低温和中温协同超高压对鲜榨荔枝汁灭酶处理和色泽影响的研究

Effect of High Pressure Processing (HPP) Combined with Low and Moderate Temperature Treatments on the Color and Enzyme Inactivation in Freshly Squeezed Lychee Juice

摘要:

为探讨超高压处对鲜榨荔枝汁中过氧化物酶(POD)、多酚氧化酶(PPO)活性的影响，对鲜榨荔枝汁进行了单独超高压处理（300~450 MPa，10~40 min）及低温（10 ℃）、中温（40~70 ℃）协同超高压(450 MPa，20 min)处理，通过对荔枝汁品质指标测定，探讨了温度协同超高压对荔枝汁品质的影响。试验结果表明：在室温、保压时间为20 min的条件下，300~450 MPa压力范围内荔枝汁中POD酶被激活，在300 MPa时活性最高；PPO酶在此压力范围内则随着压力的升高而降低；POD比PPO酶更耐压；450 MPa压力条件下，随着保压时间的延长，POD、PPO酶的活性减小；低温和中温协同超高压处理对荔枝汁中POD、PPO酶的钝化存在一定的协同效应，且中温范围内（40~70 ℃）温度越高，协同抑制效应越明显；中温协同超高压处理后的荔枝汁的L*值显著升高，果汁的亮度增加，但是随着协同温度的升高，总色差ΔE*逐渐增大，果汁的色泽变化增大。

Abstract:

In order to investigate the effects of high pressure processing (HPP) on the activities of peroxidase (POD) and polyphenol oxidase (PPO) in the freshly squeezed lychee juice, HPP (300~450 MPa, 10~40 min) alone and treatments of HPP (450 MPa, 20 min) combined with low (10 ℃) and moderate temperatures (40~70 ℃) were conducted on fresh lychee juice, respectively. Physicochemical properties and sensory quality of lychee juice were measured to explore the combination of HPP and temperature on the quality of lychee juice. The results showed that POD was activated only when HPP was carried out under pressure between 300~450 MPa at 25 ℃ for 20 min. The POD activity reached the maximal level after 300 MPa treatment. Below the aforementioned pressure range, the PPO activity decreased with increasing pressure. PPO was less pressure-resistant than POD. At the pressure of 450 MPa, the activities of POD and PPO decreased with increasing pressure-holding time. HPP combined with low and moderate temperatures had a certain degree of synergistic effect on the POD and PPO inactivation. In the moderate temperature range (40~70 ℃), the synergistic inhibitory effect was more significant with higher temperatures. Upon combining the treatment of HPP with moderate temperature, the L* value of lychee juice was significantly increased and the brightness of the juice was enhanced. However, with increasing temperature in the HPP and temperature combined treatment, the total color difference ?E* value and the change in color of the juice gradually increased.