Optimization Of Roasting Process Of Arabica Coffee And Detection And Analysis Of Physical And Chemical Indicators

Yunnan is one of the earliest coffee-growing provinces in China.Because of its unique natural conditions and geographical environment,arabica coffee bean has become one of the main crops in Yunnan Province.Due to the limitation of processing conditions,the main trade of arabica coffee bean in Yunnan Province is mainly based on raw beans,while further processing research such as roasting is not much.Based on the current situation of coffee industry in Yunnan,this paper researched on the roasting technology of Yunnan arabica coffee bean,and obtained the best roasting parameters with different roasting degrees.Secondly,the physical indexes of shallow roasting,medium roasting and deep roasting coffee beans,such as hardness,shear force,initial break ing force,and chemical indexes such as chlorogenic acid,caffeine,caffeic acid and fenugreene were improved.The correlation between physicochemical index and roasting degree was obtained by testing and analysis.Finally,according to the optimal roastin g parameters and main influencing factors of different roasting degree,the automatic control system of coffee roasting equipment was designed to automate the roasting process.The antioxidant index and nutrient content of manual roasting and automatic roasting coffee beans were tested and analyzed to verify the roasting.Feasibility and stability of automatic control system was tested.The main results and conclusions are as follows:(1)Coffee raw beans were roasted.Four main factors relating to the quality of coffee,including initial temperature,roasting time,roasting volume and opening and closing degree of air door,were selected for single factor and orthogonal test.The expansion rate,weight loss rate and sensory evaluation were taken as the evaluation indexes.The comprehensive weighted scoring method was used to analyze the data,and the optimum roasting parameters for shallow,medium and deep roasting of coffee were obtained.The optimal process parameters for shallow baking: initial temperature 240°C,roasting time 10 min,roasting amount 180 g,dam opening degree 14 mm;optimal process parameters for medium roasting: initial temperature 240°C,roasting time 12 min,roasting amount 220 g,damper opening degree 0 mm;optimal process parameters for deep roasting: initial temperature 250°C,roasting time 12 min,roasting amount 160 g,dam opening degree 7 mm.The significant factors affecting coffee roasting,initial temperature and roasting time,were obtained by variance analysis.(2)The physical and chemical indexes of light roasted,medium roasted and deep roasted coffee beans roasted by the optimum combination were tested.The hardness,shear force,initial rupture force,chromaticity value and sensory score of the coffee beans were obtained by compressing,shearing and colorimetric tests with a food property analyzer and a color difference meter.According to analysis of variance and correlation analysis,The results show that different degrees of baking have a significant effect on the physical indicators of coffee beans.The contents of chlorogenic acid,caffeine,caffeic acid,fenugreek alkali and fatty acid in coffee beans with different roasting degrees were determined by ultra-high performance liquid chromatography and gas chromatography,and then the antioxidant and nutrient contents were determined by ultraviolet spectrophotometer and crude fat analyzer.As the degree of baking deepens,the content of chlorogenic acid and caffeic acid gradually decreases,while the content of caffeine increases gradually.The content of fenugreek will increase first and then decrease,and the content of fatty acid will not change obviously with the deepening of baking degree.By comparing the physical and chemical indexes,the effe cts of different roasting degrees on the quality of coffee beans were obtained.(3)Through the variance analysis of the optimal process,it is found that the initial temperature and roasting time are the significant factors affecting the degree of coffee roasting.It is proposed that the initial temperature and roasting time are the parameters of the coffee automatic roasting control system.The optimal roasting parameters of shallow,medium and deep roasting are set in the system.According to the parameters set,different roasting processes can be realized automatically.Degree of coffee beans,thus reducing the coffee roasting process of artificial experience dependence.Then the indexes of antioxidant and nutrient components of coffee beans roasted manually and automatically are compared and analyzed.The results show that there i s no significant difference between the indexes of coffee beans roasted manually and automatically,which verifies the feasibility of the control system.