| Idesia polycarpa has been listed as one of the important woody oil crops for development in China.Both pulps and seeds of Idesia polycarpa can be used for oil production.Currently,the oil is mainly extracted from the fruit,and there is a lack of suitable drying pretreatment and oil refining processes that are adapted to the characteristics of the oil crop.Therefore,it is urgent to develop suitable oil extraction and refining technologies for Idesia polycarpa.To this end,this study determined the character indexes,oil content and fatty acid composition of Idesia polycarpa pulps and seeds of representative regions at different harvesting times,compared the composition of Idesia polycarpa pulp oils(IPPO)and Idesia polycarpa seed oils(IPSO)of different regions at the optimal harvest period,determined the drying pretreatment of the oil crop and established and optimized the oil extraction and refining process.The main research contents are as follows:Firstly,the character indexes,oil content and fatty acid composition of the pulps and seeds of Idesia polycarpa from five representative production areas at different harvesting times were determined.The results showed that the fruit character index of Idesia polycarpa was the best from October 15 th to November 1st.The oil content of Idesia polycarpa pulp ranged from 12.29% to 40.09%,Idesia polycarpa seed oil content ranged from 5.41% to21.48%,linoleic acid content of IPPO ranged from 57.31% to 73.28%,and linoleic acid content of IPSO ranged from 75.04% to 81.93% under different regions and harvesting times.As the harvest time was delayed,the oil content of the pulp first increased and then decreased,and the highest oil content appeared from October 15 th to November 1st.The seed oil content showed a general downward trend,with a significant decline in November.The linoleic acid content of the fruit oil gradually decreased as the harvest time was delayed,with a significant decline after entering November,while the fatty acid composition of the seed oil did not change significantly.Accordingly,the optimal harvesting period of Idesia polycarpa was confirmed to be from October 15 th to November 1st in Ningqiang City,Shaanxi Province,Xinyi City,Guizhou Province,Xuancheng City,Anhui Province,Mianyang City,Sichuan Province and Liangshan City,Sichuan Province.Secondly,the trace concomitant contents and free radical scavenging ability of IPPO and IPSO from different regions were measured under the optimal harvesting time.The results showed that the IPPO from Xingyi region had the highest contents of total tocopherols(1490.20 mg/kg),total sterols(3023.31 mg/kg)and squalene(2438.17 mg/kg),and the strongest free radical scavenging ability of FRAP(280.94 μmol TE/100 g of oil)and ORAC(212.37 μmol TE/100 g of oil).The highest content of polyphenols(266.50 mg GAE/kg),ABTS(387.88 μmol TE/100 g oil)and DPPH(288.01 μmol TE/100 g oil)free radical scavenging ability was found in Ningqiang region.In seed oil,the highest total tocopherol(447.91 mg/kg)and squalene(1797.96 mg/kg)contents were found in Mianyang,while the highest polyphenol content(231.46 mg GAE/kg)was found in Xingyi,the highest total sterol content(4246.81 mg/kg)was found in Ningqiang,and the strongest DPPH(175.02 μmol TE/100 g oil)and FRAP(145.31 μmol TE/100 g oil)free radical scavenging capacities were found in Xuancheng,with the strongest ABTS(245.18 μmol TE/100 g oil)and ORAC(163.40 μmol TE/100 g oil)free radical scavenging capacities.Principal component comprehensive scores showed that the scores of pulp oil were higher than those of seed oil,and Xingyi pulp oil had the best evaluation and the highest nutritional value.Thirdly,the physicochemical indexes and micronutrient composition of the pulp oils obtained after fresh pressing,sun-drying and oven-drying Idesia polycarpa were compared,and the oil extraction from the pulp pomace after fresh-pressing was optimized using aqueous enzymatic extraction.The results showed that the freshly pressed oil had the lowest acid value and peroxide value and the highest degree of nutrient retention,followed by the sun-dried oil,while the oven-dried oil had the poorest quality.Based on the advantages of fresh pressing,an overall oil production process for Idesia polycarpa was developed,which included whole fruit fresh-pressing,seed separation,and aqueous enzymatic treatment of pulp pomace.The optimized aqueous enzymatic extraction conditions were an enzyme digestion p H of 4.0,enzyme addition of 1%,digestion temperature of 55°C,and digestion time of 4 h.The oil extraction rate reached 94.14%.Finally,the refining process was optimized for the characteristics of dark color and high impurity content of IPPO.The results showed that the optimal degumming process involved a water addition of 12%,phosphoric acid addition of 0.05%,degumming temperature of 50°C,and degumming time of 25 minutes,achieving a degumming rate of 93.20%.The best process for decolorization was 95:5 ratio of activated white clay and activated carbon,7.2%decolorizer dosage,112°C decolorization temperature and 42 min decolorization time,achieving a decolorization rate of 93.61%.In summary,this study determined the optimal harvesting period of Idesia polycarpa,compared the quality of IPPO and IPSO from different regions in the optimal harvesting period,investigated the influence of different pretreatment methods on the quality of IPPO,established the overall process of Idesia polycarpa oil production,optimized the oil extraction process of pulp pomace and pulp oil refining process,and provided technical support for Idesia polycarpa harvesting,preprocessing,oil extraction and refining. |
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