96 PUBLIC HEALTH CHEMISTRY 



formation of lime salts of the fatty acids, and a soluble 

 compound of phosphoric acid with the casein. Average 

 composition of Cheddar cheese per cent : water 33-9, 

 ash 4-2, fat 30, nitrogen 4-3, casein 27-3. Water is very 

 high in cream cheeses, which are also very deficient in fat, 

 in nitrogen, and in casein. The Reichert figure for the fat 

 of cheese is, from its similar origin, the same as that for 

 butter fat. There is no standard for cheese in this country, 

 and a cream cheese can be purchased containing less fat 

 than a milk one, unless double cream be asked for. A good 

 standard would be not less than 30 per cent of true butter 

 fat and no starch or other extraneous matter : for cream 

 cheese, a 40 per cent standard. U.S.A. standard : 50 per 

 cent milk fat in dried solids. 



Analysis. Moisture : dry 2 to 5 grm. of sample cut 

 in thin slices, to constant weight in water-oven at 105 C. 

 (absolute alcohol hurries drying). 



Ash. Ignite dried cheese at as low a temperature as 

 possible. 



Nitrogen. Treat I grm. of sample by the Kjeldahl 

 process. N x 6-38 = proteins. 



Fat. Take dried cheese, put into filter-paper thimble, 

 and extract in Soxhlet for two hours ; or grind 50 grm. 

 of sample in a mortar with sand, put mixture in tall 

 stoppered cylinder and extract with four portions of ether, 

 using in all about 500 c.c. Make to a definite volume, 

 take aliquot part, evaporate to dryness, and weigh residue. 

 Or by Leffman-Beam. 



Reichert-W ollny Process. Extract fat by melting in 

 water-oven. 



Poisonous Metals in Rind. Lead, copper, and arsenic 

 have been found in rind. 



Salt 5 to 6 per cent ; tyro-toxicon, acarus domesticus, 

 moulds. 



CEREALS I WHEAT-FLOUR I BREAD. 



The cereals consist of the edible grains, such as wheat, 

 oats, barley, rye, maize, rice, millet, and buckwheat. 

 From these, various products are got which are largely 

 used for food ; as wheat flour, oatmeal, barley meal, pearl 

 barley, rye flour, corn flour (from maize or Indian corn), 



