| Cannabis sativa L., has been an important traditional crop which has a widely cultivated area in China. However, the tetrahydrocannabinol(THC),which is responsible for the most psychoactivity in marijuana, is the major problem for the developing and utilizing of hemp and its products. Since non-drug varieties of Cannabis, commonly referred to as hemp, had been successfully cultivated in 1990s, the research of hemp has been highly stressed. But, so far, hempseed has just been used to produce hempseed oil, while defatted industrial hemp is underutilized and the majority is used for animal feeding purposes. Therefore the current urgent solution is how to realize its high effective utilization.In this work, the defatted industrial hemp proteins(DIHP) were prepared from hempseed, and their physicochemical, functionality, and nutritional properties were comprehensive studied. In additional, the suitable extraction process and functional properties of industrial hemp protein isolates(IHPI) were investigated. The emulsifying activity and emulsion stability of industrial hemp protein isolates and their relations to structure were fully studied in the different circumstance of temperature, pH, and ion intensity.To prepare IHPI, two main steps were adopted. Firstly, raw industrial hemp was defatted. And then a traditional method of alkali extraction and acid precipitation was used. The extraction of protein was optimized by using a there-level three-factor Box-Behnken design and response surface methodology. Under optimized condition(temperature 40℃,pH9.3, ratio of liquid to solid 24,time 0.5h), the protein yield reached 52.27%, and protein purity was 83.8%. The content of fat, moisture, ash and carbohydrate were respectively as follows: 0.3%, 4.01%, 1.5% and 5.63%.In order to know the basic information of a newly exploited vegetable protein, a classical method of Osborne was chosen to separate DIHP to four protein fractions. The content of these fractions were as follows: edestin (37.38%) and albumin (31.66%)were two major fractions, followed by Prolamine (3.95%) and glutelin(3.39%). All the estimated nutritional quality parameters based on amino acids composition showed that IHPI and DIHP protein fractions had good nutritional quality (E/T>36% and BV>2.00), especially albumin possessed high nutritional values. The protein fractions showed an excellent balance of amino acids except for a lacking of tryptophan and lysine. In vitro pepsin digestibility test, albumin and edestin showed highest values, while IHPI was the similar of that of commercial soy protein isolate(SPI).In conclusion, the IHPI and DIHP fractions were attractive and promising source of vegetable proteins with high nutritional properties.SDS-PAGE analysis showed that IHPI had 9 major distinct polypeptides bands with Mr 64.2, 59, 54.2, 35.4, 28.6, 24.1, 19.5, 17.9, 15.1kDa. Albumin showed five bands at Mr 54.2, 35.4, 28.6, 17.9, 15.1kDa. Edestin showed 8 major polypeptide bands with Mr 64.2, 59, 54.2, 35.4, 28.6, 19.5, 17.9, 15.1kDa. DSC analysis indicated that the endothermic peak of albumin and edestin were 74.02and94.00℃, while IHPI just between them, 84.83℃.IHPI possessed a better sensory acceptability, fat absorption, foaming and emulsifying properties compared with SPI, while a relatively low in water holding, solubility, and emulsifying capacity, which limited its functionality potential. CD spectra indicated that IHPI was a protein rich inα-helical andβ-sheet structure(almost 50%).The solubility and emulsifying properties of IHPI were diverse at different temperature, pH, and ionic strength. The results showed that change of emulsifying properties depended on several factors, such as protein concentration, group surface charge, space frame, temperature, pH, and ionic strength, and so on. In addition, the results showed emulsifying activity had a direct connection to protein concentration and ionic strength in solution, while it had not positively in accordance with Surface hydrophobicity. On the contrary, emulsifying stability was positively relevant to Surface hydrophobicity. |
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