Lactobacillus paracasei isolated from grape sourdough: acid, bile, salt, and heat tolerance after spray drying with skim milk and cheese whey

Lactic acid bacteria have been isolated from sourdough and could present important properties in food manufacturing as starter cultures and also as probiotics. This study evaluated the resistance of Lactobacillus paracasei strain isolated from sourdough to spray drying in the presence of reconstituted skim milk (RSM) and cheese whey (CW). The in vitro tolerance to acid, bile, sodium chloride (NaCl) and heat was studied to free and microencapsulated cells. The microcapsules moisture was determined, and the morphology was observed by scanning electron microscopy. The viability of free and microencapsulated cells decreased by 4.25 log CFU mL⁻¹and 1.00 log CFU g⁻¹, respectively, when exposed to pH 2.0 for 3 h. At pH 3.0, free cells decreased 0.3 log CFU mL⁻¹, while the microencapsulated form maintained its viability even after 3 h of exposure. After 12 h of exposure to 2 g 100 mL⁻¹bile salts, free and microencapsulated L. paracasei decreased 3.34 log CFU mL⁻¹and 2.17 log CFU g⁻¹, respectively. No significant cell loss was observed, for free and microencapsulated form when exposed to NaCl, and microencapsulated cells survived well for 15 min at 65 °C. Moisture content of microcapsules ranged from 4.30 to 4.77 g 100 g⁻¹. L. paracasei was found to possess desirable in vitro resistance to low pH and bile salts, and the microencapsulation in RSM and CW provided a cell protection against acidic pH and bile salts. This strain is good candidate for further investigation to elucidate its potential health benefits and in fermentation processes.