Purdue food scientists improve testing of health supplements

[Guest guest]

September 4, 2003

Purdue food scientists improve testing of health supplements

 

WEST LAFAYETTE, Ind. ­ Purdue University researchers have discovered a

faster, less expensive method to test the quality and purity of dietary

supplement oils, such as flax seed, borage seed and grape seed oil, often

touted as cures for many human maladies.

Lisa Mauer's research lab

Download photo - caption below

 

The research results are published in the September issue of the Journal of

Agricultural and Food Chemistry and on the journal's Web site.

 

" This study brings analytical chemistry, food science, nutritional sciences

and consumer interest together, " said Lisa Mauer, assistant professor of

food science. " Consumers want the salad dressing brand they buy to taste the

same every time. The same is true for special types of oils, which are more

expensive than a general cooking oil. You expect what you buy to be high

quality and contain what is on the label. "

 

Consumers are concerned about purity because of taste, safety, health

benefits and cost, she said. While oils that are less pure may be less

expensive, they may lose the flavor or health benefits, and some can even be

detrimental to health. In addition, consumer demand for food and food

additives is increasingly for organic or 100 percent natural products.

 

Manufacturers of health supplements and drugs are concerned with purity

because of quality control issues that impact safety of the substances and

company economics.

 

To address these concerns, scientists search for fast, effective,

inexpensive ways of differentiating between different ingredients ­ in this

case dietary supplement oils.

 

Purdue researchers used infrared spectroscopy and statistical analysis to

classify samples of 14 dietary supplement oils and five common food oils.

The scientists profiled the chemical makeup of at least two different brands

of each.

 

First, pure oil samples were tested to determine how well the spectroscopy

method, called Fourier-transform infrared spectroscopy (FT-IR), could

differentiate between each one. Then they mixed various amounts of each

cooking oil with one of the dietary oils and tested to determine if FT-IR

could identify the amounts of individual oils in the compounds.

 

FT-IR uses wavelengths of light to identify types of chemical bonds. Each

type of molecule absorbs light differently, producing a spectrum. Scientists

use this spectral information to identify the compound, much the way a

fingerprint can identify a person.

 

" We wanted to see how good FT-IR and common chemical measurement analyses

are at differentiating real-world whole samples instead of just one

component, " Mauer said. " This is the first time this method has been used to

differentiate a whole spectrum of food samples, such as the 19 oils used in

the study, instead of only comparing two sample types. "

 

Conventional methods for ensuring the makeup of dietary and special use oils

are time-consuming, she said. They involve multiple preparation steps and

analysis, which take as much as several hours, after the sample preparation

and initial analysis are complete. This painstaking process makes

traditional purity tests expensive. The FT-IR method took only five minutes

once the analytical procedure had been developed.

 

Many food and pharmaceutical companies already own FT-IR equipment, so there

would be no additional cost of using the new purity testing.

 

In their research, the Purdue scientists tested oil mixtures that had 2

percent to 20 percent by volume of common food oils.

 

The researchers found that the FT-IR method could identify the adulteration

down to 2 percent. They picked this range because food manufacturers have

said those are the levels they need to know for quality control of oil

mixtures, Mauer said.

 

The dietary supplement oils tested were almond, apricot kernel, black

currant, borage, cod liver, evening primrose, flax seed, grape seed,

hazelnut, hemp seed, macadamia nut, olive, pumpkin seed and wheat germ oils.

The common food oils were canola, corn, peanut, soybean and sunflower.

 

Though they didn't test for adulteration levels of oils that would cause

allergic reactions in people, such as those allergic to peanut products,

Mauer said the study indicated that the method likely could detect lower

levels of various oils. Other studies have shown that FT-IR can be used to

identify the region where the oil-producing plant was grown and the variety

of plant from which it came.

 

" It's interesting to see that some of the oils, such as canola oil and

pumpkin seed oil or hazelnut oil and olive oil, are structurally so

similar, " Mauer said. " It's based on the fatty acid composition. But while

you see dietary claims related to pumpkin seed oil, I don't know of any

canola oil being sold in capsules for health purposes. "

 

The other researchers involved with this study were Banu Ozen, postdoctoral

fellow, and Ilan Weiss, graduate research assistant, both of the Department

of Food Science.

 

The Purdue University Agricultural Research Programs provided funding for

this research.

 

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