A new sensory sweetness definition and sweetness conversion method of five natural sugars, based on the Weber-Fechner Law

Sour taste perception in fluids: The impact of sweet tastant, fluid viscosity, and individual salivary properties

Binary taste perception is widely studied in aqueous solutions but less investigated in non-Newtonian fluid systems. In this study, the effect of sweet tastants on the dynamic sour taste perception in thickened fluids and its underpinning oral processing factors were investigated. Subjects were tested for taste thresholds and salivary biochemical properties. By using hydroxypropyl methylcellulose (HPMC) as a thickening agent, subjects conducted sour taste evaluation, with and without maltose and/or HPMC, using descriptive sensory analyses. A simulated fluid shear elicited by fixed-frequency mastication was applied on thickened fluid sample oral processing during time-intensity sour taste evaluation. Results showed that adding maltose to fluid samples enhanced sour taste perception, and increasing fluid viscosity generally suppressed perceived maximum sour taste. Moreover, subjects with lower sour taste sensitivity and higher salivary buffering capacity reported overall lower sour taste intensity in most samples, validating the hypothesis that salivary properties importantly affect sour taste perception.

Protein digestibility and techno-functional performance of milk-alternative prototypes based on combinations of lentil and cereal protein

Lentil protein isolate was combined with proteins from oat, rice, brewer's spent grain (BSGP) and wheat to achieve plant-based milk alternatives (PBMA) with improved protein quality and functionality. Due to the complementary amino acid (AA) profile of pulse protein which is high in lysine, and cereal protein which is high in sulphur amino acids, their combination at an optimised ratio resulted in a protein blend with a significantly improved indispensable amino acid score (IAAS) compared to the single ingredients. All protein combinations with lentil except for wheat resulted in a full IAAS for adults. The in vitro protein digestibility was assessed using the static INFOGEST digestion model to calculate the proxy in vitro DIAAS (PIVDIAAS) of the emulsions. Techno-functional properties such as particle size, rheological behaviour and physical stability were investigated. The PIVDIAAS of the combined protein emulsions was found to be 0.72, 0.78, 0.83, 0.98 for lentil + wheat, lentil + oat, lentil + BSGP and lentil + rice emulsions, respectively, compared to 0.48, 0.25, 0.5, 0.67 and 0.81 determined for the emulsions based on lentil, wheat, oat, BSGP and rice alone, respectively. The emulsions based on the combination of lentil and cereal protein also showed improved physical stability regarding sedimentation and creaming, and a higher whiteness index of the emulsions. It could be shown that the combination of lentil and cereal protein is a promising strategy to achieve PBMAs with improved protein quality and techno-functionality.

Comparative analysis of physical traits, mineral compositions, antioxidant contents, and metabolite profiles in five cherry tomato cultivars

Cherry tomatoes (Solanum lycopersicum var. cerasiforme) are cultivated and consumed worldwide. While numerous cultivars have been bred to enhance fruit quality, few studies have comprehensively evaluated the fruit quality of cherry tomato cultivars. In this study, we assessed fruits of five cherry tomato cultivars (Qianxi, Fengjingling, Fushan88, Yanyu, and Qiyu) at the red ripe stage through detailed analysis of their physical traits, mineral compositions, antioxidant contents, and metabolite profiles. Significant variations were observed among the cultivars in terms of fruit size, shape, firmness, weight, glossiness, and sepal length, with each cultivar displaying unique attributes. Mineral analysis revealed distinct patterns of essential and trace element accumulation, with notable differences in calcium, sodium, manganese, and selenium concentrations. Fenjingling was identified as a selenium enriched cultivar. Analysis of antioxidant contents highlighted Yanyu as particularly rich in vitamin C and Fenjingling as having elevated antioxidant enzyme activities. Metabolomics analysis identified a total number of 3,396 annotated metabolites, and the five cultivars showed distinct metabolomics profiles. Amino acid analysis showed Fushan88 to possess a superior profile, while sweetness and tartness assessments indicated that Yanyu exhibited higher total soluble solids (TSS) and acidity. Notably, red cherry tomato cultivars (Fushan88, Yanyu, and Qiyu) accumulated significantly higher levels of eugenol and α-tomatine, compounds associated with undesirable flavors, compared to pink cultivars (Qianxi and Fengjingling). Taken together, our results provide novel insights into the physical traits, nutritional value, and flavor-associated metabolites of cherry tomatoes, offering knowledge that could be implemented for the breeding, cultivation, and marketing of cherry tomato cultivars.

