Study On The Effect Of High Hydrostatic Pressure Processing On Physiology And Storage Quality Of Green Asparagus Spears

This study investigated the influence of high hydrostatic pressure(HHP)on the storage quality of green asparagus,elucidated the effect of pressure higher than 300 MPa as a method of processing on the microbial and storage quality of green asparagus spears,analyzed the effect of pressure of 20~100 MPa on postharvest physiology and storage quality of green asparagus spears.The purpose of current study was to provide a scientific evidence for the controling of the texture property of tender vegetables shoots,for using HHP to retain the quality of vegetables and fruits,and for the commercial application of HHP.The main research contents are as follows:1.Cell morphology and membrane structure of green asparagus treated by HHP were investigated.Effect of HHP on respiration rate at various pressure levels(300~600 MPa)for 1~20 min treatments were studied.In addition,seven treatment conditions were selected to study the effect of HHP on the cell integrity,malondialdehyde content and Relative permeability of cell membrane of prepared green asparagus.The results showed that cell of the samples treated by 100 MPa or lower pressure was undamaged,but the cell of the samples treated by 200 MPa or higher pressure was severely damaged,even loss viability.2.Effect of HHP on inactivation of aerobic bacteria,mould and yeast at various pressure levels(300~600 MPa)for 1~20 min treatments were studied.In addition,three treatment conditions were selected to study the effect of HHP on the quality of green asparagus during storage.The results showed that the effects of microorganism inactivation were improved with increasing of pressure and/or the holding time.The Weibull model was used to analyze the survival curves.The coefficients of determination(R2)were all higher than 0.97,indicating that the Weibull model fitted the microbial inactivation kinetics curve well.During the storage,the asparagus treated at 500 MPa for 5 min obtained better qualities,such as color and texture,than that of the products treated at 400 and 600 MPa.3.Postharvest physiology and storage quality of green asparagus treated by HHP were investigated.The harvested green asparagus were treated with various pressure levels(20 MPa,50 MPa and 100 MPa)for 2 min,then the vegetable were strored at4 ℃ and 90% relative humidity for 15 days.During storage,the changes ofrespiration rate,MDA content,cell membrane relative permeability,content of chlorophyⅡ and carotenoid,vegetable firmness,weight loss and color were determined.The results showed that compared with vegetable,HHP had obvious effects on the vegetable by lowering respiration rate,slowing down the chlorophyll degradation,keeping higher firmness and inhabiting apparent color change.Research provides a basis for HHP storage preservation of spear vegetables.4.Effect of HHP on lignification at various pressure levels(20~100 MPa)for 2min treatments were studied.The results showed that compared with the control group,HHP(50 MPa for 2 min)had obvious effects on the vegetable by lowering lignin content and reducing PPO and POD enzyme activity.During the storage,caffeic acid and erucic acid gradually increased,but coumaric acid and ferulic acid decreased.It is possible that caffeic acid and erucic acid play an important role for lignin synthesis,but high hydrostatic pressure processing(50 MPa for 2 min)inhibited the growth of caffeic acid and erucic acid.