On January 8, 2013, CCTV CCTV news broadcasted a report on the undercover secrets of the fake shark fins. It revealed that many shark fins sold in the hotel are made of gelatin. These so-called shark fins are only made with shark fin. "Modulated."
As one of the traditional Chinese ingredients, shark fin is widely accepted by East Asian countries. Shark fins are made from the fins of sharks. The organic components are mainly composed of various proteins such as cartilage mucin, collagen and cartilage. The shark fin cartilage contains more collagen, and the dry product contains up to 83.5% protein, but lacks tryptophan, which is an incomplete protein. In the cooking, the shark's fin must be added with ingredients to impart flavor. Generally, poultry meat, shrimp, crab, etc. all contain more tryptophan. Matching with shark fins not only gives a delicious taste, but also compensates for the lack of tryptophan.
The shark fins are expensive, and some black-hearted merchants stare at the high profit margins and play a black abacus, so that the shark fins in the feast of the feast are also shot. According to the survey, the synthetic shark fins on the domestic market are mainly synthesized with gelatin, sodium alginate and a little calcium chloride, and their nutritional value is zero. Many fake shark fins are also artificially added with chondroitin sulfate to confuse the taste when eating, making it difficult to distinguish between authenticity and authenticity. In order to verify the taste difference between true and false shark fins, Zhejiang Consumer Protection Committee and a hotel in Hangzhou completed a shark fin consumption experiment. The experimental results show that after adding the broth, the synthetic shark fin and the real shark fin not only have not many taste differences, but also the shape is difficult to identify.
In fact, the true and false shark fins can be distinguished. The most authoritative method is to detect shark source DNA in shark fin. RephiLe's technicians searched the relevant literature and compiled the DNA detection method for shark fin sharks for reference. Methods as below:
Sample DNA extraction
0.1 g of shark fin was ground into a powder, and sample DNA was extracted using an animal genomic DNA extraction kit, and the DNA concentration was measured with a nucleic acid content meter and stored at -20 °C.
2. PCR amplification
A nested PCR reaction was employed.
First round of PCR:
1×PCR buffer, Mg 2+ , 2.5 mmol/L; taq enzyme, 1 U; dNTPs, 200 μmol/L; primers (5'-TCTGCCCTATCAACTTTCGATGGTA-3' and 5'-AATTTGCGCGCCTGCTGCCTTCCTT-3'), 100 nmol/L; DNA template 50-100 ng; reaction system 25 μL.
Reaction conditions: denaturation at 94 ° C for 3 min; 94 ° C for 20 s, 54 ° C for 40 s, 72 ° C for 40 s, 40 cycles.
Second round of PCR:
12.5 μL SYBR Green Pre Mix, 1 μL Primer 1 (5'-CACCTTTAGGCAAACCAGCAC-3') (5 μM), 1 μL Primer 2 (5'-GGGCCAGGGTCGAATCTCT -3') (5 μM), 8.5 μL sterile ultrapure water, 2 μL DNA template The reaction system was 25 μL.
Reaction conditions: denaturation at 95 ° C for 10 min; 95 ° C for 30 s, 64 ° C for 40 s, 72 ° C for 45 s, 35 cycles. 95 ° C 15 s, 64 ° C 30 s, 99 ° C, 15 s.
3. PCR result detection
The PCR product was detected by agarose gel electrophoresis, and the product of the real shark fin appeared at a position of 180 bp.
Figure 1 Shark DNA specific detection electropherogram
Note: M is DL2000, 1 is a positive control, 2 is a negative control, 3 is a shark fin sample, and 4 is a blank control.
The PCR method is also applicable to Realtime PCR, which can better determine the content of shark-derived DNA.
4. Analysis of results
If the corresponding band does not appear at 180 bp, it is considered a negative result, ie shark fin-free DNA is not contained in shark fin.
To prevent or false negative results, we specifically added controls to the samples. If a negative result still occurs, it is recommended to re-extract the DNA and PCR amplification of the sample.
In particular, there are many places in life science experiments that require the use of pure water. In the nucleic acid extraction process, it is necessary to use pyrogen-free sterile ultrapure water to prevent nuclease degradation of nucleic acids and microbial metabolites from contamination. The laboratory's secondary pure water is well suited to the buffer requirements. At the same time, PCR requires very strict water. Metal ions such as Fe, Cd, and Zn in water interfere with enzymes. Organic molecules associate with DNA or with Mg 2+ to affect reactions. The effects of bacteria and pyrogens should also be avoided. . The most important requirement for water for electrophoresis is the removal of biologically active substances such as endotoxin (usually less than 0.005 IU/ml), ribonuclease and protease (not measurable); preferably with a resistivity of 18.2 MΩ·cm and a TOC of less than 10 ppb, super Filtration and ultrapure water with a bacterial content of less than 1 CFU/ml are used as water supply.
RephiLe specially recommends Direct-Pure EDI + PURIST UV combined pure water treatment system, which can provide both secondary pure water and ultra-pure water to meet the water needs of life science laboratory. The Direct-Pure EDI secondary pure water system uses Siemens's EDI, which uses tap water as the influent water to provide stable and high-quality high-purity water, and the products have reached the advanced level of similar products. The PURIST series ultra-pure water system with simple design uses pure water as the influent water to produce ultra-pure water. The water quality exceeds or meets the GB and ASTM, CAP, CLSI first-grade water standards. The terminal is equipped with an ultrafilter that can control bacteria < 0.1 cfu/ml and pyrogen < 0.001 Eu/ml to meet the special requirements of life sciences. The combination package can ensure users have no worries about using water in use, so that users can enjoy professional and thoughtful service while using high quality products. In addition, RephiLe can also provide Direct-Pure UP ultra-pure water plus RO water machine, the pure water meter uses tap water as the inlet water, and prepare reverse osmosis RO water and high-quality ultra-pure water, one machine and two waters for The choice of customers with different needs.
Shark fins represent luxury in Chinese food culture. The use of shark fins to treat guests symbolizes identity and status. As everyone knows, sharks are large at the top of the food chain, and the heavy metal element, mercury, is enriched in the body. The survey report released by Wild Rescue shows that the shark fin soup contains high concentration of mercury, and the shark fin is contaminated by mercury up to 70%. The ratio of mercury contained in the body is shocking, which is 42 times higher than the normal allowable content! Due to human overfishing, scientists point out that at least 17% of known shark species are on the verge of extinction. For our own safety, and to protect wild marine animals and maintain the integrity of the marine food chain, Rephile reminds users to respond positively to the call of environmental organizations to resist shark fins and make a contribution to protecting the environment!
There is no killing without buying or selling!
RephiLe wishes the users no worries! Health and worry-free!
For more purification and analysis products, please visit RephiLe's official website:
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