The concentration of histamine in fish meal

Table 2: Evolution of the moisture during the fish meal production process. Stages of production: Lot 1 (TVB = 30mg / 100g) Lot 2 (TVB = 120mg / 100g). Reception 75.3% – 71%; Cooking 62.6% – 58.6%; Press Cake 55% – 45%; Decantation sludge 45% – 41%; Stickwater concentrate 37% – 37.3%; Dried product without stickwater concentrate 9.3% – 11.1%; Dried product with stickwater concentrate 10.5% – 11.3%; Finished without stickwater concentrated 9.6% – 11%; Finished product with stickwater concentrated 11% – 11%. The results represent the arithmetic mean of 3 samples taken at 15 min intervals for each stage of production. Cooking losed to the raw material a portion of water in the order of 13%. At the press cake, the moisture contents for the two batches are on average 60%.

This objective is generally sought by all of the fish meal manufacturing units. The finished product, prepared with or without stickwater concentrate, was characterized by a moisture content of 11% which corresponds to a water activity value less than 0.6 (aw <0.6). The latter gived the finished product a certain microbiological stability with the exception of molds which are capable of multiplying at these water content values. The remarkable fact is the water content of stickwater concentrate which was on average 37%. Its incorporation into the press cake before drying is entirely justified in terms of the solid material yield of the finished product.

Thus, at the end of this study, certain solutions can be recommended for controlling the concentration of histamine in the finished product, namely: Stopping the recovery of stickwater when using a degraded or spoiled raw material; The distribution of the stickwater concentrate (product resulting from the evaporation of stickwater) over several dryers to reduce the level of histamine in the finished product. It should be noted that the distribution of the concentrate on the dryers must be done with a reasonable flow rate so as not to reduce the efficiency of the dryers and consequently increase the moisture in the finished product.

Conclusion: The quality of the raw material used to make fish meal, expressed through the levels of TVB-N and histamine, clearly determines the histamine levels in the finished product. When this quality is deemed acceptable (TVB-N level 30 mg / 100 g corresponding to a histamine content of24.1 ppm), the histamine contents in the finished product are from 110.6 to 185.6 ppm, and remain sufficiently

distant from the safety acceptability limit which is 500 ppm. Under these conditions, the incorporation of stickwater concentrate, the histamine contribution of which has been clearly demonstrated above, does not present any risk of exceeding this limit.

The histamine content of the final product of fish meal from the by-products of Sardina pilchardus remains proportional to the initial concentration in the raw material and the product obtained following the evaporation of the stickwater was the product with the highest level of histamine compared to products from other stages of production. To this end, its reintegration into the production chain must be done by assessing the risk of obtaining lots of fish meal with a high level of histamine, especially since the concentrations of histamine in the finished product can exceed the required safety limits when using an spoiled raw material.In the case of using an altered raw material for the production of fishmeal, the water-solubility property of histamine has made it possible to obtain the least concentration in the decantation sludge, therefore, it is strongly recommended to exploit this property to decrease the level of histamine in the finished product.

Regulation (EC) 2074/2005 enacts a limit of TVB-N of 60mg / 100g for fish used in the preparation of fish oil intended for human consumption while regulation 853/2004 provides, by derogation, that the requirements relating to histamine is not applicable to fish meal for animal consumption, while levels TVB-N of 40 mg / 100g are considered by some fish meal producers to be optimal limits for obtaining fish meal of good quality (Lückstädt and Kühlmann, 2010). To this end, it will be interesting to determine critical limits for TVB-N in the raw materials used for the purpose of producing fish meal intended for animal consumption for better sanitary and sustainable use of this product.