Encapsulation of Lactobacillus fermentum K73 by ionotropic gelation : Evaluation of probiotic stability during gastrointestinal conditions

Abstract

El desarrollo de alimentos funcionales es una alternativa viable para la prevención de ciertas enfermedades, sin embargo, la industria alimentaria tiene grandes desafíos en la producción de alimentos funcionales basados en probióticos debido a que presentan alta sensibilidad a diferentes condiciones de procesamiento y del tracto gastrointestinal. Una de las soluciones que ha encontrado esta industria es emplear métodos de encapsulación que protegen las células probióticas y las vehiculizan al punto de acción. Sin embargo, algunas técnicas de encapsulación emplean altas temperaturas, solventes nocivos y representan altos costos de operación. Por su parte, la extrusión vibratoria es un método simple y económico con operaciones suaves que preserva de manera eficiente la concentración bacteriana. El objetivo de esta investigación fue evaluar el efecto del proceso de encapsulación por extrusión vibratoria sobre la viabilidad de Lactobacillus fermentum K73, una bacteria ácido-láctica con potencial probiótico hipocolesterolémico. Se diseñó la formulación de los materiales de pared de la perla a través de un diseño óptimo de mezcla, en el que se evaluó la proporción de diferentes materiales de pared compatibles con la bacteria. Se encontró como mezcla óptima la relación de alginato y suero de leche igual a 0,61/0,39 v/v con una viabilidad de 9,20 log10 UFC/mL. La selección de las condiciones operativas del proceso de encapsulación por extrusión vibratoria que permitieran la mayor viabilidad celular, y eficiencia de encapsulación de las perlas se realizó por medio de un diseño de superficie de respuesta.

The development of functional foods is a viable alternative for the prevention of certain diseases; however, the food industry has great challenges in the production of functional foods based on probiotics, due to their high sensitivity to different processing and gastrointestinal tract conditions. One of the solutions that the food industry has found is to develop encapsulation methods that protect the probiotic cells and transport them to the point of action. However, some encapsulation techniques use high temperatures, and harmful solvents and represent high operating costs. Vibratory extrusion, on the other hand, is a simple and economical method with gentle operating conditions that efficiently preserve the probiotic bacterial concentration. The objective of this research was to evaluate the effect of the vibratory extrusion encapsulation process on the viability of Lactobacillus fermentum K73, a lactic acid bacteria with hypocholesterolemic probiotic potential. The formulation of the bead wall materials was designed through an optimal mixture design, in which the ratio of three strategic wall materials was evaluated. It was found as the optimal mixture ratio of alginate and whey was equal to 0.61/0.39 v/v, the viability of this was 9.20 log10 CFU/mL. The selection of the operating conditions of the vibratory extrusion encapsulation process that allowed the highest cell viability, encapsulation efficiency, and sphericity of the beads was performed using a response surface design. Maximum cell viability and encapsulation efficiency were obtained with a vibratory frequency of 70 Hz, voltage of 2500 V, and feed flow rate of 20 mL/min. In addition, improved tolerance to simulated gastrointestinal tract conditions was observed following the INFOGEST model of encapsulated cells compared to free cells with a final concentration higher than 1 x 106 CFU/mL. Finally, the particles were characterized through different techniques such as SEM, ATR-FTIR, CSLM, RAMAN spectroscopy, image analysis, and evaluation of mechanical properties. In conclusion, this study demonstrated that the vibratory extrusion encapsulation process guarantees the protection of the probiotic in challenging conditions for its release at the site of action, which demonstrates the importance of encapsulation as a strategy for the development of functional foods.