In chemical terms alone, there is a great deal of scope for separating the components in milk and some examples are listed ater removal to produce evaporated or dried products fat separation to produce creams and butter; protein separation to produce cheese or protein concentrates calcium removal to improve stability lactose removal, as a specialised ingredient or for low-lactose products removal of components responsible for tainting raw milk or the cooked flavour of heat-treated milk prodi removal of radionuclides from milk In plant products pesticides and herbicides may additionally be present. Some foods, particularly of plant origin, also contain natural toxins, for example oxalic acid in rhubarb, and trypsin inhibitors, phytates and haemagglutinins in many legumes cyanogenic glycosides in cassava and glucosinolates in rapeseed(Watson, 1987; Jones. 1992). However, the activity of most of these is reduced during normal processing and king metho Foods also contain active enzyme systems. For example, raw milk contains phosphatase, lipases and proteases, xanthine oxidase and many others. Fruits and vegetables contain polyphenol oxidases and peroxidases, both of which cause colour changes in foods, particularly browning, and lipoxygenases, which produce rancid off lavours(Nagodawithana and Reed, 1993) Therefore foods and wastes produced during food processing provide the raw material for extraction of enzymes and other important biochemicals with a range of applications especially in the food and pharmaceuticals industries. Some examples are listed in Table 1. 2. In the biotechnology industry, similar components may be produced by fermentation or enzymatic reactions and require extraction and purification. Perhaps the simplest example is alcohol, produced by a yeast fermentation, where the alcohol concentration that can be produced is limited to about 15 to 20%0, as it inhibits further yeast metabolism Alcohol can be recovered and concentrated by distillation. For low-alcohol or alcohol free beers and wines, there is a requirement to remove alcohol, Again distillation or membrane techniques can be used a wide range of food additives and medical compounds are produced by fermentation these include many enzymes, such as proteases for milk clotting or detergent cleaners, amino acids such as glutamic acid for monosodium glutamate(msG) production, aspartic acid and phenylalanine for aspartame, and lysine for nutritional supplements, organic acids such as citric, gluconic and lactic, and hydrocolloids, such as xanthan gum for stabilising or thickening foods, and a wide range of antibiotics and other medicinal compounds In most cases it is necessary to purify these materials from dilute raw materials, which often requires sophisticated separation techniques. In fact a large proportion of the activities of the biotechnology industry is concerned with separations of this nature, which is known as downstream processing. In general, the products produced by bio- processing applications are more valuable than food products, and it is economicall feasible to apply more complex separation techniquesSeparation processes - an overview 3 In chemical terms alone, there is a great deal of scope for separating the components in milk and some examples are listed: water removal to produce evaporated or dried products; fat separation to produce creams and butter; protein separation to produce cheese or protein concentrates; calcium removal to improve stability; lactose removal, as a specialised ingredient or for low-lactose products; removal of components responsible for tainting raw milk or the cooked flavour of heat-treated milk products; removal of radionuclides from milk. In plant products pesticides and herbicides may additionally be present. Some foods, particularly of plant origin, also contain natural toxins, for example oxalic acid in rhubarb, and trypsin inhibitors, phytates and haemagglutinins in many legumes, cyanogenic glycosides in cassava and glucosinolates in rapeseed (Watson, 1987; Jones, 1992). However, the activity of most of these is reduced during normal processing and cooking methods. Foods also contain active enzyme systems. For example, raw milk contains phosphatase, lipases and proteases, xanthine oxidase and many others. Fruits and vegetables contain polyphenol oxidases and peroxidases, both of which cause colour changes in foods, particularly browning, and lipoxygenases, which produce rancid off￾flavours (Nagodawithana and Reed, 1993). Therefore foods and wastes produced during food processing provide the raw material for extraction of enzymes and other important biochemicals with a range of applications, especially in the food and pharmaceuticals industries. Some examples are listed in Table 1.2. In the biotechnology industry, similar components may be produced by fermentation or enzymatic reactions and require extraction and purification. Perhaps the simplest example is alcohol, produced by a yeast fermentation, where the alcohol concentration that can be produced is limited to about 15 to 20%, as it inhibits further yeast metabolism. Alcohol can be recovered and concentrated by distillation. For low-alcohol or alcohol￾free beers and wines, there is a requirement to remove alcohol. Again distillation or membrane techniques can be used. A wide range of food additives and medical compounds are produced by fermentation; these include many enzymes, such as proteases for milk clotting or detergent cleaners, amino acids such as glutamic acid for monosodium glutamate (MSG) production, aspartic acid and phenylalanine for aspartame, and lysine for nutritional supplements, organic acids such as citric, gluconic and lactic, and hydrocolloids, such as xanthan gum for stabilising or thickening foods, and a wide range of antibiotics and other medicinal compounds. In most cases it is necessary to purify these materials from dilute raw materials, which often requires sophisticated separation techniques. In fact a large proportion of the activities of the biotechnology industry is concerned with separations of this nature, which is known as downstream processing. In general, the products produced by bio￾processing applications are more valuable than food products, and it is economically feasible to apply more complex separation techniques