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Công nghệ thực phẩm - Chất keo thực phẩm

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  1. 8/1/2016 CHẤT KEO THỰC PHẨM (Food hydrocolloids) Giảng viên: Mạc Xuân Hòa 1 NỘI DUNG 1. Giới thiệu chung về chất keo 2. Một số chất keo sử dụng làm phụ gia TP 3. Modification 2 1
  2. 8/1/2016 NỘI DUNG 1. Giới thiệu chung về chất keo 2. Một số chất keo sử dụng làm phụ gia TP 3. Modification 3 Hydrocolloids . Hydrocolloids are a heterogeneous group of long chain polymers (polysaccharides and proteins) characterised by their property of forming viscous dispersions and/or gels when dispersed in water. . The foremost reason behind the ample use of hydrocolloids in foods is their ability to modify the rheology of food system. This includes two basic properties of food system namely, flow behaviour (viscosity) and mechanical solid property (texture) to modify its sensory properties. 4 2
  3. 8/1/2016 Kích thước cấu tử hòa tan Dung dịch 1 pha Dung dịch keo Huyền phù (<10-6 mm ) (10-4 - 10-6 mm ) (1 - 10-2 mm ) pH Đông Nhiệt độ tụ Lực ion, 5 Nguồn gốc 6 3
  4. 8/1/2016 Functional properties • Thickening (basic) • Gelling (basic) • Emulsifying • Controlling the crystal growth of ice and sugar • . 7 NỘI DUNG 1. Giới thiệu chung về chất keo 2. Một số chất keo sử dụng làm phụ gia TP . Thickening agent/Thickener . Gelling agent 8 4
  5. 8/1/2016 NỘI DUNG 1. Giới thiệu chung về chất keo 2. Một số chất keo sử dụng làm phụ gia TP . Thickening agent/Thickener . Gelling agent 9 Thickening agents . A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties. 10 5
  6. 8/1/2016 Examples of food products containing hydrocolloids Soups Salad dressings Gravies Sauces Toppings 11 Process of thickening In dilute dispersion, the individual molecules of hydrocolloids can move freely and do not exhibit thickening. In concentrated system, these molecules begin to come into contact with one another; thus, the movement of molecules becomes restricted. The transition from free moving molecules to an entangled network is the process of thickening. 12 6
  7. 8/1/2016 Factors effecting thickening properties . Molecular weight . Concentration . Shear rate . Temperature, 13 Mark-Houwink equation . M: the molecular weight . K, α: the parameters of Mark-Houwink equation 14 7
  8. 8/1/2016 15 The critical overlap concentration C* . The polysaccharide concentration at which the sharp change in viscosity occurs is referred to as the critical overlap concentration and is denoted by C*. . Polysaccharide dispersions below C* will typically exhibit near Newtonian steady shear flow and the increase in the viscosity of the dispersion is roughly proportional to the number of molecules present. Above C* entanglement dispersion networks will exhibit shear thinning meaning that apparent viscosity decreases with increasing shear rate. 16 8
  9. 8/1/2016 Shear thining Khi C>C* độ nhớt (viscosity) và tốc độ cắt (shear rate) có quan hệ như dạng đường cong ở trên. 17 At low shear rates, solutions of xanthan gum have approximately 15 times the viscosity of guar gum and significantly more viscosity than carboxymethylcellulose (CMC) or sodium alginate which accounts for its superior performance in stabilising18 suspensions. 9
  10. 8/1/2016 Amylose will have a higher intrinsic viscosity than amylopectin. 19 20 10
  11. 8/1/2016 21 Regulations 22 11
  12. 8/1/2016 Xanthan Gum (E415) 23 XANTHAN GUM  Nguồn gốc  Cấu tạo hóa học  Tính chất  Ứng dụng 24 12
  13. 8/1/2016 XANTHAN GUM  Nguồn gốc  Cấu tạo hóa học  Tính chất  Ứng dụng 25 XANTHAN GUM Nguồn gốc  An extracellular polysaccharide secreted by the bacterium Xanthomonas campestris.  Xanthan gum is produced from a pure culture of the bacterium by an aerobic, submerged fermentation process. 26 13
