4: Lipid Modification Flashcards
What is interesterification?
Shuffling of fatty acids within the triglycerides. (As the physical characteristics of a fat are greatly influenced by the positions of FAs in TGs).
* 2 types : chemical (using a catalyst: heating at 80-100 degrees C with sodium methoxide/alkali metals) and enzymatic
What is the effect of interesterification on lard?
No change in melting point; instead causes a physical change in characteristics / structure = changes from beta crystals (lard) to beta prime crystals (shortening) that makes it easier to use as spreads
What are the main differences between interesterification and hydrogenation?
Interesterification is more commonly used, costs more due to lipid loss; little or no trans FA produced; can blend soft oils with hard fats; produces spreadable plastic fats; Marg contains 24% PUFA
Rat studies show more essential PUFA in blood
Hydrogenation is cheaper and not used as much, contains trans fats & saturated FAs produced. Marg contains 5% PUFA. Increases LDL and lowers HDL.
Rat studies show low essential PUFA in blood
Explain the enzymatic process of interesterification
- Use of lipases (normally unwanted as they break down fats in spoilage reaction)
- rearranges structure of the triglycerides
- carried out under low temp; less damage to fat
- can be controlled & targeted !!
Under specific conditions lipases can catalyse the transfer of acyl residues between acyl glycerols and FAs instead
- The presence of water favours hydrolysis so increasing amount of organic solvent facilitates the acyl exchange reaction
* Lipases provide more specificity thus products unobtainable by chemical means can be produced
* Can be used to enrich TGs with desirable FAs
What are the differences between chemical and enzymatic interesterification
CHEMICAL
* low processing cost but high processing loss
* high levels of reaction by-products (e.g. glycerol)
* more processing steps
* higher temp process
* hazardous catalyst
* highly reproducible and easily controlled
ENZYMATIC
* high processing cost; minimum processing loss
* low levels of reaction by products
* better quality finished product
* less processing steps
* lower temp process
* more complex operation & control
* simple clean & safe. Eco friendly natural process
Explain the process of fractionation (winterisation)
- oil is cooled to 7.2 degrees C to allow high MP TGs to crystallise out
- high MP TGs removed by filtration
- resulting oil stays clear on cooling e.g. salad oils
- physical process, no chemicals used
Give an example of a common use of fractionation
In the production of cocoa butter equivalents (fats equivalent in TG composition & physical characteristics to cocoa butter, but cheaper)
- mid-fraction stage is used. Has sharp melting point with excellent mouth-feel like cocoa butter
Explain the steps in margarine production
- Fat phase : mixed oils + oil soluble additives (carotene, Vitamin A,D,E; emulsifiers)
combined with
Milk phase: ripened milk (streptococcus lactic; NaCl (salts); preservatives - Emulsification
- Cooling + drying (repeated phase until desired crystal structure obtained)
- Kneading
Explain the different types / examples of lipid modification in margarine production
Normal margarine = 85 parts interesterified mixed vegetable oils : 15 parts hydrogenated soybean oil
High PUFA, low-zero trans margarine = full hydrogenation using vegetable oil to solid fat (high in sats, low in trans) -> interesterification
Give examples of carbohydrate based fat substitutes
- avicel : microcrystalline cellulose derived from fruit / veg, no calories
- stellar : starch based product derived from corn. Reduces cals and fat while increasing complex carb intake
Neither suitable for frying
Give an example of a protein based fat substitute
Simplesse : microparticulated whey protein
Provides lubrication & similar texture
Similar to the way fat is dispersed in milk
Not suitable for frying
Give 3 examples of lipid based fat substitutes
(have the most acceptable tastes & applications of all fat substitutes)
* Olestra = sucrose polyester; no calories; body doesn’t recognise
- can be used for frying
- best palatability & no cals
- but not absorbed & has laxative effect
* Salatrim = TG with very short and very long FAs; not readily recognised by the body; lower calorie. Produced by interesterification
* Caprenin = TG with long chain FAs; not readily recognised by the body; lower calorie
