Pressed distillate

Cold-pressed Distilled Cold pressed Distilled ... 

Adapted from Wang el at. (1997) with permission from Food and Nutrition Press. Distillation methods were described by Tarladgis el al. (I960). Rhee (1978), and Moerck and Ball (1974). Extraction methods were described by Sinnhuber and Yu (1977) and Witte et al. (1970). Results are expressed as mg malonaldehyde eq/kg meat sample. 

Bright stock solution, like pressed distillate, must be distilled with as little discoloration as possible. Several two-flash systems have been built. In the first flash, the naphtha is removed. The residue is then further heated in a part of the pipestill, and gas oil and a neutral oil are vaporized in the second fla. The tw6-flash system holds no important advantages over the single-flash system, but as an illustration the two-flash method of operation is shown in Fig. 7-18. Evaluation curves are shown in Fig. 7-19> The steam required in a pipestill rerun system is often less than one-fifth the amount required by shellstill redistillation.. Modem practice is tending toward single- rather than two-flash systems. 

Fig. 7-16. Diagram of a steam-atmospheric pressed-distillate rerun plant. (A stripper is usually employed for the side-draw product.) Srrdih Engineering Co,)...

Vacuum Dbtillation. Vacuum distillation may be employed for the redistillation of pressure distillate, pressed distillate, or bright stock solution. It may be used for distilling topped crude oils for the production of wax distillate and cylinder stock, or it may be used to reduce a residual stock to asphalt or pitch. Vacuum systems are widely used to produce catalytic cracking plant feed stocks of low carbon content. 

Fit securely to the lower end of the condenser (as a receiver) a Buchner flask, the side-tube carrying a piece of rubber tubing which falls well below the level of the bench. Steam-distil the ethereal mixture for about 30 minutes discard the distillate, which contains the ether, possibly a trace of unchanged ethyl benzoate, and also any biphenyl, CeHs CgHs, which has been formed. The residue in the flask contains the triphenyl carbinol, which solidifies when the liquid is cooled. Filter this residual product at the pump, wash the triphenyl-carbinol thoroughly with water, drain, and then dry by pressing between several layers of thick drying-paper. Yield of crude dry product, 8 g. The triphenyl-carbinol can be recrystallised from methylated spirit (yield, 6 g.), or, if quite dry, from benzene, and so obtained as colourless crystals, m.p. 162. ... 

Preparation of silver maleate. Dissolve 65 g. of pure maleic acid (Section 111,143) in the calculated quantity of carefully standardised 3-5N aqueous ammonia solution in a 1-htre beaker and add, whilst stirring mechanically, a solution of 204 g. of silver nitrate in 200 ml. of water. Filter oflf the precipitated silver maleate at the pump, wash it with distilled water, and press well with the back of a large flat glass stopper. Dry in an electric oven at 50-60° to constant weight. The yield of the dry silver salt is 150 g. Store in a vacuum desiccator in the dark. 

To isolate pure p-dibromobenzene, filter the second portion of the steam distillate through a small Buchner funnel with suction press the crystals as dry as possible. Combine these crystals with the residue (R) and recrystaliise from hot ethyl alcohol (for experimental details, see Section IV,12) with the addition of 1-2 g. of decolourising charcoal use about 4 ml. of alcohol (methylated spirit) for each gram of material. Filter the hot solution through a fluted filter paper, cool in ice, and filter the crystals at the pump. The yield of p-dibromobenzene, m.p. 89°, is about 12 g. 

Pour the resulting dark reddish-brown liquid into 500 ml. of water to which 17 ml. of saturated sodium bisulphite solution has been added (the latter to remove the excess of bromine). Steam distil the resulting mixture (Fig. II, 41,1) , collect the first portion of the distillate, which contains a little unchanged nitrobenzene, separately. Collect about 4 litres of distillate. Filter the yellow crystalline solid at the pump, and press well to remove the adhering liquid. The resulting crude m-bromonitrobenzene, m.p. 51-52°, weighs 110 g. If required pure, distil under reduced pressure (Fig. II, 19, 1) and collect the fraction of b.p. 117-118°/9 mm. it then melts at 56° and the recovery is about 85 per cent. 

Essentia.1 Oils. Essential oils (qv) are extracted from the flower, leaf, bark, fmit peel, or root of a plant to produce flavors such as mint, lemon, orange, clove, cinnamon, and ginger. These volatile oils are removed from plants either via steam distillation, or using the cold press method, which avoids heat degradation. Additional processing is sometimes employed to remove the unwanted elements from the oils, such as the terpenes in citms oils which are vulnerable to oxidation (49,50). 

Natural Products. Various methods have been and continue to be employed to obtain useful materials from various parts of plants. Essences from plants are obtained by distillation (often with steam), direct expression (pressing), collection of exudates, enfleurage (extraction with fats or oils), and solvent extraction. Solvents used include typical chemical solvents such as alcohols and hydrocarbons. Liquid (supercritical) carbon dioxide has come into commercial use in the 1990s as an extractant to produce perfume materials. The principal forms of natural perfume ingredients are defined as follows the methods used to prepare them are described in somewhat general terms because they vary for each product and suppHer. This is a part of the industry that is governed as much by art as by science. 

Aeration must be avoided since it can oxidize and resolubiUze the cemented (precipitated) impurities. Filter presses are used after each step and the cakes are leached to recover various values. For example, cadmium is dissolved, recemented with zinc, and recovered on site either electrolyticaHy or by distillation. A copper residue of 25—60% copper is sold for recovery elsewhere. The other impurities cannot be recovered economically with the exception of cobalt in some plants. 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

M. J. Lockett, Distillation Trcry Fundamentals, Cambridge University Press, Cambridge, Mass., 1986. 

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