Study of the effect of microwave roasting method on volatile compounds and some physicochemical attributes and sensory properties of green coffee bean

Document Type : Research Paper

Authors

1 Department of Food Science and Technology, Islamic Azad University, Science and Research Branch, Tehran

2 Agricultural Sciences and Natural Resources University of Khuzestan

Abstract

Introduction: Coffee is one of the most popular beverages in the world, which contains large amounts of bioactive compounds and micronutrients that have beneficial effects on human health.
Raw and unprocessed coffee beans are green and have a weak flavor and must be roasted before consumption to achieve the desired taste and flavor. The composition of coffee varies greatly during roasting and many factors, including the roasting method, have a great impact on the type and amount of compounds in coffee. Microwave as one of the roasting methods has advantages that have expanded its application in food processing. The aim of this study was to compare the effect of using the microwave as one of the roasting methods on the physicochemical including the moisture content, hardness, instrumental color, antioxidant activity, type and amounts of aromatic compounds, and sensory properties of green coffee beans with the common method of using hot air. For this purpose, 200 g of coffee beans of uniform size were used for each one of the roasting treatments.
Materials and Methods: In the present study, Arabica green coffee (Coffea arabica) beans produced in Brazil were roasted using direct oven hot-air (220 °C) for 15 minutes and various microwave powers (650, 750, and 900 watts) for 1.5 minutes. Moisture content was measured by accurately weighing ground coffee samples after drying them in an oven at 105 °C until constant weight. The hardness of coffee beans was investigated using a wedge probe (A/WEG) connected to a Texture Analyzer TA-XT2i equipped with a load cell of 25 kg. Instrumental color characteristics including lightness (L*), redness (a*), and yellowness (b*) were measured using a Konica Minolta Colorimeter CR-400. The antioxidant activity of coffee beans was assessed by DPPH• radical scavenging assay. The aromatic compounds of coffee samples were extracted and identified by the solid-phase microextraction (SPME) method and gas chromatography-mass spectrometry (GC-MS), respectively. Organoleptic attributes of brewed coffee samples including appearance color, odor intensity, taste, and overall acceptability were evaluated with a group of 10-trained panelists using an 11-point scale. All experiments were carried out using a completely randomized factorial design and the data reported were the mean of a minimum of three replicates.
One-way analysis of variance (ANOVA) test was taken using SPSS Software and Duncan’s multiple range test was used to show significant differences of the mean values at P ≤ 0.05.
Results: The results of data analysis showed that the moisture content of coffee beans was significantly reduced by roasting and the lowest moisture content was observed in coffee roasted by microwave at 900 watts. The results also showed that roasting reduced the hardness of coffee and microwave-roasted beans had less hardness and the lowest texture hardness was observed in microwave-roasted coffee beans at 900 watts. Roasting decreased the lightness (L*) and increased the intensity of redness (a*) and yellowness (b*) of coffee beans, and in microwave-treated samples at higher powers, more differences were observed in the instrumental color characteristics of roasted coffee with the oven. The results revealed that the roasting process reduced the antioxidant activity of coffee in different concentrations; however, microwave-roasted coffees had more antioxidant activity than oven-roasted coffees. The results of the analysis of volatile compounds of coffee samples using solid-phase microextraction method by gas chromatography-mass spectrometer (SPME-GC/MS) showed that the content of total acidic compounds in roasted beans was significantly reduced compared to green coffee beans, while the amounts of alcoholic, ketone, aldehyde, furan, pyrazine and phenolic components in roasted coffees raised significantly compared to green coffee. The results showed that the roasting method had a significant effect on the type and amount of volatile compounds in coffee (p < 0.05). During the roasting process, some compounds were completely destroyed and some new compounds appeared instead. In the present study, the highest amount of volatile compounds was observed in coffee roasted by microwave at 650 watts. Furfuryl alcohol, 2-methylpyrazine γ-butyrolactone, and Pyridine were the predominant volatile compounds in roasted coffee. The results of the sensory evaluation showed that roasting had a significant effect on the sensory properties of coffee, so that roasting increased the acceptance of the appearance color of coffee, and coffee roasted by oven and microwave (650 watts) had the highest score. In addition, coffee roasted by microwave with a power of 650 watts had a significantly higher odor and taste score. Roasted coffee with 650 watts of microwave and oven had the highest overall acceptability, while samples prepared with 900 watts of the microwave with green coffee had the lowest overall acceptability.
Conclusion: In conclusion, based on the results of the present study, it could be stated that the use of microwave power at 650 watts due to the ability to create more aromatic components in coffee beans, better sensory acceptance, and more antioxidant activity could be a suitable method for roasting coffee beans.

