Higher alcohols concentration and its relation with the biological aging evolution

The production of 1-propanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol by two flor yeast strains during accelerated biological aging of sherry wines with different aging time has been evaluated. The S. cerevisiae G1 strain has shown a higher production of higher alcohols than the S. bayanus F12 strain highlighting the 1-propanol production in the youngest wine. Differences between the two studied yeasts decreased in relation with the aging time of the initial wine used. The multiple regression analysis carried out to relate the higher alcohols concentration and the values obtained from an aging equation showed R-squared values ranging from 81.1 to 96.5%. The higher alcohols that best described such relation were 1-propanol, isobutanol and 3-methyl-1-butanol.     

Rapid and non-invasive analysis of deoxynivalenol in durum and common wheat by Fourier-Transform Near Infrared (FT-NIR) spectroscopy

Fourier transform near-infrared spectroscopy (FT-NIR) was used for rapid and non-invasive analysis of deoxynivalenol (DON) in durum and common wheat. The relevance of using ground wheat samples with a homogeneous particle size distribution to minimize measurement variations and avoid DON segregation among particles of different sizes was established. Calibration models for durum wheat, common wheat and durum + common wheat samples, with particle size <500 µm, were obtained by using partial least squares (PLS) regression with an external validation technique. Values of root mean square error of prediction (RMSEP, 306–379 µg kg^–1) were comparable and not too far from values of root mean square error of cross-validation (RMSECV, 470–555 µg kg^–1). Coefficients of determination (r ²) indicated an “approximate to good” level of prediction of the DON content by FT-NIR spectroscopy in the PLS calibration models (r ² = 0.71–0.83), and a “good” discrimination between low and high DON contents in the PLS validation models (r ² = 0.58–0.63). A “limited to good” practical utility of the models was ascertained by range error ratio (RER) values higher than 6. A qualitative model, based on 197 calibration samples, was developed to discriminate between blank and naturally contaminated wheat samples by setting a cut-off at 300 µg kg^–1 DON to separate the two classes. The model correctly classified 69% of the 65 validation samples with most misclassified samples (16 of 20) showing DON contamination levels quite close to the cut-off level. These findings suggest that FT-NIR analysis is suitable for the determination of DON in unprocessed wheat at levels far below the maximum permitted limits set by the European Commission.     

Rapid and Simultaneous Analysis of Xanthines and Polyphenols as Bitter Taste Markers in Bakery Products by FT-NIR Spectroscopy

The food industry has a direct interest into bitter-tasting substances either for the identification of negative off-flavors or for the monitoring of a desired organoleptic quality. A rapid technique, based on Fourier transform-near infrared (FT-NIR) spectroscopy and able to detect taste molecular markers in bakery commodities, was developed, focusing the attention on biscuits category. Xanthines (caffeine, theobromine, and theophylline) and polyphenols (catechins and epicathechins), considered as mainly responsible for the bitter-taste of coffee\cocoa\chocolate based products, were firstly checked using a confirmatory liquid chromatography (LC)-ESI\mass spectrometry (MS)-MS procedure after hot methanol–water extraction. Correspondent data were used for the calibration of the FT-NIR through PLS regression. Values of the standard errors of prediction (lower than 10 %) were comparable to the values of the standard errors of cross-validation. Coefficients of determination indicated a good predictive power in the calibration model (R ² xanthines?=?0.97, R ² polyphenols?=?0.96) and a satisfying discriminating power among different contents in the validation models (R ² xanthines?=?0.96, R ² polyphenols?=?0.96). A testing phase on the generated model was executed by a comparison of LC-MS and sensory panel data with FT-NIR responses recorded on unknown biscuits: differences between found and predicted levels were generally below 5 % and the best predictability was achievable in chocolate-based biscuits. This methodology is able to work directly on solid products, has the potential to be expanded on other categories of gustative molecular markers (like sugars) and can be conceived as applicable for a routine control of a standardized bitter taste quality in a real industrial production.     

