The aim of this work was to investi

The aim of this work was to investigate the effect of vacuum roasting on acrylamide formation and reduction in coffee beans. To this purpose, low-pressure treatments combined or not with roasting at atmospheric pressure were applied, in order to achieve roasted beans comparable in terms of weight loss, residual moisture and colour. In order to compare the effects of the different roasting processes, data were expressed as a function of the thermal effectF, which represents the time–temperature combination received by coffee beans at each roasting time. The effect of the roasting processes on coffee sensory properties was also evaluated.
2. Materials and methods
2.1. Coffee beans
Green coffee beans ofCoffea arabicawith moisture content of 7.60 ± 0.01% by weight were used. They had length, width and depth mean values (n= 20) of 8.6 ± 0.6, 7.0 ± 0.3 and
3.4 ± 0.2 mm, respectively, and a sphericity of 0.01824 ± 0.00023 (Severa, Buchar, & Nedomovà, 2012).
2.2. Roasting
Experiments were conducted by using an apparatus consisting of an oven (5Pascal, VS-25 SC, Trezzano S/N, Milano, Italy), equipped with heated plates for optimal heat transfer under vacuum conditions, and connected to a vacuum pump. Roasting was carried out for increasing lengths of time at atmospheric pressure (hereafter called conventional roasting), at atmospheric pressure
for 10 min followed by vacuum treatment (0.15 kPa; hereafter called combined conventional-vacuum roasting), or under vacuum (i.e. 0.15 kPa; hereafter called vacuum roasting). Once the desired temperature was reached (i.e. 200 ± 1C), weighed aluminium dishes containing approximately 10 g of green coffee beans were introduced in the geometrical centre of the oven on a heated plate and the vacuum pump was immediately switched on. The time needed to achieve the desired vacuum
was less than 10 s. Computation of treatment duration started once the set pressure value was achieved. After the treatments, samples were immediately removed from the oven and cooled to room temperature. Afterwards they were transferred to plastic vessels with pressure lids and stored at 18C until analyses were performed. In all cases, the time between the end of the vacuum treatment and analytical determinations never exceeded 24 h.
2.3. Analysis of acrylamide
Acrylamide determination was performed according to the method ofBortolomeazzi, Munari, Anese, and Verardo (2012).In brief, acrylamide was extracted by 10 mL of water and the extract
purified by a single SPE column consisting of 0.5 g of a mixture of C18, strong cation (SCX) and anion exchange (SAX) sorbents in the ratio 2/1.5/1.5 (w/w/w). The quantitation was carried out by liquid chromatography-tandem mass spectrometry usingd3-acrylamide as internal standard. The relative response factor of acrylamide with respect tod3-acrylamide was calculated daily as the average of the response factors obtained by analysing a standard solution a minimum of three times.
2.4. Determination of total solid content
Total solid content was determined by gravimetric method (AOAC, 1995).
2.5. Weight loss
Sample weight roast loss (WL) was calculated as the percentage weight difference between the initial and final weights of the roasted sample.
2.6. Colour analysis
Colour analysis was carried out on ground sample using a tristimulus colorimeter (Chromameter-2 Reflectance, Minolta, Osaka, Japan) equipped with a CR-300 measuring head. The instrument
was standardised against a white tile before measurements. Colour was expressed inL⁄ , a
⁄ andb ⁄ scale parameters anda ⁄ andb ⁄ were used to compute the hue angle (tan 1 b ⁄ a ⁄ )(Clydesdale, 1978).
2.7. Temperature monitoring and thermal effect determination
Temperature changes of coffee during roasting were measured by a copper-constantan thermocouple probe (Ellab A/S, Hilleroed, Denmark), whose tip (2.0 mm) was placed on the coffee bean surface. The thermal effectF(min) was computed using the following equation (Ball, 1923): F¼ Zt 0 10
ðTTrÞ=z dt ð1Þ whereTr is the reference temperature, which was chosen equal to 200C, roasting processes being generally carried out at temperatures around 200C(Clarke, 1987), Tis the actual temperature of the treatment (C),tis the time (min) of the treatment, andzrepresents the increase in temperature that causes a 10-fold increase in the reaction rate, which was reported to be equal to 56C for the browning reaction of coffee (Sacchetti, Di Mattia, Pittia, & Mastrocola, 2009).