Selection of a galactose-positive mutant strain of Streptococcus thermophilus and its optimized production as a high-vitality starter culture

Streptococcus thermophilus is a common starter in yogurt production and plays an important role in the dairy industry. In this study, a galactose-positive (Gal+) mutant strain, IMAU20246Y, was produced using the chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine (NTG) from wild-type S. thermophilus IMAU20246, which is known to have good fermentation characteristics. The sugar content of milk fermented by either the mutant or the wild type was determined using HPLC; metabolism of lactose and galactose was significantly increased in the mutant strain. In addition, we used response surface methodology to optimize components of the basic M17 medium for survival ratio of the mutant strain. Under these optimal conditions, the viable counts of mutant S. thermophilus IMAU20246Y reached 4.15 × 108 cfu/mL and, following freeze-drying in the medium, retained cell viability of up to 67.42%. These results are conducive to production of a high-vitality starter culture and development of "low sugar, high sweetness" dairy products.

Chemical composition and antioxidant activity of Polygonatum kingianum processed by the traditional method of "Nine Cycles of Steaming and Sun-Drying"

Polygonatum kingianum Coll. et (Hemsl) is a famous Chinese traditional food and medicine analogous plant. The rhizome of P. kingianum showed a decrease in levels of alkaloids, amino acids and derivatives, terpenoids, and an increase in organic acid and saccharides when it was processed by the traditional method of "Nine Cycles of Steaming and Sun-Drying". The relative content of 341 metabolites were increased (fold change, FC > 2; variable importance in projection, VIP > 1 and P-value, P < 0.05); while 456 metabolites were decreased (FC < 0.5, VIP > 1, and P < 0.05). The changes in chemical components result in a decrease in numb taste and an increase in sweetness. The increased antioxidant activity was observed in the processed samples. Together, this work has advanced the mechanism of reducing numb taste and enhancing antioxidant activity in the resource plants, such as P. kingianum, processed by the traditional method.

Comparison of ancestral and traditional methods for elaborating sparkling wines

This work compares the ancestral method for elaborating sparkling wines with the most widely used traditional method. Ancestral method is a single fermentation procedure in which the fermenting grape must is bottled before the end of alcoholic fermentation whereas traditional method involves a second fermentation of a base wine inside a bottle. Macabeo grapes were used to elaborate a traditional sparkling wine and two ancestral sparkling wines, one with a low yeast population and one with a high yeast population. The findings indicate that ancestral sparkling wines have lower ethanol content and can be elaborated using lower sulphur dioxide levels. In general, ancestral sparkling wines showed similar protein concentration, higher polysaccharide content, similar or better foamability (HM) than the traditional sparkling wine., No differences were found in the foam stability (HS). In addition, the sensory analysis indicated that ancestral sparkling wines have smaller bubble size, lower CO2 aggressivity, they seemed to have longer ageing time and were scored better than the traditional sparkling wine. These results therefore indicate that the ancestral method is of great interest for the elaboration of high-quality sparkling wines.

Naturalistic food categories are driven by subjective estimates rather than objective measures of food qualities

Food-related studies often categorize foods using criteria such as fat and sugar content (e.g., high-fat, high-sugar foods; low-fat, low-sugar foods), and use these categorizations for further analyses. While these criteria are relevant to nutritional health, it is unclear whether they agree with the ways in which we typically group foods. Do these objective categories correspond to our subjective sense? To address this question, we recruited a group of 487 online participants to perform a triplet comparison task involving implicit object similarity judgements on images of 36 foods, which varied in their levels of fat and sugar. We also acquired subjective ratings of other food properties from another set of 369 online participants. Data from the online triplet task was used to generate a similarity matrix of these 36 foods. Principal Components Analysis (PCA) of this matrix identified that the strongest determinant of food similarity (the first PC) was most highly related to participants' judgements of how processed the foods were, while the second component was most related to estimates of sugar and fat content. K-means clustering analysis revealed five emergent food groupings along these PC axes: sweets, fats, starches, fruits, and vegetables. Our results suggest that naturalistic categorizations of food are driven primarily by knowledge of the origin of foods (i.e., grown or manufactured), rather than by their sensory or macronutrient properties. These differences should be considered and explored when developing methods for scientific food studies.