Major congeners of australian and imported brandies and other spirits as indicators of authenticity

The quantitative determination of the congeners methanol, n-propanol, ethyl acetate, i-butanol (2-methyl-1-propanol) and amyl alcohols (2-methyl-1-butanol and 3-methyl-1-butanol, which were not separated), was carried out on 61 Australian brandies, 61 French brandies and 50 wine distillates by gas chromatography. A comparison of the absolute amounts of congeners and their ratios (in the case of the C₃–C₅ alcohols) is presented in the light of several criteria of authenticity proposed by previous workers. Of these criteria, it was found that the amyl/i-butyl alcohol ratio and the i-butyl/n-propyl alcohol ratio were the most useful—on this basis, 11 French brandies (but no Australian brandy) were considered to be of suspect authenticity.     

Development of a rapid, non-destructive method for egg content determination in dry pasta using FT-NIR technique

A quick, non-destructive method, based on Fourier transform near-infrared (FT-NIR) spectroscopy for egg content determination of dry pasta is presented. Multivariate calibration was carried out by using partial least squares (PLS) regression. A calibration set of 108 samples, a validation set of 22 samples and a prediction set of 11 samples of egg pasta were used. The diffuse reflection spectra of different types of pastas were measured by FT-NIR analyzer in the 800-2500 nm spectral range. The optimal results for egg content (root mean square error of prediction (RMSEP) = 0.7; R² = 90.7, Rank = 4) were obtained when the spectra were subjected to the first derivation combined with multiplicative scatter correction (MSC) and smoothing. Egg content was determined from FT-NIR results by introducing a mathematical correction step.     

Detection of Volatile Organic Compounds Arising from Chicken Breast Filets Under Modified Atmosphere Packaging Using TD-GC/MS

The study aimed to detect volatile organic compounds (VOCs) during spoilage of chicken breast filets under modified atmosphere packaging (MAP, (70% O₂; 30% CO₂)). Storage tests were conducted at 6 °C in a household refrigerator. Measurements were made using untreated chicken breast filets and using filets inoculated with either Pseudomonas fluorescens or Escherichia coli bacteria. The gas space above the sample was adsorbed once a day on Tenax® TA and analyzed using thermal desorption-gas chromatography-mass spectrometry (TD-GC/MS). During storage, 60 volatile organic compounds of hydrocarbons, alcohols, aldehydes, ketones, esters, ethers, and sulfur-containing compounds were detected. It was shown that the presence of most hydrocarbons and aldehydes declined during storage time, whereas most of the alcohols, ketones, sulfur-containing compounds, esters, and ethers increased. Some of these detected VOCs could act as indicators to describe the freshness loss of the product. The best spoilage markers for spoiled chicken breast filets under MAP were 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-hydroxy-2-butanone, ethyl acetate, 2-butanone, and sulfur-containing compounds.     

Major constituents of fusel oils distilled from Australian grape wines

Fusel oils from Australian grape wines (Vine sp. Vitis vinifera) have been found to consist substantially of ethanol, n-propanol, isobutanol (2-methyl-1-propanol), isoamyl alcohol (3-methyl-1-butanol) and active amyl alcohol (2-methyl-1-butanol). In addition there are present large numbers of aliphatic esters, believed to be of considerable importance to grape brandy and spirit flavour and quality. The quantities and occurrence of these esters have been found to follow a systematic pattern. The major esterified alcohols are related to the free alcohols present and the major esterified acids occur as a series of acids of even carbon number with a maximum concentration at the n-decanoic acid. These relationships provide a basis for calculating the approximate ester composition of fusel oil.     

FT-NIR diffuse reflectance spectroscopy for kiwifruit firmness detection

This research was to study the potential of Fourier transform near-infrared (FT-NIR) diffuse reflectance spectroscopy as a nondestructive way for firmness measurement of “Qinmei” kiwifruit. NIR spectra were acquired from 800 nm to 2500 nm with different combinations of resolution (2, 4, 8, 16, and 32 cm^?1) and scan number (32, 64 and 128). Original spectra, along with first and second derivative treatments, were analyzed with and without preprocessing. Two preprocessing methods were investigated, including multiplicative scattering correction (MSC) and standard normal variate (SNV). Partial least square (PLS) model for original spectra of 2 cm^?1 resolution and 64 scan number without preprocessing indicated good results for calibration: correlation coefficient (r) of 0.89, root mean square error of calibration (RMSEC) of 4.09 N. The results showed that NIR diffuse reflectance spectroscopy was feasible to predict the firmness of “Qinmei” kiwifruit.     

