Markus Stieger

How will better products improve the sensory-liking and willingness to buy insect-based foods?

Insects have been established to be a more sustainable alternative source of protein in comparison to conventional meats, but have little appeal to those who are unfamiliar with their taste. Yet little attention has been given to understanding how more appealing products could be developed, and whether that is sufficient to encourage consumption of a culturally unusual food. By evaluating appropriate (i.e. meatball) and inappropriate (i.e. dairy drink) mealworm products along with the original mealworm-free products, this study provided new insights into how the product influences sensory-liking and willingness to buy insect-based foods for trial and regular consumption. Willing (n=135) and unwilling tasters (n=79) were recruited to explore differences between individuals who differ in their intentions to eat insects. An appropriate product context improved the expected sensory-liking and willingness to buy mealworm products once and regularly. However, consumers should first be motivated to eat insects for a better product to improve consumption intentions. Descriptive sensory profiling revealed that mealworm products were expected and experienced to taste very different from the original mealworm-free products, but were generally preferred to taste similar to the original, albeit with some unique attributes. Using a familiar and liked product preparation could help to increase trial intentions, but the product should also be appropriate and taste good if it is to be regularly consumed. We conclude that even with high interest and good products, willing consumers still hesitate to consume insect-based foods regularly due to other practical and socio-cultural factors. We recommend that future research should not only give emphasis to increasing initial motivations to try, but should address the barriers to buying and preparing insects for regular consumption, where issues relating to availability, pricing, knowledge and the social environment inhibit the uptake of this culturally new food.

Effect of extraction pH on heat-induced aggregation, gelation and microstructure of protein isolate from quinoa (Chenopodium quinoa Willd)

The aim of this study was to determine the influence of extraction pH on heat-induced aggregation, gelation and microstructure of suspensions of protein isolates extracted from quinoa (Chenopodium quinoa Willd). Quinoa seed protein was extracted by alkaline treatment at various pH values (pH 8 (E8), 9 (E9), 10 (E10) and 11 (E11)), followed by acid precipitation. The obtained protein isolates were freeze dried. The protein isolates E8 and E9 resulted in a lower protein yield as well as less protein denaturation. These isolates also had a higher protein purity, more protein bands at higher molecular weights, and a higher protein solubility in the pH range of 3-4.5, compared to the isolates E10 and E11. Heating the 10%w/w protein isolate suspensions E8 and E9 led to increased aggregation, and semi-solid gels with a dense microstructure were formed. The isolate suspensions E10 and E11, on the other hand, aggregated less, did not form self-supporting gels and had loose particle arrangements. We conclude that extraction pH plays an important role in determining the functionality of quinoa protein isolates.

Individually Modified Saliva Delivery Changes the Perceived Intensity of Saltiness and Sourness

Individuals vary largely in their salivary flow and composition, and given the importance of saliva on perception of taste, this might influence how the tastant stimuli are perceived. We therefore hypothesise that altering the individual salivary flow rates has an impact on the perceived taste intensity. In this study, we investigated the role of saliva amount on the perceived taste intensity by excluding parotid saliva and adding artificial saliva close to the parotid duct at preset flow rates. Significant decreases in perception with increasing salivary flow rates were observed for citric acid and sodium chloride. This can partially be explained by a dilution effect which is in line with previous studies on detectable concentration differences. However, since the bitterness and sweetness remained unaffected by the salivary flow conditions and the dilution effect was comparable to that of saltiness, further explanation is needed. Furthermore, we investigated whether the suppression of taste intensity in binary mixtures (taste–taste interactions) could possibly be caused by the increased salivary flow rate induced by an additional taste attribute. The results show, however, that suppression of taste intensity in binary mixtures was not affected by the rate of salivation. This was more likely to be explained by psychophysics.

Identification, quantification, and sensory characterization of steviol glycosides from differently processed Stevia rebaudiana commercial extracts.

Stevia rebaudiana is known for its sweet-tasting ent-kaurene diterpenoid glycosides. Several manufacturing strategies are currently employed to obtain Stevia sweeteners with the lowest possible off-flavors. The chemical composition of four commercial S. rebaudiana extracts, obtained by different technologies, was characterized using UHPLC-ESI-MS(n). The composition of one of the ethanol-crystallized extracts (EC2) was entirely rebaudioside A, whereas the enzymatically modified (EM) extract contained the lowest concentration of this compound (2.7 mg/100 mg). The membrane-purified (MP) extract had the highest content of minor natural steviol glycosides (23.7 mg/100 mg total extract) versus an average of 2.4 mg/100 mg total extract for the EC samples. Thirteen trained panelists evaluated sweetness, bitterness, licorice, and metallic attributes of all four extracts. The highest licorice intensity (p ≤ 0.05) was found for MP. Both samples EC1 and EC2, despite their different chemical compositions, showed no significant differences in sensory perception.

Physical and sensory characterizations of oral coatings of oil/water emulsions.

The physical and sensory properties of oil coatings on the tongue formed by five oil/water emulsions varying in oil content were investigated. A total of 20 subjects processed orally each emulsion for 30 s in triplicate. In vivo fluorescence measurements at the front and back of the anterior tongue were made to quantify the oil fraction deposited at different time points. Calibration lines relating fluorescence intensity to oil fraction were determined using pig tongues at 37.5 °C to mimic oral conditions. The oil fraction on the tongue increased linearly with an increasing oil content of the emulsions. The oil fraction deposited at the back of the anterior tongue was 1.5-2.0× larger than at the front. The intensity of sensory attributes describing after-feel perception was related to the oil fraction by Weber-Fechners law. This study uses in vivo fluorescence to study food behavior in the mouth and unravel new insights in after-feel perception of emulsions.

