EGG PROCESSING SAFETY, QUALITY AND SECURITY
Location: Egg Safety and Quality
Title: IDENTIFICATION OF YEASTS ISOLATED FROM COMMERCIAL SHELL EGGS STORED AT REFRIGERATED TEMPERATURES
Submitted to: International Association for Food Protection Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 8, 2006
Publication Date: August 14, 2006
Citation: Musgrove, M.T., Jones, D.R., Hinton Jr, A., Ingram, K.D., Northcutt, J.K. 2006. Identification of yeasts isolated from commercial shell eggs stored at refrigerated temperatures [abstract]. International Association for Food Protection Proceedings. p. 126.
Yeasts and molds, which are able to withstand harsh environmental stresses, can grow on or in eggs and cause spoilage. Egg meats readily absorb off odors, including those caused by yeast or mold growth, so their presence on eggs may constitute a quality concern. Washed and unwashed eggs (treatments) were collected aseptically on three separate days (replications) from a commercial processing facility and stored for ten weeks at 4oC. Enough eggs were collected so that 10 eggs from each treatment could be sampled weekly (120 eggs/treatment/replication). Yeast and mold populations were enumerated from external rinses of the shells by plating onto acidified potato dextrose agar. Prevalence and level data were described in a previous report. Yeast colonies were picked randomly and stored for subsequent identification by gas chromatographic analysis of fatty acid content using the MIDI Microbial Identification System. Of the 688 isolates analyzed, 457 were identified to genus or species. Genera identified by this method included Candida, Cryptococcus, Hanensula, Hyphopichia, Metschnikowia, Rhodotorula, Sporobolomyces, and Torulaspora. Almost 80% of the isolates were identified as Candida spp. (390/457). Candida famata was the most commonly identified species (n = 165), followed by Candida zeylanoides (n = 20). Subsequently, a group of 20 isolates were subjected to molecular and biochemical analyses for comparison with the MIDI results. While biochemical tests and sequencing of rRNA were in agreement for 10 of the isolates, only 2 of the 20 MIDI identified isolates were in agreement with the sequenced samples when Genebank data were used. Candida famata, a synonym of Debaromyces hansenii var. hansenii was the most commonly identified isolate by biochemical and molecular methods. These data indicate that there is little correlation between MIDI system and the corresponding library is of limited use in properly identifying yeasts isolated from commercial shell eggs.