Spoilage of vacuum-packed beef by the yeast Kazachstania psychrophila

•The yeast microbiota of vacuum-packed beef is more diverse than currently known.•Till present, the occurrence of Candida argentea and Mrakia frigida on meat was not reported.•Kazachstania psychrophila was used the first time in challenge trials.•This yeast can multiply to more than 6 log cfu per cm2 at 4 °C within 2 weeks.•K. psychrophila had a high spoilage potential in the vacuum-packaged beef.

A survey of the psychrotolerant yeast microbiota of vacuum-packed beef was conducted between 2010 and 2012. Chilled vacuum-packed beef (n = 50) sampled from 15 different producers was found to have a mean psychrotolerant yeast count of 3.76 log cfu per cm2. During this assessment, a recently described yeast named Kazachstania psychrophila was shown to be associated with this product. In order to gain basic knowledge about the spoilage potential of K. psychrophila in vacuum-packed beef, challenge studies were performed and the survival of three different K. psychrophila strains was analyzed during storage of artificially contaminated beef. Beef samples were inoculated with the yeasts at a contamination level of 2 log cfu per cm2. Survival and growth of K. psychrophila strains was monitored on malt extract agar at regular intervals over 84 days. Kazachstania levels rapidly increased about 5 log units within 16 days under chill conditions (4 °C). Gas bubbles were observed after 16 days, while discoloration and production of off-flavors became evident after 42 days in inoculated samples. This study demonstrates for the first time, that the psychrotolerant yeast K. psychrophila is a dominant spoilage microorganism of vacuum-packed beef products stored at low temperatures, causing sensory defects which result in reduced shelf life, and consequently in considerable economic losses.