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Browning reaction

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Enzymatic non enzymatic

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Browning reaction

  1. 1. Food technology Properties of Food Date: 7th Feb Prepared By:Sandesh Neupane
  2. 2. BROWNING REACTIONSBROWNING REACTIONS
  3. 3. -process of becoming brown, especially referring to food. -may be desirable or undesirable. -Browning has an important economic cost, causing deterioration of the value of products in the market of food. Browning
  4. 4. Types of browning reactions (ii)Enzymatic browning (i)Nonenzymatic browning
  5. 5. Non-enzymatic browning -brown color in foods without the activity of enzymes -usually involve sugar or related compounds -Colour and flavour that are often : -desirable as in the crust of bread or - undesirable as in the discoloration of
  6. 6. The two main forms of non- enzymatic browning Caramelization Maillard browning
  7. 7. -Caramelization or sugarbrowning occurs when any of the different types of sugars are heated over their melting points. -When heated by dry heat, granulated sugar will melt at approximately 160oC with continued heating the melted sugar will gradually turn brown to form Caramelized sugar. -The extreme heat pulls water out of the sugar molecule to form furfural derivatives that undergoes Caramelization
  8. 8. Maillard browning -The Maillard browning reaction or carbonyl amine browning is the reaction of the carbonyl group of a reducing sugar and an amino acid or amino group of a protein or peptide. -The reducing sugars, in order of decreasing reactivity are; galactose, glucose,lactose and maltose the most reactive amino acids are lysine, typtophan and arginine.
  9. 9. Enzymatic Browning -Enzymatic browning is a chemical process, involving polyphenoloxidase, catechol oxidase, and other enzymes that create melanins and benzoquinone from natural phenols, resulting in a brown color. -In general, enzymatic browning requires exposure to oxygen, for example the browning that occurs when an apple is cut.
  10. 10. -Phenolases are found in many plants with especially high amount in potatoes mushrooms, peaches, banana, avocado and tea leaves . -However, the browning that occurs in tea leaves is beneficial as it imparts their characteristic colour. -The term tannin describes the polyphenolic compounds that participate in enzymatic browning and also contributes to an a stringent flavor.
  11. 11. What type of Browning involved in Bake product????
  12. 12. Methods used to deter enzymatic browning : 1.Maintaining an acid pH: • retard the activity of the phenoloxidaseenzyme :highest at a pH of 7 and diminishes as the pH decreases below 4. • The lack of activity of this enzyme is seen in fruits that are very acidic such as oranges and grape fruits •Cut fruits may be dipped in acid solution such as lemon juice and orange juice
  13. 13. 2.Use of sulphur: •Sulphur is a chemical commonly used to prevent the darkening of foods. Pineapple juice •prevent melanin formation. Cut lettuce for salad are dipped in a weak sulphur solution to retard browning -done by coating fruits with sugar or immersing them in sugar solutions. - become very mushy, sugar or salt solutions are necessary due to their osmotic pressure. 3.Reducing contact with oxygen:
  14. 14. 4.Antioxidants -Antioxidants, such as ascorbic acid are also effective in reducing browning -they keep the substrate in a reduced state, thereby interfering with the remaining series of reaction that produce brown pigments -Ascorbic acid is found in citrus fruit juices and is available as a commercial product that is sprinkled on the fruit.
  15. 15. 5.Denaturing the enzyme by blanching -Rapidly heating foods by dipping briefly in boiling water will destroy or denature the phenolase enzymes responsible for the reaction with the polyphenolic compounds. -This destruction of enzymes allows frozen foods to retain their color for a longer period of time. -Blanching treatment is done mostly in vegetables such as amaranths, spinach etc.

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