Beer, nitrosamines

N-Nitrosamines, formed principally from the reaction of naturally occurring secondary amines with nitrites that may be added to foods or produced by bacterial reduction of nitrates, have been identified in many food systems including cured meat products, nonfat dried milk, dried malt and beer. In addition, the presence of less volatile and non-volatile N-nitroso compounds or their precursors in foods have been suggested from a number of model system studies. 

Nonfat dried milk Dried buttermilk Whole milk (pasteurized) 0.05 - 0.17 N-Nitrosamine in Beers and Malt... 

It has been shown in these studies that the principal, and probably only significant source of NDMA, is malt which had been dried by direct-fired drying (21, 73). It is well known that malts kilned by indirect firing have either low or non-detectable levels of NDMA (74). Consequently, changes in malting procedures have been implemented in both the U.S. and Canada which have resulted in marked reductions in N-nitrosamine levels in both malts and beer (70,74). For example, sulfur dioxide or products of sulfur combustion are now used routinely by all maltsters in the U.S. to minimize N-nitrosamine formation (70). The Canadian malting industry, on the other hand, has... 

Results of a systematic study ( ) of food from the German market indicate the average daily intake for male persons amounts to l.l yg for NDMA and 0.1-0.15 yg for NPYR. Approximately 64% of this total daily intake for NDMA is found in beer, while another 10% comes from cured meat products. It is also important to note that food is not only the only source of N-nitrosamine or N-nitrosatable amines to which we are... 

The complex pattern of human exposure to environmental N-nitroso compounds is summarized. Recent results are given in three areas, where a significant reduction of human exposure has been achieved after elucidation of its causes 1, N-Nitrosodimethylamine in beer. 2, Volatile N-nitrosamines in baby nipples and pacifiers and 3. occupational exposure in the rubber industry. 

We have previously shown in a survey on the occurence of volatile nitrosamines in commercial food of the German market that beer is the most important source of N-nitrosodimethylamine (NDMA) (Spiegelhalder et al, 1979 Preussmann et al., 1980 Spiegelhalder et al, 1980) The investigation of about 3000 food samples allowed the calculation of an average daily intake of 1.1 /ug NDMA and of 0.1-0.15/ig N-nitrosopyrrolidine (NPYR) for a male adult in the year 1978. For NDMA 64% (= 0.7yug/day) of the total daily intake resulted from the consumption of beer. 

In the last fifteen years there has been considerable interest in the analysis of volatile N-nitrosamines in foods. The primary focus has been on meat cured with nitrite (3 ) although nitrosamines have been shown to occur occasionally in other foods such as fish and cheese (, 3) Recently, attention has been directed to volatile nitrosamines in beer and other alcoholic beverages. The purpose of this paper is to review current information on the presence of nitrosamines in beer, and to discuss work done in our laboratory and elsewhere on the mode of formation of nitrosamines in beer. 

Since the first report of N-nitrosodimethylamine (NDMA) contamination in beer (ij ), there have been a number of surveys on volatile nitrosamine occurrence in beers of different types and origins. The data in Table I includes NDMA analyses on light beers, dark beers, ales, and malt liquors. Table I shows that the... 

The data in Table I are also significant in terms of the type of analysis to determine the presence of NDMA. In all cases analysis was done using gas chromatography coupled with a Thermal Energy Analyzer, a sensitive, relatively specific nitrosamine detector (12). Further, in six of the studies, the presence of NDMA in several samples was confirmed by gas chromatography-mass spectrometry (GC-MS). The mass spectral data firmly established the presence of NDMA in the beer samples. 

We recently completed a new survey of 25 beers representing the same labels from similar markets in Oregon and found a mean value of 0.2 ppb, which is more than an order of magnitude lower than the original mean value. The reduction is a direct result of measures taken by the industry to reduce nitrosamine levels in beer. Reduction of nitrosamine levels in beer will be further discussed in the final section of this paper. 

