Primary Amino Nitrogen Research Articles

Foliar urea applications to apple trees increase yeast assimilable nitrogen, amino acids, and flavor volatiles in fruit and hard cider

Volatile compounds are a crucial component of hard apple (Malus ✕domestica Borkh.) cider aroma, flavor, and consequent marketability. Amino acids are used by Saccharomyces cerevisiae yeast in the production of volatiles and their precursors. This study hypothesized that foliar applications of nitrogen to apple trees would elevate the concentration of amino acids in the fruit, thus increasing the concentration of sensorially distinguishable aromatic volatiles in cider. In this experiment, urea foliar fertilizer was applied to ‘Ellis Bitter’ and ‘Harry Masters Jersey’ apple trees to create Control (0 applications), Low (3 weekly applications), and High (5 weekly applications) treatments. Total leaf nitrogen increased with the number of foliar urea applications, demonstrating plant uptake. The total fruit yield and fruit efficiency (total harvested fruit mass relative to trunk cross-sectional area) did not differ among treatments within the same cultivar. Similarly, fruit maturity, size, total phenolics, pH, and soluble solids concentration did not differ among treatments. Yeast assimilable nitrogen (YAN) and amino acids in the juice increased with the number of foliar urea applications, as did fermentation rates. Relative to the Control, the High treatment had 130% greater YAN in ‘Ellis Bitter’ and 145% in ‘Harry Masters Jersey’. Over 90% of the YAN in all juice samples was composed of primary amino nitrogen (PAN), and the majority of the PAN among all treatments was asparagine. Ester and fatty acid content in hard ciders increased with the number of urea applications; however, higher alcohols showed a mixed relationship with the number of applications in the cultivar ‘Ellis Bitter’. Aroma and flavor differences among treatments were discernible by triangle discrimination test panelists; however, the specific sensory differences were not easily identifiable with untrained panelists. This study demonstrated that late season foliar urea applications to apples trees can increase juice YAN and aromatic compounds in finished cider.

The Influence of Chitosan on the Chemical Composition of Wines Fermented with Lachancea thermotolerans.

Chitosan exerts a significant influence on various chemical parameters affecting the quality of wine produced using multiple strains of Lachancea thermotolerans. The impact of chitosan on these parameters varies depending on the specific strain studied. We observed that, under the influence of chitosan, the fermentation kinetics accelerated for all examined strains. The formation of lactic acid increased by 41% to 97% across the studied L. thermotolerans strains, depending on the specific strain. This effect also influenced acidity-related parameters such as total acidity, which increased by 28% to 60%, and pH, which experienced a decrease of over 0.5 units. The consumption of malic acid increased by 9% to 20% depending on the specific strain of L. thermotolerans. Nitrogen consumption also rose, as evidenced by all L. thermotolerans strains exhibiting a residual value of Primary Amino Nitrogen (PAN) of below the detection limit, and ammonia consumption increased by 90% to 100%, depending on the strain studied. However, certain parameters such as acetic acid, succinic acid, and glycerol showed contradictory results depending on the strain under investigation. In terms of volatile composition, chitosan supplementation led to increased production of i-butanol by 32% to 65%, 3-methylbutanol by 33% to 63%, and lactic acid ethyl ester by 58% to 91% across all studied strains of L. thermotolerans. Other analyzed aroma compounds exhibited varying changes depending on the specific strain of L. thermotolerans.

Rapid Dilute Sulfuric Acid Hydrolysis of Soy Flour to Amino Acids for Microbial Processes and Biorefining

Amino acids have relevance in biorefining as fermentation nutrients but also as valued coproducts obtainable from plant biomass. Soy flour was studied as a representative low-cost protein source requiring hydrolysis to free primary amino acids for utilization. Within the context of biorefining, process schemes, reactant concentrations, times, and temperatures were varied to explore the efficiency of dilute sulfuric acid hydrolysis of soy flour to release amino acids. Two process strategies were optimized. Either soy flour was co-processed with switchgrass biomass using a dilute-acid pretreatment, or it was hydrolyzed alone with dilute acid. Significant improvement to hydrolysate fermentability was accomplished by adding 2.5–10 g/L soy flour to switchgrass pretreatment with dilute sulfuric acid (0.936% v/v) for 15 min at 160 °C. This practice optimized accumulation of neutral sugars and resulted in a 25% reduction in furfural while boosting xylose 7% and up to doubling primary amino nitrogen (PAN), as compared to no soy flour addition to switchgrass pretreatment. When soy flour was hydrolyzed alone, PAN titers were optimized to 1588 mg N/L (9.9 g amino acids/L) and yield to 0.0529 g PAN/g flour (61% of theoretical) using a 10% (v/v) (1.8 M) sulfuric acid hydrolysis 30 min at 160 °C.

