Study On The Controllable Process Optimization Of Low Methoxyl Pectin And Its Features Of Rheology

China is one of the most important origin of citrus fruit.In the process of citrus production and processing,it is inevitable to produce a large number of citrus peel slag.The slag skin often cannot be effectively used,and the majority are discarded or buried directly,which result in the problems of environmental pollution and resources waste.Thus this problem has become a research focus which need to be solved eagerly.Additionally,pectin has emerged more and more in food,cosmetics even in medicines,because of its good emulsion stability and gel property.Above all,low methoxyl pectin which is the most popular pectin in the market,basically rely on import,thus the cost is high.As the market increase rapidly in china,low methoxyl pectin production using citrus peel has become an important research topic.Research has shown that high methoxyl pectin can be extracted using water,acid and alkali.However,low methoxyl pectin,often need a degreasing reaction after extracting the high methoxyl pectin.Common methods of degreasing reaction for pectin mainly include alkaline,enzymatic and amidation.Among that,alkaline method is one of the most commonly used method.Alkaline method has been made a very in-depth research,improving the biggest drawback of alkaline degreasing reaction,beta elimination reaction,and ensure the completeness of pectin galacturonic acid main chain.Alkaline hydrolysis in the process of alkaline degreasing reaction will change the pH of the environment,and intermediate cannot be promptly oxidated.Thus pectin yield is limited,and methoxylification degree is uncontrolled,so pectin quality is not assured.This study selected commercial high methoxyl pectin as raw materials,using alkaline buffer?disodium hydrogen phosphate?to provide alkaline environment.Then studying the relation between each parameter of the alkaline buffer and the methoxylification degree of the pectin,this research carried out the controllability of pectin methoxylification degree.And the quality and structure of low methoxyl pectin gel were analyzed using texture analyzer and rheological method,to explore the impact of various factors on the gel.We hope that this study can provide solid data to support the research of producing high quality low methoxyl pectin from citrus peel.The following conclusions was obtained through the study,:1 The influence of the amount of pectin,pH value and the amount of hydrogen peroxide evaluations on the methoxylification degree was in the order: p H value > the amount of hydrogen peroxide > the amount of pectin;When the amount of pectin was 3.3 g,11.40 mM for the amount of hydrogen peroxide,pectin methoxylification degree of was the lowest;When the pH value is higher than 8.00,pectin methoxylification degree is less than 50%,namely it is low methoxyl pectin.2 The influence of alkaline hydrolysis time,oxidation time,alkali solution temperature and oxidation temperature on the methoxylification degree was in the order: alkaline hydrolysis temperature > time > temperature > alkali solution oxide oxidation time.When the goal of the methoxylification degree was 36.12%,the best condition is alkali solution for 40 min,oxidation time for 40 min,oxidation temperature 60?,alkaline hydrolysis temperature 60 ?.3 The viscosity of pectin solution was increased with the concentration of sucrose,pectin,NaCl and Ca²⁺.Among that,the concentration of Ca²⁺ is the most significant impact,followed by the concentration of pectin and NaCl,and the concentration of sucrose had little influence on viscosity of pectin solution;Pectin viscosity decreased with the increase of temperature;The "Bent" change of pectin viscosity appeared along with the change of pH.When the pH value was 4 or 9,the viscosity was the highest and when the pH value was 7,the viscosity was the lowest.4 In the preparation of low methoxyl pectin,the influence of Ca²⁺ concentration on the texture properties of gel is the most significant.When the concentration of low methoxyl pectin was1.5%,the pH value was 4,and the Ca²⁺ concentration was 30 mg/g,namely pectin and Ca²⁺ concentration ratio was 0.05,the gel strength was the greatest and the adhesiveness,chewiness and resilience was best;The influence of the sucrose concentration on pectin gel was not obvious.5 The new method makes the gel structure of low methoxyl pectin under the optimum gel condition,which is superior to the gels formed by the commercial low methoxyl pectin and the low methoxyl amidated pectin.The alkaline environment is more mild,and the ratio of pectin concentration to Ca²⁺ is greater.The amount of pH and Ca²⁺ concentration which are needed to form a gel are wider.Due to the mild preparation of the new law,the reaction of ?-elimination was suppressed,and the integrity of the pectin molecular chain was guaranteed.The average molecular weight of pectin was reduced,but still in the same order of magnitude.Therefore,the viscosity is slightly higher than that of low methoxyl pectin prepared by conventional alkali method.Based on the above two points,this method is feasible and superior to the traditional alkaline.The esterification of low ester pectin is controlled.Low methoxyl pectin colloidal gel system is closed and plays good toughness,it can be effectively used in food processing.