Rheological and Physicochemical Properties of Oleogel with Esterified Rice Flour and its Suitability as Fat Replacer

다국어 초록 (Multilingual Abstract)

The objectives of the present study were (1) to produce the emulsion and oleogel prepared by different concentrations of esterified rice flour with citric acid (ERCA), (2) to evaluate the structural, physicochemical, and rheological properties of oleogels, and (3) to investigate their potential for application in the production of cookie and cream cheese.
Rice flour was esterified with citric acid (30%, w/w) to produce ERCA. Emulsions were prepared with different concentrations of ERCA (0, 5, 10, and 15%, w/w). In the steady shear rheological analysis, it was found that the values of apparent viscosity (ηa,100) and consistency index (K) of emulsions were significantly increased with increasing the concentrations of ERCA. The frequency sweep results revealed that storage modulus (G′), loss modulus (G″), and complex viscosity (η*) of emulsions were elevated with increasing the concentrations of ERCA.
Oleogels were obtained after freeze drying of the emulsions with different concentrations of ERCA. All oleogels were observed the hydrophobic carbonyl bond in the ATR-FTIR spectra. In addition, the new hydrogen bonds and amorphous peaks, which were not appeared in oleogel prepared by 0% ERCA, were observed at 3300-3400 cm-1 and 1018 cm-1, respectively. With the increase of ERCA concentrations in oleogels, the oil loss values were significantly decreased. In the time-dependent measurement, it was found that all oleogels exhibited thixotropic properties and structure-recovery properties of oleogels were increased with increasing the concentrations of ERCA. The frequency sweep test showed that G′, G″, and η* of oleogels were elevated with the increase in the concentrations of ERCA. From temperature sweep test, it was indicated that oleogel prepared by 15% ERCA had the highest G′ and G″ values during heating (4-96ºC) and cooling (96-4ºC). For the oxidative stability during heat treatment at 140ºC for 2 h, oleogels prepared with 15% ERCA showed the lowest peroxide value, p-Anisidine value and TOTOX value. The addition of oleogels to cookie did not considerably affect the appearance, spread factor, loss rate and improved the unsaturated fatty acid contents in cookie. Oleogels can be used for the production of cream cheese to enhance the dynamic shear rheological properties (G′ and G″).
Based on the results obtained from this study, ERCA can be used in the preparation of oleogels such as an emulsifier and external coating material in order to prevent oil leakage and improve rheological properties and oxidation stability. Furthermore, it can be used as a suitable fat replacer in the food industry for producing the cookie and cream cheese.

국문 초록 (Abstract)

본 연구에서는 (1) 구연산 처리 에스테르화 멥쌀가루(esterified rice flour with citric acid, ERCA)의 농도를 달리하여 에멀젼과 올레오겔(oleogel)을 제조하고, (2) 제조된 올레오겔의 유변학적 및 이화학적 특성을 분석하고, (3) 식품(쿠키, 크림치즈)으로의 적용 가능성을 평가하였다.
멥쌀가루에 30% 구연산을 처리하여 ERCA를 제조한 후, ERCA의 농도(0, 5, 10, 15%)를 달리하여 에멀전을 제조하였다. 에멀젼의 정상유동 특성을 측정한 결과, power law 모델식을 적용하여 얻어진 점조도 지수(K)와 겉보기 점도(ηa,100) 수치는 ERCA 첨가 농도가 증가함에 따라 유의적으로 증가하였다. 소진폭 진동 시험에서도 ERCA 첨가 농도가 증가함에 따라 저장 탄성률(storage modulus, G′), 손실 탄성률(loss modulus, G″)과 복소 점도(complex viscosity, η*) 수치가 증가하였다.
에멀젼을 이용하여 제조한 올레오겔에 대하여 ATR-FTIR 스펙트럼을 분석한 결과, 모든 올레오겔에서 에스테르 결합을 의미하는 피크가 나타났으며, 에스테르화 멥쌀가루를 첨가한 올레오겔 시료에서는 수소결합과 전분의 무정형을 나타내는 새로운 피크가 확인되었다. 또한 올레오겔 내의 오일 손실률은 에스테르화 멥쌀가루의 첨가 농도에 따라 유의적으로 감소하였으며, 이는 안정적인 올레오겔이 형성되었음을 나타내었다. 올레오겔의 구조회복력을 확인하기 위해 전단 속도를 달리하여 진행한 시간 의존성 시험에서 ERCA 첨가 농도가 증가함에 따라 겉보기 점도가 증가하였고, 모든 시료에서 틱소트로픽한 거동(thixotropic behavior) 을 나타내었다. 올레오겔의 소진폭 진동 시험에서는 ERCA 첨가 농도가 증가함에 따라 올레오겔의 G′과 G″ 수치가 증가하였으며, G′ 수치가 G″ 수치보다 뚜렷하게 높아 점성적 성질에 비해 탄성적 성질이 우세한 것을 알 수 있었다. 한편, 140ºC에서 1-2 시간 가열한 올레오겔의 산화안정성을 평가했을 때, 15% ERCA 첨가 올레오겔은 다른 올레오겔 시료와 비교하여 유의적으로 낮은 과산화물가(peroxide value), 아니시딘가(p-Anisidine value) 및 TOTOX 가를 나타내었다. 올레오겔을 쿠키와 크림치즈에 적용한 결과, 올레오겔의 첨가는 쿠키의 외형, 굽기 손실률 및 퍼짐성 지수에 큰 영향을 미치지 않았으며 일반 쿠키보다 불포화 지방산 함량이 높았다. 또한, 올레오겔의 첨가는 크림치즈의 동적점탄 특성(G′ 및 G″)을 향상시킬 수 있음을 알 수 있었다.
결론적으로, ERCA는 올레오겔로부터 오일의 분리를 억제하고, 유변학적 특성과 산화 안정성을 향상시키 위한 유화제 및 코팅제로 사용되어질 수 있음을 확인하였다. 또한, 식품 산업에서 쿠키와 크림치즈 제조를 위한 지방대체제로 사용될 수 있을 것으로 기대된다.