Fruitlet Thinning Improves Juice Quality in Seven High-tannin Cider Cultivars

Over 3 years (2016–18), tree productivity, biennial bearing, return bloom, and fruit quality were evaluated for seven high-tannin cider apple (Malus ×domestica Borkh.) cultivars. Five treatments were evaluated on each of the seven cultivars: hand-thinned of all fruit (a zero crop load treatment); hand-thinned to crop densities of three, six, or nine fruit/cm2 trunk cross-sectional area (TCSA); or left unthinned. In this paper, we report on the fruit maturity and juice quality properties that were analyzed for the three nonzero crop load treatments and the unthinned control. The effects of crop load on fruit maturity, as measured by starch pattern index and preharvest drop, were cultivar dependent. Crop density (fruit/cm2 TCSA) had a significant effect on all fruit maturity and juice quality variables, although effects were weakest in the “off” year (2017) for the whole planting when initial fruit set was low. As crop density increased, total poly phenols, titratable acidity, soluble solids, and primary amino nitrogen decreased in the juice of all seven cultivars. A partial budget analysis indicated that the reduced costs of nitrogen supplements due to increased primary amino nitrogen concentration alone would not justify cost of chemical or hand-thinning. By extrapolating the spring flowering density in the fourth year to potential fruit yields at harvest, we found that reducing crop load was projected to increase cumulative total polyphenol yields per tree over the long term. For the cultivars in this experiment, a target crop density of nine fruit/cm2 was found to adequately decrease biennial bearing while also not diminishing juice quality for hard cider production. High-tannin cider apple growers should consider juice quality, particularly tannin production, when making crop load management decisions.

The beneficial effect of leaf removal during fruit set on physiological, biochemical, and qualitative indices and volatile organic compound profile of the Cypriot reference cultivar 'Xynisteri'.

'Xynisteri' is the reference Cypriot white cultivar that, despite its significant societal and economic impact, is poorly characterized regarding its qualitative properties, while scarce information exists regarding its aroma profile. In the current study, the effect of leaf removal during fruit set (BBCH 71) on 6-year cordon-trained, spur-pruned grapevines was assessed and an array of physiological, biochemical, and qualitative indices were monitored during successive developmental stages (BBCH 75, BBCH 85, BBCH 87, and BBCH 89). Grapes were additionally monitored for the volatile organic compounds (VOCs) profile during the advanced on-vine developmental stages (BBCH 85-BBCH 89) with the employment of gas chromatography-mass spectrometry (GC-MS), Fourier-transform near infrared (FT-NIR) spectra and electronic nose (E-nose) techniques. Grape berries from the vines subjected to leaf removal were characterized by higher solid soluble sugars (SSC), titratable acidity (TA), tartaric acid, and ammonium nitrogen contents, while this was not the case for assimilable amino nitrogen (primary amino nitrogen). A total of 75 compounds were identified and quantified, including aliphatic alcohols, benzenic compounds, phenols, vanillins, monoterpenes, and C13 -norisoprenoids. Leaf removal led to enhanced amounts of glycosylated aroma compounds, mainly monoterpenes, and C13 -norisoprenoids. Chemometric analysis, used through FT-NIR and E-nose, showed that the aromatic patterns detected were well associated to the grape ripening trend and differences between leaf removal-treated and control grapes were detectable during fully ripe stage. Leaf removal at fruit set resulted in an overall induction of secondary metabolism, with special reference to glycosylated aroma compounds, namely monoterpenes and C13 -norisoprenoids. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Influence of Grapevine Leafroll-associated Virus-3 in Mature Plants of Vitis vinifera L. cv Albariño on 110R and 196.17C Rootstocks

