控压气体处理对草莓多模式超声冷冻的促进作用及其机理研究

In order to solve the problems such as the high thawing loss and severe tissue structure collapse due to the large and uneven size of the internal ice crystals, which are prevalent in the current frozen strawberries. In this project, it is aiming to investigate the effects of micro-bubbles from controlled-pressure gas treatments on multi-mode ultrasound freezing strawberry and their regulations. The new idea combining the controlled-pressure gas treatments and multi-mode ultrasound freezing may not only increase the freezing efficiency, but also improve the quality of frozen strawberry products is adopted for this research. It will be clarified that the stable micro-bubbles produced by controlled-pressure gas treatments will increase the efficiency of multi-mode ultrasound frozen strawberry and improve the quality resulting from the uniform size distribution of ice crystals formed inside the strawberry. It will mainly focus on the mechanism of nucleation induced and ice crystal size regulation, the construction of heat transfer model, the regulatory mechanism of frozen quality of strawberry and the freezing rule of solid model system by the combination of controlled-pressure gas treatments and multi-mode ultrasound freezing. The synergistic effect of pressure-controlled gas treatment and multi-mode ultrasound with "multi-spectrum" on the mechanism of strawberry freezing and great freezing efficiency improvement will be revealed in-depth. The results will provide some basis for solving some difficult scientific and technological problems of strawberry freezing, such as low freezing efficiency, large and non-uniform size of ice crystals, high thawing loss and serious structural collapse. This has obviously important meaning for promoting the industry producing the high-value frozen fruits and vegetables.

针对当前冷冻草莓普遍存在内部冰晶体尺寸大且分布不均匀所导致的解冻汁液流失率高、组织结构坍塌严重等难题，本项目拟以控压气体作用形成“微气泡”处理为新手段，以控压气体处理对草莓多模式超声冷冻的作用及调控为研究对象，采用控压气体处理协同多模式超声有效提高草莓冻结效率和品质为研究新思路，阐明控压气体处理有效提高草莓多模式超声冻结效率的作用机制，以及协同作用带来的草莓内部冰晶小且分布均匀化提升冻结品质的作用机理。重点研究控压气体处理协同多模式超声冷冻草莓的成核诱导和冰晶体调控的机制、草莓高效冻结过程传热模型的构建、草莓冻结品质的调控机制以及模拟固相体系冻结的规律，深入揭示在大幅度提高草莓冻结效率的同时，控压气体的“微气泡”处理与拥有“多频谱”的多模式超声协同影响草莓冷冻的作用机理，为解决草莓冷冻领域存在的难题提供新的绿色处理方法及理论支撑，对促进高附加值果蔬冷冻产业的发展具有重要意义。

草莓属于浆果类高水分含量的水果，当前，草莓速冻产业普遍存在冷冻过程冰核形成缓慢、形成的冰晶体尺寸大且分布不均匀，造成解冻后草莓汁液流失率高、营养物质损失大、色泽降低严重、组织结构坍塌变软等突出难题，严重制约着速冻草莓产业的发展。大量的试验发现，超声波对食品冷冻具有显著的促进效果，是一种极具应用前景的食品非热物理加工技术。本项目研究了控压气体处理对超声速冻草莓冻结效率和品质同步调控的机制，探究了多模式超声冷冻协同控压气体处理的作用机理。全面完成了研究任务，主要研究结论如下：1.多模式超声可以很好地诱导草莓成核的发生，尤其是同步双频20/40 kHz和三频20/40/60 kHz；2.控压气体处理对草莓超声冷冻有显著促进作用，提升了成核温度，增强了冷冻效率，使物料通过最大冰晶生成带的时间缩短；3.多模式超声冷冻缩短了草莓冷冻时间，降低了冻结草莓解冻汁液流失率和组织结构破坏情况，提升了质构和营养物质的保留，从而改善了冻结草莓的品质；4.通过研究模拟固相体系发现，控压气体处理与超声处理有协同作用，可明显降低样品的冷冻时间，提高冷冻效率，减小样品冰晶体尺寸；5.阐明了超声促进固体物料冷冻的机制不仅包括超声可提高物料的传热系数，而且包括空化效应产生的微气泡能作为物料水分成核的晶核。本项目在执行期间，以第一/通讯作者发表相关SCI学术论文10篇，其中第一标注9篇，高被引论文2篇；申请国家发明专利4项（其中授权1项）。相关研究成果获得江苏省科技进步三等奖、中国商业联合会科技进步特等奖、神农中华农业科技三等奖各一项。