A robust optimization approach to wine grape harvesting scheduling

Optimization models are increasingly being used in agricultural planning. However, the inherent uncertainties present in agriculture make it difficult. In recent years, robust optimization has emerged as a methodology that allows dealing with uncertainty in optimization models, even when probabilistic knowledge of the phenomenon is incomplete. In this paper, we consider a wine grape harvesting scheduling optimization problem subject to several uncertainties, such as the actual productivity that can be achieved when harvesting. We study how effective robust optimization is solving this problem in practice. We develop alternative robust models and show results for some test problems obtained from actual wine industry problems.     

Reactivity of wine polyphenols under oxidation conditions: Hemisynthesis of adducts between grape catechins or oak ellagitannins and odoriferous thiols

The reasons for the loss of characteristic odoriferous thiols during the aging of wine in oak-made barrels and subsequent storage in bottles have been in part attributed to covalent capture of these thiols by polyphenolic wine components that are dehydrogenated into electrophilic ortho-quinones upon wine oxygenation. Herein, FeCl₃ was used as oxidant in oxygen-deprived aqueous solutions to dehydrogenate grape (epi)catechins and oak ellagitannins in the presence of two typical odoriferous thiols, 2-furanmethanethiol (2FMT) and 3-sulfanylhexan-1-ol (3SH). The preparative-scale conditions used enabled the isolation of six novel 2FMT-bearing (epi)catechin derivatives, three known 3SH-bearing catechin derivatives (the structures of two of those were revised to be strictly derived from 1,6-conjugate addition), three novel 2FMT-bearing castalagin derivatives, and one novel 3SH-bearing castalagin derivative. The structures of these castalagin-based thio-adducts revealed that the capture of thiols by the different dehydrogenated pyrogallol rings of castalagin starts at ring IV, then ring III, and finally ring V.     

Determination of sulfur forms in wine including free and total sulfur dioxide based on molecular absorption of carbon monosulfide in the air–acetylene flame

A new method for the determination of sulfur forms in wine, i.e., free SO₂, total SO₂, bound SO₂, total S, and sulfate, is presented. The method is based on the measurement of the carbon monosulfide (CS) molecular absorption produced in a conventional air–acetylene flame using high-resolution continuum source absorption spectrometry. Individual sulfur forms can be distinguished because of the different sensitivities of the corresponding CS molecular absorption. The sensitivity of free SO₂ is about three times higher than the value for bound SO₂ and sulfate. The method makes use of procedures similar to those used in classic reference methods. Its performance is verified by analyzing six wine samples. Relative standard deviations are between 5 and 13% for free SO₂ and between 1 and 3% for total SO₂. For the validation of the accuracy of the new method, the results are compared with those of reference methods. The agreement of the values for total SO₂ with values of the classic method is satisfactory: five out of six samples show deviations less than 16%. Due to the instability of free SO₂ in wine and the known problems of the used reference method, serious deviations of the free SO₂ results are found for three samples. The evaluation of the limits of detection focuses on the value for free SO₂, which is the sulfur form having by far the lowest concentration in wine. Here, the achievable limit of detection is 1.8 mg L⁻¹. Figure Detection of non-metal elements using continuum source flame absorption spectrometry     

Comparison of the effectiveness of solid-phase and ultrasound-mediated liquid-liquid extractions to determine the volatile compounds of wine

Two ultrasound-assisted liquid–liquid extraction (LLE-I, LLE-II) methods were compared to a solid-phase extraction (SPE) protocol to assess their effectiveness for the analysis of up to 44 volatile compounds in a synthetic and several commercial white, red and “cream” wines produced in the southwest of Spain. Regardless of the extraction protocol used the highest recoveries corresponded to acids and terpene alcohols and the lowest to lactones and alcohols. In any case, it was concluded that one of the liquid–liquid extraction protocols evaluated led to higher recoveries for a greater number of odorants that could be implicated in the aroma of the wines than the solid-phase extraction. However, the SPE method also presented some advantages that should not be overlooked, like higher repeatability and throughput and lower solvent consumption.     

Analysis of selected carbonyl oxidation products in wine by liquid chromatography with diode array detection

A high performance liquid chromatography (HPLC) method for the detection and quantitation of acetaldehyde, glyceraldehyde, pyruvic acid, 2-ketoglutaric acid, and formaldehyde in wine, based on the formation of the 2,4-dinitrophenylhydrazones, is presented. These carbonyl compounds often result from the chemical oxidation of major wine components, and are known to affect flavor and color stability. Their analysis in wine is complicated due to their instability and their tendency to react reversibly with bisulfite to form α-hydroxysulfonates. Published methods that break down the sulfonates for the quantitation of total carbonyls in wine involve alkaline hydrolysis of sulfite-bound carbonyls, but we show, for the first time, that this alkaline treatment step significantly increases the concentration of carbonyls during analysis. A solution based on oxygen exclusion is described. The technique offers good specificity, reproducibility (%RSD 0.45-10.6), and limits of detection (1.29-7.53 μg L⁻¹). The method was successfully used to monitor concentration changes of these compounds in both white and red wines.     