The detrimental effects of grapevine leafroll disease (GLD) have been documented mainly in young plantsand little data is available on infected grapevines when they reach maturity. This study examined theinfluence of the rootstock on the effect of GLRaV-3 in a 20-year-old Vitis vinifera cv Albariño vineyard inwhich the virus has been spread by Planococcus ficus. Plants grafted on Richter 110 or Castell 196.17 withsimilar development were analysed for grapevine leafroll-associated viruses. In particular, 25 GLRaV-3-infected and 25 leafroll-free and asymptomatic vines were selected and monitored during a period of threeyears to determine grape yield and must components. Although the virus infection affected plants on bothrootstocks, it caused a greater effect on plants grafted onto 110R, with average accumulated yield losses ofup to 33%, relative to losses of 16% for plants on 196.17C. The sugar content was lower in the must frominfected plants on 110R (-2.1ºBrix) than in the must from plants on 196.17C (-1.5ºBrix). The presence ofthe virus was associated with decreased concentrations of primary amino nitrogen (PAN) and ammonium(NH4+), with the greatest effect for 110R (-35%). As 110R is the most used rootstock in Spain, particularcare must be taken to prevent the transmission of GLRaV-3 to certified virus-free plants on 110R in newvineyards. In sensitive varieties such as Albariño, particularly in areas with an active spread of the virusby mealybugs, grafting on 196.17C seems to minimise the effect that GLD has in a medium to long term.

Optimised processing of faba bean (Vicia fabaL.) kernels as a brewing adjunct

Pulse (Fabaceae) grains, such as peas and beans, are derived from crops that are usually cultivated in the absence of mineral nitrogen fertiliser as these crops can obtain their nitrogen requirement naturally from the air via biological nitrogen fixation. Therefore, pulses present a significantly lower greenhouse gas (GHG) footprint than crops demanding nitrogen fertiliser, whilst also offering significant quantities of starch for the brewing and distilling industries. Mitigation of agriculture derived GHG emissions through utilisation of pulses can have a positive environmental impact. To this end, the potential of exploiting dry, dehulled faba bean (Vicia faba L.) kernel flour as an adjunct for beer production was evaluated. The impact of different temperature regimes and commercial enzymes were assessed for their effect on wort: viscosity; run-off rate; primary amino nitrogen content and, fermentability. Faba beans demonstrated insufficient endogenous enzyme capacity for starch conversion and generated a viscous wort. However, using a stepped temperature mashing regime and exogenous enzyme additions, the faba bean wort was comparable in processability and fermentability to that of 100% malted barley wort. The faba based beer and co-product qualities demonstrate the environmental, nutritional and commercial potential of pulses in brewing. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling

Application of a topographic pedosequence in the Villány Hills for terroir characterization

Terroir refers to the geographical origin of wines. The landscape factors (topography, parent rock, soil, microbial life, climate, natural vegetation) are coupled with cultural factors (cultivation history and technology, cultivars and rootstock) and all together define a terroir. The physical factors can be well visualized by a slope profile developed into a pedosequence showing the regular configuration of the relevant physical factors for a wine district. In the present study the generalized topographic pedosequence (or catena) and GIS spatial model of the Villány Hills, a historical wine producing region, serves for the spatial representation and characterization of terroir types. A survey of properties of Cabernet Franc grape juice allowed the comparison of 10 vineyards in the Villány Wine District, Southwest Hungary. Five grape juice properties (FAN, NH3, YAN, density and glucose + fructose content) have been found to have a moderate linear relationship (0.5 < r2 < 0.7) with the Huglin Index (HI) and aspect. Aspect, when determined on the basis of angular distance from South (180°), showed a strong correlation (r2 > 0.7) with FAN, NH3, YAN, sugar and density and moderate correlation with primary amino nitrogen (PAN). HI showed a correlation with three nitrogen related parameters FAN, NH3, YAN, density and glucose + fructose content. Elevation and slope, however, did not correlate with any of the chemical properties.

1,6-Bis(hydrazidomethylsulfinyl)hexane: the solution state and complexation with copper(II)

The solution state of a new antituberculosis drug 1,6-bis(hydrazidomethylsulflnyl)hexane (L) and its complexation with copper(II) were investigated by spectrophotometry, pH-potentiometry (T = 25 °C; at variable ionic strength), and mathematical modeling. The dissociation constants of the protonated and imidol forms of compound L were determined. Complexation reactions in the Cu2+—L system result in mononuclear complexes [CuL]2+ and [CuL2]2+ with the amide form of the ligand provided that the redox reactions are excluded. The most probable (optimized) structures of 1,6-bis(hydrazidomethylsulfinyl)hexane and its complexes were obtained from quantum chemical calculations within the framework of the density functional theory (PBE/6-311G (d) method). Compound L adopts a folded conformation. The coordination site of the 1:1 complex includes six oxygen atoms from two carbonyl groups, two sulfoxide groups, and two water molecules. In the 1:2 complex, each ligand molecule is coordinated in bidentate mode through the carbonyl oxygen atom and the primary amino nitrogen of a hydrazide fragment.

