Spectroscopic studies on thermal degradation and quantitative prediction on acid value of edible oil during frying by Raman spectroscopy.

The health risks posed by harmful substances resulting from the thermal degradation of frying oils are of great concern. Characteristic peak intensity ratios (PIRs) screened from Raman spectra were used to characterize the thermal degradation. High correlation coefficients between PIRs and acid values (AVs) of 0.972 (linear fitting), 0.984 (logarithmic function fitting), and 0.954 (linear fitting) for fried soybean oil, canola oil, and palm oil, were obtained at the PIRs of I1267/I1749, I1267/I1659, and I1267/I1749, respectively. The highly correlated PIRs common to the three oils were determined by Pearson's correlation coefficient combined with heat maps. To accommodate both linear and nonlinear features, a global model for predicting AVs of multi-varieties frying oils was constructed using a least-squares support vector machine algorithm, and the results performed well with a root mean square error of prediction of 0.016 and a ratio of prediction to deviation of 11.351. The whole results demonstrate that Raman spectroscopy could characterize the thermal degradation and has excellent quantitative analysis ability for food control based on AV in frying oils, thus providing a new approach to quality control of frying oils.

Expression of virus-responsive genes and their response to challenge with poly(I:C) at different stages of the annual fish Nothobranchius guentheri: Implications for an asymmetric decrease in immunity.

Aging deteriorates immunity. However, if aging affects immunity in an asymmetric or symmetric way remains largely unknown. In this study we clearly demonstrate that compared with adult fish, the anti-viral responses of aged annual fish Nothobranchius guentheri, as reflected by the expression levels of virus-responsive genes, including lgp2 and mda5 encoding sensor molecules, ifn-i and viperin encoding the effector molecules and irf1, irf7, stat1 and atf3 encoding the regulation elements, are either reduced remarkably or elevated markedly or show little difference depending upon the different tissues. Moreover, although challenge with poly(I:C) results in a significant decrease in the expression of virus-responsive genes in most tissues of aged N. guentheri, it also causes a considerable increase in the expression of the genes in other tissues of aged fish. Collectively, these data suggest that the anti-viral responses of the annual fish N. guentheri generally reduces with age in an asymmetric way among the most tissues.