Consumer-Based Sensory Characterization of Steviol Glycosides (Rebaudioside A, D, and M)

A Computational Approach to Understanding and Predicting the Edulcorant Profile of Glucosyl Steviol Glycosides

Understanding the edulcorant profile of synthetic glucosyl steviol glycosides (GSGs) and rare natural steviol glycosides (SGs) is challenging due to their numerous species and rareness. This study developed a computational model based on the interactions of SG molecules with human sweet and bitter taste receptors (hSTR/hBTR). The models demonstrated a high correlation between the cumulative interaction energies and the perceived sweetness of SGs (R2 = 0.97), elucidating the mechanism of the diverse sweetness of SGs. It also revealed that more (within three) glucose residues at the C-13 position of the SG molecule yield stronger sweetness and weaker bitterness. Furthermore, the computational prediction was consistently validated with the known sweetness of GSG and also aligned well with that of several natural mogrosides. Thus, this model possesses a potential to predict the sweetness of SGs, GSGs, and mogrosides, facilitating the application or targeted synthesis of GSGs with desired sensory profiles.

Computational simulations on the taste mechanism of steviol glycosides based on their interactions with receptor proteins

Steviol glycoside (SG) is a potential natural sugar substitute. The taste of various SG structures differ significantly, while their mechanism has not been thoroughly investigated. To investigate the taste mechanism, molecular docking simulations of SGs with sweet taste receptor TAS1R2 and bitter taste receptor TAS2R4 were conducted. The result suggested that four flexible coils (regions) in TAS1R2 constructed a geometry open pocket in space responsible for the binding of sweeteners. Amino acids that form hydrogen bonds with sweeteners are located in different receptor regions. In bitterness simulation, fewer hydrogen bonds were formed with the increased size of SG molecules. Particularly, there was no interaction between RM and TAS2R4 due to its size, which explains the non-bitterness of RM. Molecular dynamics simulations further indicated that the number of hydrogen bonds between SGs and TAS1R2 was maintained during a simulation time of 50 ns, while sucrose was gradually released from the binding site, leading to the break of interaction. Conclusively, the high sweetness intensity of SG can be attributed to its durative concurrent interaction with the receptor's binding site, and such behavior was determined by the structure feature of SG.

Effects of aroma-taste interaction on the sensory attributes of rebaudiosides in soymilk and milk

BACKGROUND

Rebaudioside A (Reb-A) and rebaudioside M (Reb-M) are intense natural sweeteners but can also elicit bitterness and a bitter aftertaste. In this study, the effect of vanilla and chocolate flavorings on the sensory attributes of Reb-A and Reb-M applied to soymilk and milk was investigated to identify whether the addition of flavoring could enhance the sweetness via aroma-taste interactions.

RESULTS

Nine samples each of soymilk and milk were formulated by adding sucrose, Reb-A and Reb-M in three flavor conditions (no flavoring, vanilla, and chocolate). Descriptive analyses were conducted using nine panelists for the soymilk and eight panelists for the milk. Another descriptive analysis was conducted using the same samples with olfactory occlusion via the wearing of a nose clip to check whether the sweetness enhancement was due to olfactory input. The chocolate flavoring significantly enhanced the sweetness of Reb-A and Reb-M and reduced the bitterness, bitter aftertaste and astringency in both soymilk and milk. The vanilla flavoring was not as effective as the chocolate flavoring in enhancing sweetness. When the olfactory passage was closed with a nose clip, the sweetness enhancement and bitterness suppression were not detected in the samples.

CONCLUSION

The addition of chocolate flavoring could successfully improve the sensory profile of soymilk sweetened with Reb-A through aroma-taste interactions. © 2023 Society of Chemical Industry.

Steviol Glycosides from Stevia rebaudiana: An Updated Overview of Their Sweetening Activity, Pharmacological Properties, and Safety Aspects

This literature-based review synthesizes the available scientific information about steviol glycosides as natural sweeteners and molecules with therapeutic potential. In addition, it discusses the safety concerns regarding human consumption. Steviol glycosides exhibit a superior sweetener proficiency to that of sucrose and are noncaloric, noncariogenic, and nonfermentative. Scientific evidence encourages stevioside and rebaudioside A as sweetener alternatives to sucrose and supports their use based on their absences of harmful effects on human health. Moreover, these active compounds isolated from Stevia rebaudiana possess interesting medicinal activities, including antidiabetic, antihypertensive, anti-inflammatory, antioxidant, anticancer, and antidiarrheal activity. The described bioactivities of steviol glycosides deserve special attention based on their dose dependence and specific pathological situations. Further clinical research is needed to understand underlying mechanisms of action, therapeutic indexes, and pharmacological applications.

