# Investigation of Oil Extracted from Roasted and Unroasted Oats with Use of Chemometrics
## 3 Results and Discussion
### Calorimetry  
Although several methods have been attempted to analyse and monitor the lipid oxidation process, single methods are the only ones capable of accurately monitoring the results of these complex oxidation reactions [32]. The pressure differential scanning calorimetry (PDSC) method was used to measure the oxidative stability of the oil, as determined by the oxidation induction time (OIT). Generally, the stability of oil increases as the OIT period increases. In a recent study [12], researchers used PDSC and FTIR techniques to analyse the oil extracted from roasted hemp seeds. They determined the oxidative induction time from the PDSC curves. After roasting at higher temperatures, samples of oil extracted from hemp seeds were characterised by lower induction time than oil from hemp seeds roasted at lower temperatures. The data in Figure 1 confirm that even a short roasting time affects the OIT of the oil. Surprisingly, the oil extracted from oats roasted for 10 min showed a higher OIT than the unroasted oil. The statistical difference between the results ruled out the possibility of experimental error. Longer roasting times have resulted in lower OIT, as seen in Figure 1 and confirmed by visual inspection. The data obtained with PDSC were statistically correlated with spectral data, as presented in Section MODEL 3: Induction Time and Spectral Data. The roasting time influences the levels of thermally unstable compounds found in oils, such as phosphatides, mono- and diglycerides, fatty alcohols, sterols, and fat-soluble vitamins (like vitamin A and vitamin E). As the roasting process progresses, the content of these compounds decreases because they decompose when exposed to heat. Consequently, the oxidation induction time (OIT) and oxidation stability (OS) increase as compared to unroasted grains (green bar in Figure 1). This is because these compounds can act as catalysts in the oxidation process; therefore, when their levels are lower, the oxidation process slows down, resulting in higher OIT and OS values. Additionally, the acid value decreases, likely because free fatty acids react with free mono- and diglycerides to form esters. The esterification and hydrolysis reactions are reversible and governed by equilibrium. When heated, some water is removed, causing a shift in the equilibrium toward the formation of esters, according to [PERSON]'s principle. As a result, there is a lower concentration of free fatty acids after roasting. Figure 1: Oxidation induction time (OIT) of roasted and unroasted grains’ oil. * Different letters indicate that the samples differ significantly at \(p<0.05\). The reaction can be represented as follows:  
\[\text{R}_{1}\text{COOH}+\text{R}_{2}\text{OH}\rightleftharpoons\text{H}_{2} \text{O}+\text{R}_{1}\text{COOR}_{2}\]  
This Equation illustrates that a carboxylic acid and an alcohol are at equilibrium with an ester and water. For hempeseed oil, authors [12] studied the effect of different roasting temperatures (lower and higher) on hemp seeds on the OIT but not the impact of roasting in different time intervals at the same temperature. Classical calorimetry, also known as calorimetric bomb, was used to determine the calorific value of oat grains and the impact of the roasting process on their change. This study examined the effect of temperature treatment on the calorific value of whole oat grains. It concluded that the calorific value of samples roasted at 160 \({}^{\circ}\)C for different durations increased systematically, with the samples roasted for 60 min having the highest calorific value. The data are presented in Figure 2, where calorific values, given in kJ \(\times\) kg\({}^{-1}\), are plotted against 0, 10, 20, 30, 40, 50, and 60 min of roasting. The calorific values at different times are significantly different from each other. It has been concluded that the calorific value of samples roasted at 160 \({}^{\circ}\)C is statistically higher with the heat treatment than the unroasted samples.