Establishment of a new cell-based assay to quantitatively evaluate the sweetness of sugar and sugar alcohol

Sweetness is a crucial indicator for identifying sweeteners used for flavor regulation and nutritional matching of foods. This study established a new quantitative sweetness evaluation method based on a combination of transiently transfected sweet taste receptor cells (STRs) and human sensory evaluation. Here, nine different sweeteners were evaluated and 10 sensory difference intensities and their corresponding concentrations were obtained through sensory evaluation. Using the same concentration solution as in the sensory evaluation, the dosage-response curve and EC50 of the nine sweeteners were obtained by analyzing the intracellular calcium signal fluctuation of STRs. Data analysis revealed that the calcium signal intensity and sweetness intensity under the same concentration of sweetener presented a strong linear correlation (R2 > 0.9). Additionally, we found a favorable correlation (R2 = 0.8746) between the relative sweetness and EC50. These findings indicate that the quantitative evaluation of sweetness based on STRs could be a potential alternative to human sensory evaluation.

Understanding quality differences between kiwifruit varieties during softening

Research into variations between kiwifruit varieties particularly their softening quality during storage is important in improving kiwifruit quality. The potential reasons for ripening quality differences between 'Cuixiang' (CX) and 'Hayward' (HWD) kiwifruit were analyzed by physiology and metabolomic data combined with the random forests learning algorithm. The results showed that the storability difference between the two varieties mainly resulted from differences in polygalacturonase (PG) and β-galactosidase activities. The 1 °C slowed the fruit softening process of both varieties by decreasing their PG activities. A total of 368 metabolites were identified and amino acid, carbohydrate, cofactors and vitamins, as well as nucleotide metabolism are key metabolic modules that affect the ripening differences of CX and HWD kiwifruit. A total of 30 metabolites showed remarkable ability in distinguish the ripening quality of CX and HWD kiwifruit, in which d-glucose, d-maltose, 2-hydroxybutyric acid, phenyllactate, and vitamin B2 were noteworthy for their potential application on the evaluation of kiwifruit taste and nutritional value. These findings provide positive insights into the underlying mechanism of ripening quality differences between CX and HWD kiwifruit and new ideas for identifying key metabolic markers in kiwifruit.

Mineral composition, the profile of phenolic compounds, organic acids, sugar and in vitro antioxidant capacity, and antimicrobial activity of organic extracts of Juniperus drupacea fruits

Juniperus drupacea fruit is widely used in traditional and complementary medicine in Turkey for the treatment of different diseases in various forms such as molasses and tar. This study was carried out to evaluate the phenolic compounds, organic acid, sugar, and macro- and micromineral distributions of methanol and water extracts of J. drupace fruit, as well as their antioxidant and antimicrobial potential. For this purpose, total phenolic content by spectrophotometer, phenolics, organic acids, and sugars distributions by HPLC in extracts of J. drupacea fruits, and macro- and micromineral element content by ICP-AES in fruit were determined. 2,2-diphenyl-l-picrylhydrazyl assay (DPPH assay) was used to evaluate in vitro antioxidant activity in extracts. The antimicrobial potential of J. drupacea fruit methanol extract against some gram-positive and gram-negative pathogenic bacteria was evaluated using disk diffusion and minimum inhibitory concentration (MIC) methods. The potassium macroelement and the iron microelement were found at high content in J. drupacea fruit. The total phenolic content in the methanol extracts was higher than the water extracts. Among the individual phenolic compounds, catechin, a flavonoid that was the highest in both extractions, was determined as 300.49 μg/g in methanol extract and 314.88 μg/g in water extract. DPPH scavenging activity was higher in methanol extracts. While the methanol extract of J. drupacea had no-inhibitory effect on the gram-negative bacteria tested, it exhibited a strong inhibition on the gram-positive bacteria Listeria innocua, Listeria monocytogenes, Staphylococcus carnosus, and Enterococcus faecalis.

