| N-nitrosamines are potential harmful substance to human health and often present in foods. They can induce tumors in various experimental animal species. Some epidemiological data suggest that humans are susceptible to carcinogenesis by N-nitrosamines and that the presence of these compounds in some foods may be regarded as an aetiological risk factor for certain human cancers including cancers of the oesophagus, stomach and nasopharynx. Therefore, more efforts have been made to investigate meat products for N-nitrosamines because meat products are one of the most important components in human foods. N-nitrosamines are mainly formed during cooking, processing and storage. In vivo gastric acid, nitrification can also occur and formate the endogenous N-nitrosamines.Traditional Chinese sausage is a dry-cured sausage loved by consumers because of its special flavor. There was little information about the volatile N-nitrosamines in traditional Chinese sausage. So the objective of this study was to investigate the formation and control of volatile N-nitrosamines in traditional Chinese sausage and simulated gastric acid system.Firstly, the effects of cooking methods on volatile N-nitrosamine were studied in traditional Chinese sausage. Secondly, plant polyphenols were studied on the changes of volatile N-nitrosamine in traditional Chinese sausage during ripening. Finally, in simulated gastric acid system, polyphenols were studied on the formation of N-nitrosamines. The mechanism of plant polyphenols on N-nitrosamine formation was also analyzed. The detailed contents and results are shown as follows:1 Investigation on the volatile N-nitrosamine in traditional Chinese sausageFirst, a method of water vapor distillation, gas chromatography-mass spectrometry detection was established to determine nine volatile N-nitrosamines in meat products. The standard solutions were range from 0.1 to 10μg/mL. The quantitative detection limits were between 0.05 and 0.2 μg/kg. Recoveries were found to between 62% and 78%. Twelve Chinese sausage samples were obtained from Nanjing market.The results showed that NDMA, NDEA, NPYR were the three major types of volatile N-nitrosamine in sausages. The total N-nitrosamines were about 0.55-18.06 μg/kg and most samples were less than 10 μg/kg. The average N-nitrosamines were 8.40 and 3.63 μg/kg in traditional natural fermented Chinese Sausage and industrialized production Chinese sausage, respectively. The residual nitrites were less than 30 mg/kg in all sausages.2 The effects of cooking treatments on N-nitrosamines formation in traditional Chinese sausageThe aim of this study was to determine the influence of four different cooking methods (boiling, pan-frying, deep-frying and microwave) on the contents of volatile N-nitrosamines. The results showed that only NDMA, NDEA and NPYR were found in the traditional Chinese sausage. Total N-nitrosamines contents were about 5-7 ug/kg. Frying treatments significently increased the N-nitrosamines contents (P< 0.05). Boiling and microwave treatments had no significant effect on the content of N-nitrosamines.All cooking treatments decreased the contents of biogenic amines and residual nitrites (P<0.05). The total biogenic amines contents were declined from 52 mg/kg to 40-47 mg/kg, nitrite content were declined 2-3 mg/kg. Cadaverine and histamine may be precursors of N-nitrosamines. Boiling and microwave treatment, compared with frying, were found to be more effective methods for reducing these potential carcinogenic substances.3. The effects of plant polyphenols on N-nitrosamine formation in traditional Chinese sausageEffect of plant polyphenols (tea polyphenols, grape seed polyphenols and sodium ascorbate) on the N-nitrosamines formation in traditional Chinese sausage were investigated during the 28 days ripening period. The result showed that the pH value declined and then increased to 6.3. The aerobic plate count increased to 7 log(cfu/g). Moisture content and water activity were decreased during ripening period. The TBARS values increased and residual nitrites decreased rapidly during ripening period. Total biogenic amine contents increased to 260 mg/kg. Only NDMA, NDEA and NPYR were found in the traditional Chinese sausage. Total N-nitrosamines contents increased to 8 μg/kg. Correlation analysis showed that