Sweet Sensor Research Articles

Chemosensoric approaches for taste and odor characteristics each broccoli floret by different storage conditions analyzed using electronic sensors.

This study was to identify taste and volatile characteristics in broccoli florets under various storage conditions (room and cold temperatures). Electronic tongue (E-tongue) analysis revealed that the differences were not represented obviously according to the storage temperatures. The sourness sensor (SRS) was the highest in the 2nd week, and the saltiness sensor (STS) was the highest in the 1st week. The umami (UMS) and bitterness sensors (BRS) were the highest in the 3rd week, and the sweetness sensor (SWS) was the highest in the initial sample. Clusters were discriminated according to storage periods, regardless of storage temperature. Electronic nose (E-nose) analysis detected a total of 41 and 35 volatiles during the room and cold temperature storages, respectively. Clusters were discriminated according to storage types. These findings provide valuable data for broccoli flavor quality by different storage types.

Elucidation of Response Mechanism of a Potentiometric Sweetness Sensor with a Lipid/Polymer Membrane for Uncharged Sweeteners

Nowadays, the utilization of a taste sensor with lipid/polymer membranes is one of the most accurate and objective ways to evaluate the tastes of solutions. However, it has been difficult to evaluate uncharged sweet substances, such as sucrose, because the conventional taste sensor uses the potentiometric measurement, which is mainly based on changes in the surface electric charge density of the membrane. Previous studies have reported that a sweetness sensor called GL1 can evaluate the sweetness of sugars and sugar alcohols, and is commercially available for food, beverage, and pharmaceutical industries. However, the response mechanism of GL1 has not been fully elucidated. In this study, we focus on clarifying the effect of concentrations and types of metal ions in the conditioning solution on the response mechanism of the sweetness sensor GL1. Moreover, according to the different concentrations and types of metal ions in conditioning solutions, the complex formation and the hydrated radius were considered to influence the membrane potential measured in a reference solution and the sensor responses. The purpose of this study is to elucidate the response mechanism and improve the selectivity and sensitivity of the sweetness sensor.

A machine learning-based on-demand sweat glucose reporting platform

Diabetes is a chronic endocrine disease that occurs due to an imbalance in glucose levels and altering carbohydrate metabolism. It is a leading cause of morbidity, resulting in a reduced quality of life even in developed societies, primarily affected by a sedentary lifestyle and often leading to mortality. Keeping track of blood glucose levels noninvasively has been made possible due to diverse breakthroughs in wearable sensor technology coupled with holistic digital healthcare. Efficient glucose management has been revolutionized by the development of continuous glucose monitoring sensors and wearable, non/minimally invasive devices that measure glucose concentration by exploiting different physical principles, e.g., glucose oxidase, fluorescence, or skin dielectric properties, and provide real-time measurements every 1–5 min. This paper presents a highly novel and completely non-invasive sweat sensor platform technology that can measure and report glucose concentrations from passively expressed human eccrine sweat using electrochemical impedance spectroscopy and affinity capture probe functionalized sensor surfaces. The sensor samples 1–5 µL of sweat from the wearer every 1–5 min and reports sweat glucose from a machine learning algorithm that samples the analytical reference values from the electrochemical sweat sensor. These values are then converted to continuous time-varying signals using the interpolation methodology. Supervised machine learning, the decision tree regression algorithm, shows the goodness of fit R2 of 0.94 was achieved with an RMSE value of 0.1 mg/dL. The output of the model was tested on three human subject datasets. The results were able to capture the glucose progression trend correctly. Sweet sensor platform technology demonstrates a dynamic response over the physiological sweat glucose range of 1–4 mg/dL measured from 3 human subjects. The technology described in the manuscript shows promise for real-time biomarkers such as glucose reporting from passively expressed human eccrine sweat.