2.8. Sensory analysis
The procedure described byManzocco and Lagazio (2009)was followed. A panel of twelve Italian assessors was selected. Judges were usual coffee consumers, aged between 20 and 60 years and
approximately balanced between males and females. They all had a minimum of 2 years of experience in discrimination and descriptive sensory methods. For sensory testing, 5 g of coffee
powder were served in 50-mL capacity odourless plastic cups at ambient temperature. Coffee samples were indicated by a three-digit code and submitted to the panel paired with a reference sample (i.e. the conventionally roasted coffee powder). Assessors were asked to sniff the samples after the reference one and evaluate the intensity of odour, differentiating the treated sample from the reference sample on a 9-cm unstructured scale anchored with ‘‘reference’’ corresponding to the highest odour intensity. Due to coffee persistent flavour, only one sample was evaluated at each session and assessors evaluated the samples twice at different
sessions.
2.9. Image acquisition
Coffee powder images were acquired by using an image acquisition cabinet (Immagini & Computer, Bareggio, Italy) equipped with a digital camera (EOS 550D, Canon, Milano, Italy). In particular, the digital camera was placed on an adjustable stand positioned 60 cm above a black cardboard base where the Petri dish containing the sample was placed. Light was provided by 4 100-W frosted photographic floodlights, in a position allowing minimum shadow and glare. Images were saved injpegformat resulting in 34562304 pixels. M. Anese et al. / Food Chemistry 145 (2014) 168–172 169
2.10. Statistical analysis
Analyses were carried out at least twice in two replicated experiments; therefore each value is the average of at least four analyses. Coefficients of variation, expressed as the percentage ratio between the standard deviations and the mean values, were lower than 10 for acrylamide, weight loss and colour values, and 0.5 for total solid content. Analysis of variance was carried out and differences among means were assessed by using the Tukey or Student’sttest (STATISTICA for Windows, 5.1, Statsoft Inc., Cary, NC). Means were considered significantly different atp< 0.05.
3. Results and discussion
Fig. 1shows the temperature changes of coffee beans during conventional, combined conventional-vacuum and vacuum roasting. The temperature monitored during the vacuum treatment was lower than that recorded during the other two processes, especially in the initial stages of roasting. This can be explained by the higher rate of water vaporisation when compared with the process carried out at atmospheric pressure, due to the very low pressure generated inside the oven. As a consequence, different thermal effects (F) were obtained at the same length of roasting among the considered processes (Table 1). The degree of roast of coffee beans during conventional, combined conventional-vacuum, or vacuum roasting processes was evaluated by means of the weight loss determination (Table 1). As expected, in all cases, in the early stages of roasting coffee
weight loss proceeded faster than in the later stages and was mainly due to water evaporation. At the beginning of the

Hasil (Bahasa Indonesia) 2:

Tujuan dari penelitian ini adalah untuk mengetahui pengaruh memanggang vakum terhadap pembentukan akrilamida dan pengurangan biji kopi. Untuk tujuan ini, perawatan tekanan rendah dikombinasikan atau tidak dengan memanggang pada tekanan atmosfer yang diterapkan, dalam rangka mencapai kacang panggang sebanding dalam hal penurunan berat badan, kelembaban residual dan warna. Untuk membandingkan efek dari proses pemanggangan yang berbeda, data dinyatakan sebagai fungsi dari effectF termal, yang merupakan kombinasi suhu saat diterima oleh biji kopi pada setiap waktu pemanggangan. Pengaruh proses pemanggangan pada kopi sifat sensorik juga dievaluasi.
2. Bahan dan metode
2.1. Biji kopi
biji kopi hijau ofCoffea arabicawith kadar air 7.60 ± 0.01% berat digunakan. Mereka memiliki panjang, lebar dan kedalaman nilai rata-rata (n = 20) dari 8,6 ± 0,6, 7,0 ± 0,3 dan
3,4 ± 0,2 mm, masing-masing, dan kebulatan dari 0,01824 ± 0,00023 (Severa, Buchar, & Nedomovà, 2012).
