How can you prevent enzymatic browning

As a result, the necessary components interact and browning starts. This browning reaction actually serves as one of many defense mechanisms of plants.

That said, continued ripening and spoilage of produce will also break down cellular structures. The same goes for the avocado and mushrooms for instance.

In order for step 1 and 2 of enzymatic browning to occur oxygen has to be present. If you store the product in an environment without any oxygen, the reaction cannot take place anymore. It is very common practice to use this when packaging freshly cut lettuce. The same can be done for apple slices.

At home you can immerse them in water, preventing oxygen to come to the apple. In industrial applications by eliminating any oxygen from the package. Since fresh produce will spoil very quickly if it cannot respire anymore, this is not a long term solution. It can work for shorter periods of time, to delay the browning just a little longer.

The activity of the PPO enzymes varies with the acidity of the environment. Some work better and faster at a lower pH-value more acidic whereas others prefer a slightly higher one. This is why recipes for apple dishes say to sprinkle some lemon juice on your freshly cut apples.

It will lower the pH-value slightly, delaying the browning. When making a banana smoothie adding some lemon juice or sour yoghurt will also help to prevent browning. At this temperature the enzymes work fastest. The optimum temperature for PPO various widely for different produce. For cucumber is might be a lot higher than for apples. Generally speaking, storing produce at a lower temperature will slow down enzymatic browning.

Bananas for instance as very sensitive to cold. Storing them in the fridge will result in more damage than the normal browning. In most cases it is better to store it at room temperature and let it be, than place them in the fridge. Instead, no further browning will occur. Giving food a quick heat treatment is called blanching. You may have heard of melanin before. Melanin is the pigment that gives human hair, skin and eyes their colour. Foods are made up of lots of different molecules including some called enzymes.

Enzymes are special proteins which can speed up chemical reactions and act as biological catalysts. They can cause fruit to ripen and over-ripen, which gives the fruit a brown colour.

Fresh fruit and vegetables normally keep enzymes trapped in their tissues. However when the fruit is sliced, or squashed, or when the fruit or vegetable begins to break down with age, the enzymes come into contact with oxygen in the air. This causes the fruit to turn brown. Enzymic browning causes a lot of food waste but it can also be useful: we would not have tea or chocolate without it! If food is kept at higher or lower temperature browning is reduced.

Coagulation of protein occurs during blanching, thereby inactivating the enzyme. When fruit is canned or made into jams or jellies, the browning reaction stops as soon as the fruit is heated sufficiently to denature the enzyme. Change in pH : The optimum pH for polyphenolase activity is between 6. It is also possible citric acid reacts with the copper present in the enzyme. Malic acid also has been found to be effective.

Lemon juice contains both citric acid and ascorbic acid and both are effective. Use of antioxidants: Chemical additives like sulphur dioxide and vitamin C serve to inhibit enzymes , alter enzyme substrates or limit entrance of oxygen. Sulphur dioxide, sulphites and bisulphites inhibit effectively browning. Being a reducing agent sulphite has an additional benefit of preserving the ascorbic acid level.

Bruising on fruit is caused by the same kind of reaction. When fruit is dropped, the cells at the place of impact are damaged and exposed to oxygen inside the fruit causing it to turn brown. Enzymatic browning can also be observed in seafood such as shrimp, crab, and spiny lobster. Enzymatic browning while not harmful can just make the affected fruit or vegetable less appealing to eat.

Luckily there are ways to prevent or delay the browning. Preventing enzymatic browning on fruits. Brushing the surface of fruit with the juice from citrus fruits such as lemons, limes, grapefruits and oranges, you can prevent unsightly browning.

Lemon juice is often the most commonly used for this technique. Soaking in acidulated water: Placing fruit in water that has cider vinegar or lemon juice added to it can help prevent or delay enzymatic browning. The purpose of the lemon juice or cider vinegar is to reduce the pH on the surface of the fruit while the water will help reduce the amount of oxygen that either the fruit or vegetable is exposed to. Do not allow fruits to soak for too long.