Analysis of sizes, zeta potential and protein component of oil bodies extracted from different peanut varieties

Abstract: Oil bodies obtained from oilseeds will have extensive applications in the future, which serve as emulsifying agent for a wide variety of food products. Peanuts contain oil bodies that are coated by a layer of oleosin proteins that can absorb exogenous protein in the extraction. In nature, this protein coating protects the oil bodies from environmental stresses and may be utilized by food manufacturers in the process. Aqueous extraction was used to extract oil bodies from 5 different peanut varieties in the present work. The size distributions, zeta potentials, amino acid contents, and protein molecular weight distribution of oil bodies were the major focuses of this study with the purpose of offering scientific basis for the application of peanut oil bodies in food formulations. The results of size distribution analysis of oil bodies from 5 peanut varieties after aqueous extraction showed that the median diameter of oil bodies increased dramatically, and the order of increment degree was Yuhua9719 > Yuhua9830 > Yuhua23 > Yuhua27 > Yuhua9502. It was found that endogenous protein and exogenous protein existed in the surface of oil bodies extracted from 5 peanut varieties with aqueous media. And there existed clear difference in protein type and number. The results of zeta potentials under different external environmental condition showed that the zeta potentials of oil-body suspensions (in 10 mmol/L phosphate buffer) in different salt concentration (0-100 mmol/L) were positive at the pH value of 3.0, while the zeta potentials remained negative at the pH value of 7.4 and 9.0. It was also found that the levels of polar amino acid contents were higher than the non-polar amino acid, while the amount of negatively charged amino acids was bigger than the positively charged ones according to amino acid analysis of oil bodies extracted from 5 different peanut varieties. It indicated that there may exist some connection that oil bodies protein of more kinds and larger molecular were attributed to size distribution of wide range and large median diameter to some extent. It also demonstrated that the charge property of oil bodies was likely attributed to polar amino acid or non-polar amino acid contents and properties. These results suggest that oil bodies extracted from 5 peanuts varieties have different stability and may provide a new insight of choosing suitable peanut variety for the food industry.