The Preparation Technology And The Quality Of Amygdalus Pedunculata Seed Oil

At present,China ranks first in world consumption of vegetable oil,and as 60%of oil is imported,new varieties of edible oil have to be produced.Amygdalus pedunculatus(A.pedunculatus)is effective against desertification;its production can therefore have significant social impact and economic value.This paper studies the pretreatment,the extraction method,and the physicochemical properties of Amygdalus pedunculatus seed oil(APO).Its oxidation stability,shelf life prediction and cooking stability were also studied.The details are as following:(1)The thousand kernel weight and pure kernel yield of A.pedunculatus seeds from different districts in China(Yulin,Shaanxi,Alashan and Baotou,Inner Mongolia and Chengde,Hebei)were compared;the general composition and amygdalin content of A.pedunculatus seeds were determined;the fatty acid,triacylglycerol,polyphenol,tocopherol,phytosterol component of A.pedunculatus oil were analysed.Our results showed that crude fat and protein constituted 70%weight of the A.pedunculatus seeds,while amygdalin content was 3%.The A.pedunculatus seeds could be processed to edible oil,protein powder and amygdalin,but the amygdalin should be removed off,then the protein powder could be available as edible protein powder.A.pedunculatus oil was rich in oleic acid and linoleic acid,as the concentration of each was up to 95 wt%.Moreover many other nutrients such as polyphenols,tocopherols and phytosterols were also detected in APO.(2)Four pretreatment methods of A.pedunculatus seeds' were used;they were microwaving(M),roasting(R),steaming(S)and roasting plus steaming(RS).The oils obtained from the different processing treatments were compared to the oil obtained from raw seeds(RW)without processing.The oils obtained from these seeds with a cold press process were analyzed in detail;in particular,we examined the crude oil quality in terms of yield,color change,physicochemical property,nutritional content,benzopyrene concentration and oxidative stability.Our results showed the oils from different pretreatment techniques had a huge difference in physicochemical property and nutrients;benzopyrene,however was never detected.Compared to the oil obtained from raw seeds(RW)without processing,the oleic acid content and oxidative stability of the oils obtained from different processing treatments were higher;the linoleic acid content,on the contrary,was lower than the RW oil.This led to a lower Cox value and a higher OSI value.The acid value,peroxide value,CD and 2-TBA values of the oils obtained from pretreated seeds all increased when oils were stored in a Schaal oven at 65 ?.However,polyphenol and tocopherol contents decreased in all oil samples,but the oxidative speed was not different.The benzopyrene content of the R and RS oil didn't exceed the national standard limit of 10 ug/kg,the oils from RW,S,M exceeded the limit.Pretreating the seeds had a more evident effect in the oil sample obtained through RS technique,which showed higher oxidative stability than the other processed oils and RW oil.(3)The objective of the present study was to compare APO quality change according to different extraction techniques,such as aqueous enzymatic extraction(AEE),cold-press(CP),supercritical fluid extraction(SFE),and Soxhlet extraction(SE)from seeds of two regions in China(Yulin Shaanxi,Baotou Inner Mongolia).Physicochemical properties,nutrients(fatty acids,triacylglycerol,polyphenol,tocopherol and phytosterol)and fluorescence characteristic of the oils were determined.The results indicated that the same oil extraction method,the APO from each region had its advantages;SFE was found to be the optimum method for APO extraction with higher nutrient contents as well as better fluorescence characteristics.Considering the nutritional content,the extraction methods could be ranked as AEE>SE>CP.(4)APO oxidation stability of samples obtained by cold pressing(CP)and supercritical fluid extraction(SFE)was determined;this was done by measuring their peroxide values during oven storage 65,50,40,30,20 ?;Rancimat test was also used to evaluate the oxidation stability of A.pedunculatus oil as well as of other oils(olive oil,tea oil,rapeseed oil).The results showed that the nutrients content of the oil extracted by SFE(SFEO)was higher than that of the oil obtained with CP(CPO);although APO oxidization was accelerated with increasing storage temperature,its oxidation stability was higher than that of the other oils.The oxidation reaction of CPO and SFEO followed a first order kinetic model;the shelf-life of CPO and SFEO at 30 ? was 84d and 90d,respectively.(5)To study APO cooking stability,rapeseed oil(RSO)was used as a comparasion.The changes of the physical and chemical properties,nutrition profile and harmful substances formation were explored under different temperature conditions 100?130?160?180 and 210 ?.The results showed that,APO cooking stability was far higher than that of RSO therefore,APO was suitable to be used as high quality cooking oil.With increasing cooking temperature and time,AV and p-AV of the two oils both increased,while POV increased and later decreased.The contents of SFA and MUFA all increased,but the contents of PUFA and tocopherol both decreased significantly.Several harmful substances(trans fatty acids,benzoyrene and polar material)could be detected;APO,however,showed lower concentrations of these chemicals in comparison with RSO.Morever,they were produced at higher cooking temperature and for longer cooking times than for RSO.