Writing in the Journal of Agricultural and Food Chemistry , researchers from the August Cieszkowski Agricultural University of Poznan in Poland report that the seed extract prevented the oxidation of lipids, and could extend the shelf-life of the breakfast.
"In our study red raspberry seed extract inhibited lipid oxidation in analyzed muesli samples as could be observed in the differences in content of volatile lipid oxidation products," wrote Dorota Klensporf and Henryk Jelen.
"Raspberry seed extract can be a suitable antioxidant added to muesli and probably other cereal products."
The research taps into growing interest in plant-derived food additives as replacements to synthetic antioxidants like butylhydroxyanisole (BHA) and butylated hydroxytoluene (BHT) to slow down the oxidative deterioration of food.
Indeed, according to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts (particularly rosemary), tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by easier consumer acceptance and legal requirements for market access.
And the natural label is even more important in foods such as muesli, consumed because of their healthy reputation.
According to background information in the article, the health components of muesli include ingredients such as nuts that are rich in omega-3 fatty acids.
"However, the higher lipid content in muesli and the composition of fatty acids make these products very susceptible to lipid oxidation," wrote Klensporf and Jelen.
"Lipid autoxidation leads to the formation of hydroperoxides, which decompose to secondary oxidation products, such as aldehydes, ketones, alcohols, and furans.
These compounds are associated with changes in the odour and flavour."
Laboratory muesli Klensporf and Jelen prepare a mixture of oat flakes, wheat flakes, corn flakes, hazelnuts, raisins, sunflower seeds, and flax seeds with and without the raspberry seed extract.
The lab-made muesli was then subjected to accelerated storage tests at 60 degrees Celsius.
Using a variety of analytical techniques, the researchers observed that the raspberry seed extract inhibited the rate of lipid oxidation, with a third the quantity of volatiles and hexanal as the control muesli after 14 days.
They also report that the flavour dilution factor (FD) values - a measure of levels of odour-active products of lipid oxidation products - were lower in the muesli prepared with the raspberry seed extract.
Source: Journal of Agricultural and Food Chemistry Published online ahead of print 5 April 2008, ASAP Article, doi: 10.1021/jf0729210 "Influence of the Addition of Raspberry Seed Extract on Changes in the Volatile Pattern of Stored Model Breakfast Cereal" Authors: D. Klensporf, H.H. Jelen