Preparation and optimization of soy protein isolate–high methoxy pectin microcapsules loaded with L actobacillus delbrueckii

Summary This study was aimed to use soy protein isolate ( SPI ) and high methoxy pectin ( HMP ) as encapsulating materials for probiotic bacterial ( L actobacillus delbrueckii ) delivery systems. The encapsulation conditions were optimised, and scanning electron microscopy ( SEM ) was used to characterise the microstructural changes of the microcapsule. The results showed that the optimal conditions for microcapsule preparation were 90 mg mL −1 SPI and 1 mg mL −1 HMP , with a SPI / HMP ratio of 7:1 (v/v), and a L .  delbrueckii suspension to SPI – HMP complex ratio of 1:1 (v/v). The viability of the probiotics in the microcapsules reaching the small intestine was 3 log CFU  mL −1 higher than that of naked bacteria. SEM showed that the surface of the SPI – HMP compound microcapsules was smooth and that a large number of L .  delbrueckii could be seen in cross‐sections of the microcapsules.