential risks associated with the presence of indoor ozone and ozonation byproducts. The goal of this study is to evaluate chemical changes in thirdhand smoke (THS) aerosols induced by high levels of ozone, in comparison with THS aerosols aged under similar conditions in the absence of ozone. Samples representing different stages of smoke aging in the absence of ozone, including freshly emitted secondhand smoke (SHS) and THS, were collected inside an 18-m3 room-sized chamber over a period of 42 h after six cigarettes were consumed. The experiments involved collection and analysis of gas phase species including volatile organic compounds (VOCs), volatile carbonyls, semivolatile organic compounds (SVOCs), and particulate matter. VOC analysis was carried out by gas chromatography/mass spectrometry with a thermal desorption inlet (TD-GC/MS), and volatile carbonyls were analyzed by on-line derivatization with dinitrophenylhydrazine (DNPH), followed by liquid chromatography with UV/VIS detection. SVOCs were extracted from XAD-coated denuders and Teflon-coated fiberglass filters in the absence of ozone. In those extracts, tobacco-specific nitrosamines (TSNAs) and other SVOCs were analyzed by gas chromatography with positive chemical ionization-triple quadrupole mass spectrometric detection (GC/PCI-QQQ-MS), and polycyclic aromatic hydrocarbons (PAHs) were quantified by gas chromatography with ion trap mass spectrometric detection (GC/IT-MS) in selected ion monitoring mode. Particulate matter concentration was determined gravimetrically. In a second experiment, a 300 mg h−1 commercial ozone generator was operated during 1 h, one day after smoke was generated, to evaluate the remediation of THS by ozonation. VOCs and volatile carbonyls were analyzed before and after ozonation. Extracts from fabrics that were exposed in the chamber before and after ozonation as surrogates for indoor furnishings were analyzed by GC/IT-MS, and aerosol size distribution was studied with a scanning mobility particle sizer. Ozone concentration was measured with a photometric detector. An estimated 175 mg ozone reacted with THS after 1 h of treatment, corresponding to 58% of the total O3 released during that period. Fabric-bound nicotine was depleted after ozonation, and the surface concentration of PAHs adsorbed to fabric specimens decreased by an order of magnitude due to reaction with ozone, reaching pre-smoking levels. These results suggest that ozonation has the potential to remove harmful THS chemicals from indoor surfaces. However, gas phase concentrations of volatile carbonyls, including formaldehyde, acetaldehyde and acetone were higher immediately after ozonation. Ultrafine particles (UFP, in most cases with size <60 nm) were a major ozonation byproduct. UFP number concentrations peaked shortly after ozonation ended, and remained at higher-than background levels for several hours. Based on these results, minimum re-entry times after ozone treatment were predicted for different indoor scenarios. Clearly defining re-entry times can serve as a practical measure to prevent acute exposures to ozone and harmful ozonation byproducts after treatment. This study evaluated potential benefits and risks associated with THS remediation using ozone, providing insights into this technology.

Abnormally High Blood Acetaldehyde Concentrations Suggest Potential Postmortem Ethanol Generation.

Ethanol is one of the most commonly used and abused substances worldwide. Identifying whether the source of ethanol detected in corpses is antemortem ingestion or postmortem generation is especially important for determining the cause of death, which remains a vibrant field of research. During the synthesis of ethanol in the putrefaction process of corpses, other small molecules such as acetaldehyde and n-propanol could also be produced. According to our prospective statistical analysis based on authentic samples from forensic cases, it is rational to suspect ethanol generation after death when the concentration of acetaldehyde detected in blood exceeds 0.014 g/dL. Through in vitro simulation experiments, in addition to confirming that ethyl glucuronide and ethyl sulfate are the reliable biomarkers of antemortem ingestion of ethanol, we propose that acetaldehyde is far more sensitive than n-propanol as a potential marker in the blood of corpses for postmortem ethanol formation.

