Proses penggorengan bahan makanan sumber pati :: Kajian nisbah Amilosa-Amilopektin

SUPRIYANTO, Promotor Prof.Dr.Ir. Budi Rahardjo, MSA.Eng

2007 | Disertasi | S3 Ilmu Pertanian

Penggorengan merupakan suatu cara memasak bahan makanan. Perubahan fisik: dan kimia teijadi pada bahan makanan selama proses penggorengan. Prosesproses perubahan tersebut dapat diprediksi menggunakan model matematik. Penelitian ini bertujuan untuk mengembangkan model matematik proses penggorengan bahan makanan sumber pati. Nisbah amilosa - amilopektin dipilih sebagai fokus kajian karena kedua fraksi tersebut berpengaruh pada perubahan sifat fisik: dan kimia bahan makanan sumber pati selama proses penggorengan. Sampel yang digunakan dalam penelitian ini adalah jagung varietas Bisma dan Ketan. Tepung jagung campur dipersiapkan dengan cara mencampur tepung Bisma dan Ketan dengan lima macam variasi, yaitu : (100 : 0), (75 : 25), (50 : 50), (25 : 75) dan (0 : 100). Campuran kedua varietas jagung tersebut menghasilkan fraksi amilopektin (rasio amilopektin terhadap total pati) masingmasing : 0,80, 0,83, 0,87, 0,91 dan 0,94. Tepung jagung diproses mencapai pra-gelatinisasi, dicetak dan dikukus selama 60 menit, sampel menjadi bentuk produk semi-basah. Produk digoreng dengan variasi suhu minyak dan waktu penggorengan. Perubahan fisik: dan kimia pada bahan makanan sumber pati selama proses penggorengan, meliputi: peningkatan suhu, penurunan kadar air, peningkatan kadar minyak, pemekaran, pencoklatan, dan perubahan kadar pati resisten. Model matematik dikembangkan untuk fenomena yang teijadi pada bahan makanan sumber pati selama proses penggorengan, yaitu : proses transfer panas, transfer massa air dan massa minyak, hubungan antara nilai konduktifitas panas (k) dan kapasitas panas spesifik (Cp) dengan suhu dan kadar air, pemekaran dan perubahan kadar Hydroxymethyl Furfural (HMF). Proses transfer panas diformulasikan dengan hukum Fourier sedangkan proses transfer mas sa cairan dimodelkan dengan hukum Picks. Hubungan antara nilai k dan Cp dengan suhu dan kadar air bahan dimodelkan dengan model regresi linier. Model regresi polinomial pangkat dua digunakan untuk memodelkan proses pemekaran. Proses perubahan kadar furfural diformulasikan dengan model kinetika reaksi kimia orde I. Hasil penelitian membuktikan bahwa model-model matematik yang dikembangkan adalah valid. sehingga model dapat digunakan untuk memprediksi riwayat suhu, kadar air, kadar minyak, perubahan nilai k dan Cp, pemekaran volume dan perubahan kadar HMF pada proses penggorengan. Penelitin ini juga membuktikan bahwa terjadi peningkatan kadar pati resisten pada produk goreng makanan sumber pati. Peningkatan fraksi amilopektin dalam bahan makanan sumber pati menyebabkan : perlambatan proses transfer panas dan massa, penurunan nilai k dan Cp, peningkatan volume pemekaran, penurunan nilai konstante perubahan kadar HMF dan peningkatan kadar pati resisten selama proses penggorengan

Frying is a method of food cooking. Physical and chemical properties are change in starchy food during frying process. The changes can be predicted mathematically. The objective of this research was to develop the mathematics model of frying processes of starchy food. The Ratio of Amylose to Amylopectin was chosen as the focus of the study because those fraction were hipothized to affect the change of chemical and physical properties of starchy food during frying. Two varities of com, i.e : Bisma (high amylose) and Ketan (high amylopectin) were used as the ~pies in this study. Mixed flour was prepared with five variations of Bisma and Ketan, i.e.: (1 00 : 0), (75 : 25), (50 : 50), (25 : 75), and (0 : 100) resulted in amylopectin fraction (ratio amylopectin to total starch) of: 0.80; 0.83; 0.87; 0.91; and 0.94 respectively. The mixed flour was pre gelatinized, shaped, and steamed for 60 minutes, then dried to a semi-dry mass. The semi-dry product was fried in different time and oil temperature. There were some change the physical and chemical properties, those were increasing temperature, decreasing of water content, increasing of oil content, swelling, browning, and the change of resistant-starch content. The heat and mass transfer of oil and water, relation between heat conductivity (k) and specific heat capacity (Cp) with temperature and water content, swelling and the change of Hydroxymethyl Furfural (HMF) content during the process of frying were formulated on mathematical models. The heat transfer process was formulated with Fourier law and the liquid mass transfer process with Ficks law. The relation between k and Cp value with temperature and water content were formulated with the linear regression model. The two degree of Polynomial regression was used to make swelling model. The process of Furfural content change was modeled with chemical reaction kinetics. The result showed that those mathematic models were valid for the object studied, therefore the models could be used to predict the history of temperature, water content, and oil content; the change of k and Cp values, swelling volume and Furfural content change during frying process. This study also showed that the resistance-starch content on fried starchy food was increased. The increasing of amylopectin fraction on starchy food caused decelerating of heat and mass transfers, decreasing of k and Cp value, increasing of swelling volume, decreasing of constant value of Furfural content change, and increasing of resistance starch content during frying process.

Kata Kunci : Bahan Makanan SUmber Pati,Proses Penggorengan,Nisbah Amilosa,Amilopektin