Combinatorial synthesis and sensorial properties of polyfunctional thiols.

Over the past few years, polyfunctional thiols present as trace components have been found to play a major role in many food flavors, due to their exceptionally low odor thresholds. Unfortunately, their presence in minute concentration (in ng/kg to a few microg/kg) and their high reactivity make it very difficult to extract and identify them. Furthermore, most of them are not yet commercially available. The aim of this work was to characterize the chromatographic and sensorial properties of 10 synthetic mercaptoketones and mercaptoalcohols. Combinatorial chemistry proved to be a very useful way to synthesize them rapidly. Sulfur-selective sulfur chemiluminescence detection chromatograms coupled with mass spectroscopy enabled the target compounds to be identified. Flavor profiles and best estimate gas chromatography lowest amount detected by sniffing (BE-GC-LOADS) values were further determined by GC-olfactometry. As expected, new, exceptionally odorant molecules (BE-GC-LOADS < 0.1 ng) were revealed by this unusual approach.     

Synthesis and sensorial properties of 2-alkylalk-2-enals and 3-(acetylthio)-2-alkyl alkanals

Parallel synthesis was applied to prepare a series of 3-(acetylthio)-2-alkyl alkanals by Michael addition of thioacetic acid under alkaline conditions to alpha,beta-unsaturated 2-alkyl-substituted aldehydes, which were obtained by aldol condensation of the corresponding primary aldehydes as starting materials. The target compounds were characterized in terms of GC, MS, and NMR data. The sensory properties of the odorants, such as odor quality and odor detection threshold value, were determined with a trained panel. Structure-activity relationships are discussed, suggesting that the 1,3-oxygen-sulfur functionality, required for the "olfactophore" of tropical/vegetable notes, can further be extended to the acetylthio derivatives.     

Role of aldehydic derivatives in the condensation of phenolic compounds with emphasis on the sensorial properties of fruit-derived foods

The reactions between (epi)catechin, mavidin 3-O-glucoside, and some aldehydes were investigated by LC/DAD and LC/ESI-MS analysis. The obtained results showed that the acetaldehyde-mediated condensation occurred more generally and glyoxylic acid, furfural, and 5-(hydroxymethyl)furfural (HMF) react in the same way in the first stages of the reactions. In terms of reactivity, reactions were faster with acetaldehyde than with glyoxylic acid, furfural, or HMF, where the reactions were slower. In the case of acetaldehyde, the obtained purple derivatives were more predominant and stable than the colorless adducts and no xanthylium salt was detected. Interactions involving glyoxylic acid yield purple adducts, which were obtained in small amount compared to the colorless ones. The latter were shown to proceed to more polymerized and yellowish derivatives. Finally, in the case of furfural and HMF, purple compounds involving flavanol and anthocyanin units were detected, and colorless compounds were shown to be predominant and to yield yellowish xanthylium salts.     

Chemical and sensorial characteristics of espresso coffee as affected by grinding and torrefacto roast

Grinding is a critical step in the preparation of espresso coffee (EC). The addition of sugar during the torrefacto roasting process could influence the degree of brittleness and grinding. The aim of this work was to study the influence of the grinding grades (coarse, fine, and very fine) in Arabica/Robusta 20:80, natural roasted (A20:R80), and Arabica/Robusta 20:80 with 50% Robusta torrefacto roasted (A20:R80 50% torrefacto) on the chemical and sensorial characteristics of EC in order to select the optimal espresso grinding grade. A higher percentage of coarse particles was found in A20:R80 ground coffee. In both ECs, the extraction of solids and soluble and aroma compounds increased inversely with particle size. Higher foam indices and extraction yields were found in A20:R80 50% torrefacto ECs probably due to the solubilization of caramelized sugar and melanoidins. It has been suggested that the range of an acceptable extraction yield could be extended to 25% in A20:R80 50% torrefacto ECs. In conclusion, the optimal grinding grade for the obtainment of an EC with A20:R80 was fine and that for A20:R80 50% torrefacto was coarse.     

Synthesis and properties of immobilized pectinase onto the macroporous polyacrylamide microspheres

Pectinase was covalently immobilized onto the macroporous polyacrylamide (PAM) microspheres synthesized via an inverse suspension polymerization approach, resulting in 81.7% immobilization yield. The stability of the macroporous PAM support, which has a large surface area, is not impeded by the adsorbed proteins despite the fact that up to 296.3 mg of enzyme is immobilized per gram of the carrier particles. The immobilized enzyme retained more than 75% of its initial activity over 30 days, and the optimum temperature/pH also increased to the range of 50-60 °C/3.0-5.0. The immobilized enzyme also exhibited great operational stability, and more than 75% residual activity was observed after 10 batch reactions. The kinetics of a model reaction catalyzed by the immobilized pectinase was finally investigated. Moreover, the immobilized pectinase could be recovered by centrifuging and showed durable activity at the process of recycle.     

