A gelatin liquefaction test for the screening of compounds used or proposed as inhibitors of bacterial proteolytic deterioration in foods
article
1. A gelatin liquefaction test, useful in screening of inhibitors of bacterial proteolytic spoilage in foods, is described.
In this test gelatin slants are used as a substratum and aPseudomonas strain, isolated from the slime formed on fish, stored at 5°C., is used as an inoculum. The preparation of the medium and the density of the inoculum are standardized.
The coefficients of variation of the absolute liquefaction data obtained by four technicians, when using the same batch of gelatin and inoculum, roughly vary from 1–5. The spread in the relative liquefaction data (LR), obtained for various preservatives, amounts to 10% absolute and is not significantly influenced by the use of different batches of gelation or by differences in intensity of gelatin liquefaction in the strain.
2. Under the circumstances of the test, reduction in LR-values of the order of 50% was obtained with: 0.05% sodium nitrite at pH_o=5.5,1% sodium, chloride, 0.1% propionic acid at pH_o=5.5, 0.1% boric acid, 0.2% benzoic acid at pH_o=5.5, 0.2% hexamine at pH_o=5.5, 0.05% sodium methylparahydroxybenzoate, 0.01% zephiran, 0.1% cetyltrimethylammoniumbromide and 1.0% sodium dehydroacetate, and ethyl monobromoacetate in a concentration corresponding to 25 mg Br/kg.
In this test gelatin slants are used as a substratum and aPseudomonas strain, isolated from the slime formed on fish, stored at 5°C., is used as an inoculum. The preparation of the medium and the density of the inoculum are standardized.
The coefficients of variation of the absolute liquefaction data obtained by four technicians, when using the same batch of gelatin and inoculum, roughly vary from 1–5. The spread in the relative liquefaction data (LR), obtained for various preservatives, amounts to 10% absolute and is not significantly influenced by the use of different batches of gelation or by differences in intensity of gelatin liquefaction in the strain.
2. Under the circumstances of the test, reduction in LR-values of the order of 50% was obtained with: 0.05% sodium nitrite at pH_o=5.5,1% sodium, chloride, 0.1% propionic acid at pH_o=5.5, 0.1% boric acid, 0.2% benzoic acid at pH_o=5.5, 0.2% hexamine at pH_o=5.5, 0.05% sodium methylparahydroxybenzoate, 0.01% zephiran, 0.1% cetyltrimethylammoniumbromide and 1.0% sodium dehydroacetate, and ethyl monobromoacetate in a concentration corresponding to 25 mg Br/kg.
TNO Identifier
49649
Source
Antonie van Leeuwenhoek, 20(1), pp. 233-240.
Pages
233-240
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