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Browning reaction
- 1. Food technology Properties of Food Date: 7th Feb Prepared By:Sandesh Neupane
- 4. -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
- 5. Types of browning reactions (ii)Enzymatic browning (i)Nonenzymatic browning
- 6. 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
- 7. The two main forms of non- enzymatic browning Caramelization Maillard browning
- 8. -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
- 10. 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.
- 12. 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.
- 13. -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.
- 14. What type of Browning involved in Bake product????
- 15. 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
- 16. 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:
- 17. 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.
- 18. 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.
Editor's Notes
- Photos that can make the concept of browning reaction
- Browning has an important economic cost, causing deterioration of the value of products in the market of food. Caramelization (British English: caramelisation) is the browning of sugar, a process used extensively in cooking for the resulting nutty flavor and brown color. , as in an apple turning brown after being cut.
- Basicallytherearetwotypesofbrowningreactions: (i)Nonenzymaticbrowninginwhichnoenzymesareinvolvedtobringaboutthecolourchanges (ii)Enzymaticbrowninginwhichenzymesareinvolved
- Contrary to enzymatic or oxidative browning, non-enzymatic browning is a chemical process that produces a brown color in foods without the activity of enzymes. The two main forms of non-enzymatic browning are caramelization and the Maillard reaction. Both vary in reaction rate as a function of water activity. Caramelization is the pyrolysis of sugar. It is used extensively in cooking for the resulting nutty flavor and brown color. As the process occurs, volatile Nonenzymaticbrowningreactionsincarbohydratesare:- (i)Caramelization (ii)Maillardbrowning •Thenonenzymaticreactionsusuallyinvolvesugarorrelatedcompounds.Thebrowningreactionsproducechangesin colourandflavourthatareoftendesirable,asinthecrustofbreadorundesirable,asinthediscolorationofdriedmilkproducts.
- chemicals are released, producing the characteristic caramel flavor. The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. The sugar interacts with the amino acid, producing a variety of odors and flavors. The Maillard reaction is the basis of the flavoring industry, since the type of amino acid involved determines the resulting flavor; it also produces toast. Aged white wine with brown color. The wine color is altered with wine aging by reactions between different active molecules present in the wine, these reactions, in general, giving rise to a browning of the wine, leading from red to a more tawny color. Melanoidins are brown, high molecular weight heterogeneous polymers that are formed when sugars and amino acids combine (through the Maillard reaction) at high temperatures and low water activity. Melanoidins are commonly present in foods that have undergone some form of non-enzymatic browning, such as barley malts (Vienna and Munich), bread crust, bakery products and coffee. They are also present in the wastewater of sugar refineries, necessitating treatment in order to avoid contamination around the outflow of these refineries.
- 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 aseries of reactions that are polymerized to brown coloured compounds.
- TheMaillardbrowningreactionorcarbonylaminebrowningisthereactionofthecarbonylgroupofareducingsugarandanaminoacidoraminogroupofaproteinorpeptide. Thereducingsugars,inorderofdecreasingreactivityare;galactose,glucose,lactoseandmaltosethemostreactiveaminoacidsarelysine,typtophanandarginine.
- Theinitialstepisacondensationreactionthatremovesamoleculeofwater.Glucosereactswithanaminogroup(usuallyaprotein)toproduceaglycosylamine. •GlycosylaminesubsequentlyundergoestheAmadorirearrangementtoformaKetone(-C=0)derivativethatcanbefragmentedandpolymerizedintobrownpigmentscalledMelanoidins. Thisreactioncanoccuralsoatroomtemperaturebutitisacceleratedwithhightemperaturesincreasingalkalinity(highpH)andlowmoisturecontent
- Whencertainfruitsandvegetablesarecutorbruised,thetissueexposetotheairquicklydarkens.Bythetimethetissueisexposedtooxygen,phenolicenzymes(phenolases)bringaboutoxidationofthephenolsinthefoodandbrownorgreyblackpigmentscalledmelaninesareformedthereactioninvolvesanumberofcomplexsteps:
- Phenolasesarefoundinmanyplantswithespeciallyhighamountinpotatoesmushrooms,peaches,banana,avocadoandtealeaves. However,thebrowningthatoccursintealeavesisbeneficialasitimpartstheircharacteristiccolour. Thetermtannindescribesthepolyphenoliccompoundsthatparticipateinenzymaticbrowningandalsocontributestoanastringentflavor.
- • An acid pH will retard browning reactions because the activity of the phenoloxidaseenzyme is 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 grapefruits: This fruits do not undergo enzymatic browning. •Cut fruits may be dipped in acid solution such as lemon juice and orange juice
- •Sulphuris a chemical commonly used to prevent the darkening of foods. Pineapple juiceis high in sulphurcompoundsand browning is retarded in cut fruits dipped in this juice. Dried fruits such as apricots and golden raisins, that might turn to unappetizing brown colourare routinely dipped in a sulphursolution or exposed to sulphurfumes as a processing aid to prevent colourchanges. How???prevent browning by releasing sulfite ions, which •prevent melanin formation. CutlettuceforsaladaredippedinaweaksulphursolutiontoretardbrowningThepracticehasstoppedinsomeplacesbecausesomepeoplehaveexperiencedsevereadversereactionstosulphur, semi-liquid, pulpy, pappy, slushy, sloppy,
- This is normally done by coating fruits with sugar or immersing them in sugar solutions. If fruits are just soaked in water, they become very mushy, sugar or salt solutions are necessary due to their osmotic pressure. Antioxidants, such as ascorbic acidare also effective in reducing browning because 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.
- Blanching is an effective means of controlling browning.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 colour for a longer period of time. Blanching treatment is done mostly in vegetables such as amaranths, spinachetc. However, blanching is not a good method for retarding browning in fruits to be eaten fresh as it tends to make them mushy and changes their flavor.