Preparation Of Sacha Inchi Proteins And Their Physical-chemical Properties

Plukenetia volubilis L., known as sacha inchi is a climbing, perennial plant native to the Peruvian Amazon. Its seeds are rich in protein and high quality oil, important in human nutrition and applications in health, cosmetics and medicine. The protein content in Plukenetia volubilis L. cake is 54%-56%. Because of our lack of understanding of the Plukenetia volubilis L. proteins, as well as the present low-level of development, the cake is used as animal feed or discarded, resulting in a serious waste of protein resources.This paper mainly studies preparation of Plukenetia volubilis L. protein isolate and protein concentrate by alkali extraction and acid precipation procedure and alcohol washing separation, accordingly. The extraction processing was optimized through response surface analysis and orthogonal experiment. The structures of the proteins were carefully studied. The functional properties of PPI, PPC and commercial Soy Protein Isolate were analyzed and compared. A method for the determination of contents of morin, hesperitin, and naringenin in Plukenetia volubilis L. cake and protein was established by HPLC. The naringenin and tannins contributing to the unpleasant flavor were researched by studying the contents and dose-over-threshold of those two constutents. Main conclusions of the study are as follows:(1)By use of the Box-Behnken experimental design method, the effects of the ratio of liquid, p H, extraction time and temperature and their interactions on the protein extraction rate were studied on the base of the single-factor test. The test results showed that the optimum conditions of alkali-solution and acid-isolation extraction for Plukenetia volubilis L. protein were as following: the ratio of liquid 20:1(m L/g), p H10.5, extraction time 1.80 hour, extraction temperature 42 ℃. The influence order of factors to protein extracting rate is reaction temperature> ratio between solid and liquid >p H> reaction time. Under these conditions, the rate of protein extraction reached 82.97%.(2)Sacha Inchi proteins were prepared and dried through vacuum freeze-drying and spray drying separately. Their secondary structure and functional properties were analyzed and compared. The experimental results show that the secondary structure and hydrophobicity are different between the samples via different drying methods. The content of β-corner increased up to 30.0% and the disordered structure nearly disappeared completely through spray drying, while the disulfide bond increased from 6.79 μmol/g to 12.18 μmol/g.(3) By measuring protein solubility, water-holding properties, oil absorption, emulsifying properties, foam properties and viscosity, functional properties of the proteins were studied.The physical-chemical properties of the proteins, obtained via the two different drying methods, were compared at various temperature, p H and concentration. The experimental results show that oil-holding capacity of the proteins reached the maximum at 55 ℃with the value about 200%. Solubility of Sacha Inchi protein decreased with increasing temperature from 25 ℃ to 55 ℃. Viscosities of Sacha Inchi protein decreased with elevating temperatures from 20 ℃ to 70 ℃. The foam ability and the emulsify activity index, stability property of Sacha Inchi protein increased with increasing concentration. The properties including solubility, oil-holding capacity, water absorption of Sacha Inchi proteins through vacuum freeze-drying are better than those via spray drying; in addition, the emulsify activity index and stability by the former method is much better than that by spray drying.(4)By use of the Orthogonal experimental design method, the effects of the ratio of liquid, elution temperature, elution time, ethanol concentration and elution times were studied on the base of the single-factor test. The alcohol washing separation test results showed that the optimum conditions of extraction Sacha Inchi proteins were as following: ethanol concentration 70%, the ratio of liquid 10: 1(m L/g), elution times is 4, elution temperature 50 ℃.(5)The purpose is also to establish a method for the determination of contents of morin, hesperitin, and naringenin in Plukenetia volubilis L. cake and protein by HPLC. The mobile phase consisted of acetonitrile-0.1% phosphoric acid; the flow rate was 0.5 m L/min and the detection wavelength was set at 324 nm. The column temperature was 30 ℃. The naringenin and tannins contributing to the unpleasant flavor were researched by studying the contents and dose-over-threshold of those two constutents.