Bacon nitrosamines

Sodium nitrite can react with proteins in the stomach or during cooking, especially in high heat (such as frying bacon), to form carcinogenic N-nitrosamines. To prevent this, ascorbic acid or erythor-bic acid is commonly added to cured meats. 

NPYR occurs in processed meats and, most commonly, in cooked bacon NPYR is one of the principal volatile nitrosamines... 

Evidence exists that the relative solubility of amines and inhibitors in heterogeneous oil-water systems could be decisive in formation of nitrosamines and blocking these reactions, Nitrosopyrrolidine formation in bacon predominates in the adipose tissue despite the fact that its precursor, proline, predominates in the lean tissue (5,6,7). Mottram and Patterson (8) partly attribute this phenomenon to the fact that the adipose tissue furnishes a medium in which nitrosation is favored, Massey, et al, (9) found that the presence of decane in a model heterogeneous system caused a 20-fold increase in rate of nitrosamine formation from lipophilic dihexylamine, but had no effect on nitrosation of hydrophilic pyrrolidine. Ascorbic acid in the presence of decane enhanced the synthesis of nitrosamines from lipophilic amines, but had no effect on nitrosation of pyrrolidine. The oil-soluble inhibitor ascorbyl palmitate had little influence on the formation of nitrosamines in the presence or absence of decane. 

Percentage of N-Nitrosamines in the Fumes Produced During the Frying of Bacon or Ham... 

Nitrite concentration The kinetics of N-nitrosamine formation in vitro has been studied at length (, ) and, in moderately acidic media, the reaction rate is directly proportional to the concentration of the free amine (non-protonated) and to the square of the concentration of the undissociated nitrous acid. Therefore, it is not surprising that the amount of nitrite permitted in bacon has received considerable attention. Although, there have been suggestions that it is the initial and not the residual nitrite that influences N-nitrosamine formation in bacon (41), recent evidence seems to indicate that the lowest residual nitrite gives the least probability of N-nitrosamines... 

Recently, Robach et al. ( ) investigated the effects of various concentrations of sodium nitrite and potassium sorbate on N-nitrosamine formation in commercially prepared bacon. 

Bacon, processed with 40 mg/kg of nitrite and 0.26 sorbate contained an average of 8.7 pg/kg of NPYR, whereas samples prepared with 120 mg/kg of nitrite contained an average of 28.1 yg/kg of NPYR. This marked reduction in NPYR levels is clearly due to the reduced levels of nitrite, although it has been reported that sorbic acid also possesses anti-N-nitrosamine activity (47). 

N-Nitrosamine inhibitors Ascorbic acid and its derivatives, andDC-tocopherol have been widely studied as inhibitors of the N-nitrosation reactions in bacon (33,48-51). The effect of sodium ascorbate on NPYR formation is variable, complete inhibition is not achieved, and although results indicate lower levels of NPYR in ascorbate-containing bacon, there are examples of increases (52). Recently, it has been concluded (29) that the essential but probably not the only requirement for a potential anti-N-nitrosamine agent in bacon are its (a) ability to trap NO radicals, (b) lipophilicity, (c) non-steam volatility and (d) heat stability up to 174 C (maximum frying temperature). These appear important requirements since the precursors of NPYR have been associated with bacon adipose tissue (15). Consequently, ascorbyl paImitate has been found to be more effective than sodium ascorbate in reducing N-nitrosamine formation (33), while long chain acetals of ascorbic acid, when used at the 500 and lOOO mg/kg levels have been reported to be capable of reducing the formation of N-nitrosamines in the cooked-out fat by 92 and 97%, respectively (49). 

The inhibition of formation of NPYR and NDMA in fried bacon by the use of cure-solubilized a-tocopherol (500 mg/kg) has been demonstrated by Fiddler et al. (50). Walters et al. (53) also reported reduced levels of N-nitrosamines in the vapors during the frying of bacon in fat containing a-tocopherol. It has also been shown that a-tocopherol is dispersed quite effectively during frying of bacon slices therefore, application to bacon may be made by spray or dip to overcome the problem of water insolubility (51). Controlled addition of this antioxidant may be an effective and practical way of reducing the concentration of N-nitrosamines in cooked... 

Smoking. The effects of smoking on the formation of N-nitros-amines in bacon has been investigated recently by Bharucha et al. ( ). They reported that unsmoked bacon samples generally tended to contain more N-nitrosamines, presumably because of their higher nitrite content at the time of frying. Sink and Hsu (55) showed a lowering of residual nitrite in a liquid smoke dip process for frankfurters when the pH also was lowered. The effects of smoke seem to be a combination of pH decrease and direct C-nitrosation of phenolic compounds to lower the residual nitrite in the product (56). This is an area which requires further study since certain C-nitrosophenols have been shown to catalytically transnitrosate amines in model systems (57). 

N-Nitrosamines in Cured Meats Other Than Bacon. The presence of N-nitrosamines in cured meats other than bacon has been the subject of several recent surveys (19,58,59). In general, the majority of the positive samples contained extremely low levels of N-nitrosamine, usually less than I yg/kg (19,58). This low level could, in part, be attributed to the discontinuation of the use of nitrite-spice premixes in the mid-l970 s (l 9). In the Holland study (59), the predominant N-nitrosamines detected were NDMA and N-nitrosomorpholine (NMOR) and, generally, values of 4 yg/kg were obtained for each N-nitrosamine. More correctly, these are presumptive N-nitrsoamine levels since mass spectral confirmation of their identities was not achieved. 

