Changes in Bacterial Cell and Spore Counts of Reduced-Fat Egg Products As Influenced by Pasteurization and Spray Drying

Abstract

Microbial counts of several laboratory-prepared defatted egg products and ingredients were determined. Commercial full-fat egg yolks (EY) were defatted with hexane, air dried overnight, mixed with water, homogenized, pasteurized (60°C, 5 min), and spray dried to yield a defatted egg yolk product (DEY). Egg products for scrambling (EPS) were formulated with DEY and other ingredients, processed as above, and held wet (EPS-W) or spray-dried (EPS-SD). On a dry matter basis, the log counts in colony forming units per g (log CFU/g) of EY for aerobic bacteria, yeasts and molds, and aerobic mesophilic sporeformers were low at 1.3, 1.0 and 0, respectively. For DEY these counts were 6.0, 2.4, and 4.3, respectively. These counts for DEY after pasteurization decreased by 98.6, 89.6, and 40.0%, and after spray drying decreased by 99.3, 96.1, and 83.5%, respectively, compared to the pre-pasteurization counts. For EPS-W, pasteurization reduced aerobic bacteria, yeasts and molds, and coliforms by 82.0, 86.7, and 98.7%, but did not reduce aerobic mesophilic sporeformers. Compared to pre pasteurization counts, for EPS-SD the aerobic bacteria, yeasts and molds, coliforms, and aerobic mesophilic sporeformer counts after pasteurization decreased by 99.7, 91.9, 99.3, and 50.0%, while after spray drying the count reductions were 99.9, 98.9, 99.9, and 85.8%, respectively. Microbial counts of finished products were below guidelines set by the U.S.D.A. for egg products. No Salmonella were detected in any of the ingredients or prototype products at any stage of processing. The combination treatment of pasteurization followed by spray drying significantly reduced the spore counts of DEY and EPS-SD, compared to pre-pasteurization counts.