PART III PROCESS SAFETY
3. Probiotics
The more our knowledge on gut microbial ecology expands the more likely it is that the beneficial or pathogenic nature of bacteria at species and even strain level will be identified and therefore the above classification should be regarded as indicative only.
In addition to LAB, Bacillus spp., fungi such as Aspergillus spp. and yeasts such as Saccharomyces boulardii have been used as probiotics.
3.1. Selection criteria for probiotics
To be able to exert its beneficial effects, a probiotic microorganism should be able to survive a range of harsh physicochemical factors during transit through the stomach and small intestine, and finally it should be able to persist in the gut. For these reasons, main selection criteria for probiotic strains include the following characteristics (Ouwehand et al., 1999; FAO/WHO, 2002):
➢Non-pathogenic and non-toxic.
➢Resistance to gastric acidity and bile acids.
➢Adherence to mucus and/or human epithelial cells and cell lines.
➢Colonisation of GI tract.
➢Production of antimicrobial substances.
➢Competitive exclusion and antagonism against pathogenic bacteria.
➢Ability to stimulate host’s immune response.
➢Good technological properties (e.g. long self life, high viability, stability and functionality).
➢Clinically validated and documented health effects.
3.2. Legislation, safety considerations and claims for the use of probiotics in foods
Although LAB have a long term history of safe use in human food (Adams and Marteau, 1995), it is generally accepted that zero risk can never be applied to the ingestion of live microbes whether these are probiotics, starters or compo- nents of natural microbiota of fresh foods e.g. fruits and vegetables (Saarela et al., 2002).
Therefore, even among a group of bacteria that is generally recognised as safe (GRAS) as for example Lactobacillus spp., it is recommended that probiotic stains be characterised at a minimum with the following tests (FAO/WHO, 2002):
1. Determination of antibiotic resistance patterns
2. Assessment of certain metabolic activities (e.g. deconjugation of bile salts) 3. Testing for toxin production.
4. Haemolytic potential.
5. Lack of infectivity by a probiotic strain in immunocompromised animals.
6. Assessment of side-effects during human studies (i.e. systemic infections, dele- terious metabolic activities, excessive immune stimulation in susceptible indi- viduals and gene transfer).
7. Epidemiological surveillance of adverse incidents in consumers (post market).
Careful assessment is also needed in the case of immunocompromised per- sons or those under antibiotic treatment as probiotic supplementation could
possibly create complications (Pletincx et al. 1995). However, it should be noted that documented correlations between systemic infections and probiotic con- sumption are few and all occurred in patients with serious underlying medical conditions such as immunocompromised persons (FAO/WHO, 2002; Saarela et al., 2002).
General health claims allowed for foods containing probiotics fall under the guidelines for the use of nutrition claims adopted by the Codex Alimentarius since 1997. FAO/WHO (2002), has recommended that specific health claims such as enhanced function and/or disease prevention claims on foods containing pro- biotics should be allowed only in cases where sufficient scientific evidence is available. In the European Union such evidence has to be assessed by the European Food Safety Authority, prior to its use in the labelling, presentation and advertising of foods, according to the European Commission 2003/0165 (COD) proposal on nutrition and health claims made on foods.
3.3. Health benefits – established effects
In most cases, the health benefits attributed to probiotic consumption depend on the probiotic strain used. In addition, other factors such as host age, health status, stress and overall diet will most probably have various effects on the efficacy of the probiotics consumed. Since probiotics are beneficial microbes, their health promoting effects generally fall under the beneficial for health scheme such as the enhancement of gut barrier function (Fig. 1), reported earlier for the GI microflora.
Generally, health benefits claimed for probiotics are summarised in Figure 2 and refer to improved states of: a) intestinal condition and health (e.g. relieve of constipation, alleviation of lactose intolerance, recovery from viral and antibiotic induced diarrhoea, detoxification effects – antimutagenic/anticarcinogenic effects, alleviation of colitis symptoms), b) improved host nutrition (e.g. synthe- sis of vitamins, lowering of serum cholesterol), c) immune modulation (e.g. stim- ulation of immune response, enhancement of gut barrier function). In addition, ongoing research studies investigate the potential of probiotics towards the pre- vention of colo-rectal cancer (Saarela et al., 2002).
From the health benefits claimed for probiotics, the most well established effects in humans refer to the alleviation of symptoms of lactose intolerance and food allergies as well as the preventative and therapeutic effects against diarrhoea (Rowland, 1999). Therefore, it is obvious that probiotic fortification of foods is of relevance to food safety since their consumption could improve gut function and resistance to gastrointestinal infection.
For most probiotic microorganisms efficacy is demonstrated with daily con- sumption of 108– 1011organisms per day (Scheinbach, 1998). Thus, in order to provide consumers with useful information, it is recommended that food manu- facturers apart from designating on the labels of their products the probiotic stain(s) used, they should also point the suggested serving size needed to deliver the effective dose of probiotics related to the health claim.