| Phytosterols,are one of the basic components of plant cell membrane formation.Changes in cell membrane structure occur during senescence.Membrane lipid that key substances of membrane structure,contains sterols,phospholipids and glycolipids,in which sterols play a stabilizing role in the membrane structure.Plant cell membrane mainly includes sitosterol,stigmasterol and campesterol.Stigmasterol,one of plant phytosterol.Green Asparagus(Asparagus officinalis L.)is a nutrient-rich and valuable vegetable,but the post-harvest storage period is very short.In this paper,green asparagus was soaked in 0.5 g/L stigmasterol for 1,3 and 5 days in the dark at room temperature(20±1 ?)and low temperature(4 ±0.5?),respectively.The changes of main fatty acids in membrane lipid were measured by GC-MS in order to observe the effect of stigmasterol as the plant membrane component on the main fatty acids in membrane lipid of asparagus at normal temperature and low temperature,respectively.Then the green asparagus was soaked in different concentrations(0,0.2,0.5 and 1.0 g/L),and stored in low temperature(40.5 °C)and relative humidity(95%).The physical,chemical and physiology changes of green asparagus during storage were measured to study the preservation effect of stigmasterol on green asparagus in low temperature.The main conclusions were as follows:1?The green asparagus was soaked in 0.5 g/L stigmasterol for 1,3 and 5 days at 20 ± 1 ? and at 4 ± 0.5 ?,respectively.The changes of main fatty acids were determined by GC-MS.The results showed that with the prolonging of storage time,the relative content of the main unsaturated fatty acids in asparagus in both control and treatment at 4?was higher than 20 ?,which was helpful to improve the fluidity of the membrane and may be related to the the ability of low temperature to induced desaturase to catalyze the formation of unsaturated fatty acids in palmitic acid.2?The effects of different concentrations of stigmasterol on the quality of green asparagus were studied.The results showed that at the 40th day,the weight loss of asparagus treated with 0.2,0.5 and 1.0 g/L stigmasterol was increased to 11.74%,10.03%and 11.1%,respectively,while that of the control was increased to 12.37%.Ascorbic acid content of asparagus treated with 0.2,0.5 and 1.0 g/L stigmasterol was 7.26,10.99 and 8.42 mg/100 g FW,respectively,whereas control sample was only 6.13 mg/l00g FW.Moreover,0.5 g/L stigmasterol treatment maintained green asparagus color,improved sensory score and chlorophyll content and retarded the firmness.These aspects were better than other treatments and control,indicating that 0.5 g/L stigmasterol had significant preservation effect on green asparagus.The preservation effects of three oncentrations of stigmasterol on green asparagus:0.5 g/L>1.0 g/L>0.2 g/L?3?The effects of different concentrations of stigmasterol on the lignification of green asparagus were studied.The results showed that at the 40th day,the total phenols content of 0.5 and 1.0 g/L stigmasterol treated batches was 0.59 and 0.40g/kg,respectively,while that of the control was 0.44g/kg.The content of lignin of asparagus treated with 0.5 and 1.0 g/L stigmasterol was 5.2 and 5.9 mg/100g FW,respectively,whereas control sample was 6.07 mg/100g FW.Moreover,0.5 g/L stigmasterol treatment ensured lower activities of PAL?PPO and POD than other treatments,indicating that 0.5 g/L stigmasterol effectively inhibited the lignification of green asparagus.4?The effects of different concentrations of stigmasterol on membrane lipid peroxidation of green asparagus were studied.The results showed that at the 40th day,the relative conductivity of the control sample was 2.3 times more than the initial,while that of 0.5 and 1.0 g/L stigmasterol treated batches was 2.0 and 2.2 times more than the initial,respectively.The hydroxyl peroxide content of green asparagus treated with 0.5 and 1.0 g/L stigmastol was 5.9 and 6.1 ?mol/g,respectively,whereas control sample was 6.5?mol/g.Moreover,0.5 g/L stigmasterol treatment ensured lower MDA content,and maintained higher activities of SOD and CAT than other treatments,indicating that 0.5 g/L stigmasterol effectively inhibited membrane lipid peroxidation of post-harvest green asparagus. |
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