In the dairy industry products with a low or no fat content are experiencing increasing demand from consumers.
However, such low fat dairy products often experience a lack of creamy flavor.
Diacetyl is a high value product and it is used in the dairy industry as a buttery flavor-producing compound added to such products as margarines and oil-based products.
Heterolactic acid bacteria form diacetyl/acetoin as a by-product along with lactate as the main product. The cells form active acetaldehyde from pyruvate and thiamine pyrophosphate by pyruvate oxidase. The active acetaldehyde condenses with another molecule of pyruvate and forms alpha-acetolactate synthase. Formation of diacetyl in Lactobacillus rhamnosus is not well understood—in Lactococcus lactis subsp. lactis biovar. diacetylactis it has been suggested that alpha-acetolactate is oxidized to diacetyl by an alpha acetolactate oxidase (Jyoti et al 2003). Acetoin is formed directly by decarboxylation of alpha-acetolactate. Acetoin formation may also occur by the irreversible diacetyl reductase of diacetyl into acetoin.
Lactobacillus rhamnosus is a heterolactic acid bacterium which can be used to produce flavor compounds like diacetyl and acetoin (Jyoti et al. 2003). The level of diacetyl produced depends on the strain as well as the substrate on which it is grown.
U.S. Pat. Nos. 4,867,992 and 5,236,833 relate to processes for production of diacetyl by fermenting a coffee substrate and a pectin substrate, respectively, with a lactic acid producing bacteria.
The preparation, concentration and addition of diacetyl and/or acetoin to food products are connected with substantial costs.
U.S. Pat. No. 4,678,673 is directed to oilseed products fermented with a Lactobacillus rhamnosus strain which produces diacetyl and acetoin. The fermented oilseed products have a buttery or dairy-like flavor. There is no mention of use of Lactobacillus rhamnosus in dairy products.
Thus, there exists a need for a process of preparing dairy products with improved creamy flavor without the costly addition of diacetyl and/or acetoin.