Structural and textural properties of low methoxyl pectin-based cryogel produced with modified guar gum

국문 초록 (Abstract)

구조 변형 구아검으로 제조한 저메톡실펙틴 기반 크라이오겔의
구조적 및 조직감 특성 평가

본 연구에서는 (1) 구조변형 구아검(modified guar gum, MGG)의 물 분산성과 분자량 분포, (2) MGG의 농도를 달리하여 제조한 저메톡실 펙틴(low mehoxyl pectin, LMP) 겔의 유변학적 특성, 그리고 (3) MGG의 농도를 달리하여 제조한 LMP 기반 크라이오겔의 구조적 및 조직감 특성을 평가하였다. 분자량 분포 측정 결과 구연산 및 고온 가열 처리는 구아검의 분자량을 감소시키고, 물 분산성을 향상시킬 수 있음을 알 수 있었다. LMP 겔의 소진폭 진동 시험 결과, MGG의 첨가 농도가 증가함에 따라 저장 탄성률 (storage modulus, G′), 손실 탄성률(loss modulus, G″)과 복소점도(complex viscosity, η*) 수치가 현저히 증가함을 확인하였다. 4℃ 저장 중 MGG(0.5-1.5%)를 첨가한 LMP 겔의 G′과 G″의 변화를 측정한 결과, MGG의 첨가는 새로운 망상구조를 형성하여 LMP 겔의 G′과 G″ 수치를 향상시킬 수 있음을 알 수 있었다. 가열 및 냉각 동안, LMP 겔의 G′과 G″ 수치는 MGG가 첨가에 따라 증가하였다. LMP 기반 크라이오겔의 구조적 특성을 평가한 결과, LMP 기반 크라이오겔 제조 시 MGG의 첨가는 크라이오겔 내 기공 사이의 빈 공간을 채워줄 수 있으며, 결과적으로 다공성의 감소와 더욱 조밀하고 견고한 구조의 형성을 야기하였다. 또한, 조직감 특성 평가 결과를 통하여 MGG의 첨가는 LMP 기반 크라이오겔의 조직감 특성을 향상시킬 수 있음을 확인하였다. 결과적으로 펙틴 기반 크라이오겔 제조 시 MGG를 첨가하게 되면 더욱 견고하고 조밀한 망상구조가 형성되고, 크라이오겔 내 다공성이 감소하여 향상된 조직감 특성을 가질 수 있었다.

다국어 초록 (Multilingual Abstract)

The objectives of the present study were (1) to elucidate the water dispersibility and molecular weight of modified guar gum (MGG), (2) to evaluate the dynamic shear rheological properties of low methoxyl pectin (LMP) gels with different concentrations of MGG, and (3) to investigate the structural and textural properties of LMP-based cryogels produced with different concentrations of MGG.
High performance size exclusion chromatography demonstrated that citric acid treatment with high temperature decreased the molecular weight distribution of the native guar gum. Water dispersibility of the gum was remarkably improved after the modification with citric acid at high temperature. The results suggested that the modification of guar gum could lead to some changes in the structure and functional groups, such as the destruction of the cell-wall structures and unfolding of the polysaccharide molecules; subsequently, resulting in the exposure of hydrophilic groups from inside and the enhancement of the water dispersibility.
According to the results of frequency sweep test, the dynamic moduli (G′ and G″) for LMP gels were remarkably increased with increasing the frequency and concentrations. The changes in dynamic moduli of LMP gels added with MGG (0.5~1.5%) as a function of aging time at 4 °C demonstrated that the addition of MGG to LMP gels can form a more rigid network. Based on the findings of temperature sweep test (heating and cooling), the dynamic moduli of LMP gels added with MGG were much higher than those of only LMP gels.
The addition of MGG to LMP-based cryogels decreased the sample porosity as the pores were filled with MGG, and consequently the structure of the cryogels with MGG became more ordered and packed. In the texture profile analysis, it was found that the addition of MGG can improve the hardness, fratruallity, springiness, gumminess and chewiness values of LMP-based cryogels, which was related to the packed network and less porosity of the cryogels.

목차 (Table of Contents)

• LITERATURE REVIEW 1
• 1.1. Cryogels 1
• 1.2. Low methoxyl pectin 2
• 1.3. Guar gum 2
• 2.1. Introduction 4
• 2.2. Materials and Methods 6
• 2.2.1. Materials 6
• 2.2.2. Preparation of modified guar gum (MGG) 6
• 2.2.2.1. Water dispersibility of modified guar gum (MGG) 8
• 2.2.2.2. Molecular weight distribution of modified guar gum (MGG) 8
• 2.2.3. Dynamic shear rheological properties of LMP-MGG gels 9
• 2.2.3.1. Preparation of stock solutions 9
• 2.2.3.2. Preparation of LMP-MGG gels 9
• 2.2.3.3. Frequency sweep test 9
• 2.2.3.4. Time sweep test 10
• 2.2.3.5. Temperature sweep test 10
• 2.2.4. Preparation of cryogels 11
• 2.2.4.1. Preparation of stock solutions 11
• 2.2.4.2. Preparation of LMP-based cryogels with MGG 11
• 2.2.5. Characterization of LMP-based cryogels with MGG 12
• 2.2.5.1. Scanning electron microscope (SEM) 12
• 2.2.5.2. High resolution 3D X-ray tomography microscope (XRM) system 12
• 2.2.5.3. Texture profile analysis (TPA) 12
• 2.2.6. Statistical analysis 13
• 2.3. Results and Discussions 14
• 2.3.1. Water dispersibility of modified guar gum (MGG) 14
• 2.3.2. Molecular weight distribution of modified guar gum (MGG) 15
• 2.3.3. Dynamic shear rheological properties of LMP-MGG gels 17
• 2.3.3.1. Frequency sweep test 17
• 2.3.3.2. Time sweep test 21
• 2.3.3.3. Temperature sweep test 23
• 2.3.4. Appearance analysis of LMP-based cryogels with MGG 26
• 2.3.5. Characterization of cryogels 27
• 2.2.5.1. Scanning electron microscope (SEM) 27
• 2.2.5.2. High resolution 3D X-ray tomography microscope (XRM) system 29
• 2.2.5.3. Texture profile analysis (TPA) 32
• 2.4. Conclusion 34
• REFERENCES 35