  14. 8/1/2016 XANTHAN GUM  Nguồn gốc  Cấu tạo hóa học  Tính chất  Ứng dụng 27 XANTHAN GUM Cấu tạo hóa học Xanthan gum is a linear (1 4) linked β – D - glucose backbone (as in cellulose) with a trisaccharide side chain on every other glucose at C-3, containing a glucuronic acid residue linked (14) to a terminal mannose unit and (12) to a second mannose that connects to the backbone. 28 14
  15. 8/1/2016 XANTHAN GUM  Nguồn gốc  Cấu tạo hóa học  Tính chất  Ứng dụng 29 XANTHAN GUM Tính chất Xanthan gum is widely used as a rheology control agent for aqueous systems: Increasing viscosity (thickening)  Stabilizing emulsions  Preventing the settling of solids 30 15
  16. 8/1/2016 XANTHAN GUM Tính chất  The viscosity and yield value of compositions containing the gum will not change significantly between ambient temperature and 60°C.  Xanthan gum provides the same thickening, stabilizing and suspending properties during long-term storage at elevated temperature as it does at ambient conditions.  It imparts excellent freeze/thaw stability to most compositions. 31 XANTHAN GUM Tính chất Complex aggregates, with weak intermolecular forces High viscosity at low shear rates (suspension stabilising properties) 32 16
  17. 8/1/2016 XANTHAN GUM Tính chất At low shear rates, solutions of xanthan gum have approximately 15 times the viscosity of guar gum and significantly more viscosity than carboxymethylcellulose (CMC) or sodium alginate which accounts for its superior performance in stabilising33 suspensions. XANTHAN GUM Tính chất 34 17
  18. 8/1/2016 XANTHAN GUM Tính chất The viscosity remains nearly constant between pH 2 and pH 12 35 XANTHAN GUM Tính chất Synergistic Effect Xanthan gum có có hiệu ứng “hiệp đồng” với các chất keo sau: . Guar gum . Locust bean gum . Cassia gum . Konjac mannan Tăng khả năng làm dày 36 18
  19. 8/1/2016 XANTHAN GUM  Nguồn gốc  Cấu tạo hóa học  Tính chất  Ứng dụng 37 XANTHAN GUM Ứng dụng 38 19
  20. 8/1/2016 Introduction • Stabilizer gums are used to improve the texture, increase the firmness and prevent syneresis in yogurt. This is important to help maintain good textural and visual properties during transportation and storage. 39 Introduction Xanthan is used widely in the food industry because it has: . Solubility in hot or cold water, . High viscosity at low concentrations, . Little variation in viscosity with changing temperature, . Excellent solubility and stability in an acid system, . Unique rheological properties that provide high viscosity under low shear and low viscosity under high shear, . Excellent compatibility with a wide range of salts, 40 20
  21. 8/1/2016 Objectives • To determine the influence of laboratory- produced xanthan gum either singly or in combination with other gums on the rheological properties of yogurt and soy yogurt during refrigerated storage. 41 Method: Preparation of yogurt Treat ment I Treat ment II 0.005% All treatments were heated to 90 °C for 10 min and Cow's Treat ment III rapidly cooled to 42 °C, inoculated with 2% yogurt milk Treat ment I starter, and were then distributed into 120 ml plastic Treat ment II 0.01% cups and incubated at 42 °C until a uniform Treat ment III coagulum was reached (3 - 5h depending on the Treat ment I type of milk). The yogurt and soy yogurt cups were Treat ment II 0.005% then transferred to refrigerated storage and Soy Treat ment III analyzed after 1, 5 and 10 days of storage for their milk Treat ment I chemical, microbiological, rheological, Treat ment II 0.007% microstructural and sensory properties. Treat ment III Treat ment I: Xanthan gum Treatment II: Xanthan gum + CMC Treatment III: Xanthan gum + locust bean gum + guar gum 42 21
