Starter Cultures and Fermented Milk Products

Lesson 29. NUTRITIONAL, THERAPEUTIC, SAFETY AND QUALITY ASPECTS OF PROBIOTIC PRODUCTS

Module 15. Probiotics, acidophilus and bifidus milk products

Lesson 29
NUTRITIONAL, THERAPEUTIC, SAFETY AND QUALITY ASPECTS OF PROBIOTIC PRODUCTS

29.1 Introduction

Probiotic, prebiotics and synbiotic products are known for their therapeutic benefits. However, when they are sold as food, other aspects like sensory attributes, nutritional value, safety, quality, etc are also given due importance.

29.2 Prebiotic

A prebiotic is “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well being and health”, whereas synergistic combinations of pro- and prebiotics are called synbiotics. Prebiotics encompass fructo-oligosaccharides (FOS), trans-galacto-oligosaccharides (TOS), isomalto oligosaccharides (IMO), xylo-oligosaccharides (XOS), soyoligosaccharides (SOS), glucooligosaccharides (GOS), lactosucrose and many more. Non-digestible oligosaccharides (NDOs) are dietary substrates which meet the criteria of prebiotics. Oligosaccharides are sugars consisting of between approximately 2 and 20 saccharide units – that is, they are short-chain polysaccharides. Some occur naturally in several foods such as leek, asparagus, chicory, Jerusalem artichoke, garlic, onion, wheat, banana and oats, as well as soybean. The premise is that the selective substrate would be metabolised by the live addition in the gut. This would enhance probiotic survival, as well as offer the advantages of both gut microbiota management techniques.

29.3 Synbiotics

A synbiotic has been defined as ‘a mixture of probiotics and prebiotics that beneficially affects the host by improving the survival and implantation of live microbial dietary supplements in the gastrointestinal tract’. Prebiotics and synbiotics are much newer concepts than probiotics, and as such information on their health-promoting properties is more sparse. Nevertheless, the beneficial outcomes are likely to be similar to those of probiotics, with the chance that these are more enhanced, given the issues of reduced survivability.

29.4 Nutritional Value of Probiotic Foods

Nutritional value of any food depends on the type of raw material used, their nutrient content and the quality of nutrients. When milk is used as the raw material to make probiotic food, it is obvious that all the nutrient present in milk will also be present in the probiotic food. However, during the process of manufacture and standardization some changes occur in nutrient content. Further, the process of fermentation brings major changes in nutrients quantitatively and qualitatively (Figure 30.1).

Fig. 29.1 Change in nutritive value of probiotic fermented foods

29.4.1 Changes due to processing

These changes can be due to standardization or supplementation of some substances in the product formulation. This can be easily understood and can be calculated while calculating nutritive value of the final product. There can be some changes in nutrients due to heat processing also.

29.4.2 Changes due to fermentation

During the process of fermentation due to the microbial growth and metabolism, several quantitative and qualitative changes occur in nutrients of the substrate. Microbial growth and metabolism results in the production of diversity of metabolites. These metabolites include enzymes which are capable of breaking complex carbohydrates, proteins and lipids present within the substrate and/or fermentation medium; vitamins, antimicrobial compounds (e.g. bacteriocins and lysozymes), texture forming agents (e.g. xanthan gums); amino acids, organic acids and flavour compounds.

29.4.3 Carbohydrates

Carbohydrates are the principle substrates for fermentative microorganism. Different acids are produced from sugars which bring down the pH of the fermenting medium and help in absorption of proteins and minerals. During the fermentation of milk for yoghurt or dahi production, about 20-30 % of the lactose is utilized resulting mainly in lactic acid production. Lactic acid and other organic acid like acetate, butyrate, propionate, etc produced during fermentation act as bio-preservative by reducing pH, which inhibits the growth of potentially spoilage and harmful bacteria. Lactic acid also influences physical properties of the food. Lactic acid, the major metabolite of several fermented foods is reported to improve the absorption of calcium and phosphorous besides forming a ready source of energy to the body.

The partial hydrolysis of lactose in milk based fermented foods make them suitable for lactose intolerant people.

29.4.4 Proteins

The native milk proteins, which are known to form hard curd in the stomach, are converted into a soft curd containing finely dispersed casein particles due to bacterial action in fermented products. As a result, fermented milk proteins are particularly useful to children, old people and persons suffering from stomach ulcers.

Any proteins, after fermentation, in general become more easily digestible due to enzymatic actions of microbes. The microbes do part of the work required to be done by the body to digest the proteins and hence, they are easier to digest. During fermentation, the proteolytic action of microbes release some peptides and amino acids. The soluble nitrogen content is higher in fermented foods. The fermented food is also enriched by presence of microbial cell proteins.

29.4.5 Minerals

There are no quantitative changes in mineral content of food as a result of fermentation. However, the fermentation improves the availability of minerals for the body as they are partly modified and are consumed with lactic acid. Fermented milks are excellent source of calcium and phosphorus which are essential for the bones. Further, hydrolysis of chelating agents such as phytic acid during fermentation, improves the bioavailability of minerals. Because of these reasons, fermented foods are recommended to reduce the problem of mineral deficiencies.

29.4.6 Vitamins

During the process of fermentation, the microorganisms need certain vitamins for their own growth. Hence, it is reported that some vitamins of B-complex, orotic acid, etc reduce in fermented foods. However, several bacteria, while growing, synthesize many other vitamins too. There are several reports indicating the increase in the vitamin contents in fermented foods which are supplemented by vitamin producing probiotic bacteria. However, the quantity and quality depends upon the culture and the method of manufacture of the product.

