EGCG对美拉德反应产物抗氧化性能的影响

美拉德反应广泛存在于食品热加工和储藏过程中,能够改变食物的色、香、味,赋予食物更好的口感和外观。虽然美拉德反应的具体机制尚未清晰,还会产生有害衍生物,但是许多研究已经表明美拉德反应产物(MRPs)具有很强的抗氧化活性。表没食子儿茶素没食子酸酯(EGCG)作为天然功能性成分,能有效阻碍美拉德反应有害产物的生成。以葡萄糖-半胱氨酸为模型,采用DPPH法、ABTS法、总还原能力等抗氧化性测定方法,考察了EGCG参与下,加热时间、反应温度、体系pH值、羰氨物质的量比对模型产物抗氧化能力的影响。结果表明:10 m L葡萄糖-半胱氨酸体系中,当反应温度130℃、加热时间1.0 h、p H 6.0、羰氨物质的量比1.5∶1(葡萄糖0.029 7 g)、EGCG添加量为1.5 mg时,所得MRPs的抗氧化能力最强,为大宗食品加工和抗氧化型功能性食品开发提供了技术参考。

Effect of EGCG on antioxidant properties of Maillard reaction products

Maillard reaction widely exists in the process of food hot processing and storage,which can change the color,aroma and taste of food,and endow food a better taste and appearance. Although the specific mechanism of Maillard reaction is not clear,and harmful derivatives will be produced,many studies have shown that Maillard reaction products have strong antioxidant activity. Epigallocatechin gallate( EGCG),as a natural functional component,can effectively inhibit the formation of harmful products in Maillard reaction. The Maillard reaction system was prepared with glucose cysteine( 0. 1 mmol) dissolved in phosphate buffer( PBS) at pH 7. 4,and the anti-oxidation tests such as DPPH method,ABTS method,and total reduction capacity were conducted. With the participation of EGCG,the effects of heating time( 0,0. 5,1,1. 5,2,2. 5 h),reaction temperature( 110,120,130,140,150,160 ℃),pH value( 2,4,6,7. 4,8,10),carbonyl ammonia molar ratio( 0. 25 ∶ 1,0. 5 ∶ 1,1 ∶ 1,1. 5 ∶ 1,2 ∶ 1,4 ∶ 1) on the antioxidant capacity of the model product were investigated. When DPPH index was used to determine the antioxidant activity of the sample,DPPH was dissolved in methanol to obtain the DPPH solution with a concentration of 0. 05 mmol/L·25 μL of the sample and 4 mL of DPPH solution were pipetted into a test tube,then mixed and reacted in darkness for 30 min at room temperature. The absorbance was measured at517 nm. When ABTS index was used to determine the antioxidant activity of the sample,ABTS working solution should be prepared first,that is,5 mL of ABTS solution( 7 mmol/L) and 5 mL of potassium persulfate solution( 2. 45 mmol/L) were mixed evenly,and then ABTS working solution was obtained by reaction in darkness at room temperature for 12-16 h,and then diluted with absolute ethanol to 0. 70±0. 02 at 734 nm. 10 μL of the sample and 12 mL of ABTS working solution were pipetted into a test tube,then mixed and reacted in darkness for 30 min at room temperature. When the total reduction capacity of the sample was measured,1 mL sample was transferred to the test tube,and 2. 5 mL of 0. 2 mol/L pH 6. 6 phosphate buffer and 2. 5 mL of 1% potassium ferricyanide was added successively,and the mixture was incubated at 50 ℃ for 20 min. After cooling down to room temperature,2. 5 mL of 10% trichloroacetic acid was added and the mixture was centrifuged( 3 000 r/min) for 10 min,then 1 mL of supernatant was taken.Then 3 mL of distilled water and 0. 3 mL of 0. 1% ferric chloride were added,and the mixture was shaken and stood for 10 min. The absorbance was measured at the wavelength of 700 nm. The absorbance indicates the total reduction capacity of the sample,which is directly proportional to the absorbance. The results showed that under the three indicators,with the participation of EGCG,the antioxidant capacity of the sample increased first and then decreased with the increase of reaction temperature,system pH value,and carbonyl ammonia molar ratio. In the glucose-cysteine system,the strongest antioxidant capacity of MRPs was in the following condition: EGCG was 1. 5 mg,the reaction temperature was 130 ℃,the heating time was1. 0 h,pH 6. 0,and the molar ratio of carbonyl ammonia was 1. 5 ∶ 1( glucose 0. 029 7 g). This study provided a technical reference for the bulk food processing and the development of antioxidant functional products.