  22. 8/1/2016 Method: Rheological properties • Viscosity: 43 Method: Rheological properties • Curd tension: 44 22
  23. 8/1/2016 Method: Rheological properties • Syneresis: Syneresis of yogurt and soy yogurt was determined by measuring the volume of separated whey (milliliters whey/50 g yogurt). The amount of free whey collected after 30 min at room temperature (25±1 °C) was taken as the index of syneresis. 45 Results: Viscosity of yogurt and soy yogurt during fermentation . The viscosity values of cows’ milk yogurt or soy milk yogurt during the fermentation period were affected by the type and concentration of stabilizer used. . These values increased markedly using gum either singly or in combination with other gums. 46 23
  24. 8/1/2016 Results: Viscosity of yogurt and soy yogurt during fermentation 47 Results: Curd tension • The use of xanthan gum or its mixtures at mentioned concentration rates markedly increased the curd tension of yogurt as compared to the control when fresh and during storage. This increase may be attributed to the interaction between the gum and the milk portion. • Yogurt: treatment (I) with xanthan gum at a concentration of 0.01% exhibited the highest curd tension. • Soy yogurt: the addition of xanthan gum at a concentration of 0.005% (Treatment I) resulted in the highest curd tension of soy yogurt 48 24
  25. 8/1/2016 Results: Syneresis • No syneresis was found with xanthan gum at a concentration of 0.005% when fresh or during storage (in both yogurt and soy yogurt). 50 25
  26. 8/1/2016 NỘI DUNG 1. Giới thiệu chung về chất keo 2. Một số chất keo sử dụng làm phụ gia TP . Thickening agent/Thickener . Gelling agent 52 26
  27. 8/1/2016 Gels are . A three-dimensional network that traps or immobilizes water within it to form a rigid structure 53 Gels are . A form of matter intermediate between solid and liquid and show mechanical rigidity. . A viscoelastic system with a ‘storage modulus’ (G′) larger than the ‘loss modulus’ (G″). 54 27
  28. 8/1/2016 Rheology of gels Fluid-like Solid-like What is  ? Phase angle 55 Deformation tests: Oscillatory rheometer 56 28
  29. 8/1/2016 57 .  = 0 tan = 0: G” = 0 Solid .  = /2 tan = : G’ = 0 Fluid . 0 G’’ We can measure G’ and G’’ by using a Oscillatory rheometer 58 29
  30. 8/1/2016 Silly putty 59 60 30
  31. 8/1/2016 Which one is stronger ? 61 Which one is stronger ? 62 31
  32. 8/1/2016 Process of gelling • The formation of gel is the phenomenon involving the association of the polymer chains to form a three-dimensional network that traps or immobilizes water within it to form a rigid structure. 63 Process of gelling: physical association . Hydrogen bonding Junction . Hydrophobic association zones . Cation mediated cross-linking 64 32
  33. 8/1/2016 Process of gelling: ‘junction zones’ 65 CONDITIONS OF GEL FORMATION • Type of hydrocolloids • Concentration of Gelling Agent • Conditions at which “junction zones” can be formed: temperature, ionic strength, high pressure, 66 33
  34. 8/1/2016 Type and Concentration of hydrocolloids • Not all hydrocolloids can form gel. Gel formation only occurs above a critical minimum concentration, C∗. 67 Conditions at which “junction zones” can be formed: . Temperature (low or high): agar, gelatin, . Ionic strength: alginate, LM pectin, or carrageenan, . pH: HM pectin . High pressure 68 34
  35. 8/1/2016 Conditions at which “junction zones” can be formed: . Temperature: agar, gelatin, . Ionic strength: alginate, pectin, or carrageenan, . pH . Pressure 69 Một số loại chất keo tạo gel khi làm lạnh (agar, gelatin, pectin, tinh bột, ) 70 35
  36. 8/1/2016 Thermoreversible gels: agar, gelatin, 71 GELATIN Cooling Sol Heating (35–40ºC): ‘melt in the mouth’ 72 36
