Manufacture of Starters: Production of Frozen Concentrated Cheese Starters by Diffusion Culture

Abstract

Diffusion culture allows the production of concentrated cheese starter without centrifugation principally by removing inhibitory lactate from fermentations. Laboratory scale fermentation systems are described which remove lactate via a diffusion membrane. Single and mixed strain cultures were grown to concentrations of 1011/ml in an enzyme digest of skimmed milk supplemented with yeast extract. The present stage system is capable of producing at least half the annual bulk starter requirements of a creamery processing 100,000 gal of milk/day. Concentrated cultures were harvested in hypodermic syringes and as frozen granules. Concentrates were tested for purity and activity and suitable ones used in a commercial cheesemaking trial which produced a high proportion of extra selected grade Cheddar cheese.

Lactic acid bacteria in the dairy industry

“…This may be due to H 2 0 2 formation, which is overcome by addition of catalase, or to metabolites produced by the cultures themselves such as lactate ions and D-leucine which can act as auto-inhibitors (Gilliland, 1977). Osborne (1977) overcame this metabolite effect by a diffusion culture method using autoclavable cellulose acetate membrane of sufficient area to allow adequate diffusion of the rapidly accumulating lactate. He was able to produce concentrated starter cultures of 10" cells/ml.…”

Production of concentratedStreptococcus salivariussubsp.thermophilusby coupling continuous fermentation and ultrafiltration

“…Yields can be increased by the removal of this metabolic end product. Attempts have been made to do this with streptococcal cultures by dialysis fermentations (Bergere & Hermier, 1968;Osborne, 1977). However, these processes have severe limitations imposed by the size of the diffusion unit.…”

Advances in technology of bulk starter production and cheesemaking

“…Both systems described by Stanley (1977) and Osborne (1977) are capable of producing cultures of sufficient concentration to enable them to be used for DVI and a number of experimental vats have been made successfully with cultures from the two plants. Bunney & Stanley (1978) described work carried out with DVI of milk for the manufacture of Stilton Cheese a t Unigate Foods Harby factory.…”