Study On Removal Method And Mechanism Of Fishy Odor Substances In Evening Primrose Oil

This research is one of the subject research contents of the scientific and technological research project of Jilin Provincial Science and Technology Department（20190301058NY）.Evening primrose oil（EPO）is a dietary supplement with extremely rich nutrients and high content ofγ-linolenic acid.It has a broad market prospect,but the fishy substances limit its further development.So,we taking EPO as the research object,firstly optimize the extraction conditions of its flavor substances,and obtain the best extraction conditions.Then the EPO was irradiated with cobalt 60(⁶⁰Co),the flavor composition was studied by gas chromatography-mass spectrometry（GC-MS）,and the composition of fishy substances in evening primrose oil was explored by combining flavor omics technology The change of the ingredients,and speculate the change rule of its flavor substances.Finally,it was treated with ultraviolet combined with titanium dioxide（UV/Ti O₂）to study the evolution of its fishy substances,explore the changes of physical and chemical properties after treatment,and explore the removal mechanism of the smelly substances of evening primrose oil.The main research content and results of the full text are as follows:（1）Optimization of extraction conditions for volatile components of EPOFirstly,using EPO as raw material,the volatile components in EPO were enriched by headspace solid-phase microextraction（HS-SPME）,and the enriched volatile components were separated and identified by gas chromatography-mass spectrometry.Taking the total peak area of the ion chromatogram as an index,we determined the extraction time（A）,extraction temperature（B）,and equilibrium temperature（C）as three main influencing factors through a single factor,and finally determined the volatility of EPO by response surface experiments.The optimal extraction conditions for the active compounds are as follows:extraction time 35 min,extraction temperature60°C,equilibrium temperature 50°C,equilibrium time 25 min.Under these conditions,the total peak area of the example chromatogram in EPO is relatively high,which indicates that the extraction effect of volatile compounds is better.（2）Effects of ⁶⁰Co irradiation on the volatile components and physical and chemical properties of evening primrose oilUsing evening primrose oil as raw material,by comparing the volatile components of EPO under the irradiation dose of 1,5,10 KGy with the original EPO,it was found that the concentration of the volatile components increased after irradiation,and the ratio of each component also changed.Change.Through principal component analysis（PCA）and cluster analysis（HCA）,we found that the irradiated and unirradiated samples were separated from each other,and the 1 KGy sample showed a good similarity with the unirradiated sample,which indicated that the irradiated the higher the dose,the more significant the effect on the volatile components of EPO.Relying on Orthogonal Partial Least Squares Discriminant Analysis（OPLS-DA）analysis,we found that 1-octen-3-ol is the main substance causing fishy smell,besides,E-2-heptenal and hexanal are also It also plays an important role in the overall flavor of evening primrose oil.The results of color analysis showed that irradiation would increase the brightness value and yellowness value of evening primrose oil,and decrease the redness value,which further shows that the influence of irradiation on evening primrose oil is not only reflected in the trace volatile components,but also Sensory traits also have a certain impact.In addition,the results of sensory evaluation showed that irradiation would lead to deterioration of the flavor of evening primrose oil.In view of the changes in the volatile components of evening primrose oil,we speculated on its formation mechanism.The main reason for the deterioration of the flavor of EPO was the C=C breakage caused by irradiation and the promotion of the combination of broken fragments.（3）Effect of UV/Ti O₂ on the volatile components and physical and chemical properties of evening primrose oilTaking evening primrose oil as raw material,by comparing the volatile components of evening primrose oil after UV/Ti O₂ treatment for 0 min,5 min,15 min,30 min,45 min,60 min,etc.The main components of fishy substances in EPO,such as heptanal,decanal,and nonanal,were significantly reduced.After 60 min of treatment,the concentration of nonanal was only 0.05 mg/kg,and the concentration of（E）-2-octanal was about 20%of the original sample.Combined with its relevant threshold,we analyzed its OAV value,and the results showed that the odor activity value（OAV）value of the key fishy smell substances showed a decreasing trend,which indicated that the importance of fishy smell in EPO continued to decline,and the overall The contribution of flavor is decreasing,and the HCA analysis shows us that the group after5 min treatment is the closest to the original evening primrose oil sample,which shows that the content of flavor substances is the same as that of the original The flavor of EPO was the most similar,which indicated that 5 min of UV combined with Ti O₂treatment had a positive effect on the flavor of EPO.At the same time,we analyzed its antioxidant capacity,fatty acid composition,and quality indicators before and after treatment.The results showed that after a long period of treatment,its antioxidant capacity,TBA value,and iodine value continued to decline,and the 5 min group was the same as the original There is no significant difference in EPO,so it is further explained that 5 min treatment is a more reasonable treatment time,which is also consistent with the results of sensory evaluation.Finally,we analyzed its degradation mechanism.We believe that the decrease in the content of fishy smell substances is mainly due to the production of hydroperoxides with strong oxidizing ability after ultraviolet irradiation,which can effectively promote the decomposition of odor substances.