A Review on the Relationships between Processing, Food Structure, and Rheological Properties of Plant-Tissue-Based Food Suspensions

Diet shapes the metabolite profile in the intact human ileum, which affects PYY release

The human ileum contains a high density of enteroendocrine L-cells, which release the appetite-suppressing hormones glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) in response to food intake. Recent evidence highlighted the potential role of food structures in PYY release, but the link between food structures, ileal metabolites, and appetite hormone release remains unclear owing to limited access to intact human ileum. In a randomized crossover trial (ISRCTN11327221; isrctn.com), we investigated the role of human ileum in GLP-1 and PYY release by giving healthy volunteers diets differing in fiber and food structure: high-fiber (intact or disrupted food structures) or low-fiber disrupted food structures. We used nasoenteric tubes to sample chyme from the intact distal ileum lumina of humans in the fasted state and every 60 min for 480 min postprandially. We demonstrate the highly dynamic, wide-ranging molecular environment of the ileum over time, with a substantial decrease in ileum bacterial numbers and bacterial metabolites after food intake. We also show that high-fiber diets, independent of food structure, increased PYY release compared with a low-fiber diet during 0 to 240 min postprandially. High-fiber diets also increased ileal stachyose, and a disrupted high-fiber diet increased certain ileal amino acids. Treatment of human ileal organoids with ileal fluids or an amino acid and stachyose mixture stimulated PYY expression in a similar profile to blood PYY concentrations, confirming the role of ileal metabolites in PYY release. Our study demonstrates the diet-induced changes over time in the metabolite environment of intact human ileum, which play a role in PYY release.

Binary Pea Protein-Psyllium Hydrogel: Insights into the Influence of pH and Ionic Strength on the Physical Stability and Mechanical Characteristics

Food hydrogels, used as delivery systems for bioactive compounds, can be formulated with various food-grade biopolymers. Their industrial utility is largely determined by their physicochemical properties. However, comprehensive data on the properties of pea protein-psyllium binary hydrogels under different pH and ionic strength conditions are limited. The aim of this research was to evaluate the impact of pH (adjusted to 7, 4.5, and 3) and ionic strength (modified by NaCl addition to 0.15 and 0.3 M) on the physical stability, color, texture, microrheological, and viscoelastic properties of these hydrogels. Color differences were most noticeable at lower pH levels. Inducing hydrogels at pH 7 (with or without NaCl) and pH 4.5 and 3 (without NaCl) resulted in complete gel structures with low stability, low elastic and storage moduli, and low complex viscosity, making them easily spreadable. Lower pH inductions (4.5 and 3) in the absence of NaCl resulted in hydrogels with shorter linear viscoelastic regions. Hydrogels induced at pH 4.5 and 3 with NaCl had high structural stability, high G' and G" moduli, complex viscosity, and high spreadability. Among the tested induction conditions, pH 3 with 0.3 M NaCl allowed for obtaining a hydrogel with the highest elastic and storage moduli values. Adjusting pH and ionic strength during hydrogel induction allows for modifying and tailoring their properties for specific industrial applications.

Rheological Characteristics of Wheat Dough Containing Powdered Hazelnuts or Walnuts Oil Cakes

This study assessed edible oil industry byproducts, oil cakes (OC) based on hazelnuts and walnuts (HOC, WOC), to replace wheat flour dough (WD) based on farinograph and extensograph parameters and rheological measurements. The research hypothesis of this work is that replacing part of wheat flour with ground nut oil cakes modifies the rheological characteristics of the dough. WF was replaced at the level of 5%, 10% and 15%. It was shown that use of OC in flour mixtures at various levels significantly influenced the rheological properties of the dough. The water absorption of wheat flour and oil cake mixtures was higher than that of the control sample, and the average value of this indicator was 53.4%. The control sample had the lowest dough development time (DDT), and the presence of HOC or WOC in the system resulted in a significant increase in this parameter (p < 0.05). The average DDT of WDHOC cakes was 4.7 min and was lower compared to WDWOC which was 5.9 min. The WDWOC10% and WDWOC15% samples were characterized by the highest dough stability value and the lowest degree of softening (p < 0.05). The presence of OC in the flour mixtures increased the values of the storage and loss moduli, which was reflected in the K' and K″ values. The values of these parameters also increased as the level of OC addition increased. WDHOC doughs were characterized by higher values of the K' and K″ parameters compared to WDWOC. The results of the creep and recovery test showed that the dough with the addition of nut OC was less susceptible to deformation compared to the control dough (p < 0.05). The resistance to deformation increased with the increasing share of HOC or WOC in the mixtures. The average value of viscoelastic compliance (J1) of this parameter for WDHOC dough was on average 1.8 × 10-4 Pa-1, and for WDWOC 2.0 × 10-4 Pa-1. Nut oil cakes are an interesting technological addition to the dough. Their use may have a positive impact on the characteristics of the finished product and expand their application possibilities in the food industry. This is because the dough with the addition of nut cakes was more stiff and less flexible and susceptible to deformation.

