Food structure: Roles of mechanical properties and oral processing in determining sensory texture of soft materials

Food-Oral Processing: Current Progress, Future Directions, and Challenges

Oral processing refers to the series of physical, chemical, and biological processes inside the oral cavity when we consume food. This process affects the taste, quality, and nutrient absorption of the body. In the human diet, oral processing plays a crucial role because it impacts not only the food flavor and texture but also the absorption and utilization of nutrients. With the progress of science and technology and the increasing demand for food, the study of oral processing has become increasingly important. This paper reviews the history and definition of oral processing, its current state of research, and its applications in food science and technology, focusing on personalized taste customization, protein structure modification, food intake and nutrition, and bionic devices. It also analyzes the impact of oral processing on different types of food products and explores its potential in the food industry and science research.

The heat is on: Consumers modify their oral processing behavior when eating spicy foods

Food texture properties and consumer characteristics influence oral processing behaviors. Little is known about oral processing behavior of pungent spicy foods. In two experiments, we investigated how adding ground dried chilies to tomato soup or beef patties and curried rice altered oral processing behaviors. In Experiment One, tomato soups differing in concentration of added ground dried chilies (0.01, 0.03, 0.20 or 0.40% w/w) were consumed (n = 23). In Experiment Two, lunch meals that differed in added ground dried chilies consisting of beef patties (0.0, 0.6 or 1.2% w/w) and curried rice (0.0, 0.4 or 1.0% w/w) were consumed (n = 49). Sip/bite sizes were determined using hidden balances. Oral processing behavior was quantified using video recordings followed by post hoc annotations of specific behaviors. When eating tomato soup, increasing oral burn was associated with increasing number of water sips, water intake and total time between sips. For the solid meals (beef patties and curried rice), increasing oral burn was associated with increased time between bites and total sips of water; conversely, total oral exposure time, total number of chews and number of chews per bite all decreased with greater burn. Saliva content and rate of saliva incorporation into the solid food bolus increased with added ground dried chilies while oral exposure time decreased. We conclude consumers adapt their oral processing behaviors to oral burn of solid foods by reducing oro-sensory exposure time, chewing bites less, increasing time between bites, and consuming more water, potentially to mitigate the discomfort associated with the burn imparted by ground dried chilies.

Exploring Taiwanese Consumer Dietary Preferences for Various Vinegar Condiments: Novel Dietary Patterns across Diverse Cultural Contexts

The use of vinegar as a culinary seasoning in various global cuisines to enhance the taste characteristics and profiles of foods has been extensively documented in the culinary literature. Particularly notable is traditional Taiwanese-style thick soup, where the incorporation of vinegar plays a fundamental role in imparting distinct flavors. In the context of this experimental investigation, the foundational base of Taiwanese-style thick soup serves as the platform for a meticulously planned sensory and dietary behavior evaluation. Our research methodology combines the use of survey questionnaires and experimental techniques, employing purposive sampling and snowball sampling methods to recruit participants. The central focus of this study is to understand consumers' culinary preferences when presented with a choice between two contrasting types of vinegar-specifically, black vinegar and balsamic vinegar-as alternative gastronomic enhancements. This precise orchestration of data collection and systematic evaluation provides a perceptive window into participants' culinary inclinations and food choices, resulting in a detailed and profound understanding of their taste preferences. The empirical findings stemming from this experimentation reveal notably significant differences in the sensory assessments among participants engaging in diverse culinary experiences. Notably, distinct variations are observed in terms of visual perceptions, olfactory distinctions, and overall sensory satisfaction. This study occupies a crucial position within existing research paradigms by strategically expanding the scope of sensory investigations within the realm of Taiwanese-style thick soup. This introduces an innovative aspect represented by the introduction of balsamic vinegar as a compelling alternative to the customary black vinegar. As a result, the emerging findings not only offer compelling insights into the nuanced food choice and taste preferences of consumers, but also open up new and innovative directions within the complex tapestry of Chinese gastronomy.

Different methods for textural evaluation of freeze-dried candies during storage

The textural changes during storage of two freeze-dried candies developed from blackcurrant fruits, unflavored yogurt, and different alternative sweeteners, one sweetened with honey/isomalt (HI) and another sweetened with isomalt/stevia (IS), were analyzed using three different methods (instrumental, sensory, and image analysis). Fresh candies were in the supercooled state and presented different structural and textural characteristics (HI: compact and homogeneous, and IS: porous and crunchy), with Fmax values of 139 ± 14 and 174 ± 16 N for HI and IS, respectively. After storage, the instrumental analysis showed approximately 60% average drop in Fmax and W values, in agreement with the decrease observed by sensory analysis in hardness, fracturability, and crispness. Image analysis showed an increase in parameters related to the homogeneity and the uniformity/smoothness for HI. Pearson's correlation coefficients analysis showed that there was a good correlation between the three techniques used, suggesting that the joint use of these methods could be performed for a better understanding of complex food texture.