Quantitative determination of fusel alcohols in beer and fermenting wort

A simple quantitative method for determining four aliphatic fusel alcohols in beer and fermenting wort, namely n-propanol, isobutanol, 2-methyl-1-butanol and 3-methyl-1-butanol, has been developed. Samples were distilled at reduced pressure (10 Torr) and analysed by gas liquid-solid chromatography. Graphitised carbon black deactivated with 0.3% SP-1000 Carbowax 20 M modified with derivative of terephthalic acid and 0.3% phosphoric acid was used as column packing. Coefficients of variation determined were 3% or less. To serve as examples, contents of fusel alcohols in some commercial and experimental beers and a wort fermented for various lengths of time are reported.     

Monitoring of chemical parameters of oxygen-treated musts during alcoholic fermentation and subsequent bottle storage of the resulting wines

The effect of hyper-oxygenation of Airén white wines on color characteristics, phenolic composition, and volatile profile has been evaluated in different processing steps, not previously reported in conjunction: musts, musts during the alcoholic fermentation, resulting young wines and after 1 year of bottle storage. Hyper-oxygenation treatment achieved a positive effect on color stabilization by means of significantly lower contents of most important phenolic compound families (hydroxycinnamic acid derivatives, benzoic acids, flavonols, and flavan-3-ols) in oxygen-treated musts in fermentation, young wines, and one-year-stored white wines. Therefore, browning was avoided in wines elaborated from hyper-oxygenated musts and their values of a* (green–red component of color) were maintained, in contrast to what occurred in control wines. With regard to volatile profile, the concentration of the majority of individual volatile compounds was significantly higher in wines derived from hyper-oxygenated musts, even after 1 year of bottle storage, especially those derived from alcoholic fermentation (alcohols: 2-methyl-1-butanol and 3-methyl-1-butanol, polar esters: ethyl lactate and ethyl glutarate, C₆ alcohols: 3-methyl-1-pentanol, and acetates: 2-phenylethyl acetate). This study enhances knowledge regarding the effects of hyper-oxygenation process during and after alcoholic fermentation and 1 year of bottle aging, especially as there is scarce literature available on the subject.     

Comparative study of the biochemical changes and volatile compound formations during the production of novel whey-based kefir beverages and traditional milk kefir

Cheese whey (CW) and deproteinised cheese whey (DCW) were investigated for their suitability as novel substrates for the production of kefir-like beverages. Lactose consumption, ethanol production, as well as organic acids and volatile compounds formation, were determined during CW and DCW fermentation by kefir grains and compared with values obtained during the production of traditional milk kefir. The results showed that kefir grains were able to utilise lactose from CW and DCW and produce similar amounts of ethanol (7.8–8.3 g/l), lactic acid (5.0 g/l) and acetic acid (0.7 g/l) to those obtained during milk fermentation. In addition, the concentration of higher alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol, and 1-propanol), ester (ethyl acetate) and aldehyde (acetaldehyde) in cheese whey-based kefir and milk kefir beverages were also produced in similar amounts. Cheese whey and deproteinised cheese whey may therefore serve as substrates for the production of kefir-like beverages similar to milk kefir.     

Gas-chromatographic determination of volatile constituents in Yugoslav plum brandies

Gas-chromatographic analysis, extraction and titration methods were used to determine the volatile components of 17 home-made natural plum brandy samples as well as 14 samples of industrially-produced plum brandy. The plum used for the production of Yugoslav plum brandies is Prunus domestica L. Eighteen alcohols, 23 esters and 21 organic acids were determined qualitatively and quantitatively. Eight aldehydes and nine ketones were only qualitatively determined. Apart from other components, the plum brandies analysed contained approximately 0.30 to 4.39 g of methanol/1; 0.40 g of 1-propanol/1; 0.19 g of 2-methyl-1-propanol/1; 0.05 g of 1-butanol/1; 0.10 g of 2-methyl-1-butanol/1; and 0.28 g of 3-methyl-1-butanol/1. The plum brandies also contained approximately 0.50 g of ethyl acetate/1 and about 0.03 g of acetaldehyde/1. The concentration of the free carboxylic acids present was about 1.50 g/1. Acetic acid constituted about 90% v/v of the total acid concentration.     