  37. 8/1/2016 AGAR Gelling temperature: around 380C Melting temperature: around 850C Gelling concentration: between 0,5 – 2% 73 Conditions at which “junction zones” can be formed: . Temperature: agar, gelatin, . Ionic strength: alginate, pectin, or carrageenan, . pH . Pressure 74 37
  38. 8/1/2016 Low Methoxyl Pectin Ca2+ DUNG DỊCH GEL 75 Alginate gel formation 76 38
  39. 8/1/2016 Conditions at which “junction zones” can be formed: . Temperature: agar, gelatin, . Ionic strength: alginate, pectin, or carrageenan, . pH . Pressure 77 High Methoxyl Pectin 65% chất khô DUNG DỊCH GEL H+ (hydrogen bonds) [Pectin] = 0,5-1% . Đường có khả năng hút ẩm giảm mức độ hydrat hóa của phân tử pectin trong dung dịch; . H+ trung hòa bớt các gốc COO- làm giảm độ tích điện của các phân tử; 78 39
  40. 8/1/2016 Making Jam Cooling 79 Conditions at which “junction zones” can be formed: . Temperature: agar, gelatin, . Ionic strength: alginate, pectin, or carrageenan, . pH . High pressure (a single process or in combination with increased temperature): usually applied to form protein gels 80 40
  41. 8/1/2016 81 Keywords . Rapeseed . Protein isolate Bodybuilder 82 41
  42. 8/1/2016 Introduction • Heat and high pressure can improve gelation propertie of food protein: increased exposure of hydrophobic and sulfhydryl (SH) groups (structure modification). 83 Introduction • The effect of high pressure-induced modification depends on the protein system, the treatment temperature, the protein solution conditions, and the magnitude and duration of the applied pressure. 84 42
  43. 8/1/2016 Introduction • The objectives of this study are to determine the effects of high temperature or HP processing on protein gelation with relationships to free sulfhydryl content, surface hydrophobicity, 85 Method: HP and Heat Processing . 1 % (w/v) RPI slurry was prepared in 50mMTris– HCl buffer (pH 7.5) with stirring at 4 °C for 12 h. . For HP treatment, the RPI slurrywas sealed in a polyethylene bag and then subjected to a 4-l HP reactor unit equipped with temperature and pressure regulation as transmitting medium of water, followed by freeze-drying and storage at −20 °C until needed for further analysis. 86 43
  44. 8/1/2016 Method: Design of experiment • Trial 1: HP was operated at 200, 400, and 600 MPa for 15 min each while the temperature was kept at 25 °C. • Trial 2: the RPI slurry was heated in a water bath at 60, 80, and 100 °C for 15 min. 87 Method: Determination of responses . Free Sulfhydryl Content (M/g protein) . Surface Hydrophobicity (So) . Gelation properties: least gelation concentration (LGC), Hardness (N), . 88 44
  45. 8/1/2016 Results: Free Sulfhydryl Content (M/g protein) 200 MPa: a significant (p<0.05) increase, which probably reflects pressureinduced exposure of inaccessible thiol groups buried within the hydrophobic interior. 400 – 600 MPa: a progressive decrease in free SH groups, which may be due to formation of disulfide bonds as pressure-induced protein– protein interactions intensified. Heat had stronger effects on Free Sulfhydryl Content when compared to HP treatments 89 Results: Surface Hydrophobicity (So) So of RPI was significantly (p<0.05) increased following HP and thermal treatments, which suggests that the native protein had a higher degree of globular (folded) structure when compared to the treated samples. The higher protein unfolding efficiency of HP treatment may be due to the effective ability to disrupt hydrogen bonds that hold proteins in a folded state. HP had a stronger effect on Surface Hydrophobicity (So) when compared to Heat. 90 45
