Electrospinning as a useful technique for the encapsulation of living bifidobacteria in food hydrocolloids

This study shows the feasibility of using the electrospinning technique to encapsulate Bifidobacterium strains in food hydrocolloids for functional food applications. Specifically, a protein (whey protein concentrate) and a carbohydrate (pullulan) were used as encapsulation materials due to their ability to form micro, submicro and nanocapsules through an electrospraying process. The concentration of both biopolymers was adjusted so as to obtain functional hybrid capsules easier to handle as a food ingredient. Microcapsules containing the strain Bifidobacterium animalis subsp. lactis Bb12 were prepared from solutions of the hydrocolloids both, in PBS and in skimmed milk, resulting in structures with different morphology and protection ability. The morphological features of the obtained systems were characterized and the viability of the encapsulated probiotic was compared to that of the same bacterium in liquid medium (PBS or skimmed milk) and freeze-dried. Freeze-drying of a mix containing bacterium and the biopolymers was also carried out for comparison. The viability tests were conducted at two different temperatures (20 degrees C and 4 degrees C) and at various relative humidities (0%, 11%, 53% and 75%). The results showed that, as expected, the survival of the bifidobacterial strain increased when stored in skimmed milk or obtained from skimmed milk solutions in comparison with those stored or obtained from PBS. Encapsulation through electrospraying substantially increased the viability of the bifidobacterial strain, especially at 20 degrees C. WPC demonstrated greater protection ability as encapsulation material than pullulan as it effectively prolonged the survival of the cells even at high relative humidity. (C) 2011 Elsevier Ltd. All rights reserved.