Foliar Urea Applications Increase Yeast Assimilable Nitrogen Concentration and Alcoholic Fermentation Rate in ‘Red Spy’ Apples Used for Cider Production

Yeast assimilable nitrogen (YAN) can be a limiting nutritional factor for Saccharomyces cerevisiae yeast when fermenting apple (Malus ×domestica Borkh.) juice into hard cider. Endogenous YAN concentrations in apples are often below the recommended thresholds to completely use all of the fermentable sugar and minimize the production of off-flavors, such as hydrogen sulfide. Cider producers supplement apple juice with exogenous nitrogen to increase YAN. Urea, commonly applied to apple orchards to increase fruit size and yields, was tested for its ability to increase endogenous apple juice YAN. Starting 6 weeks before harvest in 2017 and 2018, a 1% urea solution was applied to ‘Red Spy’ apple trees one, three, or five times to create low-, medium-, and high-rate treatments, respectively. Relative to the control, the high treatment increased YAN by 229% in 2017 and by 408% in 2018. More than 90% of the YAN in all juice samples was composed of primary amino nitrogen (PAN). Among all treatments, PAN mostly comprised asparagine, and as urea applications increased, the relative concentration of asparagine also increased. Aspartic acid and then glutamic acid were the second and third most abundant amino acids in all treatments, respectively, but comprised less of the total PAN as the number of urea applications increased. Soluble solid concentration, pH, titratable acidity, and total polyphenol concentration were not different among treatments. There was a positive correlation between increased urea application rate and the maximum fermentation rate, which resulted in a shorter fermentation duration. Increasing the number of urea applications was also correlated with greater hydrogen sulfide (H2S) production in juice fermented from fruit harvested in 2017 but not for fruit harvested in 2018. No residual H2S was found in the finished cider from any treatment. Increasing the number of urea applications was estimated to be less expensive than supplementing the juice with Fermaid O™. There would have been no cost savings if Fermaid K™ was used as an exogenous nitrogen source. Foliar urea applications were estimated to be more expensive than supplementing juice with diammonium phosphate. This study demonstrated that foliar urea applications can effectively increase YAN concentration in cider apples while not negatively affecting other juice quality attributes.

Soil Nitrogen Fertilization Increases Yeast Assimilable Nitrogen Concentrations in ‘Golden Russet’ and ‘Medaille d’Or’ Apples Used for Cider Production

The recent growth in the U.S. hard-cider industry has increased the demand for cider apples (Malus ×domestica Borkh.), but little is known about how to manage orchard soil fertility best to optimize horticultural performance and juice characteristics for these cultivars. To assess whether nitrogen fertilizer applied to the soil can improve apple juice and cider quality, calcium nitrate (CaNO3) fertilizer was applied at different rates to the soil beneath ‘Golden Russet’ and ‘Medaille d’Or’ trees over the course of three growing seasons. The experiment started when the trees were in their second leaf. The trees were cropped in their third and fourth leaf. At the end of the first growing season of the experiment, the greatest fertilizer rate increased tree trunk cross-sectional area (TCSA) by 82% relative to the control, but this difference did not persist through to the end of the study. Yield and crop load were unaffected by the nitrogen fertilization treatments. Increasing the nitrogen fertilizer rate correlated positively with more advanced harvest maturity in ‘Golden Russet’ fruit, which resulted in greater soluble solid concentration (SSC). Fruit from the greatest fertilizer rate treatment had an average starch pattern index (SPI) that was 1 U greater than in the control, and an SSC that was 3% greater than the control. The fertilizer treatments did not affect juice pH, titratable acidity (TA), or total polyphenol concentrations. Yeast assimilable nitrogen (YAN) concentrations were increased by nitrogen fertilization for both cultivars in both harvest years. The greatest fertilizer treatment increased juice primary amino nitrogen by 103% relative to the control. Greater nitrogen fertilization rates correlated positively with less hydrogen sulfide production during the fermentation of ‘Golden Russet’ juice from the first, but not the second, harvest. During the first year, cumulative hydrogen sulfide production for the ‘Golden Russet’ control treatment was 29.6 μg·L–1 compared with the ‘Golden Russet’ high treatment, which cumulatively produced 0.1 μg·L–1. Greater maximum fermentation rates and shorter fermentation durations correlated positively with increased fertilization rate for both cultivars after the second harvest. High treatment fermentations had maximum fermentation rates 110% greater, and fermentation durations 30% shorter than the control. Other horticultural and juice-quality parameters were not affected negatively by the CaNO3 treatments. In orchards producing apples specifically for the hard-cider industry, nitrogen fertilizer could increase juice YAN, thus reducing the need for exogenous additions during cider production.

