Evaluation of Bacteriological Stability of Minced Canned Meat Stored Under Simulated Tropical and Subtropical Conditions

Abstract

Thermal inactivation of spoilage microorganisms is one of the widely used commercial food preservation techniques. However, its application may be too costly in terms of energy expenditure or inappropriate in terms of product quality. In this study, an attempt was made to produce tropical storage stable canned meat using remarkably milder heating effects than those commonly used by food processors. Canned beef in its own juice was used as a model product and Bacillus stearothermophilus (Merck Art No. 11499), Clostridium sporogenes (ATCC 10000) and Clostridium thermosaccharolyticum (ATCC 7956) as reference strains. The raw minced meat used for the formulation of the product was contaminated with spores of the aforesaid strains at 10⁴-10⁶ spores/g prior to the heat treatment. The heating effects (F_c – values) were measured throughout the experiment at the geometrical middle point (GMP) of the can. The canned meat was thereafter stored up to six months under simulated tropical and subtropical temperatures of 55^oC and 25^oC respectively, followed by bacteriological investigations. Results showed that C. sporogenes is of no significance in the production of tropical storage stable canned meat products. This strain was eliminated by F_c = 3.0 even at a very high contamination level of 10⁶ spores/g. At the same level of contamination, heating values of F_c = 13.0 and 16.0 were needed to eliminate spores of C. thermosaccharolyticum and B. stearothermophilus, respectively. At a reduced contamination level of 10⁴ spores/g F_c values of 11.0 and 15.0 were necessary to completely eliminate the same bacteria, respectively. Addition of 0.4 % benzoic acid resulted into reduction of the F_c – value from 16.0 to 13.0 for the elimination of B. stearothermophilus at 10⁶ spores/g contamination level. Adding the same amount of citric or acetic acid was enough to lower the heating value further to 11.0. Potassium sorbate was ineffective in increasing the heat sensitivity of B. stearothermophilus even at a concentration of 4 % in the minced meat. It was concluded that the heating effects (F_c – values) recommended for the production of tropical stable and safe meat products are applicable only for highly contaminated raw meat. F_c – values of 16 and above given by some authors seem to be on the higher side. Observing hygienic practices in handling of the raw meat could significantly (P<0.05) contribute to the lowering of heating values.

Addition of small amounts of benzoic, citric and acetic acids (GRAS-substances) to the product can indeed reduce the heating values remarkably, however their application is limited due unacceptable flavor imparted to the product at levels exceeding 0.5 %.

Journal of Agriculture, Science and Technology Vol.3(2) 2001: 31-44