留胚米贮藏过程中脂质氧化及挥发性物质变化的研究

Lipid oxidation and changes of volatile substances of germ rice during storage

以留胚米为研究对象,采用顶空固相微萃取-气相色谱-质谱联用(headspace solid phase microextraction/gas chromatography-mass spectrometry,HS-SPME/GC-MS)等方法分析留胚米在贮藏过程中(温度37℃,相对湿度75%)脂肪氧化以及挥发性物质的变化规律。结果表明,随着贮藏时间延长,留胚米脂肪含量显著降低(P<0.05);脂肪酶和脂氧合酶活性均上升,过氧化值、丙二醛值均显著增加(P<0.05)且均在21 d后趋于稳定;不饱和脂肪酸含量下降,饱和脂肪酸含量显著上升(P<0.05)。贮藏过程共鉴定差异挥发性化合物33种,包括萜类、烃类、杂环化合物、酮类、醛类、醇类,均与脂肪氧化密切相关;进一步拟合曲线(R^(2)>0.8)筛选出6种特征挥发性化合物,其中香气特征性化合物有2-乙酰基-1-吡咯啉和梨醇酯,醛类特征性化合物有(E)-2-十一烯醛和苯甲醛,醇类特征性化合物为2-乙基-1-十二烷醇,烃类特征性化合物为5,8-二乙基-十二烷。

The fat oxidation and the changes of volatile substances were analyzed by headspace solid phase microextraction/gas chromatography-mass spectrometry(HS-SPME/GC-MS)in the germ rice during storage(37℃,relative humidity 75%).Results showed that the fat and unsaturated fatty acid content of rice decreased substantially(P<0.05)as storage time increased.Meanwhile,the lipase and lipoxygenase activity,peroxide value,saturated fatty acid content,and malondialdehyde value exhibited a significant rise(P<0.05)and demonstrated a tendency to stabilize after 21 days.A comprehensive analysis revealed the presence of 33 distinct volatile compounds including terpenoids,hydrocarbons,heterocyclic compounds,ketones,aldehydes,and alcohols during storage.Notably,all these chemicals had a strong association with the process of fat oxidation.Further curve fitting(R^(2)>0.8)identified 6 characteristic volatile compounds,with 2-acetyl-1-pyrroline and pyritol ester as aroma characteristic compounds,(E)-2-undecylenal and benzaldehyde as aldehyde characteristic compounds,2-ethyl-1-dodecanol as alcohol characteristic compound,and 5,8-diethyl-dodecane as hydrocarbon compound.