Preparation of Portable Counting Card of Staphylococcus aureus
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Abstract:
In this paper, in order to develop a new type of portable counting card for the detection of Staphylococcus aureus in foods, optimization of medium composition of S. aureus count card by orthogonal experiment, the compounding ratio of the cold water soluble gel and the effect of the optimized surfactant on the texture properties of the composite gel were studied. The results showed that the medium components of S. aureus count card were tryptone 10 g/L, beef extract 5 g/L, yeast extract 1 g/L, glycine 12 g/L, lithium chloride 5 g/L, urea 0.2 g/L, potassium tellurite 10 mg/L, yolk powder 6 g/L, the optimal concentration of surfactants were D-mannitol 4 g/L, sodium pyruvate 5 g/L, the proportion of cold water soluble gel was guar gum: sodium polyacrylate=7:3. The optimal gel texture was obtained by adding the optimized cold water soluble gel of D-mannitol and pyruvate. The hardness and viscosity of the composite gel were 1362.04 g and 630.41 g respectively. Compared with the national standard plate counting method, the test results of this study have a good correlation (R2=0.995), which can reach the same level of detection limit of 2 CFU/mL and sensitivity (100%). The S. aureus count card studied in this paper can be applied to the quantitative detection of S. aureus in foods.
