Walter Jennings

Flavor composition of wines: a review.

The formation of flavor in fermented beverages is due to various biosynthetic mechanisms. In wine, flavors arise as the result of compounds: 1. Originating from the native fruit (grap) 2. Which are formed or altered during the various processes employed in production 3. Which are developed or transformed by yeast during fermentation 4. Arise during the aging process In this review the results of investigations on the development of flavors in grape and wine will be discussed. Special attention will be devoted to the effects of specific processes in winemaking on the development of flavor.

Theory and practice of hard-surface cleaning

Publisher Summary This chapter is concerned with the removal of soil from hard surfaces and the work done in textile and related fields has been considered. The manner in which a soil is attached to a substrate is related to the physical and chemical characteristics of both the soil and the substrate. Most cleaning processes are considered to consist of three primary steps: separation of the soil from the substrate; dispersion of the soil in the deterging medium; and prevention of soil redeposition on the substrate. Each of these phases involves mechanical, physical, and chemical considerations. There are a variety of factors to consider in choosing a particular detergent to remove a specific soil from a specific substrate. The chapter discusses the properties that one may wish to find in the detergent. Factors taken into account in selecting the proper detergent are: type of soil to be removed, type of substrate, water composition, and detergent complexity. Methods of detergent classification are based on the property for which that detergent will primarily be used for. The chapter also discusses the fact that the surface of a liquid is in an unbalanced state and that the surface tension is a measure of this imbalance. Much effort has been directed toward developing methods that would permit evaluation of detergent efficiency and the effect of specific variables on the detergent process. Direct and indirect means have been proposed for the evaluation of detergent efficiency.

Optimization of liquid phase mixtures

Abstract The concept of window diagrams has been used to predict what lengths of dissimilar fused-silica capillaries should be serially coupled to achieve the optimum separation of two “real world” samples whose separation on a single column has not yet been reported. Complicating factors, including the role of the solute partition ratio and the velocity gradient of the carrier gas, are discussed. Separations of mixtures of (a) volatiles produced by yeast fermentation, and (b) solvents used in the preparation of food packaging films, were achieved in single passes on properly configured serially coupled columns composed of two precise lengths, one coated with polymethylsiloxane, and the other with polyethylene glycol.

New approach to chromatographic optimizationin glass capillary gas chromatography

Abstract A system for achieving mechanically valved recycle chromatography in small bore glass capillary columns is described. The system is capable of achieving extreme resolution in comparatively short time (e.g. over 2,000,000 theoretical plates in 16 min) and can be designed to permit optimization of column length and liquid phase polarity.

Kinetic studies of detergency. I. Analysis of cleaning curves

The kinetics of removal of thin films of pure radioactive tristearin from a stainless-steel surface by .03M NaOH was studied in a circulation system. The data obtained are consistent with the presence of two species of tristearin, each species being removed simultaneously by a first-order process and behaving independently of the other. The principal evidence for the existence of the two species is the excellent agreement of the experimental data with the mathematical techniques of kinetics over a wide range of experimental conditions. Rate constants for the removal of each species and the relative proportions of the two species are given for different experimental conditions. It is shown that the difference between the two species must be based on some physical factor, and possible explanations are discussed. The presence of two species gives a satisfactory explanation for hitherto unexplained results of other workers.

Developments in Arson Analysis: A Comparison of Charcoal Adsorption and Direct Headspace Injection Techniques Using Fused Silica Capillary Gas Chromatography

Procedures that have been explored for the extraction or concentration or both of fire accelerant materials from arson residues include direct headspace injection, steam distillation, charcoal adsorption followed by thermal or solvent elution, and on-column headspace injection of vapor samples, combined with cryogenic focusing. Because of the advantages to be gained from improved separations and increased sensitivity, it seemed advisable to use capillary column gas chromatography with whatever method was ultimately selected. The results of previous studies led to a decision to compare (1) a modified carbon wire adsorption technique and (2) cryogenic focused vapor samples directly injected on-column. Based on our experiences with the charcoal and cryogenic focusing techniques (in presence of water), the cryogenic method is an appropriate and satisfactory technique. Concentration methods (for example, distillation and adsorption) have been faulted for engendering quantitative and qualitative changes in the sample. Direct headspace injections of the type investigated here exercise less effects. They are simple to perform, require minimum sample preparation, and result in superior case sensitivity.

