Rangne Fondén

Probiotic bacteria: safety, functional and technological properties

During the past two decades probiotic (health promoting) micro-organisms have been increasingly included in various types of food products, especially in fermented milks. Several aspects, including safety, functional and technological characteristics, have to be taken into consideration in the selection process of probiotic micro-organisms. Safety aspects include specifications such as origin (healthy human GI-tract), non-pathogenicity and antibiotic resistance characteristics. Functional aspects include viability and persistence in the GI-tract, immunomodulation, antagonistic and antimutagenic properties. Before probiotic strains, chosen on the basis of their good safety and functional characteristics, can benefit the consumer, they must first be able to be manufactured under industrial conditions. Furthermore, they have to survive and retain their functionality during storage, and also in the foods into which they are incorporated without producing off-flavours. Factors related to the technological and sensory aspects of probiotic food production are of utmost importance since only by satisfying the demands of the consumer can the food industry succeed in promoting the consumption of functional probiotic products in the future.

Demonstration of safety of probiotics: a review.

Probiotics are commonly defined as viable microorganisms (bacteria or yeasts) that exhibit a beneficial effect on the health of the host when they are ingested. They are used in foods, especially in fermented dairy products, but also in pharmaceutical preparations. The development of new probiotic strains aims at more active beneficial organisms. In the case of novel microorganisms and modified organisms the question of their safety and the risk to benefit ratio have to be assessed. Lactic acid bacteria (LAB) in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus are most commonly given generally-recognised-as-safe (GRAS) status whilst members of the genera Streptococcus and Enterococcus and some other genera of LAB contain some opportunistic pathogens. Lactic acid bacteria are intrinsically resistant to many antibiotics. In many cases resistances are not, however, transmissible, and the species are also sensitive to many clinically used antibiotics even in the case of a lactic acid bacteria- associated opportunistic infection. Therefore no particular safety concern is associated with intrinsic type of resistance. Plasmid-associated antibiotic resistance, which occasionally occurs, is another matter because of the possibility of the resistance spreading to other, more harmful species and genera. The transmissible enterococcal resistance against glycopeptide antibiotics (vancomycin and teicoplanin) is particularly noteworthy, as vancomycin is one of the last effective antibiotics left in the treatment of certain multidrug-resistant pathogens. New species and more specific strains of probiotic bacteria are constantly identified. Prior to incorporating new strains into products their efficacy should be carefully assessed, and a case by case evaluation as to whether they share the safety status of traditional food-grade organisms should be made. The current documentation of adverse effects in the literature is reviewed. Future recommendations for the safety of already existing and new probiotics will be given.

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.

The technology of probiotics

One important task of the Fair CT96-1028 project (Demonstration of Nutritional Functionality of Probiotic Foods) has been to demonstrate the possibility of producing, on a pilot scale, probiotic dairy foods acceptable to European consumers. In the project, different Lactobacillus spp. and Bifidobacterium spp. strains were shown to be suitable for probiotic organisms. Culture concentrates were produced by standard methods, and showed high cell concentrations and good survival during storage at low temperatures. The starter cultures were used in producing several different probiotic dairy foods. Under certain conditions probiotic strains may be used as the sole fermenting agent in milk. However, in many cases use of a support culture is preferable. Probiotic dairy products were shown to have good organoleptic properties, and the survival of the probiotic organisms was excellent during the shelf life of the products.

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.

Retention of vitamin B12 during manufacture of six fermented dairy products using a validated radio protein-binding assay

Abstract The aim of this work was to study vitamin B 12 retention during manufacture of six fermented dairy products. Careful validation of a commercial radio protein-binding kit showed this assay to be suitable after optimisation of sample pre-treatment and control of the kit for possible matrix effects. In fermented milks, vitamin B 12 concentrations decreased by 40–60%, compared with the starting milk, during storage of the final product at 4°C for 14 days, most likely attributed to consumption by starter cultures. In cottage cheese, hard cheeses and blue cheese, 18–56% of the vitamin B 12 originally present in the milk was retained. Removal of the whey fraction was the dominant factor reducing vitamin B 12 retention in cheeses, while the fermentation by starter cultures hardly affected vitamin B 12 concentrations.

Functional Aspects of Pro- and Prebiotics A literature review on immune modulation and influence on cancer

The intestinal flora plays an important role in stimulating the defence system of the organism. There are indications that children of the industrialised world are underexposed to natural intestinal microbes leading to hypersensitivity towards many common food components later in life. It has been shown that certain lactic acid bacteria (probiotics) for example, are able to modulate the immune system. The mechanisms are not yet known. It has been demonstrated that ingestion of probiotics can alleviate hypersensitivity and eczema in children. There are strong indications that probiotics may possess cancer preventive properties by suppression of pre-neoplastic changes in colon and prevention of oxidativeDNA damages. The proportion and composition of probiotic microbes as part of the intestinal flora is dependent of many factors such as eating habits and life style. Being mainly saprophytes probiotic bacteria depend on fermentable carbohydrates in the colon. Prebiotics designate carbohydrates (food-fibres) that are indigestible in the small intestine but fermentable by probiotic bacteria. Some prebiotics exert a selective function. Especially fructo oligosaccharides (FOS) seem to stimulate bifidobacteria but the specific effect of different oligosaccharides towards different probiotic bacteria is not sufficiently investigated. Keywords: probiotics, prebiotics, hypersensitivity, eczema, immune modulation, cancer.The intestinal flora plays an important role in stimulating the defence system of the organism. There are indications that children of the industrialised world are underexposed to natural intestinal microbes leading to hypersensitivity towards many common food components later in life. It has been shown that certain lactic acid bacteria (probiotics) for example, are able to modulate the immune system. The mechanisms are not yet known. It has been demonstrated that ingestion of probiotics can alleviate hypersensitivity and eczema in children. There are strong indications that probiotics may possess cancer preventive properties by suppression of pre-neoplastic changes in colon and prevention of oxidative DNA damages. The proportion and composition of probiotic microbes as part of the intestinal flora is dependent of many factors such as eating habits and life style. Being mainly saprophytes probiotic bacteria depend on fermentable carbohydrates in the colon. Prebiotics designate carbohydrates (food-fibres) that are indigestible in the small intestine but fermentable by probiotic bacteria. Some prebiotics exert a selective function. Especially fructo oligosaccharides (FOS) seem to stimulate bifidobacteria but the specific effect of different oligosaccharides towards different probiotic bacteria is not sufficiently investigated.