Properties of oil extracted from oat grains before and after the roasting process conducted under different conditions

Oat is widely cultivated around the world. The global production of oat increased by 10.65% from 2019 to 2020, reaching 25.33 million metric tons in 2020. It has always been considered a valuable crop due to its nutritional properties. Oat grains are an excellent source of protein, fibre, minerals and fats. They contain at least twice as much fat as other common cereals, such as wheat, barley or rye, and the fat contained in oat grains significantly contributes to its properties, including improved calorific value and nutritional quality.

Heat treatment, particularly roasting, has long been considered the essential method of processing grains, as roasting effectively extends shelf life and provides a pleasant roasted flavour.

The aim of the current investigation has been to evaluate and compare the calorific value of oat grains and the qualitative characteristics of oil obtained from raw grains and grains roasted in different conditions. Roasting has been conducted at 100°C and 130°C in a laboratory oven for 20 and 40 minutes at each temperature, respectively, that is under four different conditions in total. The calorific value of the whole oat grains has been determined using calorimetry. The oil from oat grains has been extracted with hexane. The fatty acid composition has been determined by gas chromatography. The retention times of the standards have been applied to identify fatty acids present in grain-extracted oils. Acid values and peroxide values of oils from fresh and roasted grains have been determined by titration. A differential scanning calorimeter coupled with a high-pressure cell has been used to define the oxidative stability of oils.

The results of the calorimetric study have confirmed that oat grains are an excellent energy supply. The oils extracted from the oat grains, both fresh and roasted, contain more than 40% of polyunsaturated fatty acids, which is beneficial from nutritional point of view. However, high level of unsaturation results in low oxidative stability. The roasting process conducted under different conditions has not affected either the composition of fatty acids or the oxidative stability at a statistically significant level.