| In this experiment,Altay sheep hips fat was used as the test material.Firstly,the ultrasonic-assisted enzymatic extraction process was optimized through response surface methods,and the basic physical and chemical indicators of mutton oil were used as evaluation criteria to explore the effects of different extraction methods on the quality of mutton oil.At the same time,the refined mutton oil was modified by dry fractionation,and the best process was optimized through single factor test and response surface design,and the differences in the physical and chemical indexes and oxidation stability of the oil before and after the modification were compared and analyzed.The main results were as follows:(1)Ultrasound-assisted enzymatic hydrolysis for extraction of lanolin and comparison of physical and chemical indexes under different extraction methodsUsing Altay sheep hips fat as the test material,Based on single factor experiment,Plackett-Burman and Box-Behnken designs were combined to optimize the extraction conditions for ultrasound-assisted enzymatic hydrolysis.The optimal process parameters were represented: the ratio of material to liquid was1:2 g/m L,neutral protease addition was 1.00%,ultrasonic enzymatic hydrolysis temperature was 46℃,enzymatic hydrolysis time was 2 h,ultrasonic time was 34 min,and ultrasonic power was 200 W.Under these conditions,the yield of mutton oil was 79.98%,which was significantly higher than dry decocting(74.35%)and enzymatic hydrolysis(72.16%)(p<0.05).The melting point,saponification value and iodine value of the three methods were not significantly different(p>0.05).The peroxidation value(0.76 meq/kg)and acid value(0.86 mg/g)of fats obtained by ultrasonic-assisted enzymatic hydrolysis were significantly lower than dry,but the acid value was significantly higher than enzymatic hydrolysis(0.83 mg/g)(p<0.05).These results indicated that: compared with the traditional process,the optimized ultrasonic assisted enzymatic extraction process can increase the yield of sheep oil and improve the quality.(2)Optimization of the dry separation process of mutton oilThe refined mutton oil was used as the test material,single factor and response surface experiments were carried out to optimize the dry separation process of mutton oil,and the equilibrium temperature,crystallization temperature,crystal raising time and cooling rate were measured to study the effect of the soild yield of mutton and melting point.The results were represented: the equilibrium temperature was70℃,the crystallization temperature was 31℃,the crystallization period was 14.20 h,and the temperature drop rate was 2.80 ℃/h.Under this process condition,the solid fat yield was 24.37%,the melting point was41.80℃,and the melting range was 39～42℃,which is suitable for the development of shortening and other high melting point functional grease base oils.(3)Analysis of the difference in oxidation stability of mutton oil and its fractional componentsThe simulated rapid oxidation method was used to investigate the oxidative rancidity of mutton oil in different states.Taking changes in color difference,peroxide value,acid value and malondialdehyde at 0 d,3 d,6 d,9 d and 12 d as the standard.The results were as follows: with the prolongation of storage time,the various indicators of mutton oil in different states have changed significantly(p<0.05).Compared with crude oil,the peroxide value and acid value of fractionated liquid fat had a larger increase,while fractionated solid fat had a slower growth rate and better oxidation stability.But the malondialdehyde content of the solid fat increased faster,while the liquid fat was slowly.These results indicated that the quality of solid fat and liquid fat after dry fractionation was relatively stable,which can provide a certain theoretical basis for the prediction of the shelf life of functional oil products. |
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