Assessment of bacteria microencapsulation performance through bio-speckle dynamic analysis

Probiotics are microbial species that have been demonstrated to confer benefits to health. In recent years, the use of probiotics in food and health has increased enormously. A sufficient concentration of probiotics in the intestine acts against pathologies such as obesity, diabetes, etc. However, if probiotics are not able to maintain their viability during their transit through the gastro-intestinal apparatus, they cannot act to enhance the immune system. Hence, protection and preservation of probiotics are essential to both food industry and in pharmaceutics. Microencapsulation is one of the most common methods of preservation, applicable to several biological matrices, including probiotics. Whenever food products or pharmaceutical formulations contain microencapsulated probiotics, it is important to quantify the effectiveness of micro-encapsulation as a microbial protection system over the time, e.g. during the shelf life of a functional product containing encapsulated probiotics, conserved in the supermarket, and during gastro-intestinal transit. Here we use bio-speckle decorrelation as a tool for the rapid assessment of microencapsulation effectiveness. Although speckles are often thought as a noise to get rid of, they represent a precious source of information, increasing the sensitivity of image sensors based on coherent illumination. Such information is exploitable to characterize bacterial dynamics in a fast and simple way suitable for applications in food science and industry. Through bio-speckle decorrelation, we quantify the shelf-time of alginate-encapsulated Lactobacillus rhamnosus and Lactobacillus plantarum probiotic bacteria and their survival rate under simulated gastro-intestinal conditions.