Amount Of Volatile Compounds Research Articles

Research on microbial diversity and nutritional flavor formation of Xianju wheat paste

AbstractBACKGROUNDXianju wheat paste, a traditional condiment in Hubei Province, China, possesses nutritional value and a distinctive taste profile. Nevertheless, there remains a dearth of comprehensive comprehension regarding the intricate interplay between the microbial population and its nutritional profile in Xianju wheat paste.RESULTSIt was determined that Xianju wheat paste harbors predominant microbial genera such as Bacillus, Staphylococcus and Aspergillus. The findings from high‐throughput sequencing analysis revealed the presence of 11 bacterial genera in Xianju wheat paste, with relative abundances exceeding 1%. These genera included Bacillus, Staphylococcus, Brevibacterium, Lactobacillus, Allorhizobium‐Neorhizobium‐Pararhizobium‐Rhizobium, Enterobacteriaceae, Pantoea, Brachybacterium, Klebsiella, Escherichia‐Shigella and Ochrobactrum. Furthermore, six fungal genera were identified with relative abundances greater than 1%, specifically Aspergillus, Zygosaccharomyces, Cutaneotrichosporon, Candida, Millerozyma and Rhizopus. The correlation analysis indicated a significant impact of the microbial community and nutritional flavor on the second phase of fermentation in Xianju wheat paste. The predominant bacterium Bacillus in Xianju wheat paste facilitated the production of free amino acids, whereas Staphylococcus exhibited a negative correlation with free amino acid levels. The quantity of volatile compounds in Xianju wheat paste progressively increased during fermentation, with the presence of typical aroma compounds 4‐vinyl‐2‐methoxyphenol significantly associated with Bacillus. This indicated Bacillus notably enhanced the production of aromatic substances. Furthermore, a strong correlation was observed between Staphylococcus and the 18 volatile organic compounds, highlighting their substantial contribution to these aroma compounds.CONCLUSIONThis research indicates that the presence of microbial communities significantly contributes to the development of the nutritional flavor profile in Xianju wheat paste. © 2024 Society of Chemical Industry.

Volatile organic contaminants in HDPE milk bottles along the mechanical recycling value chain, revealing origins and contamination pathways

To progress towards closed-loop recycling of plastic packages it is vital to understand the origin of contaminants and to develop effective mitigation strategies. High density polyethylene (HDPE) milk bottles were sampled at nine different locations along the recycling value chain and analysed with two gas chromatography – mass spectroscopy methods to study the presence of volatile organic compounds. The total approximated concentration of volatiles reduced over time from the production of the bottles up to the cross-docking facility for the separately collected lightweight packaging waste (from about 250 to 100 ppm), as alkanes and alkenes evaporate from the bottle. A clear maximum was observed in the number of identified of volatiles and in the total approximated concentration in milk bottles at the sorted HDPE product. Here contaminants peaked that originate from the milk, from other packaging components (labels, caps, inlays), from other packages and from the surrounding atmosphere. When only the milk bottles were manually separated out from this sorted product and these were mechanically recycled, flakes were obtained that contain the least amount of volatile compounds, much less than the freshly produced bottles (about 25–50 ppm). The type of volatiles present was, however, markedly different. In the freshly produced bottles alkanes, alkenes and intentionally added anti-oxidant were found, whereas in the recycled flakes mostly contaminants were found that originated from: the milk, the other packaging components, other packages and the surrounding atmosphere. Seven different contamination pathways were discerned. The gathered knowledge facilitates the future development of food-grade recycled HDPE.

Investigation into the use of novel pretreatments in the fermentation of Alaria esculenta by Lactiplantibacillus plantarum and kombucha SCOBY

High pressure processing (HPP), ultrasound probe (USP) and ultrasound bath (USB) were applied to Alaria esculenta as a fermentation pre-treatment. Seaweed was then fermented by Lactiplantibacillus plantarum (LAB) or symbiotic culture of bacteria and yeast (SCOBY). Physiochemical properties of fermented seaweed were measured. pH was significantly different (p < 0.05) across SCOBY-fermented samples with different pre-treatments but not LAB-fermented samples (p > 0.05). There was a significant difference (p < 0.05) in total viable count (TVC) with the highest count in HPP-treated samples, and lowest in control samples. Organic acids differed significantly (p < 0.05) across pre-treatments for both fermentation groups. 27 volatile compounds were detected in the samples, with alcohols and ketones the most prominent groups. The quantity of volatile compounds was not significantly lower (p > 0.05) from seaweed powder. The control sample had the highest levels of tropomyosin (15.92 mg/kg) followed by HPP samples.

