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Effects of Organic Acids on Properties of Soy Milk-Juice Beverage Models

유기산이 두유-쥬스 혼합 음료 모델의 특성에 미치는 영향

  • 피라퐁 냠니콤 (Peerapong Ngamnikom, Gangneung-Wonju National University, Graduate School, Department of Applied Marine Biotechnology and Engineering)

초록/요약 도움말

요즘 영양가가 풍부한 음식의 필요성과 수요가 커지면서 두유 주스 음료는 특히 서양중심으로 소비가 증가하고 있습니다. 두유 주스 음료는 고단백, 미네랄, 비타민 및 콜레스테롤이 적은 이소플라본을 함유하고 있습니다. 주스의 맛과 풍미는 두유 특유의 콩 비린내를 차단하여 거부감을 줄여줄 수 있습니다. 두유 주스 음료 시스템의 불안정성은 산성인 주스와 대두 단백질 간의 상호 작용으로 인하여 침전물을 발생시킵니다. 펙틴과 같은 다당류의 첨가로 인한 시스템의 불안정성을 개선하기 위한 연구가 널리 이루어지고 있습니다. 산이 대두 반백질과 결합하여 생기는 시스템의 불안정성은 잘 알려져 있습니다. 그래서, 많은 종류의 산들이 시스템 안에서 어떤 영향을 미칠지에 대한 연구는 흥미롭습니다. 여러 종류의 산들이 얼마나 에멀젼 형성 및 안정성과 관계되는 시스템 전체와 계면 특성을 포함한 대두 단백질의 특성에 영향을 미치는지에 대한 정확한 연구는 없었습니다. 첫번째 연구는 보편적인 실험들에 사용되는 대표적 산인 염산뿐만 아니라 식용 유기산인 아세틱, 아스콜빅, 락틱, 말릭, 시트릭, 그리고 타르타릭 산이 분리 대두 단백질 (SPI), 1.5% (w/v), pH 3.0)의 서스펜젼, 오일과 물의 계면, 오일이 들어 있는 물 에멀젼들의 특성에 미치는 영향에 대한 것입니다. 에멀젼 모델은 상업용 두유 주스 음료에 지방 농도에 따른 대두 오일 (1% (v/v))을 첨가하여 만들었습니다. 산의 종류는 산의 세기 순서 (낮음부터 높은 산의 세기 : 아세틱, 아스콜빅, 락틱, 말릭, 시트릭, 타르타릭, 그리고 염산)에 따른 강도의 추세와 SPI의 특성들에 미미하게 영향을 주었습니다. 약산 그룹 (아세틱과 아스콜빅산)으로 만든 서스펜젼 보다 강산 그룹 (락틱, 말릭, 시트릭, 타르타릭, 그리고 염삼산) 으로 만든 서스펜젼의 계면은 더 높은 계면장력 (γ)과 계면복합체 전단 변형률 (G*)을 가지고 있습니다. 에멀젼 특성에 대한 산의 영향 또한 미미하였습니다. 4, 25, 그리고 60도에서 28일동안의 저장기간 동안, 아스콜빅 산을 함유하고 있는 에멀젼을 제외하고는 탁도에 별 차이가 없는 반면, 60도를 제외하고 모든 온도 대에서 약간 에멀젼 입자 사이즈 차이를 확인하였습니다. 두번째 연구는, 다른 산 종류 (아세틱, 시트릭, 그리고 염산 ; 첫번째 연구에서 밝혀진 계면특성에 기초하여 선택된 산들) 들이 수상 상태에서 고 메톡시 펙틴 (HMP)이 첨가된 SPI의 서스펜젼, 오일과 물의 계면, 오일이 들어 있는 물 에멀젼 특성들에 미치는 영향입니다. SPI와HMP의 2 : 1 비율과 이것의 총 바이오폴리머의 농도는 2.25% (w/v) 입니다. 이 연구는 보통 단백질 침전을 감소시키기 위해 상업용 두유 주스 음료에 첨가되는 HMP가 첨가된 SPI-HMP 혼합물에 산 종류들이 미치는 영향을 알아보기 위한 것이다. 펼쳐진 대두 단백질 (양전하)와 특별하게 결합된 HMP (음전하) 때문에, pH 3.0에서 HMP영향에 의해 산 종류들의 영향이 두드러졌다. HMP의 존재는 계면층의 강도를 증가시켰으나 저장 온도와 상관없이 에멀젼의 안정성은 감소시켰습니다. 세번째 연구는, 다른 산 종류들 (아세틱, 시트릭, 그리고 염산 ; 첫번째 연구에서 밝혀진 계면특성에 기초하여 선택된 산들)이 레시틴 (대두유 상과 혼합, 총 3% (w/v))이 첨가된 SPI의 오일과 물 계면, 오일이 들어 있는 물 에멀젼의 특성들에 미치는 영향입니다. 자연에서 레시틴은 보통 대두에 존재하므로 대두 오일 상에 첨가 되었습니다. 이 연구는 SPI가 계면에서 레시틴과 상호작용하였을 때 산 종류들이 SPI에 미치는 영향을 알아보기 위해 연구되었다. 산 종류들은 특히 계면 특성인 G*에 큰 영향을 끼쳤으며, G*값의 순서들은 산들에 의해 변화하였다. 레시틴이 첨가된 샘플들의 계면 특성들 (레시틴이 첨가되지 않은 샘플들 보다 더 낮은 γ 과 더 높은 G* 을 나타냄)은 개선되었습니다. 그러나, 레시틴 첨가와 무 첨가 샘플들의 에멀젼 특성 차이는 (형성과 안정성) 에멀젼에 존재하는 오일의 양이 적었기 때문에 크지 않은 것 같습니다. 위의 결과들로 유추하였을 때, 산 종류들은 각각 다르게 SPI 형태 변화를 유도하여 약간의 SPI특성 차이를 발생시키는 것으로 추론할 수 있다. 산으로부터 이온화된 음이온들은 양으로 대전된 대두 단백질과 결합을 할 수 있는데, 결합 친화도는 해당 pH에서 음이온 전하량과 관련이 있습니다. 수성 시스템이 HMP같은 다른 음으로 대전된 고분자를 함유할 때, 음이온이 대두 단백질에 미치는 영향은 두드러집니다. 수성 (SPI)와 유상 (레시틴)에 각각 함유되어 있는 두 다른 분자 사이의 상호작용은 계면 특성을 개선시킬 수 있습니다.

