Chapter 4

Hydrolyzing all the ester bonds with a strong base and then analyzing the composition of the resulting mixture with Gas chromotography

Less than 1 % with the exception of olive oil

Fatty acid composition

increases with increasing chain length  decreases with increasing number of cis double bonds  increases with isomerization of cis double bonds to trans double bonds

Lipids from animal sources tend to be more saturated and are fats .  Lipids from plant sources tend to be more unsaturated and are oils .  Tropical oils such as coconut and palm are exceptions : They are highly saturated but have relatively low melting points because the fatty acids have short chain lengths

PUFAs

A process of conversion of vegetable oils to fats by decreasing their degree of unsaturation (addition of H 2 across the double bonds)

Cis to trans isomerization

Hydrogenated fats have been widely used in the manufacture of margarines and vegetable oil based shortenings

The fats & oils industry is now extensively using an alternative process interesterification ) to convert liquid oils to solid

 longer shelf life than oil or lard  greater stability and lower production costs than lard  faster dissolving and setting properties in chocolate production

 Concentrated source of energy  Source of essential fatty acids : linoleic acid, linolenic acid  Precursors for membrane lipids and prostaglandins  Carriers of fat soluble vitamins (A, D, E,  Help regulate body temperature  Protect vital organs from injury  Participate in cell production  Produce hormones and other secretions

 Heat transfer agents : Frying oils can reach very high temperatures 200 o C).  Transfer of heat to the surface of a food immersed in the oil drives off water as steam.  Both the high temperature and the loss of water are conditions that promote the Maillard reaction  During frying, oil is absorbed by the food and contributes to the sensory characteristics of the product (as well as its caloric content

Lipids tenderize baked products  Fats shorten flour s protein strands , which cause chewiness and toughness Aeration : Because lipids and air are both hydrophobic ; one of the functions of fats in baking is to incorporate air bubbles , which expand at baking temperatures and contribute to the volume and height of the baked product.

Flakiness

work best for biscuits, pies, and puff pastry

mix batters for products like pancakes, muffins, and waffles

Lubricating agents : for foods such as bread and salads , usually in the form of emulsions : oil in water (o/w) or water in oil (w/o).  Salad dressing is an o/w emulsion.  Butter is a w/o emulsion.

Much of the flavor in food is due to the addition of salt, sugar, and fats

Common lipids that season foods are butter, margarine, and mayonnaise

Dissolve and disperse

Cottonseed oil is one of the most flavorless oils, followed by vegetable shortening and soybean and canola

Contributors to texture/mouthfeel  Contributors to feeling of satiety (feeling

However, fats and oils are always composed of mixtures of triglycerides , and hence they melt ” over a wide temperature range Within this temperature range, the substance is a mixture of solid fat and liquid oil , defined by its solid fat content (SFC).  The plasticity of the fat ( ability to be molded or spread ) depends on the SFC.