Premix Vitamin

Spectrophotometric deterrnination at 550 nm is relatively insensitive and is useful for the deterrnination of vitamin B 2 in high potency products such as premixes. Thin-layer chromatography and open-column chromatography have been appHed to both the direct assay of cobalamins and to the fractionation and removal of interfering substances from sample extracts prior to microbiological or radioassay. Atomic absorption spectrophotometry of cobalt has been proposed for the deterrnination of vitamin B 2 in dry feeds. Chemical methods based on the estimation of cyanide or the presence of 5,6-dimethylben2irnida2ole in the vitamin B 2 molecule have not been widely used. 

Various aspects of the chromatography of vitamin B 2 and related corrinoids have been reviewed (59). A high performance Hquid chromatographic (hplc) method is reported to require a sample containing 20—100 p.g cyanocobalamin and is suitable for premixes, raw material, and pharmaceutical products (60). 

The standard chemical and biological methods of analysis are those accepted by the JnitedStates Pharmacopeia XXIII as well as the ones accepted by the AO AC in 1995 (81—84). The USP method involves saponification of the sample (dry concentrate, premix, powder, capsule, tablet, or aqueous suspension) with aqueous alcohoHc KOH solvent extraction solvent removal chromatographic separation of vitamin D from extraneous ingredients and colormetric deterrnination with antimony trichloride and comparison with a solution of USP cholecalciferol reference standard. 

The addition of sugar required a different formulation for MCSM from the proportions stipulated by the commodity specification (11). Also, in lieu of the usual procedure of mixing commodities in a given proportion to formulate corn-soy-milk, protein and fat percentage levels of MCSM were set identically to those specified for CC. Cornmeal, defatted soy flour and soy oil proportions were then adjusted by computer to meet these constraints. The vitamin premix provided the antioxidants B.H.A. and B.H.T., each at a level of 0.0022 percent (11) in both blends. 

The infrared technique has been described in numerous publications and recent reviews were published by Davies and Giangiacomo (2000), Ismail et al. (1997) and Wetzel (1998). Very few applications have been described for analysis of additives in food products. One interesting application is for controlling vitamin concentrations in vitamin premixes used for fortification of food products by attenuated total reflectance (ATR) accessory with Fourier transform infrared (FTIR) (Wojciechowski et al., 1998). Four vitamins were analysed - Bi (thiamin), B2 (riboflavin), B6 (vitamin B6 compounds) and Niacin (nicotinic acid) - in about 10 minutes. The partial least squares technique was used for calibration of the equipment. The precision of measurements was in the range 4-8%, similar to those obtained for the four vitamins by the reference HPLC method. 

Amprolium (Fig. 5.7) is a vitamin IT analogue. It is a competitive antagonist of the thiamine transport mechanism. Amprolium has been used as a coccidi-ostat mainly in chickens, laying hens, turkeys, and ruminants. It is available as a soluble powder for addition to drinking water (60-240 mg/L) or as a premix, usually in combination with ethopabate and/or sulfaquinoxaline, for mixing with the feed (125-500 mg/kg feed). A withdrawal period of 3 days is required for chickens. 

Mix the vitamin premix with Aerosil 200, add the other components, pass through a 0.8 mm sieve, mix and press with low compression force. 

The lipid fraction of foods containing the fat-soluble vitamins is composed mainly of triglycerides, with much smaller amounts of sterols, carotenoids, phospholipids, and minor li-poidal constituents. All of these substances exhibit solubility properties similar to those of the fat-soluble vitamins, and therefore they constitute a potential source of interference. A proportion of the indigenous fat-soluble vitamin content of a food is bound up with a lipoprotein complex, and hence the fat-protein bonds must be broken in order to release the vitamin. The protective gelatin coating used in certain proprietary vitamin premixes will need to be dissolved before commencing the analysis of supplemented foods. 

S Kmostak, DA Kurtz. Rapid determination of supplemental vitamin E acetate in feed premixes by capillary gas chromatography. J Assoc Off Anal Chem Int 76 735-741, 1993. 

Gross necropsy lesions of a selenium deficiency are identical to those of a vitamin E deficiency (NRC, 1994) and include exudative diathesis and myopathy of the gizzard. Paleness and dystrophy of the skeletal muscles (white muscle disease) are also common. The incidence and degree of selenium deficiency may be increased by environmental stress. Selenium is generally included in trace mineral premixes. Common sources for supplementation of poultry diets are sodium selenite and sodium selenate. Selenium yeast is also used in conventional diets. 

Vitamin/drug premix Calculated analysis (g/kg unless stated) 10.5 10.5 10.5... 

Table 5.15. Composition of a vitamin premix to provide the NRC (1994) estimated vitamin requirements in chicken grower and layer diets when included at 5 kg/t. ...

Each shipment of supplement and premix should be sampled and the samples stored in a freezer. If problems are found with the premix, a sample is then made available for analysis. Selected nutrients such as biotin or vitamin E can be chosen as monitors of correct composition. 

Coehlo, M.B. (1994) Vitamin stability in premixes and feeds a practical approach. BASF Technical Symposium, Indianapolis, Indiana, 25 May, pp. 99-126. 

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