The role of wet fermentation in enhancing coffee flavor, aroma and sensory quality

This study investigates the impact of wet fermentation on flavor volatiles and sensory quality of coffee beans and beverage. Pulped coffee beans were kept underwater for 36 h before air-drying and roasting, and volatiles in the beans were characterized by solid-phase microextraction and gas chromatography–mass spectrometry. A total of 79 volatiles were identified. Fermented roasted beans had higher concentrations of ethanol, isoamyl alcohol, 3-methylbutanal, benzaldehyde, acetaldehyde, and ethyl acetate compared with mechanically processed (no fermentation) beans; whereas, ketones, pyrazines, pyrroles, pyridines, furans and sulfides were not significantly different between the two treatments. Coffee made with fermented beans was rated significantly higher in flavor, aroma, acidity, body and uniformity scores with noted fruity aroma compared with beverage made with mechanically processed beans in sensory evaluation (cup test) by a 3 Q-Grade Coffee Certification Panel. The findings demonstrated wet fermentation played an important role in coffee flavor, aroma and sensory quality.

Synthesis of Ligustrazine from Acetaldehyde by a Combined Biological-Chemical Approach.

Ligustrazine is an important active alkaloid in medicine and in the food industry. Here, we developed a combined biological-chemical approach to produce ligustrazine from acetaldehyde. First, we constructed a whole-cell biocatalytic system to produce the precursor acetoin from acetaldehyde by overexpressing formolase (FLS). Second, a two-step strategy was developed to enhance protein expression of FLS by codon usage optimization at the first 14 codons and the introduction of an overlapping gene before the start codon. Through expression optimization and directed evolution of FLS, we improved the titer of acetoin about 40 fold when the concentration of acetaldehyde was 1.5 M. Finally, after reaction conditions optimization, the titer of acetoin and ligustrazine reached 222 g L-1 and 94 g L-1, with a 86.5% and 48% conversion rate from acetaldehyde, respectively. The developed one-pot synthesis for acetoin and ligustrazine is expected to be applied to industrial production in the future with the advantages of a green process, high efficiency, and low cost.

Contribution of mobile sources to secondary formation of carbonyl compounds

ABSTRACT In the 2014 National Air Toxics Assessment (NATA), the carbonyl compounds formaldehyde and acetaldehyde were identified as key cancer risk drivers and acrolein was identified as one of the three air toxics that drive most of the noncancer risk. In this assessment, averaged across the Continental United States, about 75% of ambient formaldehyde and acetaldehyde, and about 18% of acrolein, is formed secondarily. This study was conducted to estimate the potential contribution to these secondarily formed carbonyl compounds from mobile sources. To develop such estimates, we conducted several CMAQ runs, where emissions are set to zero for different mobile source sectors, to determine their potential contribution. Although zeroing out emissions from an individual sector can offer only a rough approximation of how the sector might contribute to overall secondary concentrations, our results suggest that across the U. S., mobile sources contribute about 6–18% to secondary formaldehyde, 0–10% to secondary acetaldehyde, and 0–70% to secondary acrolein, depending on location. Implications: Photochemical modeling of carbonyl compounds was conducted with emissions set to zero for various mobile source sectors to determine their contribution to secondary concentrations. Results indicated mobile sources contributed to total and secondary concentrations of formaldehyde, acetaldehyde, and acrolein in many locations across the U.S. with acrolein the dominant contributor in some locations. However, biogenic sources dominated secondary formaldehyde and acetaldehyde, and fires dominated secondary acrolein.

The study of the main impurities mature mash depending on the duration of fermentation, yeast alcohol race and used enzyme preparations

The paper studied the process of intensification of concentrated fermentation mash with account of the complex amylolytic enzymes, hemicellulase and proteolytic activities. We determined the dependence of ethanol yield, the content of volatile impurities, the content of reducing substances, depending on the different strains of yeast at a seed rate 15 million cells per 1 cm3 wort. To identify the parameters of the fermentation process the wort with an increased solids content, investigated the dynamics of accumulation of volatile impurities by varying the rate and duration of seeding yeast fermentation using 987-O5 race yeast. It revealed that the qualitative composition of impurities in the mash, the resulting wort of high-concentration depends both on the duration of fermentation, and from normal seeding yeast. Thus, depending on the duration of the fermentation process, the acetaldehyde content increases (from 613,17 mg/dm? to 54 h to 1724,6 mg/dm? to 72 hours), the amount of ethyl acetate is reduced (from 409,2 mg/dm? to 54 hours prior to 207 mg/dm? to 72 hours), the methanol content to 54 h at a rate of 15 million yeast seeding cells per 1 cm? of the wort amounted to 0,0043 mg/cm?, whereas by 72 h of fermentation at the same seed rate yeast – 0,0070 mg/dm?, the amount of 1-propanol and 1-butanol was reduced from 903,14 mg/cm? and 6,38 mg/cm? -54 h to 880 mg/cm? and 5,57 mg/cm? - to 72 hours, respectively. The minimum content of isobutanol independent of the duration of fermentation was 900-1100 mg/cm? at a seed rate 15 million yeast cells per 1 cm? wort izoamilola number increases from 1219,08 mg/dm? (54 hr) to 2673,84 mg/dm? (72 h). It revealed that the smallest total amount of impurities obtained by seed rate yeast 15 million cells per 1 cm? wort at the duration of fermentation 54 hours was found that maximum ethanol content in the mash with minimal accumulation therein volatiles corresponds embodiment:. Duration of fermentation - 54 hours at normally the problem of yeast cells – 15,0 million / cm? wort.

