Rosalee Brown

Many people like fried foods and most foods with fats. However, one gram of fat yields nine calories, compared to the same amount of protein or carbohydrate, each yielding four calories.

One of the most popular uses of oils in food preparation is for frying. The process of frying includes high temperatures that vary from 107°C to 232°C. High temperature is one of the factors that can lead to the deterioration of oils. All oils have what is called a smoke point, which is the point to which it can be heated before it starts to break down. It then reaches the flash point at approximately 315°C where it starts to emit sparks and the fire point at approximately 371°C where it erupts into flames.

Smoke Point

Different oils have different smoke points. Refined oils such as vegetables oil, which are usually a blend of several economical oils with high smoke points, are effective for frying, but an oil such as avocado oil which has a high smoke point is quite expensive.

Rancidity

One of the most obvious ways to identify the deterioration of oil is by its smell and taste. Oils go rancid because of either hydrolysis or oxidation. Rancidity not only affects flavours but can be unhealthy as the process of rancidity can destroy nutrients such as vitamins. Rancid oils can cause indigestion.

The processing of oils, especially those with high smoke points, removes additives such as natural antioxidants. These antioxidants help to retard oxidation. Oils which are cold pressed, that is, they are not subjected to high temperature processing, still have these antioxidants and other natural ingredients intact and are most times sold in dark bottles; they are usually further protected in boxes or other opaque containers from the light. These oils are best refrigerated and the shelf life is shorter than the highly-processed varieties, which are deodorised (all natural aroma and flavour removed) and have an artificial antioxidant added to prevent rancidity.

Useful tips

Choose dishes which require small amounts of oils such as stir frying.

Only heat to required temperature for the recipe, cook and remove from heat quickly.

Use unrefined oils for lower temperature cooking.

When you occasionally shallow fry, which requires more oil and would call for a more economical refined variety, do not overheat and do not reuse unless you are assured you did not get to the smoke point.

To reuse oil, you need to strain through a cloth to remove all foreign particles. If the oil changes colour and consistency it has started to deteriorate.

Bulk cooking can increase the chance of deterioration of oils because of factors such as prolonged heating, additives in the oil, storage and reusing of the oils. The possibility of rancidity also increases with improper storage of meats, which are naturally high in fats. This can lead to indigestion, which I unfortunately experienced recently when I business lunches from the same source twice in the same. Safe cooking with oils should be observed by everyone!

Rosalee M. Brown is a registered dietitian/nutritionist who operates Integrated Nutrition and Health Services; email: yourhealth@gleanerjm.com.