Study On The Effect Of Storage Conditions And Irradiation Processing On The Quality Of Cyperus Esculentus

As a new oil crop,Cyperus esculentus has a crude fat content of 22.14-44.92%,and its oil has a high content of unsaturated fatty acids,mainly oleic acid(67.71-74.60%),and its nutritional value is comparable to that of olive oil.In addition,it has the characteristics of high yield per mu,easy to plant and short growth cycle,so it has great development prospects.However,Cyperus esculentus grow in the soil,and the microorganisms are very easy to attach to their surfaces and pores during harvest.The moisture content of newly harvested Cyperus esculentus is about 30%.When stored improperly,there will be mildew,oxidation and rancidity and other phenomena,these problems will lead to a waste of Cyperus esculentus resources.In order to solve this problem,the effect of storage on the quality characteristics of Cyperus esculentus and oil was studied in this paper.The adsorption and thermodynamic characteristics of Cyperus esculentus under different temperature/humidity were determined,and the changing rules of oil quality of Cyperus esculentus and oil under different storage conditions and methods were determined,and the storage technology of Cyperus esculentus was improved by irradiation.to provide theoretical and technical reference for the safe storage of Cyperus esculentus.(1)Determine the adsorption isotherm and thermodynamic properties of Cyperus esculentus.The equilibrium moisture content of Cyperus esculentus at different temperatures(15°C,25°C,35°C)and different water activity(0.113～0.979)was determined by static gravimetric method to determine the adsorption isotherm of Achsa at different temperatures and establish a model,and the thermodynamic properties of the adsorption isotherm model with the best fitting effect were used to determine its thermodynamic properties,including adsorption heat,entropy,specific surface area and Gibbs free energy.The results showed that the equilibrium water content increased with the increase of water activity and decreased with the increase of temperature.The adsorption isotherm of the Cyperus esculentus is s-type,which belongs to type II according to the Brunauer classification.Under the conditions of15°C,25°C and 35°C,the water content of the monolayer of the Cyperus esculentus was4.71%,4.49%and 4.24%,and the adsorption surface area was 166.37 m~2/g,158.46 m~2/g and149.74 m~2/g,respectively.The hygroscopic process of Cyperus esculentus is a spontaneous exothermic reaction.Based on the comprehensive test results,the safe storage moisture content of Cyperus esculentus is 11%.(2)Study on the influence of different storage conditions on the quality of Cyperus esculentus.Different temperatures(15°C,25°C,35°C),initial moisture content(9%,13%,17%),packaging method(conventional,nitrogen,vacuum)and irradiation processing(2 k Gy irradiation,unirradiation)were used to simulate the storage process of Cyperus esculentus(6months),and the changes of oil and oil quality during storage were explored.The results showed that the high temperature condition(35°C)had a great influence on the moisture content during the storage of the Cyperus esculentus under other conditions.The storage conditions had no obvious effect on the crude fat content in Cyperus esculentus.When irradiated(2 k Gy)or low initial moisture(9%),the mold rate of Cyperus esculentus is 0.Under other conditions,low-temperature(15°C)storage or low initial moisture content(9%)or vacuum and nitrogen packaging will delay the change of the physical and chemical properties of the oil in the Cyperus esculentus to a certain extent.During storage,the hydrolysis of triglycerides decreases and free fatty acids increase,resulting in an increasing acid value.Storage does not cause changes in the fatty acid types of oil in the Cyperus esculentus,but it will lead to an increase in saturated fatty acids.Medium to high moisture(13%,17%)was able to retainα-tocopherol during storage of samples with different initial moisture content.The content of oleosterols was highest at low temperature(15°C)storage.Nitrogen storage is the best way to retain carotenoids.Storage also reduces the phospholipid content and retains the phospholipid content of salsa oil stored under vacuum,nitrogen-filled or low-moisture(9%)conditions.In general,low temperature,low moisture content and vacuum and nitrogen-filled packaging are conducive to delaying the deterioration of the quality of Cyperus esculentus.(3)Study on the effect of irradiation processing on oil quality before and after storage.Different irradiation doses(0 k Gy,2 k Gy,4 k Gy,6 k Gy,8 k Gy)were used to irradiate the Cyperus esculentus,and combined with three months of storage,the changes of oil quality in the Cyperus esculentus were determined.The results showed that the acid price of Cyperus esculentus increased first and then decreased with the increase of irradiation dose.In addition,irradiation processing can lead to an increase in the degree of oxidation of oils and fats.Irradiation processing can reduce the content ofα-tocopherol and carotenoid in Cyperus esculentus and increase the content of phospholipid.The irradiation dose of 2 k Gy increases the plant sterol content,which decreases when it is greater than 2 k Gy.Irradiation processing had no significant effect on fatty acid species and oil structure of Cyperus esculentus.After three months of storage,the physicochemical properties of the oil deteriorated and the content of all trace components(sterols,α-tocopherols andβ-tocopherols,phospholipids and carotenoids)decreased.Based on the experimental results,2 k Gy is the ideal irradiation dose in the explored range.