Macromolecular Interactions During Gelatinisation and Retrogradation in Starch-Whey Systems as Studied by Rapid Visco-Analyser

Abstract

Gelatinisation and retrogradation of starch-whey mixtures were studied in water (pH 7) using the Rapid Visco-Analyser (RVA). The starch:whey ratios ranged from 0:100 -100:0. Wheat starch, and whey protein concentrate (about 80% solids basis) and isolate (about 96% solids basis) were used. Mixtures with whey isolates were generally more viscous than those with whey concentrates, and this was attributed to fewer non-protein milk components in the former. Whey protein concentrates and isolates reduced the peak, trough and final viscosities of the mixtures, but the breakdown and setback ratios of the mixtures were increased. The gelatinisation temperature increased with whey substitutions indicating that whey protein delayed starch gelatinisation. The temperature of fastest viscosity development decreased as the amount of whey was increased. Whey protein isolate generally exercised a lesser effect than the concentrate. At between 40 -50% whey substitutions, the dominant phase changed from starch to protein irrespective of the source of the whey protein. An additive law poorly defined selected RVA parameters. Both macromolecules interacted to define the viscosity of the mixture, and an exponential model predicted the viscosity better than the additive law. The results obtained in this study are discussed to assist the understanding of extrusion processing of starch-whey systems as models for wheyfortified snack and ready-to-eat foods.

Weighing up whey fortification of foods: Implications for kinetics of starch digestion and estimated glycemic index of model high-protein-low-carbohydrate food systems

“…However, at 50% moisture, 300 rpm screw speed and 110 • C maximum barrel temperature, SME of the whey-starch mixtures ( ∼ =130 kJ kg −1 ) was much less than that for the wheat starch (290 kJ kg −1 ). This agrees with the observations of Sopade, Hardin, Fitzpatrick, Desmee, and Halley (2006) on the reduction of RVA pasting viscosity of the wheat starch as the concentration of whey proteins was increased. However, it is recognised that melt viscosity (limited water) in extrusion is different from RVA pasting viscosity (excess water).…”

“…The setback viscosity, which is the difference between RVA peak (or trough) and final viscosities, is regarded as a direct measure of starch retrogradation (Carvalho, Onwulata, & Tomasula, 2007;Mariotti, Sinelli, Catenacci, Pagani, & Lucisano, 2009). Apart from high amylose corn starch (Hylon VII), whey protein isolate reduced the setback viscosity (minimal retrogradation) of tapioca, amioca, and corn starches (Carvalho et al, 2007), while the setback viscosity of 50W50S was significantly less than 20W80S for both whey protein concentrate and isolate (Sopade et al, 2006). It is, therefore, unlikely that retrogradation during digestion could wholly explain the inverse relationship between whey concentration and rate of starch digestion in the present study if exogenous proteins enhance digestion.…”

Effects of soy protein hydrolysates on maize starch retrogradation studied by IR spectra and ESI-MS analysis

“…4 Glu + Asp + Phe + Lys + Lys + Ala + Gly + Ser + Thr + His + His + Glu + Arg + Leu Negative ion 178.7 Leu + HCOOH 648. 8 Asp + Arg + Val + Phe + Leu 656. 7 Asp + Tyr + Val + Phe + Leu 863.…”

“…2 Glu + Asp + Arg + Val + Phe + Phe + Phe + Lys + Ala + Gly + Ser + Thr + His + His + Leu 1978. 8 Glu + Arg + Val + Phe + Phe + Phe + Ala + Ser + Ser + Thr + His + His + His + His + Glu + Leu Negative ion 178.7 Leu + HCOOH 536. 7 Asp + Arg + Val + Phe 648.…”

“…In the trial experiment, it is found that certain soy protein hydrolysates derived from acidic protease inhibit maize starch retrogradation significantly. The reason for such inhibition probably lies in the syneresis of the protein-corn starch gel [7], gelatinization temperature increasing [8], and forming of a more elastic than viscous behavior [9]. Soy protein is mainly composed of glutamic acid, arginine, aspartic acid, leucine, lysine and phenylalanine [10][11][12][13].…”