EFECTO DEL AGENTE ENCAPSULANTE EN LA VIABILIDAD DE UN MICROORGANISMO PROBIÓTICO (Lactobacillus rhamnosus B442)

Abstract

In recent years, probiotics have become increasingly important. Final their consumption has effects on the human digestive system. For this reason, the industry is looking for processes which preserve the viability of these types of microorganisms (m.o.) to fulfill their function, such as the techniques of encapsulation that protect them against environmental conditions that may reduce their viability. Probiotics need prebiotic substances (such as inulin and resistant starch) to maintain their viability. The aim of this study was to evaluate the effect of native rice starch and inulin as wall material in the encapsulation of probiotics. To determine the conditions of process, an experiment was carried out for each of the encapsulating agents, estimated as the variables of response: the encapsulation efficiency, expressed as the number of viable microorganisms in colony forming units (CFU/g). To evaluate the individual application of the encapsulating agent bacterial suspensions of Lactobacillus rhamnosus were proposed at 109 CFU/g at 10,15 and 20 % concentration (w/w). Each suspension was dried sprayed, using a flow rate of 14 g/min and inlet temperatures of 135 and 155°C, considering a suspension of 15% and 145°C as a central point. The obtained powders were analyzed for moisture content, water activity (aw), bulk density, particle size, fermentability, morphology and distribution of lactobacillus in the encapsulating agents. Also, the viability of storage at two temperatures for 4 weeks (32 days), was assessed: at room temperature (25°C) and refrigeration temperature (4°C), observing that the smaller reduction in log units was obtained in the following conditions: starch 20%, inlet temperature of 135°C, and outlet temperature 65°C, and when the storage time effect was tested, the viability of the m.o. did not change at the different starch concentrations, but difference was found with the m.o. encapsulated with inulin. The results show that the formation of microcapsules porous of rice starch effectively protected the microorganisms regardless of the temperature at which they were stored, and the CFU/g obtained at the end of this test are within the parameters established to be considered a functional product (5.83 x 108 CFU/g). Powders with inulin had log reductions greater of 25°C, the refrigeration temperature was more appropriated to have a smaller reduction. Humidity and water activity (aw) values obtained for the powders were low and they are considered appropriate. There was also a homogeneous particle size for both agents (5-6 μm) during the encapsulation process. The powder with higher viability during the stability test were used to determine the fermentative capacity (prebiotic test), showing that both wall material were used by the m.o. in different level due to the acid lactic production (decrease of pH) in the MRS medium