Comparison of the Rheological Behavior of Fortified Rye-Wheat Dough with Buckwheat, Beetroot and Flax Fiber Powders and Their Effect on the Final Product

This study was focused on the replacement of the part of the flour (10% w/w) in rye-wheat bread with three different botanical origin powders with a high dietary fiber content (buckwheat hulls, beetroot and flax powder). The dough was based on rye-wheat flour without and with the addition of fiber powders with different botanical origins and was tested, and the quality of the finished baked products made from those doughs were assessed. In order to characterize the flour mixtures, their basic parameters were determined, and their pasting characteristic was performed. The dough parameters were described by the Burger rheological model and also the creep and recovery test. On the other hand, in bread, the basic parameters of baking, crumb and crust color parameters were determined, and an analysis of the crumb texture was carried out. Additionally, a sensory analysis of the finished products was carried out. The applied fiber additives influenced the pasting characteristics of the tested rye-wheat flour and were influenced by the dough rheological properties. It was found that used fiber powders changed the quality parameters of the final products. Despite this, using fiber at the amount of 10% as a flour substitute allowed us to obtain bread of a similar quality to the control sample.

Uncovering the secrets of industrial hemp in food and nutrition: The trends, challenges, and new-age perspectives

Hemp is a valuable crop with a wide range of use, from applications in foods and textiles to pharmaceuticals. Over recent years, the use of hemp as food and food ingredients has drastically increased. The growth is driven by numerous health benefits hemp possesses and its wide range of applications in the food industry. This review provides the scientific literature concerning the benefits of industrial hemp in the food industry. The relevant historical context of use, recent applications in the food industry, health benefits, various development challenges, and the global market outlook for hemp-based food products have been analyzed. Evidence suggests that today hemp is widely consumed as food or an ingredient in the food. Hemp-based foods are marketed as having various health benefits, although their reception by target consumers and success varies. Besides, scientific research on hemp-derived foods has dramatically increased over recent years. Numerous in vitro and in vivo studies have investigated the health benefits of hemp-based foods. Therefore, there is a promising growth trend in producing novel foods from industrial hemp. Nevertheless, due to health concerns related to THC, there is a general need for regulatory compliance when integrating hemp into foods to ensure product safety before use.

Application of Optical and Rheological Techniques in Quality and Storage Assessment of the Newly Developed Colloidal-Suspension Products: Yogurt-Type Bean-Based Beverages

The objectives of this study were to compare the properties of the yogurt-type bean-based beverages B and BG produced from the nongerminated and germinated beans, respectively, by high-pressure homogenization (HPH) and fermentation with three starter cultures. Optical techniques were used to evaluate the particle size distribution (PSD), color parameters, and instability during storage, while rheological tests were used to evaluate the shear viscosity, flow behavior, and viscoelastic properties. The BG compared to B, irrespective of the starter culture used, showed a higher mean diameter and Span of PSD (d_4,3 ≈ 76.8-84.2, Span ≈ 2.24-2.35 for BG vs. d_4,3 ≈ 38.2-47.0, Span ≈ 1.90-2.00 for B). The BG vs. B showed lower viscosity (0.47 Pa·s for BG vs. 0.81 Pa·s for B at shear rate 75 s^-1) and slightly lower but satisfactory stability (after 21 days at 6 °C, the Turbiscan Stability Index TSI ≈ 1.3-2.0 for BG vs. TSI ≈ 0.6-0.9 for B). Both B and BG were characterized by light-yellow color and showed the characteristics of a viscoelastic fluid. The HPH and germination mainly affected the properties of the tested plant tissue, which has a direct impact on the properties of the final products.

