Valuable furan fatty acids in soybeans and soy products

Franziska Müller,Melanie Hogg,Walter Vetter

doi:10.1007/s00217-020-03497-w

Franziska Müller, Melanie Hogg + Show 1 more

Open Access

https://doi.org/10.1007/s00217-020-03497-w

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Abstract

Furan fatty acids (FuFAs) are valuable minor compounds in our food with excellent antioxidant properties. Naturally occurring FuFAs are characterised by a central furan moiety with one or two methyl groups in β-/β’-position of the heterocycle (monomethyl- or M-FuFAs and dimethyl- or D-FuFAs). Comparably high concentrations of D-/M-FuFAs were reported in soybeans, but soy is often consumed as a processed product, such as full-fat soy flour and flakes, soy drink, tofu and texturised soy protein (TSP). Due to the chemical lability of D-/M-FuFAs, e.g. in the presence of light or oxygen, a degradation during the processing is possible. For this purpose, freshly harvested soybeans (n = 4) and differently processed soybean products (n = 22) were analysed on FuFAs. Three FuFAs, i.e. 11-(3,4-dimethyl-5-pentylfuran-2-yl)-undecanoic acid (11D5), 9-(3,4-dimethyl-5-pentylfuran-2-yl)-nonanoic acid (9D5), and 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid (9M5), were identified and quantified in all fresh soybeans and most of the processed soy products (n = 20). A trend towards lower D-/M-FuFA contents in higher processed products was observable. Lower FuFA concentrations were usually accompanied with a decrease of the share of the less stable D-FuFAs (9D5, 11D5) in favour of the M-FuFA 9M5. Furthermore, one or two 3,4-nonmethylated furan fatty acids (N-FuFAs), i.e. 8-(5-hexylfuran-2-yl)-octanoic acid (8F6) and partly 7-(5-heptylfuran-2-yl)-heptanoic acid (7F7), were detected in all processed products, but not in the freshly harvested soybeans. Our results indicate that D-/M-/N-FuFAs may serve as suitable markers for both, careful manufacturing processes and adequate storage conditions of soy products.

Highlights

Furan fatty acids (FuFAs) are a class of valuable minor fatty acids, characterised by a central furan building block within the acyl chain [1, 2]
The furan moiety is substituted with one methyl group in β-position or two methyl groups in β- and β-position
Four soybean samples planted in the south of Germany and harvested in autumn 2018 contained D-/M-FuFA concentrations of 14–21 mg/100 g fatty acid methyl esters (FAMEs)

Summary

Introduction

Furan fatty acids (FuFAs) are a class of valuable minor fatty acids, characterised by a central furan building block within the acyl chain [1, 2]. The carboxyalkyl chain is usually odd numbered (7–13 carbon atoms), while the terminal alkyl residue typically consists of a propyl or a pentyl group [1]. D-/M-FuFAs can effectively protect lipids from lipid peroxidation and organisms against oxidative stress and associated diseases [1, 8, 10,11,12,13]. The antioxidative capacity of FuFAs correlates with number of methyl groups on the furan ring (i.e., D-FuFAs > M-FuFAs) [12]. Anti-inflammatory effects were reported for FuFAs [14]

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