A laboratory determination of the destruction of α-amylase and salmonellae in whole egg by heat pasteurization

The conditions of heating necessary to destroy salmonellae in liquid whole egg have been compared with those necessary to destroy the activity of the α-amylase of whole egg. All conditions of pasteurizing from the mildest at 61·1° C. (142° F.) for 1 min. to the most severe at 65·5° C. (150° F.) for 5 min. eliminated Salm. typhimurium. The heat-resistant strain of Salm. senftenberg N.C.T.C. 9959 (775 W) was not recovered after heating at 64·4° C. (148° F.) for 2½ min. and at the lower temperatures when the heating period was 3 min. or more. The activity of α-amylase was also destroyed by heating at 64·4° C. (148° F.) for 2½ min. but not at lower temperatures.Because the baking properties of egg are not impaired by heating at 64·4° C. (148° F.) for 2½ min. it is proposed that the inactivation of the α-amylase of whole egg can be used as a test for controlling the pasteurization process, and a routine test has been developed which can be completed within 1 hr.

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Thermal Resistance of Aeromonas hydrophila in Liquid Whole Egg†

Journal of Food Protection ◽

10.4315/0362-028x-60.3.231 ◽

1997 ◽

Vol 60 (3) ◽

pp. 231-236 ◽

Cited By ~ 22

Author(s):

JAMES D. SCHUMAN ◽

BRIAN W. SHELDON ◽

PEGGY M. FOEGEDING

Keyword(s):

Thermal Resistance ◽

Aeromonas Hydrophila ◽

Animal Origin ◽

Inactivation Kinetics ◽

Processing Plant ◽

Decimal Reduction Time ◽

Heat Resistant ◽

Liquid Whole Egg ◽

D Values ◽

Whole Egg

Aeromonas hydrophila (AH) is a psychrotrophic spoilage bacterium and potential pathogen which has been isolated from a variety of refrigerated foods of animal origin, including raw milk, red meat, poultry, and commercially broken raw liquid whole egg (LWE). Decimal reduction times (D values) of 4 strains of AH (1 egg isolate, 2 egg processing plant isolates, 1 ATCC type strain) were determined in LWE using an immersed sealed capillary tube (ISCT) procedure. Initial populations (7.0 to 8.3 log CFU/tube in 0.05 ml LWE) were heated at 48, 51, 54, 57, and 60°C, and survivors were plated onto starch ampicillin agar (48 h at 28°C). D values ranged from 3.62 to 9.43 min (at 48°C) to 0.026 to 0.040 min (at 60°C). Both processing plant isolates were more heat resistant than the ATCC strain. Decimal reduction time curves (r2 ≤ 0.98) yielded ZD values of 5.02 to 5.59°C, similar to those for other non-spore-forming bacteria. D values of the most heat resistant AH strain were also determined in LWE at 48, 51, and 54°C using a conventional capped test tube procedure (10 ml/tube). Cells heated in test tubes yielded nonlinear (tailing) survivor curves and larger (P ≤ 0.05) apparent D values at each temperature than those obtained using the ISCT method. This study provides the first thermal resistance data for AH in LWE and the first evidence that straight-line semilogarithmic thermal inactivation kinetics may be demonstrated for Aeromonas using the ISCT procedure.

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