The impact of different drying methods on the physical properties, bioactive components, antioxidant capacity, volatile components and industrial application of coffee peel.

This study evaluated the effects of hot air drying (HAD), microwave drying (MD), vacuum drying (VD), sun drying (SD) and vacuum freeze drying (VFD) on the physical properties, bioactive components, antioxidant capacity, volatile components and industrial application of coffee peel. The results showed VFD could retain the appearance color, total phenolics (19.49 mg GAE/g DW), total flavonoids (9.65 mg CE/g DW), caffeine (3.15 mg/g DW), trigonelline (2.71 mg/g DW), and antioxidant capacities of fresh sample to the greatest extent, but its operating cost was significantly higher than other treatments and total volatile components were in the minimum levels. HAD and SD exhibited the highest loss rates of total phenols and antioxidant capacities, exceeding 50%. MD offered the lowest operating cost, superior retention of bioactive components, and the richest variety and quantity of volatile compounds. Therefore, it is recommended to use MD to dehydrate the coffee peel in actual production.

Effects of freezing methods on physicochemical properties, protein/fat oxidation and odor characteristics of surimi gels with different cross-linking degrees

This work investigated the effects of liquid nitrogen immersion freezing (LNF), −35 °C air freezing (AF-35℃) and −18 °C air freezing (AF-18℃) on the physical and chemical characteristics and flavor quality of surimi gels with different cross-linking degrees. Compared to AF-35 °C and AF-18 °C, LNF was shown to considerably delay the texture deterioration and water migration of frozen gels, as well as the accumulation of thiobarbituric acid reactive substance values and carbonyl contents. Additionally, an appropriate increase of cross-linking degree (45.83 to 62.99%) was found able to improve gel properties and inhibit quality deterioration during freezing. Moreover, LNF-treated gels were closer to fresh gels in the amount of volatile compounds, in contrast to most significant negative aroma changes in AF-18℃-treated gels. Furthermore, 29, 29 and 31 key differential volatile compounds were screened for gels with a cross-linking degree of 29.66, 45.83 and 62.99%, respectively, mainly including aldehydes, alcohols and esters.

DLLμE/GC-MS as a Powerful Analytical Approach to Establish the Volatilomic Composition of Different Whiskeys

The volatilomic fingerprint of nine different whiskeys was established using a rapid and sensitive analytical approach based on dispersive liquid–liquid microextraction (DLLμE) followed by gas chromatography mass spectrometry detection (GC-MS) and gas chromatography with flame ionization detection (GC-FID). The influence of the extractor solvent on the extraction efficiency of volatile compounds (VOCs) was evaluated by DLLμE/GC-MS. The highest amounts of VOCs were obtained using 5 mL of sample, dichloromethane as the extractor solvent, and acetone as the disperser solvent. The proposed method showed no matrix effect, good linearity (R2 ≥ 0.993) in the assessed concentration range, recovery (ranging from 70 to 99%, precision (RSD ≤ 15%) and sensitivity (low limits of detection and quantification). A total of 37 VOCs belonging to different biosynthetic pathways including alcohols, esters, acids, carbonyl compounds, furanic compounds and volatile phenols were identified and quantified using DLLμE/GC-MS and DLLμE/GC-FID, respectively. Alcohols (3-methylbutan-1-ol, propan-1-ol), esters (ethyl decanoate, ethyl octanoate, ethyl hexanoate), and acids (decanoic acid, octanoic acid, hexanoic acid) were the most abundant chemical families. The multivariate statistical analysis allowed for the discrimination of whiskeys based on their volatilomic fingerprint, namely octanoic acid, 2-furfural, ethyl octanoate, ethyl hexanoate, acetic acid, ethyl dodecanoate, butan-1-ol, and ethyl decanoate.

Characterization of Volatile Flavor Compounds in Supercritical Fluid Separated and Identified in Gurum (Citrulluslanatus Var. colocynthoide) Seed Oil Using HSME and GC-MS.

In this study, the volatile compound profiles of gurum seed oil were determined using two methods: supercritical CO2 extraction (SFE) and the screw press process (SPP). For volatile compounds extraction and identification, headspace solid-phase micro-extraction (HS-SPME) and GC–MS were used, respectively. A total number of 56 volatile compounds were revealed and identified in oil extracted by SFE, while only 40 compounds were detected in extracted oil by SPP. Acids, aldehydes, esters, ketones, furans, and other components were present in the highest ratio in oil extracted by SFE. In contrast, alcohols and alkenes were found in the highest proportion in oil extracted by SPP. In this study, it was observed that SFE showed an increase in the amounts of volatile compounds and favorably impacted the aroma of gurum seed oil. The results reveal that different extraction methods significantly impact the volatile components of gurum seed oil, and this study can help evaluate the quality of the oil extracted from gurum seeds.

