# Prediction of Walnut Deterioration Using Kernel Oxidative Stability
## 3 Results and Discussion
### Shelf-Life Prediction, and Temperature Coefficient, and Q\({}_{10}\) Number Calculation  
Choosing the most suitable operational parameters for foods with different composition and matrix is important for the application, accuracy, and reproducibility of accelerated oxidation methods. In addition, it was previously demonstrated that susceptibility to oxidations in different levels of n-3 PUFA-rich oils such as algae and fish using Rancimat method and chemometric analysis can be accomplished [3]. Thus, a reliable accelerated oxidation method for walnut kernels would be useful and valuable information to distinguish the susceptibility to oxidations. A linear regression between the logarithm of kernel OSI at three different temperatures and temperature coefficients were calculated to predict shelf-life using the accelerated method (Table 2). Significant linearity was found for each airflow, with R\({}^{2}\) of 0.997, 0.989, and 0.988, respectively. The temperature coefficient (T\({}_{\text{coeff}}\)) represents the factor by which the rate (R) of a reaction increases for every 10-degree rise in the temperature (T), which in our case indicates the slope of our linear relations. T\({}_{\text{coeff}}\) showed similar values from 15 and 20 L h\({}^{-1}\) (-3.7 and -3.9, respectively) but lower values at the highest airflow (-3.3). The decrease rate of OSI with a 10 \({}^{\circ}\)C increase in temperature from this study is much higher than 2, the rate found in oils and edible fats in previous studies [6; 20]. The low curve slope at an airflow 25 L h\({}^{-1}\) determined a lower OSI\({}_{22}\) and Q\({}_{10}\). OSI\({}_{22}\) indicates the oxidative stability of samples if measured at 22 \({}^{\circ}\)C. This value represents an estimation of the time required for the samples to reach oxidative stability if exposed at 22 \({}^{\circ}\)C of storage, which is the temperature of exposure of most products in-store shelves. The highest value was found for airflow at 15 L h\({}^{-1}\), and the most conservative shelf-life prediction was given by airflow at 25 L h\({}^{-1}\). These results suggest that the airflow influences the shelf-life prediction for walnut kernels using the Rancimat method. Q\({}_{10}\) is the factor by which the rate increases when the temperature is raised by ten degrees. In this study, an airflow of 15, 20, and 25 L h\({}^{-1}\) had Q\({}_{10}\) of 2.4, 2.5, and 2.2, respectively. These results are in accordance with previous studies on oil and ghee using the same temperature ranges [5; 21]. When increasing the temperature of analysis by 10 \({}^{\circ}\)C, accelerated oxidative reactions and OSI are halved. The possibility to decrease OSI by increasing temperature may give decrease time of analysis which may be important as OSI in kernels (Table 1) is much higher than the OSI in oil [22]. This method is simple and does not require a trained scientist so it can be done easily in-house at processing facility, an advantage compared to other oxidative methods commonly used in kernels, such PV, volatile compounds or sensory evaluations.