CHROMATOSTRIP ISOMERIZATION OF TERPENES.

Abstract Isomerization of the monoterpene hydrocarbons of black pepper oil occurred during isolation by thin-layer chromatography. α-Thujene, α-pinene, β-pinene, myrcene, 3-carene, limonene, β-phellandrene, ψ-terpinene, terpinolene and p -cymene were each eluted from chromatostrips and were all found to chromatograph without change. Sabinene isomerized to α-thujene, α-terpinene, ψ-terpinene, limonene, β-phellandrene and terpinolene when so treated. A possible mechanism for this reaction is discussed. Oxidation of α-terpinene and α-phellandrene to p -cymene occurred both in the control samples and on chromatostrips. In the silica-gel-induced isomerization of sabinene, α-phellandrene and p -cymene were formed in addition to the chromatostrip isomerization products. The results indicated that p -cymene was formed from α-terpinen and α-phellandrene.

Kinetic studies of detergency. II. Effect of age, temperature, and cleaning time on rates of soil removal

The effects of variation in temperature, flow rate, cleaning time, and age were studied in a model circulation system. The results are recorded as changes in the rate constants k1 and k2 and changes in the relative proportions of the two soil species. The removal of tristearin in this simple system was found to proceed by two independent mechanisms, acting simultaneously. The first, named the “flow mechanism,” is dependent on time, and its rate increases with flow rate. The second, which the authors term the “Dupré mechanism,” is not dependent upon time and arises from the air-detergent interface that moves over the surface. The Dupré effect is independent of flow rate at all rates of flow. In most of the experiments the Duprè mechanism accounted for about 90% of the removal of tristearin. A comparison is made between the removal of monomolecular films and thin polymolecular films. It is shown that the empirical finding of apparently simple first-order kinetics is not inconsistent with the complex processes that remove tristearin from the surface.

HRGC and HRGC-MS applied to wine constituents of lower volatility

ZusammenfassungDie Aromastoffe des Weines (Riesling, Jahrgang 1984) wurden durch Flüssig-Flüssig-Extraktion mit Trichlorfluormethan/Dichlormethan (9 + 1, v/v) angereichert. Die Extrakte wurden mit Capillargaschromatographie und Capillargaschromatographie-Massenspektrometrie (EI) auf apolaren stationären Phasen analysiert, um die Komponenten von geringerer Flüchtigkeit zu untersuchen. Es wurden 12 Phenole, 3 Indole, 2 Lactone und 5 sonstige Komponenten des Weinaromas identifiziert. Von den 22 Substanzen sind 7 bisher noch nicht als Aromastoffe in Weißwein (5 davon in Wein) publiziert worden.[/p]AbstractThe constituents of a White Riesling wine (vintage 1984) were isolated by continuous liquid-liquid extraction with trichlorofluoromethane/dichloromethane (9+1, v/v). The extracts were analysed by capillary gas chromatography and capillary gas chromatography-mass spectrometry (EI) on apolar stationary phases to investigate compounds of lower volatility. The identified constituents included 12 phenols, three indoles, two lactones and five miscellaneous wine compounds. Of the 22 substances identified, seven are reported for the first time in white wine (five of these in wine).[/p]

Kinetic studies of detergency. III. Dependence of the duprȳ mechanism on surface tension

The kinetics of the removal of thin films of pure radioactive tristearin from a stainless steel surface by detergent solutions in a circulation cleaning system were used to study the effect of the surface tension of the detergent solution on the Dupré mechanism and the flow mechanism.Lowering the surface tension reduced the effectiveness of the Dupré mechanism for both species 1 soil and species 2 soil, as expected. Lowering the surface tension increased the efficiency of the flow mechanism for both species of soil, but, at the present time, it is not known how much of the increase can be ascribed to the lowered surface tension, and how much is due to the increased concn of the surfactant that was used to lower surface tension.