Using Smoke Condensed Liquids from Pruned Fruit-Tree Branches for Aedes Mosquito Larva Control

Some mosquitos are disease-causing vectors. Their widespread existence poses a great threat to disease control worldwide. Finding an effective, low-cost solution for mosquito population control is desperately needed. Pruned branches from three fruit trees of date, pomelo, and guava were chopped, dried, and smoldered to form biochar and smoke. The smoke was condensed at 6 °C to form a smoke condensed liquid (SCL) to be used as a larvicide for mosquito larva control. The SCL had a smoky smell, minimal nutrients, and little metal contents, yet contained plenty of phenolic molecules commonly used as biocides. Via bacterial inhibition zone tests, ten percent of the date, pomelo, and guava SCLs had 1.44, 1.13, and 0.83 times higher bactericidal effects, respectively, than the use of 75% ethanol. The effectiveness of bacterial inhibition was positively related to the amounts of volatile compounds in the SCL liquids. As for larvicidal effects, a ten percent solution of the date and pomelo SCLs killed all tested larvae within 2 hrs. The reactive time versus each SCL’s LC50 was determined and fitted with a first-order mathematic model. The adopted model and its estimated parameters showed satisfactory results in presenting the dose–effect relationships in larval mortality of all the tested SCLs. Finally, the liquid pHs and dissolved oxygen (DO) over time were examined for their effectiveness and variation, respectively, and the SCL addition was concluded as the sole key factor in the mortality of the tested larvae.

Physicochemical properties, and volatile compounds of blackened jujube vinegar as prepared by optimized fermentation process

ABSTRACT Response surface methodology was used to optimize the fermentation factors of blackened jujube vinegar (BJV). Physicochemical properties, antioxidant activity, sensory evaluation, and volatile compounds were studied with the methods of high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results indicated that the optimal fermentation conditions was the acetic acid inoculation amount of 15%, the fermentation temperature of 30.44°C, and the initial alcohol content of 6.45% vol. During fermentation processing, there was a delay in the start of BJV fermentation and the fermentation rate was lower than red jujube vinegar (RJV). There was a significant difference in cyclic adenosine monophosphate (cAMP) content between these two (P < .05), and BJV is 3.55 times that of RJV. The content of polysaccharides in BJV and RJV decreased significantly and the trend was the same. The 5-Hydroxymethylfurfural (5-HMF) content of BJV decreased rapidly with the process and reached a very low level finally. The antioxidant activity of BJV was significantly higher than that of RJV in terms of 2,20 -azinobis (3-ethylbenzothiazoline6-sulfonicacid) (ABTS) and ferric reducing antioxidant power (FRAP) (P < .05). From sensory evaluation, the aroma and taste of BJV were better than those of RJV. There were no significant differences in the categories and quantities of volatile compounds between them. Volatile acid of BJV was less than that of RJV with the value of 72.91% and 81.15%, respectively, meanwhile, volatile esters of BJV (19.11%) was significantly higher than that of RJV (9.28%), for these reasons, sensory of BJV was softer, richer ester fragrance, and RJV was more stimulating.

Influence of the stretching temperature on the volatile compounds and odour intensity of high moisture mozzarella: A model study

The impact of the stretching phase on the volatile compounds (VOC) and odour intensity of high moisture mozzarella was investigated. Three trials were done using raw milk with different microbiological quality for the preparation of control and aseptic (sodium azide) cheeses at two different stretching temperatures. The SPME-GC/MS analysis showed that stretching caused a decrease of VOC from curd to cheese in the aseptic samples due to volatilisation or solubilisation into the stretchwater. It was not observed in the control mozzarella due to the formation of microbial-derived VOC during the cooling phase. The samples stretched at 70 °C had the highest amount of VOC, except for those made from high quality milk. The formation of new VOC due to stretching remained doubtful. The control samples stretched at 70 °C had the highest odour intensity, whereas stretching at 90 °C resulted in a more intense odour in the aseptic cheeses.