  46. 8/1/2016 Results: Gelation properties LGC of RPI was significantly (p<0.05) decreased from 15 to 6 % by HP treatment, while heat treatment decreased LGC from 15 to 10 %. The unfolded proteins are then able to interact through hydrophobic bonding to increase strength of resultant gel networks and reduce amount of proteins required to form the gel, i.e., decreased LGC. 91 Conclusions • Overall, pressure treatments (200–600 MPa) were better than heat treatments (60–100 °C) to modify the structure and improve gelation properties of RPI. 92 46
  47. 8/1/2016 93 94 47
  48. 8/1/2016 95 Jam Jelly Confectionery 96 48
  49. 8/1/2016 97 98 49
  50. 8/1/2016 Other Applications . Surface activity and emulsifying properties . Hydrocolloids as edible films and coatings . Hydrocolloids as fat replacers 99 100 50
  51. 8/1/2016 NỘI DUNG 1. Giới thiệu chung về chất keo 2. Một số chất keo sử dụng làm phụ gia TP 3. Modification 101 Why do we modify food hydrocolloids ? • Some native hydrocolloids have often been reported to present a number of undesired properties, including is insolubility in cold water, crumbling after heating, and loss of viscosity, 102 51
  52. 8/1/2016 Starch 103 TINH BỘT Cấu tạo hóa học Hydrogen bonds 104 52
  53. 8/1/2016 STARCH Rheological properties Reassociation of Amylose Heating Cooling 105 Three categories of digestible starches are distinguished by the rate at which glucose is formed and absorbed in the blood . Rapidly digestible starches (RDS) are hydrolysed in the small intestine within the first 20 min of digestion. . Slowly digestible starches (SDS) acquire more time to degrade. . Resistant starch (RS) generally escapes digestion in the small intestine and passes through the large intestine as dietary fiber for fermentation by bacteria, where it helps to maintain colon health and protect against disease 106 53
  54. 8/1/2016 Starch modificatiion • Starch modifications are a means of altering the structure and affecting the hydrogen bonding in a controllable manner to enhance and extend their application. The alterations take place at the molecular level, with little or no change taking place in the superficial appearance of the granule. Therefore, the botanical origin of the starch may still be identified microscopically 107 Hạt tinh bột khoai tây ở thời điểm trước và sau biến tính bằng enzyme amylase 108 54
  55. 8/1/2016 TINH BỘT Biến tính tinh bột (Starch modification)  Phương pháp vật lý  Phương pháp hóa học  Phương pháp hóa sinh (enzyme) 109 TINH BỘT Biến tính tinh bột (Starch modification)  Phương pháp vật lý  Phương pháp hóa học  Phương pháp hóa sinh (enzyme) 110 55
  56. 8/1/2016 TINH BỘT Biến tính tinh bột (Starch modification) Phương pháp vật lý: Tiền hồ hóa (Pre-gelatinisation)  Mục đích: pregelatinisation is designed to remove the necessity for cooking.  Phương pháp: tinh bột ban đầu được hồ hóa trong một lượng thừa nước, sau đó sấy để tách ẩm. 111 Drum Drying 112 56
  57. 8/1/2016 113 Production of pre-gelatinized wheat starch Wheat starch was first dispersed in cold water (10% w/w, starch in water), then, it was dried using a twin drum drier (Model Benton Harbor, USA) at drum speed of 5 rpm, steam pressure of 5 bar, clearance between the drums of 0.4 mm and the surface temperature was 158 °C. The dried starch sheet with moisture content of 7.3% ± 0.2 (dry weight basis) was milled using a laboratory mill and then sieved to obtain a powder with particle size of 150-250 μm. The PGS was packed in polyethylene bags and stored at room temperature for further experiments. 114 57
  58. 8/1/2016 Twin Drum Drier 115 Pre-gelatinized Wheat Starch 116 58