Microstructural and Texturizing Properties of Partially Pectin-Depleted Cell Wall Material: The Role of Botanical Origin and High-Pressure Homogenization

In the current study, the texturizing properties of partially pectin-depleted cell wall material (CWM) of apple, carrot, onion and pumpkin, and the potential of functionalization by high-pressure homogenization (HPH) were addressed. This partially pectin-depleted CWM was obtained as the unextractable fraction after acid pectin extraction (AcUF) on the alcohol-insoluble residue. Chemical analysis was performed to gain insight into the polysaccharide composition of the AcUF. The microstructural and functional properties of the AcUF in suspension were studied before HPH and after HPH at 20 and 80 MPa. Before HPH, even after the pectin extraction, the particles showed a cell-like morphology and occurred separately in the apple, onion and pumpkin AcUF and in a clustered manner in the carrot AcUF. The extent of disruption by the HPH treatments at 20 and 80 MPa was dependent on the botanical origin. Only for the onion and pumpkin AcUF, the water binding capacity was increased by HPH. Before HPH, the texturizing potential of the AcUFs was greatly varying between the different matrices. Whereas HPH improved the texturizing potential of the pumpkin AcUF, no effect and even a decrease was observed for the onion AcUF and the apple and carrot AcUF, respectively.

Formulation engineering of food systems for 3D-printing applications - A review

The efficient development of extrusion-based 3D-printing requires flexibility in both formulation- and process design. This task requires a fundamental understanding of the influence of material rheological properties on the extrusion process. Within this review, a qualitative toolbox for food extrusion is presented which provides guidelines for the formulation and engineering of extrusion processes in general and 3D-printing in particular. The toolbox is based on current knowledge of highly viscous food systems and the influence of individual components on the overall rheology. It includes the efficiency of particle packing, microstructure and the influence of shear rate, as well as the formation of self-supporting structures by gelation of the liquid phase and crowding of particles. Physical laws and semi-empirical equations are discussed to describe the rheology and relate relevant theory to the extrusion process. Practical information is presented, including examples of extrusion and 3D-printing of food and non-food systems. The qualitative extrusion toolbox provides a general framework for the emerging field of extrusion-based 3D-printing of food products. It can be used to identify which specific material and process parameters can be changed and how they may be altered to optimize the 3D-printing process. The general framework will assist researchers, as well as industry.

Combined rotational and capillary rheomtery to determine slip coefficients and other rheological properties of orange pulp

The characterization of the rheological properties of orange pulp under typical processing temperatures is needed for the design and optimization of orange pulp processing systems. The flow of orange pulp produced slip at shear rates at ∼1 to 5 s^-1 . Rotational rheometry revealed that the flow behavior of orange pulp before slip occurrence followed the Power Law model for concentrations of ∼500 to 800 g/L at 4 to 80 °C. The consistency coefficient (K) ranged from 33 to 234 Pa·sⁿ and the flow behavior index n ranged from 0.18 to 0.24. Both, K and n decreased with temperature. While K fitted well an Arrhenius-like model, n best fitted a linear model. As concentration increased K increased linearly, while n was not significantly (P > 0.05) affected. The flow without slip was calculated using the Power Law parameters from rotational rheometry and the wall shear stress (σ_w ) from capillary rheometry for the experimental flow rates. This allowed calculating the corrected slip coefficient β_c and obviated the need for pipes with multiple diameters. β_c decreased by one order of magnitude when temperature increased from 4 to 50 °C when σ_w was 0.1 kPa. The effect was exacerbated with increased flow rate. Similarly, β_c increased by about one order of magnitude when pulp concentration increased from ∼550 to 850 g/L at 80 °C. The increase in β_c with temperature indicated that the effect of temperature in the consistency of the bulk was different from its effect on the consistency of the liquid phase near the pipe wall. PRACTICAL APPLICATION: Design and optimization of processes equipment and industrial handling systems of orange pulp require detailed knowledge of their rheological (flow) properties. Citrus pulp like fruit pastes and purees produce less friction than one would anticipate when they flow because the liquid fraction acts as a lubricant. This study presents an original method for such characterization and shows that wall slip is greatly affected by temperature and concentration.

