食品添加剂 乳化剂
合集下载
相关主题
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
The higher the surface tension, the less the two materials like each other 界面张力越高，两种物质越难混合
Interfacial tension
The unbalanced force between two surfaces contacted.
Interfacial tension
oil
Surface Tension is derived from the unbalance force at the surface:
Fwater-water-Fwater-air
表面不平衡的力造成表面张力
Rain drop
GH TS
∝Surface tension *Contacting Area
Generally, hydrophilic and hydrophobic liquids are immiscible
How an amphiphilic looks like and be called
Surfactant, surface active agent, emulsifier
Class of molecules which contain hydrophobic (non-polar) hydrocarbon "tails" and a hydrophilic (polar) "head" group. 一类含有亲水的头和亲油的尾 “like dissolves like“ 相似相容
Oil in water
Water in oil
由于表面积巨大，乳液热力学不稳定，要乳液稳定，必须加入乳化剂
2. How emulsifiers are classified?
Based on their ionic property
Anionic –
Sodium stearate, Potassium laurate Sodium dodecyl sulfate Sodium sulfosuccinate – Polyglycol, Fatty acid esters, Lecithin Quaternary ammonium salts, Amine hydrochlorides
Based on their sources
Natural 天然 Synthetic 合成
来源
Based on solubility
溶解性
Water soluble and oil soluble emulsifiers
How emulsions are classified?
- Based on dispersed phase 根据分散相 Oil in Water (O/W): Oil droplets dispersed in water Water in Oil (W/O): Water droplets dispersed in oil - Based on size of liquid droplets 分散相尺寸 0.2 – 50 mm Macroemulsions (Kinetically Stable,动 力学) 0.01 – 0.2 mm Microemulsions (Thermodynamically Stable，热力学)
油溶性乳化剂倾向于形成油包水型乳液
More polar the oil phase, the more hydrophilic the emulsifier should be. More non-polar the oil phase more lipophilic the emulsifier should be.
1. Introduction
What is emulsion? – Suspension of liquid droplets (dispersed phase) of certain size within a second immiscible liquid (continuous phase).
Baidu Nhomakorabea
oil in water type O/W emulsion
water in Oil type W/O emulsion
Continuous phase / domain
连续相
Bicontinuous phase双连续相
3. Tests for Emulsion Type (W/O or O/W emulsions)
油相的极性越大，需要的乳化剂亲水性也越强
Selection methods
HLB method – HLB indicative of emulsification behavior. HLB 3-6 for 8-18 for W/O O/W
HLB no. of a surfactant depend on which phase of the final emulsion it will become. Limitation – does not take into account the effect of temperature.
Emulsion, continuous phase and dispersed phase 连续相和分散相
What if oil and water are blended?
Blending means increasing in contacting area
Strong mechanical stir
separation
oil
water
Oil droplet
Contacting area ↑ Contacting area ↓
Why separation? Why minimum surface area?
The molecules at the surface of a liquid are subjected to an unbalanced force of molecular attraction as the molecules of the liquid tend to pull those at the surface inward while the vapor does not have as strong an attraction. This unbalance causes liquids to tend to maintain a minimum surface area. The magnitude of this force is called the surface tension.
Material’s nature
hydrophilic Amphiphilic
it has a surface to which water is attracted
It attracts both water and oil
hydrophobic
it has a surface to which water is “afraid”
An emulsion is a liquid-liquid (oil-water) suspension that is small drops of one liquid dispersed in another liquid. 乳液是一种液体以微粒的形式分散在另一种液
体中混合物（悬浮液）
Water and oil
G H TS
∝Interfacial
tension
×Contacting Area
The higher the interfacial tension, the less the two materials like each other
But……it is hard to decrease the
Chapter XI Emulsifiers
1. Introduction 2. Types and classification of emulsifiers and emulsions 3. Tests for emulsion types 4. General guidelines 5. More……in Chinese
Oil
Oil is disguised as hydrophilic liquid while water is disguised as hydrophobic one 油的界面水化，水的界面油化
亲油 油相
介质 乳化剂、表面活性剂 稳定剂
亲水 水
More on emulsification and emulsifier
Due to the large specific interfacial area, emulsion is not stable thermodynamically. In order to stabilize an emulsion a third substance known as an emulsifying agent should be added.
interfacial tension by altering the intrinsic properties of each bulk phase 既然界面张力仅仅发生在界面，
要改变它，最有效的方法就是从界面开始
How to alter the interface only?
Add something to adhere to the interface. Something that is attracted by both side oil and water and hence reduce the interfacial tension 如何仅改变界面的性质？ 加入一些“粘附”于界面的物质，这些物质受到界面两边比较均衡的力， 从而减少了界面张力
Water-oil emulsion
Any liquid immiscible with water is named as oil.
Emulsions encountered in everyday life!
Pesticide
Asphalt
Skin cream
Ice cream Metal cutting oils Margarine Stability of emulsions may be engineered to vary from seconds to years depending on application 乳液稳定性可以长达数年或者数秒
Nonionic Cationic – 阴离子 非离子 阳离子
硬脂酸钠、月桂酸钠 聚乙二醇 季铵盐，氯化铵
How emulsifiers are classified?continued
Based on their molecular weight分子量
Polymeric surfactant 高分子 Low molecular weight surfactant 低分子量
4. General Guidelines
Type of emulsion determined by the phase in which emulsifier is placed.
乳液的类型由乳化剂所处的相有关
Emulsifying agents that are preferentially oil soluble form W/O emulsions and vice versa.
Based on the Bancroft’s rule, many emulsion properties are governed by the properties of the continuous phase （连续相）乳液性质主要连续相决定
Dye test 染料测试 Dilution test 稀释 Electrical conductivity measurements 电导 Refractive index measurement 折光 Filter paper test 滤纸
Interfacial tension
The unbalanced force between two surfaces contacted.
