Research On The Postharvest Physiology And Fresh-preservation Technology Of Xiang Lotus Seed During Storage

With the rapid development of China's aquatic industries,aquatic such as fresh lotus seed is much appreciated by the majority of consumers.However,because of its short harvesting period and easily occurred post-harvest spoilage,the unmarketable situation of fresh lotus seed was formed.For a long time,its main commodity forms are dried lotus seed products in the market.With the advances in food processing and preservation technology,fresh lotus seed will gradually replace the dried commodity forms,and be the mainstream of the market for its full appearance and fresh flavor.Although the fresh-keeping period of fresh lotus seed is very short,till now the study for shelf time extension is still in the initial stage at home and abroad.Therefore,it is important to conduct in-depth research on the pos-harvest physiology and fresh-preservation technologies of fresh Xiang lotus seed,which is the inevitable ways for further development of aquatic industries.The present study focused on the post-harvest physiological changes of fresh Xiang lotus seeds at storage temperatures of?4±0.1??and?25±0.1??.In addition,the electronic tongue had been used to investigate the dynamic change trend of taste of fresh lotus seeds stored at the different temperatures to identify its optimal storage periods after harvest.The specific spoilage organisms?SSO?of fresh lotus seeds stored at a low temperature were separated and identified,and their growth and decline rules were studied as well.The single factor and orthogonal experiment designs were conducted to investigate the color-protection effects of L-cysteine,sodium chloride,sodium bisulfite,citric acid,and EDTA-Na₂,and the coating preservative effects of chitosan,alginate,pullulan,sodium stearate,gelatin on hulled Xiang lotus seed.Thus,a storage and preservation strategy for hulled fresh lotus seeds was built.The detailed research results were as follows:The storage temperature had extremely significant effects on the moisture and protein contents,L*,a*,b*and sensory qualities of fresh lotus seeds?P<0.01?.Compared to the lotus seed storeds at room temperature,the highest point of SSC?mature saturation point?was heavily delayed to be the 21^st d post-harvest?15 d delayed?if stored at?4±0.1??.Since the3^rd d postharvest,net photosynthetic rate of fresh lotus seeds preserved at?4±0.1??continued to be maintained at a lower level than that of lotus seeds preserved at?25±0.1??.Gustation changes of fresh lotus seeds,especially for bitterness,were small when stored at?4±0.1??,while the variations were fluctuated widely for those stored at?25±0.1??,of which the bitterness was gradually increased,and astringency and umami were declined.The SSO of fresh lotus stored at?4±0.1??were separated and identified to be Pantoea dispersa,Staphylococcus epidermidis,Staphylococcus warneri,and Pantoea agglomerans.The growing trends of total bacterial colonies,Pantoea dispersa,Staphylococcus epidermidis,Staphylococcus warneri of fresh lotus seeds were similar,which were decreased firstly,then increased by time pasted.The amount change of Pantoea agglomerans was irregular.These results indicate that the low temperature?4±0.1??storage could slow down the water loss and protein degradation of fresh lotus seed,thus significantly inhibit the respiration rate.Therefore,the low temperature storage could maintain the nutritional value and edible qualities to the maximum extent,and extend the shelf life of fresh lotus seeds.The types,dosages,and usage methods of the single color-preservation agent and coating fresh-preservation agent were further studied,and optimal combination for hulled lotus seed preservation was screened out.The best process is after spraying treatment with 0.3%citric acid and 0.020%EDTA-Na₂,soaking treatment with 2%sodium alginate for 5 min.The composite film slowed SSC,net photosynthetic rate,and the color variation of L*,a*,b*,W value down?P<0.05?,and inhibited PPO,POD activities and SSO?P<0.05?of fresh lotus seeds significantly.The freshness of fresh lotus seeds was extended.In conclusion,low temperature storage can greatly improved the qualities of fresh lotus seeds than room temperature.Through freshness-keeping treatments of fresh lotus seeds in the present study,the composite film was screened out and optimized.It has a good effect on the post-harvest storage of fresh lotus seeds.