Microencapsulation of Probiotic Cells for Food Applications

Abstract

The addition of microencapsulated probiotic cells to food products is a relatively new functional food concept. Most of the published scientific research in this field is not older than ten years. However, the technological background reaches back to the 1980s, where lactic acid bacteria were microencapsulated within the concept of the so-called immobilized cell technology (ICT). Target applications of ICT were continuous fermentation processes and improved biomass production. The methods adopted from immobilized cell technology were applied for the microencapsulation of probiotics, often optimized towards specific requirements associated with the protection of probiotic cells in food applications. However, there are still significant hurdles with respect to currently available methods for probiotic cell microencapsulation. This is mainly due to the fact that important characteristics of microcapsules based on ICT appear to be in conflict with the requirements arising from an application of probiotic microcapsules in food products, with particle size and inappropriate matrix characteristics being the most prominent ones. Based on this situation the aim of this review is to give a critical overview of the current approaches regarding the microencapsulation of probiotic cells for food applications and to report on emerging developments.

Microencapsulation of Lactic Acid Bacteria (LAB)

“…Also Brusch-Brinques et al (2011) stated the efficiency of microencapsulated probiotics into yoghurt resulting in an increased survival of Lactobacilli in yoghurt under refrigerated storage, but on the same time, there is a significant effect on sensorial attributes of the food product to detect. Graininess, for example, is associated with large capsule sizes, and flavor changes may be caused due to complex reactions between capsule hydrocolloids and yoghurt matrix (Heidebach et al, 2012). Therefore, Truelstrup-Hansen et al (2002) recommended generally a microcapsule size below 100 µm in order to avoid a negative sensorial impact of microcapsules in food.…”

“…An aqueous polymer, such as modified starch, whey protein isolate, gelatin etc. containing solution, makes the capsules hard enough to protect the LAB cells against harsh conditions, hereby serves as a base to form strong microcapsules (Heidebach et al, 2012). However, there are still difficulties during spray dying processes which have to be overcome.…”

“…It is of utmost interest to keep the number of living cells stable by microencapsulation technology, since there is a long way until LAB will reach their final destination in human gut and exert their probiotic effects. On the same time, capsules should be formed in the size that doesn't have any adverse influence regarding sensorial aspects of food product (Heidebach et al, 2012). The size of microcapsules as well as the processing steps of generating small beads can have significant influences on the microcapsules yield (Capela et al, 2007).…”

“…However, not all cheese types are suitable for adding microencapsulated cell cultures, because the physiological condition in a hydrocolloid matrix of alginate is not as favorable for the bacteria as a milk protein based rennet-gel-matrix (Godward and Kailasapathy, 2003;Heidebach et al, 2012). Addition of microencapsulated probiotic bacteria to Feta cheese can slow acid development during storage and increase water-holding capacity of the cheese, due to open texture of cheese, possible disintegration of microcapsules in brine solution and a higher salt uptake during incorporation, microencapsulated probiotic bacteria cannot be protected well (Kailasapathy and Masondole, 2005).…”

“…By proper adjustment and control of the processing conditions, such as 'inlet and outlet' temperatures, viable encapsulated cultures of desired particle size distribution can be achieved (Kailasapathy, 2002). Besides the production of small size capsules at generally low costs, it has widespread application in the food sector by converting liquids into solid dry powders and a potential alternative to ICT based encapsulation methods (Heidebach et al, 2012). An aqueous polymer, such as modified starch, whey protein isolate, gelatin etc.…”