Trans Fat

Lab to Label

What is trans fat?

Chemically: Geometric isomers of the natural cis form of unsaturated fatty acids

Physically: Fatty acids modified to have a higher melting point by changing their configuration from bent to straight.

What is a Trans Fat?

Oleic (9-cis-C18:1)mp: 13-14C

Elaidic (9-trans-C18:1)mp: 44-45C

Where Does Trans Fat Come From?

Chemical Hydrogenation of Vegetable Oils (may be >50%)

Biochemical Hydrogenation by Rumen Bacteria (5% or less)

Some Food Labeling History

Nutrition Labeling & Education Act 1990Major Change in Fat DefinitionNew Fat Methodologies RequiredOnly “cis” fats included in unsaturatesCall for Trans Fat LabelingDecision Delayed Pending Better Data

Trans Added to Label

Amended to Include TransRequired by Jan 2006

Why Trans Fat?

Trans Fat Raises LDL Cholesterol/Lowers HDLTrans Fat Increases Plasma TGsMay Be Stronger CHD Factor than Saturated FatUp to 100,000 Premature Deaths/yr in USAverage US Consumer Gets 2% of Calories from Trans Fat

What Foods Contain Trans Fat?

Margarines (Hard varieties are higher)Shortenings and Frying FatsFried FoodsBeef and Dairy FatsBakery Products

But . . . . Changing Rapidly

How Are They Measured?

Usually complex mixturesPHVO can have >40 isomers of 18 Carbon FAMore than 15 isomers of linoleic acids

Hydrogenation Increases Complexity

Salad Oil – no hydrogenation

C18:0

C18:1 C18:2

Hydrogenation Increases Complexity

Margarine C18 region only

C18:1 C18:2

Trans C18:1

How Are They Measured?

FTIR for Process Control of Fats and Oils(high levels, not for complex foods, specific)

HRGC for Products and Ingredients(low levels, complex foods, not specific)

Ag+ Chromatography/GC(Not practical at present, but may be useful in future)

Accurate Measurement ofTrans Fat in Foods

Specialized GC Capillary ColumnsVery Long Columns (100 meters)Optimized Separation of Trans Fats

Overview of Methodfor Measuring Fat

Crude Extract

Saponify with KOH

Esterify with Acid/MeOH

Separate and Measure by GCCriti

cal step fo

r trans fa

t

Optimized Trans Analysis

Standard Separation(Could underestimateTrans by up to 25%)

Optimized Separation

Optimized Trans Fat Separation

100 Meter Capillary ColumnSpecialized Stationary PhasesIsothermal Column TemperatureSplit Injection

US and Canadian Food Labels

US Canada

List Separately

List Sum

Trans Fat Label Requirements

USLabel trans fat >0.5 g per servingIf total fat < 0.5 g per serving, not required, but“Not a significant source of trans fat”No fat or cholesterol claims allowed

No nutrient content claims for trans fat

CanadaBoth sat fat and trans fat <0.2 g per serving to list as “zero”Limited use of “Not a significant source”

Future

Other Label Changes Being StudiedMay Add a %DV for Trans FatMay Allow Nutrient Content Claims for Trans Fat

Trans Fats Rapidly Disappearing from Food Products

Online Resources

Harvard School of Public Health Trans Fat Report:http://www.hsph.harvard.edu/reviews/transfats.html

FDA Trans Fat Labeling Q&A Siteshttp://www.cfsan.fda.gov/label.htmlhttp://www.cfsan.fda.gov/~dms/qatrans2.html