The effect of high-temperature heat treatment and homogenization on the microstructure of set yogurt curd networks

Set yogurt's physical characteristics are greatly affected by the homogenization and heat treatment processes. In our previous study, set yogurt treated at 130°C and with the fat particle size reduced to ≤0.6 μm had equivalent curd strength, less syneresis and smoother texture than yogurt treated at 95°C. When investigating the mechanisms underlying yogurt's physical properties, it is important to evaluate the yogurt's microstructure. We conducted electron microscopy evaluations to investigate the mechanisms of changes in yogurt's physical properties caused by 130°C heat treatment and by a reduction in the fat globule size. We prepared yogurt mixtures by combining heat treatment at 95 and 130°C and homogenization pressure at 10 + 5 and 35 + 5 MPa and then fermented the mixtures in a common yogurt starter. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for the structural observations. Fine particles were observed on the surface of the casein micelles of the yogurt treated at 95°C, and the coalescence density between micelles was high. The surface of the yogurt treated at 130°C had few fine particles, and the coalescence density between micelles was low. The yogurt treated at 130°C with 35 + 5 MPa homogenization had low coalescence density between casein micelles, but smaller-particle-size fat globules increased the network density. Approximately 30% of the fat globules were estimated to be incorporated into the yogurt networks compared to the volume of casein micelles. We speculate that 130°C heat treatment alters the structure of whey protein on the surface of casein micelles and interferes with network formation, but reducing the size of fat globules reinforces the network as a pseudoprotein.

Application of small angle scattering (SAS) in structural characterisation of casein and casein-based products during digestion

In recent years, small and ultra-small angle scattering techniques, collectively known as small angle scattering (SAS) have been used to study various food structures during the digestion process. These techniques play an important role in structural characterisation due to the non-destructive nature (especially when using neutrons), various in situ capabilities and a large length scale (of 1 nm to ∼20 μm) they cover. The application of these techniques in the structural characterisation of dairy products has expanded significantly in recent years. Casein, a major dairy protein, forms the basis of a wide range of gel structures at different length scales. These gel structures have been extensively researched utilising scattering techniques to obtain structural information at the nano and micron scale that complements electron and confocal microscopy. Especially, neutrons have provided opportunity to study these gels in their natural environment by using various in situ options. One such example is understanding changes in casein gel structures during digestion in the gastrointestinal tract, which is essential for designing personalised food structures for a wide range of food-related diseases and improve health outcomes. In this review, we present an overview of casein gels investigated using small angle and ultra-small angle scattering techniques. We also reviewed their digestion using newly built setups recently employed in various research. To gain a greater understanding of micro and nano-scale structural changes during digestion, such as the effect of digestive juices and mechanical breakdown on structure, new setups for semi-solid food materials are needed to be optimised.

Developing a novel method to measure texture changes of semi-solid food during a continuous compressive motion with high deformation using repeatable dual extrusion cell (RDEC)

Mechanical changes during mastication are difficult to evaluate without using a novel method because the size of the sample is continuously and randomly reduced. The repeatable dual extrusion cell (RDEC) has been developed to measure the breakdown characteristics of a semi-solid food (i.e., minced pork gel) from initial solid states to a small particle size during repeated high deformation compressive motions. The force-time curve of RDEC was recorded, followed by a calculation of work values for each cycle and fitted by Peleg's model. The decrease of k₁ (1.7-1.19) and k₂ (1.56-1.42) values in Peleg's model with an increase of moisture content (56.5-62.5 %) indicated the easily deformable characteristics of soft food. During RDEC measurement, as long as the characteristic length of the sample was larger than the diameter of RDEC probe hole (>4.5 mm), the initial sample size showed no significant influence (p < 0.05) on the measurements. RDEC demonstrated similar ratios of particulate size with human subjects up till 20 cycles of processing. The equilibrium force value from RDEC and SEM images demonstrate that the connective tissue in pork gel mainly contributed to the end-product texture properties after continuous mastication. This study provided an application of the novel RDEC device to estimate the texture and structural changes of minced pork gel under a continuous high deformation compressive motion.

