Phase separation, antiplasticization and moisture sorption in ternary systems containing polysaccharides and polyols

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.

Current Positron Studies on the Modifications of the Molecular Packing in Green-Based Polymers Through Changes in the Synthesis Procedures or Environmental Conditions

The sensitivity of positron annihilation characteristics to changes in the molecular packing in network-forming polymers has been demonstrated since the early 1980s. Positron annihilation lifetime spectroscopy (PALS) is a unique technique that can provide direct information on the free volume in polymers through the experimental parameters of the free volume hole distribution, their mean value, and volume fraction. This knowledge is currently applied for PALS investigations on the main processes that govern the molecular organization in some green polymers when subjected to different synthesis procedures or environmental conditions (humidity, physical aging, temperature). In this article, which includes a wide repertoire of works published in the last two decades, results of PALS studies on eco-sustainable polymer systems based on starch, chitosan, or vegetable oils, are analyzed and discussed. Many examples are taken from the direct experience of the authors.

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.

The Glass Transition Temperature of Heterogeneous Biopolymer Systems

Biopolymers are abundant, renewable, and biodegradable resources. However, bio-based materials often require toughening additives, like (co)polymers or small plasticizing molecules. Plasticization is monitored via the glass transition temperature versus diluent content. To describe this, several thermodynamic models exist; nevertheless, most expressions are phenomenological and lead to over-parametrization. They also fail to describe the influence of sample history and the degree of miscibility via structure-property relationships. We propose a new model to deal with semi-compatible systems: the generalized mean model, which can classify diluent segregation or partitioning. When the constant k_GM is below unity, the addition of plasticizers has hardly any effect, and in some cases, even anti-plasticization is observed. On the other hand, when the k_GM is above unity, the system is highly plasticized even for a small addition of the plasticizer compound, which indicates that the plasticizer locally has a higher concentration. To showcase the model, we studied Na-alginate films with increasing sizes of sugar alcohols. Our k_GM analysis showed that blends have properties that depend on specific polymer interactions and morphological size effects. Finally, we also modeled other plasticized (bio)polymer systems from the literature, concluding that they all tend to have a heterogeneous nature.

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.

Understanding functionality of sucrose in cake for reformulation purposes

We review the functionality of sucrose during the manufacture of cakes from the perspective of sugar replacement. Besides providing sweetness, sucrose has important functionalities concerning structure formation. These functionalities also need to be mimicked in reformulated cakes. First, we review the hypotheses, concerning the development of structure and texture of cakes 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 cake during manufacturing in a supplemented state diagram, which indicates the important phase transitions occurring during baking. From the analysis, we have learned that sucrose act both as a plasticizer and as a humectant, modifying the phase transitions of biopolymers, dough viscosity, and water activity. If sugar replacers exactly mimick this behavior of sucrose, similar textures in reformulated cakes can be obtained. Physical theories exist for characterizing the plasticizing and hygroscopic behavior of sugars and their replacers. We have shown that the starch gelatinization and egg white denaturation can be predicted by the volumetric density of hydrogen bonds present in the solvent, consisting of water, sugar or its replacers, such as polyols or amino-acids.

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties

Antiplasticization of glassy polymers, arising from the addition of small amounts of plasticizer, was examined to highlight the developments that have taken place over the last few decades, aiming to fill gaps of knowledge in the large number of disjointed publications. The analysis includes the role of polymer/plasticizer molecular interactions and the conditions leading to the cross-over from antiplasticization to plasticization. This was based on molecular dynamics considerations of thermal transitions and related relaxation spectra, alongside the deviation of free volumes from the additivity rule. Useful insights were gained from an analysis of data on molecular glasses, including the implications of the glass fragility concept. The effects of molecular packing resulting from antiplasticization are also discussed in the context of physical ageing. These include considerations on the effects on mechanical properties and diffusion-controlled behaviour. Some peculiar features of antiplasticization regarding changes in Tg were probed and the effects of water were examined, both as a single component and in combination with other plasticizers to illustrate the role of intermolecular forces. The analysis has also brought to light the shortcomings of existing theories for disregarding the dual cross-over from antiplasticization to plasticization with respect to modulus variation with temperature and for not addressing failure related properties, such as yielding, crazing and fracture toughness.