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Foods and Raw Materials, 2020, vol. 8, no. 1
E-ISSN 2310-9599 ISSN 2308-4057
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DOI: http://doi.org/10.21603/2308-4057-2020-1-107-114 Available online at http://jfrm.ru/en/
Volatile N-nitrosamine, residual nitrite, and ascorbic acid levels
in sausages during storage
Houra Ramezani, Khadijeh Abhari , Zahra Pilevar , Hedayat Hosseini* ,
Abdorreza Mohammadi**
Food Sciences and Technology Department, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
* e-mail: [email protected]
** e-mail: [email protected]
Received September 01, 2019; Accepted in revised form November 13, 2019; Published February 25, 2020
Abstract:
Introduction. The increasing global consumption of processed meat products has led to certain concerns. For instance, processed meat products are known to contain carcinogen precursor compounds, thus creating the risk of chronic diseases. The present study was performed to estimate the food safety status of processed meat products available in Iran and evaluate the related effective factors.
Study objects and methods. 140 samples of seven most popular commercial types of cooked sausages were obtained from four major meat factories (A, B, C and D) in 140 samples were collected from seven most popular commercial types of cooked sausages as follows: beef salami 90%, chicken salami 90%, dry cured sausage 70%, dry cured salami 60%, beef sausages 55%, chicken sausages 55% and Frankfurt sausage 40% (n = 5) from four major meat factories (A, B, C and D) in Tehran. The samples were screened for residual nitrite, ascorbic acid, and nitrosamine contents on days 0, 7, 14, 21, and 28. The results indicated that products from meat factory B had lower residual nitrite content in the samples with high content of meat. Beef salami (90% of meat) and Frankfurt sausage (40% of meat) contained the lowest and highest amounts of residual nitrite on day 0 - 73.99 and 177.42 mg of nitrite per 1 kg of meat, respectively.
Results and discussion. Beef salami contained 90% of meat, chicken salami - 90%, dry cured sausage -70%, dry cured salami -60%, beef sausages - 55%, chicken sausages - 55%, and Frankfurt sausage - 40% (n = 5). Nitrite reduction rates in sausages with a smaller diameter, e.g. Frankfurt sausage, were significantly lower (P < 0.05), compared to salami samples. The difference can be explained by the shorter cooking time. Nitrosamine formation increased during refrigerated storage; however, it was not significant in all samples. During refrigerated storage, nitrosamine formation depended on the level of added nitrite, the amount of residual nitrite, ascorbic acid, pH, and cooking temperature. Ascorbic acid content decreased significantly (P < 0.05) during refrigerated storage.
Conclusion. The findings demonstrate significant correlation between the meat content, cooking time, nitrite content, and nitrosamine formation.
Keywords: Meat industry, processed meat, meat products safety, carcinogenic agents, preservation
Funding: This research was financially supported by National Nutrition and Food Technology Research Institute (NNFTRI) of Iran.
Please cite this article in press as: Ramezani H, Abhari K, Pilevar Z, Hosseini H, Mohammadi A. Volatile N-nitrosamine, residual nitrite, and ascorbic acid levels in sausages during storage. Foods and Raw Materials. 2020;8(1): 107-114. DOI: http://doi.org/10.21603/2308-4057-2020-1-107-114.
INTRODUCTION
To reduce the adverse effects of red meat and artificial additives on human health, one can reduce the consumption of red meat or processed meat products. However, studying possible ways to reduce the harmful effects might be as effective as limiting consumption levels. Nitrite/nitrate salts are usually added to meat products to guarantee their safety, since these salts inhibit the growth of Clostridium botulinum and prevent
heat-resistant spores from producing toxins. Moreover, nitrite/nitrate salts improve the color, flavor, and aroma of the finished product and postpone lipid oxidation processes [1].
In spite of the numerous advantages, an excessive intake of nitrite can produce adverse effects on human health. Nitrite can be transformed to a nitrosating agent (NO+), which reacts with biogenic amines and creates carcinogenic N-nitrosamines. Bacterial and meat
Copyright © 2020, Ramezani et al. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license.
enzymes cause decarboxylation of free amino acids, which leads to the formation of biogenic amines. Several intrinsic and extrinsic factors, e.g. salt content, can also affect the biogenic amine formation level [2-4].
