Effects of processing methods on the content of minerals in fish products

Effects of salting, pickling and smoking processing methods on the mineral composition in fish products were investigated. The concentrations of Ca, P, Mg, K, Na, Cu, Fe, Zn, Mn and Se in fish products were determined during subsequent stages of processing in raw fish, semi-processed products and ready products. Fresh fish contained macro-elements in the following order: K > P > Na > Ca > Mg. The tendency was similar in semi-processed and ready products, except for the dominance of sodium. The sodium content in marinated products was three-fold higher than in fresh fish and twelve-fold higher in salted herring and cold-smoked fish. The sodium content in a 100 g portion of salted herring exceeded by six-fold the recommended daily allowance and by two-fold the tolerated amount. The content of K, Mg and P in marinated and salted herring tended to decrease throughout processing. No significant differences were observed in concentrations of Ca. The order of the concentrations of microelements was as follows: Zn > Fe > Cu > Se > Mn. The content of these elements in fish products was similar to their levels in fresh fish and corresponded to the following shares of the recommended allowances: Se up to 20%; Cu up to 11%; Zn up to 6%; Mn up to 1%; Fe up to 10%. Disadvantageous changes in the mineral composition in fish during processing result from water losses during technological processes, but the primary cause of mineral loss was leaching when the products were soaked in brine solutions with a high sodium content. Significant changes in the content of minerals in salted and pickled herring decreased the nutritional value of these products. Smaller mineral losses that occurred during smoking meant that these products were more valuable nutritionally in relation to minerals.