Moisture sorption in mixtures of biopolymer, disaccharides and water

Decoupling texture from nutritional composition in sugar and fat reduced pound cake: A physico-chemical approach to bakery formulations

Reducing sugars and fats in cakes often compromises sensory properties, limiting consumer acceptance. This study proposes that the textural changes from 30% fat replacement (using dietary fibres) can be balanced by adjusting the water-sugar mixture properties through a concurrent 30% sugar replacement. Specifically, key physico-chemical parameters were investigated to design cake reformulation: (i) the volumetric density of hydrogen bonds, Φw,eff, affecting protein denaturation and starch gelatinization; (ii) the molar volume density of effective hydroxyl groups in the sugar molecules, NOH,s/vs, influencing starch pasting properties; (iii) the Flory-Huggins water interaction parameter, χeff, describing the hygroscopic properties of sugar mixtures; and (iv) the volume fraction of flour, Φflour. These parameters were independently varied and tested against phase transitions, dough rheology (temperature sweeps) and cake properties. Results indicated that all physico-chemical parameters (Φw,eff, NOH,s/vs, χeff, and Φflour) effectively described key physical properties associated with phase transitions and batter rheology during heating, as well as final cake properties. Biopolymer phase transitions and the viscoelastic behavior of batters were primarily governed by Φw,eff, while cake properties depended on all physico-chemical parameters combined. Sensory tests with naïve consumers confirmed that properly modulating these parameters yielded cakes with sensory attributes comparable to the reference. Notably, cakes with enhanced sweetness, softness, and moistness were achieved despite the 30% sugar and fat reduction, positively influencing liking. Overall, this study highlights a formulation strategy that decouples texture from nutritional composition, enabling improved sensory properties while lowering calorie density.

Soluble fibres modulate dough rheology and gluten structure via hydrogen bond density and Flory-Huggins water interaction parameter

Soluble fibres are gaining increasing interest for functional food applications like bread, but their interaction with gluten and effects on dough rheology are not fully elucidated. This study hypothesized that soluble fibres influence gluten structure and dough rheology by acting as plasticizers and humectants. Plasticizing properties depend on the effective number of hydrogen bonding sites available in the fibre molecule (N OH,s ). Humectant properties are related to the water interaction parameter derived from analysis of the sorption behaviour. Oligo-fructoses, inulins, polydextrose and a glucose syrup were added individually and in mixtures to wheat dough to test the hypothesis. PCA and multi-linear regressions showed that the G' from temperature sweeps increased with an increase in the effective volume fraction of hydrogen bonding sites (Φ w , e f f ) in the solvent and in the water interaction parameter (χ eff ). The enhanced G' corresponded to a reduction in tan(δ), indicating an increased elastic behaviour. The parametersΦ w , e f f and χ eff also explained the changes in phase transitions during heating, i.e. Tonset and Tpeak of starch gelatinization (R2 > 0.9). Image analysis of the gluten network revealed that fibre structure and physico-chemical properties influenced the gluten network by altering branching rate, lacunarity, and protein strand width. Comparing inulins and polydextrose of similar molecular weights (Mw) indicated that interactions with gluten were influenced more by N OH,s than Mw. High Mw inulins, with a linear structure, promoted junctions in the gluten network through hydrogen bonds, and possibly phase separation in gluten-rich and inulin-rich phases. In contrast, the more hydrophilic, branched polydextrose reduced junction formation in the gluten network due to fewer N OH,s . This study provides new insights into the physico-chemical properties of soluble fibres and their role in wheat dough functionality.

Recent advances in carbohydrate phase behavior and rheology

The past decades have seen major advances in the understanding of the role of phase and state transitions of food carbohydrates on the behavior during processing and on product characteristics. Specifically, the awareness of the importance of the glass transition temperature and the plasticization by water and its study for a variety of food system is having major impact on the formulation and processing of foods, and in defining shelf-life conditions. This has led to the use of phase and state diagrams in the analysis and prediction of the behavior of food systems during processing and storage. This review first summarizes the current understanding of the food carbohydrate phase behavior and rheology, with emphasis on the concentrated states close to the glass transition and in the glassy state. Several pertinent topics, including the modeling of the rheological properties close to the glass transition, the strongly non-linear diffusion of water in the rubbery and glassy states, the aging and antiplasticization of glassy carbohydrate matrices, and consequences of amorphous-amorphous phase separation for the behavior of carbohydrate blends in concentrated states are discussed. Applications in food processing and product development are discussed, including the spray drying and freeze drying, powder agglomeration of food powders, powder caking, encapsulation, baked goods, crystallization and extrusion.