Bread Products from Blends of African Climate Resilient Crops: Baking Quality, Sensory Profile and Consumers' Perception

With food insecurity rising dramatically in Sub-Saharan Africa, promoting the use of sorghum, cowpea and cassava flours in staple food such as bread may reduce wheat imports and stimulate the local economy through new value chains. However, studies addressing the technological functionality of blends of these crops and the sensory properties of the obtained breads are scarce. In this study, cowpea varieties (i.e., Glenda and Bechuana), dry-heating of cowpea flour and cowpea to sorghum ratio were studied for their effects on the physical and sensory properties of breads made from flour blends. Increasing cowpea Glenda flour addition from 9 to 27% (in place of sorghum) significantly improved bread specific volume and crumb texture in terms of instrumental hardness and cohesiveness. These improvements were explained by higher water binding, starch gelatinization temperatures and starch granule integrity during pasting of cowpea compared to sorghum and cassava. Differences in physicochemical properties among cowpea flours did not significantly affect bread properties and texture sensory attributes. However, cowpea variety and dry-heating significantly affected flavour attributes (i.e., beany, yeasty and ryebread). Consumer tests indicated that composite breads could be significantly distinguished for most of the sensory attributes compared to commercial wholemeal wheat bread. Nevertheless, the majority of consumers scored the composite breads from neutral to positive with regard to liking. Using these composite doughs, chapati were produced in Uganda by street vendors and tin breads by local bakeries, demonstrating the practical relevance of the study and the potential impact for the local situation. Overall, this study shows that sorghum, cowpea and cassava flour blends can be used for commercial bread-type applications instead of wheat in Sub-Saharan Africa.

Pea protein–sugar beet pectin binders can provide cohesiveness in burger type meat analogues

Methylcellulose is commonly used in meat analogues for binding ingredients. In this study, we compared the binding properties of a methylcellulose hydrogel (5% w/w) to a novel, clean-label binder based on a mixture of pea protein and sugar beet pectin (r = 2:1, 22.5% w/w, pH 6.0) with and without laccase addition in a burger type meat analogue. It was shown that the pea protein–pectin binder glued vegetable protein particles and fat mimic particles together prior to cooking and frying, thereby improving forming of the mass into burger patties. Furthermore, sensory analysis revealed that the cohesiveness of the fried burger patties was better when the protein–pectin binder was used. However, the used binder system did not affect the hardness of the burger patties indicating that the binders rather affected the coherence of the structural elements. Burgers with solid fat particles were rated better in terms of appearance as compared to emulsified fat particles, since the former were not visible. This study is useful to better understand meat analogue product design for a higher acceptance among consumers.

Enrichment of 3D-Printed k-Carrageenan Food Gel with Callus Tissue of Narrow-Leaved Lupin Lupinus angustifolius

The aim of the study is to develop and evaluate the printability of k-carrageenan inks enriched with callus tissue of lupin (L. angustifolius) and to determine the effect of two lupin calluses (LA14 and LA16) on the texture and digestibility of 3D-printed gel. The results demonstrated that the enriched ink was successfully 3D printed at concentrations of 33 and 50 g/100 mL of LA14 callus and 33 g/100 mL of LA16 callus. The feasibility of 3D printing is extremely reduced at higher concentrations of callus material in the ink. The hardness, cohesiveness, and gumminess of the 3D-printed gel with LA16 callus were weakened compared to the gel with LA14 callus. The results of rheological measurements showed that an increase in the content of LA16 callus interfered with the formation of a k-carrageenan gel network, while LA14 callus strengthened the k-carrageenan gel with increasing concentration. Gel samples at different concentrations of LA14 and LA16 calluses formed a spongy network structure, but the number of pores decreased, and their size increased, when the volume fraction occupied by LA14 and LA16 calluses increased. Simple polysaccharides, galacturonic acid residues, and phenolic compounds (PCs) were released from A-FP gels after sequential in vivo oral and in vitro gastrointestinal digestion. PCs were released predominantly in the simulated intestinal and colonic fluids. Thus, incorporating lupin callus into the hydrocolloid ink for food 3D printing can be a promising approach to developing a gelling material with new mechanical, rheological, and functional properties.