稀土农膜转光材料合成与性质研究

采用乙醇 水溶液析出法合成了 1 1种以稀土三价铕离子为中心离子 ,以 β二酮 (α 噻吩甲酰三氟丙酮、二苯甲酰甲烷、苯甲酰丙酮 )和芳香羧酸 (肉桂酸、烟酸 )为主配体 ,有机胺类 (邻菲咯啉、三辛胺、三乙胺 )为协同配体的二元及三元配合物 ,通过荧光光谱和TG DTA谱线分析配合物荧光性能及热力学稳定性结果表明 ,所合成的配合物中仅三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ )和三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ )荧光强度高于对照 ,且依次为三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ ) >三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ ) >对照。三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ )和三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ )起始分解温度分别为 2 2 0℃和 2 5 0℃ ,高于膜的加工温度 ,可满足生产需要。而三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ )生产成本低于对照和三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ ) ,因而更具竞争优势     

Chemical and sensorial aroma characterization of freshly distilled Calvados. 2. Identification of volatile compounds and key odorants

Eight samples of freshly distilled Calvados were extracted using pentane. Gas chromatography with either a mass spectrometer or flame ionization detector was used to determine the volatile compounds composition of the extracts. More than 120 molecules were identified in Calvados and then correlated with results obtained by olfactometric analysis in our earlier work [Guichard, H.; Lemesle, S.; Ledauphin, J.; Barillier, D.; Picoche, B. Chemical and Sensorial Aroma Characterization of Freshly Distilled Calvados. 1. Evaluation of Quality and Defects on the Basis of Key Odorants by Olfactometry and Sensory Analysis. J. Agric. Food Chem. 2002, 50, 424-432 (preceding paper in this issue)]. Of these, 16 of the 19 molecules that constitute the "aroma skeleton" were identified, including 5 esters, 2 ketones, 5 phenolic derivatives, 2 alcohols, and 2 carboxylic acids. Numerous compounds were also associated with odors found in part 1. These molecules can be considered as being responsible for the good quality of Calvados or, in contrast, for defects. Relative levels of some major olfactive compounds were also estimated and tentatively compared with olfactometric indices found in part 1. A good correlation was found in many cases. Two important markers of defects in Calvados were also identified. 3-Methylbut-2-en-1-ol leads to an "herbaceous" defect, and 1,1,3-triethoxypropane seems to give an "acrolein" defect in the product. "Floral" notes of the aroma of freshly distilled Calvados seem to be due to the presence of phenolic derivatives such as 2-phenylethanol and 2-phenylethyl acetate. Low-molecular-weight esters such as ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, and 3-methylbutyl acetate give, in general, the "fruity" notes. However, the overall aroma of Calvados seems likely to be a subtle balance of various functionalized compounds.     

Combined effect of ascorbic acid and gamma irradiation on microbial and sensorial characteristics of beef patties during refrigerated storage

The present study was undertaken to evaluate the effect of ascorbic acid concentrations (0.03 to 0.5%) and irradiation doses (0.5 to 4 kGy) on microbial growth, color coordinates (L, a, and b), and sensory characteristics (taste and odor) of beef patties during storage at 4 +/- 1 degrees C. Ascorbic acid was also compared to citric acid at a similar pH value in order to differentiate the effects of ascorbic acid from those of pH reduction. Results showed significant reduction (p< or = 0.05) of aerobic plate counts (APCs) and total coliforms, and a significant interaction (p< or = 0.05) between ascorbic acid and irradiation dose was observed. The irradiation treatment had detrimental effects on redness, yellowness, and hue angle values of meat. However, incorporation of ascorbic acid into the meat before irradiation resulted in significant (p< or = 0.05) stabilization of color parameters. The color improvement obtained with ascorbic acid was not related to the pH reduction. Also, no significant detrimental effect on taste or odor was found in irradiated samples containing ascorbic acid.     

