TCA occurs in plants check details at varying levels (Suvachittanont, Kurashima, Esumi, & Tsuda, 1996) with pepper being a potential source of TCA (Fig. 6). Formaldehyde is ubiquitous in the environment and exists at low levels in most living organisms as a metabolic intermediate; however, black pepper also contains substances (e.g. piperine) which can liberate formaldehyde.

Larger amount of formaldehyde is liberated during combustion processes and therefore also produced during wood smoking. High levels of NTCA occur in smoked meat products. The formation of NTCA therefore seems to be limited by the availability of formaldehyde. Formation of NMTCA seems to be less related to the smoking process (Herrmann et al., 2015 and Massey et al., 1991) and dependent on other constituent(s). As Pictilisib order mentioned earlier we performed some preliminary tests on a simpler meat system using minced pork meat, to which only water, nitrite and sodium chloride were added.

In this simple meat system we found that the formation of both NTCA and NMTCA was only limited by nitrite, because saturation curves were observed with increasing ingoing amount of nitrite (data not shown). The addition of tripolyphosphate resulted in no significant main effects (Fig. 3A1–E1). In Fig. 3A2–E2 are the observed interactions presented as interaction plots. If the lines in the interaction plots are parallel it indicates no interaction between the two factors in question (indicated below and in the right side of the figure). Only one significant interaction was observed in this setup. If the PLEK2 level of erythorbic acid was high then the effect of also adding ascorbyl palmitate on the NPRO level (Fig. 3B2) was very limited, whereas if the level of erythorbic acid was low adding ascorbyl palmitate did provide further inhibition. This interaction was also indicated for the other NA. From the interaction plots it also

appears that the distance between the two lines are generally greatest for erythorbic acid which very nicely illustrates that of the tested factors erythorbic acid exhibits the largest effect on the NA levels. Based on the result of this second setup we concluded that black pepper increases the levels of at least two NA of which one is known to be carcinogenic. Besides the ingoing amount of nitrite, erythorbic acid is the factor with the highest impact on the NA levels. Ascorbyl palmitate may contribute to the inhibition of NA and it was therefore chosen to further examine the effect of combining the two antioxidants at different levels (third setup). The results of this third setup are illustrated as surface plots (Fig. 4). As can be seen from these surface plots the levels of NHPRO, NPRO, NPIP and NTCA decrease with increasing amount of erythorbic acid (396, 500, 750, 1000 and 1104 mg kg−1).