Headspace content

Following preliminary hypochlorite treatments, a coherent process path was identified and implemented. Corn starch was oxidized with 6.4% (w/w) hypochlorite for two hours and given a combined base-heat gelatinization process (Method A). This base material exhibited excellent physical characteristics (i.e., stable emulsion with 20% db lemon oil incorporation into an aqueous dispersion, low lemon oil vapor phase flux (low headspace content), lack of inherent flavor and aroma) and when finally tested for spray dried lemon oil (20% db) retention efficiency in a lab-scale mini-dryer, the viability of this polymer was ascertained. Nearly 70% of the added lemon oil was retained following the drying of this DE 1.45 starch, a measure of functionality matched only by gum arabic (34). 

Figure 1. Effect of hypochlorite addition on starch titratable acidity and lemon oil headspace content values.

Sample Polymer Content (% w/v) Headspace Content (% EStd)C Retention mini- Niro ... 

Protein-Type A Microspheres for Injection USP Perflutren headspace content Assay, container C 0.53... 

Protein-Type A Microspheres Injectable Suspension USP headspace content ... 

Dynamic headspace GC/MS. The distillation of volatile and semivolatile compounds into a continuously flowing stream of carrier gas and into a device for trapping sample components. Contents of the trap are then introduced onto a gas chromatographic column. This is followed by mass spectrometric analysis of compounds eluting from the gas chromatograph. 

Pimento Berry Oil. The pimento or allspice tree, Pimenta dioca L. (syn. P. officinalis, Liadl.), a native of the West Indies and Central America, yields two essential oils of commercial importance pimento berry oil and pimenta leaf oil. The leaf oil finds some use ia perfumery for its resemblance to clove leaf and cinnamon leaf oils as a result of its high content of eugenol. Pimento berry oil is an item of commerce with extensive appHcation by the flavor industry ia food products such as meat sauces, sausages, and pickles, and moderate use ia perfumery, where it is used primarily as a modifier ia the modem spicy types of men s fragrances. The oil is steam-distilled from dried, cmshed, fully grown but unripe fmits. It is a pale yellow Hquid with a warm-spicy, sweet odor with a fresh, clean topnote, a tenacious, sweet-balsamic-spicy body, and a tea-like undertone. A comparative analysis of the headspace volatiles of ripe pimento berries and a commercial oil has been performed and differences are shown ia Table 52 (95). 

Principle. The content of 1,4-dioxane in ether sulfates is determined by headspace gas chromatography according to the standard additions method. The method is suitable for all ether sulfates and gives reliable results independent of chain length distribution and water content. 

Ulberth F (1998) A rapid headspace gas chromatographic method for the determination of the butyric acid content in edible fats. Z Lebensm Unters Forsch 2o6A 305-3oy. 

Weigh 50 g of sample into the headspace flask with a magnetic stirrer bar. Add immediately 50 mL of 1.5% stannous chloride solution in hydrochloric acid, and close the vessel with the silicone-rubber septum and the screw-cap. Transfer the head-space flasks into the electric oven (or water-bath) heated at 80 °C for 1 h. After 15 min, take the flasks out of the oven and mix the contents with the magnetic stirrer, heated at 50 °C, for 1 min. Return the flasks to the electric oven and repeat the mixing of the samples every 15 min. After 1 h, take the flasks out of the oven, mix the contents of each flask for 1 min, and inject an aliquot of headspace (100-1000 xL) on to the GC column with a gas-tight syringe. 

Figure 8.26(A) is an example of a valve type interface [329]. Helium carrier gas is provided to the headspace saiq)ler and is split into two flow paths. One path is flow-controlled and provides a constant flow of carrier gas which passes from the headspace unit through the heated transfer line to the gas chromatograph. The second flow path is pressure-regulated and, in the standby mode, the seunple loop and seuapling needle are flushed continuously by the helium flow. At a time determined by the operator, the sampling needle pierces the septum and helium pressurizes the headspace vial to any desired pressure. The headspace gas is then allowed to vent through the sample loop. Once filled, the sample loop is placed in series with the normal carrier gas flow and its contents are driv Bbhrough the heated...

