低频电场冰温保鲜对虾的水分迁移规律及品质变化的影响

为探明低频电场延长冰温保鲜对虾货架期的可行性。在冰温基础上施加低频电场（LFEF+冰温）保鲜对虾，监测贮藏期间对虾的菌落总数和总挥发性盐基氮（TVB-N）含量变化，分析微观结构变化，通过低场核磁共振（LF-NMR）技术探究虾肉和虾头的水分迁移和变化规律，并与常规冰温保鲜作对照。结果表明:贮藏第9 d，LFEF+冰温组的菌落总数和TVB-N含量开始表现出显著低于对照组的趋势（P<0.05）；第12 d后，LFEF+冰温组的菌落总数比对照组低一个数量级；其TVB-N含量在第11 d比对照组显著低36%（P<0.05），货架期可达13 d以上。相比对照组的松散结构，LFEF+冰温组的虾肉微观结构变化程度明显较小。LF-NMR结果表明，低频电场从第7 d开始明显抑制冰温保鲜对虾虾头部位不易流动水向自由水的迁移，MRI成像可见水分扩散较慢。虾肉的腐败速率则低于虾头，LFEF+冰温组虾肉15 d内未出现明显的水分迁移。低频电场有利于延缓冰温保鲜期间对虾的腐败，延长货架期3~5 d。

Water Migration and Quality Change of Prawn Preserved under Controlled Freezing-point Storage Combined with Low Frequency Electric Field Technology

To study the feasibility of shelf life extending for prawns preserved through controlled freezing-point storage combined with low frequency electric field technology. A low frequency electric field was applied on controlled freezing-point storage to keep fresh of prawns (LFEF+CFPS). During storage, the total viable count (TVC) and total volatile basic nitrogen (TVB-N) content of prawn were monitored, and the microstructure changes were analysed. Moreover, the water migration and change of prawn meat and head were studied by the low field nuclear magnetic resonance (LF-NMR) technology, respectively. Meanwhile, the CFPS was used as control. The results showed that: Storage of 9th day, the TVC and TVB-N content of the LFEF+CFPS group began to show significantly lower than those of control group (P<0.05). Furthermore, the TVC in the LFEF+CFPS group was one order of magnitude under the control group at 12th day. Its TVB-N content was 36% lower than the control group at 11th day (P<0.05), and with the shelf life of more than 13 days. Compared with the loose structure of the control group, microstructure change of prawn in LFEF+CFPS group was significantly samller. LF-NMR technology also showed that, water migration from immobilized water to free water in prawn head was significantly inhibited by LFEF from storage of 7th day. Slower water diffusion was also found in MRI. As the decay rate in prawn meat was lower than that in prawn head, there was no apparent water migration in prawn meat of LFE+CFPS group within 15 days. LFEF was contributive to delay the corruption in prawn and prolong its shelf life for 3~5 days during CFPS.