Extruded Maize Flour as Texturizing Agent in Acid-Unheated Skim Milk Gels

Starches have been used to improve the textural properties, substitute fats or increase satiety in yoghurts and acidified milk gels, however studies involving addition of flours are scarce. The objective of this study was to analyze the effect of skim milk substitution by pregelatinized extruded maize flour on the acidification process (changes in pH and rheology), textural properties, syneresis and microstructure of acidified milk gels (15% w/w solids). To this end, pregelatinized flour was used to replace 17, 33 and 50% of the skim milk powder. A greater proportion of flour resulted in a faster acidification process and a higher pH at the gelation point, indicating a faster gelation. The substitution of milk by flour up to 33% increased the firmness and consistency of the set gel, but these changes were reversed with greater substitution levels due to the lack of a connected protein structure. In addition, a greater syneresis of the gels was observed as the milk content was reduced, an effect that was reversed by increasing the percentage of solids in the mixture.European Regional Development Fund (FEDER)Spanish Ministry of Economy and Competitiveness (Project AGL2014-52928-C2

The Impact of Basil Seed Gum on Native and Pregelatinized Corn Flour and Starch Gel Properties

The effect of Basil Seed Gum (BSG) on native and pre-gelatinized corn starch and flour gels was evaluated. With this purpose, the hydration, pasting, rheological, textural and microstructural properties of the mixed gels were analyzed. Xanthan was used as a comparison, as it presents comparable high zero shear viscosity to BSG. The presence of BSG led to greater water binding capacity and greater water absorption index of the starch and flours compared to the free-gum systems. In general BSG substantially increased the peak and final viscosities of the pastes, also leading to a raise in the viscoelasticity (G’ and G”) and hardness of the final gels, native or treated (pregelatinized starch and extruded flour). A more opened microstructure—compared to a homogeneous and dense matrix of the control native starch gels— with strands and a spider-like network of BSG across the pockets was detected. On the other hand, xanthan showed the opposite effect, decreasing the peak and final viscosities of the native systems, delaying the gelatinization process, and also leading to weaker gels of reduced viscoelasticity with opened honeycomb-like microstructures. However, for pregelatinized flour and starch the effect of xanthan was minimal.Spanish Ministry of Economy and Competitiveness (Project AGL2014-52928-C2-2-R) and the European Regional Development Fund (FEDER

Probing hydrogen bond interactions in a shear thickening polysaccharide using nonlinear shear and extensional rheology

Mamaku gum is a polysaccharide extracted from the fronds of the black tree fern found in New Zealand. The cooked pith has traditionally been used for various medicinal purposes and as a food source by the Maori people of New Zealand. It has potential applications as a thickener in the food industry and as a palliative for patients with dysphagia. Studies on the shear rheology of Mamaku gum have revealed that the gum exhibits shear thickening at a critical shear rate due to a transition from intra- to inter-molecular chain interactions upon shear-induced chain elongation. In this paper, we demonstrate that these interactions are primarily due to hydrogen bonding. We perform extensional rheology on mixtures of Mamaku gum and urea (a known disruptor of hydrogen bonds) to quantify the nature of these interactions. Capillary Breakup Extensional Rheometry (CaBER) performed on the pure Mamaku gum solutions yield plateau values of the Trouton ratio as high as ∼10[superscript 4], showing that the viscoelasticity of the gum in uniaxial elongation is much higher than in shear. For all Mamaku concentrations tested, the extensional viscosity decreases upon increasing urea concentration. Furthermore, the relaxation time decreases exponentially with increasing urea concentration. This exponential relationship is independent of the Mamaku concentration, and is identical to the relationships between urea concentration and characteristic timescales measured in nonlinear shear rheology. We show using the sticky reptation model for polymers with multiple sticker groups along the backbone how such a relationship is consistent with a linear decrease in the free energy for hydrogen bond dissociation. We then demonstrate that a time-concentration superposition principle can be used to collapse the viscoelastic properties of the Mamaku-gum/urea mixtures.United States. National Aeronautics and Space Administration (Grant NNX09AV99G