there was a significant negative correlation between N-nitrosamine and residue of nitrite, moisture content, water activity (P< 0.01). There was a significant positive correlation between nitrosamine and cadaverine, histamine, tyramine, spermidine (P< 0.01).There have no significant effect of plant polyphenols on moisture content, water activity, pH and the aerobic plate count in traditional Chinese sausage during processing. The TBARS values were lower in plant polyphenols, tea polyphenol had the significant effect to decrease the TBARS (P< 0.05). The residual nitrites were lower in plant polyphenols, vitamin C had the significant effect to decrease the nitrite (P< 0.05). Vitamin C and tea polyphenols decreased the contents of cadaverine, tyramine and total biogenic amines (P<0.05). Compared with the control, the additive vitamin C, tea polyphenols and grape seed polyphenols reduced N-nitrosamine content. It was concluded that plant extracts, in combination nitrite was more effective in maintaining the quality and safety of these traditional Chinese sausage, as indicated by lower TBARS, lower residual nitrites and reduced N-nitrosamines values.4 The effect of plant polyphenols on N-nitrosamine formation in stimaluted gastric acid systemIn simulated gastric acid system, tea polyphenols and grape seed polypheonls on nitrite scavenging and N-nitrosamine formation were determined, and their antioxidant activity was assessed by DPPH, ABTS and FRAP assay. The results showed that tea polyphenols, grape seed polypheonls and VC could scavenge nitrite to different extents, tea polyphenol had the higher scavenging rate. With the increasing of polyphenols concentrion, the antioxidant capacity increased gradually. The IC50 of the tea polyphenols, grape seed polypheonls and VC on DPPH radicals were 0.19,0.52 and 0.76mg/mL respectively, the IC50 on ABTS radicals were 1.21,1.82 and 3.20 mg/mL, respectively. The FRAP iron reduction in turn was tea polyphenols> VC> grape seed polyphenols.In simulated gastric acid system, with the increase of tea polyphenols and grape seed polyphenols, the content of NDEA was increased. When the content of NDEA reached a relative high level, then the content of NDEA was declined, finally the NDEA formation was inhibited completely. So polyphenols had the dual effect of facilitation and inhibition on NDEA formation, but VC only inhibited the N-nitrosamine formation.5 The effect of phenolic compounds on N-nitrosamine formation in simulated gastric acid systemIn simulated gastric acid system, phenolic compounds were found to be potent scavenger and the four most potent ones were EGCG (Epigallocatechin gallate), EGC (Epigallocatechin), pyrogallol and gallic acid. The nitrite scavenging effect was increased when the content of phenolic compounds increased.The radical scavenging activity of the different classes of the tested flavonoids decreased in the following order:flavanols> flavonols> flavones> isoflavones. There was a highly significant positive correlation between nitrite scavenging ability and antioxidant capacity of polyphenols. This study confirmed that the number and position of hydroxyl groups largely determined radical scavenging activity of the tested phenolic compounds. The ortho-dihydroxy structure in B ring was the most important structural feature of high activity for all tested phenolic compounds. The scavenging effect was bigger when there was more hydroxyl in phenol.3-OH in C ring groups and 5,7-OH in A ring are essential for effective free radical scavenging activity.In simulated gastric acid system, polyphenols componds on N-nitrosamine formation were determined. EC (Epicatechin), ECG (Epicatechin gallate), EGC, EGCG,procyanidin B2, quercetin, resorcinol and phloroglucinol had the dual effect of facilitation and inhibition on NDEA formation. With the increase of polyphenols, the content of NDEA was increased. When the content of NDEA reached a relative high level, then the content of NDEA was declined, finally the NDEA formation was inhibited completely. Chlorogenic acid, caffeic acid, gallic acid and phenolic acids only inhibited the formation of NDEA. This study analyzed that A ring resorcinol structure compounds had the role of promoting and inhibiting the formation of NDEA. |
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