In meat and meat products, carcinogenic N-nitrosamines are usually formed under acidic conditions caused by the electrophilic reaction between a nitrosating agent, e.g. nitrite or nitrous acid, and secondary/tertiary amines that result from protein and lipid degradation [5]. The mechanism of nitrosamine formation in meat products has been thoroughly studied. Nitrosamines with generic chemical structure of R2NN = O are produced under certain conditions of low pH, high temperature, and presence of some reducing agents associated with processing and composition of a particular meat product [6]. There are several hurdle technologies that can reduce the concentration of nitrite required to inhibit bacterial growth, e.g. ascorbic/erythorbic (isoascorbic) acid and essential oils, certain processing conditions, or various non-thermal methods [1, 7]. Exposure level of N-nitrosodimethylamine (NDMA) compound via consumption of food and beverages was estimated to be 0.09 and 0.1 ^g/day in the Netherlands and Germany, respectively [8, 9]. The level of these compounds in nitrite-preserved meat products varies significantly. It depends on the ingoing volume of nitrite, meat quality, and fat content, as well as on processing, ripening, and storing conditions. There have been many reports on nitrosamines detected in processed meat products [10, 11].
The research objective was to examine the safety of emulsion-type cooked sausages available on the Iran markets by assessing the contents of residual nitrite, ascorbic acid, and nitrosamine. In addition, we also studied the effects of processing conditions and related factors on these compounds to provide information for health professionals and food manufacturers.
STUDY OBJECTS AND METHODS
Samples. The samples were collected from four major meat factories in Tehran (A, B, C, and D) out of the total of 189 meat factories in Iran. Seven most popular commercial types of cooked sausages were randomly purchased. Seven most popular commercial types of cooked sausages were randomly purchased as follows: beef salami 90%, chicken salami 90%, dry cured sausage 70%, dry cured salami 60%, beef sausages 55%, chicken sausages 55% and Frankfurt sausage 40%.
Five samples (2 kg) from each type were examined on days 0, 7, 14, 21, and 28 of storage. The samples contained beef (15% fat) orchicken (10% fat), water, oil, sodium caseinate, sodium polyphosphate, garlic, salt, wheat flour starch, spices, gluten, natural flavorings (paprika, curcumin, ginger, and cinnamon), ascorbic acid, and sodium nitrite. The samples were immediately transferred to the laboratory and kept refrigerated until tested.
Residual nitrite determination. The nitrite content was evaluated during 28 days on days 0, 7, 14, 21, and 28 using slightly modified calorimetric method of AOAC method no. 973.31 [12]. The samples were cut into pieces and homogenized. An aliquot of about 2.5 g of minced sausage was added to 5 mL of saturated borax and 25 mL of deionized water (> 70°C) in Falcon tubes. After stirring and cooling in room temperature, 1 mL of each Carrez solution (I and II) was added to each sample and adjusted to the volume of 50 mL. Carrez solution
I was prepared by dissolving 10.6 g of ferrocyanide in distilled water (100 mL) according to the method introduced by Ramezani et al. [13]. Carrez solution
II was also made by mixing 21.9 g of zinc acetate with acetic acid (3 mL) and adjusted to the volume of 100 mL using distilled water. After centrifugation at 4000 rpm for 5 min (HeltichRotorfix 32A), 25 mL of supernatant was transferred to a 100 mL tube. Ten ml of sulfanilamide reagent and 6 mL of dilute HCl were added to the supernatants and kept in the dark for 5 min. Then, 2 mL of naphtyl-ethylenadiamine solution was added to obtain high intensity azo dyes. The samples were kept in the dark for 10 min to achieve complete reactions. Absorbance was measured at 538 nm.
Ascorbic acid determination. To determine the ascorbic acid content, 2 g of minced sausage was mixed with 10 mL of meta-phosphoric acid solution (3%), tertiary butylhydroquinone (TBHQ) (0.1%), and acetic acid (8%). After that, they were centrifuged at 4000 rpm for 10 min. After filtration, 20 ^L of supernatant solution was injected to a Cecil CE-4900 high-performance liquid chromatograph coupled to a UV-vis detector (HPLC-UV/VIS, Cambridge, England). The analytical HPLC was equipped with two CE-4100 pumps, vacuum degasser, six port valves (Rheodyne, USA), mixing chamber, multiple solvent delivery unit, and an ODS column (250 mm-4 I.D., 5 ^m). The mobile phase consisted of acetonitrile and sodium phosphate buffer solution (50:50). The flow rate was 1.2 mLmin-1 at room temperature [14].