A Comprehensive Review of Food Hydrogels: Principles, Formation Mechanisms, Microstructure, and Its Applications

Food hydrogels are effective materials of great interest to scientists because they are safe and beneficial to the environment. Hydrogels are widely used in the food industry due to their three-dimensional crosslinked networks. They have also attracted a considerable amount of attention because they can be used in many different ways in the food industry, for example, as fat replacers, target delivery vehicles, encapsulating agents, etc. Gels-particularly proteins and polysaccharides-have attracted the attention of food scientists due to their excellent biocompatibility, biodegradability, nutritional properties, and edibility. Thus, this review is focused on the nutritional importance, microstructure, mechanical characteristics, and food hydrogel applications of gels. This review also focuses on the structural configuration of hydrogels, which implies future potential applications in the food industry. The findings of this review confirm the application of different plant- and animal-based polysaccharide and protein sources as gelling agents. Gel network structure is improved by incorporating polysaccharides for encapsulation of bioactive compounds. Different hydrogel-based formulations are widely used for the encapsulation of bioactive compounds, food texture perception, risk monitoring, and food packaging applications.

Evaluating the Mechanical Response of Agarose-Xanthan Mixture Gels Using Tensile Testing, Numerical Simulation, and a Large Amplitude Oscillatory Shear (LAOS) Approach

Large deformation stress response characteristics of hydrocolloid mixture gel systems were investigated based on texture and rheological measurements. Agarose and xanthan mixtures at different ratios (1:0, 0.75:0.25, and 0.5:0.5) were chosen as the model systems. A decrease in failure stress from 2.65 to 1.82 MPa and an increase in failure strain from 0.08 to 0.13 with higher xanthan ratios were obtained based on the ring tensile test, indicating that xanthan molecules could improve the flexibility of the agarose network. The gels showed severe water loss by compression, particularly for the pure agarose gel (6.74%). Compared to the compression test, the gels presented low water loss after the ring tensile test (<1.3%) indicating that the ring tensile test could calculate the correct stress−strain relationship. Digital image correlation (DIC) and numerical simulation revealed that agarose-xanthan gel systems possess a deformation behavior with homogeneous strain distribution before failure. Elastic and viscous Lissajous−Bowditch curves from the large amplitude oscillatory shear (LAOS) measurement at different strains and frequencies elucidated that the agarose-xanthan gel was dominated by the agarose structure with a similar magnitude of elasticity at a low frequency. The large deformation approach from this study has great potential for elucidating and understanding the structure of food and biopolymer gels.

Enrichment of Agar Gel with Antioxidant Pectin from Fireweed: Mechanical and Rheological Properties, Simulated Digestibility, and Oral Processing

The aims of the study were to evaluate the influence of pectin isolated from fireweed (FP) on the mechanical and rheological properties of agar (A) gel, to investigate the release of phenolic compounds (PCs) and pectin from A-FP gels at simulated digestion in vitro, and to evaluate the oral processing and sensory properties of A-FP gels. The hardness of A-FP gels decreased gradually with the increase in the concentration of FP added (0.1, 0.4, and 1.6%). The hardness of A-FP1.6 gel was 41% lower than A gel. Rheological tests found A gel was a strong physical gel (storage modulus (G′) >>loss modulus (G″)), and the addition of FP up to 1.6% did not significantly change its G’. The G″ value decreased in A-FP gels compared to A gel. The release of galacturonic acid (GalA) was 3.4 ± 0.5, 0.5 ± 0.2, 2.4 ± 1.0, and 2.2 ± 0.7 mg/mL after digestion of A-FP1.6 gel in the oral in vivo phase (OP) and subsequent incubation in simulated gastric (SGF), intestinal (SIF), and colonic (SCF) fluids in vitro. The incubation medium after OP, SGF, and SIF digestion of A-FP1.6 contained 24−64 μg GAE/mL of PCs, while SCF contained 144 μg GAE/mL, supposing a predominant release of antioxidant activity from the gel in the colon. Chewing to readiness for swallowing A-FP gel required less time and fewer chews with less activity of the masseter and temporalis muscles. A-FP1.6 gel had a lower likeness score for taste and consistency and a similar score for appearance and aroma when compared with A gel. Thus, A-FP gels were weakened compared to A gel and required less time and muscle activity for oral processing. A-FP gel had antioxidant activity due to the PCs associated with pectin, while A gel had no antioxidant activity.

