【作者】 王萍；

【导师】 张佰清；

【作者基本信息】 沈阳农业大学 ， 食品科学， 2024， 硕士

【摘要】 黑果腺肋花楸浊汁易存在不稳定性现象,常加入食品添加剂中的稳定剂来减轻这一现象。超声波的空化效应能够降低浊汁中的果肉粒度,从而提高果汁的稳定性。本研究基于非热加工的超声技术对鲜榨黑果腺肋花楸汁进行稳定性研究,考察超声处理对黑果腺肋花楸汁品质的影响,并分析超声过程中的自由基效应对黑果腺肋花楸汁稳定性的影响。主要研究结论如下:（1）超声处理时间、功率和过滤目数的增加使得黑果腺肋花楸汁的云值和云稳定性增加,浊度和离心沉淀率降低,在超声处理25 min基本趋于稳定状态。超声对经100目过滤的黑果腺肋花楸汁的稳定性影响最大。（2）在理化指标方面,超声处理对黑果腺肋花楸汁的可溶性固形物（TSS）、p H、总酸含量无明显变化;颜色出现轻微红移和黄移,在超声270 W、360 W条件下,总体颜色差异较小。在营养成分方面,还原糖、总黄酮含量增加;总糖、花青素含量略有减少;270 W和360 W功率条件下更利于黑果腺肋花楸汁总酚的保留;270 W条件下单宁含量降低,360 W、450 W条件下单宁含量增加。在抗氧化能力方面,黑果腺肋花楸汁的DPPH、ABTS自由基清除率随超声时间的延长先增加后降低,超声30 min、450 W条件下DPPH、ABTS自由基清除率分别为95.34%、96.37%。在流变学特性方面,与未超声处理的相比,超声处理后的黑果腺肋花楸汁表观黏度显著增加,但仍为经典的假塑性非牛顿流体。超声处理对黑果腺肋花楸汁的弹性行为比黏性行为影响更大,450 W 20min黑果腺肋花楸汁的G′和G″值达到最大。在微观结构方面,超声处理时间和功率的增加,黑果腺肋花楸汁微观结构的破坏程度变大。（3）通过分析不同超声时间和功率条件下H₂O₂和·OH的产量变化,确定添加自由基屏蔽剂（硫脲CH₄N₂S）的最佳量为4 m M。超声时间和功率的增加能显著减小颗粒粒径,降低其分散性指数,与未添加硫脲相比,添加硫脲后超声的自由基效应对黑果腺肋花楸汁浊度、粒径、分散性指数无显著性差异（P>0.05）。低功率短时超声产生的自由基对黑果腺肋花楸汁稳定性无明显效果,随着超声时间和超声功率的增加,云值和云稳定降低、离心沉淀率增加。借助多重光散射仪观察体系局部的不稳定现象,发现失稳机制主要表现为粒子沉降,而超声处理可增加粒子的悬浮性,同一超声条件下,添加硫脲前后发现不稳定现象极为相似。背散射光稳定性指数:未超声（1.098%/h）>超声+CH₄N₂S（1.021%/h）>超声（0.941%/h）。表明超声波的自由基效应对黑果腺肋花楸汁的稳定性有一定的影响,机械效应占主要作用。更多还原

【Abstract】 The turbid juice of Aronia melanocarpa is prone to instability,which is often mitigated by the addition of stabilizers in food additives.The cavitation effect of ultrasound can reduce the particle size of pulp in the cloudy juice,thus improving the stability of the juice.In this study,the stability of freshly squeezed Aronia melanocarpa juice was investigated based on non-thermal ultrasound technology to examine the effect of ultrasound treatment on the quality of Aronia melanocarpa juice and to analyze the effect of free radicals in the process of ultrasound on the stability of Aronia melanocarpa juice.（1）The increase of ultrasonication time,power and mesh filtration resulted in the increase of cloud value and cloud stability,decrease of turbidity and centrifugal sedimentation rate of Aronia melanocarpa juice,which basically tends to be stabilized in ultrasonication for 25 min,and the most significant effect was found at the power of 450 W.Ultrasound had the strongest stabilizing effect on the Aronia melanocarpa juice after 100 mesh filtration.（2）The results showed that in terms of physicochemical indexes,there was no significant change in the Soluble solid（TSS）,p H,and total acid content of Aronia melanocarpa juice,and the color showed a slight red shift and yellow shift,and the overall color difference was small under the ultrasound conditions of 270 W and 360 W.In terms of nutrient composition,the content of reducing sugars and total flavonoids increased,the total sugar and anthocyanin content decreased slightly,the 270 W and 360 W power conditions were more favorable for the retention of total phenols in Aronia melanocarpa juice;the tannin content decreased in the 270W condition,and it increased in the 360 W and 450 W conditions.In terms of antioxidant capacity,the DPPH and ABTS radical scavenging rates of Aronia melanocarpa juice increased and then decreased with the increase of ultrasound time and the DPPH and ABTS free radical scavenging rates under ultrasonication for 30 min and 450 W were 95.34%and 96.37%,respectively.In terms of the changes in rheological properties,the apparent viscosity of the ultrasonicated Aronia melanocarpa juice was significantly increased compared to that of the un-sonicated one,but it was still a classical pseudoplastic non-Newtonian fluid.The ultrasonic treatment had a greater effect on the elastic behavior than the viscous behavior of Aronia melanocarpa juice,with the maximum values of G′and G″for Aronia melanocarpa juice at 450W for 20 min.In terms of microstructure,the increase in ultrasonication time and power increased the disruption of the microstructure of Aronia melanocarpa juice.（3）The effect of free radicals generated by ultrasound on the stability of Aronia melanocarpa juice was investigated by analyzing the changes in the yields of H₂O₂ and·OH under different ultrasound time and power conditions,and by determining the optimal amount of free radical shielding agent（thiourea CH₄N₂S）to be added at 4 m M.The increase of ultrasound time and power significantly reduced the particle size and lowered its dispersibility index.Compared with no thiourea added,the free radical effect of ultrasound had no significant difference（P>0.05）on the turbidity,particle size,and dispersibility index of Aronia melanocarpa juice after the addition of thiourea.The free radicals generated by low power short time ultrasound had no significant effect on the stability of Aronia melanocarpa juice,with the increase of ultrasound time and ultrasound power,the cloud value and cloud stability decreased and the centrifugal sedimentation rate increased.The local instability of the system was observed with the aid of a multiple light scattering instrument,and it was found that the destabilization mechanism was mainly manifested as particle sedimentation,while ultrasonication increased the suspension of particles,and the instability was found to be extremely similar before and after the addition of thiourea under the same ultrasonic conditions.Backscattered light stability index:unsonicated（1.098%/h）>sonicated+CH₄N₂S（1.021%/h）>sonicated（0.941%/h）.The results showed that the free radical effect of ultrasound had an influence on the stability of Aronia melanocarpa juice,with the mechanical effect playing a major role.更多还原