Sodium Chloride Suppresses Vegetable Bitterness Only When Plain Vegetables Are Perceived as Highly Bitter

Application of a salt substitute in bitter taste suppression and toward better acceptance of cruciferous vegetables in diet

The addition of table salt has been reported to enable better acceptance when consuming the least preferred vegetables belonging to the Cruciferae family. Considering the adverse effect of excessive table salt intake on incidence of hypertension and cardiovascular diseases, it is essential to explore an alternative healthier option for better acceptance and to encourage consumption of these vegetables. In this study, 261 adult participants were evaluated for their preferences toward basic tastes and food as well as sensory evaluation of a meal prepared from cruciferous vegetables with the addition of two different salts, sodium chloride and salt substitute containing a blend of potassium and sodium salts. A general questionnaire was used to assess taste and food preferences, while the Cruciferous Vegetable Food Frequency Questionnaire (CVFFQ) was used for vegetable intake assessment. The Labeled Magnitude Scale (LMS), Just About Right (JAR) scale, and several hedonic scales were used to determine taster status and sensory evaluation. The results show that a low concentration of the salt substitute did not impact bitterness suppression but did result in higher preference of the cruciferous vegetable meal. Although, subjects self-reported to have salty taste preferences were more sensitive to bitter taste, they did not perceive samples as less salty and less acceptable than subjects with lower sensitivity. The results show the necessity for further examination of the effectiveness of different concentrations of the assessed salt substitute in suppressing perceived bitterness of cruciferous vegetables and regarding their overall acceptance for inclusion in diets.

Factors related to sensory properties and consumer acceptance of vegetables

Many consumers perceive the bitter taste or other sensory characteristic of vegetables as unpleasant, posing a challenge to dietary recommendations aiming to increase vegetable consumption. Food experience is multisensory, with complex interactions between the senses and individual differences in sensory perception. This review focuses on the factors affecting sensory properties of vegetables and sensory perception of vegetables among adults. Topical examples of sensory quality and evaluation of vegetable samples are presented. Cultivar and growing conditions are related to the internal sensory quality of vegetables. The effects of different processing methods, such as freezing and cooking, on the sensory properties of vegetables are also reviewed. Flavor modification of vegetables with seasonings may be used to improve palatability and incorporating vegetables to meals may increase the intake of vegetables. Recently, external factors (e.g. visual and odor stimuli) have been tested in multisensory research in the context of vegetable perception and choice. These options to achieve better sensory quality, more palatable meals and pleasant eating context may be used to promote vegetable intake among adults.

Sodium, but not potassium, blocks bitterness in simple model chicken broths

Potassium chloride (KCl) has proven useful as a salty taste replacer to help reduce dietary sodium. But unlike sodium, which in simple aqueous solutions blocks the perception of bitterness of selected compounds, KCl does not blocker bitterness. We tested the ability of potassium to block bitterness in a more complex translational system by presenting model chicken broths to healthy adults. Broths were presented in three added salt conditions: (1) no added salt, (2) salted with sodium chloride (NaCl), or (3) salted with KCl. To create a model bitter off-taste, four concentrations of l-tryptophan (l-tryp, present in chicken meat) were added to each broth. In Experiment 1, the base broth consisted of chicken flavor only. In Experiment 2, the base broth was more complex, containing savory (umami) ingredients. In both experiments, subjects rated broths with either added NaCl or KCl as saltier than unsalted broths. Only NaCl, however, suppressed bitterness (by about 30%, across a wide range of l-tryp concentrations). Accordingly, when complex foods have sodium reduced and potassium increased to balance salty taste, the bitterness reducing properties of sodium will need to be replaced independently, since potassium does not share this effect.