2.2. Memanggang
Percobaan dilakukan dengan menggunakan alat yang terdiri dari oven (5Pascal, VS-25 SC, Trezzano S / N, Milano, Italia), dilengkapi dengan pelat dipanaskan untuk perpindahan panas yang optimal dalam kondisi vakum, dan terhubung ke pompa vakum. Pemanggangan dilakukan untuk meningkatkan panjang waktu pada tekanan atmosfer (selanjutnya disebut memanggang konvensional), pada tekanan atmosfer
selama 10 menit diikuti dengan pengobatan vakum (0,15 kPa, selanjutnya disebut gabungan memanggang konvensional-vakum), atau di bawah vakum (yaitu 0,15 kPa; selanjutnya disebut memanggang vakum). Setelah suhu yang diinginkan tercapai (yaitu 200 ± 1? C), ditimbang piring aluminium yang mengandung sekitar 10 g biji kopi hijau diperkenalkan di pusat geometris oven di piring panas dan pompa vakum segera diaktifkan. Waktu yang dibutuhkan untuk mencapai vakum yang diinginkan
adalah kurang dari 10 s. Perhitungan durasi pengobatan dimulai setelah nilai tekanan yang ditetapkan tercapai. Setelah perawatan, sampel segera dikeluarkan dari oven dan didinginkan sampai suhu kamar. Setelah itu mereka dipindahkan ke kapal plastik dengan tutup tekanan dan disimpan di? 18? C sampai analisis dilakukan. Dalam semua kasus, waktu antara akhir pengobatan vakum dan penentuan analitis pernah melebihi 24 jam.
2.3. Analisis akrilamida
penentuan Akrilamida dilakukan sesuai dengan metode ofBortolomeazzi, Munari, anese, dan Verardo (2012) .Dalam singkat, akrilamida diekstraksi dengan 10 ml air dan ekstrak
dimurnikan oleh SPE kolom yang terdiri dari 0,5 g campuran dari C18, kation kuat (SCX) dan anion exchange (SAX) sorben dalam rasio 2 / 1,5 / 1,5 (w / w / w). Kuantisasi yang dilakukan oleh cairan kromatografi-tandem mass spectrometry usingd3-akrilamida sebagai standar internal. Faktor respons relatif akrilamida dengan hormat tod3-akrilamida dihitung harian rata-rata faktor respon yang diperoleh dengan menganalisis larutan standar minimal tiga kali.
2.4. Penentuan kadar padatan total
Jumlah konten yang solid ditentukan dengan metode gravimetri (AOAC, 1995).
2.5. Berat badan
penurunan berat badan Contoh panggang (WL) dihitung sebagai perbedaan persentase berat antara bobot awal dan akhir dari sampel panggang.
2.6. Analisis Warna
analisis Warna dilakukan pada sampel tanah menggunakan colorimeter tristimulus (kromameter-2 reflektansi, Minolta, Osaka, Jepang) yang dilengkapi dengan kepala pengukuran CR-300. Instrumen
adalah standar terhadap ubin putih sebelum pengukuran. Warna itu diungkapkan inL/, a
parameter / andb / skala Andari / andb / digunakan untuk menghitung sudut rona (tan? 1 b / a /) (Clydesdale, 1978).
2.7. Pemantauan suhu dan efek termal penentuan
perubahan suhu kopi selama memanggang diukur dengan probe termokopel tembaga constantan (Ellab A / S, Hilleroed, Denmark), yang ujungnya (2,0 mm) ditempatkan pada permukaan biji kopi. The effectF termal (min) yang dihitung dengan menggunakan persamaan berikut (Ball, 1923): F¼ Zt 0 10
dt TRTH = z dt ð1Þ whereTr adalah suhu referensi, yang dipilih sama dengan 200 C, proses pemanggangan yang umumnya dilakukan??? pada suhu sekitar 200? C (Clarke, 1987), Tis suhu sebenarnya perlakuan (? C), tis waktu (menit) pengobatan, andzrepresents peningkatan suhu yang menyebabkan peningkatan 10 kali lipat dalam reaksi rate, yang dilaporkan sama dengan 56? C untuk reaksi pencoklatan kopi (Sacchetti, Di Mattia, Pittia, & Mastrocola, 2009).
