Effects Of Lipids On Physicochemical And Antioxidant Properties Of Coffee Colloidal Particles

Coffee is rich in polysaccharides,oils,polyphenols and other active substances,with antioxidant,anti-inflammatory and other biological effects.The chemical composition of coffee also shapes the unique sensory characteristics of coffee.Lipids can alleviate the bitterness of coffee to a certain extent and enhance the lubricity of coffee entrance.As a polyphasic system,colloidal particles contained in coffee are rarely studied,and their active constituents and contributions to the overall sensory and functional aspects of coffee are unclear.In addition,the determination of coffee antioxidant is mainly chemical methods,and there are few intracellular antioxidant tests that are more closely related to physiological state.In this study,different coffee samples were prepared by selecting different grind sizes and temperature,and the colloidal particles of coffee were separated by membrane filtration,and the main chemical components such as lipids,colloid properties and extracellular and intracellular antioxidant properties were measured.The distribution of lipids and other components in different phases was explored by comparing with the relevant indexes of coffee stock solution and its true solution.On this basis,the correlation between lipid content in colloidal phase and sensory characteristics and antioxidant activity of coffee was further investigated.By adding different concentrations of oil to coffee liquid and homogenizing treatment,the simulation of coffee with different lipid content was conducted to determine the differences in physicochemical,physiological and tribological activities of these samples.The specific results were as follows:1.There were differences in chemical composition,colloid properties and antioxidant properties of coffee liquids prepared by hot brewing and cold brewing of coffee powder with different grind sizes.The dissolution rate of lipids and other components under hot brewing condition was higher than that of cold-brewing coffee.The results of colloidal property characterization showed that compared with cold brewing coffee,coffee was more likely to produce colloidal particles under hot brewing conditions,and hot brewed coffee was more likely to form a monodisperse system.The dissolution rate of different chemical components of coffee samples was highly correlated with the antioxidant properties.Different components of coffee had a certain proportion of distribution in the colloidal phase,of which the proportion of lipid distribution was large,and some samples even had more than 50% of the lipid in the colloidal particles.Coffee colloid showed different levels of antioxidant activity in both intracellular and extracellular assay methods,indicating that the unique physical and chemical properties of coffee colloid particles contributed significantly to the overall antioxidant capacity of coffee.2.The effects of different types and contents of lipids on physicochemical properties,sensory characteristics and antioxidant activity of coffee colloidal particles were investigated by adding coffee oil and cream and homogenizing emulsification respectively.The results showed that with the increase of the added lipid content from 0.37 mg/m L to 1.50 mg/m L,the lipid participated in the formation of colloidal particles in coffee to varying degrees.With the increase of lipid content of colloidal particles,there was no significant difference in the extracellular antioxidant activity,but a certain negative correlation with the strength of intracellular antioxidant capacity.In tribology,the friction coefficient of adding coffee oil increases with the increase of lipid content,and the lipid content bound to colloidal particles in coffee increased from 0.55 mg/m L to 1.15 mg/m L,while the free lipid content was relatively small.The friction coefficient of adding cream showed a decreasing trend,in which the lipid content combined with colloidal particles in coffee was relatively small,while the free lipid content was more.It is speculated that the friction coefficient changes due to the combined action of lipids and free lipids combined with coffee colloidal particles.The research on this aspect plays an important role in understanding the lipids in coffee and the correlation between "lipids","colloidal particles" and "sensory and antioxidant properties",which provides basic data support for the research and development of new coffee products.