Ioannis S. Chronakis

On the Molecular Characteristics, Compositional Properties, and Structural-Functional Mechanisms of Maltodextrins: A Review

Compositional, physicochemical, and structural properties of maltodextrins and the most important advances that have been made are critically reviewed. Individual topics focuses on the maltodextrin production, carbohydrate composition, and dextrose equivalent determination, factors that alter the polysaccharide properties, the molecular arrangement, the mechanisms and complex physicochemical changes of maltodextrins such as water interaction (hygroscopicity, precipitation, turbidity, bound and free water) and the role of molecular interactions for a network formation. Of particular importance is the information concerning the network structure of maltodextrins gels (degree of crystallinity, crystallite size, aggregation) and the involvement of linear and branched chains for the network formation. Rheological properties have become a desirable tool to predict and understand their structural and functional properties, in single and in mixed systems with other macromolecules. These advances are assessed together with the structural development of food products and processes. Their main food applications, particular advantages, recent commercial directions, and modifications together with potential problems are also discussed. As food ingredients, maltodextrins are a valuable production tool, but still with considerable promises. Nevertheless, a more detailed knowledge of the properties of maltodextrins is necessary in order for their use to be considered as sufficiently effective and desirable in a number of known food applications and for novel development purposes.

The behaviour of protein preparations from blue-green algae (Spirulina platensis strain Pacifica) at the air/water interface

Abstract The surface tension of a protein sample isolated from the blue-green algae (cyanobacteria) Spirulina platensis strain Pacifica was studied using the Wilhelmy plate method. The isolated material was characterised by determining the protein and lipid content, SDS-PAGE electrophoresis, isoelectric focusing, and visible spectroscopy. The protein is capable of reducing the interfacial tension at the aqueous/air interface already at relatively lower bulk concentrations compared to common food proteins. The surface tension of the protein preparation seems to be quite independent of pH, which indicates that electrostatic interactions are of minor importance for the interfacial behaviour. We have also separated out fractions with different interfacial properties by centrifugation. When the protein was spread at the air/aqueous interface, the pressure area isotherm somewhat resembles those recorded for lipids, with a higher collapse pressure than usually observed for proteins. The interfacial behaviour of extracted lipids confirms that remaining traces of lipids in protein powder have only a minor influence on the surface activity of Spirulina protein. The surface-active components are likely to be protein and/or protein-pigment complexes rather than individual protein molecules.

Rheology of kappa-carrageenan in mixtures of sodium and cesium iodide : two types of gels

Abstract Recent studies on dilute solutions (Borgstrom et al. (1996), Int. J. Biol. Macromol. 18 , 223) have shown that kappa-carrageenan helices associate into superhelical rigid rods in mixed 0.1 M aqueous solutions of NaI and CsI above a critical mole fraction ( x Cs = 0.4) of Cs. This work concerns the temperature-dependent rheology of more concentrated systems in mixed and pure solutions of the same salts. Gels with low moduli were even found in NaI alone, although this salt is known to impede the gelation of kappa-carrageenan, but only above 0.9% (w/w) of carrageenan. These gels were reminiscent of iota-carrageenan gels in two respects: the (low) magnitude of the shear storage modulus ( G ′), and the absence of hysteresis in the sol-gel transition. On the other hand, both the threshold concentration for gelation and the ratio between the loss and storage moduli were substantially higher for the kappa-carrageenan gels in NaI. In mixed solutions of CsI and NaI, two types of kappa-carrageenan gels could be distinguished, depending on the cesium content. The transition occurred at x Cs = 0.4, as in the previous studies on dilute solutions. Below x Cs = 0.4, the gels were similar to those in NaI alone. Above x Cs = 0.4, the gels were similar to ‘conventional’ kappa-carrageenan gels, formed in salts such as KC1: a pronounced thermal hysteresis appeared in the sol-gel transition, the gels showed tendencies for syneresis, and G ′ increased dramatically with increasing cesium content.

Biosolar proteins from aquatic algae

Publisher Summary There is little doubt that algae could be produced in industrial quantities and that the harvested proteins could find a ready market as a human foodstuff. Moreover, as animal proteins are scarce and expensive, a great deal of attention could be given to the alternative protein supplies, also in relation to the population growth of the world. This chapter introduces the apparent biochemical, physicochemical, nutritional, and technological value of the biosolar algae proteins as indicated by both chemical composition and available feeding trials. This chapter focuses on the future prospects for algae proteins as food macromolecules, but some important aspects of other algae biomolecules and recent knowledge in phototrophic algae are briefly introduced. Some already existing food applications of algae and algae protein functions are also addressed. The brief exploration of this chapter is restricted to edible algae vegetables that can be used for direct consumption or as ingredients for the food industry.

Specific Methods for the Analysis of Identity and Purity of Functional Food Polysaccharides

Publisher Summary All foods with few exceptions contain biopolymers— namely, polysaccharides and proteins, occurring either as natural constituents of edible living tissues (e.g. connective tissue and muscle fibers in meat and fish, cell walls of fruits and vegetables, etc.,) or as aid-agents intentionally added to manufactured food in order to increase sensory acceptability and physical stability. This chapter describes the selected instrumental analytical methods, which can provide “fingerprints” of the free structure characteristics leading to the unambiguous identification of some industrial polysaccharides. First, an overview is presented on the different techniques and strategies available for analysis of polysaccharide primary structure, which is followed by a section on specific examples of different analytical problems found in food polysaccharides. The systems covered are: (i) starch, (ii) gum arabic, (iii) alginate, and (iv) carrageenan. A summary of analytical tests to identify the presence of hydrocolloid gums in foods is also included as the final section of this review. Although the major structure features of each of the polysaccharide systems covered in the above examples and current analytical strategies to determine such features are outlined in this chapter, coverage by no means pretends to be exhaustive.