N-nitrosamine determination. The experiment evaluated seven volatile nitrosamines in the popular cooked sausages from four major Iran meat factories. The nitrosamines included N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitroso-morpholine (NMOR), N-nitrosopyrrolidine (NPYR), N-nitrosopiperidine (NPIP), N-nitrosodi-n-butylamine (NDBA), and N-nitrosodiphenylamine (NDPheA). The presence of nitrosamine was determined and quantified according to the method described in our previous study [13]. The method presupposed using microwave-assisted extraction coupled with dispersive liquidliquid micro extraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS).
Statistical analysis. All experiments were carried out in triplicate. One-way ANOVA was performed to determine significant differences. Duncan's multiple
range test was used to define the differences of mean value. Data analysis was performed using SPSS version 21 (SPSS Inc., Chicago, IL, USA); P < 0.05 was considered statistically significant.
RESULTS AND DISCUSSION
The present research featured samples from seven most popular types of sausages in Iran. The selected sausages differed in the amount of nitrite, ascorbic acid, and nitrosamine. This difference is associated with the variations in concentration of added nitrate and nitrite salts (sodium and potassium), storage conditions, and different pH values [15, 16]. Following the EU legislations, 2006/52/EC directive limited the usage of nitrite to 150 mg per 1 kg of meat. However, the national laws in Iran are more restricting. Iranian provisions allow for maximum 120 mg of nitrite per 1 kg of meat (ppm) in sausages [17]. Table 1 displays the residual nitrite, ascorbic acid, and nitrosamine contents in the meat samples under study during storage.
Figure 1 illustrates the results of nitrite content changes (mg/kg meat) in the meat samples obtained from factory B as representative of all the four meat factories.
As it was expected, the amount of nitrite residue in meat products of all four meat factories decreased during 28 days of refrigerated storage. The increase in meat content increased the reduction rate of sodium nitrite in the products. In other words, lower residual nitrite content was detected in high content meat samples. The highest reduction rate of nitrite content was observed in chicken and beef salami (90% of meat). On the first day of refrigerated storage, the Frankfurt sausage (40%) and both beef and chicken sausages (55%) contained 80 ^g/kg of nitrite.
The detected amount exceeded the level permitted by Iranian laws as defined by the Institute of Standard and Industrial Research of Iran (ISIRI). The maximum permissible burden of nitrite is 66 and 63 ^g/kg for processed meat products with 40% and 55% of meat content, respectivelyI. The concentration of nitrite was higher than the expected levels even after 28 days of storage. However, the residual nitrite content was not exactly equal to the initial added nitrite. First, it was partly degraded by heating process. Second, it decreased when ascorbic acid was applied to the meat product during the heating process to accelerate conversion of nitrite to nitric oxide.
The nitrite content varied due to interaction with heme-containing components, non-heme proteins, and fat tissues, conversion to nitrate, production of such gases as N2, CO2, and NO, and nitrosamines [18]. Therefore, residual nitrite was associated with meat content due to different contents of myoglobin [19]. As a reactive agent, nitrite converts to nitrite oxide and forms
: ISIRI 932. Test method for determination of nitrite in meat and meat products (reference method). Iran: Iran Institute of Standards and Industrial Research; 2014.
Time, day
(1) Beef salami 90% (5) Chicken salami 90%
(2) Dry cured salami 60% (6) Beef sausage 55%
(3) Chicken sausage 55% (7) Dry cured sausage 70%
(4) Frankfurt sausage 40%
Figure 1 Residual nitrite content (mg/kg meat) in sausages with different meat content from factory B on days 0, 7, 14, 21, and 20
nitrite-heme-nitrosomyoglobin complex with myoglobin, thus producing nitrosomyochromogen. The latter is responsible for the characteristic bright pink color of cured meat products [20].