목차 (Table of Contents)

• LITERATURE REVIEW 1
• 1. Esterified rice flour 1
• 2. Oleogel 1
• 3. Rheological property 1
• 4. Oxidative stability 2
• 1.1. INTRODUCTION 3
• 1.2. MATERIALS AND METHODS 5
• 1.2.1. Materials 5
• 1.2.2. Preparation of esterified rice flour with citric acid 5
• 1.2.3. Characterization of emulsions 6
• 1.2.3.1. Preparation of emulsions 6
• 1.2.3.2. Rheological properties of emulsions 7
• 1.2.3.2.1. Steady shear rheological properties 7
• 1.2.3.2.2. Frequency sweep 7
• 1.2.4. Preparation of oleogels 8
• 1.2.5. Characterization of oleogels 8
• 1.2.5.1. ATR-FTIR analysis 8
• 1.2.5.2. Oil loss 9
• 1.2.6. Rheological properties of oleogels 9
• 1.2.6.1. Time-dependent properties 9
• 1.2.6.2. Frequency sweep 9
• 1.2.6.3. Temperature sweep 9
• 1.2.7. Oxidative stability of oleogles 10
• 1.2.7.1. Accelerated oxidation 10
• 1.2.7.2. Peroxide value 10
• 1.2.7.3. p-Anisidine value 10
• 1.2.7.4. Total oxidation (TOTOX) value 11
• 1.2.8. Characterization of cookies with oleogels prepared by ERCA 11
• 1.2.8.1. Preparation of cookies 11
• 1.2.8.2. Dimensional characteristics of cookies 13
• 1.2.8.3. Fatty acids compositions of cookies 13
• 1.2.9. Characterization of cream cheeses in oleogels prepared by ERCA 14
• 1.2.9.1. Preparation of cream cheese 14
• 1.2.9.2. Frequency sweep 16
• 1.2.10. Statistical analysis 16
• 1.3. RESULTS AND DISCUSSION 17
• 1.3.1. Characterization of emulsions 17
• 1.3.1.1. Rheological properties of emulsions 17
• 1.3.1.1.1. Steady shear rheological properties 17
• 1.3.1.1.2. Frequency sweep 19
• 1.3.2. Characterization of oleogels 21
• 1.3.2.1. ATR-FTIR 21
• 1.3.2.2. Oil loss 24
• 1.3.3. Rheological properties of emulsions 25
• 1.3.3.1. Time-dependent properties 25
• 1.3.3.2. Frequency sweep 27
• 1.3.3.3. Temperature sweep 29
• 1.3.4. Oxidative stability of oleogels during heat treatment 32
• 1.3.5. Application of oleogels to cookies and cream cheeses 34
• 1.3.5.1. Physicochemical properties of cookies with oleogels prepared by ERCA 34
• 1.3.5.2. Rheological properties of cream cheeses with oleogels prepared by ERCA 37
• 1.4. CONCLUSION 39
• REFERENCES 40