Transglycosylation of Stevioside by a Commercial β-Glucanase with Fungal Extracted β-Glucans as Donors

Abstract

Alternative sweeteners, such as steviol glucosides from the plant Stevia rebaudiana Bertoni, are becoming increasingly popular for the design of next-generation foodstuffs. However, the bitter aftertaste of native steviol glucosides is one of the main reasons behind consumer reluctance towards stevia-containing products. Biocatalysis could be a sustainable solution to this problem, through addition of glucosyl moieties to the molecule. Glycoside hydrolases are enzymes performing transglycosylation reactions, and they can be exploited for such modifications. In the present work, the commercial β-glucanase Finizym 250L® was employed for the transglycosylation of stevioside. After optimization of several reaction parameters, the maximal reaction yield obtained was 19%, with barley β-glucan as the glycosyl donor. With the aim to develop a sustainable process, β-glucan extracts from different fungal sources were prepared. Pulsed Electric Field pretreatment of mycelial biomass resulted in extracts with higher β-glucan content. The extracts were tested as alternative glucosyl donors, reaching up to 15.5% conversion yield, from Pleurotus-extracted β-glucan. Overall, in the present work a novel enzymatic process for the modification of stevioside is proposed, with concomitant valorization of β-glucans extracted from fungal biomass, potentially generated as a byproduct from other applications, in concert with the principles of circular economy.

Graphical Abstract

The Effect of Steviol Glycosides on Sensory Properties and Acceptability of Ice Cream

There has been a challenge in overcoming the bitter aftertaste of stevia, a natural non-caloric sweetener. Recent research focuses on investigating various types of steviol glycosides, the sweet compounds in stevia leaves, as they exhibit different sensory characteristics. This study determined the sensory properties and acceptability of ice cream sweetened solely with three steviol glycosides, rebaudioside (Reb) A, D, and M (0.09% w/v), using sucrose-sweetened ice cream as a control (14% w/v). Ice cream consumers (n = 92) rated their overall liking, attribute liking, and sweetness and bitterness intensities and described the aftertastes of each sample using check-all-that-apply. The liking scores of Reb D- and M-sweetened ice creams were significantly higher than those of Reb A-sweetened ice cream. Among the three glycosides, only Reb M showed a sweetness intensity comparable with that of sucrose. Consumers perceived the aftertastes of Reb D and M ice creams as being more sweet, pleasant, creamy, and milky, while Reb A was more artificial and chemical. Reb D and M ice creams were also plotted close to sucrose in the correspondence analysis graph, meaning that their aftertaste characteristics were similar to those of sucrose. The present study clearly highlights that Reb D and M have better tastes and provide better perceptions to consumers than Reb A, which is the most widely used glycoside in food industry.

Enhancement of Rebaudioside M Production by Structure-Guided Engineering of Glycosyltransferase UGT76G1

Owing to zero-calorie and advanced organoleptic properties similar to sucrose, the plant-derived rebaudioside M (Reb M) has been considered as a next generation sweetener. However, a low content of Reb M in Stevia rebaudiana Bertoni and low enzymatic activity of UGT76G1, which is an uridine diphosphate glucose (UDPG)-dependent glycosyltransferase with the ability to glycosylate rebaudioside D (Reb D) to produce Reb M through the formation of β-1,3 glycosidic bond, restrict its commercial usage. To improve the catalytic activity of UGT76G1, a variant UGT76G1-T284S/M88L/L200A was obtained by structure-guided evolution, whose catalytic activity toward Reb D increased by 2.38 times compared with UGT76G1-T284S. This allowed us to prepare Reb M on a large-scale with a great yield of 90.50%. Moreover, molecular dynamics simulation illustrated that UGT76G1-T284S/M88L/L200A reduced distances from Reb D to catalytic residues and UDPG. Hence, we report an efficient method for the potential scale production of Reb M in this study.

Sweetness profiles of glycosyl rebaudioside A and binary mixtures with sugar alcohols in aqueous solution and a lemonade model system

BACKGROUND

The demands for better-tasting alternative sweeteners have driven efforts to improve the sensory properties of rebaudioside A (Reb-A), such as glycosylation and blending with bulk sweeteners. This study attempted to (i) investigate the sensory profiles of a novel sweetener, glycosyl rebaudioside A (gReb-A), and its 1:1 mixtures with erythritol or maltitol, and (ii) compare between the sensory characteristics in an aqueous solution and lemonade.

RESULTS

The concentrations of the sweeteners were prepared to match the sweetness intensity of a 7% (w/v) sucrose solution using relative sweetness values determined using the two-alternative forced-choice test. Eight trained panelists identified sensory profiles of the sweeteners in an aqueous solution and lemonade using a descriptive analysis protocol. gReb-A had significantly less bitterness and lingering sweetness than Reb-A did, eliciting a sensory profile similar to that of sucrose. The mixture of gReb-A and erythritol was not sensorially differentiated from the sucrose in the aqueous solution. Blending with maltitol significantly enhanced the sweetness and suppressed the bitterness of gReb-A. gReb-A and its binary mixtures were perceived as more similar to sucrose in the lemonade than in solution.