  59. 8/1/2016 Pre-gelatinized Wheat Starch 117 Pre-gelatinized Wheat Starch A cold water viscosity of 3833 centi Poise (cP) was observed for PGS at 25 ºC, while no peak was seen for the native starch at this temperature. For the latter, a peak viscosity of 2011 cP was observed at 95 ºC when the sample was held for 11 min. 118 59
  60. 8/1/2016 Pre-gelatinized Wheat Starch . The PGS had the ability to increase the viscosity at temperatures below gelatinization temperature of native starch. At high temperatures, however, the native starch was able to increase the viscosity. . Moreover, if PGS is heated and then cooled down, it produces lower final viscosity than native starch. 119 120 60
  61. 8/1/2016 Keywords Imitation cheese 121 Keywords Imitation cheese Imitation (analogue) cheese products may be classifed as cheese substitutes or imitations, which partly or wholly substitute or imitate cheese and in which milk fat, milk protein or both are partially or wholly replaced by non-milk-based components, principally of vegetable origin. Ingredients such as rennet casein, vegetable oils or fats, salts, acids and Xavourings are generally used in the manufacture of imitation cheese. Rennet casein: Due to its high cost, considerable eVort has been vested in the partial replacement of casein with cheaper ingredients, of which, starch has been the most effective low-cost casein substitute 122 61
  62. 8/1/2016 Objectives • The objective of this study is to investigate the eVects of pre-gelatinised starches on the rheology, meltability and microstructure of imitation cheese. 123 Materials & methods: imitation cheese Water 48% Renet casein/PG starch 24.5% Vegetable fat 26% Emusifying salt (trisodium citrate, 2.18% citric acid, disodium phosphate) Sodium chloride 1.67% Sorbic acid 0.1% 62
  63. 8/1/2016 Rennet casein Control . Micro-structure PG maize . Melt . Hardness . Dynamic rheology replacing 15% . Viscosity PG waxy maize of the rennet casein by PGS PG wheat PG potato PG rice Results 126 63
  64. 8/1/2016 Micro - structure PGS had poorer fat emulsification. Imitation cheese products containing pre-gelatinized starches had larger fat globule size distributions (especially rice or waxy-maize starch). 128 64
  65. 8/1/2016 The G’ of all products decreased signiWcantly (P · 0.05) with increasing measuring temperature from 22 to 85 °C, due to melting of the vegetable fat and softening of the protein matrix. Imitation cheese containing potato starch had the highest G’ values in the temperature ranges 55–85 °C, which was possibly due to extensive starch retrogradation impeding the Xow of casein. 129 All products containing starch had significantly lower tan values at 22 °C (ranging from 0.36 - 0.02 for waxy-maize to 0.42 - 0.013 for rice starch- containing imitation cheese) compared to the control imitation cheese (0.44 - 0.012), indicating more elastic (less viscoelastic) structural behaviour compared to the control. 130 65
  66. 8/1/2016 The replacement of 15% of the protein in the dispersions with pre-gelatinised starches resulted in increases in apparent viscosity in the order rice starch (26.3 - 1.2 mPa s) > waxy-maize (24.6 - 0.4 mPa s) > wheat (22.2 - 0.5 mPa s) > potato (21.6 - 0.6 mPa s) > maize (20.0 - 0.5 mPa s) starch. 131 TINH BỘT Biến tính tinh bột (Starch modification)  Phương pháp vật lý  Phương pháp hóa học  Phương pháp hóa sinh (enzyme) 132 66
  67. 8/1/2016 TINH BỘT Biến tính tinh bột (Starch modification) Phương pháp hóa học:  Acid hydrolysis  Oxidation  Cross-linking  Stabilisation  Lipophilic substitution  Dextrinisation 133 TINH BỘT Biến tính tinh bột (Starch modification) Phương pháp hóa học: Acid hydrolysis Water/alcol  When the starch is heated beyond its gelatinisation temperature the granules rupture quickly.  A lower hot viscosity due to the increase in the ratio of smaller, linear molecules  A stronger gel develops on cooling (set-back) 134 67
