Cold-Set Whey Protein Gels with Addition of Polysaccharides

Abstract

Cold-set whey protein (WP) gels with addition of xanthan or guar were evaluated by mechanical properties and scanning electron microscopy. Gels were formed after the addition of different amounts of glucono-δ-lactone to thermally denatured WP solutions, leading to different acidification rates and final pH values. At lower acidification rates and higher final pH, gels showed more discontinuous structure and weaker and less elastic network, which was attributed to a predominance of phase separation during gel formation due to slower gelation kinetics. In contrast, at higher acidification rates and lower final pHs, gelation prevailed over phase separation, favoring the formation of less porous structures, resulting in stronger and more elastic gels. The gels' fractal dimension (D f ; structure complexity) and lacunarity were also influenced by the simultaneous effects of gelation and phase separation. For systems where phase separation was the prevailing mechanism, greater lacunarity parameters were usually observed, describing the heterogeneity of pore distribution, while the opposite occurred at prevailing gelation conditions. Increase in guar concentration or lower final pH of xanthan gels entailed in D f reduction, while the increase in xanthan concentration resulted in higher D f . Such a result suggests that the network contour length was rugged, but this pattern was reduced by the increase of electrostatic interactions among WP and xanthan. Guar addition caused the formation of gel network with smoother surfaces, which could be attributed to the guar-protein excluded volume effects leading to an increase in protein-protein interactions.

Effect of polysaccharides with different ionic charge on the rheological, microstructural and textural properties of acid milk gels

“…This is consistent with the rheology results which showed that addition of 0.05% LBG increased the G′. Similar results were reported previously (Cavallieri & Cunha, 2009;Sanchez et al, 2000). Such a marked effect of addition of higher concentrations of guar and LBG may be responsible for their negative effect on the rheological properties of the samples as discussed in Section 3.2.1.1.…”

Effect of addition of gelatin on the rheological and microstructural properties of acid milk protein gels

“…The diameter of 316 the casein particles was 0.2-0.3 µm and the average pore size was about 1-2 µm. Similar results have 317 been previously reported (Aichinger, et al, 2003;Cavallieri, et al, 2009;Walkenstrom, et al, 1996). 318…”

“…The protein concentration used in this work was lower than the 173 minimum required for thermal gelation of whey proteins. So the heat treatment (95 ˚C for 10 min) 174 prior to acidification did not cause gelling of WPI, although the whey proteins would have been 175 denatured with partial unfolding and subsequent aggregation into fine strands (Cavallieri, et al, 2009; 176 The mixed gels showed much lower G′ values than pure WPI gels except for the gel with 0.4% gelatin, 184 which had G′ value similar to that of pure WPI gel (Fig. 1A).…”

“…SEM has been a 56 very useful technique for determining the microstructure of milk protein gels with simple specimen 57 preparation and to provide a three-dimensional image (Kalab & Harwalkar, 1973). The microstructure 58 of milk gels with polysaccharides has been studied widely using SEM (Cavallieri & Cunha, 2009; 59 specimens in the study of Kalab, et al (1975) were prepared by freeze drying after fixation and 61 observed at accelerating voltage of 20 kV. The relatively high accelerating voltage may induce 62 structure damage, especially with the technique of freeze drying during specimen preparation, while at 63 a low acceleration voltage, the freeze drying technique was reported to produce poor resolution (Trieu 64 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 for SEM, which can provide distortion-free images (Bray, Bagu, & Koegler, 1993).…”

Effect of chemical composition on physico-chemical, rheological and sensory properties of spreadable processed whey cheese

“…All the PWC samples received above average scores of smoothness, revealing that any possible inherent whey protein aggregates were not perceived by the panellists. Guar gum addition has been shown to cause the formation of whey protein isolate network with smoother surfaces, attributed to the guar-protein excluded volume effects leading to an increase in protein-protein interactions [53]. Stickiness was more prominent in samples 3-6, as well as 9, which all received equal scores, and was less evident in sample 1, which also had a lower value of adhesiveness, as determined by TPA.…”