Quantification of bitterness of coffee in the presence of high-potency sweeteners using taste sensors

Electronic tongues have been identified as useful tools for quantifying the taste of food and beverages. However, the bitterness evaluation of coffee in the presence of high-potency sweeteners has not been performed yet. In this study, we investigated an approach to quantify the bitterness of coffee with different roasting degrees and the sweetness of acesulfame potassium (Ace K) added to the coffee using taste sensors with lipid polymer membranes. A formula for predicting coffee bitterness with the addition of Ace K was proposed using the responses of a bitterness sensor and a sweetness sensor. We found that the predicted coffee bitterness showed a good correlation with human taste.

A Quantitative Method for Acesulfame K Using the Taste Sensor.

We have developed a method to quantify the sweetness of negatively charged high-potency sweeteners coexisting with other taste substances. This kind of sweetness sensor uses lipid polymer membranes as the taste-sensing part. Two types of outputs have been defined in the measurement of the taste sensor: one is the relative value and the other is the CPA (the change in membrane potential caused by adsorption) value. The CPA value shows a good selectivity for high-potency sweeteners. On the other hand, the relative value is several times higher than the CPA value, but the relative value is influenced by salty substances. In order to obtain both high sensitivity and selectivity, we established a model for predicting the concentration of sweeteners with a nonlinear regression analysis method using the relative values of both the sweetness sensor and the saltiness sensor. The analysis results showed good correlations with the estimated concentration of acesulfame potassium coexisting with salty substances, as represented by R2 = 0.99. This model can correspond well to the prediction of acesulfame K in a concentration of 0.2–0.7 mM, which is commonly used in food and beverages. The results obtained in this paper suggest that this method is useful for the evaluation of acesulfame K using the taste sensors.

Sweet Sensor for the Detection of Aflatoxin M1 in Whole Milk.

Recently, there is an increase in interest to develop user-friendly monitoring devices in healthcare, environmental, and agrofood fields for a fast detection of contaminants. Aflatoxins (AFs) are a group of toxic substances produced by the fungi of species Aspergillus that contaminate cereals and dried fruits. When dairy cows ingest feed contaminated with aflatoxin B1 (AFB1), it is metabolized and transformed in the liver into a carcinogenic form aflatoxin M1 (AFM1), which is eliminated through the milk. In this work, we developed a sensor assay to detect low amounts of AFM1 directly in whole milk. For this purpose, we produced monospecific polyclonal antibody (IgGMS-M1) that was able to bind with high avidity to AFM1. Then, we conjugated the antibody to the invertase enzyme from Saccharomyces cerevisiae. This enzyme is able to convert sucrose into fructose and glucose. After incubation of invertase-conjugated anti-AFM1 antibody with milk containing AFM1, we measured the produced glucose by a glucometer. The produced glucose was then correlated to the amount of AFM1 present in the milk. The obtained results show that the assay is easily customizable as a portable instrument for on-site AFM1 measurements. In addition, the results point out that the assay is very sensitive since it can detect the presence of 27 parts per trillion (ppt) of AFM1 in whole milk, a value lower than the AFM1 quantities in milk and dairy products set by the European Commission (50 ppt).

Development of Lipid/Polymer Membrane by Reduced Graphene Oxide for Sugar Sensor

The sweetness sensor has been developed for sensing sweeteners using lipid/polymer membrane as ion selective membrane in potentiometry measurement. In this work, effects of blending reduce graphene oxide (rGO) at 1.25, 2.5 and 3.75 wt.% during conventional lipid/polymer membrane preparation to increase electrical responsive was investigated. The results demonstrated that the lipid/polymer/rGO-3.75% membrane has the highest response, which was 13.06 and 18.21 % increment (at 0.1 M and 0.3 M of sucrose, respectively) from the conventional lipid/polymer membrane.

