Spoilage of vacuum-packed beef by the yeast Kazachstania psychrophila.

Food microbiology (2015-12-19)
Jan Kabisch, Constanze Erl-Höning, Mareike Wenning, Christina Böhnlein, Manfred Gareis, Rohtraud Pichner
ABSTRACT

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 cm(2). 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 cm(2). 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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Perchloric acid, ACS reagent, 70%
Sigma-Aldrich
Perchloric acid, 70%, 99.999% trace metals basis
Sigma-Aldrich
Lactic acid solution, ACS reagent, ≥85%
Sigma-Aldrich
Lactic acid, 85%, FCC
Sigma-Aldrich
Lactic acid, meets USP testing specifications
Sigma-Aldrich
Perchloric acid, ACS reagent, 60%
Sigma-Aldrich
Lactic acid, natural, ≥85%
Sigma-Aldrich
Perchloric acid, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., 70.0-72.0%
Sigma-Aldrich
DL-Lactic acid, 85 % (w/w), syrup
Sigma-Aldrich
Perchloric acid, puriss. p.a., ACS reagent, packed in coated, shock- and leak-protected glass bottle, ≥60% (T)
Sigma-Aldrich
DL-p-Chloroamphetamine hydrochloride, ≥94% (HPLC)