Foodchem Lecture 8 Pictures

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Foodchem Lecture 8 Pictures
2012-02-12 21:24:59
Foodchem Lecture Pictures

Foodchem Lecture 8 Pictures
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  1. "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
  2. "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