SPME/GC/MS is an efficient technique to reveal the presence of resinic substances in archaeological samples. Indeed, volatile terpenes are still present in very old archaeological samples (4000 years old), particularly in the case of compact matrixes, and can be trapped by the SPME fibre. In comparison with methylene chloride extraction, SPME is very specific and allows the direct analysis of the volatile terpenes content in complex mixtures including oils, fats or waxes. For this reason, headspace SPME is the first method to use when analysing an archaeological sample it will either allow the identification of the resin or indicate further sample treatment in order to detect characteristic triterpenes. The method is not really nondestructive because it uses a little of the sample but the same sample can be used for several SPME extractions and then for other chemical treatments. 

Combining solids that have previously been equilibrated at different relative humidities results in a system that is thermodynamically unstable, since there will be a tendency for moisture to distribute in the system so that a single relative humidity is attained in the headspace. As shown in Fig. 7, moisture will desorb into the headspace from the component initially equilibrated at a higher relative humidity and sorb to the component initially equilibrated at a lower relative humidity. This process will continue until both solids have equilibrated at the final relative humidity. The final relative humidity can be predicted a priori by the sorption-desorption moisture transfer (SDMT) model [95] if one has moisture uptake isotherms for each of the solid components, their initial moisture contents and dry weights, headspace volume, and temperature. Final moisture contents for each solid can then easily be estimated from the isotherms for the respective solids. 

Vinyl chloride monomer (VCM) is the main substrate for the manufacture of polymers used as packaging materials for food. Since VCM is considered by lARC to be a human carcinogen, monomer levels in PVC food packaging materials are strictly controlled. To ensure a safe product, the residual content of VCM in the finished material or article is limited to one mg per kg in the final product (Council Directive 78/142/EEC). Furthermore, VCM should not be detectable in foodstuflfs. Commission Directives 80/766/EEC and 81/432/ EEC give the method of analysis for official control of the VCM level in food packaging materials and in foods - gas-phase chromatography using the headspace method, after dissolution or suspension of samples in N,N-dimethylacetamide. Both residual monomer content of the polymer and... 

The next example (excerpt 5A) returns us to the analysis of PCBs in milk. Recall that Elompart et al. (2001) (excerpt 4C) used HSSPME techniques to detect PCBs in milk. Their stumbling block was the fat content. The original method worked fine on skim milk, but the fat contained in nonskim milk trapped the PCBs in the liquid phase (those pesky matrix effects ), rendering headspace (i.e., gas-phase) analysis of the PCBs disappointing at best. More promising results were obtained when the milk fat was first saponified with base (NaOH), a process that helps to release the PCBs from the fatty matrix. 

Finally, we note that carbon balance closures are generally poorer in the alcohols than in water. A control experiment in which the entire reaction was carried out without sample collection, and another in which reactor and contents were carefully weighed at each stage of reaction, offered no hint as to the fate of lost GO or products. We measured gas formation in the reactor headspace and found < 1% of initial carbon present as gaseous products, primarily methane. We suspect that glycerol and alcohols are forming ethers at the elevated reaction temperatures, and that these ethers are not detected in HPLC. We are continuing efforts to better understand interactions of the solvents with substrates and reaction products. 

ERH may be estimated by measuring the relative humidity of the headspace over a food in a small, sealed container hygrometrically, psychro-metrically or directly by measuring the moisture content of the air by gas chromatography. ERH can be estimated by moisture-related colour changes in paper impregnated with cobalt thiocyanate (Co(SCN)2) and compared to standards of known aw. 

The Basic Protocol describes the determination of water activity of a product using a chilled mirror dew-point water activity meter. Dew point is a primary measurement of vapor pressure that has been in use for decades (Harris, 1995). Dew-point instruments are accurate, fast, simple to use, and precise (Richard and Labuza, 1990 Snavely et al., 1990 Roa and Tapia de Daza, 1991). In a dew-point instrument, water activity is measured by equilibrating the liquid-phase water in the food sample with the vapor-phase water in the headspace, and then measuring the vapor pressure of the headspace. The basic principle involved in dew-point determinations of vapor pressure in air is that air may be cooled without change in water content until it saturates. The dew-point temperature is the temperature at which the air reaches saturation. It is determined in practice by measuring... 

The ratio of the sample volume to headspace volume should be large enough (close to 0.5) to minimize changes in water activity due to loss of water by vaporization. In samples of higher water content the ratio of sample to headspace volume could be lower. 

This group evaluated the impact of changes in fatty acid composition on headspace aldehyde content of fresh pork and demonstrated the utility of these saturated aldehydes as an indicator of lipid oxidation. 

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