Keywords


تقوی ن، ناطقی ل و برنجی ش، 1397، امکان سنجی تولید بستنی فراسودمند بر پایه فیبر قهوه سبز و دانه­های کفیر. نشریه پژوهش­های صنایع غذایی، 28(2)، 177-161.
Aguiar J, Estevinho BN, and Santos L, 2016. Microencapsulation of natural antioxidants for food application--the specific case of coffee antioxidants-A review. Trends in Food Science and Technology 58: 21–39.
Alinezhad M, Hojjati M, Barzegar H, Shahbazi S, and Askari H, 2021. Effect of gamma irradiation on the physicochemical properties of pistachio (Pistacia vera L.) nuts. Journal of Food Measurement and Characterization 15: 199–209.
Bobková A, Hudáček M, Jakabová S, Belej Ľ, Capcarová M, Čurlej J, Bobko M, Árvay J, Jakab I, Čapla J, and Demianová A, 2020. The effect of roasting on the total polyphenols and antioxidant activity of coffee. Journal of Environmental Science and Health Part B 55(5): 495-500.
Baggenstoss J, Poisson L, Kaegi R, Perren R, and Escher F, 2008. Coffee roasting and aroma formation: application of different time- temperature conditions. Journal of Agricultural and Food Chemistry 56: 5836–5846.
Bothiraj KV, and Vanitha V, 2020. Green coffee bean seed and their role in antioxidant–A review. International Journal of Research in Pharmaceutical Sciences 11(1): 233-240.
Budryn G, Nebesny E, Żyżelewicz D, Oracz J, Miśkiewicz K, and Rosicka-Kaczmarek J, 2012. Influence of roasting conditions on fatty acids and oxidative changes of Robusta coffee oil. European Journal of Lipid Science and Technology 114:1052–1061.
Ciaramelli C, Palmioli A, and Airoldi C, 2019. Coffee variety, origin and extraction procedure: Implications for coffee beneficial effects on human health. Food Chemistry 278:47-55.
Diviš P, Pořízka J, and Kříkala J, 2019. The effect of coffee beans roasting on its chemical composition. Slovak Journal of Food Sciences 13(1): 344–350.
Dong W, Cheng K, Hu R, Chu Z, Zhao J, Long Y, 2018. Effect of microwave vacuum drying on the drying characteristics, color, microstructure, and antioxidant activity of green coffee beans. Molecules 23(5):1146.
Giacalone D, Degn TK, Yang N, Liu C, Fisk I, and Münchow M, 2019. Common roasting defects in coffee: Aroma composition, sensory characterization and consumer perception. Food Quality and Preference 71: 463–474.
Gökcen BB, and Şanlier N, 2019. Coffee consumption and disease correlations. Critical Reviews in Food Science and Nutrition 59(2): 336-348.
Hojjati M, Lipan L, and Carbonell-Barrachina ÁA, 2016. Effect of roasting on physicochemical properties of wild almonds (Amygdalus scoparia). Journal of the American Oil Chemists' Society 93(9): 1211-1220.
Kim JW, Byun MS, Yi D, Lee JH, Jeon SY, Jung G, Lee HN, Sohn BK, Lee, JY, Kim YK, and Shin SA, 2019. Coffee intake and decreased amyloid pathology in human brain. Translational Psychiatry 9(1): 1-10.
Muñoz AE, Hernández SS, Tolosa AR, Burillo SP, and Herrera MO, 2020. Evaluation of differences in the antioxidant capacity and phenolic compounds of green and roasted coffee and their relationship with sensory properties. LWT 128:109457.
Nebesny E, and Budryn G, 2003. Antioxidative activity of green and roasted coffee beans as influenced by convection and microwave roasting methods and content of certain compounds. European Food Research and Technology 217: 157–163.
Nebesny E, Budryn G, Kula J, Majda T, 2007. The effect of roasting method on headspace composition of robusta coffee bean aroma. European Food Research and Technology 225:9–19.
O'Keefe JH, DiNicolantonio JJ, and Lavie CJ, 2018. Coffee for cardioprotection and longevity. Progress in Cardiovascular Diseases 61(1): 38-42.
Odžaković B, Džinić N, Jokanović M, and Grujić S, 2019. The influence of roasting temperature on the physical properties of Arabica and Robusta coffee. Acta Periodica Technologica 50:172-178.
Pan MH, Tung YC, Yang G, Li S, and Ho CT,  2016. Molecular mechanisms of the anti-obesity effect of bioactive compounds in tea and coffee. Food and Function 7: 4481–4491.
Perrone D, Farah A, and Donangelo CM, 2012. Influence of coffee roasting on the incorporation of phenolic compounds into melanoidins and their relationship with antioxidant activity of the brew. Journal of agricultural and food chemistry 60(17): 4265-4275.
Pittia P, Dalla Rosa M, and Lerici C, 2001. Textural Changes of Coffee Beans as Affected by Roasting Conditions. LWT 34: 168-175.
Pramudita D, Araki T, Sagara Y, and Tambunan AH, 2017. Roasting and colouring curves for coffee beans with broad time-temperature variations. Food and Bioprocess Technology 10(8):1509-1520.
Saeed Alkaltham M, Musa Özcan M, Uslu N, Salamatullah AM, Hayat K, 2020. Effect of microwave and oven roasting methods on total phenol, antioxidant activity, phenolic compounds, and fatty acid compositions of coffee beans. Journal of Food Processing and Preservation 44: 1–9.
Schenker S, Heinemann C, Huber M, Pompizzi R, Perren R, Escher F, 2002. Impact of roasting conditions on the formation of aroma compounds in coffee beans. Journal of Food Science 67: 60–66.
Shahidi F, and Nazck M, 1995. Food Phenolic Sources Chemistry Effects Applications, p 331. Lancaster-Basel: Technomic Publishing Company.
Wang X, and Lim LT, 2015. Physicochemical Characteristics of Roasted Coffee, In: Coffee in Health and Disease Prevention, Pp247–254. Academic Press.
Zhao Y, Jiang Y,  Zheng B, Zhuang W, Zheng Y, and Tian Y,  2017. Influence of microwave vacuum drying on glass transition temperature, gelatinization temperature, physical and chemical qualities of lotus seeds. Food chemistry 228: 167–176