Interfacial tension
oil
Surface Tension is derived from the unbalance force at the surface:
Fwater-water-Fwater-air
表面不平衡的力造成表面张力
Rain drop
GH TS
∝Surface tension *Contacting Area
Generally, hydrophilic and hydrophobic liquids are immiscible
How an amphiphilic looks like and be called
Surfactant, surface active agent, emulsifier
Class of molecules which contain hydrophobic (non-polar) hydrocarbon "tails" and a hydrophilic (polar) "head" group. 一类含有亲水的头和亲油的尾 “like dissolves like“ 相似相容
Oil in water
Water in oil
由于表面积巨大，乳液热力学不稳定，要乳液稳定，必须加入乳化剂
2. How emulsifiers are classified?
Based on their ionic property
Anionic –
Sodium stearate, Potassium laurate Sodium dodecyl sulfate Sodium sulfosuccinate – Polyglycol, Fatty acid esters, Lecithin Quaternary ammonium salts, Amine hydrochlorides
Based on their sources
Natural 天然 Synthetic 合成
来源
Based on solubility
溶解性
Water soluble and oil soluble emulsifiers
How emulsions are classified?
- Based on dispersed phase 根据分散相 Oil in Water (O/W): Oil droplets dispersed in water Water in Oil (W/O): Water droplets dispersed in oil - Based on size of liquid droplets 分散相尺寸 0.2 – 50 mm Macroemulsions (Kinetically Stable,动 力学) 0.01 – 0.2 mm Microemulsions (Thermodynamically Stable，热力学)
油溶性乳化剂倾向于形成油包水型乳液
More polar the oil phase, the more hydrophilic the emulsifier should be. More non-polar the oil phase more lipophilic the emulsifier should be.
1. Introduction
What is emulsion? – Suspension of liquid droplets (dispersed phase) of certain size within a second immiscible liquid (continuous phase).
Baidu Nhomakorabea
oil in water type O/W emulsion
water in Oil type W/O emulsion
Continuous phase / domain
连续相
Bicontinuous phase双连续相
3. Tests for Emulsion Type (W/O or O/W emulsions)
油相的极性越大，需要的乳化剂亲水性也越强
Selection methods
HLB method – HLB indicative of emulsification behavior. HLB 3-6 for 8-18 for W/O O/W
HLB no. of a surfactant depend on which phase of the final emulsion it will become. Limitation – does not take into account the effect of temperature.
Emulsion, continuous phase and dispersed phase 连续相和分散相
What if oil and water are blended?
Blending means increasing in contacting area
Strong mechanical stir
separation
oil
water
Oil droplet
Contacting area ↑ Contacting area ↓
Why separation? Why minimum surface area?
The molecules at the surface of a liquid are subjected to an unbalanced force of molecular attraction as the molecules of the liquid tend to pull those at the surface inward while the vapor does not have as strong an attraction. This unbalance causes liquids to tend to maintain a minimum surface area. The magnitude of this force is called the surface tension.
Material’s nature
hydrophilic Amphiphilic
it has a surface to which water is attracted
It attracts both water and oil
hydrophobic
it has a surface to which water is “afraid”
An emulsion is a liquid-liquid (oil-water) suspension that is small drops of one liquid dispersed in another liquid. 乳液是一种液体以微粒的形式分散在另一种液
体中混合物（悬浮液）
Water and oil
G H TS
∝Interfacial
tension
×Contacting Area
The higher the interfacial tension, the less the two materials like each other
But……it is hard to decrease the
Chapter XI Emulsifiers
1. Introduction 2. Types and classification of emulsifiers and emulsions 3. Tests for emulsion types 4. General guidelines 5. More……in Chinese
Oil
Oil is disguised as hydrophilic liquid while water is disguised as hydrophobic one 油的界面水化，水的界面油化
亲油 油相
介质 乳化剂、表面活性剂 稳定剂
亲水 水
More on emulsification and emulsifier
Due to the large specific interfacial area, emulsion is not stable thermodynamically. In order to stabilize an emulsion a third substance known as an emulsifying agent should be added.
interfacial tension by altering the intrinsic properties of each bulk phase 既然界面张力仅仅发生在界面，
要改变它，最有效的方法就是从界面开始
How to alter the interface only?
Add something to adhere to the interface. Something that is attracted by both side oil and water and hence reduce the interfacial tension 如何仅改变界面的性质？ 加入一些“粘附”于界面的物质，这些物质受到界面两边比较均衡的力， 从而减少了界面张力
Water-oil emulsion
Any liquid immiscible with water is named as oil.
Emulsions encountered in everyday life!
Pesticide
Asphalt
Skin cream
Ice cream Metal cutting oils Margarine Stability of emulsions may be engineered to vary from seconds to years depending on application 乳液稳定性可以长达数年或者数秒
Nonionic Cationic – 阴离子 非离子 阳离子
硬脂酸钠、月桂酸钠 聚乙二醇 季铵盐，氯化铵
How emulsifiers are classified?continued
Based on their molecular weight分子量
Polymeric surfactant 高分子 Low molecular weight surfactant 低分子量
4. General Guidelines
Type of emulsion determined by the phase in which emulsifier is placed.
乳液的类型由乳化剂所处的相有关
Emulsifying agents that are preferentially oil soluble form W/O emulsions and vice versa.
Based on the Bancroft’s rule, many emulsion properties are governed by the properties of the continuous phase （连续相）乳液性质主要连续相决定
Dye test 染料测试 Dilution test 稀释 Electrical conductivity measurements 电导 Refractive index measurement 折光 Filter paper test 滤纸