白酒基酒中典型醇的近红外预测模型构建

采用气相色谱法测定白酒基酒中的正丙醇、正丁醇、正戊醇和异戊醇的含量作为建立近红外预测模型的化学值,将近红外光谱图结合偏最小二乘法和内部交互验证法建立基酒中典型醇的快速检测模型,并进一步优化模型。确定了最优光谱预处理方法和最佳谱区,正丙醇、正丁醇、正戊醇和异戊醇的校正集样品的真实值与近红外预测值的决定系数（R2）分别为0.952、0.981、0.963和0.981,内部交互验证均方根误差分别为0.27、0.49、0.101?mg/100?mL和0.67?mg/100?mL;验证集的决定系数（R2）分别为0.947、0.980、0.928和0.952,预测均方根误差分别为0.40、0.81、0.49?mg/100?mL和1.35?mg/100?mL。结果表明建立的典型醇近红外快速检测模型的准确度、稳定性及预测性能均呈现良好,为白酒基酒的醇类物质品质分析方法研究提供了新的思路。     

Determination of Free Amino Acids in Coated Foods by GC–MS: Optimization of the Extraction Procedure by Using Statistical Design

The development and validation of an extraction procedure for quantification of free amino acids in coated products by MTBSTFA derivatization and GC–MS detection is described. The extraction method entailed the sample homogenization with hydrochloric acid (HCl) by stirring at 40 °C followed by two centrifugation steps. The optimum combination of the extraction variables was achieved by response surface methodology. HCl concentration and volume and stirring time influenced free amino acid extraction yield. The selected optimal extraction conditions were 5 g of sample mixed to 7.5 ml of 0.1 N HCl and stirred during 90 min. Consistency between predicted and experimental values as well as in the quality parameters was observed. The calibration curves were linear within the range 5–100 μg ml^?1 with correlation coefficient values (R ² ) higher than 0.99. Detection and quantification limits of the analytical procedure ranged from 2.10^?5 to 18.10^?2 μg μl^?1 and from 8.10^?5 to 60.10^?2 μg μl^?1, respectively. Precision was 0.20–12.59 % for run-to-run and 3.38–17.60 % for day-to-day. The accuracy is between 82.99 and 115.77 %. Nineteen amino acids were analyzed in frozen-thawed and deep-fried coated products from different origin, with cysteine being the most relevant.     

气相色谱-质谱法分析比较牛栏山牌清香型二锅头酒和浓香型白酒中的香味成分

采用液液萃取的方法分别提取清香型牛栏山二锅头酒和浓香型牛栏山白酒中的香味成分,结合气相色谱-质谱联用仪进行分析检测。结果表明两种香型白酒共检测出65种香味成分,其中：清香型牛栏山二锅头酒中共检测出34种香味成分,主要呈香化合物有酯类化合物、烷烃类化合物和醇类化合物,主要香味成分有3-甲基-1-丁醇、2-羟基-丙酸乙酯、棕榈酸乙酯、油酸乙酯和亚油酸乙酯;浓香型牛栏山白酒共检测出43种香味成分,其主要呈香化合物有酯类化合物、醇类化合物和酸类化合物,主要香味成分有己酸乙酯、1,1-二乙氧基乙烷、3-甲基-1-丁醇、己酸和2-羟基丙酸乙酯。表明酿酒原料和工艺不同导致的香味成分的差异,是赋予两种白酒不同口感和风格的关键。     

A rapid spectroscopic method for quantification of P57 in Hoodia gordonii raw material

The feasibility of quantifying the perceived active ingredient (P57) in Hoodia gordonii raw material using Fourier transform near- and mid-infrared spectroscopy combined with chemometric techniques was investigated. The concentration of P57 (a triterpene glycoside) was determined in 146 plant samples with liquid chromatography coupled to mass spectrometry and these values were used to develop a calibration model based on the partial least squares projections to latent structures (PLS) and orthogonal projections to latent structures (O-PLS) regression algorithms. The performance of each calibration model was evaluated according to the root mean square error of prediction (RMSEP) and correlation coefficient (R²). The PLS model with 2nd derivative pre-processing predicted P57 content based on the FT-NIR spectra with the best accuracy and a correlation coefficient (R²) value of 0.9629 and the lowest RMSEP of 0.03%. These results demonstrated that FT-NIR spectroscopy can be used to rapidly quantify P57 in H. gordonii raw material with high accuracy.     

