| Peanut skin was the low value by-product during the processing of peanut, which contained rich phenolics who had great antioxidant activity and had been attracted the attention of researchers at home and abroad. However, the fractionation and antioxidative characteristics of individual phenolic compounds contained in the peanut skin have not been studied, as well as the application in sausage. In this context, the aim of this study was to optimize the preparation of the phenolic compounds of peanut skin, characterize and collect the antioxidative fractionations of phenolic compounds extracted from peanut skin, then the application of phenolic compounds in peanut skin in sausage had been researched. The main results were summarized as follows:Using ultrasound-assisted extraction to extract the phenolic extract which had high extraction rate, then analysis the composition of phenolic compounds by RP-HPLC. The extraction conditions were optimized by quadratic regression rotation design experiment and the optimum extraction conditions were as follows: ethanol concentration 55%, time 13 min, power 240 W and temperature 47 ℃. Under these conditions, the extraction rate was(85.62±0.52)%, the predictive value is 86.35%, there is on error of 0.80%. The result of RP-HPLC showed 8 kinds of phenolic compounds were eluted within 65 min, which were as follows: protocatechuic acid,(-)-epigallocatechin,(+)-catechin, procyanidin B2, epicatechin, p-coumaric acid, ferulic acid and quercetin. The correlation coefficients, r, of calibration curves of the 8 compounds were >0.99. The RSD of precision, repeatability, respectively and stability was 0.76%~2.39%, 1.12%~2.43% and 0.99%~2.67%.The recoveries was 86.9%~111.27%.The separation of different fractions of phenolic compounds was performed by using a semi-preparative HPLC. The antioxidant activity was detected by chemical antioxidant method. The results showed that catechin, epicatechin, epigallocatechin and procyanidin B2 in peanut skin prossessed higher purity(80%) than phenolic acids. The FRAP value of procyanidin B2 was 22.20±0.50 mmol/g, who also had the lowest EC50 value of DPPH radical scavenging capacity, superoxide anion radical-scavenging capacity and hydroxyl radical-scavenging capacity, 71.12±0.08 μg/mL, 103.28±4.26 μg/mL and 304.20±6.22 μg/mL, respectively. So procyanidin B2 was found to possess the highest antioxidant activity among other eight fractions of phenolic compounds.Using complex enzymatic method to extract the phenolic extracts which contained high content of procyanidin B2, then prepare sausage by adding them to study the impact on the storage stability, the color, and the texture of the sausage. The extraction conditions were optimized by quadratic regression rotation design experiment and the optimum extraction conditions were as follows: the proportion of cellulase and pectinase proportion was 2:1, the addition, temperature and time of enzyme were 0.51%, 54 ℃ and 120 min, the extraction times was 4 times, the yield was(1868.32±52.44)%, the predictive value is 1883.11μg/g, there is on error of 0.78%. The addition of the phenolic cmpounds of peanut skin could significantly improve(P<0.05) the storage stability(peroxide value and acid value) of the sausage. The storage stability had a dose-dependent manner with the amount of antioxidant. The effect of the same dose phenolic compounds of peanut skin was better than Vc(1.69% and 0.44%), and could not compare with BHT(8.57% and 8.84%); the color was significantly changed(P<0.05), with the increasing of the addition of the phenolic cmpounds of peanut skin, the L*, a* and b* all changed as parabola, getting the extreme point at 0.05% and 0.03%, the minimum value of L* was 66.55±0.91 at 0.05%, the maximum of a* was 6.95±1.39 at 0.03%, the minimum value of b* was 10.84±0.37 at 0.05%. the addition of Vc and BHT had no significant changes(P>0.05) on the color of the sausage; the addition of phenolic compounds of peanut skin could significantly(P<0.05) improve the texture of the sausage, when the addition was 0.01%, all of the texture profile analysis(TPA) indexes reached the maximum value: hardness 3597.33±281.22 g, springiness 0.90±0.03 、 cohesiveness 0.59±0.07 、chewiness 2098.87±230.43, increasing by 25.26%、7.14%、11.32% and 92.65%, respectively. With the increasing of the addition of phenolic compounds of peanut skin, there was no significant impact(P>0.05) on TPA. The addition of Vc and BHT could only significantly increased(P<0.05) the hardness(25.69% and 26.40%, respectively). There was no significant changes on springiness, cohesiveness and chewiness(P>0.05). |
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