CHAPTER ONE
INTRODUCTION
1.0 BACKGROUND OF THE STUDY
Dairy products are generally defined as foods produced from commercially domesticated cows, goats or buffalo’s milk (United Kingdom food Standard Agency, 2009). They are usually high energy-yielding food products. Raw milk for processing of dairy products comes mainly from cows and to a lesser extent from other mammals such as goats, sheep, yaks, camel or horses. Dairy products are commonly found in the European, middle-Eastern and Indian cuisines, whereas they are almost unknown in Eastern cuisines. The United Kingdom Food Standards Agency defined Dairy as “foodstuffs” made from mammalian milk (Bandler and Singh, 2009). Most dairy products contain large amounts of saturated fat and most of them are usually fermented. Examples of dairy products include Cheese, Kefir, yoghurt, etc.
Fermented dairy products, also known as cultured dairy foods or cultured milk products, are dairy foods that have been fermented with lactic acid bacteria such as Lactobacillus, Lactococcus and Leuconostoc. The fermentation process increases the shelf-life of the product as well as adds to the taste and improves the digestibility of milk (Canadian dairy Commission, 2007). There is evidence that fermented milk products have been produced since around 10,000 B.C, and a range of different Lactobacilli strains has been grown in laboratories for a wide range of cultured milk products with different tastes.
Fermented milk products are sour tasting milk products which have been made by either fermenting the milk naturally or by the use of starter culture to produce the desirable milk product. Examples of fermented milk in Africa, Syria, Asia and America are Cheese, nono, buttermilk, yoghurt, irgo, kadam, laban, shenineh, dahi, shirkand, mahi, etc (Ajayi, 2006).
Yoghurt, as a fermented dairy product, is a semi-solid milk product and the best known of all fermented milk products. It is obtained by souring of milk using a pure culture of Lactobacillus bulgaricus and Streptococcus thermophilus (Chandan and Shahani, 1993). It can be manufactured from liquid cow milk, powdered milk and vegetable milk (Soy milk) as base material (Adolfsson et al., 2004). Lactic acid and the other molecules that are formed during fermentation of milk make yoghurt a food product that is both acidic and creamy, appreciated for its taste and nutritional qualities notably for its calcium content (Buttriss, 1997). Yoghurt is thus a very convenient food as compared to milk which is very fragile. Due to the health benefits and taste, it is known to constitute an appreciable proportion of total daily food consumption or even just as a refreshing beverage in several countries (Khan et al., 2008). It is regarded as a nutritionally balanced food, containing almost all the nutrients present in milk and in a more assimilable form (Younus et al., 2002). Yoghurt is a source of highly nutritive protein, energy from added cane sugar, milk fat and unfermented lactose as well as vitamins (Ihekoronye and Ngoddy, 1985). It is actually considered to be more nutritive than milk in terms of vitamins content, digestibility and as a source of calcium and phosphorus (Foissy, 1983). It is believed that yoghurt has valuable “therapeutic properties” and helps in curing gastro intestinal disorders (Adolfsson et al., 2004). It also prevents and controls diarrhoea, capable of modulating the inflammatory response produced by carcinogens, helps in reducing the inflammatory response through an increase in apoptosis.
Yoghurt is characterized as a smooth viscous gel with specific taste of sharp acid and green apple flavor (Bodyfelt et al., 1988). Some yoghurts exhibit a heavy consistency that closely resembles custard of milk pudding, in contrast to others that are purposely soft boiled and are essentially drinkable (Connolly et al.,1984). The most important textural characteristics of yoghurt are firmness and the ability to retain water which is a factor of the type and concentrations of stabilizers used. The type of culture used is also an important factor affecting microstructure and the textural properties of yoghurt (Hussan et al., 1999).
Stabilizers and thickeners are important in several manufactured products and dairy products such as chocolate dressing, milk drinks, ice-cream and yoghurt. These substances prevent separation of various ingredients, increase the viscosity and inhibit the formation of large crystals. Substances used as stabilizers and thickeners include vegetable or tree gums such a gum tragacanth and gum Arabic, agar, cornstarch, gelatin and pectin. Cellulose compounds like methylcellulose and CMC (sodium carboxyl methyl cellulose) are also used (Awan, 1995).
Yogurt is mainly classified based on its chemical composition (full-fat, reduced fat and low-fat), manufacturing method (set and stirred yogurt), flavour type or post incubation process. Yoghurt on the basis of method of production prior to incubation, cooling and final packaging exists as set and stirred yoghurt. Set yoghurt is a type of yoghurt which when produced is incubated and cooled in the final retail package and it is characterized by a firm jelly-like texture (White, 1995). On the other hand, stirred yoghurt is a type of yoghurt that is produced and incubated in a tank and the final coagulum is “broken” by stirring prior to cooling, addition of flavours and packaging (Skriver et al., 1993; White, 1995).
| Project details | Contents |
|---|---|
| Number of Pages | 145 pages |
| Chapter one | Introduction |
| Chapter two | Literature review |
| Chapter three | methodology |
| Chapter four | Data analysis |
| Chapter five | Summary,discussion & recommendations |
| Reference | Reference |
| Questionnaire | Questionnaire |
| Appendix | Appendix |
| Chapter summary | 1 to 5 chapters |
| Available document | PDF and MS-word format |
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