| Summary: | 碩士 === 國立海洋大學 === 食品科學系碩士在職專班 === 90 === Abstract
It has been known that the lactic-producing lactobacilli in fermented dairy products can inhibit potentially pathogenic bacteria toxin formation in the large intestine of host and is inferred that having the effect of prevention and protection which can improve health and prolong life. Although the ideas were originally related to lactic acid bacteria in dairy products, the interest of other scientists soon turned to lactic acid bacteria of intestinal origin i.e., the living microorganisms. Recent work is further to define that as the products made from the cell preparations, components of viable cultures and non-viable cultures, or metabolites that have beneficial effect on the health of the host. Probiotic preparations nowadays used in food mainly belong to Bifidobacterium, Lactobacillus, Lactococcus, Streptococcus thermophilus, Enterococcus, and Saccharomyces species. Probiotic, the microorganism that has beneficial effects in fermented dairy products, was coined in 1965 and used to describe several species of protozoa that can produce substances to prolong the logarithmic phase in other species during their logarithmic phases of growth. In 2001 the definition is widened to as the foods or products containing enough amounts of live microorganisms that can positively influence the microflora of the colon and improve the health of the host when consumed in adequate amounts. Gradually the definition does not restrict the use of probiotics. Not only the whole microbial cells but also parts of cells including viable cultures, non-viable cultures, cells extracts, or metabolites of these microorganisms can be accepted as the applied forms of probiotics. Besides, the strains of probiotic used in food should be attributed to food grade organism and human origin. Several technologies are used for distinguishing probiotics from bacteria. The enumeration method selects a set of culture media to perform the enumeration of probiotic when it appears together with bacteria of lactic acid starters in fermented dairy products. The approaches are simple and time-saving and can offer a good cell recovery for the microorganisms. The taxonomy and physiology of probiotics can be implemented by using the polyphasic taxonomy that combines morphological, biochemical and physiological characteristics with molecular-based phenotypic and genomic techniques. Comparing the sequence of rRNA is currently the most powerful and accurate technique for determining the degree of phylogenetic relation of microorganisms. Based on the available information on the sequences of 16S/23S rRNA, the phylogenetic trees can be created. Due to the claimed beneficially physiological effects are beyond those of good nutrition without adverse effects, conventional toxicology and safety evaluation is of limited value in the safety evaluation of probiotic microorganisms. Therefore, a multidisciplinary approach involving the contribution of pathologists and microbiologists is necessary. Furthermore, a few rare cases of infection have so far been associated with lactic acid bacteria. Safety implications should be taken into consideration before using new strain to make composition food or medicine. A potential probiotic bacteria should fulfill the following criteria: (1) easy to prepare as viable culture concentrate on a large industrial scale, (2) able to survive during preparation and storage of the carrier foods, and (3) able to survive in the intestinal ecosystem of the host. To ensure the ability of improving health effects, the initial screening and selection of probiotics should include the stability test of phenotype and genotype which takes account of (a) plasmid stability; (b) carbohydrate and protein utilization patterns; (c) the ability to tolerate, survive, and grow in acid and the bile metabolism; (d) the adhesion properties of intestinal epithelium; (e) the ability to produce antimicrobial substances and antibiotic resistance patterns. The adhesive properties, metabolism, and morphology of probiotics grown in intestinal contents or intestinal mucus may affect health effects. The adherence to mucosal surfaces contributes to the efficacy of a probiotic. Probiotics indigenous strains might contribute to the prevention of infection by pathogenic micro-organisms by blocking attachment sites and/or producing short-chain fatty acids (SCFAs) that inhibit the growth of pathogenic organisms. The properties of fermented products depend on the strain, inoculation level, temperature, and time. The manufacturing process thus should consider carefully the effects on the selection and characteristics of starter cultures and the interactions between different strains to maintain the vitality and stability. Nowadays probiotics are widely used in fermented foods including infant formula, fruit drinks, and sweet milk. Fermented milk and cheese are the most common foods with probiotics. Probiotic cultures may be used in special shapes like capsules or tablets, or they may be used in the production of a large variety of fermented food products. In some cases the cultures may be added to a food to contribute specific probiotic or functional properties. With innovation in a variety of foods and drinks such as snack, biscuits, ice creams, and confectionery the incorporation of probiotic strains should not impact negatively on product quality. Future research on probiotic bacteria will center on selecting new and more specific strains for the well being of the host age group, healthy populations, and disease specific. The work of simplicity and liability to categorize and identify probiotic should be improved under the cost. The future research trends will be to inter-link the expertise and scientific knowledge on food, gastrointestinal tract (GI-tract) functionality, and human health. In the clinical research, develop diagnostic tools and biomarkers for their assessment will help studying the mechanisms of action of probiotics in the GI-tract. To develop technology for non-dairy probiotic applications (i.e., bean, cereal based materials and snack) will be essential for the probiotic industry.
Keywords: Lactic acid bacteria; Probiotic; Food safety; Health effects; Processing food
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