| Mulberry seed oil(MSO)is a kind of vegetable oil rich in polyunsaturated fatty acids potential for health-care.It is liable to be oxidized when exposed to light,heat and oxygen.It may pose potential health hazards in the application.Emulsion is a common oil-water coexistence system in food.The emulsifier with good performance has obvious protective effect on oil in O/W system.This study,we investigated composition and thermal properties of fatty acids profiles of freshly squeezed MSO and construct an oil-in-water emulsion system stabilized by acid hydrolyzed egg albumin(AHEA)to protect MSO from oxidation.It has been well concern in food research field.The results are as follows:(1)Analysis of mulberry seeds and effect of antioxidants on the stability of MSO during the heating process.Mulberry seeds contained 38.81% of crude fat,22.10% of protein,free amino acids and total amino acods were 0.28and19.0g/100 g,respectively.The crude fat content in mulberry seeds is about 38.81% and consists of 16 amino acids.GC-MS analysis showed that the content of linoleic acid in MSO was almost 60%,the content of volatile components was abundant,and the content of esters was high,accounting for 20.96% of the total content of volatile components.Heat treatment of MSO at 160?oil bath showed that the sensory quality,antioxidant capacity and apparent viscosity of MSO decreased significantly with longer heating time;The BHT had a significant protective effect on MSO,compared with MSO without BHT,The downward trend of the indicators has obviously slowed down.(2)Construction of MSO/AHEA emulsion system.Egg albumin(EA)was incubated at pH 2.5 and 85? for 0,2,4,6,12,and 24 h,respectively.Six groups of samples with different degrees of hydrolysis were obtained,and then the pH was adjusted to neutrality.MSO/AHEA emulsion to build an oxidation protection system for MSO.SDS-PAGE analysis showed that acid hydrolysis of EA was evident.As the hydrolysis time prolonged,the bands of various proteins or subunits gradually became lighter,and at the same time,new bands with low molecular weight were generated;Surface hydrophobicity and intrinsic fluorescence intensity increased firstly and then decreased with increasing of hydrolysis time;Hydrolysis led to a more extended form of the secondary structure,?-helix regions decreased and ?-sheet regions increased.The DPPH radical scavenging efficiency and anti-lipid oxidative capacity of AHEA increased firstly and then decreased.Antioxidant ability is the strongest at 4h.The macroscopic stability of the emulsions after 4,6,and 12 h of hydrolysis in the six groups of emulsions was relatively good;the particle sizes of the emulsions that had been hydrolyzed for 4 or 6h were relatively small and the particle size distribution was relatively uniform;the six groups of emulsions all showed shear thinning during storage.The characteristics of the apparent viscosity and storage modulus with the degree of hydrolysis showed increased firstly and then decreased trend;the hydrolysis of the emulsion 4h minimum level.Comprehensive analysis,acid hydrolysis is conducive to improve the emulsifying capacity of EA.The hydrolysates of EA acid hydrolyzed for 4 hours had more hydrophobic residues and the best antioxidant capacity.(3)The influence of pH on hydrolyzed EA / LMP complex on storage stability of MSO emulsion.In the MSO/AHEA system,The addition of LMP has been conducive to prepare the protein-polysaccharide complex emulsion to further improve the stability of the MSO emulsifying system,and the influence of pH on the stability of the complex emulsion system was emphasized.The results showed that LMP promoted the adsorption of acid hydrolyzed EA at the water-oil interface,and the MSO/AHEA-LMP emulsion had better stability.At pH 8.0,the emulsion has the small particle size,the largest absolute value of ?-potential(51.26mV),and the smaller viscosity and storage modulus values.The stability of the emulsion prepared by the soluble complex formed by AHEA and LMP is the best. |
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