The Impact of Chitosan on the Chemical Composition of Wines Fermented with Schizosaccharomyces pombe and Saccharomyces cerevisiae.

This study investigates the influence of the antimicrobial agent chitosan on a selected Schizosaccharomyces pombe strain during the alcoholic fermentation of ultra-pasteurized grape juice with a high concentration of malic acid. It also studies a selected Saccharomyces cerevisiae strain as a control. The study examines several parameters relating to wine quality, including volatile and non-volatile compounds. The principal aim of the study is to test the influence of chitosan on the final chemical composition of the wine during alcoholic fermentation, and to compare the two studied fermentative yeasts between them. The results show that chitosan influences the final concentration of acetic acid, ethanol, glycerol, acetaldehyde, pyruvic acid, α-ketoglutarate, higher alcohols, acetate esters, ethyl esters, and fatty acids, depending on the yeast species.

Effect of hypobaric treatment on off-flavour development and energy metabolism in ‘Bruno’ kiwifruit

Kiwifruit (Actinidia deliciosa cv. Bruno) can more easily acquire ‘alcoholic flavour’ due to the accumulation of ethanol under normal ripening conditions compared to the other cultivars of kiwifruit. In this study, the effects of hypobaric treatment (25 ± 5 kPa for 30 min) one time (T1) and two times (T2) on fruit quality, ethanol metabolism and energy metabolism in ‘Bruno’ kiwifruit were investigated during room temperature storage. The results showed that T2 treatment effectively reduced fruit decay and weight loss during the whole storage period, and both T1 and T2 treatments maintained higher values of total phenolic, quinic acid and citric acid than CK during the late stage of storage. Moreover, the hypobaric treatments reduced alcoholic flavour development, while T2 treatment was more effective than T1 treatment. The mechanism for this effect might involve two aspects. On the one hand, T2 treatment enhanced aerobic metabolism by increasing the energy level and the activities of succinic dehydrogenase (SDH), cytochrome c oxidase (CCO) and H+-adenosine triphosphatase (H+-ATPase) during the late stage of storage. On the other hand, T2 treatment inhibited anaerobic metabolism by decreasing the concentrations of acetaldehyde and ethanol and the activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH). In conclusion, we speculated that the effect of hypobaric treatment on ‘Bruno’ kiwifruit might be involved in the regulation of aerobic and anaerobic metabolisms during storage at room temperature.

Simultaneous determination of acetaldehyde, ethyl acetate, methanol, iso butanol, and iso almyacol concentrations in white alcol in some areas in Hai Duong province in 2018 - 2019

The research has developed a method for simultaneous determination of acetaldehyde, ethyl acetate, methanol, isobutyl alcohol, isoamyl alcohol in white alcohol. Validation results show that the method has satisfactory accuracy with recovery in the range of 105 - 108%, repeatability RSD &amp;lt; 1.57%, detection limit below 3 mg/L for all compounds. Proficiency test results in 2020 were satisfactory with Z-scores of all substances below 2. The method has been applied to analyze 200 distilled alcohol samples and 50 blended alcohol samples taken in Hai Duong city during the period from 2018 to 2020. Three of 200 distilled alcohol samples have the methanol content higher than the maximum limit. The relationship between methanol content in proportion to content of acetaldehyde, ethyl acetate, isobutyl alcohol, and isoamyl alcohol in the same sample has been evaluated to distinguish between blended alcohol and distilled alcohol.