Hence, lugher content of myoglobin results in tower nitrite content in the final meat product. The results obtained by analysis mdicate that residual
nitrite iy Feankfurt 0ausage (40%e was segmficantly higher (/^O.OSX whereas in beef sylami (У0%) it was at its lowest. No significant differences were observed in other saunage aad aiakmi products (P > 0.05).
Ascorbic acid, or ascorbate, is applied to meat products as an additive with high water solubility for three major reasons. First, the nitrosomyoglobin-forming reduction of nitrite to nitric oxide produces the required color. Second, the antioxidative activity of ascorbic acid slows down oxidation of pigments and lipids, which results in color and flavor stability. Third, residual nitrite decreases due to binding to nitrite in heated samples [21].
Ascorbate proved effective in eitrosamine inhibition. This quality is associated with rapid reactions of ascorbate with nitric oxide compared to nitrosating agents, e.g. amines. Therefore, nitrosamines are formed when the reaction rate constant of ascorbate is not much larger than amines [16]. Figure 2 and Table 1 demonstrate that ascorbic acid content of samples decreased significantly (P < 0.05) during refrigerated storage.
Meat products with higher meat content exhibited lower ascorbic acid reduction rate, which was due to lower residual nitrite content. Ascorbic acid degradation in meat products could be related to oxygen content, temperature, light, water activity, presence of metal ions, e.g. copper and ferric iron, and storage time [22-24]. Degradation of ascorbic acid is increased in acidic conditions (pH = 3.3-5.5). In the current study,
Table 1. Residual nitrite, ascorbic acid and nitrosamine contents in sausages produced by four major meat factories during storage
Factory A Day 0 Day 7 Day 14 Day 21 Day 28
Beef salami Nitrite, mg/kg 67.91 ± 0.605a 59.95 ± 0.360b 46.06 ± 0.326c 27.75 ± 0.119d 16.07 ± 0.294e
(90% of meat) Nitrosamine, ng/g 5.43 ± 0.004a 6.71 ± 2.887b 13.44 ± 0.033c 17.25 ± 0.563d 22.01 ± 0.038e
Ascorbic acid, ng/g 214.08 ± 0.262a 216.81 ± 0.026a 194.98 ± 0.018b 171.95 ± 0.017c 167.82 ± 0.026c
Chicken salami Nitrite, mg/kg 73.20 ± 0.376a 62.90 ± 0.134b 51.72 ± 0.226c 33.00 ± 0.156d 17.75 ± 0.356e
(90% of meat) Nitrosamine, ng/g 6.30 ± 0.135a 10.91 ± 0.173b 16.47 ± 0.610c 18.68 ± 0.856c 22.44 ± 0.616d
Ascorbic acid, ng/g 175.39 ± 0.039a 168.53 ± 0.003a 159.21 ± 0.027b 140.84 ± 0.039c 134.40 ± 0.021d
Dry cured salami Nitrite, mg/kg 90.93 ± 1.036a 85.00 ± 0.457b 72.64 ± 0.678c 61.36 ± 0.719d 36.73 ± 0.381e