Hen protein-derived peptides as the blockers of human bitter taste receptors T2R4, T2R7 and T2R14

Bitter sensation is mediated by various bitter taste receptors (T2Rs), thus T2R antagonists are actively explored. Our objective was to look for novel T2R blockers in hen protein hydrolysate (HPH). We screened the least bitter HPH fractions using electronic tongue, and analyzed their peptide sequences and calcium mobilization in HEK293T cells expressing T2Rs. The results showed that the HPH fractions with higher bitterness intensity had higher hydrophobicity, more hydrophobic amino acids, and more positively charged peptides, but fewer known umami peptides. The peptide fractions from the least bitter HPH fraction significantly inhibited quinine bitterness (P < 0.05), and also significantly inhibited quinine- or diphenhydramine-dependent calcium mobilization of HEK293T cells expressing human T2R4, T2R7, or T2R14 (P < 0.05). Among them, the first eluted (least bitter) peptide fraction showed the strongest bitter-inhibitory effect. In conclusion, HPH peptides are the blockers of T2R4, T2R7, and T2R14.

Sodium Chloride Suppresses the Bitterness of Protein Hydrolysates by Decreasing Hydrophobic Interactions

The formation of bitter off-flavor is a long-existing issue during food protein hydrolysis. The aim of this study is to determine the mechanism of sodium chloride (NaCl) suppressing the bitterness of protein hydrolysates. In this study, the bitterness of egg white hydrolysate (EWH) and hen meat hydrolysate (HPH) was determined using an electronic tongue. The results showed that the bitterness intensity of quinine hydrochloride, EWH, and HPH was suppressed significantly by NaCl in a concentration-dependent manner (P < 0.05). The particle sizes, turbidity, zeta potentials, and surface hydrophobicity of EWH and HPH were also significantly decreased by NaCl at concentrations of 0.05, 0.1, 0.3, and 0.5 M (P < 0.05). These results indicated that adding NaCl at certain concentrations led to a salting-in effect, burying hydrophobic groups and decreasing the surface hydrophobicity of peptides, resulting in the decrease of bitterness. Using NaCl is an alternative, effective, and cheap strategy to suppress protein hydrolysate bitterness by decreasing hydrophobic interactions in food industry. PRACTICAL APPLICATION: NaCl can be used as an effective bitterness masker for food protein hydrolysates by decreasing hydrophobic interactions of peptides.

Evaluation of the Bitterness-Masking Effect of Powdered Roasted Soybeans

The masking of bitterness is considered important because many pharmaceutical compounds have a bitter taste. The bitterness-masking effect of powdered roasted soybeans (PRS) was investigated using a bitter taste sensor. PRS was revealed to significantly suppress the bitterness of quinine hydrochloride and denatonium benzoate. Furthermore, the bitterness-masking mechanism of PRS extracts was evaluated using dynamic light scattering. These results showed that the extracted suspension consisted of particles that were several hundreds of nanometers in size. Analysis of the PRS extracts by nuclear magnetic resonance spectroscopy indicated that denatonium benzoate was entrapped in the PRS extracts. Thus, PRS may be useful as a bitterness-masking agent in orally administered pharmaceuticals.

Long-Chain Fatty Acids Elicit a Bitterness-Masking Effect on Quinine and Other Nitrogenous Bitter Substances by Formation of Insoluble Binary Complexes

We have previously found that fatty acids can mask the bitterness of certain nitrogenous substances through direct molecular interactions. Using isothermal titration calorimetry, we investigated the interactions between sodium oleate and 22 bitter substances. The hydrochloride salts of quinine, promethazine, and propranolol interacted strongly with fatty acids containing 12 or more carbon atoms. The (1)H NMR spectra of these substances, obtained in the presence of the sodium salts of the fatty acids in dimethyl sulfoxide, revealed the formation of hydrogen bonds between the nitrogen atoms of the bitter substances and the carboxyl groups of the fatty acids. When sodium laurate and the hydrochloride salt of quinine were mixed in water, an equimolar complex formed as insoluble heterogeneous needlelike crystals. These results suggested that fatty acids interact directly with bitter substances through hydrogen bonds and hydrophobic interactions to form insoluble binary complexes that mask bitterness.