Khamir Sebagai Kultur Starter dalam Proses Fermentasi untuk Meningkatkan Cita Rasa Kopi Robusta Pelangi

Abstract

Proses pemanenan buah kopi pada perkebunan rakyat umumnya dilakukan oleh petani secara tanpa seleksi dengan upaya untuk menghemat waktu sehingga menghasilkan panen buah kopi pelangi, yaitu buah kopi dengan tingkat kematangan berbeda. Kopi yang diproduksi dari buah kopi pelangi memengaruhi cita rasanya, sementara itu sortasi kopi buah matang merah akan memerlukan tenaga dan waktu serta merubah kebiasaan petani memanen kopi dengan tingkat kematangan yang seragam sulit digantikan dalam waktu singkat. Permasalahan tersebut akhirnya memunculkan upaya dalam memperbaiki cita rasa kopi robusta melalui penelitian pada proses pengolahan kopi yang memiliki peran besar untuk menentukan kualitas kopi yang dihasilkan termasuk cita rasa, yaitu melalui proses fermentasi. Tujuan penelitian ini adalah untuk mempelajari parameter fisik fermentasi dan dinamika mikrob kultur starter selama fermentasi kopi, mengevaluasi pengaruh kultur starter terhadap degradasi substrat gula serta efisiensinya dalam memproduksi enzim pektinolitik dan menemukan metode pengolahan kopi yang dapat meningkatkan cita rasa kopi robusta pelangi serta jenis inokulum kultur starter, dilihat dari aspek parameter fisik fermentasi, perubahan komposisi senyawa selama fermentasi serta penilaian sensori kopi robusta. Proses fermentasi dilakukan dengan metode basah selama 48 jam dengan menguji coba perlakuan inokulasi khamir sebagai kultur starter fermentasi kopi dan tanpa inokulasi sebagai kontrol. Sampel buah kopi terdiri dari buah kopi pelangi, yaitu buah kopi panen acak tanpa sortasi yang menghasilkan tingkat kematangan beragam dan buah kopi merah, yaitu buah kopi kematangan maksimal yang diperoleh dari hasil sortasi. Proses penelitian dimulai dari persiapan inokulum kultur starter, proses pengolahan kopi dan proses analisis penelitian. Rancangan percobaan penelitian ini menggunakan Rancangan Acak Lengkap Faktorial dengan dua faktor, yaitu jenis buah kopi merah dan pelangi dan jenis inokulum kultur starter (Saccharomyces cerevisiae Y612, Candida parapsilosis Y207, and Torulospora delbrueckii Y594). Analisis data dengan menggunakan ANOVA dan uji lanjut Tukey dengan taraf kepercayaan 5%. Ketiga inokulum kultur starter masing-masing digunakan sebanyak 30 mL dengan kepekatan 10^8 sel/mL dan diinokulasi pada proses fermentasi 5 kg biji kopi basah dalam 3 L air. Selama proses fermentasi tersebut parameter fisik fermentasi yang dianalisis setiap 12 jam sekali di antaranya adalah suhu, nilai pH dan aktivitas pertumbuhan kultur starter. Suhu yang tercatat selama fermentasi berfluktuasi dengan suhu awal fermentasi sekitar 24,67 – 25,5 °C dan suhu akhir fermentasi ditutup dengan kenaikan suhu yang tercatat sekitar 26,22 – 27,00 °C. Nilai pH selama fermentasi tercatat terus mengalami penurunan hingga fermentasi