(60% of meat) Nitrosamine, ng/g 6.93 ± 0.0561a 14.77 ± 0.037b 18.03 ± 0.060c 21.82 ± 0.518d 24.67 ± 0.091e
Ascorbic acid, ng/g 185.86 ± 0.021a 180.79 ± 0.003b 172.05 ± 0.062c 168.86 ± 0.683d 162.35 ± 0.706d
Beef sausage Nitrite, mg/kg 181.80 ± 0.274a 137.28 ± 0.760b 108.10 ± 0.716c 83.97 ± 0.080d 70.78 ± 0.387e
(55% of meat) Nitrosamine, ng/g 14.47 ± 0.399a 24.80 ± 1.06b 32.31 ± 0.389c 33.60 ± 0.566c 42.52 ± 1.077d
Ascorbic acid, ng/g 198.22 ± 0.149a 203.91 ± 0.057a 196.78 ± 0.031a 182.49 ± 0.033b 175.88 ± 0.018c
Chicken sausage Nitrite, mg/kg 187.42 ± 0.315a 145.40 ± 0.447b 114.00 ± 0.151c 91.21 ± 1.279d 76.29 ± 0.390e
(55% of meat) Nitrosamine, ng/g 7.71 ± 0.075a 25.96 ± 0.1063b 33.32 ± 0.053c 34.29 ± 0.067c 41.91 ± 0.0167d
Ascorbic acid, ng/g 165.27 ± 0.009a 163.34 ± 0.009a 161.99 ± 0.024a 158.26 ± 0.072b 149.46 ± 0.031c
Dry cured sausage Nitrite, mg/kg 82.11 ± 0.757a 69.78 ± 0.758b 54.94 ± 0.115c 46.35 ± 0.314d 39.79 ± 1.206e
(70% of meat) Nitrosamine, ng/g 14.32 ± 0.052a 15.36 ± 0.012a 17.86 ± 0.083ab 20.81 ± 0.765b 21.55 ± 0.045b
Ascorbic acid, ng/g 129.67 ± 0.416a 120.55 ± 0.007ab 117.99 ± 0.033b 106.79 ± 0.039c 105.82 ± 0.705c
Factory B Day 0 Day 7 Day 14 Day 21 Day 28
Beef salami Nitrite, mg/kg 73.99 ± 0.011a 54.53 ± 0.130b 48.76 ± 0.649c 32.60 ± 0.626d 30.20 ± 0.598d
(90% of meat) Nitrosamine, ng/g 3.06 ± 0.058a 5.13 ± 0.204ab 7.05 ± 0.284b 13.40 ± 0.122c 14.18 ± 0.1054c
Ascorbic acid, ng/g 194.99 ± 0.016a 192.30 ± 0.021a 165.00 ± 0.699b 144.62 ± 0.004c 121.60 ± 0.060d
Chicken salami Nitrite, mg/kg 77.55 ± 0.556a 72.12 ± 0.505a 55.24 ± 0.247b 44.41 ± 0.830c 31.62 ± 0.347d
(90% of meat) Nitrosamine, ng/g 4.85 ± 0.045a 4.83 ± 0.018a 6.43 ± 0.09a 11.43 ± 0.065b 14.81 ± 0.031b
Ascorbic acid, ng/g 220.79 ± 0.022a 192.84 ± 0.554b 168.95 ± 0.134c 164.89 ± 0.025c 134.07 ± 0.492d
Dry cured salami Nitrite, mg/kg 101.79 ± 0.290a 94.85 ± 0.362a 76.18 ± 0.359b 63.30 ± 0.244c 49.24 ± 0.396d
(60% of meat) Nitrosamine, ng/g 11.93 ± 0.081a 15.20 ± 0.256ab 15.32 ± 0.298ab 21.68 ± 0.307b 28.38 ± 0.575c
Ascorbic acid, ng/g 201.24 ± 0.127a 188.65 ± 0.038b 172.34 ± 0.401c 168.01 ± 0.002d 145.69 ± 0.018e
Beef sausage Nitrite, mg/kg 156.45 ± 0.774a 128.46 ± 0.637b 95.54 ± 0.323c 87.82 ± 0.296d 65.26 ± 0.971e
(55% of meat) Nitrosamine, ng/g 13.21 ± 0.057a 14.94 ± 0.04a 23.64 ± 0.075b 29.54 ± 0.94c 37.73 ± 0.059 d
Ascorbic acid, ng/g 200.90 ± 0.132a 193.71 ± 0.015ab 187.60 ± 0.345b 183.60 ± 0.031b 174.74 ± 0.297c
Chicken sausage Nitrite, mg/kg 149.47 ± 0.197a 126.70 ± 0.516b 98.98 ± 0.708c 86.83 ± 0.681d 71.21 ± 0.192e
