| China is a country with a serious shortage of edible vegetable oil and protein resources.At present,the edible oils on the market are mainly composed of long-chain unsaturated fatty acids.Long-term excessive consumption can easily lead to a series of metabolic diseases such as diabetes and cardiovascular diseases.Cinnamomum camphora seed kernel is rich in medium-carbon chain oil(58%)and protein(18%),which can be used as an effective supplement to edible plant oil and protein in China,and needs to be developed and utilized urgently.A large number of studies have shown that the different extraction methods will affect oil active substances,volatile components and protein properties.Therefore,in this study,Cinnamomum camphora seed kernel was taken as the raw material,and the Cinnamomum camphora seed kernel crude oil(CCSKO)was extracted using hot pressing,cold pressing,solvent extraction,aqueous extraction,sub-critical fluid extraction and supercritical fluid extraction.The effects of extraction methods on the active substances and volatile components of crude oil were investigated,and the effects of extraction methods on the protein structure and functional characteristics of Cinnamomum camphora seed kernel were further explored in order to obtain the optimal extraction method of each product from Cinnamomum camphora seed kernel,which would provide a theoretical reference for the deep processing of Cinnamomum camphora seed kernel oil and protein in the future.The main research contents are as follows:(1)The extraction rate and acid value of CCSKO obtained by different extraction methods were significantly different,while the peroxide value,saponification value,iodine value,fatty acid composition,triacylglycerol composition,group structure and thermal properties were not significantly different.The extraction rates from high to low were sub-critical fluid extraction of crude oil(SCFE,97.93%),supercritical fluid extraction of crude oil(SFE,95.24%),solvent extraction of crude oil(SE,93.49%),aqueous extraction of crude oil(AE,56.10%),hot pressing crude oil(HP,47.72%)and cold pressing crude oil(CP,44.48%),respectively.The acid values ranged from high to low as HP(3.89 mg KOH/g),SE(3.26 mg KOH/g),SCFE(3.11 mg KOH/g),CP(2.57 mg KOH/g),AE(1.97 mg KOH/g),and SFE(1.94 mg KOH/g).(2)The active substance content,antioxidant activity and volatile components in CCSKO obtained by different extraction methods are significantly different.Among them,the contents of total polyphenols(307.12 μg GAE/g),δ-tocopherol(13.93 μg/g)and total sterols(838.91 μg/g)in AE were the highest,with the DPPH and ABTS free radical scavenging abilities the strongest;α-tocopherol(75.02 μg/g)and γ-tocopherol(514.20 μg/g)in CP were the highest;and the highest content of squalene(19.36 μg/g)was found in SCFE.The optimum conditions for the extraction of volatile components from CCSKO by solid-phase microextraction were determined by single factor condition optimization: injection mass of 1.0 g,extraction temperature of 50 °C,equilibration time of 20 min and extraction time of 30 min.Under these conditions,a total of 83 volatile compounds were identified,mainly ketones(50.97%–78.28%),alcohols(4.74%–30.56%)and hydrocarbons(2.95%–18.76%),among which,HP had the most volatile components(58 kinds)and AE the least(33 kinds).The main odor-contributing substances of CCSKO were 2-nonanol,ethyl decanoate,linalool and methyl eugenol.(3)The amino acid compositions of the six Cinnamomum camphora seed kernel proteins were basically the same,and the subunit molecular weights were mainly distributed in three bands of 40-55 k Da,35-40 k Da and 10 k Da.The secondary structure of protein in hot pressed cake was changed most significantly,with the lowest fluorescence intensity and denaturation temperature(110.12 °C),the highest surface hydrophobicity(71.74)and oil holding capacity(13.64 g/g);the content of free sulfhydryl in aqueous extract protein(8.12 μmol/g)was the highest;the solubility and emulsification of protein in the sub-critical extraction cake were the best,while the foaming property of protein in the supercritical extraction cake was the best. |
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