| High acyl gellan gum(HA)is a kind of microbial polysaccharide produced by Sphingomonas elodea under aerobic conditions.HA is usually used as thickener and stabilizer in food industry with its excellent comprehensive property.At present,the emulsifying capacity of natural macromolecular emulsifiers has been widely studied and applied.As a stable transport system,emulsion system can significantly improve the solubility and stability of some bioactive substances,such as ?-carotene.The high electrostatic repulsion and viscosity of HA showed its potential as an emulsifier/stabilizer.In this paper,the emulsification effect of ultrasonic emulsification(UE)and high pressure homogeneous emulsification(HE),as well as the emulsification properties of HA,low acyl gellan gum(LA)and gum arabic(GA)were compared by measuring the mean particle size,particle size distribution and interfacial tension in O/W emulsion.Additionally,the P-carotene emulsion with HA as emulsifier was prepared by UE method,and the preparation technology was optimized by Response Surface Medology.A further evaluation of the emulsion stability of HA-?-carotene emulsion system was carried out.On this basis,the property of digestion and bioavailability of ?-carotene emulsion in vitro were analyzed.The results of this study are aimed at providing theoretical guidance for the research and development of HA-?-carotene emulsion,processing improvement,the effective use of?-carotene.The development of comprehensive function of HA and its application in food industry are also significant purpose.The main research results are as follows:The properties of average particle size,particle size distribution,and ?-potential of HA emulsion obtained by UE and HE methods were compared.The average particle size of UE emulsion and HE emulsion with HA concentration of 0.175%were 5.381±0.04?m and 5.146±0.07?m.The absolute value of ?-potential and particle size distribution of UE emulsion were also close to the results of HE emulsion.The emulsification characteristics and stability of three kinds of hydrocolloids were studied by analysing of ?-potential analysis,average particle size and particle size distribution analysis,and interfacial tension measurement.The results showed that the average size of emulsion prepared by HA was slightly larger than GA,and the size of LA was large,which did not have good emulsifying activity.The absolute value of HA emulsion ?-potential was significantly higher than GA emulsion(p<0.05),and the interfacial tension of the emulsion was lower than GA emulsion in the optimal concentration.Therefore,the stability of HA emulsion was superior to GA emulsion,and the stability of LA emulsion was poor.After the emulsion was stored for 20 days,the HA emulsion was only stratified at the HA concentration of 0.050%and 0.100%.When GA concentration was range from 1.0%to 15.0%,all the samples of emulsion were stratified at different degrees,and the particle size change rate of HA emulsion was significantly lower than GA emulsion.It is determined that HA had good emulsifying properties,and using HA as an emulsifier can prepare O/W emulsion with lower additive amount(HA:0.175%,GA:15.0%)and better stability than GA.The ?-carotene emulsion system using UE process with HA as emulsifier was systematically studied.The stability and stabilizing mechanism of the emulsion under different conditions of heat treatment,pH and sodium concentration was investigated by analysing of Zeta potential analysis,average particle size,emulsion yield measurement,dynamic stability analysis and colorrate measurement.At the same time,the processing of HA-P-carotene emulsion by UE method was optimized,and the preparation conditions were determined as follows:ultrasonic time was 7.66 min,ultrasonic power was 513W,The concentration of oil phase was 12.0%,and HA concentration was 0.179%.Further investigation was conducted on the effects of HA-?-carotene emulsion system on the bioavailability of P-carotene in vitro.The results showed that The average particle size of the emulsion at each HA concentration and the change of ?-potential were all within 2.5?m and 3.0mV,while after entering the simulated intestinal phase,and the ?-carotene was released from oil droplet and formed micelles with bile salts and phospholipids.The release rate of free fatty acid(FFA)can be increased by HA-?-carotene emulsion.In the control group,the bioavailability rate of P-carotene was only 4.13±0.01%and 26.63±1.31%of HA-?-carotene emulsion,indicating that HA-?-carotene emulsion system can effectively improve the bioavailability rate.Meanwhile,UE technology can improve the bioavailability of ?-carotene observably(p<0.05)compared with the results of bioavailability of HA-P-carotene emulsion prepared by HE method. |
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