| Rapeseed oil is the second most consumed type of oil in China.Fragrant rapeseed oil is very popular among consumers due to its characteristic flavor,and its consumption accounts for more than 30% of the total consumption of rapeseed oil in China.Roasting and degumming are the key steps that influence the physicochemical properties,minor components and flavor during the current processing of fragrant rapeseed oil,but there are fewer reports of relevant systematic studies.Germination is a novel and effective method widely used for the pretreatment of oil seeds to increase nutrients,but little research has been reported on the effect of germination on the physicochemical properties and minor components of rapeseed oils.In this paper,two main varieties of rapeseeds(Shanyou 28 and Qinyou 10)cultivated in Shaanxi were taken as materials,the effect of germination,roasting,and degumming on the quality of fragrant rapeseed oil was systematically investigated,which could provide a reference for precise and moderate processing of rapeseed oil.The main conclusions are as follows:(1)The oil content and moisture of rapeseeds,and the physicochemical characteristics and minor components of rapeseed oils during germination were systematically determined.The oil contents of rapeseeds of Shanyou 28 and Qinyou 10 were 36.51 ～ 43.49% and 35.51～ 41.93%,respectively,with a slight increase and then a continuous decrease during germination.The peroxide values of the two oils were 0.13 ～ 0.49 mmol/kg and 0.09 ～ 0.58mmol/kg;the acid values were 0.64 ～ 3.51 mg KOH/g and 0.47 ～ 1.92 mg KOH/g;the contents of unsaturated fatty acids were 91.86 ～ 92.10% and 92.01 ～ 92.31%.In the two rapeseed oils,α-tocopherols were 234.24 ～ 693.62 mg/kg and 269.56 ～ 681.09mg/kg,which increased as germination proceeded.The total tocopherols were 680.42 ～ 939.31 mg/kg and 771.10 ～991.85 mg/kg.The total phytosterols were 1884.02 ～ 2071.55 mg/kg and 1723.01 ～ 2691.72mg/kg.Therefore,germination is an effective pretreatment for increasing tocopherols and phytosterols in fragrant rapeseed oil.(2)The physicochemical properties,minor components and volatile flavor compounds of fragrant rapeseed oils prepared under different roasting conditions were comprehensively analyzed.The acid values of Shanyou 28 and Qinyou 10 rapeseed oils were 1.05 ～ 2.21 mg KOH/g and 1.04 ～ 1.97 mg KOH/g,respectively.The total tocopherols were 696.13 ～ 721.16mg/kg and 809.76 ～ 844.56 mg/kg;the total phytosterols were 1996.42 ～ 2031.35 mg/kg and1835.75 ～ 1945.47 mg/kg.Roasting significantly increased phenols and flavonoids(p < 0.05),with phenols increasing by 1.35 ～ 24.40 times and 1.21 ～ 20.96 times,and flavonoids by 0.97～ 21.41 times and 0.78 ～ 4.03 times,respectively.In the two rapeseed oils,the total volatile compounds were 19.02 ～ 905.01 mg/kg and 22.68 ～ 1193.28 mg/kg,respectively,with 3.88 ～223.83 mg/kg and 7.79 ～ 376.38 mg/kg of glucosinolate degradation products,4.38 ～ 519.89mg/kg and 7.04 ～ 634.84 mg/kg of heterocyclic compounds and 14.89 ～ 155.08 mg/kg and14.17 ～ 170.17 mg/kg of oil oxidation products,all of which increased with the increase of roasting temperature.Roasting increased the content of minor components in fragrant rapeseed oils,with the most significant increase in phenols and flavonoids.(3)The physicochemical properties,minor components,and volatile compounds of fragrant rapeseed oils degummed under different conditions were determined comprehensively.Different amounts of phosphoric acid solution(6%,w/w)were added to rapeseed oils for degumming,and the highest degumming rate of 98.16% and 98.61% was achieved with the addition of 5%.The peroxide values of Shanyou 28 and Qinyou 10 rapeseed oils were 0.14 ～0.45 mmol/kg and 0.14 ～ 0.35 mmol/kg,respectively;the acid values were 1.16 ～ 1.52 mg KOH/g and 1.99 ～ 2.46 mg KOH/g.After degumming,chlorophylls in oils were reduced by15.38 ～ 20.67% and 12.06 ～ 62.31%;carotenoids were reduced by 5.86 ～ 7.77% and 23.18 ～27.20%.The L* value increased,the a* value decreased,and the b* value increased after degumming.Degumming decreased tocopherols in Shanyou 28 rapeseed oils by 3.48 ～ 5.82%.Phytosterols were reduced by 4.22 ～ 6.63% and 5.03 ～ 6.62%,phenols by 1.74 ～ 4.97% and6.23 ～ 9.33%,and flavonoids by 0.98 ～ 8.83% and 3.29 ～ 6.84% in the two rapeseed oils.The volatile compounds were 60.65 ～ 147.26 mg/kg and 62.63 ～ 101.93 mg/kg,respectively.with12.29 ～ 44.76 mg/kg and 21.26 ～ 32.85 mg/kg of glucosinolate degradation products,26.07 ～58.41 mg/kg and 23.98 ～ 30.08 mg/kg of heterocyclic compounds,and 13.49 ～ 44.09 mg/kg and 16.27 ～ 30.08 of oil oxidation products.Degumming removed phospholipids in oils,improved the color,but caused partial loss of minor compounds and volatile compounds. |
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