FOOD 569 



not so readily separate out. It should always be tried when cow's 

 milk is not available. It is not sufficiently appreciated in some parts 

 of the tropics. 



Yitamines. 



Vitamines are essential food substances without which some 

 deficiency disease soon sets in. They are contained in rice polishings 

 and veast, hence the former should not be rejected. They prevent 

 polyneuritis. Vitamines (CO (NH)^ CieHigOg ?) belong to the 

 Pyramidine group, and may be a constituent of nucleic acid. They 

 are nitrogenous bodies which do not contain phosphorus or fat. They 

 are soluble in alcohol and water. They are crystallizable and not 

 destroyed by boiling water. They are unimpaired when milk is 

 sterilized or pasteurized. They are found in all food-stuffs in a minute 

 quantity, but they are more plentiful in commercial lecithin, milk, ox 

 brain and brewer's yeast. They are probably the mother substances 

 of ferm.ents and hormones. They are destroyed at i20°-i30° C. in 

 twenty rninutes, and also by extreme dryness. 



ADULTERATION OF FOODS. 



Adulterants in milk are common in the tropics, such as : — 

 (i) Sewage from w^ells, tanks and ponds. 



(2) ]\Iolasses or potassa to raise the specific gravity after adding 

 water. 



(3) Arrowroot and pulped banana. Cream is usually removed from 

 milk samples where these adulterants are used. 



(4) Preservatives are not so commonly used. 

 Test for nitrites in milk. 



Coagulate a little milk in a test-tube with acetic acid. 



Filter, add to the filtrate a few c.c. of sulphanilic acid and naphthyl- 

 amine sulphate, equal parts; a rose-red colour is positive for nitrites. 



Test for nwlasses and botassa. 



To one test-tube containing 10 c.c. of milk add 5 grm. of ammonium 

 molybdate and 10 c.c. of dilute alcohol (i in 10). 



To a second test-tube place 6 per cent, solution of lactose and treat 

 as above. 



Place both test-tubes in a water bath and raise the temperature 

 gradually to 80° C. 



A blue coloration in the tube is positive for cane sugar, while 

 lactose is unaltered. 



This test will detect o'l per cent, of cane sugar. 



Another test. 



To 10 c.c. of milk add o"i grm. of resorcin and a few drops of HCl 

 Boil for a few minutes. 