Quality characterisation via image forming methods differentiates grape juice produced from integrated, organic or biodynamic vineyards in the first year after conversion

In this study, the effects on grape juice quality resulting from the conversion of vineyard plots from integrated to organic and biodynamic management vs. integrated management were assessed using image forming methods. In addition, grape yield, Botrytis infection and the chemical composition of wood prunings and grapes were assessed. The images of replicate, encoded samples representing five different treatments were: (i) grouped into pairs displaying similar image features, (ii) characterised with respect to the quality domains ‘strength of form expression’ and ‘resistance to deterioration’ and (iii) ranked according to the quality characterisation. Based on the image analyses, all samples pairs were correctly grouped, i.e. the five production methods were precisely separated. The treatments were characterised as follows: (i) Integrated (INT): weakest form expression, most advanced deterioration; (ii) Conversion to Biodynamic without horn silica (BD0): strongest form expression, advanced deterioration; (iii) Conversion to Organic (ORG): weak form expression, low deterioration; (iv) Conversion to Biodynamic with 3 × horn silica (BD3): medium form expression, low deterioration; (v) Conversion to Biodynamic with 4 × horn silica (BD4): strong form expression, low deterioration. Principal component analysis (PCA) of field assessment and chemical analysis data revealed that the two treatments with the strongest form expression, BD0 and BD4, were characterised by high vigour, as indicated by high prune weight and primary amino nitrogen (NOPA). With respect to the resistance to deterioration, as depicted by image forming methods, no parallels were found with PCA.

Pre-fermentation supplementation of mango must with ammonium and primary amino nitrogen influences mango wine chemistry

Mango wine is a shelf-stable value-added product that can be produced from fresh mango, mango juice or mango concentrate. Mango wine production techniques including cultivar selection, yeast strain selection and pressing conditions have been investigated, but no prior work has examined the effect of nitrogen supplementation on mango wine fermentation performance. After sugar, yeast assimilable nitrogen (YAN) is the most important nutrient required for yeast growth and metabolism during fermentation. In this study, the effect of supplementation of mango must with YAN on fermentation kinetics, residual sugar in mango wine, and residual yeast assimilable nitrogen in mango wine were determined. Nitrogen sources investigated included diammonium phosphate at two concentrations (100 mg/L and 200mg/L) and Fermaid O at two concentrations (100mg/L and 200mg/L). Initial YAN in mango must was 70mg/L, and increasing YAN concentration with either exogenous nitrogen source led to increased fermentation rate. Supplementation to the same initial YAN concentration of approximately 100 mg/L YAN with Fermaid O resulted in lower residual sugar in mango wine as compared to supplementation to the same initial YAN concentration with DAP. Conversely, residual YAN concentration in mango wine was higher when Fermaid O was the source of exogenous nitrogen.

Using a dynamic stomach model to study efficacy of supplemental enzymes during simulated digestion

In vitro static digestion models, with constant pH and volume, are commonly used to evaluate supplementary enzyme activity. The research objective was to apply a dynamic stomach model, Dynamic Gastric Simulating Model (DGSM), to evaluate the efficacy of supplementary enzymes in assisting food digestion. DGSM incorporates compressive forces to disintegrate food, mimics continuous gastric emptying, and simulates gastric secretion that generated pH profiles similar to human stomach. Static and dynamic models were used to evaluate supplementary proteases (SPs) efficacy. Additionally, acid-stable supplementary fungal enzyme blends were tested on food matrix containing oil, starch, and tuna using DGSM. A prescribed pancreatic enzyme drug, CREON, was used as a comparison. In static model, porcine pepsin (PP) had higher proteolytic activities generating significantly higher average Tyrosine Equivalent (TE) concentrations at pH 1.3 and 3. DS Proteases generated comparable TE concentrations to PP at pH 5. Under DGSM, addition of DS Proteases and Peptidases generated significantly greater TE and Primary Amino Nitrogen (PAN) than PP alone. Main findings show enhanced food digestion upon adding supplementary enzymes and blends. Furthermore, DGSM showed great potential as being an alternative tool used to study enzyme performances inside the human stomach as affected by dynamic physiological conditions.

