Study On The Construction And Application Of Edible Polymer Based Oleogels

A new strategy to produce solid fats containing zero trans and low saturated fatty acids in order to substitute traditional fat is to produce supramolecular oleogel by vegetable oil.Common organogelators studied were small molecule gelators or surfactants which are prohibited or limited by GB 2760.It is of great significance to use food polymers such as polysaccharides which have unique interface characteristics and are renewable resources to structure oil rich in unsaturated fatty acid.In this project,o/w emulsions and oleogels were produced based on the interaction of amphiphilic polysaccharide and hydrophilic polysaccharide or protein and polysaccharide.The physical properties of the oleogels were evaluated,the microstructure and the interaction force of the oleogels were investigated,and the application of the oleogels in baking products was explored.The main contents and conclusions are as follows.First of all,the construction method of the polymer-based oleogel were exploered,and different polysaccharide and protein were chosen as the oleogelator to construct the oleogel.Techniques such as polarizing microscope(PLM),rheometer and X-ray diffractometer(XRD)were used to compare the properties of the oleogels.It was found that the oleogels could be built with amphiphilic polysaccharide such as hydroxypropyl methyl cellulose(HPMC)and octylic succinic acid modified starch(OSA-MS)as the main emulsifier and polysaccharide such as xanthan gum(XG),guar gum and locust bean gum as the thickening agent,or with protein such as soybean protein and gelatin as the main emulsifier and XG as the thickening agent.However,the gel strength and oil binding capacity of the oleogels emulsified by HPMC were better than that of protein and MS,which proved that HPMC has the advantage over protein and MS to construct polymer oleogels.In addition,for HPMC oleogels,stronger mechanical strength of emulsions suggested more tightness networks of soft solids,stronger gel strength,and better oil binding capacity of the oleogels.The oleogels produced showed time-dependent and structure-recovery behavior,and were stable in a wide range of temperature(5~80°C).Secondly,the effects of concentration of the main emulsifier such as HPMC and gelatin,and the influences of molecular weight of HPMC and methyl cellulose(MC)on macro properties and microstructure of the polymer based oleogel were evaluated.Polarizing light microscope(PLM)as well as scanning electron microscope(SEM)was used to gain information on the microstructure of the samples.Oil loss of the oleogel was measured to evaluate their oil binding capacity,and rheological behaviors of the emulsions and oleogels were tested for their gel strength.It was found macro-properties of the samples were linked to their microstructure characteristic.Higher concentration of HPMC(1.0 wt%)resulted in more stable emulsion with higher mechanical strength,hard dried products with more compact network,and oleogels with higher mechanical strength and better oil binding capacity.Oleogels stabilized by gelatin follows the same rule.For both HPMC and MC,the higher molecular weight sample resulted in a better structure with respect to emulsions,vacuum dried emulsions,and oleogels compared to the lower molecular weight sample.Compared to that of MC,the mechanical strength of HPMC stabilized vacuum dried emulsions and oleogels were harder.Thirdly,fourier transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD)were used to evaluate intermolecular forces between the polysaccharides or proteins in the oleogels,and the gel mechanism of polymer based oleogels were investigated.It was found that the oleogel was a kind of physical gel,and intramolecular or intermolecular hydrogen bonding presented in the oleogels came from the polysaccharides or proteins contributed to the formation of the relatively orderly structure of the oleogels,which was similar to the semi-crystalline structure with liquid oil bound to it.The oxidation stability of the oleogels during storage were evaluated and the influence of different drying techniques on it was also investigated.It was found that the acid value(AV),peroxide value(PV)and anisidine value(p-AV)all increased with the increasing time,but all lied in the range of the limit for acceptance of vegetable oils.During the storage,no obvious effect of the drying process on the secondary oxidation was happened.Vacuum drying has obvious advantages over oven drying.Vacuum drying would reduce the drying time(48 h to 12 h),decrease the oxidation of the oleogels and prepare the dried emulsions with better structure.Finally,the oleogel produced by HPMC and XG was applied in the pound cakes and cookies in order to substitute the conventional solid fats.The properties including fatty acid composition,sensory properties and physical properties of the batter and the bakery products produced by the oleogel,soybean oil,margarine and shortening were compared,respectively.It was found that the polymer oleogel has the potential to replace margarine or shortening used in bakery products such as cakes and cookies.The bakery products produced by the oleogel contained low content of saturated fatty acids(17.44%)and no trans fatty acids.The hardness of the cakes and the initial hardness of the cookies produced by the oleogel could achieve that made by commercial shortening and margarine.There was no significant difference of the overall acceptability between the oleogel cakes and margarine or shortening cakes.The swirls on the oleogel cookies were clearer than that of other cookies.However,The ability of the oleogel to stir in and stabilize bubbles was worse than that of margarine and shortening.The storage stability of the oleogel cakes and cookies also needed to be improved.