Reserch On N-Nitrosamines And Biogenic Amine Formation In DRY-Cured Perch Affected By Adding Ferulic Acid And Salting With NACI Replaced By KCL

Perch is one of the most valuable fish varieties in our country. The meat of perch has the characteristics of be delicate、Low-fat and high-protein content、proper nutrition structure. The traditional curing and drying process is one of the most important way of aquatic products processing in our country and the products has a suitable and special flavor. However, most of our traditional dry-cured products have many safety problems. N-Nitrosamines are a kind of carcinogens and widely exist in many kinds of dry-cured products. Sodium chloride (NaCl) is a commonly-used ingredient in curing products. However, studies have shown that excessive NaCl intake causes high blood pressure、 cardiovascular and cerebrovascular diseases etc. At present, there is no report about relationship between partial replacement of NaCl by KCl and N-nitrosamine formation in dry-cured products. The purpose of this work was to evaluate effects of partial replacement of NaCl by KCl and addition ferulic acid on the quality of dry-cured perch. The specific research tasks and results are conclued as below:1. Optimization of extraction and detection of N-nitrosamines in dry-cured perchSeven N-nitrosamines may contained in the dry-cured perch includingNMEA, NDMA, NDEA,NDPA,NDBA, NPYR and NPIP were extracted by optimized ultrasonic extraction technology and simultaneously measured by Gas Chromatography Tandem Mass Spectrometry(GC-MS/MS). The Linear range of this method is 1.0～100 μg·L-1 with its linear correlation coefficient greater than 0.999. The detection limit of this method is 0.4～0.5μg·L-1. Recovery is 80.52%～104.53%, precision is 2.31%～8.14%. The recovery and precision meet test requirements of N-nitrosamine in dry-cured products. Applying this method to detect species and concentrations of N - nitrosamines contained in dry-cured perch, and the results show that there is one kind of N-nitrosamine detected in dry-cured perch,that is N-dimethyl nitrosamine (NDMA).2. Quality control of dry-cured perch affected by adding ferulic acid0、50、100、150 and 200 mg/kg of ferulic acid as inhibitors were added into the curing process of the perch and the effect of it on quality of dry-cured perch was studied. Results show that:adding ferulic acid significantly reduces amount of BAs, total number of colonies, amount of N-dimethyl nitrosamine (NDMA), amount of nitrite residues (NaN02) and amount of volatile basic nitrogen (TVB-N) in the case of not decreasing the sensory quality of dry-cured perch. Ferulic acid has significant inhibitory effect on histamine (HIS), putrescine (PUT), tyramine (TYR) and cadaverine (CAD), but increases SPD content. Samples without ferulic acid added have detectable NDMA after drying and samples with ferulic acid added have detectable NDMA after nine days of storage. NDMA content significantly decreased with the adding of ferulic acid increasing when concentration of added ferulic acid does not exceed 150 mg/kg. The total number of colonies in raw perch was 4.76 1gCFU · g-1. After 27 days of storage the total number of colonies of control group was 7.59 lgCFU · g-1, and 5.45 1gCFU·g-1 of group V, and was reduced by 28.20% compared to samples of control group.3. Evolution of N-nitrosamines and biogenic amine affected by salting with NaCl replaced by KC1The fish were salted with the 4 salt formulations (or salt mixtures), formulation I: 100% of NaCl (control); Ⅱ:80% NaCl,20% KC1;Ⅲ:70% NaCl,30% KC1; and Ⅳ:60% NaCl,40% KC1. The results show that salting with NaCl/KCl mixtures can lead to a significant discrepancy on physicochemical indexes、biogenic amine contents、nitrite residues and NDMA contents. There was no significant discrepancy on spermine (SPM)、 spermidine (SPD) contents but significantly reduce the contents of histamine (HIS), tyramine (TYR), cadaverine (CAD), putrescine (PUT) in dry-cured perch by partial replacement of NaCl by KC1. The using of NaCl/KCl mixtures could effectively maintain the nitrite content at a significantly higher level in dry-cured perch. Formulation II (20% KCl+80%NaCl) showed the highest nitrite content value at the end of curing. After 3 days of storage, the content of NDMA in perch salted with KCl was significantly higher than the control. The regulation published by the Ministry of Health, P.R. China limit the content of NDMA in aquatic product below 4ig/kg, NDMA contents in KCl-treated samples were about two times more than the samples treated with NaCl only. Especially for the meat treated with Formulation IV (40%KCl+60%NaCl), the NDMA level reached 8.31 ig/kg, which was more than twice as much as the meat salted with Formulation I (3.86 ig/kg), after twelve days of storage.