A Fechner multiscale local descriptor for face recognition

Inspired by Fechner's law, we propose a Fechner multiscale local descriptor (FMLD) for feature extraction and face recognition. Fechner's law is a well-known law in psychology, which states that a human perception is proportional to the logarithm of the intensity of the corresponding significant differences physical quantity. FMLD uses the significant difference between pixels to simulate the pattern perception of human beings to the changes of surroundings. The first round of feature extraction is performed in two local domains of different sizes to capture the structural features of the facial images, resulting in four facial feature images. In the second round of feature extraction, two binary patterns are used to extract local features on the obtained magnitude and direction feature images, and four corresponding feature maps are output. Finally, all feature maps are fused to form an overall histogram feature. Different from the existing descriptors, the FMLD's magnitude and direction features are not isolated. They are derived from the "perceived intensity", thus there is a close relationship between them, which further facilitates the feature representation. In the experiments, we evaluated the performance of FMLD in multiple face databases and compared it with the leading edge approaches. The results show that the proposed FMLD performs well in recognizing images with illumination, pose, expression and occlusion changes. The results also indicate that the feature images produced by FMLD significantly improve the performance of convolutional neural network (CNN), and the combination of FMLD and CNN exhibits better performance than other advanced descriptors.

Electrochemical and biosensing properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens

We investigated the bioelectrochemical properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens (TvGDH) and its electrochemical behaviour when immobilized on a graphite electrode. TvGDH was recently shown to have an unusual substrate spectrum and to prefer maltose over glucose as substrate, and hence could be of interest as recognition element in a maltose sensor. In this study, we determined the redox potential of TvGDH, which is -0.268 ± 0.007 V vs. SHE, and advantageously low to be used with many redox mediators or redox polymers. The enzyme was entrapped in, and wired by an osmium redox polymer (poly(1-vinylimidazole-co-allylamine)-{[Os(2,2'-bipyridine)₂Cl]Cl}) with formal redox potential of +0.275 V vs. Ag|AgCl via poly(ethylene glycol) diglycidyl ether crosslinking onto a graphite electrode. When the TvGDH-based biosensor was tested with maltose it showed a sensitivity of 1.7 μA mM^-1cm^-2, a linear range of 0.5-15 mM, and a detection limit of 0.45 mM. Furthermore, it gave the lowest apparent Michaelis-Menten constant (K_{M app}) of 19.2 ± 1.5 mM towards maltose when compared to other sugars. The biosensor is also able to detect other saccharides including glucose, maltotriose and galactose, these however also interfere with maltose sensing.

Fruit quality and volatile constituents of a new very early-ripening pummelo (Citrus maxima) cultivar 'Liuyuezao'

'Liuyuezao' (LYZ) pummelo (Citrus maxima) originated from a spontaneous bud sport on a 'Guanxi' (GXB) pummelo tree and was released as a new very early-season cultivar. The objective of this study was to present the sensory and nutritional profiles of LYZ fruits, and compare it with other major commercialized pummelo cultivars including GXB, 'Sanhong' (SH) and 'Hongrou' (HR). LYZ had higher contents of organic acids (12.01 mg/g), phenols (669.01 mg/L), vitamin C (75.73 mg/100 mL) and stronger antioxidant capacity (77.65 mg/100 mL) but lower levels of soluble sugars (62.85 mg/g), carotenoids (0.25 mg/L) and flavonoids (46.3 mg/L) when compared to the other pummelos. Moreover, a smaller number (49) and much less content (7.63) of fruit volatiles were detected in LYZ than them in GXB, SH and HR. The relatively high levels of fructose (20.6 mg/g) and organic acids and low levels of volatile compounds in LYZ mainly contributed to its sweet and mildly sour taste and moderate aroma of pummelo note. LYZ is presented as an alternative pummelo cultivar with the potential for commercialization.

