Page 173 - Analytical method for food addtives

Reference
2
4
3
Transfer to photocell and determine A at 540 nm against
flask and dilute with water. Measure colour at 450 nm
add NED reagent, mix, let colour develop for 15 min.
Add sulphanilamide reagent to an aliquot, after 5 min
receiver containing NaOH. Transfer distillate to vol
Aqueous extract is treated with sulphanilamide and
Nitrate using m-xylenol. After nitration distil into
N-1(-naphthyl)ethylenediamine dihydrochloride.
Red compound produced is measured at 538 nm
Method conditions
blank
bath for 2 h. Cooled, diluted to volume.
Mixed with hot water, placed on steam
Mixed in warm water on steam bath,
Dispersed in warm water, fat and
transferred to volumetric flask
proteins precipitated, filtered
Sample preparation
Summary of methods for nitrites in foods 118 Analytical methods for food additives 5 Diazotisation of sulphanilic acid with the nitrite, and Clarification of aqueous extract with zinc Cheese coupling with 1-naphthylamine hydrochloride to form a hydroxide + NaOH. Placed on water bath pink azo dye whose absorbance is measured at 522 nm
Filter
Milk and milk
products
Matrix
Meat
Meat
Table 9.1 (a) Method Spectrometry Distillation/ spectrometric Colorimetric Reduction/ colorimetric Colorimetric Colorimetric Spectro- photometric