STARTER CULTURES AND FERMENTED MILK PRODUCTS

Module 1. Introduction

Lesson 1
INTRODUCTION TO STARTER CULTURES AND FERMENTED MILKS

1.1 Introduction

Starter cultures are those microorganisms that are used in the production of cultured dairy products such as dahi, yogurt and cheese.

The organisms selected for this purpose need to produce the desired effect in the finished product.

Starters are a group of active and desirable microorganisms capable of bringing about desirable changes in the milk product through the process of fermentation. These are carefully selected microorganisms that are deliberately added to milk to initiate (‘start’) and carry out the desired fermentation in the production of fermented milk products. In other words starters bring about the specific changes in the appearance, body, texture and flavour characteristics of the final product.

The natural microflora of the milk is inefficient, uncontrollable and unpredictable, or is destroyed altogether by the heat treatments given to the milk. A starter culture can produce particular characteristics in a more controlled and predictable fermentation when added to milk.

The most common use of starter cultures is for the production of lactic acid from lactose (milk sugar), which in most cases causes or assists in the coagulation of milk protein by lowering pH of milk. Cultures that produce lactic acid are generally referred to as “lactic acid bacteria” (LAB). Certain starter organisms are added specifically for their ability to produce flavour compounds such as diacetyl. Starter organisms can also influence texture of cultured and/or aged products through the breakdown of proteins, fats and other milk constituents in addition to the pH effect. The lower pH of cultured products can be inhibitory to certain spoilage organisms, although inhibition is associated with other by-products of growth with some starters.

More recently, probiotic cultures are finding their way into cultured milk products. These organisms possess some claimed health benefit for the consumer, e.g., better digestion, anti-cancer compounds, and prevention of heart disease etc. Probiotic cultures may be added as adjuncts or they may be directly involved in the fermentation process.

1.2 History of Starter Cultures and Fermented Milks

Fermented foods are of great significance since they provide and preserve vast quantities of nutritious foods in a wide diversity of flavours, aromas and textures, which enrich the human diet. Over 3500 traditional, fermented foods exist worldwide. Fermented foods have been with us since early ages and of these fermented milks have long been an important component of nutrition and diet. Originally fermented milks were developed as a means of preserving nutrients (Milk and other products).

When our ancestors acquired the knowledge to use milk, they also learnt how to use lactic acid bacteria (LAB) in dairy products even though they did not know about the existence of microorganisms. When milk was left at room temperature, it was spontaneously fermented and was used as such or after dilution with water.

As an alternative fermented mix could be concentrated by drainage of whey, resulting in a new product, which could be stored for several months: the first cheese. Owing to this long period of consumption, such products were found to be safe and healthy. By trial and error, the practice of inoculating milk with a small amount of previously fermented milk was developed. Heating the milk before inoculation increased the quality of the product and it became possible to develop a range of specific, traditional fermented milk products.

About two hundred years ago, cheese and butter production became industrialized. Traditional products were standardized and slightly modified to adjust them to industrial production. Starters were grown in manufacturing plants, but, as the size of the operations grew, the importance of standardized starters increased. In the late 19th century companies with specialized in the starter production were founded. In the beginning the constraints were that, the starters were still undefined, containing an unknown mixture of different strains of the suitable species. Later on, starters were analysed and defined, allowing them to be composed of specific strains with selected properties selected to give a standard product. In general, defined starters are composed of some specific strains with less species variety than undefined starters, and do not usually contain yeast.

1.3 Consumption and Production Statistics

Table 1.1 Consumption statistics of fermented milk products

Country	Kg/ head
Year	2001	2002	2003	2004
Denmark	37.0	40.7	43.0	44.6
Germany	26.1	27.0	28.5	28.9
France	20.5	21.1	21.9	21.9
EU 15	18.2	18.1	19.3	19.6
Czech republic	14.3	14.1	14.8	14.9
Cyprus	11	10.8	10.8	10.9
Hungary	11.5	11.9	14.3	15.4
Poland	8.7	11.1	11.5	11.9
10 new EU member countries	9.1	10.5	10.7	11.1
EU 25	16.7	17.5	17.9	18.2
Iceland	34.0	35.2	36.3	40.7
Norway	19.0	20.0	20.7	21.1
Switzerland	24.2	23.7	25.6	27.0
Canada	5.2	5.7	6.2	6.7
Mexico	3.1	3.2	3.8	3.9
Argentina	7.3	6.8	7.3	9.4
South Africa	3.2	3.2	1.3	1.5

The manufacture of cultured dairy products represents the second most important fermentation industry only after the production of alcoholic drinks.

