Stability And Crystallization Characteristics Of Diacylglycerol Based Water-in-oil Emulsions

Diacylglycerol(DAG)is a well-recognized new food material.Its unique molecular structure gives DAG emulsification and antistatic properties.It also has the advantages of safety,nutrition and good processing.It regulates blood lipids,inhibits weight gain and relieves.It plays an important role in diabetes,preventing arteriosclerosis and reducing intestinal burden,and is therefore widely used as a substitute for functional oils.In this paper,the molecular distillation residue(MDR)from the production process of monoglyceride(MAG)were used to prepare,purify and characterize medium-and long-chain diglycerides(M/LCD).Long chain diglyceride(LCD)was obtained by molecular distillation MDR,the stability and crystallization mechanism of 53.46% LCD and 50.773% M/LCD-stabilized W/O emulsion were explored,and the effect of water content on the rheological properties of LCD-stabilized W/O emulsions was studied.The main findings are as follows:(1)Preparation,purification and characterization of M/LCD by enzymatic catalysis of heavy phase products from industrial molecular distillation monoglyceride and octanoic acid.Suitable preparation conditions were: reaction temperature was 65 ?,substrate molar ratio was6:4,reaction time was 6 h,enzyme amount was 15 wt%.Under these conditions,the octanoic acid insertion rate was 15.35%,and the DAG content was 50.73% in the crude M/LCD that processed after chemical acid removal.Silica gel was used as adsorbent and n-hexane-diethyl ether-formic acid(volume ratio: 45:25:1)was used as eluent,the crude M/LCD sample was purified by column chromatography to obtain with DAG content of 88.24%.The M/LCD,was mainly 1,3-DAG,the crystal form was ? and ?' coexist,and the melting point was 60.34 ?,which had higher melting point and stronger solid characteristics than M/LCG.(2)W/O emulsion with LCD,M/LCD-rich solid fat were prepared.The properties effected by the emulsifiers addition of polyglycerol polyricinoleate(PGPR),glycerol monooleate(GMO)and glycerol monostearate(GMS)were measured.The results showed that the addition of PGPR,GMO and GMS reduced the contact angle,melting peak and crystallization peak temperature of LCD and M/LCD.The LCD and the M/LCD stabilized emulsions showed interface crystallization and network crystallization that the Pickering stability and network stability coexist in the emulsions.GMO and GMS didn't change the stability forms,but PGPR made the interfacial crystallization of the emulsion inconspicuous.The emulsions prepared by LCD were more stable than the emulsions prepared by M/LCD.The addition of PGPR had no significant effect on the emulsion stability prepared with LCD and M/LCD,but the addition of GMO and GMS significantly reduced the emulsion stability prepared with M/LCD.(3)The emulsions prepared with the emulsifiers of LCD,PGPR and PGPR-LCD were investigated.The stability and related physical and chemical properties(microstructure,particle size,hardness,solid fat content,fat polymorphism and rheological properties)of the emulsions were determined to investigate the stability mechanism of LCD on W/O emulsions.The results showed that LCD promoted the Hydrogenated palm oil(HPO)to crystallize at the oil-water interface and form the Pickering stabilized emulsions,enhancing the SFC,hardness and viscoelasticity of the emulsion,and the crystallization temperature of the HPO were increased in the emulsion to improve the stability of emulsions.The emulsion of PGPR mainly enhanced the stability of the emulsion in the form of network stability.LCD and PGPR had synergistic effects in the HPO-stabilized W/O emulsion,so the emulsion stabilized with PGPR-LCD was more stable than the emulsions stabilized with DAG and PGPR alone.(4)Suitable cooling methods for preparing W/O emulsions with different water content(10-40 wt%)were: cooling in ice water bath,cooling with mechanical electric mixer stirring,cooling for 20 min.And the HPO addition was preferred for 10 wt%,emulsifier addition amount was preferred for 3 wt%.It was found by polarized light microscopy that HPO formed network crystallization,LCD and GMS could form interfacial crystallization,which could promote the dispersion of water droplets into active filler,and the viscoelasticity of emulsion increased with the increase of water content(10-40 wt%).