Optimization Of Roast Extract And Freeze-drying Process Of Cold Brew Coffee And Analysis Of The Components Of Process Change

Coffee is one of the most highly recognized beverage in the world.In this years,the cold brew coffee market is growing rapidly by the high body,low bitter taste,strong of Flower and fruit fragrance,clear and clean acidity.Cold brew coffee was fond of consumers in the market by better retains the flavor of the coffee itself.There are few reports on Freeze-dried cold brew coffee powder at present,.The factors affecting the quality of freeze-dried cold extract coffee powder are not clear.This study was explored and optimized for roast,cold extract and freeze-drying process of coffee powder and was used to analyze the components of coffee powder by GC-MS,research the changes in its composition.The main results and conclusions are as follows.The roast’s critical factor parameter study of coffee bean: Four factors of the highest roasting temperature,roasting time,opening degree of air door,and cooling time that affect the roasting quality of coffee beans were explored.Eight factors relating to the sensory of coffee,including,Fragrance/Aroma,Flavor,Aftertaste,Acidity,Sweetness,Body,Balance,Overall,The weight loss rate,chlorogenic acid content and sensory evaluation in the three evaluation indexes from orthogonal test for results.The optimal parameters for coffee bean’s roasting: highest roasting temperature was 235℃,roasting time was 14.5 min,opening degree of air door was90% and cooling time was 7 min.The weight loss rate was 17.53%,chlorogenic acid content was 17862 mg/kg and sensory evaluation was 0.9917 under this condition.The primary and secondary factors were highest roasting temperature>cooling time>opening degree of air door>roasting time.The cold extraction critical factor parameter study of coffee roasting beans: on the basis of single factor results,Box-Behnken Design was carried out on cold extraction.The result show that optimal parameters for coffee bean’s cold extraction: extraction temperature was 27.2℃,Extraction pressure was 3.3 MPa,powder ratio was 1∶11.6,grinding granularity was more than81.7% 20 mesh number and less than 4.7% 80 mesh number.The chlorogenic acid content was40702 mg/kg and solid matter yield was 18.6%.Moreover the grinding granularity was the biggest impact both of chlorogenic acid content and solid matter yield.The Freeze-dried cold brew coffee powder critical factor parameter study of coffee liquid.Measure the crystallize point of cold extract coffee liquid was-16℃～-18℃,eutectic point of cold extract coffee liquid was-12℃～-14℃.through the resistance method.Four factors relating to the Freezing time,maximum heating plate temperature,vacuum degree,thickness on single factor,The drying rate,moisture content,solution rate and sensory evaluation in the four evaluation indexes.The result was Freezing time 6h,maximum heating plate temperature 59℃,vacuum degree 62 Pa,thickness on single factor 0.99 cm through the Box-Behnken Design.And the drying rate was 3.32%/h,moisture content was 1.63%,solution rate was 5s,sensory evaluation was 82.Moreover it was found that the microstructure of spray-dried coffee powder,bad conditions and freeze-dried coffee powder and the best conditions freeze-dried coffee were quite different.According to the GC-MS analysis results found that the main ingredients in green Coffee beans,roasting coffee beans,cold extract coffee liquid and Freeze-dried cold brew coffee powder:Alcohols,Esters,Acids,Alkanes,Alkenes,Aldehydes,Ketones,Benzenes,Phenols,Oxoles,Pyrazines,Pyrroles,Pyridines and another.With the coffee roasting,cold extraction,Freeze-dried process,the number of substances produced is increased first and then reduced,Green coffee beans have 39 volatile ingredients,and elevates to 93 species after roasting.There have 104 species after the cold extraction and after Freeze-dried,it was greatly reduced to 38 species.