Relationship between potentiometric measurements, sensorial analysis, and some substances responsible for aroma degradation of white wines

Oxidative degradation of white wines can be described sensorially as developing from a loss at positive aroma characteristics, through the development of negative aromas to a linel stage of chromatic alterations. This work attempts to relate the oxidation "status" evaluate by potentiometric titrations, with sensorial degradation and the levels of substances responsible for "off-flavors", such as methional and phenylacetaldehyde. The potentiometric titration employed measures the most powerful antioxidants of white wines (e.g., those which more rapidly consume oxygen). Considering that aromatic precedes chromatic degradation, resistance to oxidation (ROX) constitutes a useful indicator of resistance to oxidation. Sensorial degradation (ID), potentiometric measures, and volatiles were determined both in samples submitted to a "forced aging" protocol and normal aged white wines. High correlation values were observed between ROX and the ID, in both sets (r > 0.87). ID is better explained by ROX values than by the indicated wine age or by the "degree of browning" (Abs = 420 nm). It was also observed that in samples with ROX values higher than 10, the concentration of methional and phenylacetaldehyde were above their respective odor threshold. Finally, it was observed that there is a relationship between oxygen consumption and the respective ROX. Although these results seem very promising, they needed to be further complemented in order to estimate the shelf life of a white wine using potentiometric titrations.     

Combined use of starter cultures and preservatives to control production of biogenic amines and improve sensorial profile in low-acid salami

The combined effect of starter culture, nitrites, and nitrates has been studied in low-acidity salamis, typical products of northern Italy. Nine batches have been prepared, combining three different inoculations of starter cultures (control, Lactobacillus plantarum , and Lactobacillus plantarum together with Kocuria varians ) with three different preservatives (control, sodium nitrate, and sodium nitrite). All of the batches showed a good fermentation process with a proper pH decrease, which was quicker in batches inoculated with L. plantarum. The use of starter cultures and in particular the use of nitrites allowed the control of the proliferation of Enterobacteriaceae and enterococci. The accumulation of biogenic amines, especially putrescine, cadaverine, tryptamine, and tyramine, in salami ready for consumption (60 days of ripening) was strongly affected by the presence of Enterobacteriaceae and enterococci. Results obtained showed that the combined use of adequate preservatives and starter cultures allows the production of safer products with improved sensorial profile.     

SA-IP-SPS型保水剂及其对土壤物理性能的影响

以未经预处理的工业级丙烯酸、聚乙烯醇为原料，首先通过氯磺酸磺化法在聚乙烯醇分子中引入强亲水性离子基团，然后采用静态水溶液聚合法合成了吸盐水率较高、凝胶机械强度较高的的聚丙烯酸钠-聚乙烯醇硫酸钠互穿网络(SA-IP-SPS）型保水剂。研究了SA-IP-SPS型保水剂含量、颗粒大小对南方赤红壤的水分抑蒸发性能和团粒结构的影响，比较研究结果表明，SA-IP-SPS型保水剂对赤红壤的水分抑蒸发性能和团粒结构改良性能与丙烯酸-丙烯酰胺交联共聚型保水剂效果相当，但明显优于传统的交联聚丙烯酸钠保水剂。     

Effect of aging on lees and of three different dry yeast derivative products on Verdejo white wine composition and sensorial characteristics

A study was made of the effect of aging on lees and of three different commercial yeast derivative products of different composition and degree of purification on the phenolic compounds, color, proteins, polysaccharides, and sensorial characteristics of white wines. The results obtained showed that the lees and yeast derivative products can interact or adsorb some of the phenolic compounds present in wines, reducing their concentration. This reduction depends on the treatment applied, the phenolic compound analyzed, and the stage of vinification or aging process. The use of lees and yeast derivative products can reduce the color intensity and the browning of the wines immediately following treatment. The monosaccharide and polysaccharide content of yeast derivative products depends on the manufacturing process and degree of purification of the product, both of which have an influence on wine treatments. After 6 months in the bottle, both the aging on lees and the treatment with commercial yeast derivative products gave rise to wines with better sensorial characteristics than in the case of the control wines.     

松香凹凸棒石粘土包膜尿素的制备及缓释性能的研究

矿物和有机物复合包膜有利于提高肥料的利用效率.以松香的无水乙醇溶液为粘结剂,凹凸棒石粘土作为内包层,石蜡作为外层,采用熔融喷雾包膜的方法制备一种缓释包膜尿素.通过扫描电镜( SEM)分析得出,尿素内部形成一层以松香和凹凸棒石粘土为内包层的均匀膜,根据水浸泡试验和抗压强度测定表明,添加凹凸棒石粘土增加了包膜层的强度,松香...     

Lactones. 21. Synthesis and odoriferous properties of lactones with the p-menthane system

Starting from (R)-(+)- and (S)-(-)-pulegone, enantiomeric pairs of esters and lactones with the p-menthane system were obtained. The Claisen rearrangement of allylic alcohols and iodolactonization of gamma,delta-unsaturated acids were the key steps of syntheses presented. The structures of compounds were determined by both spectroscopic and crystallographic methods. Some of the synthesized compounds are characterized by interesting odoriferous properties.     

