Modifikasi Debranching Dan Gelombang Mikro Untuk Meningkatkan Pati Resisten Pada Tepung Beras Hitam (Oryza Sativa L. Indica)

Abstract

Beras hitam (Oryza sativa L. indica) mengandung pati sebagai komponen utama yang tersusun atas amilosa dan amilopektin. Modifikasi struktur pati merupakan salah satu pendekatan yang dapat digunakan untuk meningkatkan pembentukan pati resisten (resistant starch), yaitu fraksi pati yang tidak tercerna di usus halus dan berperan sebagai komponen pangan fungsional. Modifikasi pati dapat dilakukan secara enzimatis melalui proses debranching maupun secara fisik menggunakan gelombang mikro yang mampu mengubah struktur dan sifat fisikokimia pati. Penelitian ini bertujuan menganalisis pengaruh perlakuan debranching, gelombang mikro, dan kombinasi keduanya terhadap karakteristik fisikokimia tepung beras hitam, meliputi kadar pati resisten, daya cerna pati, komposisi proksimat, kadar amilosa dan amilopektin, profil pasting, serta tipe kristalinitas pati. Modifikasi tepung beras hitam dilakukan melalui tiga perlakuan, yaitu gelombang mikro, debranching, dan kombinasi gelombang mikro–debranching. Perlakuan gelombang mikro dilakukan pada daya 700 W selama 3 menit, sedangkan perlakuan debranching menggunakan enzim pullulanase dengan aktivitas 50 U/g dan waktu inkubasi 16 jam. Pada perlakuan kombinasi, tepung terlebih dahulu diberi perlakuan gelombang mikro kemudian dilanjutkan dengan proses debranching. Setelah proses modifikasi, seluruh sampel didinginkan pada suhu 4°C selama 24 jam untuk mendorong proses retrogradasi, kemudian dikeringkan pada suhu 40°C selama 24 jam sebelum dilakukan analisis. Hasil penelitian menunjukkan bahwa perlakuan debranching dan gelombang mikro mampu meningkatkan kadar pati resisten secara signifikan dibandingkan tepung beras hitam tanpa perlakuan. Sebaliknya, kombinasi gelombang mikro–debranching menyebabkan penurunan kadar pati resisten. Di antara seluruh perlakuan, debranching merupakan metode yang paling efektif dalam meningkat-kan karakteristik fungsional tepung beras hitam karena menghasilkan peningkatan pati resisten yang diikuti penurunan daya cerna pati. Hasil analisis fraksi pati menunjukkan bahwa perlakuan debranching menurunkan kadar Rapidly Digestible Starch (RDS) dan meningkatkan Slowly Digestible Starch (SDS). Kondisi ini diduga berkaitan dengan terbentuknya struktur kristalin yang lebih teratur sehingga menghambat hidrolisis oleh enzim pencernaan. Sebaliknya, perlakuan gelombang mikro meningkatkan kadar RDS dan menurunkan SDS yang diduga terkait dengan meningkatnya proporsi daerah amorf pati sehingga proses hidrolisis berlangsung lebih cepat. Peningkatan daya cerna pati juga teramati pada perlakuan kombinasi gelombang mikro–debranching. Komposisi proksimat yang meliputi kadar air, abu, protein, dan lemak menunjukkan variasi antar perlakuan. Modifikasi pati juga memengaruhi struktur kristal pati. Perlakuan debranching mempertahankan tipe kristalinitas A, sedangkan perlakuan gelombang mikro dan kombinasi gelombang mikro–debranching menghasilkan kristalinitas tipe V yang mengindikasikan kemungkinan terbentuk-nya kompleks amilosa–lipid. Perubahan struktur pati akibat perlakuan modifikasi turut memengaruhi sifat pasting tepung beras hitam. Seluruh perlakuan menye-babkan penurunan nilai peak viscosity (PV), breakdown viscosity (BV), setback viscosity (SV), dan final viscosity (FV). Sementara itu, suhu pasting meningkat pada perlakuan debranching dan gelombang mikro. Pada perlakuan kombinasi, suhu pasting tidak terdeteksi, yang mengindikasikan bahwa granula pati telah mengalami kerusakan dan gelatinisasi yang lebih intens sehingga transisi gelatinisasi tidak dapat diamati selama pengukuran profil pasting. Perlakuan debranching dan gelombang mikro juga meningkatkan kadar amilosa yang diikuti penurunan kadar amilopektin. Perubahan tersebut berkaitan dengan pemutusan cabang amilopektin dan perubahan struktur granula pati selama proses modifikasi. Sebaliknya, perlakuan kombinasi menyebabkan penurunan kadar amilosa yang diduga akibat kerusakan struktur pati yang lebih intens. Selain itu, seluruh perlakuan modifikasi menyebabkan penurunan kadar pati total. Secara keseluruhan, modifikasi pati melalui pendekatan enzimatis dan fisik mampu mengubah karakteristik fisikokimia tepung beras hitam dan meningkatkan nilai fungsionalnya. Perlakuan debranching merupakan metode yang paling efektif untuk meningkatkan kadar pati resisten dan menurunkan daya cerna pati, sehingga berpotensi digunakan dalam pengembangan pangan fungsional berbasis beras hitam. Sebaliknya, kombinasi gelombang mikro–debranching perlu dikendalikan secara cermat karena dapat menyebabkan kerusakan struktur pati yang berlebihan dan menurunkan pembentukan pati resisten.

