Aqueous Enzyme Extraction、Modification Of Sheep Tail Oil And Its Application In Shortening

With the increase in consumer demand for meat fat,high-quality lamb resources in Bayannur have been developed and utilized.Among them,sheep tail fat,a by-product of lamb meat,has received extensive attention from researchers due to its rich fatty acid content,low molecular mass,unique flavor and high nutritional value.At the same time,sheep tail oil is also a popular choice for people on halal diets.However,existing methods of extracting animal fats and oils suffer from low oil yield,worse oil quality and serious loss of nutrients.Moreover,the high cholesterol content of sheep tail oil greatly limits its application in the food sector.Therefore,taking the fat of sheep tail as the research object,this paper investigates the ability of aqueous enzymatic extraction of sheep tail oil,the cholesterol-lowering effect of β-cyclodextrin and the effect of ultrasonic modification of sheep tail oil,providing a theoretical basis and technical support for the application of sheep tail oil in baking shortening.The major studies are as shown below:Firstly,the oil extraction effects of three proteases(Alcalase 2.4 L and Flavourzyme 1000 L and Protamex)were analyzed.Then,using the Protamex as the hydrolysis enzyme,the effects of protease amount,enzymatic temperature,enzymatic p H,enzymatic time and solid-to-liquid ratio on the basic physicochemical properties of sheep tail oil were investigated and the process parameters were optimized.The results showed that the effect of protease amount on the oil yield was most significant under the action of the protease Protamex,followed by the enzymatic temperature and p H.Under the optimal conditions of response surface optimization,the oil yield of sheep tail oil was as high as 90.31%,which was much higher than that of the traditional dry and wet boiling method(p < 0.05).In addition,the sheep tail oil obtained by aqueous enzyme extraction possessed lower peroxide value,higher oxidative stability and richer fatty acid content.The fatty acids were dominated by oleic(46.82%),palmitic(22.06%)and stearic(9.00%)acids and the major triglycerides contained 18:1/18:1/18:1(29.87%)and16:0/18:1/18:1(27.23%).These results show that the aqueous enzymatic method has higher oil extraction rate and can better protect the quality of the oil,which provides an idea and reference for the extraction of oil.Secondly,β-cyclodextrin was used to remove cholesterol from sheep tail oil and the variation in physicochemical properties were evaluated before and after treatment.The results showed that the cholesterol content in sheep tail oil obtained with 7% β-cyclodextrin,55°C stirring temperature,1:1 oil to water ratio and 60 min reaction time decreased from 69.38mg/100 g of crude oil to 2.28 mg/100 g.The acid value of sheep tail oil decreased and peroxide value increased after β-cyclodextrin treatment,and it did not significantly affect the type and content of fatty acids The acid value and peroxide value of β-cyclodextrin-treated sheep tail oil decreased and increased,but did not significantly affect the type and content of fatty acids.In addition,the viscosity of the low-cholesterol sheep tail oil was slightly reduced,which could reduce oil adherence during processing and thus reduce oil intake.These findings demonstrate that β-cyclodextrin embedding method is an efficient,green and safe method for cholesterol reduction and can further increase the added value of sheep tail oil.Subsequently,the low cholesterol sheep tail oil was used as raw material to further explore the effect of high intensity ultrasound on the crystallization behavior of oil.The isothermal crystallization curves showed that high intensity ultrasound shortened the crystallization induction period,increased the crystallization rate of the oil and made the crystalline particles become small and compact.By analysis of the results of X-ray diffractometer and melting curves,it was found that both β and β′ crystalline forms existed in the oils and fats,and the content of β′ crystalline increased after the ultrasonic treatment.At the same time,the higher the ultrasonic power and the longer the ultrasonic time,the more obvious effect of promoting the crystallization of the oil.In addition,the study of the physical and chemical properties of sheep tail oil showed that the viscosity of the oil was slightly reduced after ultrasonic treatment,but the effect on fatty acids was not significant.The above experimental findings suggest that ultrasonic treatment is a useful tool to assist in the crystallization of oils and fats.Finally,a high melting point baking shortening was developed using the stearin fraction of sheep tail oil after ultrasonic treatment and centrifuged.The data indicated that the shortening prepared after rapid cold kneading had similar appearance,solid fat content,thermodynamic properties,crystalline structure and microstructure to commercial shortening when the ratio of stearin fraction of sheep tail oil to palm stearin was 3:2 and the emulsifier formulation was molecular distillation of monoglyceride: phosphatidylcholine: SPAN 60 = 0.45:0.1:0.45.Furthermore,the results for solid fat content showed that the shortening prepared on the basis of the above-mentioned sheep tail oil had a good range of plasticity.The above conclusions can promote the application of sheep tail oil in the field of baking shortenings.