Determination of Calcium in Meat Products by Automatic Titration with 1,2-Diaminocyclohexane-N,N,N',N'-tetraacetic Acid

Abstract

Mechanically separated meat (MSM) is a by-product of the poultry industry that requires routine quality assessment. Calcium content is an indirect indicator of bone debris in MSM but is difficult to determine by EDTA titration due to the poor solubility of calcium phosphate. Therefore, 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid was used instead, which has two orders of magnitude higher affinity for calcium ions. In addition, the auxiliary complexing agents triethanolamine and Arsenazo III, an indicator that is sensitive to low calcium concentrations, were used. Automatic titration endpoint detection was performed using an immersion probe at 660 nm. It has been shown that the color change in Arsenazo III can also be read with an RGB camera. The CDTA titration procedure has been tested on commercial Bologna-type sausages and the results were in line with AAS and ICP reference data. The content of calcium in sausages turned out to be very diverse and weakly correlated with the content of MSM. The tested MSM samples had a wide range of calcium content: from 62 to 2833 ppm. Calcium-rich poultry by-products include fat and skin (115 to 412 ppm), articular cartilage (1069 to 1704 ppm), and tendons (532 to 34,539 ppm). The CDTA titration procedure is fully suitable for small meat processing plants due to its simplicity of use and low cost.

Keywords: calcium; cartilage; mechanically deboned meat; mechanically separated meat; skin; tendon.

Figure 1

Structural formulae of (a) CDTA, (b) TEA, and (c) Arsenazo III.

Figure 2

(a) Spectral changes of Arsenazo III in the presence of calcium ions. The operating wavelengths of the Optrode LEDs are indicated by the correspondingly colored bands. (b) Optrode signals at different wavelengths during CDTA titration of Ca model solutions. Arsenazo concentration is 2 μM. (c) Optrode signal at 660 nm vs. CDTA volume at different concentrations of Arsenazo III. (d) First derivatives of graphs (c).

Figure 3

(a) Titration graphs obtained during the analysis of 1 g and 2 g samples of brand A chicken sausage. (b) The influence of TEA on the shape of the titration graph when analyzing 1 g of brand I turkey sausage. Smooth lines are the first derivative graphs of titration curves. (c) Titration graphs obtained with model solutions containing Ca and Mg ions and 10% TEA at a pH of 12.

Figure 4

Correlation between complexometric titration and AAS measurements for (a) Bologna-type sausages and (b) MSM samples. The samples are (●) chicken, (■) turkey, and (▲) pork meat products.

Figure 5

(a) Distribution of calcium content values in the sausage samples. The boxes indicate the upper and lower quartiles; the whiskers indicate the minimum and maximum values; and the × sign indicates the mean value. (b) Calcium content as a function of MSM content in the sausage samples. Meat producers are color coded. Ingredients other than MSM are listed in the legend.

Figure 6

Calcium content in chicken and turkey parts: (a) meat; (b) fat and skin; (c) articular cartilage; and (d) tendon. The boxes indicate the upper and lower quartiles; the whiskers indicate the minimum and maximum values; and the × sign indicates the mean value.

Figure 7

Changes in (a) red, (b) green, and (c) blue color components in the images of the reaction beaker were recorded during the complexometric determination of calcium in 1 g of a sample of brand I turkey sausage. The indicator was Arsenazo III at a concentration of 2 μM.