Propionic acid fermentation of ultra-high-temperature sterilized whey using mono-and mixed-cultures

Summary Unlike sterilization by autoclave (Anderson et al. 1986) high concentrations of cheese whey sterilized by ultra high temperature (UHT) resulted in a medium conducive to microbial growth and propionic acid production. Propionibacterium freudenreichii ss. shermanii, grown with pH control in 12% whey solids and 1% yeast extract sterilized by UHT, produced about 1.9% propionic acid within 70 h; more than 50% of the lactose was not used. Under similar conditions, mixed cultures of P. shermanii and Lactobacillus casei produced more than 3.0% propionic acid. Acclimating the mixed culture to the whey medium resulted in 4.5% propionic acid. The amount of propionic acid produced was further increased to about 6.5% by raising the concentration of whey solids to about 18%. Using the mixed culture, all the lactose was consumed and lactic acid did not accumulate.