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초록/요약 도움말

Soy milk-juice beverage has increased in consumption especially in western country, because people need to consume rich of nutritional food in nowadays. This product contains high proteins, minerals, vitamins and isoflavones with low cholesterols. The taste and flavor of juice can block beany flavor in soy milk and improve acceptance of westerners. The system instability can be occurred from the interaction between acid juices and soy proteins then precipitation happens. There are widely study of improving system instability by addition of polysaccharide such as pectins. As it was well known about the cause of system instability which is acids interact soy proteins. So it can be seen the point which it is interesting to note that many acid types exist in the system. It has been no literature exactly reports how different acids influence soy protein properties, including bulk and interfacial properties, and these relate with emulsion formation and stability. The first study was the effects of different food organic acids, including acetic, ascorbic, lactic, malic, citric, and tartaric acids, as well as hydrochloric acid (HCl) for reference acid in general experiments, on the suspension properties, oil-water interfacial properties, and oil-in-water emulsion properties of soy protein isolate (SPI) at 1.5% (w/v) at pH 3.0. Soybean oil 1% (v/v) was added to making emulsion model, according to the fat concentration in commercial soy milk-juice beverage. The acid types marginally influenced the properties of SPI and the trend of magnitude quite followed order of acid strength (acid strength from low to high; acetic, ascorbic, lactic, malic, citric, tartaric, and HCl). Interfacial properties of acidified suspension with the group of stronger acid strength (lactic, malic, citric, tartaric, and (HCl) had higher interfacial tension (γ) and interfacial complex shear modulus (G*) than the group of weaker acid strength (acetic and ascorbic). The emulsion properties were also marginally influenced by acid types. The storage emulsion stability at 4, 25, and 60 oC for 28 days showed a few different emulsion particle size excluding the storage at 60 oC, while they were not much change in turbidity excluding emulsion contained ascorbic acid. The second study was the effects of different acid types (acetic, citric, and HCl; selected acid types based on interfacial properties from the first study) on the suspension properties, oil-water interfacial properties, and oil-in-water emulsion properties of SPI with the addition of high methoxy pectin (HMP) in the aqueous phase of SPI. The ratio of SPI : HMP was 2 : 1 and its total biopolymer concentration was 2.25% (w/v). This study wanted to know the effect of acid types on SPI-HMP mixture by which HMP is normally added in the commercial soy milk-juice beverage in order to decrease protein precipitation. The effect of acid types was dominated by the effect of HMP at the pH 3.0 due to binding of HMP (negative charge) on partially unfolded soy proteins (positive charge). The existing of HMP increased the strength of interfacial layer but decreased the emulsion stability, regardless of storage temperature. The third study was the effects of different acid types (acetic, citric, and HCl; selected acid types based on interfacial properties from the first study) on the oil-water interfacial properties and oil-in-water emulsion properties of SPI with the addition of lecithin (soy lecithin) 3% (w/v) in the soybean oil phase. The lecithin was decided to add in the oil phase because it normally exists in the soybean oil in the nature. This study wanted to know the effect of acid types on SPI when the SPI interacted with lecithin at the interface. The acid types were large significance on interfacial properties especially G*, which the order of G* dependent on acids was changed. The lecithin-added samples showed the improvement of the interfacial properties which they showed lower γ and higher G* than non-lecithin-added samples. However the emulsion properties including formation and stability were not much different between lecithin-added and non-lecithin-added samples, which it could be the small amount of oil existing in emulsions. These results could infer an information which acid types differently induced change of SPI conformation, hence the SPI properties could be some difference. The anions, which ionized from acids, could bind positively charged soy proteins. The binding affinity related with amount of anion charge at concerned pH. When the aqueous system contained another negatively charge macromolecules, such HMP, it could dominate the effects of anions on soy protein. The interaction between two different molecules, which they separately contained in aqueous (SPI) and oil phases (lecithin), could improve interfacial properties at oil-water interface.