Performance of an air purifier using a MnOx/TiO2 catalyst-coated filter for the decomposition of aldehydes, VOCs and ozone: An experimental study in an actual smoking room

To develop an air purifier for a smoking room, an ozone (O3) decomposition manganese catalyst, capable of the oxidative decomposition of the volatile organic compounds (VOCs) in tobacco smoke, was applied in this study. The actual concentration of the total VOCs (TVOCs) that was measured in a smoking room was ~2,000 μg m−3, toluene, benzene, and acetaldehyde were also obtained in high concentrations.An O3 oxidative decomposition catalyst, MnOx/TiO2, synthesized by chemical vapor condensation (CVC) (MnOx/CVC-TiO2) was subjected to decomposition experiments, at room temperature (25 °C), utilizing acetaldehyde as the target material. The catalyst-coated filter was installed as a fixed bed, and after supplying O3, at a concentration of 25 ppm, it was confirmed that the catalyst had facilitated the complete decomposition of 10 ppm of acetaldehyde. Next, a decomposition experiment was conducted for TVOCs with a prototype smoke purifier, which employed the catalyst-coated filter, in a 1-m3 bench-scale chamber. The initial concentration of TVOC, 4,300 μg m−3, was reduced to 171 μg m−3 after 30 min (treatment efficiency, 96%). Finally, the treatment performance of the practical smoke purifier was tested in a real smoking room (61.9 m3). The initial TVOC concentration was reduced from 2,229 to 493 μg m−3 after 30 min with a removal efficiency of 80%. Moreover, ~70% of the acetaldehyde concentration was also decomposed.

Continuous aldehydes monitoring in primary schools in France: Evaluation of emission sources and ventilation practices over 5 weeks

This paper presents a field campaign conducted in two French elementary schools for 5 weeks aiming at identifying effects of occupation and ventilation practices on indoor aldehyde concentrations and discriminating aldehyde emission from building materials and furniture. The investigated classrooms were first empty and not occupied whereas the furniture was added the following week. Normal school activities were restarted for the last three weeks under various ventilation practices.C2–C7 aldehydes concentrations were monitored with the conventional method based on DNPH derivatization using active sampling followed by off-line HPLC/UV analysis. Acetaldehyde (AA) and hexanal (HA) were the two main aldehydes present if formaldehyde is not considered. The weekly mean values of acetaldehyde concentrations were found in the range 9.5–13.1 μg m−3 (School 1), 9.4–17.6 μg m−3 (School 2) and equal to 5.3 μg m−3 (School 3). In Schools 2 and 3, weekly hexanal concentrations ranged between 3.3 and 5.4 μg m−3 but increased up to 40.1 μg m−3 in school 1 where painting work was performed during the week 2. Smaller amount of propionaldehyde (PA) and benzaldehyde (BA) were always detected, their weekly average concentrations being in the range 0.4–4.0 μg m−3 and 0.9–2.7 μg m−3 for PA and BA, respectively. The results supported by Student's tests show that building materials and furniture contribute to aldehyde emissions while ventilation significantly improves indoor air quality without being able to privilege one of the three ventilation scenarios tested.

Effects of the pre-fermentative addition of chitosan on the nitrogenous fraction and the secondary fermentation products of SO2 -free red wines.

Different red winemaking were carried out to evaluate the effects of the prefermentative addition of chitosan, as an alternative to the use of SO2 , on the secondary products of alcoholic fermentation, yeast available nitrogen (YAN), biogenic amines and ethyl carbamate. The wines made with chitosan presented higher total acidity and higher content of tartaric and succinic acids than those made only with SO2 . The use of chitosan in winemaking resulted in wines with higher glycerol and diacetyl content without increasing the concentration of ethanol, acetic acid, acetaldehyde or butanediol. YAN was lower in wines made with chitosan, which may mean an advantage for the microbial stability of the wines. Furthermore, the use of chitosan at the beginning of alcoholic fermentation did not increase the concentration of biogenic amines or the formation of ethyl carbamate in SO2 -free red wines. The total or partial substitution of SO2 for chitosan at the beginning of the alcoholic fermentation gives rise to quality red wines without negatively affecting their nitrogen fraction or their very important secondary fermentation products such as acetic acid or acetaldehyde. © 2020 Society of Chemical Industry.

Suppressive Effect of Shiitake Extract on Plasma Ethanol Elevation.