Application of Food Mechanics and Oral Processing in Modelling First Bite of Grilled Meat

This study analyzed the potential of modelling meat mastication by using pork and poultry meat as food with different physical properties under different grilling temperatures. For the purpose of modelling oral processing, temporal dominance of sensations and finite element methods were employed. A panel with ten subjects was trained and used for oral processing analysis and temporal dominance of sensations revealing in-mouth sensations and mastication characteristics. In parallel, the second aim was to evaluate the mechanical properties of the samples and explore the potential of simulating the first bite using the finite element method. Based on the textural parameters, a 3D model of grilled meat was created and a first-bite simulation was performed. A higher level of differences was observed comparing the number of chews for pork meat compared to poultry meat. The chewing rate showed a statistical difference with values in the range of 1.31 chews/s to 1.46 chews/s for pork meat and between 1.36 chews/s and 1.42 chews/s for poultry meat. Firmness was the predominant sensory attribute recognized by panelists at the beginning of mastication, which confirmed our approach used for first-bite modelling. Simulation results show the growth of internal stress following the jaw’s path. Presented models demonstrate that the highest values are around teeth pressure and lead to a conclusion that upon biting, the meat structure will suffer irreversible damage dividing the grilled meat into two pieces, as it happens during the first bite. The main conclusion of this study is that by combining results from oral processing and testing of mechanical properties of the grilled products, it is possible to simulate the first bite.

Modulating aroma release of flavour oil emulsion based on mucoadhesive property of tannic acid

Flavour is a crucial sensory element that determines the consumers' preference for food and beverages. In this study, we determined the effects of complex gum arabic (GA) and tannic acid (TA) on the aroma release of flavour oil emulsions in vitro by simulating oral processing conditions. GA and TA were used to stabilize flavour oil emulsions. Visualization of in vitro retention using ex vivo porcine tongue, detection of aroma release in the model mouth, and sensory evaluation of flavour emulsions were performed to determine the effect of TA and GA. The results indicated that the retention of emulsions and the release of aroma compounds were modulated by TA and GA, which could be because of interactions that occurred between GA and TA in emulsions and mucins on the tongue. GA enhanced aroma release, whereas TA contributed to the retention or slow release of target aroma compounds.

Multi-Scale Structures and Functional Properties of Quinoa Starch Extracted by Alkali, Wet-Milling, and Enzymatic Methods

The purpose of this study is to investigate the effects of starch extraction methods (alkali, wet-milling, and enzymatic) on the multi-scale structures and functional properties of quinoa starch. When the enzymatic method was compared with alkali and wet-milling, it showed higher protein content (2.39%), larger size of aggregated granules (44.1 μm), higher relative crystallinity (29.6%), scattering intensity (17.8 α.u.), absorbance ratio of 1047/1022 (0.9), single and double helical content (8.2% and 23.1%), FWHM ratio (2.1), and average molecular weight and radius of gyration (1.58 × 107 g/mol and 106.8 nm), respectively. Similarly, quinoa starch by enzymatic extraction had a higher onset (82.1 °C), peak (83.8 °C), and conclusion (86.3 °C) temperatures, as well as an enthalpy change (6.7 J/g). It further showed maximum hardness (238.8 N), gumminess (105.6 N), chewiness (80.2 N), SDS content (7.5% of raw and 4.8% of cooked), and RS content (15.5% of raw and 13.9% of cooked), whereas it contained minimum RDS content (77.1% of raw and 81.9% of cooked). The results suggest that extraction of starch by the enzymatic method could be a viable approach to retain the native structure of starch and may eventually improve the glycemic response.

A comprehensive review of food gels: formation mechanisms, functions, applications, and challenges

Gels refer to the soft and flexible macromolecular polymeric materials retaining a large amount of water or biofluids in their three-dimensional network structure. Gels have attracted increasing interest in the food discipline, especially proteins and polysaccharides, due to their good biocompatibility, biodegradability, nutritional properties, and edibility. With the advancement of living standards, people's demand for nutritious, safe, reliable, and functionally diverse food and even personalized food has increased. As a result, gels exhibiting unique advantages in food application will be of great significance. However, a comprehensive review of functional hydrogels as food gels is still lacking. Here, we comprehensively review the gel-forming mechanisms of food gels and systematically classify them. Moreover, the potential of hydrogels as functional foods in different types of food areas is summarized, with a special focus on their applications in food packaging, satiating gels, nutrient delivery systems, food coloring adsorption, and food safety monitoring. Additionally, the key scientific issues for future food gel research, with specific reference to future novel food designs, mechanisms between food components and matrices, food gel-human interactions, and food gel safety, are discussed. Finally, the future directions of hydrogels for food science and technology are summarized.

