According to Food and Agriculture Organization (FAO), World Health Organization (WHO), International Life Sciences (ILSI) and European Food and Feed Cultures Association (EFFCA), probiotics have been defined as live microorganisms which when administrated in adequate amounts confer a health benefit to the host 6.
In 2002, a cooperation between research groups from FAO and WHO released criteria to evaluate the probiotics. Four minimum requirements resulted from the experiments to consider a specific microorganism to be probiotic 6:
1. Strain identity assessment (genus, species, strain level);
2. In vitro tests to screen potential probiotics: e.g. survival of the microorganism in the digestive system environment, antimicrobial properties against potentially pathogen;
3. Safety assessment: requirements for proof that a candidate probiotic strain is safe and without contamination in its delivery form;
4. In vivo studies for substantiation of the health effects in the target host.
The studies of probiotics are contemporary. Despite that evaluation, there are numerous questions regarding this matter that still ambiguous. For example, the delivery mode and the mode of action in the human body haven’t been specified. This question derived from the case of the delivery of the lactase through injection of live Streptococcus thermophilus directly into the small intestine. This microbe can be considered as a probiotic, even though the bacterial strain itself does not survive in the digestive pathway 7.
When considered probiotics functionality, the interpretation of definition is wide-ranging. This creates the difficulty when trying to define the perquisite of probiotics. For instance, the use of probiotics could target diverse locations of the human body and its application can also target specific human subgroup. There is also a diverse range of potential biological effects and new functional activities are constantly being explored 6. The advantages of these microbes are countless. Among them, the most prominent health benefit is the protection and treatment of diarrhoea and the increase of the immune.