Abstract: [Objective] This paper aimed to investigate the quality forming regularity of Ping'ou hybrid hazelnut(Corylus heterophylla×C.avellana) kernels and discuss the nutritional quality characteristics of the kernel during growth and development stages to provide important theoretical foundation for production and cultivation management, timely harvesting and efficient utilization of hazelnut.[Method]Ping'ou hybrid hazelnut at different developmental stages was used to measure the water content in husk, shell and kernel, main nutrition substance content and important bioactivators, in kernels, including fat content, protein content, sugar content, fatty acid content, VC and VE content, total phenols and total flavonoids content, and then analyze the quality forming regularity of hazelnut during development phase further. [Result] At the early stage of development, the water content of kernels decreased rapidly from 88.6% to 38.2%; the content of crude fat, total protein and VE increased rapidly from 29.9 g·kg^-1 FW, 37.3 g·kg^-1 FW and 0.038 g·kg^-1 oil to 362.4 g·kg^-1 FW, 96.7 g·kg^-1 FW and 0.35 g·kg^-1 oil, respectively. However, those substances all remained relatively stable level at the later stage of development. The VE in the kernel was mainly composed of α-configuration of VE, with a small amount of β-, γ- and σ-configuration. Sugar content gradually increased during the whole development period. Sucrose was the main component of sugars in hazelnut kernels and its content gradually increased during the whole development stages. VC reached the maximum content of 0.13 g·kg^-1 FW at the kernel-filling stage and then sharply decreased until 0.062 g·kg^-1 FW at the fully-mature of hazelnuts. The contents of total phenols (TPC) and total flavonoids (TFC) gradually increased in the early stage of development and reached the peak value at the kernel-filling period, being 1.49 g GAE·kg^-1 FW and 2.44 g RE·kg^-1 FW, respectively and then rapidly decreased until to the end of development phase. The final TPC and TFC contents were 34.0% and 23.7% of the peak values at the nut abscission period, respectively. [Conclusion] During the whole development period, the water content of kernels decreased gradually and main nutrition substances increased gradually. As the main component of fatty acid, the increase tendency of oleic acid content was in step with the decrease tendency of palmitic acid and linoleic acid contents. VE, mainly the α-configuration, was gradually accumulated; Main antioxidants substance VC, phonelic and flavonoid were rapidly accumulated and peaked at kernel-filling period and then decreased at the later stage. The early development phase was the significant time for nutrient substance formation of hazelnut kernels. Kernel-filling period was the important transition stage of development of hazelnut, during which hazelnut kernels completed the accumulation of the main nutrient substances and had higher antioxidant substance reserves.

Key words: hybrid hazelnut, nut, development phase, quality forming, nutrient substances