Sensory sweetness and sourness interactive response of sucrose-citric acid mixture based on synergy and antagonism

The clarity of taste sensation interaction is a key basis for promoting the food sensory science research and its application to the beverage and food additive industries. This study explored the synergy and antagonism effect of sucrose-citric acid mixture and established an optimized method to determine the human sweetness and sourness interactive response. Sucrose-citric acid mixtures were evaluated by the “close type” question. According to the sensory difference strength curves and Weber–Fechner law, citric acid increased the sucrose’s absolute threshold (0.424–0.624%) and weber fraction (20.5–33.0%). Meanwhile, sucrose increased citric acid’s absolute threshold (0.0057–0.0082%) and decreased its weber fraction (17.96–9.53%). By fitting absolute threshold and weber fraction variation equations, the sweet–sour taste sensory strength variation models (SSTVM) were derived, which could be used to explain the synergy and antagonism effect of sweet–sour taste. According to the SSTVM, the interactive response to sweet–sour taste could be quantitatively calculated. The high coincidence between SSTVM and human evaluation (1.02% of relative error) indicated that it could be applied in the food industry, health management, and intelligent sensory science.

Comparative elucidation of bioactive and volatile components in dry mature jujube fruit (Ziziphus jujuba Mill.) subjected to different drying methods

This study investigated the effects of convective drying(CD) and freeze drying(FD) on bioactive and volatile components in jujube. No significant difference in total phenolic, total flavonoids and antioxidant capacity among CD60, CD70, CD80 and FD samples (P > 0.05). LC-MS/MS analysis showed that this trend mainly originated from the dynamic equilibrium relationships between caffeic acid, chlorogenic acid, p-hydroxybenzoic acid, rutin, epicatechin, and quercetin. HS-SPME-GC-MS identified 31 volatile organic compounds (VOCs) comprising more than 80% aldehydes and acids. Principal component analysis distinguished the VOC characteristics of samples subjected to different drying methods. Six VOCs had an odor activity value (OAV) >1, most of which were fatty acid oxidation or Maillard reaction products. Combined with the precursor components, these reactions were speculated to be the major VOC-producing pathways in dried jujube. Considering the bioactive components and flavor retention, CD at 60 °C was an effective drying method with potential to replace FD.

An optimized organic acid human sensory sourness analysis method

BACKGROUND

Sour taste perception builds on both chemical and physiological foundations, and plays an important role in food flavor, including that of fruit, beer, wine, and other beverages. A uniform sourness standard and sourness conversion method for researchers and food enterprises is necessary to obtain uniform conclusions.

RESULTS

This study established an optimized organic acid sensory sourness analysis and sourness conversion method. It is based on sour sensory difference strength curves, which consist of an absolute threshold value and sensory difference threshold values. Defining the absolute threshold value of citric acid sourness as 1, sourness could be calculated according to the curve. With a logarithmic curve form, the acid sourness indexes (AI) were calculated as 1, 0.74, 0.77, 1.31, and 1.21 for citric, malic, fumaric, lactic, and tartaric acid samples, respectively. Consequently, each acid's sourness and concentration could be obtained and converted. Single acid and mixed acid sourness comparison evaluation's result implied that the novel method was more accurate (91.7-100%) than the hydrogen ion concentration method.

CONCLUSION

The novel sourness determination and conversion equation would provide more accurate sourness standard and calculation method in food sensory areas. © 2021 Society of Chemical Industry.

Utilization and evaluation of Citrus natsudaidai peel waste as a source of natural food additives

This study aims to obtain beneficial ingredients from Citrus natsudaidai (CN) peel waste. The yields of ingredients were 26.2-31.6 mg/g dried material (DM) in pectin, 466-581 mg/g DM in insoluble dietary fiber, 5.56-7.15 g/kg fresh material (FM) in the hexane extracts obtained from CN peels, 23.8-27.0 mg/g DM in naringin, and 8.30-10.2 mg/g DM in neohesperidin. A sensory evaluation and instrumental assays using an Electronic nose and Electronic tongue were performed to evaluate aqueous solutions flavored with 0.02% hexane extracts obtained from CN peels. CN-flavored solutions had a preferred smell over commercial citrus-flavored drinks and were classified into the same group as commercial citrus juices in the Electronic nose assay. In addition, CN-flavored solutions showed sourness, bitterness, and orange-like taste, and the overall acceptance of CN-flavored solutions did not significantly differ from commercial citrus-flavored drinks. CN peel waste can be industrially utilized as a source of natural food additives.