Accumulation and Prediction of Yeast Assimilable Nitrogen in New York Winegrape Cultivars

A three-year study was conducted to investigate the accumulation of yeast assimilable nitrogen (YAN) during the final weeks of ripening in seven winegrape cultivars grown in New York State and to assess the feasibility of predicting harvest YAN using linear regression models. Berry samples of Vitis vinifera cvs. Cabernet franc, Chardonnay, Merlot, Pinot noir, and Riesling and interspecific hybrid cvs. Noiret and Traminette were collected weekly from 49 vineyard sites across the Finger Lakes, Hudson Valley, Lake Erie, and Long Island growing regions from August through harvest. YAN concentrations in Cabernet franc, Riesling, and Traminette were generally low, averaging 200 mg/L. During the ripening period, linear regression models predicted harvest YAN up to five weeks before harvest (R2 = 81.6%). A decrease in YAN during ripening was observed across cultivars, caused primarily by decreases in ammonia (AMM), as primary amino nitrogen levels remained stable. Population distributions were used to estimate appropriate prophylactic nitrogen additions for each cultivar, minimizing the risk of deficiency or excess; this was most difficult with Chardonnay, Noiret, and Pinot noir, which had the highest and most variable YAN concentrations and subsequently run the greatest risk of oversupplementation with prophylactic additions.

Preharvest Prediction of Yeast Assimilable Nitrogen in Finger Lakes Riesling Using Linear and Multivariate Modeling

A three-year study was conducted to determine if regression models could be developed to predict yeast assimilable nitrogen (YAN) before harvest, using Riesling in the New York Finger Lakes region as a model. Berry samples were taken from 62 commercial Riesling vineyards around the Finger Lakes at veraison, two weeks before harvest, and harvest. Samples were measured for berry weight, Brix, pH, titratable acidity, ammonia, primary amino nitrogen, and yeast assimilable nitrogen (YAN). The average YAN concentration at harvest was 91.8 mg/L, and there were no significant differences in harvest YAN concentration among years. Linear regression models created using preharvest YAN concentrations (<i>p</i> &lt; 0.05) had a cross-validated R² (Q²) of 70%. Models using only preharvest ammonia had less predictive power (Q² = 63%) but may allow winemakers more analytical flexibility than those requiring complete YAN measurements. Models created using multiple linear regression provided better predictive power (Q² = 73.6%). Finally, a multivariate approach using partial least squares regression was used to create models with the highest predictive power (Q² = 74.2%). The additional analysis required to obtain values for additional prediction variables may limit the practicality of multiple linear regression and partial least squares approaches. Because many winemakers are not able to perform the analyses required to calculate YAN during the busy time of harvest, the development of these regression models as predictive tools may allow winemakers to use preharvest analysis to calculate accurate supplemental nitrogen additions, allowing targeted supplementation and lowering the risk of excessive prophylactic additions.

New applications for Schizosaccharomyces pombe in the alcoholic fermentation of red wines

SummaryThe fermentation of grape must using non‐Saccharomyces yeasts with particular metabolic and biochemical properties is of growing interest. In the present work, red grape must was fermented using four strains of Schizosaccharomyces pombe (935, 936, 938 and 2139), Saccharomyces cerevisiae 7VA and Saccharomyces uvarum S6U, and comparisons were made over the fermentation period in terms of must sugar (glucose + fructose), malic acid, acetic acid, ammonia, primary amino nitrogen, lactic acid, urea (a possible fermentation activator or precursor of other metabolites) and pyruvic acid (a molecule affecting vitisin formation and therefore colour stability) concentration. The colour intensity of the fermenting musts was also recorded. The Schizosaccharomyces strains consumed less primary amino nitrogen and produced less urea and more pyruvic acid than other Saccharomyces species. Further, three of the four Schizosaccharomyces strains completed the breakdown of malic acid by day 4 of fermentation. The main negative effect of the use of Schizosaccharomyces was strong acetic acid production. The Schizosaccharomyces strains that produced most pyruvic acid (938 and 936) were associated with better ‘wine’ colour than the remaining yeasts. The studied Schizosaccharomyces could therefore be of oenological interest.