Interactions in plasticizer mixtures used for sugar replacement

In our quest for novel ingredients to be used in sugar replacement strategies, we have investigated the thermodynamics of polycarboxylic acids, such as citric acid. We have demonstrated the applicability of the Flory-Huggins (FH) theory to describe the thermodynamics of polycarboxylic acids solutions. Moreover, for citric acid we can describe the complete phase diagram with the theory. It shows that polycarboxylic acids have similar plasticizing and hygroscopic properties as sugars and polyols. Regarding mixtures of polycarboxylic acids and carbohydrates, the FH theory is able to describe a) the water activity of the mixtures, b) the solubility of ternary mixtures of acids and sugars, c) the lowering of the deliquescence point for binary mixtures of crystals, and d) the melting point depression in eutectic mixtures. Unexpectingly, our investigations show there is a strong non-zero FH interaction parameter between carboxylic acids and carbohydrates. In our prior sugar replacement strategy we have assumed zero interactions between plasticizers. Here, we will readdress this assumption. Carefull investigations of solid-liquid equilibrium of eutectic mixtures involving polycarboxylic acids and/or carbohydrates, shows nearly zero interaction in eutectic mixtures consisting only of two carbohydrates or two polycarboxylic acids. We now hold the hypothesis that there is strong non-zero interaction if the mixture contains plasticizers strongly differing in the amount of hydrogen bonding groups. This strong interaction explains why these mixtures, like polycarboxylic acids and carbohydrates, are excellent candidates as deep eutectic solvents. Furthermore, we conclude that polycarboxylic acids are useful additions to the toolbox of sugar replacers, albeit that there are some limitations to their amounts used.

Dry Heating of Cowpea Flour below Biopolymer Melting Temperatures Improves the Physical Properties of Bread Made from Climate-Resilient Crops

Improving the technological functionality of climate-resilient crops (CRCs) to promote their use in staple foods, such as bread, is relevant to addressing food and nutrition security in Africa. Dry heating of cowpea flour (CPF) was studied as a simple technology to modulate CPF physicochemical properties in relation to bread applications. For this purpose, the melting behavior of cowpea starch and proteins in CPF was first studied and modeled using Flory–Huggins theory for polymer melting. Next, dry-heating conditions were investigated based on the predicted biopolymer melting transitions in CPF to be well below starch and protein melting. The pasting properties (i.e., peak viscosity, final viscosity, breakdown and setback) of CPF could be selectively modulated depending on temperature-time combinations without altering the thermal behavior (i.e., melting enthalpies) of CPF. Water-binding capacity and soluble solids decreased with the increased severity of the temperature-time combinations. Dry-heated CPF added to CRC-based bread significantly improved crumb texture. In particular, dry heating at 100 °C for 2 h provided bread with the highest crumb softness, cohesiveness and resilience. The positive effects on the crumb texture could be largely related to enhanced starch integrity, as indicated by a reduction in breakdown viscosity after treatment. Overall, dry heating of CPF under defined conditions is a promising technology for promoting the use of CPF as a techno-functional and protein-rich ingredient in bread-type products.

A Systematic Comparison of the Intrinsic Properties of Wheat and Oat Bran Fractions and Their Effects on Dough and Bread Properties: Elucidation of Chemical Mechanisms, Water Binding, and Steric Hindrance

This study aimed at elucidating the contribution of chemical interactions, water binding, and steric hindrance on the effect of wheat and oat brans and of their fractions, i.e., soluble and insoluble, on dough and bread properties. For such purpose, an inert filler, i.e., glass beads of comparable particle size and with no water binding capacity and moisture sorption properties, was also studied. The glass beads provided breads most similar to the control, indicating the limited role of steric hindrance. Brans and bran fractions showed distinct compositional and physical properties. The soluble fraction from oat bran, rich in β-glucan, was less hygroscopic than the wheat counterpart and could bind more water, resulting in larger detrimental effects on bread quality. The β-glucan content showed a prevalent role in affecting gluten development, the thermo-setting behaviour of the dough, and crumb texture, i.e., cohesiveness and resilience. Overall, the comparison between the two brans and their fractions indicated that the interplay between water binding, mainly provided by the insoluble fraction, and the plasticizing properties of the soluble bran fraction controlled the effects on bread volume and texture. From a compositional standpoint, β-glucan content was a determining factor that discriminated the effects of wheat and oat brans.

Theoretical investigation of the swelling of polysaccharide microgels in sugar solutions

In this paper, we explain the increased swelling of crosslinked polysaccharide microgels by the increase of sugar concentration using a modified Flory-Rehner theory. This theory is validated via the investigation of the swelling of dextran microgels in sugar solutions, which can be viewed as a model system for crosslinked starch in sugar solution and custard. An essential part of our modified theory is that starch perceives the sugar solution as an effective solvent rendering a certain hydrogen bond density. Our simulations show that the often experimentally observed maximum in swelling of starch at 20% sugar concentration is probably due to the fact that equilibrium is not reached within practical time scales. Also, we discuss the use of our theory as a tool in sugar reformulation issues of custard. From simulation results one can produce a state diagram showing which formulations render a creamy, space-filling network.