Sucrose detection and discrimination estimated by the analysis of psychometric functions with linear and non-linear models

Sucrose detection and discrimination thresholds were determined by conducting two alternative forced-choice tests with aqueous solutions. The standard models probit and logit, and non-linear were fitted to the empirical psychometric functions. 0, 7 and 15 g/L sucrose solutions were used as standard stimuli in the detection and discrimination experiments (two levels) respectively. Comparison stimuli consisted of aqueous sucrose solutions with concentrations from 0.5 to 25 g/L. Observed absolute threshold was around 2.96 g/L and the difference limen for 7 and 15 g/L standard stimuli was around 2.98 g/L and 5.29 g/L, respectively. Calculated Weber fractions for 7 and 15 g/L standard stimuli were 0.42 and 0.35, respectively. Judges' performance in the discrimination experiment was similar to that observed in the detection experiment. Goodness of fit for probit and logit models was similar. The non-linear model showed a lower average error and demonstrated an excellent predictive ability.

Physico-chemical characterization of Cornus kousa Burg. fruit: determining optimal maturity for fresh consumption

BACKGROUND

Japanese dogwood (Cornus kousa Burg.) is a popular ornamental plant which develops edible compound fruit utilized in traditional Asian medicine. Previous compositional studies have focused on a small fraction of secondary metabolites at a single maturity stage. In order to address the question of optimal ripeness of Japanese dogwood fruit for consumption the study provides a comprehensive insight into its primary and secondary metabolic profile.

RESULTS

The aim of the study was to investigate biochemical composition and morphological traits of Japanese dogwood (Cornus kousa Burg.) fruit at four maturity stages: GF, green fruit; BF, fruit with a defined red blush; RF, ripe fruit; OF, over-ripe fruit. Fruit was characterized by a nearly spherical shape, decreased water content in later stages of ripeness and highest a* values at RF and OF stages. Total sugars increased significantly from GF to OF stage and total organic acids and vitamin C decreased with maturation. Japanese dogwood fruit was characterized by four major phenolic groups: anthocyanins (three), flavonols (eight) hydroxycinnamic acids (three) and flavonoids (one) as well as by four lipophilic antioxidants: tocopherols (two), xanthophylls (five), carotenes (two) and chlorophylls (two). The progression of fruit ripening caused faster accumulation of individual phenolic compounds and lipophilic antioxidants which resulted in significantly higher total phenolic content at the RF and OF stages.

CONCLUSION

Japanese dogwood fruit is a rich alternative source of ascorbic acid, α-tocopherol, flavonols and anthocyanins and should be consumed fresh at fully developed red colour of compound berries when their composition is optimal. © 2020 Society of Chemical Industry.

Fruit Quality Characterization of New Sweet Cherry Cultivars as a Good Source of Bioactive Phenolic Compounds with Antioxidant and Neuroprotective Potential

Sweet cherries (Prunus avium L.) are highly appreciated fruits for their taste, color, nutritional value, and beneficial health effects. In this work, seven new cultivars of sweet cherry were investigated for their main quality traits and nutraceutical value. The phytochemical profile of three classes of phenolic compounds and the antioxidant activity of the new cultivars were investigated through high-performance liquid chromatography with diode array detection (HPLC-DAD) and spectrophotometric assays, respectively, and compared with those of commonly commercialized cultivars. Cyanidine-3-O-rutinoside was the main anthocyanin in all genotypes, and its levels in some new cultivars were about three-fold higher than in commercial ones. The ORAC-assayed antioxidant capacity was positively correlated with the total anthocyanin index. The nutraceutical value of the new cultivars was investigated in terms of antioxidant/neuroprotective capacity in neuron-like SH-SY5Y cells. Results demonstrated that the new cultivars were more effective in counteracting oxidative stress and were also able to upregulate brain-derived neurotrophic factor (BDNF), a pro-survival neurotrophin, suggesting their potential pleiotropic role in counteracting neurodegenerations.