effect of different storage conditions on n-nitrosamine content in ...

322<strong>conditions</strong>. There are several factors which may influence the appearance <strong>of</strong>nitrosamines. Starting materials for nitrosamine formation are nitrate, nitrite andprimary, secondary and tertiary amines and amides, proteins, peptides and amino acidsor precursors <strong>of</strong> these, which are transformed into nitrosamine precursors by microbialaction (26). It seems that all these compounds could be present in analyzed meatproducts.Nitrate and nitrite are used as preservatives in meat products. These curingagents develop and stabilize the colour associated with cured meats, enhance the curedflavour and act as antioxidants. Nitrite is also antimicrobial agent that inhibitsClostridium botulinum growth and toxin production. Among studied meat productsonly “salceson” contains the greatest amount <strong>of</strong> salted compounds, other contain theirlower amounts or non-salted materials. On the other hand, all these products containingredients <strong>of</strong> plant origin (garlic, onion, paprika, semolina, buckwheat groats, andherb). There are many published papers that provide evidence for the presence <strong>of</strong>nitrate in plant foods (6, 11, 16). The other source <strong>of</strong> nitrate and nitrite in theseproducts could be water used during their preparation. Vegetables, grains and meatscan be rinsed and cooked in water. The amount <strong>of</strong> nitrate/nitrite available from watertaken in <strong>different</strong> places differs considerably depending on water source (17).Nitrosamine formation is also dependent on the presence <strong>of</strong> amines, amides,proteins, peptides and amino acids. The biogenic amines in <strong>different</strong> types <strong>of</strong> meats andmeat products were found in a great variability <strong>of</strong> concentrations (1). They areproduced by the action <strong>of</strong> microbial decarboxylases on free amino acids. The mainfactors affecting formation <strong>of</strong> the biogenic amines in foods are presence <strong>of</strong>microorganisms and <strong>storage</strong> <strong>of</strong> foods in <strong>conditions</strong> enabling their growth (23). Silla-Santos (23) reported that the content <strong>of</strong> amines could increase during the <strong>storage</strong>. It wasshown that NDMA could be formed from such amino acid as glycine, NPIP from suchamine as cadaverine or piperidine and NPYR from spermine and spermidine also fromamino acid proline (12, 14, 24, 27). Other sources <strong>of</strong> precursors <strong>of</strong> nitrosamines as wellas performed nitrosamines could be <strong>different</strong> additives occurring in food as spices,vegetables, and herbs (25).Nitrosamines can be formed as the result <strong>of</strong> chemical reaction and alsomicrobial action. The analyzed meat products are made <strong>of</strong> compounds which could becontaminated with some microorganisms (gastric walls, tongue, blood, as well asspices, herbs and cereals), contain low levels <strong>of</strong> added preservatives (nitrate or nitrite)and are processed in rather low temperatures (brewing at 80-85 0 C during 50-130 min,and sometimes smoking at 30 0 C during 30-40 min). All these cause that their shelf-lifeis rather short. They could contain some microbial load just on the purchase day. The<strong>storage</strong> <strong>conditions</strong> applied in our experiment additionally influenced the number <strong>of</strong>microorganisms, especially <strong>storage</strong> for 24 h at rt. Ayanaba reported thatmicroorganisms could take part in N-nitrosamines formation in <strong>different</strong> ways: bynitrates reduction to nitrites, degradation <strong>of</strong> proteins to amines and amino acids,production <strong>of</strong> enzymes carrying nitrosation and formation <strong>of</strong> pH suitable for nitrosation(2). Some strains <strong>of</strong> Lactobacillus casei showed a biocatalytic <strong>effect</strong> on the formation<strong>of</strong> nitrosamines, especially the extract <strong>of</strong> their intracellular enzymes (21). Other genus<strong>of</strong> bacteria, like coliforms, Clostridium or Pseudomonas could also synthetizenitrosamines (2, 9, 22).It is known that nitrosation reactions can be influenced by inhibitors (vitaminC and E) or catalysts (metal ions, nucleophilic anions as Cl - or I - , carbonyl compounds)(26). The presence <strong>of</strong> such substances in studied products could not be ruled out. The