【作者】 张琪；

【导师】 张海德；

【作者基本信息】 海南大学 ， 食品加工与安全， 2023， 硕士

【摘要】 咖啡具有独特的风味,咖啡因对人体的刺激作用以及生理活性成分带来的健康益处,使咖啡成为世界上最受欢迎的饮料之一。随着人们的生活水平的提高,消费者对咖啡的品质要求也提高,速溶咖啡和即饮咖啡不再能满足消费群体的需求,现磨咖啡采用新鲜烘焙的咖啡豆进行研磨冲泡,能最大程度的保留咖啡的香气和风味,掀起一波热潮。因此,为帮助消费者更好地了解咖啡冲泡过程中不同萃取参数对品质的影响,为冲泡一杯品质较好咖啡提供理论依据。本研究以海南咖啡豆为原料,对咖啡豆进行不同程度烘焙,探究不同萃取工艺,对咖啡的化学组分、抗氧化能力以及浅烘焙咖啡豆中丙烯酰胺含量的影响,并通过响应面优化得到最佳萃取工艺,对不同温度冲泡咖啡中可溶性固形物含量（Total dissolved solids,TDS）进行一阶、二阶萃取动力学模型拟合,建立TDS的预测模型,实现咖啡冲泡程度的预测。主要研究内容及结果如下:（1）咖啡豆烘焙度的研究。探究了不同烘焙度与生豆之间的理化指标的变化,结合感官评价,中深度烘焙的咖啡感官评价得分最高,浅度烘焙的绿原酸含量较高但检测出丙烯酰胺最高。因此,基于咖啡品质与健康的考虑,同时选取两个烘焙度咖啡进行后续萃取工艺的试验。（2）萃取工艺对咖啡萃取液品质的影响。在不同研磨度、萃取温度、粉水比（咖啡粉/水,质量比）、萃取时间等条件下冲泡咖啡,探究不同萃取工艺对咖啡化学组分的影响,为得到咖啡最佳萃取工艺的研究,通过对不同萃取条件下咖啡的品质进行综合评分,随着温度的升高得到的评分越高,温度在92℃得分最高,在92℃萃取温度下,以研磨度、萃取时间、粉水比作为试验因素,综合评分作为响应值,响应面模型分析得到最佳萃取工艺:研磨度为中度、粉水比为1:20、萃取时间为2 min。（3）萃取工艺对咖啡萃取液抗氧化能力的影响。浅度烘焙咖啡的萃取液抗氧化能力明显高于中深度烘焙咖啡,研磨度越细,冲泡咖啡的抗氧化能力越强;抗氧化能力因粉水比变小而降低,在料液比为1:10时抗氧化活性最高;不同烘焙度咖啡萃取液的抗氧化能力都随时间延长而增大,在5 min时达到最大值,浅度、中深度烘焙咖啡萃取液的ABTS自由基清除率分别为1.48 mmol/L、1.36mmol/L,DPPH自由基清除率为5.41 mmol/L、4.91 mmol/L;随着温度的升高,ABTS和DPPH自由基清除率也越来越高,这表明烘焙过程中发生的化学和物理变化而产生抗氧化物质,在萃取温度较高的情况下,咖啡萃取液中总酚类物质含量较高。（4）萃取工艺对丙烯酰胺含量的影响。丙烯酰胺含量因研磨度越细,萃取得到的含量就越高,最高含量为16.28±0.58 ng/m L,说明咖啡粉的粒径越小,丙烯酰胺溶于水中的速率越快;丙烯酰胺含量与粉水比有关,粉水比为1:15时高于粉水比为1:10的,丙烯酰胺含量增加14.56%,当继续增大水的量,丙烯酰胺含量没有加大的趋势;萃取时间对丙烯酰胺含量的影响基本与粉水比一致,前3min丙烯酰胺含量随萃取时间增加而增加,3 min后趋于平稳,可能是因为丙烯酰胺易溶于水,所以咖啡中的丙烯酰胺在3 min内几乎可以完全被提取。（5）咖啡冲泡程度预测模型的建立。将不同温度下冲泡咖啡的TDS浓度变化数据进行一阶、二阶动力学模型拟合,相比较一阶动力学模型,不同温度下冲泡咖啡的TDS浓度二阶动力学模型拟合的相关系数R²更好,都达到0.99以上,与数据拟合程度较好,能更好的阐释咖啡冲泡过程中TDS的萃取动力学过程。根据不同冲泡温度下TDS浓度随萃取时间变化的试验数据,通过计算推导得到咖啡冲泡过程中TDS浓度的二阶动力学模型参数,建立咖啡冲泡程度的预测模型为:TDS_t=t/(0.71×10^-3exp（3120/T）+[t/（0.1519-2.078）])更多还原

