Emmental-type cheese

The acidity of food is related to the amount of undissociated and dissociated forms of carboxyKc acids and oxonium ions, respectively, that are present. The major substances that give a sour taste in foods are undissociated hydroxycarboxylic acids, citric and malic acids. Often, however, other carboxylic acids occur, such as ascorbic acid in most types of fruits, tartaric acid in grapes, isocitric acid in blackberries, oxalic acid in rhubarb, lactic acid in some dairy products (such as yoghurt), fermented cucumbers, cabbage, oKves, vinegar and propionic acid in Emmental type cheeses (see Section 8.2.6). The acidity of cola drinks is provided by phosphoric acid, sometimes accompanied by citric or other acids. Carboxylic acids also act as bacteriostatic agents and affect a number of biochemical and chemical reactions. 

The use of propionic acid and its salts are allowed for pre-packed sliced bread and rye bread (3000 mg/kg), and for energy reduced bread, partially baked, pre-packed bread and pre-packed fine bakery wares (including flour confectionery) with a water activity of more than 0.65 (2000 mg/kg). Fermented milk products (Emmental type cheeses) contain natural propionic acid arising in the fermentation process, which is not regarded as a food additive. 

Fermentation of lactic acid to yield propionic acid, carbon dioxide, acetic acid, and succinic acid is important for proper eye formation and flavor development in Emmental, Gruyere, and Swiss-type cheese varieties. This fermentation is associated with Propionibacterium spp. subspecies of Propionibacterium freudenreichii are of greatest significance. These organisms can also be used for industrial production of vitamin Bi2 and propionic acid. 

The metabolism of lactose and lactate in Swiss-type cheeses was described comprehensively by Turner et al. (1983). Typically, Emmental cheese contains 1.7% lactose 30 min after moulding, which is rapidly metabolized by 5. thermophilus with the production of L-lactate. Only the glucose moiety of lactose is metabolized by S. thermophilus and consequently galactose accumulates to a maximum of —0.7% at —10 hr, when the lactobacilli begin to multiply. These metabolize galactose to a mixture of d- and L-lactate, which reach —0.35 and 1.2%, respectively, at 14 days, when the galactose is metabolized completely. 

Important components of hard cheeses (Gouda type) include some carboxylic acid esters (ethyl butanoate, ethyl hexanoate), as well as carboxylic acids (acetic, butyric, isobutyric, valeric, isovaleric, 2-methylbutyric and caproic acids). Cheeses manufactured using bacteria of the genus Propionibacterium (such as Emmental and Gruyere) contain propionic acid and other lower fatty acids, methyl thioacetate, some oxocarboxylic acids, various alcohols, esters (such as ethyl butanoate), lactones (such as 8-decalactone), amines and other basic compounds (also skatole in addition to aliphatic amines), alkylpyrazines (e.g. 2-sec-butyl-3-methoxypyrazine), 4-hydroxy-2,5-dimethyl-2H-furan-3-one (furaneol), 2-ethyl-4-hydroxy-5-methyl-2H-furan-3-one (homofuraneol) and a range of other compounds. 

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