CONCLUSION

This study suggests that glycosylation and blending with erythritol and maltitol gave a more sucrose-like sweetness profile in the aqueous solution and lemonade. The results of the study can be used to develop adequate sugar substitutes for acidic beverages. © 2021 Society of Chemical Industry.

Metabolic engineering for the synthesis of steviol glycosides: current status and future prospects

With the pursuit of natural non-calorie sweeteners, steviol glycosides (SGs) have become one of the most popular natural sweeteners in the market. The SGs in Stevia are a mixture of SGs synthesized from steviol (a terpenoid). SGs are diterpenoids. Different SGs depend on the number and position of sugar groups on the core steviol backbone. This diversity comes from the processing of glycoside steviol by various glycosyltransferases. Due to the differences in glycosylation, each SG has unique sensory properties. At present, it is more complicated to extract high-quality SGs from plants, so the excavation of the metabolic pathways of engineered microorganisms to synthesize SGs has been extensively studied. Specifically, the expression of different glycosyltransferases in microbes is key to the synthesis of various SGs by engineered microorganisms. To trigger more researches on the functional characterization of the enzymes encoded by these genes, this review describes the latest research progresses of the related enzymes involved in SG biosynthesis and metabolic engineering.Key points• Outlines the research progress of key enzymes in the biosynthetic pathway of SGs• Factors affecting the catalytic capacity of stevia glucosyltransferase• Provide guidance for the efficient synthesis of SGs in microbial cell factories.

Process Simulation and Techno-Economic Analysis of Large-Scale Bioproduction of Sweet Protein Thaumatin II

There are currently worldwide efforts to reduce sugar intake due to the various adverse health effects linked with the overconsumption of sugars. Artificial sweeteners have been used as an alternative to nutritive sugars in numerous applications; however, their long-term effects on human health remain controversial. This led to a shift in consumer preference towards non-caloric sweeteners from natural sources. Thaumatins are a class of intensely sweet proteins found in arils of the fruits of the West-African plant Thaumatococcus daniellii. Thaumatins' current production method through aqueous extraction from this plant and uncertainty of the harvest from tropical rainforests limits its supply while the demand is increasing. Despite successful recombinant expression of the protein in several organisms, no large-scale bioproduction facilities exist. We present preliminary process design, process simulation, and economic analysis for a large-scale (50 metric tons/year) production of a thaumatin II variant using several different molecular farming platforms.

Effects of gastrointestinal delivery of non-caloric tastants on energy intake: a systematic review and meta-analysis

Purpose

Taste receptors are expressed throughout the gastrointestinal tract. The activation of post-oral taste receptors using tastants could provide a non-invasive treatment option in combating the obesity epidemic. The aim of this review was to examine the effect of post-oral delivery of non-caloric tastants on eating behavior reflected by primary outcome energy intake and secondary outcomes GI symptoms and perceptions and potential underlying mechanisms. This review was conducted according to the PRISMA guidelines for systematic reviews.

Methods

A systematic literature search of the Cochrane, PubMed, Embase, and Medline databases was performed. This systematic review and meta-analysis was registered in the PROSPERO database on 26 February 2020 (ID: CRD42020171182). Two researchers independently screened 11,912 articles and extracted information from 19 articles. If at least two studies investigated the effect of the same taste compound on primary outcome energy intake, a meta-analysis was performed to determine pooled effect sizes.

Results

Nineteen papers including healthy volunteers were included. In the 19 papers analyzed, effects of various tastants were investigated in healthy volunteers. Most extensively investigated were bitter tastants. The meta-analysis of effects of bitter tastants showed a significant reduction in energy intake of 54.62 kcal (95% CI − 78.54 to − 30.69, p = 0.0014).

Conclusions

Bitter stimuli are most potent to influence eating behavior. Energy intake decreased after post-oral delivery of bitter tastants. This highlights the potential of a preventive role of bitter tastants in battling the obesity epidemic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02485-4.

Bioconversion of Stevioside to Rebaudioside E Using Glycosyltransferase UGTSL2

Rebaudioside E, one of the minor components of steviol glycosides, was first isolated and identified from Stevia rebaudiana in 1977. It is a high-intensity sweetener that tastes about 150-200 times sweeter than sucrose and is also a precursor for biosynthesis of rebaudioside D and rebaudioside M, the next-generation Stevia sweeteners. In this work, new unknown steviol glycosides were enzymatically synthesized from stevioside by coupling UDP-glucosyltransferase UGTSL2 from Solanum lycopersicum and sucrose synthase StSUS1 from Solanum tuberosum. Rebaudioside E was speculated to be the main product of glucosylation of the Glc(β1→C-19) residue of stevioside along with the formation of a (β1→2) linkage based on the analysis of the regioselectivity and stereoselectivity of UGTSL2, and verified afterwards by LC-MS/MS with standard. In a 20-ml bioconversion reaction of 20 g/l stevioside by UGTSL2 and StSUS1, 15.92 g/l rebaudioside E was produced for 24 h.