  68. 8/1/2016 TINH BỘT Biến tính tinh bột Phương pháp hóa học: (Starch modification) Oxidation Alkaline hypochlorite  The relatively bulky carboxyl (COOH) and carbonyl (C=O) groups are introduced together the bulky groups disrupts any tendency towards re-association (set back) of the shorter chains reduce the gel strength.  Partial depolymerisation of the starch chains a significantly reduced hot viscosity.  Bleaching 135  Độ nhớt khi hạt tinh trương nở cực đại  Tính bền nhiệt: sự thay đổi độ nhớt ở nhiệt độ cao  Tốc độ hồ hóa  Độ bền gel: độ nhớt khi tạo gel 136 68
  69. 8/1/2016 TINH BỘT Biến tính tinh bột Phương pháp hóa học: (Starch modification) Cross - linking Cross – linking Distarch phosphates Distarch adipates Replacement of the hydrogen bonding between starch chains by stronger, more permanent, covalent bonds: typically one cross-link per 100–3000 anhydroglucose units of the starch:  The swelling of the starch granule is inhibited;  The starch becomes more resistant to gelatinisation;  Heat and shear stability over their parent native starches. 137 138 69
  70. 8/1/2016 distarch phosphate acetate-adipate starch. 139 TINH BỘT Biến tính tinh bột Phương pháp hóa học: (Starch modification) Stabilisation Acetylated Hydroxypropylated  Bulky groups are substituted onto the starch to take up space and hinder (steric hindrance) any tendency for dispersed (cooked), linear fragments to re-align and retrograde (freezethaw cycles).  Degree of Substitution (DS): is a measure of the number of substituents per 100 anhydroglucose units (those with DS below 0.2 are typically used).  Easy cooking, particularly useful in low-moisture environments and where the moisture level is restricted by competition from co- ingredients. 140 70
  71. 8/1/2016 E1420: acetylated starch  Độ nhớt khi hạt tinh trương nở cực đại  Tính bền nhiệt: sự thay đổi độ nhớt ở nhiệt độ cao  Tốc độ hồ hóa  Độ bền gel: độ nhớt khi tạo gel 141 TINH BỘT Biến tính tinh bột Phương pháp hóa học: (Starch modification) Lipophilic substitution Hydrocarbon chain The glucose part of starch binds the water while the lipophilic part binds the oil emulsion stabilisation. 142 71
  72. 8/1/2016 TINH BỘT Biến tính tinh bột Phương pháp hóa học: (Starch modification) Dextrinisation (a) (b)  (a) Depolymerisation: dry roasting the starch either alone, making use of its natural 10–20% moisture content, or in the presence of catalytic quantities of acid.  (b) Recombination: in a branched manner. 143 TINH BỘT Biến tính tinh bột (Starch modification) Combination treatments are used to achieve the desired objective:  Cross-linking/Stabilisation  Cross-linking/Stabilisation/Pregelatinisation 144 72
  73. 8/1/2016  Độ nhớt khi hạt tinh trương nở cực đại  sự thay đổi độ nhớt ở nhiệt độ cao  Tốc độ hồ hóa  Độ bền gel: độ nhớt khi tạo gel 145  Độ nhớt khi hạt tinh trương nở cực đại  Tính bền nhiệt: sự thay đổi độ nhớt ở nhiệt độ cao  Tốc độ hồ hóa  Độ bền gel: độ nhớt khi tạo gel E1412: distarch phosphate (Cross-linking) E1414: acetylated distarch phosphate (Cross-linking/Stabilisation) E1422: acetylated distarch adipate (Cross-linking/Stabilisation) 146 73
  74. 8/1/2016 TINH BỘT Biến tính tinh bột (Starch modification)  Phương pháp vật lý  Phương pháp hóa học  Phương pháp hóa sinh 147 TINH BỘT Biến tính tinh bột (Starch modification) Phương pháp hóa sinh 74
  75. 8/1/2016 TINH BỘT Biến tính tinh bột (Starch modification) Phương pháp hóa sinh Dextrose Equivalent (DE):  DE = 100: dextrose (glucose)  DE = 0: starch  DE = 50: maltose  DE < 20: maltodextrin  DE = 20 ÷ 100: glucose syrup 149 Bai bao dual starch 150 75
  76. 8/1/2016 151 76