The study of volatile compounds of the raw material of immortelle (Helichrysum bracteatum)

Topicality. Plants during their life cycle synthesize, accumulate and release volatile compounds into the environment. Volatile compounds are substances that are heterogeneous in structure and chemical properties, and belong to different classes of compounds. These substances can have saturated and unsaturated, linear and branched chains and cyclic fragments. They can also contain various functional groups: hydroxyl, ether, carboxyl, etc. Substances of the terpenes class occupy a special place among volatile compounds. Many substances related to volatile compounds are commercially important. This fact determines the commercial value of any plant and the prospects of its pharmacognostic research. The study of the composition of volatile compounds will allow us to assess the prospects of further study of a particular plant. With the steadily increasing demand of the pharmaceutical industry for the medicinal plant raw material, and the need to search for new medicinal products based on medicinal plants, special attention should be paid to plants that have a widely represented raw material base. Immortelle (Helichrysum Bracteatum) is such a promising plant. The preliminary phytochemical studies have found that the raw material of immortelle has a diverse composition of biologically active substances.Aim. To study the composition of volatile compounds of immortelle herb and flowers.Materials and methods. As the study object the crushed raw of immortelle was used. The study of volatile compounds was performed on an Agilent 6890N/5973 inert chromatography-mass spectrometric system (Agilent Technologies, USA); the carrier gas was helium.Results and discussion. As a result of the study conducted, 26 volatile compounds were identified in the herb of immortelle, 39 compounds in the flowers of immortelle. Identification was carried out using the mass spectra library NIST 02, WILEY 2007, as well as AMDIS and NIST identification programs. When determining the share of each of the substances identified in the total amount of volatile compounds it was found that the main volatile compounds in the herb of immortelle were n-hexadecanoic acid (44.48 %), phytol (13.71 %), 9.12-octadecanoic acid (11.21 %) and decamethyltetrasiloxane (8.55 %). The main volatile compounds in the flowers were n-hexadecanoic acid (43.83 %), 9.12-octadecanoic acid (19.52 %), the methyl ester of 7.10.13-hexadecatrienoic acid (8.85 %) and tetradecanoic acid (6.10 %). The remaining compounds identified were in significantly smaller amounts. Their share was 22.05 % in the herb, and 21.70 % in the flowers. Conclusions. For the first time, the study of the qualitative composition of volatile compounds in the herb and flowers of immortelle has been conducted using gas chromatography with mass spectrometric detection. The results of the study of volatile compounds of the raw material of immortelle, as well as according to the studies conducted earlier on the content of substances of other classes, indicate the prospect of further research of immortelle as an object for the development of new drugs.

Volatile constituents and ellagic acid formation in strawberry fruits of selected cultivars

Strawberries (Fragaria × ananassa Duch.) are considered a functional food and pleasing fruit in China, mainly because of their high concentration of ellagic acid (EA) and their aroma. A total of 127 volatile compounds were identified by HS–SPME–GC–MS. Changes in volatile constituents and EA were investigated in 50 strawberry cultivars in the red-ripening stage and in 6 cultivars, including ‘Benihoppe’, ‘Snow White’, ‘Yanli’, ‘Kaorino’, ‘Tokun’, and ‘Xiaobai’, at four developmental stages. The results indicated that the components and amounts of volatile compounds and EA markedly varied among and within cultivars. Through multivariate statistical analysis of the volatile compounds, 50 cultivars were divided into 4 clusters. Aromatic components that affected the cluster formation of cultivars were detected. Volatile compounds varied quantitatively among the 6 varieties during the developmental stages, and distinct changes were observed in both red-turning fruits and red-ripening fruits compared with white fruits. Except for ‘Xiaobai’, which showed the highest EA content at the red-ripening stage, the other 5 cultivars exhibited the highest EA level at the large green fruit stage. Partial least squares–discriminant analysis (PLS–DA) of the profiles of volatile compounds indicated that large green fruits were characterized by EA and aldehydes; white fruits were characterized by ketones and alkanes; and red-ripening fruits were characterized by esters, acids, furans, and alcohols. The results contribute new and important information to breeding programs and the desirable cultivation of strawberry production.

Single-Laboratory Validation of a Gas Chromatographic Method of Direct Determination of Volatile Compounds in Spirit Drinks: Need for an Improved Interlaboratory Study.