Strategies to improve meat-like properties of meat analogs meeting consumers' expectations

Due to environmental and ethical concerns, meat analogs represent an emerging trend to replace traditional animal meat. However, meat analogs lacking specific sensory properties (flavor, texture, color) would directly affect consumers' acceptance and purchasing behavior. In this review, we discussed the typical sensory characteristics of animal meat products from texture, flavor, color aspects, and sensory perception during oral processing. The related strategies were detailed to improve meat-like sensory properties for meat analogs. However, the upscaling productions of meat analogs still face many challenges (e.g.: sensory stability of plant-based meat, 3D scaffolds in cultured meat, etc.). Producing safe, low cost and sustainable meat analogs would be a hot topic in food science in the next decades. To realize these promising outcomes, reliable robust devices with automatic processing should also be considered. This review aims at providing the latest progress to improve the sensory properties of meat analogs and meet consumers' requirements.

Determining the relationship between food texture and dental condition: First bite and chewing aspects

Among the sensory properties of foods, texture perception is a complex modality due to catastrophic changes during eating. Relating dental conditions and capacity of texture sensation are still paucities in the literature. Different dental areas emphasize the difference in texture sensation. Anterior teeth are responsible for biting, ripping or tearing; while posterior teeth are chewing and grinding. Hence, the absence of any is expected to cause disruptions in mastication functions. The hypothesis of the present study was dental loss or missing is a burden for hardness perception for first-bite and twice chewed for anterior and posterior teeth, respectively. Patient groups were divided according to anterior-posterior tooth deficiencies and hardness sensation was assessed at first bite and twice chewed modal food (white cheese) with various hardness levels obtained with different fat content. The modal food was tested for its physicochemical, textural and sensory properties with dental assessment. Findings suggest that first-bite hardness judgements were not affected by the loss of the anterior. Oppositely, twice chewed hardness has a significant effect on the loss of a posterior tooth. These findings can indicate to future researchers to be tested according to their dental status especially if chewing is necessary for their sensory tests.

Recent application of protein hydrolysates in food texture modification

The demand for clean labels has increased the importance of natural texture modifying ingredients. Proteins are unique compounds that can impart unique textural and structural changes in food. However, lack of solubility and extensive aggregability of proteins have increased the demand for enzymatically hydrolyzed proteins, to impart functional and structural modifications to food products. The review elaborates the recent application of various proteins, protein hydrolysates, and their role in texture modification. The impact of protein hydrolysates interaction with other food macromolecules, the effect of pretreatments, and dependence of various protein functionalities on textural and structural modification of food products with controlled enzymatic hydrolysis are explained in detail. Many researchers have acknowledged the positive effect of enzymatically hydrolyzed proteins on texture modification over natural protein. With enzymatic hydrolysis, various textural properties including foaming, gelling, emulsifying, water holding capacity have been effectively improved. It is evident that each protein is unique and imparts exceptional structural changes to different food products. Thus, selection of protein requires a fundamental understanding of its structure-substrate property relation. For wider applicability in the industrial sector, more studies on interactions at the molecular level, dosage, functionality changes, and sensorial attributes of protein hydrolysates in food systems are required.

Engineering Emulsion Gels as Functional Colloids Emphasizing Food Applications: A Review

Gels are functional materials with well-defined structures (three-dimensional networks) assembled from the dispersed colloids, and capable of containing a large amount of water, oil, or air (by replacing the liquid within the gel pores), known as a hydrogel, oleogel, and aerogel, respectively. An emulsion gel is a gelled matrix filled with emulsion dispersion in which at least one phase, either continuous phase or dispersed phase forms spatial networks leading to the formation of a semisolid texture. Recently, the interest in the application of gels as functional colloids has attracted great attention in the food industry due to their tunable morphology and microstructure, promising physicochemical, mechanical, and functional properties, and superior stability, as well as controlled release, features for the encapsulated bioactive compounds. This article covers recent research progress on functional colloids (emulsion gels), including their fabrication, classification (protein-, polysaccharide-, and mixed emulsion gels), and properties specifically those related to the gel-body interactions (texture perception, digestion, and absorption), and industrial applications. The emerging applications, including encapsulation and controlled release, texture design and modification, fat replacement, and probiotics delivery are summarized. A summary of future perspectives to promote emulsion gels' use as functional colloids and delivery systems for scouting potential new applications in the food industry is also proposed. Emulsion gels are promising colloids being used to tailor breakdown behavior and sensory perception of food, as well as for the processing, transportation, and targeted release of food additives, functional ingredients, and bioactive substances with flexibility in designing structural and functional parameters.