Effect of Celluclast 1.5L on the Physicochemical Characterization of Gold Kiwifruit Pectin

The effects of Celluclast 1.5L concentration on the physicochemical characterization of gold kiwifruit pectin was evaluated. Varying the enzyme concentration affected the pectin yield and pectin physicochemical properties. The viscosity of extracted pectin was largely dependent on the enzyme concentration. Celluclast 1.5L with medium concentration exhibited the highest viscosity. Varying the enzyme concentration also influenced the molecular weight distribution. High molecular weight (Mw) pectin (1.65 × 106 g/mol) was obtained when the medium concentration was used. Overall, the study clearly reflects the importance of taking into consideration the amount of cellulytic enzyme added in order to determine the final quality of pectin

Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)

Effect of sugar type and concentration on the heat coagulation of oil-in-water emulsions stabilized by milk-protein concentrate.

The influence of various sugars, on the heat stability of a milk-protein-concentrate (MPC)-stabilized emulsion (10% w/w protein, 10% w/w oil) was studied. Regardless of concentration, the addition of sugars during emulsification slightly increased the droplet diameter except the addition of 20–30% w/w maltodextrin significantly (p \u3c 0.05) decreased the droplet diameter and was attributed to the larger change in disperse/continuous phase viscosity ratio. Generally, the addition of sugar reduced the heat coagulation time (HCT) determined at 140 °C. The increased concentration of glucose, maltose, sucrose, trehalose shifted the pH at heat stability maximum towards more acidic values whereas the increased concentration of maltodextrin shifted the pH at heat stability maximum towards more alkaline values. The extent of destabilization also varied between sugars, with trehalose being particularly effective in retaining the original heat stability of the MPC-stabilized emulsions. Reducing sugars (glucose, maltose, maltodextrin) decreased the heat stability maximum more significantly than non-reducing sugars (sucrose and trehalose). Particle size, microstructure, and rheological measurements showed good correlations with the heat stability. Several factors, including free calcium ion level, volume fraction of the continuous phase protein and solvent quality, will also affect the heat stability of MPC-stabilized emulsions with added sugars

Physical stability, microstructure and rheology of sodium-caseinate-stabilized emulsions as influenced by protein concentration and non-adsorbing polysaccharides.

We explored the stability and rheological properties of 30% oil-in-water emulsions stabilized with sodium caseinate (1–10% w/w). The dynamics of the formation of a transient droplet network were investigated using microstructure, rheology and creaming. The behaviour was classified into two types of depletion-flocculated caseinate emulsions: (1) emulsions with intermediate caseinate concentrations (1.5–4%) displayed rapid phase separation because of compaction of the flocculated networks; (2) emulsions with high caseinate concentrations (5–10%) displayed increased creaming stability, because the higher continuous phase concentration contributed to retarded formation of the viscous transient droplet network with stronger attractions. Small deformation rheology showed that the development of a transient droplet network depended markedly on the caseinate concentration. We distinguished between the contributions of the continuous phase viscosity and the depletion force by investigating the influence of maltodextrin and xanthan gum on the stability and rheology of 1.5% caseinate emulsions. Surprisingly, the droplet–droplet interactions were weakened by the addition of maltodextrin, and the stabilizing mechanism differed from the prediction that high zero shear viscosity is the dominant factor in preventing phase separation of a depletion-flocculated emulsion. We attributed the change in the depletion force to the change in caseinate particle size; a small change in caseinate size could have changed the depletion interaction potential moderately. Furthermore, the droplet rearrangements within the flocculated network played an important role in the stability of the emulsions, and were possibly influenced by both the strength of the depletion force and the continuous phase viscosity at high caseinate concentrations. Both depletion force and continuous phase viscosity increased with the addition of xanthan gum. The phase separation kinetics and the restabilization mechanisms were analogous to those of the caseinate system