Triterpene saponins as bitter components of beetroot

Abstract

S u m m a r yMany varieties of beetroots (Beta vulgaris L.) are valued for their productivity as well as their content of nutrients and pigments from a group of betalains that have strong antioxidant properties. On the other hand, the strong bitterness of roots of several beet varieties is a frequent reason for their being not accepted by consumers. The hitherto published studies describe too vaguely the diversity of beetroot varieties in terms of their bitter taste. Up to now, it is still not clear, which of the secondary metabolites that naturally occur in beetroots is responsible for their bitter taste and aftertaste. The objective of this study was to determine the group of compounds that caused that beetroots had a bitter taste and bitter aftertaste of a high intensity level. The first stage in the research study was to select the most bitter beetroot cultivars based on the sensory characteristics of fresh beet roots (of their flesh and skin) of six cultivars ('Nochowski', 'Chrobry', 'Noe 21', 'Rywal', 'Opolski', and 'Wodan'). The sensory profile of the analysed group of beets showed that the flesh and skin of the 'Nochowski', 'Chrobry', and 'Noe 21' cultivars were characterized by the most intense bitterness. The 'Rywal', 'Opolski', and 'Wodan' cultivars were marked by a relatively low intensity level of the bitterness notes. A mixture of triterpene saponins was isolated from a lyophilisate in the roots of the 'Nochowski' cultivar that, according to the sensory evaluation results, was classified into the group with the strongest bitterness traits. The results of sensory analyses of the saponin mixture of the 'Nochowski' cultivar, its concentration being C = 1.3515 g/dm 3 , confirmed that the group of those compounds had a strong bitter taste comparable to that of the quinine solution at a C 2 = 6.6 × 10 -3 g/dm 3 concentration. It was also proved that the beetroot extracts tested were a mixture composed exclusively of saponin compounds, which varied in their chemical structure.

Bidirectional Recurrent Half‐Sib Family Selection for Geosmin Concentration in Table Beet

“…It could be there is some other factor that tasters are perceiving, such as not masking color sufficiently or another culinary quality yet to be determined. A recent body of work regarding saponins, a bitter taste, could be an influencing characteristic (Mikoajczyk‐Bator and Kikut‐Ligaj, 2016). Another important variable might be the epidermis and should remain on for taste tests (Archer and Stokes, 1978; Bach et al, 2014).…”

An overview of bitter compounds in foodstuffs: Classifications, evaluation methods for sensory contribution, separation and identification techniques, and mechanism of bitter taste transduction

“…Terpenoids (terpenes and their oxygenated derivatives) are the most important secondary metabolites widely distributed in medicinal plants and some well‐known foods and beverages, such as bitter melon (Tan et al., 2016), Kuding tea ( Ilex kudingcha C.J. Tseng) (Wüpper et al., 2020), and red beet ( Beta vulgaris L.) (Mikolajczyk‐Bator & Kikut‐Ligaj, 2016), imparting them a remarkable bitter taste. Terpenoids are natural compounds derived from isoprene and could be classified into six groups based on their number of carbon atoms: monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), triterpenes (C30), tetraterpenes (C40), and polyterpenes (C > 40) (Sülsen, 2021).…”

“…However, momordicines I and II and momordicosides K and L have long been known as the main determinants of bitterness in bitter melon (Tan et al., 2016). The root of red beets is typically consumed as a kind of vegetable, and bitter red beet cultivars are desirable in the food industry due to their high contents of betalain pigment and strong antioxidant properties (Mikolajczyk‐Bator & Kikut‐Ligaj, 2016). A mixture of triterpenoid saponins from the roots of the red beet cultivar “Nochowski” was found to be responsible for its intense bitterness (Mikolajczyk‐Bator & Kikut‐Ligaj, 2016).…”

The significance of saponins in shaping the quality of food products from red beet [pdf]

“…A bitter taste is generally caused by different groups of chemical compounds, including the triterpene saponins present in beets (MikołajczykBator and KikutLigaj, 2016). Based on the conducted control test of a saponin sample (aqueous extract), the selected evaluators determined the kind of taste quality among different taste attributes -sweetness, bitterness, astringency or sourness, demonstrated by the saponin extract.…”

“…The triterpene saponins in red beets constitute a group of natural compounds which have an influence on the sensation of the bitter features of food products obtained from this raw material (MikołajczykBator, 2018;MikołajczykBator and KikutLigaj, 2016). Cultivars of red beet differ in terms of their saponin profile and content, which may affect the different health and sensory qualities of finished food products.…”