CHAPTER ONE
1.0 INTRODUCTION
Fermented milk products are very popular products and new varieties are regularly entering the consumer market. Most commonly used fermented dairy products are the sour cream, buttermilk, ropy milk, acidophilus milk, cheese and yoghurt.
Yoghurt is the most popular and ideal food representing pleasant aromatic flavor thick creamy consistency and several health benefits (Huma et al., 2003). It is made in variety of composition either plain or with added substances such as fruits, sugar and gelling agents. Yoghurt is a fermented food product produced by lactic acid fermentation of milk, generally by mixed cultures of lactic acid bacteria (Chan dan, 2006). Some Yoghurt contains live beneficial bacteria (probiotic) and it is rich in protein, fat. Calcium, Riboflavin, vitamin B6 and vitamin B12.
Appearance and physical characteristics are important quality parameters of yoghurt (Amata et al., 2006).
Stabilizers are used to improve the consistency, viscosity of yoghurt and reduce syneresis rate (Lucey 2002). Gelatin, starches, pectin, alginate, carrageenan, derivatives of methyl cellulose, gum Arabic tragacanth, karaya, locust bean gum (LBG), guar and xanthan gums are some of the compounds used as stabilizers in yoghurt (Tamine and Robinson 1985). These stabilizers improve the consistency and dispersion properties of spray dried yoghurt powder in water, (Ramirez et al; 2002). Stabilizers such as carboxymethyl cellulose (CMC), LBG, alginate or sugar gum can be used as thickener in conjunction with a stabilizer such as carrageenan to reduce syneresis (Hansen, 1993). Use of soluble fibers as stabilizers has some advantages due to their beneficial effects for human health (Labell, 1990). Coronary disease, hypertension, diabetes, hypercholesterolemia and gastro intestinal disorder may decrease or be prevented by consuming fibre in the diet (Dello et al., 2004). Some stabilizers not only stabilize the product but also used as fat replacers like malodextrin which gives better taste, appearance and also reduce syneresis (Parveen, 2004).
1.1 PROBLEM STATEMENT
There are some common problems in the production of yoghurt such as syneresis, improper texture, lower shelf life, sourness, acidity and hardness. (Debrandere and Debaerdemaeker, 2002; Lee and Lucey, 2010).Synersis is the major problem which reduce the shelf life of yoghurt and it might be reduced by increasing the casein content of the milk, reducing the incubation temperature (Lucey 2001; Answer et al; 2013) and rate of acidification (Fiszma et al; 1999) or by adding appropriate stabilizers which interacts with the casein network.
In general stabilizers tend to have varying impacts on the yoghurt quality besides improving consistency.
1.2 JUSTIFICATION OF STUDY
In today’s health conscious society, low and non-fat yoghurt products have become extremely popular and different stabilizers are used in these production. These provides body and mouth feel to create a smooth delicate, creamy texture while providing an attractive surface sheen in addition to the texture enhancement, stabilizers improve customer appeal by preventing syneresis and extending shelf life.
The consumption of yoghurt in Nigeria has increased during the last decade and its taken as dessert or refreshing beverage drink. The quality of yoghurt in local market varies from one product to another. Poor quality milk, unhygienic practices associated with the process involved and all kinds of stabilizers give rise to poor grade yoghurt. (Younus et al; 2002). It is therefore important to carry out an investigation of the effect of stabilizers on yoghurt quality to ascertain appropriate brands for light yoghurt quality production.
1.3 OBJECTIVE OF THE STUDY
The broad objective of this research is to study the effect of various stabilizing agents on yoghurt quality. The specific objective includes;
- To produce yoghurt from cow milk using different stabilizers.
- To evaluate physiochemical and organoleptic properties of the yoghurt.
- To evaluate the shelf stability of the yoghurts.
- To conduct statistical analysis of the data obtained to ascertain the best sample.
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