Research On The Preparation Conditions Of Antifreezing Proteins And Antifreezing Ptides In Wheat Gluten

In nowadays,ice cream and other frozen food may cause recrystallization phenomenonbecause of temperature fluctuations in the process of condensation, freezing, transportation,storage and sales,which can affect the taste of product seriously.Antifreezing proteins(AFP), also known as ice structure proteins, which can prevent the formation of ice crystals,controlling their growth, changing the growth pattern of frozen or natural growth process ofnucleation,crystal growth rate,shape,and size of the ice crystals, which can control thephenomenon of ice crystal growth from small to big when food in the process oftemperature fluctuations of freezing-melting-refreezing.So it can suppress the generationof re-crystallization effectively.Wheat gluten is deep processing byproduct of wheat.It has a wide range of sources,and protein-rich.Compared with other raw materials of antifreezing proteins andantifreezing peptides,wheat gluten is preferred raw material. Therefore, wheat gluten as rawmaterial, exploring the preparation conditions of antifreezing proteins and antifreezingpeptides has a certain significance, and even has a broad market prospects and social andeconomic benefits.In order to research on the preparation conditions of antifreezing proteins andantifreezing ptides in wheat gluten, this study includes the following two aspects:First, wheat gluten as raw material,controlling different reaction conditions of thesingle factor experiment and orthogonal experiment to determine the optimum processconditions of the extraction of antifreezing protein and analysising its components.The results showed that: under the condition of0.07mol/L NaOH solution, thesolid-liquid ratio (gluten/alkali solution) of1:20, extraction time at3h, extractiontemperature is30℃, when the thermal hystersis activity(THA) is highest,the THA of wheatgluten is reach to0.1℃.Getting further purification from antifreezing crude protein bySephadex G-100gel filtration chromatography in optimum conditions,then THA of thepurified antifreezing protein components is measured by differential scanningcalorimetry(DSC),the results showed that:the THA of antifreezing protein is about0.1℃under optimal conditions.Observing crystal growth conditions by hot and cold microscopesystem, and bovine serum albumin as comparison, comparing observed crystals exhibitsome frost resistance.Determining the molecular weight distribution of antifreezing proteinis about43.14Ku by SDS-PAGE.Then,crude extracted antifreezing proteins as raw material, researching on the effect ofenzymatic hydrolysis time, substrate concentration, enzyme concentration, solution pH,hydrolysis temperature on the THA of antifreezing proteins of wheat gluten through single factor experiment and orthogonal experiment to determine the optimum process conditionsof the extraction of antifreezing ptides.The studies found the order of five factors effected of the THA of antifreezing proteinsof wheat gluten from strong to weak as follows: the solution pH,reactiontemperature,enzyme concentration,substrate concentration,hydrolysis time.the resultsshowed that:when hydrolysis time at2.5h,substrate concentration of9%,4%of the enzymeconcentration,substrate pH=8.0,55℃,THA of antifreezing peptides is highest.When themaximum THA of antifreezing peptides, the THA is about0.27℃, observing crystal growthconditions by the hot and cold microscope system, and bovine serum albumin as acomparison, comparing observed crystals exhibit some frost resistance.Under the optimumthermal hysteresis activity conditions to determine the antifreezing peptides by TricineSDS-PAGE molecular weight distribution is in the range of8.04Ku~50.12Ku.