Study On The Preparation Of Lipophilized Lotus Oligomeric Proanthocyanidins And Its Antioxidation In Oils

At present the most common way to effectively prevent oils from oxidative rancidity in food is adding antioxidants,and synthetic lipophilized antioxidants are widely used in food industry such as BHA,BHT and TBHQ.But in recent years,synthetic antioxidants are limited to use because studies have shown that they have direct or indirect effects of carcinogenesis and teratogenesis.Therefore,as people pay increasingly attention to food safety and health,development and application of natural antioxidants have become the new direction of food science.A variety of lipophilized natural food antioxidants also comes into being.Lotus oligomeric proanthocyanidins(LSOPC)has good antioxidant activity,but its hydrophilicity based on numerous phenolic hydroxyls limits its application in oil system.Inspired by the relevant studies of chemical modification on natural antioxidants such as tea polyphenols,catechins and EGCG,LSOPC was modified by stearoyl chlorid in order to increase antioxidation in oils.Lipophilized LSOPC was prepared by connecting with nonpolar fatty acid chains.The preparation technique and optimal conditions were optimized by single-factor experiments and orthogonal experiment.Preliminary molecular characterize of modified LSOPC was investigated and its chemical properties such as lipid solubility,antioxidant activity and stability were also analyzed.Add Lipophilized LSOPC in the rapeseed oil to inspect its effects on the physical and chemical properties of oil oxidation,and other types of synthetic or natural antioxidants were compared.At last the modified products'antioxidant application in cooling pork were studied.The results will provide technical support for LSOPC's development and application in the oil.Through the researches above,the main results were as follows:1.The optimization of preparation process and condition about lipophilized LSOPC:take LSOPC dissolved in a certain amount of ethyl acetate,in turn,add the target quantity of basic catalyst Na HCO₃and stearoyl chloride dropwise.Under the protection of nitrogen,we get neutral reddish brown liquid by filtering and water washing after the oscillating reaction in 40?water for 7 h.Finally modified LSOPC received by removing ethyl acetate with the helping of the rotary evaporation apparatus.Through single-factor experiments and orthogonal experiment,in addition,take the POV of overheated rapeseed oil added LSOPCm as evaluation index,the optimal reaction conditions are obtained.The catalyst amount has significant effect in preparation of LSOPCm.Under optimal conditions the POV of overheated rapeseed oil was 31.6%lower than that of control group(added with LSOPC).It proves that the antioxidant activity of modified LSOPC is better than LSOPC's.2.The property analysis and structure characterization of lipophilized LSOPC:the infrared spectrogram of LSOPC and LSOPCm shows that esterification between LSOPC and stearoyl chloride reacts partly.In comparison with LSOPC,the total phenol content of modified LSOPC was reduced and IC₅₀of scavenging DPPH is increased double,but LSOPCm still maintains strong activity of scavenging free radicals.These indicators will reflect the degree of esterification indirectly.At the macro level,Log P of modified LSOPC increased obviously,it means the purpose of modification reached.Especially in the long-term storag of rapeseed oil,antioxidant effect of LSOPCm was stronger than other kinds of antioxidants such as VC?VE?BHT.Modification of LSOPC can receive the aim to improve the solubility and antioxidant activity in oils.3.The stability study of lipophilized LSOPC in different solution environment:Using the UV-Vis Spectroscopy,the stability were investigated qualitativly.Results showed that high concentrations of acidic and alkaline environment,oxidant like H₂O₂,acid radical ion such as CO₃^2-?HCO₃^-,and high cation Fe²⁺?Fe³⁺?Al³⁺has obvious damage to the LSOPCm.While the solution includes low concentration acid,low concentration of reducing agent and other anion and cation like Cl^-?SO₄^2-?NO₃^-?Na⁺?K⁺?Mg²⁺?Ca²⁺,LSOPCm can keep good basic stability and the structure will not change.4.The application research of lipophilized LSOPC to keep the cooling pork fresh:while cooling pork store at 0 to 4?,the SAP exudation rate,acid value and TBA value with LSOPCm treatment significantly reduced compared with LSOPC treatment.Using chromaticity to evaluate freshness of cooling pork,the results show that the modified LSOPC can effectively inhibit lipid oxidation of pork and it is advantageous to the cooling pork's quality maintaining in the process of storage.