Black rice (Oryza sativa L. indica) contains starch as its major component, consisting primarily of amylose and amylopectin. Starch structure modification is one of the approaches that can be employed to enhance the formation of resistant starch, a fraction of starch that escapes digestion in the small intestine and functions as a beneficial component of functional foods. Starch modification can be achieved through enzymatic treatment, such as debranching, or through physical treatment using microwave irradiation, both of which can alter the structural and physicochemical properties of starch. This study aimed to evaluate the effects of debranching, microwave treatment, and their combination on the physicochemical characteristics of black rice flour, including resistant starch content, starch digestibility, proximate composition, amylose and amylopectin contents, pasting properties, and starch crystallinity. Black rice flour was modified using three different treatments: microwave treatment, debranching, and a combination of microwave treatment followed by debranching. Microwave treatment was performed at 700 W for 3 minutes, whereas debranching was carried out using pullulanase at an enzyme activity of 50 U/g with an incubation period of 16 hours. For the combined treatment, the flour was first subjected to microwave irradiation and subsequently treated with pullulanase. After modification, all samples were stored at 4°C for 24 hours to promote starch retrogradation and then dried at 40°C for 24 hours prior to analysis. The results showed that both debranching and microwave treatments significantly increased the resistant starch content compared with untreated black rice flour. In contrast, the combined microwave–debranching treatment resulted in a reduction in resistant starch content. Among all treatments, debranching was the most effective method for improving the functional properties of black rice flour, as indicated by the increase in resistant starch content accompanied by reduced starch digestibility. Analysis of starch fractions revealed that debranching decreased the proportion of Rapidly Digestible Starch (RDS) while increasing Slowly Digestible Starch (SDS). This effect was likely associated with the formation of a more ordered crystalline structure that hindered hydrolysis by digestive enzymes. Conversely, microwave treatment increased the RDS fraction and reduced the SDS fraction, which may be attributed to an increase in the amorphous regions of starch, thereby facilitating enzymatic hydrolysis. Increased starch digestibility was also observed in the combined microwave–debranching treatment. The proximate composition, including moisture, ash, protein, and fat contents, varied among treatments. Starch modification also affected the crystalline structure of starch. Debranching maintained the A-type crystalline pattern, whereas microwave treatment and the combined microwave–debranching treatment produced a V-type crystalline pattern, suggesting the possible formation of amylose–lipid complexes. Structural changes in starch resulting from the modification treatments also influenced the pasting properties of black rice flour. All treatments reduced peak viscosity (PV), breakdown viscosity (BV), setback viscosity (SV), and final viscosity (FV). In contrast, pasting temperature increased following debranching and microwave treatments. For the combined treatment, no pasting temperature was detected, indicating extensive starch granule disruption and gelatinization, which prevented the observation of a distinct gelatinization transition during pasting profile analysis. Both debranching and microwave treatments increased amylose content while reducing amylopectin content. These changes were associated with the cleavage of amylopectin branch chains and alterations in starch granule structure during modification. In contrast, the combined treatment decreased amylose content, which may have resulted from more extensive starch structural degradation. Furthermore, all modification treatments led to a reduction in total starch content. Overall, enzymatic and physical starch modification successfully altered the physicochemical characteristics of black rice flour and enhanced its functional properties. Debranching was the most effective treatment for increasing resistant starch content and reducing starch digestibility, indicating its potential application in the development of black rice-based functional foods. In contrast, the combined microwave–debranching treatment should be carefully controlled, as excessive structural damage to starch may reduce resistant starch formation.