Study On Antibacterial Gel Based On Tilapia Fish Scale Collagen And Its Application In The Preservation Of Salmon

There are abundant freshwater fish resources in china, scales is the main by-product of aquatic products processing, most of scales are processed into fish feed or discarded directly, which is rich in collagen and has not been effectively utilized.Collagen is a bio-polymer, with low toxicity, biodegradability, low immune activity, moisture and nutrition, which is widely used in food industry, cosmetics, biomedical materials, and other areas.Tilapia has attracted the attention of the world aquaculture,and is known as one of the main sources of animal protein in the future. In this study, the tilapia fish collagen was extracted using acid, and its physical and chemical properties were studied. Meanwhile, the scale collagen gel was used as the substrate, adding the oregano essential oil, lysozyme and tea polyphenols. The application of these three natural antibacterial agents in salmon preservation was also studied. This study provide theoretical basis for the development and utilization of tilapia fish collagen and application prospect on the development of seafood storage and preservation technology. The main research contents and results are as follows:1. Basic component of tilapia fish scale was measured according to the national standard method. The moisture content is as high as 47.39%, crude protein, ash content and total calcium content is about 21.57%, 16.23% and 13.94%, respectively, fat content is the lowest, only about 0.02%. The composition is beneficial to the extraction of collagen.2. Property differences of scales collagen extracted with different time:(1) Using scanning electron microscope to observe the scales structure, the results showed that the tilapia fish scales have a complete ring shape and rich collagen fiber layer compared to the untreated scales. This indicates acid method can fully extract tilapia fish collagen.(2) Scale collagen extraction rate under different extraction time: Tilapia fish collagen was extracted by acid method, determination of collagen content through mapping hydroxyproline standard curve, then, analyze the extraction rate, which first increased and then decreased with the extraction time, the extraction rate at 48 h reached a maximum of 24.7%.(3) Using UV, fourier transform infrared(FTIR) spectroscopy, SDS-PAGE gel electrophoresis and amino acid analysis to detect the influence of different extraction time on the nature of the collagen.The results showed that: 12 h, 24 h, 48 h and 72 h extracted proteins have a UV-visible absorption peaks at about 230 nm, and in the infrared characteristic peaks have vibration absorption peak, this explains the protein extracted from tilapia scales belong to the collagen; The SDS-PAGE electrophoresis analysis showed that only 48 h extracted collagen has ?1, ?2 and ? chain,which is unique to ? type collagen, It showed that 48 h is optimum extracting time, retain the best collagen structure. Amino acid composition analysis result further confirmed that the hydroxyproline content is higher at 48 h, and the quality is better.3. Physicochemical and toxicologic studies of acid soluble fish collagen: The denaturation temperature, emulsification and emulsion stability, moisture absorption, foaming ability and foam stability and toxicity of acid soluble scale collagen(ASC)(extraction time for 48 h) were determined. The results showed that the degeneration temperature of ASC was 35.23 ?, the emulsification and emulsion stability were 48.48% and 59.89% respectively, the moisture absorption of 0.25 g/g, foaming ability and filtration rate were 185.00% and 41.00% respectively, the oral toxicity as LD50> 5000 mg/kg, according to acute toxicity grading for the actual non-toxic.4. Inhibition effects of three natural antimicrobial agents:(1) 96-well plate method was used to determine minimum inhibitory concentration(MIC) and minimum bactericidal concentration(MBC) of oregano essential oil, lysozyme and tea polyphenols against E. coli, S. aureus, L. monocytogenes and V. parahemolyticus. It was found that the MICs of oregano essential oil, lysozyme and tea polyphenols for E. coli were 2.5 ?L/m L, 6.25 mg/m L and 0.156 mg/m L, the MBCs were 2.5 ?L/m L, 25 mg/m L and 0.156 mg/m L; The MICs of S. aureus were 1.25 ?L/m L, 12.5 mg/m L and 0.156 mg/m L, the MBCs were 2.5 ?L/m L, 25 mg/m L and 0.156 mg/m L; The MICs of L. monocytogenes were 1.25 ?L/m L, 12.5 mg/m L and 0.625 mg/m L,the MBCs were 1.25 ?L/m L, 25 mg/m L and 1.25 mg/ml;The MICs of V. parahemolyticus were 0.313 ?L/m L, 25 mg/m L and 0.156 mg/m L,the MBCs were 0.313 ?L/m L, 25 mg/m L and 0.156 mg/ml?(2) The inhibition rates of ASC containing oregano essential oils, polyphenols and lysozyme on E. coli were 87.53%, 49.26% and 79.81%, respectively; the inhibition rate on S. aureus were 83.22%, 51.16% and 75.22%, respectively; the inhibition rate of L. monocytogenes were 75.00%, 58.86% and 79.08%, respectively; the inhibition rate of V. parahemolyticus were 92.43%, 41.73% and 88.24%, respectively.5. The application of scale collagen antibacterial gel in salmon preservation: Add the oregano essential oil, lysozyme and tea polyphenol in ASC. Using sensory evaluation, p H value, color value, texture value and TVB-N value, the total number of colonies and other indicators to detect salmon fresh changes during the storage. The results indicated that fish collagen based gel can delay the deterioration rate of salmon at different levels. Comprehensive indicators showed that adding oregano essential oil in fish scale collagen antibacterial gel is better compared with the other two antibacterial agents, the shelf life of salmon was extended 2 days.