Chocolate agar refers to the strong, firm, gel created from the combination of traditional agar and red blood cells. The mixture is heated until the substance becomes chocolate brown in color. Chocolate agar is primarily used in laboratories as a culture medium for specific microorganisms.
Agar is a red seaweed extract used as a culture medium for bacteria. It is also used as a stabilizer in puddings, pie fillings, cheese, ice creams, soups and sauces. At room temperature, agar is a gel. When combined with red blood cells, agar becomes blood agar. Once heated, the blood agar becomes brown and chocolate colored, creating chocolate agar that can be used to culture specific species of microorganisms.
Hardy Diagnostics reports that chocolate agar is made up of proteose peptone, sodium chloride, dipotassium phosphate, monopotassium phosphate, corn starch, bovine hemoglobin, KoEnzyme enrichment and agar. The KoEnzyme enrichment contains various vitamins, amino acids and sugars including dextrose, L-Cysteine, L-Glutamine, L-Cystine, vitamin B12 and thiamine.
In the article, "Chocolate Agar, a Differential Medium for Gram-Positive Cocci," Bruce Gunn states that chocolate agar is an enriched culture medium used to aid in the growth of specific microorganisms such as Haemophilus influenzae. When supplemented with antibiotics, chocolate agar can also be used to culture the Neisseria species of microorganisms. While chocolate agar is primarily used in the laboratory setting, traditional agar can be used as a stabilizer in puddings, meringues, pie fillings, cheese, icings and sherbets.
In the kitchen
While chocolate agar is primarily used in laboratories, there are some countries such as Asia and Australia, that use agar powder in recipes. When combined with sugar, water, cocoa powder and evaporated milk, agar helps to create a jelled, pudding-like dessert. The recipe is called chocolate agar, or chocolate agar agar. The agar is used in place of traditional gelatin to help create a stronger and firmer gel.