Gel Glukomanan Porang-Xantan dan Kestabilannya Setelah Penyimpanan Dingin dan Beku

Abstract

The objectives of this research were to find the porang glucomannan-xanthan optimum ratio on composite gelation and its stability after chilled and frozen storage. Porang glucomannan sol was mixed with xanthan sol in ratio 20/40; 40/60; 50/50; 60/40 and 80/20. The composites were heated for 45 minutes at 90 °C with agitation for 5 minutes, molded, tempered, and stored at 5 °C dan -8 °C for 24 days. Before dan after storage, the texture profile, WBC and sineresis of the gel were analyzed. The composite gel microstructure was analyzed using SEM. The composite gel with ratio 20/80 had the optimum interaction synergy on gelation and stability. The GP-X intermolecular association resulted in long high density junction zones which had highest hardness, chewiness and gumminess with the smallest deformation degree and sineresis as well as medium cohesiveness. Despite of no sineresis after chilled storage, the smaller gel pores indicated that the composite gel began to contract and degrade which resulted in cohesiveness, chewinees, hardness and gumminess decrease. The WBC increase on the higher GP-X ratio composite gel made the gel to be more stable in frozen storage compared to chilled storage. However, the bigger gel pores from entrapped water volume increasing during frozen storage crystal ice formation resulted in sineresis increase. The gel became more compact with higher cohesiveness, hardness, chewiness, gumminess and deformation degree.

ABSTRAK

Penelitian ini bertujuan untuk menentukan proporsi komposit glukomanan porang dan xantan (GP-X) yang bersinergi optimal dalam pembentukan gel yang stabil setelah penyimpanan dingin dan beku. Sol glukomanan porang 1% dan sol xantan 1% dicampur dengan proporsi GP-X 20/40; 40/60; 50/50; 60/40; dan 80/20. Campuran tersebut dipanaskan pada suhu 90-95  °C selama 45 menit disertai pengadukan selama 5 menit, dicetak, didinginkan dan disimpan pada suhu dingin (5 °C) dan beku (-8 °C) selama 24 hari. Profil tekstur, water binding capacity (WBC), dan sineresis dianalisis di awal dan setelah penyimpanan. Morfologi gel komposit sebelum penyimpanan dan morfologi gel yang paling optimum setelah penyimpanan dianalisis dengan Scanning Electron Microscope (SEM). Sinergi pembentukan gel komposit GP-X paling optimal didapatkan dengan ratio 20/80. Asosiasi intermolekul GP-X pada proporsi tersebut membentuk zona hubung yang panjang dan densitas tinggi sehingga  menghasilkan hardness, chewiness, dan gumminess paling tinggi dengan derajat deformasi dan sineresis paling rendah serta daya kohesif yang sedang. Meskipun belum mengalami sineresis selama 24 hari penyimpanan dingin, pengecilan ukuran jaringan tiga dimensi (pori) gel komposit tersebut menunjukkan gel mulai kontraksi dan mengalami penurunan mutu dengan indikasi penurunan daya kohesif, chewiness, hardness, dan gumminess. Peningkatan WBC pada proporsi yang lebih tinggi menyebabkan gel nampak lebih stabil pada penyimpanan beku dibandingkan dengan penyimpanan dingin. Pembesaran pori gel akibat pengembangan volume air yang terperangkap selama pembentukan kristal es menyebabkan peningkatan sineresis, pemadatan gel, dan peningkatan hardness, chewiness, gumminess, dan persentase deformasi.