The consumption of milk drinks and fermented products has been recently reviewed by the International Dairy Federation, as shown briefly in the above Table-1.1. It is quite clear from the data that the consumption of fermented milks has generally increased around the globe over a period from 2001 to 2004. According to another report by Euromonitor a global market analyst, largest fermented dairy market till 2003 was Japan, where the leading brand Yakult is the reference product for the entire category, having been available in Japan for more than 50 years. The next most significant markets are South Korea and Brazil, followed by a number of Western European markets including US probiotic drinking yoghurts, booming on the basis of their portability, snack appeal and health claims which match those of fermented dairy drinks; offering improvement to digestive health and a boost to the immune system.

In the Indian subcontinent also, fermented milk products such as dahi (curd), Lassi (sweetened yoghurt drink like product), buttermilk and shrikhand (drained curd added with sugar and flavoring) figure prominently in people’s diet. The demand for fermented milk products is increasing and it has been estimated that about 10% of total milk produced in India is used for preparation of traditional fermented milk products. Dahi is an age-old indigenous fermented milk of India and has retained its popularity in Indian diet despite changing lifestyles and food habits. About 6.9% of total milk produced in India is utilized for making dahi intended for direct consumption.

1.4 Advantages of Milk Fermentation /Role of Fermentation in Food

i) Enrichment of human diet through a wide variety of flavours, aroma and texture of foods

ii) Preservation of foods via lactic acid, alcoholic, acetic acid and alkaline fermentations

iii) Bio-enrichment of food substantially with proteins, essential amino acids, Essential fatty acids and vitamins

iv) Detoxification during food fermentation processing

v) Nutritional and physiological benefits such as

• Promotion of growth and digestion
• Settling effect on the GI tract by deceasing harmful bacteria
• Improvement of bowel movements
• Suppression of cancer
• Suppression of blood cholesterol
• Suppression of tumours
• Catering to the needs of lactose intolerant people

1.5 Scope for Fermented Milk Industry

Over the past century, voluminous scientific knowledge has been well established regarding the technological aspects of fermented milks, including the physiology of starter cultures and related probiotic microflora. It is also very important to preserve this pool for future application. It is necessary to have better understanding of enzymic pathways in these starters in order to be able to select strains with specific, desired characteristics. Among various milk products the fastest market growth at almost six times to that of total dairy sector growth was observed for probiotic based fermented milk products during the last one decade. The increasing demand from consumers for dairy products with 'functional' properties is a key factor driving value sales growth in developed markets. This led to the promotion of value-added products such as probiotic and other functional yoghurts, reduced-fat and enriched milk products and fermented dairy drinks and organic cheese. Another important global trend observed is the increasing demand for consumer convenience. Present day consumers prefer foods that promote good health and prevent disease. Furthermore, these foods must fit into current lifestyles providing convenience of use, good flavour, and an acceptable price- value ratio. Such foods constitute current and the evolution of the food development cycle.

It is evident that the market for fermented milks is booming especially for probiotics and those with special added ingredients. 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. Producers and marketers of cultured milks are making every effort to keep them growing through product development and packaging innovations suited for all occasions of gastronomic indulgence with supporting scientific documentation; a health claims strategy and successful presentation.

.Appropriate international definition(s) of yoghurt and other fermented milks including other probiotic products are required to show the relationship between food, intestinal bacteria, human health and disease in the field of probiotics along with properly designed clinical studies to establish the proper health benefits to humans. Many a times in vitro results cannot be found in vivo, and observations reported in animals cannot be translated directly to humans; there are problems in generalizing the results in the given types of microorganisms used, thus more number of clinical studies should be conducted on humans of different races in different countries to properly substantiate the health benefits in humans. New product categories, containing difficult raw materials with regard to technology of probiotics, will certainly be the key research and development area for future functional food markets.

There are products with complete supplementation offered as medical foods, as well as healthy products for people who have problems obtaining all the nutrients they needed. It is clear from the literature that new kinds of fermented milks containing various nutrients are being tested as curatives for specific diseases and are approaching medical food effectiveness in conventional food format and will continue to be introduced to the food supply. The occurrence of diet-related diseases of deficiency and excess, points to the importance of the development of functional foods. Functional food science must be viewed world over beyond the short-term commercial prospects and should be considered for long-term research and development.