Combinatory Effects of Texture and Aroma Modification on Taste Perception of Model Gels

In this study, the effects of texture modification and aroma-induced sweetness enhancement were systematically investigated in apple-flavored semi-solid Na-caseinate gels. Gels containing apple juice as a basic flavor were developed differing in stiffness, brittleness and serum release (texture modification), aroma, and sugar concentration (flavor modification). In a full factorial design (2 × 2 × 2), eight samples were evaluated by a sensory panel on ten attributes (five texture, five flavor). Sweetness was enhanced significantly by modification of texture, aroma, and sugar concentration. Texture modification was found to be by far the greatest contributor to overall sweetness. In comparison to texture modifications, aroma modification and changes of sugar concentration resulted only in small sweetness enhancement. When texture and aroma modifications are combined, a small additive effect of aroma modification on sweetness enhancement was found in addition to the sweetness enhancement caused by texture modification. This suggests that the relationship between texture (modification) and flavor (modification) and sweetness is additive in a nonlinear manner. It can be concluded that texture modification is a valid tool to enhance taste intensity. Hence, texture modification can compensate for a loss of sweet taste intensity induced by sugar reduction, while aroma-induced sweetness enhancement can contribute to further taste enhancement in order to develop healthier products.

Effects of Visual Priming on Taste-Odor Interaction

Little is known about the influence of visual characteristics other than colour on flavor perception, and the complex interactions between more than two sensory modalities. This study focused on the effects of recognizability of visual (texture) information on flavor perception of odorized sweet beverages. Participants rated the perceived sweetness of odorized sucrose solutions in the presence or absence of either a congruent or incongruent visual context. Odors were qualitatively reminiscent of sweet foods (strawberry and caramel) or not (savoury). Visual context was either an image of the same sweet foods (figurative context) or a visual texture derived from this product (non-figurative context). Textures were created using a texture synthesis method that preserved perceived food qualities while removing object information. Odor-taste combinations were rated sweeter within a figurative than a non-figurative context. This behaviour was exhibited for all odor-taste combinations, even in trials without images, indicating sustained priming by figurative visual context. A non-figurative context showed a transient sweetening effect. Sweetness was generally enhanced most by the strawberry odor. We conclude that the degree of recognizability of visual information (figurative versus non-figurative), influences flavor perception differently. Our results suggest that this visual context priming is mediated by separate sustained and transient processes that are differently evoked by figurative and non-figurative visual contexts. These components operate independent of the congruency of the image-odor-taste combinations.

Descriptive sensory profiling of double emulsions with gelled and non-gelled inner water phase

The use of double emulsions (w1/o/w2) has been acknowledged as a promising strategy to reduce oil content in several food applications. Despite the potential of double emulsions for oil reduction, their sensory properties have not been investigated. In this study, we investigated sensory perception of double emulsions by descriptive sensory profiling using a trained panel (n=11). Two sets of emulsions with either 30 or 50% dispersed phase fraction were studied. Each set differed in composition (gelled and non-gelled inner w1 phase, gelatin as gelling agent) and fat reduction level (30 to 50%), but was similar in oil droplet size and viscosity. Fat reduction level depended on the amount of water droplets entrapped inside the oil droplets. Emulsions were evaluated on nine attributes describing taste (T), mouth-feel (MF) and after-feel (AF) perception, including thickness (MF), creaminess (MF, AF), fattiness (MF, AF), and cohesiveness (MF). The replacement of oil by small water droplets w1 did not decrease the intensity of fat-related attributes. When inner w1 droplets were gelled, 47wt.% of oil could be replaced while increasing the intensity of fat-related attributes. This indicates that the sensory perception of single and double emulsions with gelled and non-gelled w1 phase is mainly determined by the total oil droplet surface area. The composition of the inner water phase (gelled or not) also influences the sensory perception of double emulsions. We conclude that fat reduction up to 47wt.% can be achieved in double emulsions while maintaining or enhancing fat-related sensory perception.

Sensory and health properties of steamed and boiled carrots (Daucus carota ssp. sativus)

Abstract This study examined the influences of domestic processing conditions applied by consumers on firmness, colour and amount of phytochemicals and liking and sensory attributes intensity rating of carrots. The aim was to identify a cooking method and time that yields carrots with higher amount of β-carotene while maintaining consumer liking. Instrumentally measured firmness and colour showed comparable degradation trends between cooking methods. While boiling showed a significant decrease in the amount β-carotene after 20 min (−19%), steaming maintained the amount (+40%). Cooking method did not show a significant effect on liking and intensity ratings for the majority of the sensory attributes. Medium firm carrots were liked the most and low firm carrots the least. This study demonstrates that for optimum liking, carrots should be in the range of medium firmness. This can be obtained through either cooking methods but steamed carrots possess a higher amount of β-carotene and maintains liking.

High-Pressure–High-Temperature Processing Reduces Maillard Reaction and Viscosity in Whey Protein–Sugar Solutions

The aim of the study was to determine the influence of pressure in high-pressure-high-temperature (HPHT) processing on Maillard reactions and protein aggregation of whey protein-sugar solutions. Solutions of whey protein isolate containing either glucose or trehalose at pH 6, 7, and 9 were treated by HPHT processing or conventional high-temperature (HT) treatments. Browning was reduced, and early and advanced Maillard reactions were retarded under HPHT processing at all pH values compared to HT treatment. HPHT induced a larger pH drop than HT treatments, especially at pH 9, which was not associated with Maillard reactions. After HPHT processing at pH 7, protein aggregation and viscosity of whey protein isolate-glucose/trehalose solutions remained unchanged. It was concluded that HPHT processing can potentially improve the quality of protein-sugar-containing foods, for which browning and high viscosities are undesired, such as high-protein beverages.