29.5 Therapeutic Value of Probiotic Foods

The therapeutic value of health effect of probiotics can be classified as

• Reducing the risk of a disease.
• Prevention of a disease or disease conditions
• Supportive therapy
• Curative therapy.

The health claims are classified and regulated in most of the countries so as to prevent mis-guiding claims by the manufacturers and suppliers of probiotic products. The health effect of a probiotic can not be generalized, but it is strain dependant. Hence, for each strain of probiotic bacteria, if a health claim is given, it is required to be proved by sound, reliable, clinical trials. Following is the list of possible heath effects of probiotic foods. As the probiotic bacteria, taken orally through food, acts via gastro-intestinal tract.

29.5.1 Role in gastrointestinal tract

• Many Lactic Acid Bacteria(LAB) are normal habitat of GI tract

• LAB have inhibitory activity towards intestinal pathogens

• They regulate intestinal population

• Have the ability to implant in intestinal tract

• Thereby they can control diarrhea, gastric acidity, constipation, inflammatory bowel disease and other diseases too.

29.5.2 Role in cardiovascular diseases

• Some probiotic organisms help in lowering of cholesterol

• Beneficial in controlling cardio-vascular diseases

29.5.3 Bioactive peptides produced from fermented milks are beneficial

• Opiates act as sleep inducers

• Angiotensin converting enzyme (ACE) inhibitors have anti-hypertensive effect

• Platelet aggregation inhibitors

• Antibacterials help in preventing growth of pathogens

• Digestive system regulators help in solving digestive disorders

• Immunomodulators increase specific and non-specific immune response

29.5.4 Anticarcinogenic activities

• Selected LAB exhibit anti-tumor properties in in vivo experiments against human cancer cell lines.

• Animal experiments have shown reduced rate in proliferation of tumor.

• Are most effective against colon cancer by regulating intestinal population.

29.5.5 Immunostimulating effects

• Check translocation of undesirable bacteria through mucosal barriers

• Increase circulating and intestinal antibodies

• Production of specific antibodies

• Increase macrophage activity

• Enhance NK-cell (Natural killer) activity

• Increase T-cell and B-cell activities

• Production of gamma-interferon

29.5.6 Can help aid’s patients

• Fermented milks and Lactobacilli can inhibit the initiation and promotion of tumors

• They can reverse the immunosuppression induced by chemical carcinogens

• They can alleviate the symptoms of AIDS and provide protection against infection

• They can help in control of secondary infections.

29.5.7 Delays the process of ageing

· Calcium availability is higher particularly in fermented milks

· Vitamin D is important for uptake of dietary calcium and in calcium metabolism.

· Protein content is high in fermented milks which is shown to slow down bone loss

· Slows down other age related diseases like impaired lactose digestion, improved immune defense system, less dehydration etc.

29.5.8 Controls and reduces chances of hepatic encephalopathy

• Reduces the content of ammonia in blood by suppressing the enzymes that convert urea to ammonia.

29.5.9. Other possible benefits

• Prevention and treatment of food allergy
• Fermented milks have been found to be very useful for lactose intolerant people.
• Use as oral vaccines
• Control of urinary tract infections
• Degradation of toxins
• Treatment of diseases other than GI tract. Higher intake of low fat fermented dairy products may lower the risk of diabetes in men.
• Local application for control of infection
• Alleviation of depression
• Food fermentations that raise the protein content or improve the balance of essential amino acids or their availability will have a direct curative effect on some of the protein or protein-calories deficiency nutritional diseases.

Now a days, detailed scientific investigations are going on to explain the mechanism of probiosis and also see the effect on specific conditions. Some of the specific areas being investigated are;

• Prevention and/or reduction of duration and complaints of rotavirus-induced diarrhea studies,
• Prevention or alleviation of antibiotic-associated scientific community diarrhea
• Reduction of the concentration of cancer promoting enzymes and/or putrefactive (bacterial)metabolites in the gut effects,
• Prevention or alleviation of allergies and atopic diseases in infants groups,
• Beneficial effects on microbial aberrancies, inflammation and other complaints in connection with: inflammatory diseases of the gastrointestinal tract, Helicobacter pylori infection, bacterial overgrowth,
• Treatment of urogenital infections,
• Prevention of respiratory tract infections (common cold, influenza) and other infectious diseases,
• Amelioration of autoimmune diseases (e.g. arthritis),
• Improvement of the mouth flora, caries prevention,

29.5.10 Safety of probiotics

Probiotics are safe for human consumption. However, depending upon the strain of the organism, rare cases of infection, such as bacteraemia, endocarditis, pneumoniae, septic arthritis and meningitis have been reported, mostly in immunocompromised patients. The risk that probiotic bacteria carrying acquired antimicrobial resistance traits may be horizontally transferable to autochthonous gut microbiota and issues such as virulence and transfer of antibiotic resistance have eaten into the confidence of consumers and the sale of manufacturers.

As these are a very few reported cases of minor safety concern, there is no foundation for safety concerns in relation to probiotic dairy products on the market today. Probiotics are generally considered safe. As evidenced by epidemiologic studies, bacteremia, or sepsis from lactobacilli is extremely rare. Several probiotics have had a long history of safe use and no health concerns have been observed. A long history of safe use is still the most credible safety test. However, it can not be said that probiotics have zero risk.