Quantitative prediction of bitterness masking effect of high-potency sweeteners using taste sensor

A taste sensor based on lipid/polymer membranes has been reported being possible to detect the masking of bitter substances or masking on bitterness receptors (physical masking or biochemical masking). However, it was difficult to express the bitterness suppression by sweeteners, which is decided by the balance of substances produced in human’s brain (functional masking). High-potency sweeteners are one of the sweeteners used for bitterness-masking in food and pharmaceutical industry. The objective of this study is to evaluate the bitterness-masking effect of high-potency sweeteners using the taste sensor. A bitterness sensor was used to evaluate the bitterness of quinine hydrochloride, and sweetness sensors for high-potency sweeteners were used to evaluate the sweetness of aspartame and saccharine sodium. The sensory evaluation was also carried out to examine the bitterness suppression effect of high-potency sweeteners. The bitterness-prediction formulas were proposed with the aid of a model regression analysis using two outputs from the bitterness sensor and the sweetness sensor for high-potency sweeteners. As a result, the predicted bitterness showed a good correlation with the human taste when aspartame or saccharine sodium was added to quinine hydrochloride. Thus, this study provided an effective method to evaluate the bitterness suppressed by high-potency sweeteners.

Taste cell-expressed α-glucosidase enzymes contribute to gustatory responses to disaccharides

The primary sweet sensor in mammalian taste cells for sugars and noncaloric sweeteners is the heteromeric combination of type 1 taste receptors 2 and 3 (T1R2+T1R3, encoded by Tas1r2 and Tas1r3 genes). However, in the absence of T1R2+T1R3 (e.g., in Tas1r3 KO mice), animals still respond to sugars, arguing for the presence of T1R-independent detection mechanism(s). Our previous findings that several glucose transporters (GLUTs), sodium glucose cotransporter 1 (SGLT1), and the ATP-gated K(+) (KATP) metabolic sensor are preferentially expressed in the same taste cells with T1R3 provides a potential explanation for the T1R-independent detection of sugars: sweet-responsive taste cells that respond to sugars and sweeteners may contain a T1R-dependent (T1R2+T1R3) sweet-sensing pathway for detecting sugars and noncaloric sweeteners, as well as a T1R-independent (GLUTs, SGLT1, KATP) pathway for detecting monosaccharides. However, the T1R-independent pathway would not explain responses to disaccharide and oligomeric sugars, such as sucrose, maltose, and maltotriose, which are not substrates for GLUTs or SGLT1. Using RT-PCR, quantitative PCR, in situ hybridization, and immunohistochemistry, we found that taste cells express multiple α-glycosidases (e.g., amylase and neutral α glucosidase C) and so-called intestinal "brush border" disaccharide-hydrolyzing enzymes (e.g., maltase-glucoamylase and sucrase-isomaltase). Treating the tongue with inhibitors of disaccharidases specifically decreased gustatory nerve responses to disaccharides, but not to monosaccharides or noncaloric sweeteners, indicating that lingual disaccharidases are functional. These taste cell-expressed enzymes may locally break down dietary disaccharides and starch hydrolysis products into monosaccharides that could serve as substrates for the T1R-independent sugar sensing pathways.

Role of the sweet taste receptor in glucose metabolism: no sweets for diabetes?

Type 2 diabetes is closely associated with our daily diets and has become a global health problem with increasing number of patients. Maintaining energy homeostasis is essentially required for the treatment of diabetes. Energy metabolism starts with taking in a meal. Nutrients including amino acids, fatty acids and glucose in the digest have been shown to act on the neuroendocrine cells in the gastrointestinal (GI) tract, and thereby play important roles in energy homeostasis. Therefore, the GI tract is now recognized as a sensor system for nutrient signals. Taste receptor type 1 member 2 (T1R2) is known to function as a co-receptor with T1R3 to detect sweet chemicals in the taste buds. It has been proposed that the T1R2/T1R3 receptor complex acts as sweet sensor in the intestine, and plays a pivotal role in sensing sugars and maintaining glucose homeostasis through incretin secretion. To clarify the physiological roles of T1R2 in glucose homeostasis, T1r2-lacZ knock-in/knock-out mice were generated. We found lacZ gene expression in the GI tract where T1r3 expression has been reported. Interestingly, the T1r2-lacZ knock-in mice showed impaired glucose tolerance on oral glucose challenge but not on intraperitoneal injection. However, the fasting glucose level in T1r2-lacZ knock-in mice was comparable to that in wild type mice. These results suggest an important role of the sweet taste receptor system in the intestine when stimulated by glucose. Therefore, the roles of T1R2 will be presented and the mechanism for metabolic homeostasis will be discussed.