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목차 도움말

Table of contents I
List of Tables VII
List of Figures IX
Acknowledgements XII
Abstract XIII
Chapter 1. Literature review 1
1. Introduction to soybean, soy milk and soy milk-juice beverage 1
2. Composition of soybean, soy milk, and soy milk-juice beverage 3
3. Study of soy milk-juice beverage 8
4. Structure of soy milk 17
5. Structure of acidified soy milk 18
6. Soybean protein 19
6.1 Soy protein isolate (SPI) 19
6.2 Glycinin 20
6.3 β-conglycinin 21
6.4 Comparison of characteristics 23
7. Dissociation of SPI at acidic pH 24
8. Unfolding of SPI at acidic pH 25
9. Acid-induced unfolding of globular protein and anion-induced refolding
of unfolded globular protein 26
10. Interfacial tension 29
11. Interfacial rheology 30
12. Protein adsorption at interface 31
13. Adsorption of SPI at oil-water interface 33
14. Organic acids 35
15. Previous study of the effect of acid types on properties of protein in
foods 36
16. Natural pectins 37
17 Commercial pectins 39
17.1 Chemical structure of commercial pectins 40
17.2 Solubility and viscosity properties of commercial pectins 41
17.3 Application of commercial pectins in foods 42
17.4 Application of commercial pectins in acidified soy milk 43
17.5 Soy protein-HMP interaction in bulk phase 43
17.6 Soy protein-HMP interaction at interfaces 46
18. Soy lecithin 47
18.1 Chemical structure of soy lecithin 48
18.2 Properties of soy lecithin 50
18.3 Soy protein-soy lecithin interaction in bulk phases 50
18.4 Soy protein-soy lecithin interaction at interfaces 50
19. Research significance 51
20. Research objectives 53
Chapter 2. Effects of organic acids on oil-water interfacial and aqueous suspension properties of SPI, and on the emulsion properties of soy milk-juice beverage model 55
Abstract 55
1. Introduction 57
2. Materials and methods 62
2.1 Materials 62
2.2 SPI suspension preparation 63
2.3 SPI emulsion preparation 63
2.4 Particle size measurement 63
2.5 Zeta potential measurement 64
2.6 Flow curve measurement 65
2.7 Diffusion coefficient measurement 66
2.8 Interfacial tension measurement 67
2.9 Interfacial shear viscoelastic measurement 69
2.10 Emulsion stability 72
2.11 Statistical analysis 73
3. Results and discussion 74
3.1 SPI suspension preparation 74
3.2 Effects of acids on SPI suspensions 76
3.3 Effects of acids on interfacial properties 85
3.4 Effects of acids on SPI emulsions 95
4. Conclusions 107
Chapter 3. Effects of organic acids on oil-water interfacial and aqueous suspension properties of SPI in the presence of HMP, and on the emulsion properties of HMP-added soy milk-juice beverage model 109
Abstract 109
1. Introduction 110
2. Materials and methods 112
2.1 Materials 112
2.2 SPI and SPI-HMP suspension preparation 113
2.3 SPI and SPI-HMP emulsion preparation 113
2.4 Particle size measurement 114
2.5 Zeta potential measurement 114
2.6 Flow curve measurement 114
2.7 Diffusion coefficient measurement 114
2.8 Interfacial tension measurement 114
2.9 Interfacial shear viscoelastic measurement 114
2.10 Emulsion stability 114
2.11 Statistical analysis 114
3. Results and discussion 115
3.1 Selection of acid types from study in Chapter 2 115
3.2 Effects of acids on SPI and SPI-HMP suspensions 115
3.3 Effects of acids on interfacial properties 126
3.4 Effects of acids on SPI and SPI-HMP emulsions 134
4. Conclusions 142
Chapter 4. Effects of organic acids on oil-water interfacial properties of SPI in the presence of soy lecithin in oil phase, and on the emulsion properties of soy lecithin-added soy milk-juice beverage model 144
Abstract 144
1. Introduction 145
2. Materials and methods 147
2.1 Materials 147
2.2 SPI suspension and LEC in soybean oil preparation 147
2.3 SPI and LEC-SPI emulsion preparation 148
2.4 Interfacial tension measurement 148
2.5 Interfacial shear viscoelastic measurement 148
2.6 Particle size measurement of emulsions 148
2.7 Zeta potential measurement of emulsions 148
2.8 Flow curve measurement of emulsions 148
2.9 Emulsion stability 148
2.10 Statistical analysis 148
3. Results and discussion 149
3.1 Selection of acid types from study in Chapter 2 149
3.2 Effects of acids on interfacial properties 149
3.3 Effects of acids on SPI and LEC-SPI emulsions 160
4. Conclusions 169
Chapter 5. Summary 171
Chapter 6. References 173

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