Microencapsulation of Lactiplantibacillus plantarum CRL2211 for bakery application: thermal, gastrointestinal and storage survival

Abstract

Probiotics and technological relevant microorganisms must be able to retain viability and metabolic activity under stressful conditions such as processing, storage and gastrointestinal transit. In order to exert health benefits, the selected bacteria must be present at a minimum level of 106 CFU/g of food product. In recent years, probiotic bakery products have been proposed as a food innovation. However, microorganisms must be carefully protected to ensure their safe delivery to the host. Microencapsulation shows a great potential for conferring protection on cells that need to be added to foods with an unfavorable environment. The most commonly reported microencapsulation procedure is based on the calcium alginate gel capsule formation. Lactiplantibacillus plantarum CRL2211 is a legume strain that removes antinutrients from pulses flours by fermentation. These improved flours have been used for the manufacture of a functional legume cracker. The objective of this work was to produce lactobacilli microcapsules by ionic gelation into alginate beads, and evaluate their viability after heat treatment, simulated gastrointestinal conditions and storage. Lactobacilli at stationary phase (108 CFU/mL) were microencapsulated by extrusion with 2% sodium alginate as coating material. For thermal treatment, the beads were included into fermented legume doughs and exposed for 10 min at 70°, 100°, 120° and 140°C. For gastrointestinal tolerance, the beads were incubated in a successive manner in simulated saliva (lysozyme and α-amylase, pH 6.5, 10 min), gastric (pepsin and HCl, pH 3, 90 min) and pancreatic juice (bile salts, pancreatin and NaOH, pH 8, 90 min). Beads were stored at 25°C and 4°C during 100 days. Microorganisms were released with sodium citrate 0.1 M, ten-fold diluted and plated on MRS agar. The morphology and size of beads was assessed by microscopy. Scanning electron microscopy confirmed the formation of smooth, spherical, micron-sized beads with a mean diameter of 434.8 ±48.3 µm and lactobacilli included into the alginate matrix. Microencapsulated lactobacilli showed an improved survival after simulated gastrointestinal passage since a decrease of 1 log was observed after complete digestion (106 CFU/mL) but 3 log were lost from free cells suspensions. Microencapsulation and refrigeration (4°C) improved survival of microorganisms and more than 106 CFU/mL were recovered after 45 days of storage. Surprisingly, L. plantarum CRL 2211 survived all the thermal treatments, but in concentrations too low to exert a beneficial effect (103 CFU/mL at 120°C and 102 CFU/mL at 140°C). Our results show that microencapsulation in alginate beads is suitable for retaining viability of L. plantarum CRL2211 during gastrointestinal transit and storage but it is not appropriate for protecting this strain from cooking. Other coating materials should be tested in order to include this LAB into functional crackers or it should be considered as a postbiotics source.