Predicting the solubility of mixtures of sugars and their replacers using the Flory-Huggins theory

In this paper we investigate whether the Flory-Huggins theory can describe the thermodynamics of solutions of simple carbohydrates, like sugars and polyols. In particular, we focus on the description of the solubility of the carbohydrates in water. This is investigated for both binary and ternary mixtures, having two types of these carbohydrates. This research question arises especially in the case of bakery products, where one seeks to replace sucrose with other simple carbohydrates - which are often polyols. Based on the model parameters obtained from fitting the theory to the experimental data of binary solutions, we show that the theory can predict (a) solubility data for ternary mixtures, over a broad range of concentrations and temperatures, and (b) the deliquescence point of binary mixtures of carbohydrate crystals as a function of temperature. The theory can even be applied to carbohydrates, which form hydrate crystals. Together with our earlier theories on the thermodynamics of complex food mixtures, we have now a complete thermodynamic framework to describe the phase and state transitions of food materials as confectionery and bakery products, where the question of sucrose replacement is urgent.

Understanding functionality of sucrose in biscuits for reformulation purposes

We review the functionality of sucrose during the manufacture of biscuits from the perspective of sugar replacement. Besides to providing sweetness, sucrose has important functionalities concerning structure and texture formation. These functionalities also need to be mimicked in reformulated biscuits. First, we review the hypotheses concerning the development of structure and texture of biscuits during manufacturing, which are conveniently summarized in a qualitative way using the Complex Dispersed Systems methodology. Subsequently, we represent the changes of the state of the biscuit during manufacturing in the supplemented state diagram, which indicates the important phase transitions occurring during mixing and baking. We propose that when reformulated biscuits follow similar paths in the state diagram, similar structures and textures can be obtained. Physical theories exist for predicting these phase transitions for existing sucrose-rich biscuits and also reformulated biscuits containing extensive sweeteners as sugar replacers. More accurate predictions of structure and texture can be eventually obtained if they are combined with computational models, including heat and moisture transfer.

Understanding the influence of buckwheat bran on wheat dough baking performance: Mechanistic insights from molecular and material science approaches

A molecular and material science approach is used to describe the influence of coarse and fine buckwheat bran on wheat dough properties and bread textural quality. Focus is given on (i) gluten solvation and structural arrangements in presence of bran as studied by front-face fluorescence; (ii) thermo-mechanical behavior of dough during heating studied by dynamic mechanical thermal analysis and (iii) texture of bread crumb analyzed in terms of a cellular solid. The thermo-mechanical behavior of dough was found to be largely related to starch phase transitions during heating. The use of thermodynamic approaches to biopolymer melting revealed that key transitions such as the onset of starch gelatinization were function of the interplay of water and bran volume fractions in the dough. Front-face fluorescence studies in wheat dough revealed that gluten solvation and structural arrangements were delayed by increasing bran addition level and reduction in particle size, as indicated by the drastic decrease in the protein surface hydrophobicity index. Variations in gluten structure could be strongly related to dough baking performance, i.e. specific volume. With regards to texture, the approach revealed that crumb texture was controlled by variations in density, moisture and bran volume fractions. Overall, this study elucidates a number of physical mechanisms describing the influence of buckwheat bran addition to dough and bread quality. These mechanisms strongly pointed at the influence of bran on water partitioning among the main polymeric components. In the future, these mechanisms should be investigated with bran material of varying source, composition and structure.

Multiscale analysis of structure development in expanded starch snacks

In this paper we perform a multiscale analysis of the food structuring process of the expansion of starchy snack foods like keropok, which obtains a solid foam structure. In particular, we want to investigate the validity of the hypothesis of Kokini and coworkers, that expansion is optimal at the moisture content, where the glass transition and the boiling line intersect. In our analysis we make use of several tools, (1) time scale analysis from the field of physical transport phenomena, (2) the scale separation map (SSM) developed within a multiscale simulation framework of complex automata, (3) the supplemented state diagram (SSD), depicting phase transition and glass transition lines, and (4) a multiscale simulation model for the bubble expansion. Results of the time scale analysis are plotted in the SSD, and give insight into the dominant physical processes involved in expansion. Furthermore, the results of the time scale analysis are used to construct the SSM, which has aided us in the construction of the multiscale simulation model. Simulation results are plotted in the SSD. This clearly shows that the hypothesis of Kokini is qualitatively true, but has to be refined. Our results show that bubble expansion is optimal for moisture content, where the boiling line for gas pressure of 4 bars intersects the isoviscosity line of the critical viscosity 10(6) Pa.s, which runs parallel to the glass transition line.