Understanding the interplay between food structure, intestinal bacterial fermentation and appetite control

Epidemiological and clinical evidence highlight the benefit of dietary fibre consumption on body weight. This benefit is partly attributed to the interaction of dietary fibre with the gut microbiota. Dietary fibre possesses a complex food structure which resists digestion in the upper gut and therefore reaches the distal gut where it becomes available for bacterial fermentation. This process yields SCFA which stimulate the release of appetite-suppressing hormones glucagon-like peptide-1 and peptide YY. Food structures can further enhance the delivery of fermentable substrates to the distal gut by protecting the intracellular nutrients during upper gastrointestinal digestion. Domestic and industrial processing can disturb these food structures that act like barriers towards digestive enzymes. This leads to more digestible products that are better absorbed in the upper gut. As a result, less resistant material (fibre) and intracellular nutrients may reach the distal gut, thus reducing substrates for bacterial fermentation and its subsequent benefits on the host metabolism including appetite suppression. Understanding this link is essential for the design of diets and food products that can promote appetite suppression and act as a successful strategy towards obesity management. This article reviews the current evidence in the interplay between food structure, bacterial fermentation and appetite control.

Clustering of instrumental methods to characterize the texture and the rheology of slimy okra (Abelmoschus esculentus) suspensions

Okra (Abelmoschus esculentus) is one of the ingredients widely used in African gastronomy because of the unique slimy texture it gives to sauces. However, processing and formulation can affect the textural and rheological properties of these sauces, leading to unacceptable quality for the African consumer. The aim of this study was to select the instrumental measurements best enabling (a) characterization of the rheology and texture of slimy sauces prepared from okra and (b) monitoring its evolution during the preservation process. Thirty-seven slimy suspensions (sauces and purées) were measured with 16 rheological and textural parameters. A principal component analysis revealed that flow consistency index K and flow behavior index n were well correlated with visco-elastic, adhesive, and shear thinning properties, and that stringiness was well correlated with elongational, cohesive, and ductile properties. These two sets of measurement methods are sufficient to characterize their rheological and textural properties, and necessary to discriminate them according to their process and formulation.

Bolus rheology and ease of swallowing of particulated semi-solid foods as evaluated by an elderly panel

Preparation of a bolus is a complex process with both food comminution and degree of lubrication with saliva playing an important role in a safe swallow.

Cell Wall Polymer Composition and Spatial Distribution in Ripe Banana and Mango Fruit: Implications for Cell Adhesion and Texture Perception

Banana (Musa acuminata) and mango (Mangifera indica) are two of the most popular fruits eaten worldwide. They both soften during ripening but their textural attributes are markedly different. This study aimed to elucidate the molecular mechanism underpinning textural differences between banana and mango. We used a novel combination of methods at different scales to analyse the surface properties of fruit cells and the potential contribution of cells and cell wall components to oral processing and texture perception. The results indicated that cell separation occurred easily in both organs under mild mechanical stress. Banana cells showed distinctively elongated shapes with distinct distribution of pectin and hemicellulose epitopes at the cell surface. In contrast, mango had relatively spherical cells that ruptured during cell separation. Atomic force microscopy detected soft surfaces indicative of middle lamella remnants on banana cells, while mango cells had cleaner, smoother surfaces, suggesting absence of middle lamellae and more advanced cell wall disassembly. Comparison of solubilized polymers by cell wall glycome analysis showed abundance of mannan and feruylated xylan in separation exudate from banana but not mango, but comparable levels of pectin and arabinogalactan proteins. Bulk rheology experiments showed that both fruits had similar apparent viscosity and hence might be extrapolated to have similar "oral thickness" perception. On the other hand, oral tribology experiments showed significant differences in their frictional behavior at orally relevant speeds. The instrumental lubrication behavior can be interpreted as "smooth" mouthfeel for mango as compared to "astringent" or "dry" for banana in the later stages of oral processing. The results suggest that cell wall surface properties contribute to lubricating behavior associated with textural perception in the oral phase.

