Degree Type

Dissertation

Date of Award

1987

Degree Name

Doctor of Philosophy

Department

Food Technology

Abstract

Thermal inactivation characteristics of Newcastle disease virus (NDV) were defined in turkey breast spiked to 10[superscript]8 virus per gram. Five strains, including mesogenic, velogenic and exotic NDV, were compared for loss of infectivity at 56° C. Roakin and Fontana strains were more stable than Texas GB, San Juan or Parrot Project viruses. The thermal death time curve for Roakin strain NDV was defined over the temperature range 56 to 68.8° C. Based on time required to inactivate virus at various temperatures, the values F[subscript]68.8° C = 5.0 min and z = 8.9° C were calculated;Thirty adult market turkeys were inoculated with the Fontana strain of exotic NDV. Pre-inoculation hemagglutination inhibition antibody titers did not exceed 1:16. The combined intraocular (IO), intravenous (IV) and intra-muscular routes of inoculation were more effective than IO or IO plus IV. Virus was demonstrated in 12 of the 30 turkey breasts. Viremic turkey breast tissue was thermally processed under laboratory conditions which duplicated the heat exposure of the center of whole breasts heated by a proposed commercial process. No virus was recovered from any of the thermally processed viremic turkey breasts;Acid phosphatase (ACP) activity of turkey breast was determined for temperature/time treatments which inactivated NDV. At 56° C/140 min and 60° C/49 min, the ACP activity was more stable to heating than was the ACP activity at 64° C/17.2 min and 68.8° C/5.0 min. The ACP was more extensively inactivated by proposed commercial processing conditions than it was by any of the temperature/time treatments which inactivated NDV. Therefore, laboratory analysis which demonstrates that ACP activity of thermally processed turkey breast falls below a threshold level indicates that NDV has been destroyed. The threshold ACP activity level can be adjusted to change the safety margin. In this model system, adequate processing can be demonstrated regardless of the specific thermal process used;The ACP test method, based on 2,6 dibromoquinone chloride colorimetry, was shown to be subject to both false positive and false negative reactions with some phenolics present in spices and flavorings.

DOI

https://doi.org/10.31274/rtd-180813-13122

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Robert Marshall Davis

Language

en

Proquest ID

AAI8721878

File Format

application/pdf

File Size

122 pages

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