(55% of meat) Nitrosamine, ng/g 7.85 ± 0.118a 14.70 ± 0.077b 24.73 ± 0.053c 29.77 ± 2.93d 37.99 ± 0.133e
Ascorbic acid, ng/g 181.71 ± 0.014a 160.27 ± 0.020b 138.63 ± 0.013c 121.13 ± 0.003d 104.42 ± 0.005e
Dry cured sausage Nitrite, mg/kg 106.62 ± 0.277a 87.71 ± 0.850b 79.26 ± 0.211c 65.21 ± 0.306d 57.90 ± 0.226e
(70% of meat) Nitrosamine, ng/g 8.18 ± 0.202a 9.71 ± 0.469a 15.22 ± 0.085b 25.88 ± 0.1589c 33.16 ± 0.622d
Ascorbic acid, ng/g 197.86 ± 0.215a 156.10 ± 0.021b 131.45 ± 0.073c 127.63 ± 0.015d 126.30 ± 0.007d
Frankfurt sausage Nitrite, mg/kg 177.42 ± 0.677a 141.07 ± 0.075b 103.64 ± 0.280c 88.45 ± 0.662d 78.61 ± 0.710e
(40% of meat) Nitrosamine, ng/g 14.34 ± 0.05a 16.12 ± 0.6746b 27.20 ± 0.116c 34.97 ± 0.202c 45.06 ± 0.229d
Ascorbic acid, ng/g 192.57 ± 0.062a 187.08 ± 0.032b 169.47 ± 0.057c 155.29 ± 0.008d 137.55 ± 0.006e
Factory C Day 0 Day 7 Day 14 Day 21 Day 28
Beef salami Nitrite, mg/kg 59.08 ± 0.199a 35.41 ± 0.347b 25.26 ± 0.952c 18.25 ± 0.297d 8.42 ± 0.088e
(90% of meat) Nitrosamine, ng/g 2.65 ± 0.0123a 8.37 ± 0.058b 15.51 ± 0.021c 19.27 ± 0.057c 33.83 ± 0.123d
Ascorbic acid, ng/g 232.27 ± 0.0321a 187.13 ± 0.060b 135.76 ± 0.025c 122.71 ± 0.031cd 108.52 ± 0.026d
Chicken salami Nitrite, mg/kg 62.90 ± 0.220a 50.30 ± 0.589b 36.67 ± 0.347c 19.66 ± 0.714d 9.26 ± 0.076d
(90% of meat) Nitrosamine, ng/g 2.78 ± 0.071a 9.68 ± 0.078b 14.47 ± 0.064c 18.59 ± 0.083d 25.34 ± 0.117e
Ascorbic acid, ng/g 162.54 ± 0.055a 155.95 ± 0.086b 121.19 ± 0.060c 103.93 ± 0.112d 92.68 ± 0.049e
Dry cured salami Nitrite, mg/kg 69.96 ± 0.912a 65.00 ± 0.721a 50.22 ± 0.977ab 36.57 ± 0.386b 19.17 ± 0.448c
(60% of meat) Nitrosamine, ng/g 3.51 ± 0.007a 11.91 ± 0.042b 19.61 ± 0.047c 22.57 ± 0.052d 23.76 ± 0.052d
Ascorbic acid, ng/g 248.29 ± 0.004a 213.54 ± 0.630b 198.32 ± 0.016b 165.78 ± 0.032c 119.79 ± 0.296d
Beef sausage Nitrite, mg/kg 107.41 ± 0.682a 92.93 ± 0.114ab 85.60 ± 1.314b 64.39 ± 0.142c 31.88 ± 0.397d
(55% of meat) Nitrosamine, ng/g 8.61 ± 0.157a 17.01 ± 0.05b 20.51 ± 0.547b 34.51 ± 0.068c 44.20 ± 0.051d
Ascorbic acid, ng/g 200.69 ± 0.45a 196.17 ± 0.057a 189.30 ± 0.047ab 175.08 ± 0.107b 142.58 ± 0.117c
Chicken sausage Nitrite, mg/kg 116.20 ± 0.725a 93.36 ± 0.354ab 81.96 ± 0.279b 55.90 ± 0.374c 47.44 ± 0.658d
(55% of meat) Nitrosamine, ng/g 9.85 ± 0.011a 16.19 ± 0.145ab 20.51 ± 0.547b 35.51 ± 0.068c 44.20 ± 0.051d
Ascorbic acid, ng/g 199.63 ± 0.588a 184.59 ± 0.068b 165.67 ± 1.013c 102.61 ± 0.173d 79.79 ± 0.033e
Continuation of the table 1