Determination of 4-ethylcatechol in wine by high-performance liquid chromatography-coulometric electrochemical array detection

A HPLC method using a coulometric electrode array detector (CEAD) to analyse 4-ethylcatechol in wine was established. The procedure does not require any sample preparation or analyte derivatisation and performs chromatographic separation in a short time. The assay method is linear up to 1520 μg L⁻¹ and precise (R.S.D. < 3%), with limits of detection and quantitation of 1.34 μg L⁻¹ and 2.2 μg L⁻¹, respectively. Recoveries in spiked wine samples ranged from 95% to 104% with a median value of 102% and matrix effects were not observed. The method was applied to the evaluation of the concentration of 4-EC in 250 commercial Italian wines. The red wines analysed had median, 75° percentile and maximum values of 37 μg L⁻¹, 89 μg L⁻¹ and 1610 μg L⁻¹, respectively. For Sangiovese-based wines the mean ratios of 4-EP and 4-EG to 4-EC were 3.7:1 and 0.7:1, respectively. The feasibility of a cheaper fluorimetric approach to 4-EC quantification was investigated.     

Simple and rapid determination of biogenic amines in wine by liquid chromatography-electrospray ionization ion trap mass spectrometry

A rapid liquid chromatographic-electrospray ionisation ion trap mass spectrometry (LC-ESI-ITMS) method has been developed for the routine analysis of eight of the most oenologically important biogenic amines in wine without any sample pre-treatment. The method involves addition of heptylamine as an internal standard (IS) and the direct injection of filtered wine samples previously diluted with ultra high purity (UHP) water. The full-scan MS-MS spectra and the identical retention times to those of reference standards were used for unequivocal identification of the analytes. For most amines, the most abundant ions were derived from the loss of an ammonia group, while in the case of spermine and the I.S. the major product ions arose from the loss of 1,3-propyldiamine and the production of adduct with water, respectively. Detection was achieved in positive ionisation with an ion trap mass spectrometer operating in multiple-reaction monitoring (MRM) mode. The method allowed accurate determination of the analytes in the range 0.5-40 ng mL⁻¹. Within-day and between-day relative standard deviation percentages were <8% and <12%, respectively. The overall process was successfully applied to identify and quantify biogenic amines in Rioja red wines. The new method is sensitive, rapid, cheap and less labour intensive.     

Effect of temperature variation on the visible and near infrared spectra of wine and the consequences on the partial least square calibrations developed to measure chemical composition

Many studies have reported the use of near infrared (NIR) spectroscopy to characterize wines or to predict wine chemical composition. However, little is known about the effect of variation in temperature on the NIR spectrum of wine and the subsequent effect on the performance of calibrations used to measure chemical composition. Several parameters influence the spectra of organic molecules in the NIR region, with temperature being one of the most important factors affecting the vibration intensity and frequency of molecular bonds. Wine is a complex mixture of chemical components (e.g. water, sugars, organic acids, and ethanol), and a simple ethanol and water model solution cannot be used to study the possible effects of temperature variations in the NIR spectrum of wine. Ten red and 10 white wines were scanned in triplicate at six different temperatures (25 °C, 30 °C, 35 °C, 40 °C, 45 °C and 50 °C) in the visible (vis) and NIR regions (400-2500 nm) in a monochromator instrument in transmission mode (1 mm path length). Principal component analysis (PCA) and partial least squares (PLS) regression models were developed using full cross validation (leave-one-out). These models were used to interpret the spectra and to develop calibrations for alcohol, sugars (glucose + fructose) and pH at different temperatures. The results showed that differences in the spectra around 970 nm and 1400 nm, related to OH bonding were observed for both varieties. Additionally an effect of temperature on the vis region of red wine spectra was observed. The standard error of cross validation (SECV) achieved for the PLS calibration models tended to inverse as the temperature increased. The practical implication of this study it is recommended that the temperature of scanning for wine analysis using a 1 mm path length cuvette should be between 30 °C and 35 °C.     

Gas chromatography-mass spectrometry determination of 3-mercaptohexan-1-ol and 3-mercaptohexyl acetate in wine: a comparison of headspace solid phase microextraction and solid phase extraction methods

A gas chromatography-mass spectrometry method was established using headspace solid phase microextraction (HS-SPME) as the sampling procedure to analyse 3-mercaptohexan-1-ol (3-MH) and 3-mercaptohexyl acetate (3-MHA), two molecules with a tropical fruit aroma, in wine at trace level. This method offers important advantages, as it neither requires time-consuming sample preparation nor uses dangerous organic compounds, thus making control of wine aroma easier and suitable for routine analysis. As a comparison, a solid phase extraction (SPE) method, already described elsewhere for aroma analysis, was applied to quantify these analytes, extending this exhaustive enrichment to two important thiols. Detection limits for both the approaches were close to the sensory threshold value, resulting lower for the HS-SPME procedure and suitable for requirements in the oenological field. The application of the two proposed methods to 52 wines of different varieties gave similar results.     

冯了性风湿跌打药酒中东莨菪素含量的高效液相色谱法测定

介绍了用高效液相色谱法测定冯了性风湿跌打药酒中东莨菪素含量的方法。色谱柱为ＳｐｈｅｒｉｓｏｂＣ_（１８）柱（１５０ｍｍ×４．６ｍｍ,５μｍ）;流动相为甲醇－水（４６：５４,Ｖ／Ｖ）的混合液;流速０．８ｍＬ／ｍｉｎ;检测波长３６０ｎｍ,样品流过Ｓｅｐ－ｐａｋＣ_（１８）微柱,收集第６ｍＬ至第８ｍＬ的流出液作供试液。方法平均回收率为１０１．０％,ＲＳＤ＝０．９３％。进样量在０．２０６～２．０６μｇ范围内线性关系良好,ｒ＝０．９９９７．所建立的方法可作为冯了性风湿跌打药酒质量控制的一种简便、快速和准确的测定方法。