The Effect Of L-ascorbyl Palmitate On The Fats Crystalline Network: Mechanism And Application

Plastic fats are widely applied in fat-structured food for their excellent mechanical properties and functionality,such as margarine,ice cream,chocolate,etc.The crystalline smallmolecule emulsifiers could act as functional additives to modify and structure the crystalline network due to their amphiphilic behavior,fat-like crystallization properties,safety,and wide availability.On the one hand,emulsifiers can participate the crystallization process and affect the crystallization behavior of triglycerides(TAGs)in traditional plastic fats,thereby improving the crystalline network.On the other hand,emulsifiers can be evaluated as organogelators to create the crystalline network and create new plastic fats.L-ascorbyl palmitate(L-AP)is a chemical compound of the hydrophilic ascorbic acid and the hydrophobic palmitic acid through ester bonds.The amphiphilic structure suggestes that L-AP has the surface active.In this study,the effect of L-AP on the crystallization behavior of soild fats and the structural characteristics of organogels prepared by L-AP were systematically explored.In addition,their corresponding bread performance was also carried out for a better understanding of the potential baking applications.The main contents and conclusions are as follows:First of all,the effect of L-AP on the crystallization behavior of palm oil(PO)and coconut oil(CO)were studied using pulsed nuclear magnetic resonance(p-NMR),X-ray scattering(XRD),differential scanning calorimetry(DSC)and polarized light microscopy(PLM).Crystallization kinetics analysis indicated that L-AP accelerated the crystallization process,showing higher crystallization rate and shorter induction time.Onset/peak temperature and enthalpies of both crystallization and melting process increased after adding 1%,3%and 5%L-AP,also suggesting that L-AP promoted the crystallization of PO and CO.L-AP participated in the crystallization process,which led to higher content of??polymorph in PO.In addition,the presence of L-AP increased the thickness of the nanoscale crystal in CO but decreased that in PO.The sub-microstructure of the crystals determines the microstructure.The presence of L-AP led to the smaller,finer and denser crystals of PO and CO with more ordered microstructures(higher D_b).Secondly,the macro-micro structural characteristics and intermolecular forces of the crystalline network prepared with L-AP in high oleic sunflower oil(HOSO)/peanut oil(PNO)were systematically investigated by rheological measurements,polarized light microscope(PLM)analysis,X-ray diffraction(XRD)and Fourier Transform Infrared Spectroscopy(FTIR)detections.Rheological measurements demonstrated that all organogels presented a solid-like behavior(G'>G'')with excellent structure-recovery property and thermal stability.Numbers of needle-like crystal morphology was observed in all samples from PLM.Higher concentration of L-AP resulted in a denser and more complex crystalline network,which improved the mechanical strength(higher G')and the oil binding capacity(lower oil loss).Moreover,XRD and FTIR results indicated that L-AP formed the crystalline network through hydrogen bonding interactions and trapped oil droplets during gelation process.Higher concentration of L-AP provided more numbers of-OH groups to create H-bonds,and thus formed stronger crystalline network(higher G').Finally,those fats were applied in bread to evaluate their structure characteristics and aging process.Overall,more desirable structural characteristics were obtained in bread prepared with solid oil(shortening,PO,PO and L-AP mixturse,CO,CO and L-AP mixture,organogels),suggesting that organogels based on L-AP had great potential to replace shortening.In addition,L-AP had positive effect on the structure characteristics of wheat flour bread,such as specific volume,cell density and cell average area.Besides,L-AP reduced the aging rate of bread,thereby improved the shelf life through reducing water migration and polymer reorganization.