berakhir, mulai dari 5,74 – 6,05 menurun hingga mencapai 4,24 – 4,67. Nilai pH tertinggi didominasi oleh kopi fermentasi non-inokulum, sementara itu nilai pH terendah diperoleh sampel kopi merah inokulum C. parapsilosis Y207. Inokulum T. delbrueckii Y594 merupakan kultur starter yang memiliki aktivitas pertumbuhan tertinggi selama proses fermentasi kopi. Jumlah populasi kultur starter T. delbrueckii Y594 pada 12 jam pertama fermentasi sebanyak 7,47±0,16 log CFU/mL, terus meningkat selama fermentasi hingga mencapai jumlah 8,89±0,24 log CFU/mL. Buah kopi pelangi fermentasi non-inokulum merupakan sampel yang memperoleh aktivitas pertumbuhan mikrob terendah yang ditemukan selama fermentasi kopi. Perbedaan jumlah populasi mikrob selama fermentasi ini dipengaruhi oleh jenis inokulum kultur starter dan jenis buah kopi merah dan pelangi yang difermentasi. Aktivitas enzimatik menjadi indikator proses fermentasi kopi berlangsung, poligalakturonase merupakan salah satu enzim pektinolitik yang bertugas mendegradasi pektin pada lapisan lendir biji kopi. Aktivitas enzim tersebut mengalami peningkatan pada 12 jam pertama, kemudian menurun hingga proses fermentasi berakhir. Sampel buah kopi merah dengan inokulum S. cerevisiae Y207 memperoleh aktivitas enzim tertinggi sebesar 16,82 U/mL pada fermentasi 12 jam pertama sehingga dapat dikatakan spesies tersebut lebih efisien dalam meningkatkan aktivitas enzim selama fermentasi . Aktivitas poligalakturonase yang terjadi selama proses fermentasi kopi dipengaruhi oleh jenis buah kopi merah dan pelangi serta jenis inokulum kulutur starter pada fermentasi. Penurunan kadar gula terjadi selama proses fermentasi kopi berlangsung untuk jenis gula fruktosa, glukosa, dan sukrosa. Kadar fruktosa menurun dari 71,27–72,57 mg/g menjadi 69,00–71,07 mg/g, kadar glukosa menurun dari 26,30– 30,64 mg/g menjadi 10,20–18,72 mg/g, dan kadar sukrosa menurun dari 7,94–8,41 mg/g menjadi 7,44–7,61 mg/g. Perubahan kadar gula pada fermentasi kopi lebih banyak mengalami penurunan walaupun sedikit mengalami kenaikan pada beberapa sampel dan pada jam tertentu. Perlakuan fermentasi lebih berpengaruh nyata terhadap perubahan kadar glukosa dibandingkan dengan fruktosa dan sukrosa. Kadar kafein kopi robusta yang difermentasi dengan kultur starter bernilai lebih tinggi dibandingkan dengan fermentasi non-inokulum. Buah kopi pelangi inokulum S. cerevisiae Y612 memperoleh penilaian terbaik dari skor total kopi robusta yaitu sebesar 82,10. Penilaian sensori antara buah kopi merah dan pelangi yang difermentasi dengan kultur starter tidak mengalami perbedaan yang signifikan, namun berbeda signifikan pada fermentasi kontrol. Hasil penilaian keseluruhan dari atribut sensori kopi menunjukkan bahwa kopi yang difermentasi dengan inokulum S. cerevisiae Y612 berhasil meningkatkan cita rasa kopi robusta pelangi, sehingga metode tersebut menjanjikan untuk diaplikasikan pada pengolahan kopi.

