Paste colour

Finally, an exhaustive study of some of the variables affecting the measurement of tomato paste colour has been carried out as part of the COST 90 programme by Brimelow (1987). The effects of such factors as paste dilution, test duration, instrument aperture size and illumination area, sample temperature, standardisation hitching-post tile temperature, and the presence or absence of extraneous light were all examined. A standard colour measurement procedure was advocated for this important food commodity. As a parallel effort in this work, a new European standard tomato red tile was specified by the COST 90 colour group participants, to act as a hitching post in the measurement of tomato pastes and purees. 

When in-situ neutralisation is not possible, pastes are stored in agitated tanks of up to 100 tons capacity. Heating coils should be provided with hot water (80 C). Pitting of mild steel will eventually occur and, as freedom from iron contamination is important for on paste colour, stainless steel or glass-reinforced polyester tanks should be used. 

The quality of alkylbenzene sulphonate from 20% oleum plants is normally very good. The free oil figures fall in a range between 0.6 and 1.7% on 100% AD. Due to the dissolved sulphuric acid in the sulphonic acid phase, the sodium sulphate levels on 1(X)% AD vary between 6 and 15% depending on the type of alkylate and the efficiency of the separation process of sulphonic acid/spent acid. Paste colour is normally very good, wiA values well below 1(X) Klett (5% AD solution, 4 cm cell, F42 filter). 

Transfer 30 g. of the hydrochloride to a 500 ml. separatory funnel, add 100 ml. of water and shake until a thin paste of uniform consistency is obtained add 10 per cent, aqueous sodium hydroxide solution in the cold with shaking until the whole mass has become bright green (the colour of the free base) and the mixture has an alkaUne reaction. Extract the free base by shaking with two 60 ml. portions of benzene (1). Dry the combined benzene extracts with a Uttle anhydrous potassium carbonate, and filter into a distiUing flask fitted with a water condenser. Distil off about half of the benzene, and pour the residual hot benzene solution into a beaker. Upon cooUng, the p-nitrosodimethylaniUne erystallises in deep green leaflets. Filter these off and dry them in the air. The yield of p-nitrosodimethylaniUne, m.p. 85°, from the hydrochloride is almost quantitative. 

Add 101 g. (55 ml.) of concentrated sulphuric acid cautiously to 75 ml. of water contained in a 1 htre beaker, and introduce 35 g. of finely-powdered wi-nitroaniline (Section IV,44). Add 100-150 g. of finely-crushed ice and stir until the m-nitroaniUne has been converted into the sulphate and a homogeneous paste results. Cool to 0-5° by immersion of the beaker in a freezing mixture, stir mechanically, and add a cold solution of 18 g. of sodium nitrite in 40 ml. of water over a period of 10 minutes until a permanent colour is immediately given to potassium iodide - starch paper do not allow the temperature to rise above 5-7° during the diazotisation. Continue the stirring for 5-10 minutes and allow to stand for 5 minutes some m-nitrophenjddiazonium sulphate may separate. Decant the supernatant Uquid from the solid as far as possible. 

Now take another batch of sulphur flowers, but this time heat it well past its melting point. The liquid sulphur gets darker in colour and becomes more and more viscous. Just before the liquid becomes completely unpourable it is decanted into a dish of cold water, quenching it. When we test the properties of this quenched sulphur we find that we have produced a tough and rubbery substance. We have, in fact, produced an amorphous form of sulphur with radically altered properties. 

During the past decade there has been an astonishing proliferation of further binary earbon-sulfur speeies, both anionie and neutral. Of the anions, the beige coloured dianion (made from tctrachloroeyelopropenc) has the /J3/, strueturc (I) and the yellow QS4 (made from squarie aeid, p. 312) has the D, slrueture (2). The off-while CfiSf, ", (3), (made from... 

During the past 20 y numerous other highly coloured halogen cations have been characterized by Raman spectroscopy. X-ray crystallography, and other techniques, as summarized in Table 17.18. Typical preparative routes involve direct oxidation of the halogen (a) in the absence of solvent, (b) in a solvent which is itself the oxidant (e.g. AsFs) or (c) in a non-reactive solvent (e.g. SO2). Some examples are listed below ... 

Ink is a fluid or paste having an intense colour. Inks comprise a pigment or dye as the chromophore dissolved or dispersed in a liquid called the vehicle. 

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