Pectin-microfibrillated cellulose microgel: Effects on survival of lactic acid bacteria in a simulated gastrointestinal tract.

Using high pressure microfluidization, we prepared micro-fibrillated soybean cellulose (MFSC) and analyzed its morphology and structure. MFSC was then incorporated into low-methoxyl pectin (PC) to coat lactic acid bacteria (LAB) by ionotropic gelation, and the effects of PC-MFSC microgel on LAB survival in a simulated gastrointestinal tract were investigated. Particle size analysis showed that the MFSC particle size decreased significantly with increasing jet pressure. Transmission electron microscopy analysis indicated that many cellulosic microfibers appeared at 150 MPa. Infrared spectroscopy and X-ray diffraction analysis revealed that the crystal structure changed from β-cellulose I type to II type with increasing jet pressure, but excessive pressure (200 MPa) damaged the crystalline structure of MFSC. Scanning microscopy indicated that cellulosic microfibers not only promoted a compact pectin gel morphology but also adhered to and coated the LAB in the pectin gel. MFSC-150 stabilized the pectin gel network, preventing the weakening of the gel under low pH conditions. Compared with other PC-MFSCs, PC-MFSC-150 microgel significantly decreased LAB susceptibility to gastrointestinal juice and increased the viability of LAB. • Jet pressure was the key factor determining the micro-structure of MFSC. • High pressure (150 MPa) could degrade cellulose into semi-crystalline microfibre. • Semi-crystalline microfibre stabilized the pectin gel network in low pH condition. • PC-MFSC-150 microgel improved the tolerance of LAB in gastrointestinal fluid. [ABSTRACT FROM AUTHOR]