Foodchem Lecture 8 Pictures

"Becel - example of when interesterification allows one to change physical properties without forming trans fatty acids"

• "Production of monoglycerides from fat by reacting with excess glycerol"
• TG interesterified with excess glycerol produces predominantly monoglycerides

• "Van der Waals forces"
• Crystals are held together by Van der Waals forces (electrons moving in sympathy with one another) which form a 3D network, which holds the system together

• "Soft margarines"
• When a fat can be deformed readily, it is said to be in its 'plastic range', which is a function of the triglyceride faty acid composition and distribution
• Hence 'soft margarines' are fats specially formulated to have wide plastic range - to be plastic at refrigerator temperatures but still not melt at room temperature

• "Alpha-crystals"
• Have a somewhat random packing arrangement and are relatively unstable
• If holding temperature rises above the temperature of stability for the alpha-crystal form, it will sponaneously start to change to another crystalline form

• "Beta prime crystals"
• These crystals tend to be small and uniform, a desirable structure and are relatively stable
• If they re-melt and cool very slowly and form large beta crystals

• "Beta crystals"
• When beta prime crystals re-melt and cool very quickly, very dense large, beta crystals are produced
• Undesirable because they induce graininess (detected organoleptically) and reduce functionality

• "Dilatometer"
• Measurement of the solid fat content is commonly determined by dilatometry or NMR
• Based on the measurement of specific volume (the inverse of density) per unit temperature

• "Specific volume plotted as a function of temperature to produce a graph"
• A sigmoidal curve will be produced which has 3 general regions:
• A. Solid fat undergoing thermal expansion of the solid
• B. Representing expansion of solid and progressive dilation due to a change in state to a liquid
• C. Representing the expansion of the liquid only

• "Assuming that the solid line is parallel to the liquid line one can calculate the ratio of solid to liquid fat at a specific temperature"
• Calculation based on temperature selected:
• % solids at 25°C = (X₂₅/Y)*100

• "Examples of dilatometric curves for fats"
• utter and lard dilatometric profiles

• "NMR machine"
• Probing of the fat using radio waves and magnetic field - the radio waves causing the hydrogen in liquid fat molecules to resonate
• Measurement by NMR is termed solid fat content (SFC)
• The amount of resonance generated is proportional to the liquid portion of the fat

• "NMR absorption scan"
• Produced by NMR machine to determine solid fat content (SFC)

• "Shortening"
• Shortenings have the capability to reduce the elasicity of a dough to make pastry more tender/flakey
• Fats with higher levels of unsaturated fatty acids hve greater shortening power - often prepared by hydrogenation of vegetable oils

"Shortening plasticity can also be varied by changing varying the amount of nitrogen incorporated into the fat, which also whitens it"

• "Margarines are fat and oil blends which have extensively replaced butter, 2nd photo shows new ones with plant sterols"
• Margarine = water (about 20%) in oil emulsion with some milk solids

• "Enrobing fats"
• Typified by cocoa butter - used extensively to enrobe confectionary products or ice cream
• Has narrow melting point range and contains about 80% di-saturated triglycerides

• "Shortbread cookies"
• Incoporation of fats into baked products tends to shorten texture - reduces the interaction of the wheat proteins to produce a desirable crumbly texture required for cakes and cookies

• "Fats and oils used to manufacture salad dressings used with raw vegetables to provide lubrication and carry flavors"
• Used to manufacture mono/di-glyceride emulsifiers, which are required in the formulation of salad dressings - stabilize the emulsion formed by their polar/non-polar moieties

• "Pam"
• Source of phospholipid by-products also used extensively as emulsifiers, as food/pan release agents (like Pam) and anti-spattering agents

• "Monoglyceride structure"
• Have the characteristic of reducing the interfacial tension between oil and wter by bridging the two phases by having both hydrophilic and hydrophobic moieties within its molecular structure

• "Phospholipid"
• Have the characteristic of reducing the interfacial tension between oil and wter by bridging the two phases by having both hydrophilic and hydrophobic moieties within its molecular structure

• "Emulsion"
• Becoming viscoue, opaque, and the fatty sensation associated with oil is masked

• "There are specialty products - i.e. medium chain triglycerides - for clinical, health food/athletic markets"
• Sold extensively and expensively to athletes

• "Visible fat trends"
• Butter and lard are declining
• Major increase in salad/cooking oils from vegetble sources
• Margarine/shortening holding steady

• "Invisible fat trends"
• Major sources of invisible fats - meat, fish, poultry
• Followed by dairy products - milk, cream, cheese, but excluding butter
• Eggs are a relatively minor source as legumes, grains and nuts
• Fruits and vegetables very minor source of fat

• "Total fat consumed = Visible + Invisible"
• Fat consumption has been rising
• This trend has leveled off somewhat since 1985

• "Fat replacers - Olestra"
• All the properties of an oil, but not digesible