The Source of Protein or Its Value? Consumer Perception Regarding the Importance of Meat(-like) Product Attributes

Food product attributes may significantly influence the general perception of the product itself, as well as the willingness for its consumption. Assessment of the product is based on customers’ beliefs and individual preferences. Because meat-like products are presented as meat substitutes providing sufficient protein values, the present study aimed to determine the effect of protein source and labelling pointing at high protein content on the evaluation of the product. The experimental online study was conducted with a group of 552 respondents. Four versions of product packaging were designed and tested. These packages differed in the presence or absence of the Nutrition Claim and the presence of the text indicating the vegetable or meat origin of the product. Data collected in the experiment were analyzed using a 2 × 2 ANOVA. The study revealed that the source of protein (plant vs. animal) appears to shape consumers’ perception of the product as more eco-friendly (F (1.518) = 38.681, p < 0.001, η2 = 0.069), natural (F (1.518) = 15.518, p < 0.001, η2 = 0.029), and healthy (F (1.518) = 25.761, p < 0.001, η2 = 0.047). Moreover, labelling including a “high-protein” Nutrition Claim increases the willingness to consume the product (F (1.518) = 4.531, p = 0.034, η2 = 0.009), and provides the impression of it being more eco-friendly (F (1.518) = 6.658, p = 0.01, η2 = 0.012) and of a higher quality (F (1.518) = 7.227, p = 0.007, η2 = 0.014). The obtained results may have theoretical significance by improving the understanding of factors determining the perception of food products and the use of meat substitutes.

Olfactory and gustatory disorders caused by COVID-19: How to regain the pleasure of eating?

Background

Recently, anosmia and ageusia (and their variations) have been reported as frequent symptoms of COVID-19. Olfactory and gustatory stimuli are essential in the perception and pleasure of eating. Disorders in sensory perception may influence appetite and the intake of necessary nutrients when recovering from COVID-19. In this short commentary, taste and smell disorders were reported and correlated for the first time with food science.

Scope and approach

The objective of this short commentary is to report that taste and smell disorders resulted from COVID-19 may impact eating pleasure and nutrition. It also points out important technologies and trends that can be considered and improved in future studies.

Key findings and conclusions

Firmer food textures can stimulate the trigeminal nerve, and more vibrant colors are able to increase the modulation of brain metabolism, stimulating pleasure. Allied to this, encapsulation technology enables the production of new food formulations, producing agonist and antagonist agents to trigger or block specific sensations. Therefore, opportunities and innovations in the food industry are wide and multidisciplinary discussions are needed.

Multiscale Approach to Dairy Products Design

Dairy products are among the most popular nutritious foods in the world. Understanding the relationship between the composition, process, and structural properties at different scales (molecular, microscopic, and macroscopic) is fundamental to designing dairy products. This review highlights the need to analyze this relationship from different scales as an essential step during product design through a multiscale approach.

Purple eggplant and zucchini color, mechanical properties, mastication, and sensory perception influenced by boiling and grilling

The present study investigated the influence of boiling and grilling deployed at 15, 30, and 45 min on selected eggplant and zucchini qualities. The colorants present in these vegetables contribute to their attractive appearance while presenting health-benefit components. This study shows that boiling and grilling differently affected the color properties of the eggplant and zucchini flesh and skin, leading to discoloration. However, the multifactorial mechanisms behind this phenomenon are not yet fully uncovered. Both boiling and grilling caused softening in examined vegetables within cooking prolongation, but different effects were observed. In the case of grilling, large- and small-deformation mechanical parameters established higher values. Thus, grilling produced firmer samples, which was further projected on mastication and dynamic sensory perception. Although there was limited differentiation in mastication parameters, it was observable that grilled products were more mastication-demanding. The number of chews and consumption time provided most of the information and established higher values for short-time cooking treatments and grilling. As a consequence, samples that had longer in-oral exposure times were perceived as bitter (eggplant) or sweet (zucchini). Oppositely, boiled vegetables were juicier. Regardless of the type of vegetable or cooking method, the shortest cooking treatments resulted in products dominantly perceived as firm.

Ease of mastication index-Quantification of mastication effort using quality function deployment

An effort required to masticate a bite of food seems important for a broad group of consumers considering many foodstuffs. Consumers with specific needs (elderly, people with impaired oral functioning) are also interested in ease of mastication. Besides understanding the relationships between mastication and sensory perception, a better insight into foodstuffs' mastication effort is needed to gain vital information when choosing the food and judging its quality. However, there is not much work describing the quantification of mastication effort as a quality grade. Within this research, we: (a) analyzed consumers' demands toward mastication attributes, (b) examined mastication, mechanical, and sensory parameters for nine foodstuffs (meat and dairy products), and (c) developed a quality function deployment model that connects consumers' demands with a multidimensional technical scale, enabling mastication effort quantification through a novel "ease of mastication index" (EMI). As a single-value quality score, EMI answers how much effort must be applied to masticate certain foodstuff. It is a left-sided index (it can have only positive values up to EMI = 1), having the maximal value for creamy cheese (0.96) and minimal (0.40) for fermented sausage in the present study, meaning the latter was the most difficult case study product for mastication. This study's practical application may be seen in the proposed model usage for foodstuffs research and development, bearing in mind ease of mastication. EMI may play an essential role as a novel quality indicator that can be considered crucial for broad and specific consumer groups.