2.8. Analisis sensori
Prosedur dijelaskan byManzocco dan Lagazio (2009) diikuti. Sebuah panel dua belas penilai Italia dipilih. Hakim adalah konsumen kopi biasa, berusia antara 20 dan 60 tahun dan
sekitar seimbang antara laki-laki dan perempuan. Mereka semua memiliki minimal 2 tahun pengalaman dalam diskriminasi dan metode deskriptif sensorik. Untuk pengujian sensorik, 5 g kopi
bubuk disajikan dalam 50-mL kapasitas gelas plastik berbau pada suhu kamar. Sampel kopi yang ditunjukkan dengan kode tiga digit dan diserahkan ke panel dipasangkan dengan sampel referensi (yaitu bubuk kopi konvensional panggang). Penilai diminta untuk mengendus sampel setelah referensi satu dan mengevaluasi intensitas bau, membedakan sampel diperlakukan dari sampel referensi pada skala terstruktur 9-cm berlabuh dengan '' referensi '' sesuai dengan intensitas bau tertinggi. Karena kopi rasa terus-menerus, hanya satu sampel dievaluasi pada setiap sesi dan penilai mengevaluasi sampel yang berbeda dua kali di
sesi.
2.9. Akuisisi citra
kopi bubuk gambar diperoleh dengan menggunakan kabinet akuisisi citra (Immagini & Komputer, Bareggio, Italia) dilengkapi dengan kamera digital (EOS 550D, Canon, Milano, Italia). Secara khusus, kamera digital ditempatkan pada berdiri disesuaikan diposisikan 60 cm di atas dasar karton hitam di mana cawan Petri yang berisi sampel ditempatkan. Cahaya disediakan oleh 4 100-W lampu sorot fotografi buram, dalam posisi yang memungkinkan bayangan minimum dan silau. Gambar yang disimpan injpegformat menghasilkan 3456? 2304 piksel. M. anese et al. / Food Chemistry 145 (2014) 168-172 169
2.10. Analisis statistik
Analisis dilakukan setidaknya dua kali dalam dua percobaan direplikasi; Oleh karena itu setiap nilai adalah rata-rata minimal empat analisis. Koefisien variasi, dinyatakan sebagai persentase rasio antara standar deviasi dan nilai rata-rata, lebih rendah dari 10 untuk akrilamida, penurunan berat badan dan nilai-nilai warna, dan 0,5 untuk kandungan total solid. Analisis varians dilakukan dan perbedaan di antara cara-cara yang dinilai dengan menggunakan Tukey atau Student'sttest (STATISTICA untuk Windows, 5.1, Statsoft Inc, Cary, NC). Berarti dianggap ATP yang berbeda secara signifikan <0,05.
3. Hasil dan diskusi
Gambar. 1shows perubahan suhu biji kopi selama konvensional, dikombinasikan konvensional-vakum dan memanggang vakum. Suhu dipantau selama terapi vakum lebih rendah dari yang tercatat selama dua proses lainnya, terutama pada tahap awal pemanggangan. Hal ini dapat dijelaskan oleh tingkat yang lebih tinggi dari penguapan air bila dibandingkan dengan proses yang dilakukan pada tekanan atmosfer, karena tekanan yang sangat rendah yang dihasilkan di dalam oven. Akibatnya, efek termal yang berbeda (F) diperoleh pada panjang yang sama memanggang antara proses dianggap (Tabel 1). Tingkat panggang biji kopi selama konvensional, dikombinasikan konvensional-vakum, atau proses pemanggangan vakum dievaluasi dengan cara penentuan penurunan berat badan (Tabel 1). Seperti yang diharapkan, dalam semua kasus, pada tahap awal memanggang kopi
penurunan berat badan berlangsung lebih cepat dari pada tahap selanjutnya dan terutama karena penguapan air. Pada awal