0| Raw Material | Characteristics | Nutritional Value |
| Beef Extract | An aqueous extract of lean beef tissue concentrated to a paste | Contains the water-soluble substances of animal tissue, which include carbohydrates, organic nitrogen compounds, water-soluble vitamins, and salts. |
| Peptone | The product resulting from the digestion of proteinaceous materials, e.g., meat, casein, and gelati; digestion of the protein matetrial is accomplished with acids or enzymes; many different peptones (depending upon the protein used and the mmethod of digestion) are available for use in bacteriological media; peptones differ in their ability to support growth of bacteria. | Principal source of organic nitrogen; may also contain some vitamins and sometimes carbohydrates, depending upon the kind of proteinaceous material digested. |
| Agar | A complex carbohydrate obtained from certain marine algae; processed to remove extraneous substances | Used as a solidification agent for media, agar, dissolved in aqueous solutions, gels when the temperature is reduced below 45 degrees; agar not considered a source of nutrient to the bacteria. |
| Yeast Extract | An aqueous extract of yeast cells, commerially available as a powder | A very rich source of the B vitamins; also contains organic nitrogen and carbon compounds. |