甘味センサの開発に関するレビュー

甘味センサの開発に関するレビュー

Development and Investigation of a Sweetness Sensor for Sugars -Effect of Lipids-

Development and Investigation of a Sweetness Sensor for Sugars -Effect of Lipids-

Development of sweetness sensor with selectivity to negatively charged high-potency sweeteners

Objectivetaste evaluation has been much in demand in the food, beverage and pharmaceutical industries. A taste-sensing system, which is an electronic tongue with “global selectivity,” is one of the methods used for objective taste evaluation. A taste sensor electrode responds to only one of the basic tastes (saltiness, sourness, sweetness, bitterness and umami) as a change in membrane potential caused by interactions with tastants. Sweet substances are compounds with diverse chemical structures and sizes. Since the taste-sensing system is a potentiometric measurement system using a change in membrane potential, three types of sweetness sensors are required, one for sweeteners with each type of electric charge (uncharged, positively charged and negatively charged). A sweetness sensor for uncharged sweeteners has been developed. Therefore, negatively charged sweeteners, such as saccharine sodium and acesulfame potassium, were chosen as the target substances in this study. We investigated the responses of various sensor membranes using a lipid and nine kinds of plasticizers to each basic taste sample. Furthermore, not only the selectivity of the membranes but also the concentration dependence of their response to sweeteners was investigated. As a result, one of the developed sensors showed responses of over 20mV to 5mM saccharine sodium and 10mM acesulfame potassium in CPA value measurement (CPA: change in membrane potential caused by adsorption). On the other hand, the sensor also showed nearly zero responses to other basic taste samples. In addition, saltiness was the only interfering taste, and the responses to target substances in relative value measurement were over 140mV. The developed sweetness sensor had high selectivity and concentration-dependent responses. Hence, we concluded that the sensor is suitable for use as a sweetness sensor for high-potency sweeteners with a negative electric charge.

Development of a sweetness sensor for aspartame, a positively charged high-potency sweetener.

Taste evaluation technology has been developed by several methods, such as sensory tests, electronic tongues and a taste sensor based on lipid/polymer membranes. In particular, the taste sensor can individually quantify five basic tastes without multivariate analysis. However, it has proven difficult to develop a sweetness sensor, because sweeteners are classified into three types according to the electric charges in an aqueous solution; that is, no charge, negative charge and positive charge. Using membrane potential measurements, the taste-sensing system needs three types of sensor membrane for each electric charge type of sweetener. Since the commercially available sweetness sensor was only intended for uncharged sweeteners, a sweetness sensor for positively charged high-potency sweeteners such as aspartame was developed in this study. Using a lipid and plasticizers, we fabricated various lipid/polymer membranes for the sweetness sensor to identify the suitable components of the sensor membranes. As a result, one of the developed sensors showed responses of more than 20 mV to 10 mM aspartame and less than 5 mV to any other taste. The responses of the sensor depended on the concentration of aspartame. These results suggested that the developed sweetness sensor had high sensitivity to and high selectivity for aspartame.

Sweetness Sensor with Lipid/Polymer Membranes: Sweet-Responsive Substances

A sweetness sensor with lipid/polymer membranes has been developed for evaluating the sweetness of sugars and sugar alcohols. Among the constituents of lipid/polymer membranes, gallic acid has been used as the main substance involved in sucrose response in our group. In this study, as a step toward understanding the response mechanism of the sweetness sensor, functional groups of gallic acid, namely, carboxyl and hydroxyl groups, were focused on. The results demonstrated that the carboxyl group is essential for the sweetness sensor, whereas the hydroxyl group is not always necessary for the sucrose response. It was also revealed that the phosphate group may be a substitute for the carboxyl group. Then, for one of the sensors with the highest response to a 300 mM sucrose solution, named the sweetness sensor GL1, the basic characteristics such as selectivity and correlation with sweetness were investigated. The behavior of GL1 sensor outputs was relatively similar to the sweetness perception in humans.