Dry cured sausage Nitrite, mg/kg 84.48 ± 0.188' 71.59 ± 0.763b 57.72 ± 0.274c 50.18 ± 1.247c 27.29 ± 0.242d
(70% of meat) Nitrosamine, ng/g 10.05 ± 0.033a 10.35 ± 0.048a 17.68 ± 0.031b 20.81 ± 0.080c 23.44 ± 0.037d
Ascorbic acid, ng/g 149.83 ± 0.017a 114.28 ± 0.177b 103.91 ± 0.122c 89.73 ± 0.145d 71.32 ± 0.035e
Frankfurt sausage Nitrite, mg/kg 135.79 ± 1.314a 98.41 ± 1.405b 82.62 ± 0.592c 80.51 ± 0.754c 52.84 ± 0.489d
(40% of meat) Nitrosamine, ng/g 10.05 ± 0.087a 17.95 ± 0.086b 24.09 ± 0.105c 37.80 ± 0.065d 41.32 ± 0.090e
Ascorbic acid, ng/g 141.12 ± 0.059a 138.09 ± 0.012a 102.27 ± 0.027b 91.43 ± 0.068b 74.10 ± 0.707c
Factory D Day 0 Day 7 Day 14 Day 28
Beef salami Nitrite, mg/kg 96.65 ± 0.646a 75.59 ± 0.754b 59.11 ± 1.413c 52.95 ± 1.361cd 47.94 ± 0.628d
(90% of meat) Nitrosamine, ng/g 28.96 ± 0.026a 34.52 ± 0.042ab 39.02 ± 0.054b 44.38 ± 0.048bc 49.52 ± 0.077c
Ascorbic acid, ng/g 233.43 ± 0.202a 195.42 ± 0.054b 163.34 ± 0.095c 157.90 ± 0.158c 132.90 ± 0.167d
Dry cured salami Nitrite, mg/kg 101.88 ± 0.611 90.53 ± 0.437a 78.70 ± 0.650b 66.24 ± 0.271c 53.22 ± 0.917d
(60% of meat) Nitrosamine, ng/g 31.53 ± 0.017a 35.12 ± 0.051ab 39.81 ± 0.029b 44.46 ± 0.036c 48.46 ± 0.036c
Ascorbic acid, ng/g 169.07 ± 0.115a 157.47 ± 0.032b 114.25 ± 0.174c 103.32 ± 0.151d 89.92 ± 0.341e
Beef sausage Nitrite, mg/kg 114.24 ± 0.862a 99.66 ± 0.920ab 86.06 ± 0.526b 73.10 ± 1.452c 61.39 ± 0.122d
(55% of meat) Nitrosamine, ng/g 38.02 ± 0.031 74.74 ± 0.136b 94.90 ± 0.021c 124.58 ± 0.033d 131.558 ± 0.063d
Ascorbic acid, ng/g 198.59 ± 0.035a 104.30 ± 0.240b 54.95 ± 0.079c 35.61 ± 0.162d 29.11 ± 0.452d
Chicken sausage Nitrite, mg/kg 143.09 ± 0.787a 127.56 ± 0.488b 98.24 ± 0.196c 72.37 ± 0.808d 55.95 ± 0.069e
(55% of meat) Nitrosamine, ng/g 38.02 ± 0.562a 68.88 ± 0.125b 70.90 ± 0.152b 85.94 ± 0.099c 89.91 ± 0.059c
Ascorbic acid, ng/g 201.10 ± 0.351a 173.31 ± 0.494b 138.33 ± 0.442c 90.33 ± 0.953d 68.82 ± 0.721d
Frankfurt sausage Nitrite, mg/kg 150.45 ± 1.003a 135.95 ± 0.765b 109.52 ± 1.216c 97.55 ± 0.084d 80.41 ± 0.784e
(40% of meat) Nitrosamine, ng/g 12.91 ± 0.085a 38.73 ± 0.039b 100.42 ± 0.093c 153.60 ± 0.253d 178.60 ± 0.293e
Ascorbic acid, ng/g 282.14 ± 0.310a 181.60 ± 0.025b 170.03 ± 0.169c 117.97 ± 0.037d 75.22 ± 0.897e
Different letters in the same row during storage within the same section (i.e. factories A-D) indicate a significant difference (P < 0.05)
pH values were in the range of 5-6 in all samples. Therefore, ascorbic acid degradation might have been due to the relative acidic condition of meat products and heating process.