Alcohol is usually consumed with meals, but chronic consumption is a leading cause of alcoholic liver diseases. We investigated if shiitake extracts with a high lentinic acid content (Shiitake-H) and without lentinic acid (Shiitake-N) could suppress the elevation in plasma ethanol concentrations by accelerating ethanol metabolism and preventing ethanol absorption from the gut. Shiitake-H and Shiitake-N suppressed the elevation in concentrations of ethanol and acetaldehyde in plasma, and promoted the activities of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) in the liver. However, these effects of Shiitake-H were more prominent than those of Shiitake-N. Furthermore, Shitake-H promoted ADH and ALDH activities in the stomach. We also examined the change in plasma ethanol concentration by injecting Shiitake-H or Shiitake-N into the ligated loop of the stomach or jejunum together with an ethanol solution. Shiitake-H suppressed the absorption of ethanol from the stomach and jejunum. In conclusion, Shiitake-H accelerates ethanol metabolism in the stomach and liver and inhibits ethanol absorption in the stomach and jejunum indicating that lentinic acid is a functional component in shiitake.

Effect of Lactobacillus rhamnosus on Physicochemical Properties of Fermented Plant-Based Raw Materials.

Texture and flavor are currently the main challenges in the development of plant-based dairy alternatives. To overcome them, the potential of microorganisms for fermentation of plant-based raw materials is generating great interest in the food industry. This study examines the effect of Lactobacillus rhamnosus, LGG® (LGG® is a trademark of Chr. Hansen A/S) on the physicochemical properties of fermented soy, oat, and coconut. LGG® was combined with different lactic acid bacteria (LAB) strains and Bifidobacterium, BB-12® (BB-12® is a trademark of Chr. Hansen A/S). Acidification, titratable acidity, and growth of LGG® and BB-12® were evaluated. Oscillation and flow tests were performed to analyze the rheological properties of fermented samples. Acids, carbohydrates, and volatile organic compounds in fermented samples were identified, and a sensory evaluation with a trained panel was conducted. LGG® reduced fermentation time in all three bases. LGG® and BB-12® grew in all fermented raw materials above 107 CFU/g. LGG® had no significant effect on rheological behavior of the samples. Acetoin levels increased and acetaldehyde content decreased in the presence of LGG® in all three bases. Diacetyl levels increased in fermented oat and coconut samples when LGG® was combined with YOFLEX® YF-L01 and NU-TRISH® BY-01 (YOFLEX® and NU-TRISH® are trademarks of Chr. Hansen A/S). In all fermented oat samples, LGG® significantly enhanced fermented flavor notes, such as sourness, lemon, and fruity taste, which in turn led to reduced perception of the attributes related to the base. In fermented coconut samples, gel firmness perception was significantly improved in the presence of LGG®. These findings suggest supplementation of LAB cultures with LGG® to improve fermentation time and sensory perception of fermented plant-based products.

ASSESSMENT OF DURABILITY AND CHARACTERISTICS OF CHANGES IN KEFIR MADE FROM COW'S AND GOAT'S MILK

Present study was aimed to determine the changes and the best consumption time of kefir samples made from cow and goat milk using starter culture during the storage at the refrigerator (+4°C for 35 days). It was found that goat kefir (GK) samples had higher pH and lipolysis values during storage while cow kefir (CK) samples had higher values of viscosity. The counts of lactococci, lactobacilli, leuconostoc, total mesophilic aerobic bacteria, acetic acid bacteria and yeast decreased during the storage. Amounts of lactic, acetic, citric, pyruvic and oxalic acids were higher in GK samples. Acetaldehyde, diacetyl and acetoin contents were higher in CK samples. The highest sensory scores were obtained for CK samples on 14th day and for GC sample on 21th day of the storage.

Investigation of potential strategies to control malt-induced premature yeast flocculation

Premature yeast flocculation (PYF) during beer fermentation is an undesired event by which yeast flocculate too early and heavily before the wort nutrition is exhausted. While PYF can be a major financial detriment to brewers, the conditions that trigger it and the chemical composition of PYF are poorly understood. Gas chromatography–mass spectrometry results from this study indicated that purified malt PYF factor consisted of numerous polysaccharides; however, no protein was identified. High concentrations of PYF promoted further yeast flocculation, which in turn decreased the rate of fermentation and increased acetaldehyde content of the beer. PYF factors were found to be derived primarily from malt husks and factors such as microbial content of the water used for germination, mixing malts with different PYF values, and presence of tannic acid were all found to influence the rate of yeast flocculation. Findings from this study may be beneficial in developing PYF prevention and control measures that can be applied to future brewing strategies.