| Great interest has been focused on developing functional foods that include foods or food ingredients that exert a beneficial effect on host health. Probiotic microorganisms defined as"living microorganisms, which upon ingestion in certain number exert health benefits beyond inherent basic nutrition"are progressively incorporated into functional products to affect beneficially the consumers'health by improving their intestinal microbial balance. Common microorganisms used in probiotic preparations are predominantly Lactobacillus species. Their incorporation in traditional food products has been established in the dairy industry, leading to the production of novel types of fermented milks and cheeses.A practicable method to improve the viability of probiotics is to immobilize the bacteria in an external protective matrix, which can improve their resistance to adverse conditions and facilitate better survival in specific food products. The technique of microencapsulation based on complex (w/o/w) dispersion offers several advantages for the immobilization of probiotics. It can achieve a relatively stable internal environment which can counteract harmful conditions (e.g. against oxidation); it is preferable to other preparation methods such as freezing and spray drying, because it requires relatively mild conditions such as ambient temperature and constant stirring. Thus, a stable emulsion can be formed without severely compromising the activity of the encapsulated bacteria. Moreover, this method needs relatively low cost.In this paper, the optimum growth conditions and numeration method for Lactobacillus E1 were measured. Activated diatomite was used as the absorption carrier for Lactobacillus E1 in immobilization. The immobilized Lactobacillus E1 was prepared using double emulsion strategy (w/o/w). Sodium alginate, dextrin and gelatin were used as protective solutes for the preservation of Lactobacillus E1. The influence of the protective solutes, the pH value of the internal aquatic phase and storage temperatures on the storage viability of Lactobacillus E1 were investigated. The acid resistance of the immobilized Lactobacillus E1 and the release of the immobilized Lactobacillus E1 in stimulant intestinal fluid (SIF) were also evaluated.The optimum growth temperature for Lactobacillus E1 was 37±1℃; at this temperature, Lactobacillus E1 entered early stationary phase after 36h incubation with an initial inoculation count of ~ 103cfu/g. Lactobacillus E1 was incubated under static culture contion. Cell count on MRS agar was the optimum numeration method for Lactobacillus E1.The encapsulated emulsion microparticles obtained using double emulsion strategy (w/o/w) displayed a sphere morphology consisting of a white and homogeneous gelatin membrane. Particle size distribution (PSD) of the microparticles obtained displayed a normal distribution curve. The mean particle diameter of the microparticles was found to be 348μm, with a rather large standard deviation (±138μm).The optimum formulation of internal aquatic phase was 2% sodium alginate + 5% dextrin + 4% gelatin. The preparation with this formulation achieved high bacteria viable count of over 109cfu/g for an extended shelf life of 37 days when stored at 4℃. When the pH value was between 6.0~7.0, the immobilized Lactobacillus E1 could sustain high storage viability. The survival of immobilized Lactobacillus E1 was significantly affected by the storage temperatures. When stored at non- refrigerated temperatures (15℃and 20℃), the storage viability declined relatively quickly. The inactivation of bacteria was accelerated with the increasing of storage temperature. However, the effect of refrigerated temperatures on the cell viability was different from that of non-refrigerated temperatures. The survival of immobilized Lactobacillus E1 at 4℃was not significantly different from that at 10℃. This finding indicated that the immobilized bacteria were not devitalized by the increased temperature during this refrigerated temperature scale. At each temperature, the storage viability of unenvelopped Lactobacillus E1 was lower than that of immobilized ones. The devitalization rate of unenvelopped bacteria was accelerated by the increasing of storage temperature, no matter during non-refrigerated or refrigerated temperature scale. Considering the energy consumption by refrigerators to achieve low temperature, 10℃was the best storage temperature for the immobilized Lactobacillus E1. When stored at 10℃, the preparation with 2% sodium alginate + 5% dextrin + 4% gelatin as protective solutes, achieved high bacteria viable count of over 109cfu/g for an extended shelf life of 37 days.The immobilized Lactobacillus E1 obtained using the optimum formulation had high acid resistance and sufficient release in SIF. When compared with the unencapsulated Lactobacillus E1, the immobilized Lactobacillus E1 had significantly higher viable count in pH 2.0 and pH 3.0 PBS. The release rate of the immobilized Lactobacillus E1 in SIF could reach above 95% after 60 min and 100% after 120 min.This preparation method needs no drying process and useful for further research of functional food ingredient which is convenient and high viable for both human dairy food and animal feedstuff.
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