The conversion to indirect-firing is costly both in capital investment and in increased fuel costs nevertheless, much of the U.S. malting industry is converting to indirect-firing because it ultimately may be the most effective method for reducing nitrosamine levels in malt and in beer. 

Beer Samples. The beer samples were examined as part of the American Society of Brewing Chemists (ASBC) and Association of Official Analytical Chemists (AOAC) collaborative studies of NDMA in beer. Duplicate samples were analyzed by the column extraction procedure and the ASBC distillation procedure (35). The AOAC procedure (36) was similar, except that a larger sample (50 vs. 25 g) was examined and sulfamic acid was added to minimize artifactual formation of nitrosamines. Both methods utilize N-nitrosodipropylamine (NDPA) as an internal standard. 

In the AOAC procedure, the beer was treated with dilute HCl and sulfamic acid, and the added acid was then neutralized by addition of dilute alkali. Volatile nitrosamines were collected by atmospheric pressure distillation. The distillate was made alkaline and extracted with DCM. The extract was dried and concentrated to 1.0 ml and an aliquot was analyzed by GC-TEA. We used these concentrates, without further cleanup, for evaluating the GCMS high resolution selected ion monitoring procedure. 

For the AOAC beer samples, a 2 m x 2 mm glass column packed with 8.57o Carbowax 20 M + 0.857, NaOH on 100/120 mesh Chromosorb G was used at 130 C and a helium flow rate of 20 cc/min. Retention times of NDMA and NDPA were 4.5 and 12.2 min, respectively. For the ASBC collaborative study, a 1 m x 2 mm glass column containing 67, Carbowax 20 M-TPA on 100/120 mesh Chromosorb G was operated at 90 C with 20 cc/min helium flow rate. Retention times were 3.6 and 11.3 min for NDMA and NDPA, respectively. For determination of nitrosamines in amines, a 2 m X 2 mm, 107, Carbowax 20 M-TPA on 100/120 mesh Chromosorb G column was operated at 190 C with a carrier gas flow rate of 20 cc/min. Retention times were NPYR, 6.6 min NMOR, 7.4 min. 

Figure 1 shows narrow range high resolution scans of the molecular ion region of NDMA, recorded near the maximum of the GC peaks, present in one of the beer samples prepared in the AOAC collaborative study. The peak at m/z 74.0480 represents approximately 0.15 ng of NDMA injected on the column, corresponding to a concentration of 0.6 yg/kg of beer. Use of high resolution MS permitted confirmation of the identity and amount of nitrosamine without additional cleanup of the concentrate prepared by the AOAC method. Sample quantity requirements were comparable to those of the TEA. 

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... 

The contamination in beer with NOC was first reported in Germany in 197987. The contamination of beer occurs during the kilning (drying) process of malt88 and fermentation89, which leads to the occurrence of NDMS and NPYR. The nitrogen oxides were identified as a source of nitrosamine formation in the beer, formed by nitrosation of the alkaloids... 

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. 

Some nitrosamines have been used as solvents and as intermediates in chemical synthesis. They have been found in a variety of materials to which humans may be exposed, including beer, whiskey, and cutting oils used in machining. 

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]. 

Review of Ascorbic Acid Mechanisms of Action. Ascorbic acid and AP have antioxidant activity in fats, oils, vitamin A, and carotenoids. In these systems AP is a better antioxidant than are the phenolic antioxidants BHT and BHA, both from these data and others (29,35). Ascorbic acid protects against oxidation of flavor compounds in wine, beer, fruits, artichokes, and cauliflower (29) presumably by oxygen scavenging. The well-known formation of nitric oxide from nitrites by ascorbic acid is used not only for inhibition of nitrosamine fortnation, but also to promote... 

A66. Jasinski, J.S. Liquid chromatographic determination of nitrosamines in malt and beer with a photoconductivity detector Anal. Chem. 56 (1984) 2214—2218. 

---