【Abstract】 Coffee has a unique flavor,caffeine’s stimulating effects on human body and the health benefits of physiologically active ingredients,have made coffee one of the most popular beverages in the world.With the improvement of people’s living standards,consumers also have higher requirements for the quality of coffee,the instant coffee and ready-to-drink coffee no longer meet the needs of consumer groups.Freshly ground coffee uses freshly roasted coffee beans to grind and brew,which can retain the aroma and flavor of coffee to the greatest extent and set off a wave of upsurge.Therefore,to help consumers better understand the impact of different extraction parameters on the quality of the coffee brewing process,and to provide a theoretical basis for brewing a better quality cup of coffee.To explore the effects of different extraction processes on the chemical composition,antioxidant capacity and acrylamide content in light roasted coffee beans,using the Hainan coffee beans as raw material,with different levels of roasting.The optimal extraction process was obtained by response surface optimization.To fit the first-order and second-order extraction kinetic models of Total dissolved solids（TDS）content in coffee brewed at different temperatures,and to establish the prediction models of TDS content to realize the prediction of coffee brewing degree.The main study contents and results are as follows:（1）Research on the degree of roasting of coffee beans.To explore the changes of physical and chemical indicators between different roasting degrees and green beans,were combined with sensory evaluation,the sensory evaluation score of medium-dark roasted coffee was the highest,and the light roasted coffee had higher chlorogenic acid content but the highest detection of acrylamide.Consider coffee quality and health,Based on the impact on human health,selecting two roast degrees coffees for the subsequent extraction process test.（2）Effect of extraction process on quality of coffee extract.To explore the effects of different extraction processes on the chemical components of coffee,which was brewed under different grinding degree,extraction temperature,powder/water ratio（coffee powder/water,mass ratio）,extraction time and other conditions.In order to obtain the best extraction process of coffee,by comprehensively scoring the quality of coffee under different extraction conditions.As the temperature increases,the higher the score is,the highest score is obtained at 92℃,the grinding degree,extraction time,and powder-to-water ratio were used as the test factors,and the combined score was used as the response value.The optimal extraction process was obtained by response surface model analysis:medium grinding degree,powder to water ratio was 1:20,and extraction time was 2 min.（3）Effect of extraction process on the antioxidant capacity of coffee extracts.The antioxidant capacity of the light roasted coffee extract is significantly higher than that of the medium-dark roasted coffee.The finer the grind,the stronger the antioxidant capacity of brewed coffee;the antioxidant capacity decreases due to the smaller powder-to-water ratio.The antioxidant activity was the highest at 1:10;the antioxidant capacity of coffee extracts with different roast degrees increased with time,and reached the maximum at 5 minutes.1.48 mmol/L,1.36 mmol/L,DPPH free radical scavenging rate is 5.41 mmol/L,4.91 mmol/L;ABTS and DPPH radical scavenging also increased with increasing temperature,which indicates that the production of antioxidant substances due to chemical and physical changes that occur during the roasting process,and the higher content of total phenolics in the coffee extracts at higher extraction temperatures.（4）Effect of extraction process on acrylamide content.The finer the grinding degree,the higher the content of acrylamide extracted,the highest content is 16.28±0.58 ng/m L;The content of acrylamide was related to the ratio of powder to water.When the ratio of powder to water was 1:15,the content of acrylamide increased by14.56%compared with that when the ratio of powder to water was 1:10.Continuing to increase the amount of water,the acrylamide content did not tend to increase;the effect of extraction time on the acrylamide content was basically consistent with the powder-to-water ratio,and the acrylamide content increased with the increase of extraction time in the first 3 min,and leveled off after 3 min,probably because acrylamide is easily soluble in water,so the acrylamide in coffee could be almost completely extracted in 3min.（5）Establishment of a prediction model of coffee brewing degree.The first-order and second-order kinetic models were fitted to the TDS concentration variation data of coffee brews at different temperatures.Compared with the first-order kinetic model,the correlation coefficient R2 of the second-order kinetic model fitted to the TDS concentration of coffee brewed at different temperatures was better,all reaching above0.99 which can better explain the extraction kinetics of TDS during the coffee brewing process.The second-order kinetic model parameters of TDS concentration in coffee brewing process were derived by calculation based on the experimental data of the variation of TDS concentration with extraction time at different brewing temperatures.The prediction model of coffee brewing degree is established as follows.follows:TDS_t=t/(0.71×10^-3exp（3120/T）+[t/（0.1519-2.078）])更多还原