The possibilities of increasing lignan content in food

Abstract

Lignans are bioactive substances which belong to polyphenols. This compounds can be found in plants including coniferous trees. Lignans are secondary plant metabolites with wide range of biological effects, such as antimicrobial, antivirus or anticancer. They also serve as antioxidants and are naturally occurring compounds which are found in food rich in fibre. There are more than 200 lignans that originate from more than 70 plant families. They can be found in all parts of the plant, mainly in seeds. Almost 37% of total lignan intake in human diet comes from drinking tea and coffee. Fruit and vegetable contain only about 1% of lignans, but they are also significant source of lignans because they are consumed in higher amounts than seeds. 7-hydroxymatairesinol is the main representative of lignans. It is white powder with great health benefits and it is present in the knots of coniferous trees, especially in knots of spruce. Lignans were extracted from the knots and used for fortifying fruit and vegetable spreads. Subsequently, the fortified products became subject to sensory analysis, their antioxidant capacity was measured by the FRAP method, total polyphenols content was found and lignan content determined using the HPLC method. The aim was enriching commonly consumed foods by healthy lignans to avoid negative effects on the sensory quality of these products by the bitter taste of the lignan extract. Of the tested foods, plum jam and red pepper paste are the best options as they best block the bitter taste of lignans. There was a positive increase in antioxidant capacity in food products fortified by the lignan extract. For plum jam, strawberry jam, strawberry spread and red pepper paste, the more lignans were added to the products, the greater was the level of antioxidant capacity. The highest antioxidant capacity was reached in samples with the added amount of 340 mg of lignan per kg of product. As with the antioxidant capacity, total polyphenols content is dependent on the quantity of added lignans. Plum jam is the only exception, for which there was no statistically evident difference between the doses of 170 mg and 340 mg of lignans per kg. The values of lignans measured for samples with added 340 mg of lignans per kg range from 313 mg to 339 mg. For samples with addition of 170 mg of lignans per kg the measured values range from 129 to 164 mg per kg. Although lignans are beneficial for health, they are not acceptable to deteriorate taste of the product. The samples containing the highest dose of lignans, i.e. 340 mg of lignans per kg, were rated as the least acceptable by consumer. Evaluated as the most suitable in this regard was plum jam with a dose of 170 mg of lignans per kg of product where lignans were not found to possess a sensory effect on the acceptability of the product.