The process of harvesting coffee cherries on smallholder plantations is generally carried out by farmers without selection in an effort to save time so as to produce a rainbow coffee berry harvest, namely coffee cherries with different maturity levels. Coffee produced from rainbow coffee cherries affects its taste, meanwhile sorting red ripe fruit coffee will require effort and time and changing the habits of farmers to harvest coffee with a uniform level of ripeness is difficult to replace in a short time. This problem eventually led to efforts to improve the taste of Robusta coffee through research on the coffee processing process which has a big role in determining the quality of the coffee produced including the taste, namely through the fermentation process. The purpose of this study was to study the physical parameters of fermentation and microbial dynamics of starter culture during coffee fermentation, evaluate the effect of starter culture on sugar substrate degradation and its efficiency in producing pectinolytic enzymes and find coffee processing methods that can improve the taste of Robusta Pelangi coffee and the type of starter culture inoculum, seen from the aspect of physical parameters of fermentation, changes in compound composition during fermentation and sensory assessment of robusta coffee. The fermentation process was executed using the wet method for 48 hours by testing the yeast inoculation treatment as a starter culture for coffee fermentation an without inoculation as a control. The coffee cherries sample consisted of rainbow coffee cherries, which are randomly harvested coffee cherries without sorting which produce various levels of maturity and red coffee cherries, which are the maximum ripeness coffee cherries obtained from the sorting results. The research process starts from the preparation of starter culture inoculum, the coffee processing process and the research analysis process. The experimental design of this study used a completely randomized factorial design with two factorial designs with two factors, red and rainbow coffee cherries and starter culture inoculum types (Saccharomyces cerevisiae Y612, Candida parapsilosis Y207, and Torulospora delbrueckii Y594)., Data analysis using ANOVA and Tukey’s test with a confidence level of 5%. The three starter culture inoculums were used as much as 30 mL each with a concentration of 10^8 cells/mL and were inoculated in the fermentation process of 5 kg of wet coffee beans in 3 L of water. During the fermentation process, the physical parameters of the fermentation were analyzed every 12 hours including temperature, pH value and growth activity of the starter culture. The temperature recorded during the fermentation fluctuated with the initial temperature of fermentation around 24,67 – 25,5 °C and the temperature at the end of the fermentation was closed with a temperature increase recorded around 26,22 – 27,00 °C. The pH value during fermentation was recorded to continue to decrease until the fermentation ended, the pH of the first 12 hours of fermentation was recorded at 5,74 – 6,05 and the final pH value of fermentation was 4,24 – 4,67. The highest pH value was dominated by non-inoculum fermented coffee, while the lowest pH value was obtained by red coffee sample inoculum C. parapsilosis Y207. Inoculum T. delbrueckii Y594 is a starter culture with the highest growth activity during the coffee fermentation process. The total population of T. delbrueckii Y594 starter culture in the first 12 hours of fermentation was 7,47 ± 0,16 log CFU/mL, which continued to increase during fermentation until it reached 8,89a ± 0,24 log CFU/mL. Non-inoculum fermented rainbow coffee cherries were samples that obtained the lowest microbial growth activity found during coffee fermentation. The difference in the number of microbial populations during this fermentation was influenced by the type of starter culture inoculum and the type of fermented red and rainbow coffee cherries. Enzymatic activity is an indicator of the coffee fermentation process taking place, polygalacturonase is one of the pectinolytic enzymes to degrade pectin in the mucilage layer of coffee beans. The enzymes activity increased in the first 12 hours, then decreased until the fermentation process ended. Samples of red coffee fruit with S. cerevisiae Y207 inoculum obtained the highest enzyme activity of 16,82 U/mL in the first 12 hours of fermentation so that it can be said that these species are more efficient in increasing enzyme activity during fermentation. The activity of polygalacturonase that occurs during the coffee fermentation process is influenced by the types of red and rainbow coffee cherries and the type of starter culture inoculum during the fermentation process. A decrease in sugar levels occurs during the coffee fermentation process for fructose, glucose, and sucrose types of sugar. Fructose levels decreased from 71,27– 72,57 mg/g to 69,00–71,07 mg/g, glucose levels decreased from 26,30–30,64 mg/g to 10,20–18,72 mg/g g, and sucrose levels decreased from 7,94–8,41 mg/g to 7,44– 7,61 mg/g. Changes in sugar content during coffee fermentation experienced a decrease, although it experienced a slight increase in several samples and at certain hours. Fermentation treatment had a more significant effect on changes in glucose levels compared to fructose and sucrose. The caffeine content of robusta coffee fermented with starter culture is higher than that of non-inoculum fermentation. Rainbow coffee fruit inoculum S. cerevisiae Y612 received the best taste of robusta coffee with 82.10%. The sensory assessment between red and rainbow coffee cherries fermented with starter culture did not have a significant difference, however it was significantly different in the control fermentation. The results of the overall assessment of the sensory attributes of coffee show that coffee fermented with S. cerevisiae Y612 inoculum has succeeded in improving the quality of rainbow robusta coffee, so this method is promising for application in coffee processing.