Combined Effects of Irrigation Regime, Genotype, and Harvest Stage Determine Tomato Fruit Quality and Aptitude for Processing into Puree

Industry tomatoes are produced under a range of climatic conditions and practices which significantly impact on main quality traits of harvested fruits. However, the quality of tomato intended for processing is currently addressed on delivery through color and Brix only, whereas other traits are overlooked. Very few works provided an integrated view of the management of tomato puree quality throughout the chain. To gain insights into pre- and post-harvest interactions, four genotypes, two water regimes, three maturity stages, and two processes were investigated. Field and glasshouse experiments were conducted near Avignon, France, from May to August 2016. Two irrigation regimes were applied: control plants were irrigated in order to match 100% of evapotranspiration (ETP); water deficit (WD) plants were irrigated as control plants until anthesis of the first flowers, then irrigation was reduced to 60 and 50% ETP in field, and glasshouse respectively. Fruits were collected at three stages during ripening. Their color, fresh weight, dry matter content, and metabolite contents were determined before processing. Pericarp cell size was evaluated in glasshouse only. Two laboratory-scaled processing methods were applied before structural and biochemical analyses of the purees. Results outlined interactive effects between crop and process management. WD hardly reduced yield, but increased dry matter content in the field, in contrast to the glasshouse. The puree viscosity strongly depended on the genotype and the maturity stage, but it was disconnected from fruit dry matter content or Brix. The process impact on puree viscosity strongly depended on water supply during fruit production. Moreover, the lycopene content of fresh fruit may influence puree viscosity. This work opens new perspectives for managing puree quality in the field showing that it was possible to reduce water supply without affecting yield and to improve puree quality.

Relationship between processing history and functionality recovery after rehydration of dried cellulose-based suspensions: A critical review

Cellulose-based suspensions have raised more and more attention due to their broad range of properties that can be used in paper industry and material science but also in medicine, nanotechnology and food science. Their final functionality is largely dependent on their processing history and notably the structural modifications that occur during drying and rehydration. The purpose of this work is to make a state-of-the-art contribution to the mechanisms involved in the process-structure-function relationships of cellulose-based hydrogels. The different assumptions that exist in the literature are reviewed taking the key role of the initial sample characteristics as well as the processing conditions into consideration. The decrease in swelling ability after drying is clearly due to an overall shrinkage of the structure of the material. At microscale, pore closure and cellulosic fibril aggregation are mentioned as the main reasons. The origins of such irreversible structural modifications take place at molecular level and is mainly explained by the establishment of a new balance of interactions between all components. Nevertheless, the respective contribution of each interaction are still under investigation.

Characterization and functional properties of mango peel pectin extracted by ultrasound assisted citric acid

Pectin was extracted from 'Tainong No. 1' mango peels, using a chelating agent-citric acid as extraction medium by ultrasound-assisted extraction (UAE) and conventional extraction (CE) at temperatures of 20 and 80°C. Chemical structures, rheological and emulsifying properties of mango peel pectins (MPPs) were comparatively studied with laboratory grade citrus pectin (CP). All MPPs exhibited higher protein content (4.74%-5.94%), degree of methoxylation (85.43-88.38%), average molecular weight (Mw, 378.4-2858kDa) than the CP, but lower galacuronic acid content (GalA, 52.21-53.35%). CE or UAE at 80°C resulted in significantly higher pectin yield than those at 20°C, while the extraction time for UAE-80°C (15min) was significantly shorter compared to CE-80°C (2h) with comparable pectin yield. Moreover, MPPs extracted at 80°C were observed with higher GalA and protein content, higher Mw, resulting in higher viscosity, better emulsifying capacity and stability, as compared to those extracted at 20°C and the CP. Therefore, these results suggested that MPPs from 'Tainong No. 1' may become a highly promising pectin with good thickening and emulsifying properties, using ultrasound-assisted citric acid as an efficient and eco-friendly extraction method.

Filler functionality in edible solid foams

We review the functionality of particulate ingredients in edible brittle foams, such as expanded starchy snacks. In food science and industry there is not a complete awareness of the full functionality of these filler ingredients, which can be fibers, proteins, starch granules and whole grains. But, we show that much can be learned about that from the field of synthetic polymeric foams with (nano)fillers. For edible brittle foams the enhancement of mechanical strength by filler ingredients is less relevant compared to the additional functionalities such as 1) the promotion of bubble nucleation and 2) cell opening-which are much more relevant for the snack texture. The survey of particulate ingredients added to snack formulations shows that they cannot be viewed as inert fillers, because of their strong hygroscopic properties. Hence, these fillers will compete with starch for water, and that will modify the glass transition and boiling point, which are important factors for snack expansion. Filler properties can be modified via extrusion, but it is better if that processing step is decoupled from the subsequent processing steps as mixing and expansion. Several filler ingredients are also added because of their nutritional value, but can have adverse effect on snack expansion. These adverse effects can be reduced if the increase of nutritional value is decoupled from other filler functionality via compartmentalization using micropellets.