Chiral dioxovanadium(V) Schiff base complexes of 1,2-diphenyl-1,2-diaminoethane and aromatic o-hydroxyaldehydes: Synthesis, characterization, catalytic properties and structure

A series of dioxovanadium(V) complexes of tridentate ligands obtained by monocondensation of chiral 1,2-diphenyl-1,2-diaminoethane and aromatic o-hydroxyaldehydes was synthesized. The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV–Vis, CD, 1H and 51V NMR). Single crystal X-ray analysis was performed with (VO 2L · H 2O) 2, denoted as ( 4 · H 2O) 2, where L is ( S, S)-1-amino-2-{(2′-oxido-4′,6′-dimethoxyphenyl)methylene}amino-1,2-diphenylethane. Crystal structure analysis revealed that ( 4 · H 2O) 2 contains oxo-bridged dimers of 4 joined with water molecules by hydrogen bonding interactions, and that two five-membered chelate rings in the dimeric molecule adopt different envelope conformations, one on the asymmetric carbon atom linked to the azomethine nitrogen and the other on the asymmetric carbon atom linked to the primary amino nitrogen. The ( S, S)- and ( R, R)-complexes bearing the methoxy substituent in positions 3 or 5 of the salicylidene moiety catalyze the oxidation of phenyl methyl sulfide by cumene hydroperoxide yielding the corresponding sulfoxide almost quantitatively with 34–39% enantiomeric excess.

Rapid Determination of Primary Amino Acids in Grape Juice Using ano-Phthaldialdehyde/N-Acetyl-L-Cysteine Spectrophotometric Assay

Low levels of yeast assimilable nitrogenous compounds (YANC) in grape juice have been associated with sluggish or stuck fermentations. In contrast, excessive levels may lead to the increased formation of ethyl carbamate. Wine yeasts mainly consume primary amino acids and ammonium during vinification. While the ammonium fraction is easily determined by the winemaker, no winery-suitable analytical method has been available to estimate the primary amino nitrogen fraction. This research evaluated a spectrophotometric procedure to measure the primary amino nitrogen fraction. The assay was based on the derivatization of primary amino groups with an <i>o</i>-phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC) reagent. The resulting isoindole derivatives formed rapidly and were stable at a wavelength of 335 nm. The procedure used a juice blank to account for the absorbance of non-derivative forming compounds in the juice. The assay was insensitive to proline, showed a 3.5% response to ammonium, and correlated with HPLC estimates (R²= 0.988). The relative standard deviations for replicated analyses ranged from 0.27 to 3.20%. Estimates made using this procedure were within the systematic errors for model solutions, and known additions of isoleucine to grape juices had recoveries of 97.6 to 101.3%. The relative accuracy, precision, rapid analysis times and use of low-toxic reagents suggest that this procedure, dubbed NOPA for `nitrogen by OPA9, is appropriate for use in wineries.

Binickel(II) complex of a new asymmetrical acyclic ligand: the X-ray crystal structure of [Ni 2L](ClO 4) 2 reveals alternating square-planar and octahedral nickel ions

The binuclear nickel(II) complex of the macrocyclic ligand H 2L which contains one N(CH 2) 2N and one N(CH 2) 2NH– moiety has been studied. In the mixed spin-state complex [Ni 2L][ClO 4] 2 ( 1), one nickel center is square-planar (low spin), accommodated by the smaller N 2O 2 cavity provided by the phenolic oxygens and N(CH 2) 2N nitrogens; the other nickel center is octahedral (high spin), accommodated by the larger cavity provided by the phenolic oxygens and N(CH 2) 2NH– nitrogens. Diethylenetriamine takes the skew configuration, which inhibits the full cyclization. This leads to one primary amino nitrogen and one acetyl oxygen on both sides of the octahedral nickel completing the fifth and sixth coordination sites. The Pauling covalent radius of low-spin Ni 2+ is ca. 0.20 Å shorter than that of high-spin Ni 2+, leading to considerably stronger in-plane ligand-field strength of N 2O 2 donors at the square nickel(II) relative to that of the octahedral nickel(II). Crystallographic data for ( 1): space group P-1, triclinic, a=11.573(2) Å, b=15.608(3) Å, c=10.943(2) Å, α=104.54(2)°, β=114.97(1)°, γ=82.62(1)°, Z=2, R=0.061, R w=0.079.