Analytical and sensorial characterization of the aroma of wines produced with sour rotten grapes using GC-O and GC-MS: identification of key aroma compounds

In the present work, the aroma profiles of wines elaborated from sound and sour rot-infected grapes as raw material have been studied by sensory analysis, gas chromatography-olfactometry (GC-O), and gas chromatography-mass spectrometry (GC-MS), with the aim of determining the odor volatiles most likely associated with this disease. The effect of sour rot was tested in monovarietal wines produced with the Portuguese red grape variety Trincadeira and in blends of Cabernet Sauvignon and sour rotten Trincadeira grapes. Wines produced from damaged berries exhibited clear honey-like notes not evoked by healthy samples. Ethyl phenylacetate (EPhA) and phenylacetic acid (PAA), both exhibiting sweet honey-like aromas, emerged as key aroma compounds of sour rotten wines. Their levels were 1 order of magnitude above those found in controls and reached 304 and 1668 μg L(-1) of EPhA and PAA, respectively, well above the corresponding odor thresholds. Levels of γ-nonalactone also increased by a factor 3 in sour rot samples. Results also suggest that sour rot exerts a great effect on the secondary metabolism of yeast, decreasing the levels of volatiles related to fatty acids and amino acid synthesis. The highest levels of γ-decalactone of up to 405 μg L(-1) were also found in all of the samples, suggesting that this could be a relevant aroma compound in Trincadeira wine aroma.     

Synthesis of soybean oil-based polymeric surfactants in supercritical carbon dioxide and investigation of their surface properties

This paper reports the preparation of polymeric surfactants (HPSO) via a two-step synthetic procedure: polymerization of soybean oil (PSO) in supercritical carbon dioxide followed by hydrolysis of PSO (HPSO) with a base. HPSO was characterized and identified by using a combination of FTIR, (1)H NMR, (13)C NMR, and GPC methods. The effects of HPSO polysoaps on the surface tension of water and interfacial tension of water-hexadecane were investigated as a function of concentration of HPSO and counterion chemistry. HPSO polysoaps were effective at lowering the surface tension of water and the interfacial tension of water-hexadecane. They displayed minimum values of surface tension in the range of 20.5-39.6 dyn/cm at a concentration range of 3.2-32 μM and minimum values of interfacial tension in the range of 15.6-31.44 dyn/cm. The minimum surface and interfacial tension values were highly dependent on the nature of the counterion and increased in the order K(+) < Na(+) < TEA(+). These results suggested that a very low concentration of surfactant can be used to reduce the surface tension of water and interfacial tension of water-hexadecane. Water-hexadecane interfacial energy was also calculated from measured surface tension data using Antonoff, harmonic mean (HM), and geometric mean (GM) methods. Measured values agreed well with those calculated using the HM and GM. The HM method predicted slightly higher values than the GM method, but the Antonoff method did not agree with measured values.     

Synthesis of methacrylic-ferulic acid copolymer with antioxidant properties by single-step free radical polymerization

A novel, simple, and cheap method to synthesize antioxidant methacrylic-ferulic acid copolymer (PMAA-FA) by free radical polymerization was developed by employing a hydrogen peroxide-ascorbic acid pair to produce hydroxyl radicals acting as radical initiators. FT-IR spectra were performed to verify the insertion of ferulic acid into the polymeric chain, and the antioxidant activity of PMAA-FA was compared to that of a control polymer synthesized in the absence of antioxidant molecule. Good antioxidant activity was demonstrated by obtained materials, showing the efficiency of the polymerization method. This material could be useful in the pharmaceutical field and in the food industry (food packaging).     

Effect of decontamination agents on the microbial population, sensorial quality, and nutrient content of grated carrots (Daucus carota L.)

Several decontamination agents including water, sodium hypochlorite, peroxyacetic acid, neutral electrolyzed oxidizing water, and chlorine dioxide gas were tested for their effectiveness to reduce the natural microflora on grated carrots. Microbial reductions of the total aerobic count obtained after the different treatments varied between 0.11 and 3.29 log colony-forming units (cfu)/g. Whether or not a decontamination step induced significant changes in the sensory attributes of grated carrots is highly dependent on the type and concentration of disinfectant. To maintain the nutritional value, the influence of the decontamination agents on carotenoid content, alpha-tocopherol content, total phenols, and antioxidant capacity was studied. Besides the part of the nutrients that was leached away from the cutting areas by water, the nutrient losses caused by adding sanitizers were rather limited. Compared with the untreated carrots alpha-tocopherol content was, however, significantly reduced when 250 ppm of peroxyacetic acid (-80%) or 200 ppm of sodium hypochlorite (-59%) was used. Additional losses in carotenoid content were caused by contact with chlorine dioxide gas (-9%). On the condition of an optimized decontamination process toward time and concentration, the microbial quality of fresh-cut carrots could be improved without negatively influencing their sensory quality and nutrient content.