Lab Report

Title: Practical 4 Enzymatic Browning

INTRODUCTION

When foods like fruits and vegetables are cut or peeled, they release an enzyme from their cells. This enzyme is known as phenolase or polyphenol oxidase and is highly reactive in the presence of oxygen. It catalyzes a biochemical reaction that converts the phenolic compounds present in foods to brown pigments known as melanins. This reaction is known as enzymatic oxidative browning, that renders food the typical black or brown tinge.

In apples the phenolic substrates are present in the flesh and peel. The substrates are chlorogenic acid, caffeic acid, 3,4-dihydroxyphenylalanine (DOPA), p-coumaric acid, flavonol glycosides, 4-methyl catechol, catechin, 3,4-dihydroxy benzoic acid, p-cresol and leucocyanidin. These compounds are substrates for this browning enzyme that finally lead to formation of browning product.

OBJECTIVE

To determine factors that influence enzymatic browning in fruit.

MATERIALS

* Apples

* Water

* 1% salt solution

* 20% sucrose solution

* Sugar

* 1% vinegar solution

* 1% citric acid solution

* Lemon juice

* 1% ascorbic acid solution

* Knife

* Cutting board

* Petri dish

* Stopwatch

PROCEDURES

a. OBSERVATION OF BROWNING REACTION

1. A piece of apple was cut into 6 parts

2. The 1 part was reserved intact.

3. 1 part was bruised.

4. 1 part was sliced.

5. 1 part was crushed.

6. 1 part was placed in cold water

7. I part was placed in hot water.

8. The times taken for the fruit to brown were recorded.

b. CONTROL OF BROWNING REACTION

1. The apple was cut into quarters and then sliced as required.

2. The sliced apples were treated by the following methods:-

* 1% sucrose solution

* 20% sucrose solution

* Sugar

* 1% salt solution

* 1% vinegar solution

* 1% citric acid solution

* Lemon juice

* 1% ascorbic acid solution

3. The times taken were recorded for the...