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Budi Rahardjo
Jurusan Teknik Pertanian, Fakultas Teknologi Pertanian Universitas Gadjah Mada Jl. Sosio Yustisia, Yogyakarta 55281

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Perubahan Suhu, Kadar Air, Warna, Kadar Polifenol dan Aktivitas Antioksidatif Kakao Selama Penyangraian dengan Enerji Gelombang Mikro Supriyanto Supriyanto; Haryadi Haryadi; Budi Rahardjo; Djagal Wiseso Marseno
agriTECH Vol 27, No 1 (2007)
Publisher : Faculty of Agricultural Technology, Universitas Gadjah Mada, Yogyakarta, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (198.485 KB) | DOI: 10.22146/agritech.9489

Abstract

Heat penetrated slowly during conventional roasting of cocoa resulting in possibly less effective and gradation change. In this experiment microwave energy was applied to reast cocoa nib. The objective of this research was to study changes of temperature, moisture content, color, polyphenol content and antioxidative activity during microwave roasting of ground cocoa nibs. Ground cocoa nib passing through 20 mesh screen wa contained on glass bowl, and then heated in a microwave oven for 2-12 min. Conventional roasting using electric oven at 140ºC for 40 min was conducted for comparison. The result indicated that microwave roasting took a shorter time compared to that using conventional method as shown by the increasing temperature rate and the decreasing rate of moisture and polyphenol contents, i.e.10, 11 and 13 times faster than those given by the conventional roasting, respectively. Microwave roasting was more suitable for high roasting to get dark brown product. The trends of inhibition of linoleic acid oxidation by the product roasted using micorwave energy were similar to that of conventionally roasted, ground cocoa, i.e. 85-90%. A longer roasting of ground cocoa nibs was caused the polyphenol content in product more minimize, but this matter did not have an effect on reality to antioxidative activity of this product.ABSTRAKPada penyangraian biji kako cara konvensional proses pemanasan berlangsung lambat, sehingga tidak efisien dan senyawa dalam biji kako banyak mengalami perubahan terutama kandungan polifenol dan aktivitas antioksidatifnya. Penelitian ini bertujuan untuk menentukan pengaruh penyangraian keping biji kakao menggunakan enerji gelombang mikro (EGM) terhadap perubahan suhu, kadar air, warna, kandungan polifenol dan aktivitas antioksidatif produk yang dihasilkan, dibandingkan dengan penyangraian konvensional. Hancuran keping biji kako lolos ayakan 20 mesh sebanyak 50 g, ditempatkan dalam mangkok gelas, dipanaskan dalam oven  EGM 900 watt, 2450 MHz selama 2 sampai dengan 12 menit pada power 20%. Penyangraian konvensional dilakukan menggunakan oven listrik pada suhu 140ºC  selama 20 menit sampai dengan 140 menit. Hasil penelitian menunjukkan bahwa penyangraian dengan EGM menghasilkan kenaikan suhu 10 kali lebih besar, penurunan kadar air dan kansungan polifenol masing-masing 11 dan 13 kali lebih besar, dibandingkan dengan penyangraian konvensional. Penyangraian menggunakan EGM lebih cocok untuk penyangraian tingkat berat dengan produk yang berwarna coklat kehitaman. Pola perubahan aktivitas penghambatan oksidai asam linoleat selama penyangraian menggunakan EGM adalah serupa dengan pola perubahan pada penyangraian konvensional, dengan nilai antara 85-90%. Selama penyangraian kandungan polifenol menurun, dengan pola mendekati garis lurus. Perubahan kandungan polifenol selama penyangraian tidak berkorelasi secara nyata dengan perubahan aktivitas penghambatan oksidasi asam linoleat.
Pengaruh Penyangraian dengan Enerji Gelombang Mikro Terhadap Polifenol dalam Hancuran Keping Biji Kakao Supriyanto Supriyanto; Haryadi Haryadi; Budi Rahardjo; Djagal Wiseso Marseno
agriTECH Vol 26, No 3 (2006)
Publisher : Faculty of Agricultural Technology, Universitas Gadjah Mada, Yogyakarta, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1477.265 KB) | DOI: 10.22146/agritech.9592

Abstract

Polyphenols play important roles in taste and flavour development as well as antioxidative property of cocoa products. Chemical changes of the polyphenols occurring during conventional roasting was due to exposure to the oxygen of surrounding air at high temperature(110-200oC) for 20 up to 60 min, depend on the degree of roasting. Shorter time was needed to roast the cocoa nib by using microwave energy. The objective of this research was to investigate changes of polyphenol compounds during microwave roasting of ground cocoa nibs. Deshelled and ground cocoa nib passing through 20 mesh screen was roasted using microwave oven at 20% power for 5 min. Conventional roasting conditions were also adopted for treating the sample using an electric oven at 140 oC for 40 min as comparison. The polyphenols was extracted with acetone 80% and then freez dried. The crude extract was characterized for total polyphenols. Polarity of the polyphenolic fractions was analyzed from the crude extract as well as the ethyl acetate soluble extract by HPLC. Chemical bond of the compounds were detected by Fourier Transform Infrared Spektrophotometer (FTIR). Results indicated that the conventional roasting tend to decrease the polyphenols content while microwave roasting was increase, though the data showed significantly no difference (p≤0,05) . HPLC separation suggested that the roasting of the sample  increased in polarity, though FTIR spectra showed similarity in quantity of O-H, C-H, and C=C bonds respectively The microwave oven roasting gave one small additional fraction compared to both sample extracts from the conventional roasted and the unroasted samples which gave two fractions. Further, the ethyl acetate soluble extract from the microwave sample gave eight chromatographic fractions while from those conventional roasted and the unroasted gave two fractions and one fraction, respectively.