The obtained results showed an increase in nitrosamine content of samples during refrigerated storage. However, it was not significant in all samples (Fig. 3).
The nitrite reduction rates in the sausages with a smaller diameter, e.g. Frankfurt sausage, appeared significantly lower (P < 0.05) than in the samples with a bigger diameter, e.g. salami. This difference can be
explained by the longer cooking time for salami (5-6 h) compared to Frankfurt sausages (3-4 h), which is associated with a higher reduction rate of residual nitrite. According to the results, the total volatile mtrosamine level of Iranian meat products with lower meat contents was generally higher than that of samples with high meat contents. The mtrosamine content in meat products was associated with the added nitrite and the residual nitrite [25]. The residual nitrite is a reactive agent that can be reduced by heating treatment or exposureto such meat components asproteins, lipids, and pigments[26, 27].
240
21
28
(1) Beef salami 90%
(2) Dry cured salami 60%
(3) Chicken sausage 55%
(4) Frankfurt sausage 40%
14
Time, day
(5) Chicken salami 90%
(6) Beef sausage 55%
(7) Dry cured sausage 70%
a a
50
40
30
20
10
14
Time, day
21
28
(1) Beef salami 90%
(2) Dry cured salami 60%
(3) Chicken sausage 55%
(4) Frankfurt sausage 40%
(5) Chicken salami 90%
(6) Beef sausage 55%
(7) Dry cured sausage 70%
Figure 2 Ascorbic acid content (ng/kg meat) in sausages with different meat content from factory B on days 0, 7, 14, 21, and 28
Figure 3 M^sam^ content (ng/kg of meat) in sausages with different meat content from factory B on days 0, 7, 14, 21, and 28
0
0
7
0
7
0 7 14 21 28
Time, day
(1) Factory A (2) Factory B (3) Factory C (4) Factory D
Figure 4 Correlation between residual nitrite content and nitrosamine in beef salami (90% meat) samples
Figure 4 shows that there was a significant correlation between the amounts of added nitrite and the nitrosamine contents in beef salami (90%) samples from all four meat factories.
In this study, the correlation factor was 0.9, which asserts the effects of added nitrite and also residual nitrite contents on nitrosamine formation in the processed meat product. Therefore, the products with lower meat content showed higher residual nitrite and, consequently, a greater nitrosamine formation. In meat products, presence of nitrosating agents increases the concentration of nitrosamine, whether grouped in NO2 related agents, e.g. N2O4, or grouped in nitrous acid derivatives, e.g. N2O3 and HNO2 [28].
There are several suggested strategies to reduce nitrosamine formation in meat products to improve their healthy status and safety. The present research clarified that the levels of nitrosamines in the samples depended on the amount of residual nitrite, ascorbic acid, pH, and cooking temperature. Higher levels of residual nitrite
were detected in the samples with a lower amount of meat, compared to those with a higher amount of meat.
CONCLUSION
In the current study, the residual nitrite, ascorbic acid, and nitrosamine contents of seven most popular Iranian processed meat products, namely sausages with different amounts of meat were evaluated to monitor the safety status of the meat industry. The samples contained various concentrations of nitrite and nitrosamine, which were above the permitted standard level. Several factors were found to affect the residual nitrite and nitrosamine contents, the meat content being a significant variable. Nitrite interacted with heme-containing components, non-heme proteins, and fat tissues, thus conversed to nitrate and nitrosamine. Therefore, the contents of residual nitrite and, consequently, nitrosamine in products with lower meat content were significantly higher. A longer cooking time also decreased residual nitrite and nitrosamine concentration.
Further research is needed to identify new substances that could replace nitrites, as well as factors that reduce the required amount of nitrite in meat products.
CONTRIBUTION
The authors were equally involved in writing the manuscript and are equally responsible for plagiarism.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interest regarding the publication of this article.
ACKNOWLEDGEMENTS
We would like to thank National Nutrition and Food Technology Research Institute for the financial support.
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ORCID IDs
Khadijeh Abhari https://orcid.org/0000-0001-9241-3563 Zahra Pilevar https://orcid.org/0000-0001-7360-0478 Hedayat Hosseini https://orcid.org/0000-0001-8301-4229