Decomposition studies confirmed that N-nitrosamides are much less stable than volatile N-nitrosamines such as NPYR and NDMA (79). Thermal studies utilizing heating conditions commonly encountered in the cooking of bacon and pork roasts indicated that N nitrosomethylpropionamide (NOMP) was degraded to the extent of 74-97% compared to 3-14% for NPYR and NDMA (Table V). It was tentatively concluded that the major... 

The formation of nitrosamines in aprotic solvents has applicability to many practical lipophilic systems including foods (particularly bacon), cigarette smoke, cosmetics, and some drugs. The very rapid kinetics of nitrosation reactions in lipid solution indicates that the lipid phase of emulsions or analogous multiphase systems can act as "catalyst" to facilitate nitrosation reactions that may be far slower in purely aqueous media (41, 53, 54). This is apparently true in some cosmetic emulsion systems and may have important applicability to nitrosation reactions in vivo, particularly in the GI tract. In these multiphase systems, the pH of the aqueous phase may be poor for nitrosation in aqueous media (e.g., neutral or alkaline pH) because of the very small concentration of HONO or that can exist at these pH ranges. 

Various NOC can be found in food processing operations. The most commonly known contributors to dietary volatile and non-volatile N-nitrosamines are nitrite cured meats, particularly fried bacon and beer. Several reviews cover the occurrence and formation of... 

Vapors horn cooking. About 90% of NDMA and 75% of NPYR formed in cooked bacon is lost through evaporation during frying (44,45). It has been calculated that the airborne nitrosamine levels in a typical kitchen could be as high as 56 ng/m3 of NDMA and 560 ng/m3 of NPYR (16). However, the exposure would be of short duration (<1 hr.) and the total nitrosamine intake would be small. 

Relative Risks of Nitrosamines. The mere existence of reproducible variations in carcinogenicity from one nitrosamine to another is directly relevant to the question of potential human health hazards from environmental nitrosamines. The problem of nitrosamines in cooked bacon is a simple and straightforward example. 

Several nitrosamines, including N-nitrosopyrrolidine (NP), N-nitrosodimethylamine (NDMA), and N-nitrosodiethylamine (NDEA), have been detected at various concentrations in this food. Table lists some typical values for the concentrations of these compounds in cooked bacon and some other prepared meat products (14). Nitrosopyrrolidine has been generally found, especially in bacon, at much higher levels than NDMA or NDEA, and most attention has consequently been directed toward this compound (15, 16). 

Concentration of nitrosamines in processed meats, including bacon... 

This analysis, along with some observations concerning the possible absolute hazards arising from nitrosamines in bacon, has been detailed in an earlier report (17). 

The major health concern regarding use of curing salts is the possibility of nitrosamine formation in the cured products. Nitrite ion appears to be the precursor compound required for nitrosamine formation, rather than NO. Inclusion of reductants such as ascorbate, now required in bacon, lowers nitrite level in the product and increases the level of NO available for cured meat color formation and stability. 

Compared to the worst case exposure from the fourth NIOSH survey, a worker in this area now would inhale approximately 6.0 yg of nitrosamines per shift, an exposure equivalent to eating a few strips of bacon and drinking a liter of beer. 

Any secondary amine will react with nitrous acid to form a nitrosamine (Eq. 27-25). Tertiary amines can also react with loss of one alkyl group. This can occur in the stomach, and the nitrosamines may be absorbed into the system. All plants contain some nitrate and some, such as spinach and beets, have large amounts. Bacon and other cured R R meats contain both nitrites and nitrates, and many drugs and natural food... 

The promising contribution of adding tocopherol to bacon, along with sodium ascorbate, to inhibit nitrosamine formation undertaken by Mergens and associates is reported in detail in the Mergens et al, reference (1978). 

The most important sources of A-nitrosamines in terms of NDMA in the human diet are the following fried bacon, smoked meat, smoked fish (0.4 40 mg/kg), wine (10-21 mg/kg), and beer (0.1-0.5 mg/kg) [79]. 

Nitrosamines can be formed when amines that occur naturally in food react with sodium nitrite, NaN02, a preservative added to meats such as ham, bacon, and hot dogs to inhibit the growth of Clostridium botulinum, a bacterium responsible for a lethal form of food poisoning. Nitrosamines may also be formed in vivo in the gastrointestinal tract when bacteria in the body convert nitrates (N03 ) into nitrites (NO2 ), which then react with amines. 

Several ascorbic acid derivatives were examined by Pensabene et al. (570) for their ability to inhibit nitrosation of pyrrolidine in a model system developed to simulate the lipid-aqueous-protein composition of bacon. While sodium ascorbate was quite effective in the aqueous phase, a combination of an ascorbyl ester with sodium ascorbate gave a better effect in the lipid phase (Table XX). The use of ascorbates and tocopherol as inhibitors of nitrosamine formation and oxidation in foods of the aqueous and lipid type has been reviewed by Newmark and Mergens (326). These compounds in combination could be markedly useful in preventing food contamination with nitrosamines and/or nitros-amides in cured meats such as bacon. 

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