[Studies on the electrostatic interactions between beta -lactoglobulin and tragacanthin: the first step towards fabrication of biopolymeric micro- and nanoparticles]

Investigation of the colloidal behaviour of protein-polysaccharide systems is becoming increasingly important to provide a foundation for their applications in areas such as production of biopolymer micro-and nano-particles, designing food analogues, and microencapsulation technology. The aim of the present study was to investigate the pH-induced critical transitions during associative phase separation between beta -lactoglobulin [BLG] and tragacanthin [T]. The formation of electrostatic complexes in BLG/T dispersions [0.3wt.% total concentration; BLG:T ratio 2:1] was investigated as a function of pH [2.00-6.00] by spectrophotometry and particle size analysis. In addition, coupling of slow in situ acidification of the blend, with gluconodelta-lacton, and rheometry were used to monitor the structural transitions during the associative phase separation. The influence of salt type and concentration on the formation of micro-particles were also determined. The formation of soluble complexes started at pH -5.20, and at pH -4.85 the aggregation of intrapolymeric complexes occurred, followed by a bulk phase separation at pH -4.30. The data indicated that coacervation occurred at pH 4.15. Finally, the mixture returned to a mono-phasic system at pH 2.5. Particle size analysis showed that the assembled structures experienced a contraction process upon complexation. Rheometry provided deeper insights into the colloidal behaviour of the system and the results were in good agreement with quiescent pH-induced transitions established by HCl titration. The formation of the micro-particles was strongly salt-dependent. Under controlled pH conditions, electrostatic interactions between beta -lactoglobulin and tragacanthin can be used to form a variety of biopolymer particles. These biopolymeric micro- and nanoparticles may be used in the food industry as natural delivery systems or fat-replacers

[Physico-chemical properties of some commercial lines of Iranian cultivated wheat flour and their effects on sensory attribute of biscuit]

Biscuits are the most common bakery product after bread in Iran and have a long shelf-life. The technological properties of Iranian wheats used to produce biscuits have not been investigated so far. The objective of this study was to investigate the physico-chemical properties of 20 Iranian wheat flours and the sensory properties of biscuits produced from them. Twenty Iranian wheat cultivars released by the Seed and Plant Improvement Institute [SPII], Karaj, Iran were studied. The wheat grains were milled using the Quadrumate Senior Mill. The physicochemical characteristics of the resulting flours were determined according to AACC [2000] methods. Biscuits were then baked from each flour and their organoleptic characteristics determined by trained panelists. The physical and chemical characteristics of the wheat flours differed significantly due to differences in genetic make-up and environmental factors. Sensory evaluation showed no significant differences between the colors and tastes of the biscuits. However, significant differences were found among them with regard to texture, shape and surface and overall acceptability. Further analysis of the data showed that the sensory characteristics of the biscuits were statistically negatively correlated with their protein and gluten contents, gluten index, and SDS sedimentation. Biscuits produced from Golestan, Moghan, Prishtaz, and Omid wheat cultivars had the highest quality and acceptability. The Moghan cultivar was found to give the highest yield of flour, so it is the most suitable cultivar for biscuit production