Food Science and Processing

FOOD SCIENCE AND PROCESSING 3 (2+1)

Lesson 12 : Composition, Nutritive Value and Processing of Nuts and Oil Seeds

Processing of fats and oils

• Fats and oils do not occur in free nature. Present in animal tissues, plant seeds, fruits.
• They are isolated, refined, processed for specific use.
• Fats extracted from
• Animal tissues by rendering
• Other sources by
• Pressing and
• Solvent extraction

1. Production and Processing methods


2. Plasticity: At room temperature most of the fats and oils contains solid fat crystals and liquid oil. Liquid part is held in a network of small crystals of which fat can be moulded or pressed in to various shapes without breaking. This property of fat is called as plasticity. Plastic fats can be creamed by incorporation of oil. The size and type of crystal in plastic fat influences the performance of fat in backed products and pastry.


3. Hydrogenation
   Refined oil on storage becomes, rancid due to deteriorative changes in unsaturated fatty acids (USFA). Therefore refined oils are hydrogenated by passing H2 under pressure through hot oil in presence of catalysts like nickel.
   The quality of final products depends on
   • Temperature
   • Rate of mixing of H2
   • Nature of catalysts
   • Pressure of H2
     • The fat will be neutral in flavour
     • High smoking temperature, therefore will have good shortening power
     • High stability
     • Low undesirable flavour

     Vansapathi: Vanaspathi is an hydrogenated oil containing 95% hydrogenated oil and 5% liquid oil . Sesame oil in olden days is used as Vanaspathi . At present more non traditional oils are used as Vanaspathi.

4. Winterization: Some oils become cloudy when kept in refrigerator because the triglyceride (TG) molecules in oil have higher melting points than other molecules in one mixture. The oil filtered to separate crystals is used as salad oil, As it is having lower melting point , it is used in salad dressings.