Sweetness Sensor with Lipid/Polymer Membranes: Response to Various Sugars

A sweetness sensor with lipid/polymer membranes has been developed for evaluating the sweetness of sugars and sugar alcohols. In this paper, experiments were performed to compare the electric responses of the sweetness sensor with the chemical structure of various sugars. The results demonstrated that the presence of two adjacent hydroxyl groups in a sugar molecule is important and that the optimum distance between the two adjacent hydroxyl groups is approximately 3 A. The interaction between the sweetness sensor and sugars is discussed.

Sweet sensor for amino acid

Sweet sensor for amino acid

Integrated Oligoaniline‐Cross‐Linked Composites of Au Nanoparticles/Glucose Oxidase Electrodes: A Generic Paradigm for Electrically Contacted Enzyme Systems

Sweet sensor: A bis-aniline-cross-linked Au nanoparticles (NPs)/glucose oxidase composite has been electropolymerized on a Au electrode (see picture). The integrated Au NPs/enzyme electrode provides an effective matrix for making electrical contact with the enzyme, and this yields a specific amperometric glucose biosensor.Electropolymerizable glucose oxidase (GOx) was synthesized by the tethering of thioaniline units to the protein. The electropolymerization of the thioaniline-modified GOx in the presence of thioaniline-functionalized Au nanoparticles (NPs) yielded a three-dimensional bis-aniline-cross-linked Au NPs/GOx network. The bis-aniline bridging units are redox active and mediate the electron transfer between the enzyme redox sites and the electrode, and the Au NPs provide the three-dimensional conductivity for transporting the electrons to the electrode. The covalently linked GOx displays an effective electrical contact with the electrode (turnover rate of ca. 500 s(-1)), which results in a sensitive and selective glucose-sensing electrode. The preparation of the electrode by means of electropolymerization, and the bioelectrocatalytic features of the electrode, suggest its feasibility as a miniaturized electrode with a sensing matrix and as an implantable glucose sensor in future applications.

A Sweet Sensor for Size-Conscious Bacteria

Bacteria, like eukaryotic cells, regulate their size by coordinating cell growth and division, growing faster and becoming larger when nutrients are more plentiful. Weart et al. (2007) now identify an enzyme in a glucolipid pathway that inhibits assembly of the key cell division protein FtsZ, but only during high nutrient conditions. Delaying cell division during rapid growth allows bacterial cells to become larger.

Sweet Sensor, Surprising Partners

Hexokinase1 (HXK1) is an evolutionarily conserved glucose sensor in plants. However, the molecular mechanism through which HXK1 controls the expression of genes encoding proteins involved in photosynthesis is a mystery. Recent research demonstrates that a previously unknown HXK1 nuclear complex controls the expression of specific photosynthetic genes, a process that is independent of glucose metabolism but requires two unexpected partners, VHA-B1 and RPT5B. Both VHA-B1 and RPT5B have well-established and conserved functions in processes that are seemingly unrelated to glucose-dependent regulation of gene expression, and neither of them is a predominantly nuclear protein. Biochemical, genetic, and molecular evidence demonstrates that VHA-B1 and RPT5B directly interact with HXK1 in the nucleus and that the HXK1 complex binds to the cis-acting elements of chlorophyll a/b binding protein 2, a photosynthetic gene that is transcriptionally suppressed by glucose. The identification of the HXK1 nuclear complex reveals an unexpected glucose-signaling mechanism and reinforces the notion that metabolic enzymes can play unique roles in signal transduction by directly controlling gene expression in the nucleus.