Background: The quality and safety control of an alcoholic drink is mainly the establishment of its chemical content, particularly the quantity of volatile compounds. Objective: A single-laboratory validation of a gas chromatographic method of direct determination of volatile compounds in spirit drinks was conducted. The discussed method applies ethanol, the major volatile component of an alcoholic beverage, as an internal standard. Possible algorithms of method validation based on interlaboratory study were proposed and described. Methods: Seven standard solutions of the following volatile compounds were prepared gravimetrically in 40% (v/v) water-ethanol solution: acetaldehyde, methyl acetate, ethyl acetate, methanol, 2-propanol, 1-propanol, isobutanol, 1-butanol, and isoamylol. Each sample was measured with the proposed method 30 times in repeatability conditions. Results: Flame ionization detector response was linearly correlated with assigned concentrations at a range of 2 to 5000 mg/L of absolute alcohol (AA) with coefficients of determination (R²) more than 0.995 for all analyzed components. Repeatability (RSDr ≤ 4.5%; RSDr ≤ 2.0%), reproducibility (RSDR ≤ 5.0%; RSDR ≤ 2.0%), and trueness (relative bias ≤ 2.6%; relative bias ≤ 1.4%) were obtained for low (10-25 mg/L AA for methanol and 2-10 for other volatiles) and high (25-5000 mg/L AA for methanol and 10-5000 for other volatiles) ranges of concentrations, correspondingly. Conclusions: The method increases the reliability of measurements and eliminates manual procedures of internal standard addition into both calibration standard solutions and spirit drinks.

Characterization of Aroma-Active Compounds in Seed Extract of Black Cumin (Nigella sativa L.) by Aroma Extract Dilution Analysis

Turkish Nigella sativa L. seed extracts were used to detect the aroma and key odorant compounds of the spice using gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Volatile compounds were extracted by the purge and trap extraction (PTE) method. A total of 32 volatile compounds consisting of different chemical classes acids (13), alcohols (7), phenols (3), terpene (1), esters (2), ketones (2), aldehyde (1), lactone (1) and hydrocarbons (2) were determined. The amounts of volatile compounds were found to be 21,544 µg kg−1. The application of aroma extract dilution analysis (AEDA) revealed the presence of 13 odor-active compounds alcohols (2), carboxylic acids (4), phenols (2), terpene (1), ketone (1), hydrocarbon (1) and unknown compounds (2) in Nigella sativa L. extract. Flavor dilution (FD) factors of key odorants ranged between 4 and 1024, while odor activity values (OAV) were in the range of 1.0 to 170.8. Acetoin was the only aroma-active ketone detected in Nigella sativa L. seed extracts. It had the strongest aroma (FD = 1024) and provided a buttery odor. This compound represented the most abundant compound of overall aroma profile with a concentration of 9394 µg kg−1, followed by isobutanoic acid (FD = 512 with a concentration of 218 µg kg−1) and contributed a powerful aroma and a cheesy characteristic odor.

Identification of volatile compounds from polyolefin used for food packaging

Identification of volatile compounds from different virgin polyolefin FCMs was carried out by GC-MS with both HS-SPME and ultrasonic extraction (UE), with the aim to obtein the most amount of volatile compounds from polyolefin. Seventy compounds were identified with 90% reliability by GC-MS with NIST 14 library, most of them are NIAS.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;

Comparison of volatile compounds at various developmental stages of tuberose (Polianthes tuberosa L. cv. Mahallati) flower with different extraction methods

Tuberose volatile components were evaluated at four developmental stages of flowers extracted by Hydrodistillation Extraction (HE), Solvent-Assisted Hydrodistillation Extraction (SAHE), Accelerated Organic Solvent Extraction (AOSE) and Organic Solvent Extraction (OSE). Among the total number of 37 compounds, benzenoids such as benzyl benzoate via AOSE and OSE seemed to have the highest values at Fully Opened stage (FO). In addition, FO showed the highest total amount of sesquiterpenoids extracted by all tested methods. Half-opened stage (HO) had the highest values of monoterpenoids such as 1,8-cineole in all methods of extraction, and benzenoids such as methyl benzoate from SAHE. Unopened bud (UO) and Nearly Slight Opened bud (NSO) stages showed the least amount of volatile compounds. Although OSE is treated as a traditional preparative extractive technique for tuberose oil, SAHE and AOSE could be useful for rapid extraction of preferable compound and the qualitative analysis of volatile components at analytical level.

