感应电场处理后蓝莓泥酶活性及总花青素含量变化

为了避免食品电场加工中因电极使用而产生电化学反应造成食品污染和电极腐蚀的问题,采用交变磁通代替电极作为激励源,在果泥料液中诱导形成感应电场(induced electric field,IEF),实现对蓝莓果泥的IEF处理:分析激励电压、温度和时间对蓝莓果泥多酚氧化酶(polyphenol oxidase,PPO)和过氧化物酶(peroxidase,POD)活性及总花青素含量的影响。结果表明,100 V激励电压产生的IEF可减缓PPO和POD酶活的受热损失。150和250 V激励电压下,IEF与高温钝化PPO和POD具有协同作用。IEF可提高花青素分子的热稳定性且电场强度越高稳定作用越强。与未处理果泥相比,经85℃、250 V激励电压的IEF处理30 min的果泥总花青素含量得到最大提升(12.55%),PPO和POD可被完全灭活。该条件下获得的蓝莓果泥表观黏度与鲜榨果泥更为接近,且储藏期内(4℃,8周)的菌落总数维持在1 lg(CFU/mL)以下,显著低于常规热处理(0 V)和未经热处理的果泥。研究为蓝莓果泥的IEF处理提供了数据参考。

Changes of enzyme activity and total anthocyanin content in blueberry pureeafter induction electric field treatment

In order to avoid food contamination and electrode corrosion caused by electrochemical reaction adopting electrodes in prevailing electric field processing,induced electric field(IEF)processing of blueberry puree was conducted by applying magnetic flux to replace metal electrodes as excitation source.Effects of excitation voltage,temperature and processing time on polyphenol oxidase(PPO)activity,peroxidase(POD)activity and total anthocyanin content were investigated.Results indicated that IEF at excitation voltage of 100 V could maintain PPO and POD activity,but IEF at excitation voltages of 150 V and 250 V presented a synergistic effect with heat on the inactivation of the enzymes.IEF could enhance the thermal stability of anthocyanin molecules.Meanwhile,this stabilizing effect of IEF on anthocyanin was more significant when higher excitation voltage was applied.Compared with untreated blueberry puree,the IEF-treated sample had a maximum increase of 12.5%in anthocyanin content at the optimum conditions:excitation voltage of 250 V,temperature of 85℃and processing time of 30 min,under which both PPO and POD were completely inactivated.Besides,the IEF-treated blueberry puree presented an apparent viscosity similar with that of the untreated blueberry puree.The total colonies number in IEF-treated blueberry(250 V,85℃,30 min)remained less than 1 lg CFU/mL during 8 weeks of storage at 4℃,which was significantly lower than that of the conventional heat-treated(0 V)and untreated samples.This study provides certain value reference for IEF processing of blueberry puree.