Ross Crittenden

Technological challenges for future probiotic foods

Abstract Modern consumers are increasingly interested in their personal health, and expect the food that they eat to be healthy or even capable of preventing illness. Gut health in general has shown to be the key sector for functional foods in Europe. The probiotic yoghurt market is well established but the key growth sector recently has been the probiotic drinks. The popularity of dose-delivery systems for probiotic drinks has also resulted in research efforts targeted to developing probiotic foods outside the dairy sector. New product categories, and thus novel and more difficult raw materials with regard to technology of probiotics, will certainly be the key research and development area for future functional food markets. The viability and stability of probiotics has been both a marketing and technological challenge for industrial producers. Probiotic foods should contain specific probiotic strains and maintain a suitable level of viable cells during the products shelf life. Unless strict demands are set on probiotic product definition and labelling their regulatory definition will remain obscure. The technological demands placed on probiotic strains are great and new manufacturing process and formulation technologies may often be required for bacteria primarily selected for their functional health properties. Before probiotic strains can be delivered to consumers, they must first be able to be manufactured under industrial conditions, and then survive and retain their functionality during storage as frozen or freeze-dried cultures, and also in the food products into which they are finally formulated. The probiotic strains should also survive the gastrointestinal stress factors and maintain their functionality within the host. Additionally, they must be able to be incorporated into foods without producing off-flavours or textures—they should be viable but not growing. The packaging materials used and the conditions under which the products are stored are also important for the quality of products. Future technological prospects exist in innovations finding solutions for the stability and viability problems of probiotics in new food environments. Current research on novel probiotic formulations and microencapsulation technologies exploiting biological carrier and barrier materials and systems for enteric release provides promising results. Maintenance of low production costs will remain the challenge for future probiotic process and formulation technologies. Exploitation of food-grade raw materials such as native, and physically or enzymatically treated starches, is one example of future technology that has the potential to meet the challenge of broadening the range of food types into which probiotic ingredients can be successfully incorporated. Novel developments for control release systems in foods and pharmaceuticals will also provide new possibilities.

Probiotics: towards demonstrating efficacy

PROBDEMO, a multi-centre European research project, began in 1996 with the aim of demonstrating that probiotic micro-organisms can positively effect human health in rigorously conducted human clinical studies. These studies, now completed, have shown that some probiotics can influence the composition of the intestinal microbiota and modulate the host immune system with measurable benefits to health, including the control of atopic eczema in infants with food allergy. Considerable promise was also demonstrated for the use of selected probiotics in controlling inflammatory bowel disease, and infections in children and the elderly. The scientific approaches to selecting and evaluating probiotics that were demonstrated in the PROBDEMO project provide a model for food manufacturers to move further towards demonstrating efficacy for their probiotic products.

Adhesion studies for probiotics: need for validation and refinement

Adhesion of probiotic bacteria to intestinal epithelial cells is regarded as a prerequisite to exert beneficial health effects. Human intestinal epithelial lines, like Caco-2 or HT-29 cells, have been extensively used to select for adhesive strains in vitro. Adhesion to intestinal mucus has been used to a lesser extent. However, to date, there has been no standardization of the conditions used in in vitro adhesion assays. As a consequence, results obtained in different laboratories using identical strains, but different assay conditions, show great variability. This lack of standardization complicates the interpretation of data and discrepancies emerge on what is meant by effective adhesion. A critical validation of in vitro adhesion is essential for the food industry, using adhesion assays as predicitve screening tools to assess new probiotic strains. In this review we summarize a comparative study on adhesion of the well characterized probiotic bacteria L. johnsonii La1 and L. rhamnosus GG with respect to the influence of bacterial growth conditions, growth phase, buffer, pH, and mucus on adhesion properties. The results are employed in the current scientific discussion to allow a critical evaluation on the reliability of the in vitro assays.

Safety evaluation of probiotics

The market for functional products, such as probiotics, is undoubtedly the fastest growing area of new food product development. This market introduces a new paradigm for food safety professionals: beneficial physiological effects beyond those of good nutrition without adverse effects. This specificity generates a need for new approaches in food safety evaluation. Conventional toxicology and safety evaluation alone is of limited value in the safety evaluation of probiotic microorganisms. Instead, a multidisciplinary approach is necessary, involving the contributions of pathologists, geneticists, toxicologists, immunologists, gastroenterologists, and microbiologists. In the case of new products, the objective is to produce products that are at least as safe as conventional counterparts regardless of potential health benefits. In the case of existing strains, the history of safe use criterion is very much associated with being able to detect, enumerate and characterize strains to ensure consumers have been ingesting the same organism throughout the claimed exposure period.

Probiotic research in Australia, New Zealand and the Asia-Pacific region

Although the epicentres of probiotic research in the past decade have been Japan and Europe, researchers in the Asia-Pacific region have actively contributed to the growing understanding of the intestinal microbial ecosystem, and interactions between gut bacteria, diet and health of the human host. A number of new probiotic strains have been developed in the region that have been demonstrated to have beneficial impacts on health in animal and human trials, including improved protection against intestinal pathogens and modulation of the immune system. Probiotics targeted to animals, including aquaculture, feature heavily in many Asian countries. Developments in probiotic technologies have included microencapsulation techniques, antimicrobial production in fermented meats, and synbiotic combinations. In particular, the impact of resistant starch on the intestinal environment and fermentation by intestinal bacteria has been intensively studied and new probiotic strains selected specifically for synbiotic combinations with resistant starch. This paper provides an overview of probiotic research within Australia, New Zealand and a number of Asian countries, and lists scientists in the Asia-Pacific region involved in various aspects of probiotic research and development.

Probiotics - how effective are they?

For most of the last century lactobacilli and bifidobacteria have been actively promoted as being beneficial to health. Most of the time, evidence for their benefits has been limited to anecdotal recordings. Only since the 1980s have there been well-designed animal experiments and human clinical trials conducted on probiotic bacteria. Unfortunately, the health professionals? view of probiotics is based on the mystique and chicanery used in earlier days to market probiotics. Marketing of this kind is still commonplace. However, research conducted primarily in the last 10 years has started to identify health benefits imparted by specific strains of probiotic microorganisms. This paper presents the evidence accumulated so far for beneficial effects on the health of consumers.