Characterization of flavour and volatile compounds of fermented squid using electronic nose and HPMS in combination with GC-MS

ABSTRACTThe present study investigated the flavour characteristics and key volatile components of fermented squid (Dosidicus gigas) as well as their formation mechanism by three different starter cultures of lactic acid bacteria (LAB) and natural squid. The sensory assessment, volatile compounds, as well as the amino acids of the mixed fermented squid were detected using pickled brine as samples of fermented squid. A total 88 types of volatile compounds were found in four samples by 0–72 h of fermentation. After fermentation by LAB, the volatile compounds of squid showed that the fermented squid with different started cultures differed mainly in terms of numbers of alcohols, ketones, and esters. Furthermore, the amounts of volatile compounds among three starter cultures were also obviously different. Gas Chromatography-Mass Spectrometer (GC-MS) analysis indicated that the mixed fermentation process contained relatively higher (+)-limonene (11.71%) (lemon scent) and 3-hydroxy-2-butanone (5.72%) (creamy taste). These compounds were not detected in the control group. The main flavour compounds of nonanal and 2, 4-decadienal were gradually reduced. Meanwhile, 2, 3-butanedione, 2-heptanone, 2-pentylfuran, and nonanoic acid are the key flavour components. The total principal component is 94.01%, which were clarified by electronic nose in combination with principal components analysis. After mixed fermentation by LAB, the total amino acid (TAA) content reached 85.36 g/100 g, which was almost twice the amount of the control, especially in aspartate, glutamate, and threonine. Our results indicated that LAB has obvious effects on deodorization and flavour promotion during the fermentation of squid. This study provided an important basis for the further development and utilization of squid.

Effect of different combined moistening and redrying treatments on the physicochemical and sensory capabilities of smoking food tobacco material

ABSTRACTSmoking food tobacco material include flue-cured tobacco leaves, expanded stems, and reconstituted tobacco sheets. As the main raw material in the cigarette industry, the quality of flue-cured tobacco leaves is very important to the smoking food products. The effects of different combined moistening and redrying treatments on the physicochemical and sensory changes of flue-cured tobacco leaves have been systemically studied. This work has demonstrated that the steam moistening and low-temperature slow redrying (SM–LTSR) processes can improve the moisture content and color uniformity of tobacco leaves (p < 0.05). More importantly, the degradation of colorant and polyphenol precursors in tobacco leaves can be reduced for different redried lamina, and the average degradation amounts can be decreased by 30.63 and 22.41%, respectively. The total amount of volatile compounds can be decreased by 9.61% in comparison with the steam-water mixing moistening and high-temperature redrying (SWM–HTR) processes. We conclude that the mid-high-grade tobacco leaves should be processed through the SM–LTSR treatments to improve the color brightness, quality stability and retain flavor, while the low-grade tobacco leaves should be processed through the SWM–HTR processes to improve the processability, aftertaste and remove the offensive odor in actual threshing and redrying. This work has formed the suitable processing methods for different qualities of tobacco leaves and has laid the theoretical foundation for the quality improvement and flavor preservation of tobacco leaves.

Thermal study of ZrO2 nanoparticles: Effect of heating and cooling cycles on solid-solid transition

This study investigates the influence of particle size on the solid-solid transition in zirconium (ZrO2) nanoparticles. The Simultaneous Thermogravimetry/Derivate Thermogravimetric-Differential Thermal Analysis (TG/DTG-DTA) was used to evince the phase transitions processes as well as the quantity of volatile compounds and the residual organic matter formed during the synthesis of nanoparticles. Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) were used to prove the increase and agglomeration ;1;of particle size after each thermal cycle.

Effect of mixed yeast starter on volatile flavor compounds in Chinese rice wine during different brewing stages

The volatile compounds of Chinese rice wine fermented by Saccharomyces cerevisiae FC 15 and S. cerevisiae BR 30 and their combination (MIX) were investigated. The results showed that the wines fermented with different starters differed mainly in the numbers of alcohols and esters. Furthermore, the amounts of volatile compounds among three starters were also obviously different. After clarification, the loss of esters was greater than that of alcohols and aldehydes, whereas after sterilization, the loss of aldehydes was the greatest. PCA showed diethyl succinate to be the key flavor component. Moreover, short-chain fatty acid ethyl esters were main flavor substances during fermentation, whereas long-chain fatty acid ethyl esters were typical compounds after clarification and sterilization. Analysis of the ratio of higher alcohols to esters showed that BR 30 wine presented a stronger ester aroma than MIX wine, whereas FC 15 wine exhibited an outstanding alcohol flavor. Sensory evaluation indicated that FC 15 wine was intense in alcohol-aroma, whereas BR 30 wine exhibited high levels of cereal-aroma. Furthermore, both MIX and BR 30 wine were highly assessed in continuation and full body mouth-feel. It means that flavor characteristic of Chinese rice wine could be adjust by combination of yeast starters.