Statistical Analysis for Quality Adjustment of the Analytical Curve for Determination of Pesticide Multiresidue in Pineapple Samples

This work describes the development of an analytical methodology based on the modified QuEChERS method and GC/MS detection involving the analysis of 38 pesticides in pineapple from a local market in Fortaleza-Brazil. Matrix-standard calibration and heteroscedasticity have been studied by a weighted least squares linear regression model application. The analytical curves for most of the analytes (except cyproconazole and pyraclostrobin) presented heteroscedasticity by weighted least square regression (WLS). The weighted correlation coefficient values were in the range of 0.9690 to 0.9987 (linear range of 0.03 to 0.50 mg kg^?1). The calibration curves obtained by applying regression by ordinary least squares (OLS) showed relative errors of approximately 32.3% for fenpropathrin, 23.1% for buprofezin, 17.4% for methyl parathion, and 13.9% for ametryn. Analysis of commercial pineapple samples revealed the presence of methyl parathion, buprofezin, ametryn, and fenpropathrin at 0.023 ± 0.0037, 0.013 ± 0.0047, 0.043 ± 0.0156, and 0.031 ± 0.0049 mg kg^?1, respectively.     

Novel and Precise Method to Isolate,Identify, and Quantify Volatile Compounds in Headspace of Pear Juice Enriched with α-Cyclodextrin

The combination headspace solid phase micro-extraction?+?gas chromatography–mass spectrometry?+?gas chromatography with flame ionization detector was successfully used in quantitative determination of the instrumental odor of pear juice. Esters, aldehydes, alcohols, and terpenes were the major chemical families of the pear juice odor. Twenty-six were identified and quantified, with propyl acetate, hexyl acetate, 2-methyl-1-butanol, and butyl acetate being the major compounds. α-Cyclodextrins (CD) significantly improved the color of pear juice, leading to higher values of L* and lower of scores of a*, b*, and ΔE*. However, α-CD also reduced the total concentration of volatiles in the headspace of the juice by creating inclusion complexes with volatiles; after 40 min of oxidation, total volatiles were 8.2 and 3.4 mg L^?1 in control and α-CD-treated juices, respectively. But in summary, the global quality (joint consideration of the main sensory attributes) was improved by the addition of α-CD (6.9 compared to 5.2).     

静态顶空气质联用法测定霞多丽在酒精发酵过程中香气的变化

运用静态顶空-气相色谱质谱联用法,从霞多丽葡萄汁到酒精发酵结束,每隔12h对其香气成分进行检测。检测得到的香气成分通过质谱谱库进行定性,色谱峰面积归一化法进行定量。测定结果显示:霞多丽在酒精发酵过程中共检测出31中香气物质,其中醇类物质有11种,酯类物质有13种,其他物质(酸、醛、酮)有7种。发酵前后香气成分的种类和相对含量变化显著。其中酯类和醇类物质的种类和相对含量随着发酵的进行有所增加,而其他类(酸、醛、酮)物质的种类和相对含量随着发酵的进行急剧下降。发酵结束后,发酵液的主要香气成分为:乙醇、2-甲基丙醇、3-甲基丁醇、2,3-丁二醇、苯乙醇、正丙醇、己醇、乙酸己酯、辛酸乙酯、壬酸乙酯、2-苯基乙酸乙酯、十二酸乙酯、乙酸乙酯、2-甲基乙酸丙酯、3-甲基乙酸丁酯、己酸乙酯、乙酸。     

液液萃取与固相微萃取二锅头香气成分的比较

采用液液萃取和固相微萃取结合气相色谱-质谱联用技术对清香型牛栏山二锅头的香气成分进行了定性分析,共得到42种香气成分,主要包括酯类化合物17种,酸类化合物8种,醇类化合物7种,杂环类化合物5种、烷烃类化合物4种和醛类化合物1种。液液萃取主要呈香物质有3-甲基-1-丁醇、十六酸乙酯、2-羟基-丙酸乙酯、油酸乙酯和亚油酸乙酯。固相微萃取主要呈香物质有3-甲基-1-丁醇、己酸乙酯、3-甲基-1-丁醇乙酸、辛酸乙酯和乙酸乙酯。液液萃取和固相微萃取对香气成分的分离效果存在较大差异,表明两种方法对白酒的定性分析有一定的互补性。