Effect of micro-aeration on the mechanical behaviour of chocolates and implications for oral processing

Aeration in foods has been widely utilised in the food industry to develop novel foods with enhanced sensorial characteristics. Specifically, aeration at the micron-sized scale has a significant impact on the microstructure where micro-bubbles interact with the other microstructural features in chocolates. This study aims to determine the effect of micro-aeration on the mechanical properties of chocolate products, which are directly correlated with textural attributes such as hardness and crumbliness. Uniaxial compression tests were performed to determine the mechanical properties such as Poisson's ratio, Young's modulus and macroscopic yield strength together with fracture tests to estimate the fracture toughness. In vivo mastication tests were also conducted to investigate the link between the fracture properties and fragmentation during the first two chewing cycles. The uniaxial stress-strain data were used to calibrate a viscoplastic constitutive law. The results showed that micro-aeration significantly affects mechanical properties such as Young's modulus, yield and fracture stresses, as well as fracture toughness. In addition, it enhances the brittle nature of the chocolate, as evidenced by lower fracture stress but also lower fracture toughness leading to higher fragmentation, in agreement with observations in the in vivo mastication tests. As evidenced by the XRT images and the stress-strain measurements micro-aeration hinders the re-arrangement of the microscopic features inside the chocolate during the material's deformation. The work provides a new insight of the role of bubbles on the bulk behaviour of complex multiphase materials, such as chocolates, and defines the mechanical properties which are important input parameters for the development of oral processing simulations.

Exploring the potential of polysaccharides or plant proteins as structuring agents to design cheeses with sensory properties focused toward consumers in East and Southeast Asia: a review

The focus of the global cheese industry on accessing new markets for cheese is currently driving a greater need for innovation in cheese products. Research to date suggests that, for example, East Asian consumers prefer cheeses that have a soft texture, with mild and milky flavors. Strategies for achieving such cheese characteristics are reviewed in this article. For example, incorporation of polysaccharides into cheese results in cheese with higher moisture levels and softer textures; this also results in modification of other properties such as adhesiveness, meltability and flavor release. Hydrated polysaccharides may be considered as filler particles within cheese matrices, and therefore filled gel models with suitable filler particles can be used to establish the effect of filler volume, size and surface properties on the fractural and rheological properties of cheese matrices, thus guiding the use of polysaccharides. Addition of plant proteins such as soy and pea protein can also result in cheeses with softer texture. Furthermore, it has been suggested that heat-induced gelation of soy or pea protein with casein results in a gel structure consisting of two independent protein gels, thus facilitating the design of bespoke structures by adjusting the ratio of the two proteins. Finally, it is proposed that incorporation of ingredients with sensory properties familiar to East and Southeast Asian consumers and with the capacity to achieve bespoke textures offer potential for the development of cheese products for consumers in these markets.

Critical review of sensory texture descriptors: From pureed to transitional foods for dysphagia patients

Dysphagic people need to change their diet to avoid pain or risk of choking. For example, they can eat texture modified foods (including pureed and transitional foods, that is, food that start with one texture and change into another because of moisture or heating). Simple testing methods proposed by the IDDSI initiative can be performed to characterize texture modified food but these methods are not always relevant for understanding oral texture and mouthfeel properties. Sensory characterization is essential to develop or optimize a food product and to meet consumer's expectations and needs especially for dysphagic persons. However, sensory methods and texture descriptors are complex to target and evaluate for different severity of dysphagia. Sensory texture descriptors can be determined by different methods and assessed in different ways. This review is useful for listing the sensory methods used to generate sensory descriptors to characterize the oral texture of cereal and pureed foods. We found that 55% of the reviewed publications used specific oral texture descriptors and that 17 descriptors could be identified as the most used and relevant for all the products studied (sticky), for pureed (e.g., cohesiveness, floury, and soft) and for cereal-based foods (e.g., hard, fatty, and crispy). These results should be considered to facilitate the choice of sensory texture descriptors in future studies on pureed and transitional foods such as cereal-based foods according to the IDDSI level. This review also demonstrates that it is difficult to find a consensus between studies using different evaluation methods for the same descriptor.