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What is interesterification and Glycaemic Index?

When it comes to cooking, there is a lot to consider when deciding which oil or fat to use. These key questions are answered here
© University of Turin

When it comes to cooking, there is a lot to consider when deciding which oil or fat to use. Plus what is interesterification, Glycaemic Index and how essential are wholegrains?

These important questions are answered below.

What is the difference between extra virgin olive oil, virgin oil and olive oil?

Extra virgin olive oil is the highest grade of virgin olive oil. Both extra-virgin and virgin olive oils, obtained by mechanical pressing, are rich in beneficial substances such as vitamins, phytosterols, and, above all, polyphenols.

Olive oil is a chemically processed virgin olive oil. Olive oils contain a lower amount of the beneficial compounds mentioned above (depending on the refining process).

What fat is better for cooking and frying?

Oils are more resistant to frying if they contain a greater proportion of monounsaturated fatty acids. Olive oil is better than others thanks to its higher oleic acid content, a monounsaturated fat.

Peanut oil also has a high resistance, which makes it ideal for good frying. Heating oil to the smoke point during stir-frying may decrease the amount of polyunsaturated fatty acids because of oxidative degradation. This is the reason why oils rich in polyunsaturated fatty acids are not recommended for frying.

Is margarine a good alternative to other fats?

In the past, margarines were mainly obtained by hydrogenation, a process that converts liquid vegetable oils, depending on the level of hydrogenation (from partial to full hydrogenation) into semi-solid or solid fats in order to make them suitable for food manufacturing purposes.

The hydrogenation process entails the direct addition of a hydrogen atom to the double bonds in the fatty acid chains of the triglycerides. This means the molecule becomes more ‘saturated’ and thus the fat more solid.

Hydrogenated vegetable oils are usually cheaper than animal fat with the same physical properties (e.g. butter); they are more heat-stable and have an increased shelf life.

This process of hydrogenation could lead to the formation of trans fatty acids, which have been linked to adverse health effects.

What is interesterification?

Today, the majority of margarines are obtained by interesterification. Fats can be interesterified, as an alternative to the hydrogenation process, without the formation of trans fatty acids.

In this chemical process, the fatty acid chains are rearranged within or between the triglyceride molecules, creating new triglycerides. The newly formed triglycerides alter the fat’s properties, such as hardness, plasticity and heat resistance.

From a health perspective, trans fatty acids from partially hydrogenated vegetable oils and saturated fatty acids found in margarines should preferably be replaced by vegetable oils rich in monounsaturated and polyunsaturated fatty acids. This is the reason why using liquid vegetable oils is always a better choice.

How many portions of wholegrain food should a person eat daily?

Considering the nutritional value of wholegrains and their high content in dietary fibres, vitamins, minerals and phytochemicals, they should be preferred to refined and processed grains, which have a much lower nutritional quality.

In particular, the guidelines existing in different countries suggest that people should obtain at least half of their daily grain intake from wholegrains.

What is the glycaemic index?

The Glycaemic Index (GI) is a relative ranking of carbohydrate in foods according to how they affect blood glucose levels.

Foods with a low glycaemic index tend to release glucose slowly, whereas foods with a high glycaemic index release glucose rapidly.

You can find an interesting table showing the glycaemic index of the main types of food at the following link:

© University of Turin
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