Effect of concentration, homogenization and stabilizing salts on heat stability and rheological properties of cow skim milk ultrafiltered retentate

Abstract

Ultrafiltration (UF) of skimmed milk altered the composition of UF retentate and decreased the heat stability. Heat stability further reduced upon its subsequent homogenization or diafiltration. Poor heat stability of UF retentate restricts its processing at elevated temperatures. Therefore, this study was aimed to investigate the effect of protein concentration, homogenization and addition of stabilizing salts on the heat stability and rheological properties of UF retentates. Changes in the heat stability of fivefold homogenized UF retentate (59 HUFR) was studied in the pH range of 6.1-7.0. Disodium phosphate and trisodium citrate significantly increased the heat coagulation time (HCT) from 1.45 min (pH 6.41) to 120 min (at pH 6.5, 6.6, 7.0) and 80 min (pH 6.6), respectively. Significant reduction in f-potential of UF retentates was observed with an increase in calcium and reduction in pH during UF process. Rheological behaviour of retentates above threefold concentration exhibited Herschel-Bulkley behavior with linear increase in flow behavior index (n). Changes in the viscosity of the homogenized retentates were measured at the respective pH of maximum heat stability as a function of temperature (20-80°C). Promising approaches that might improve the heat stability, solubility and other functional properties of protein rich powders have been discussed in this article.

Physico-chemical, functional and rheological properties of milk protein concentrate 60 as affected by disodium phosphate addition, diafiltration and homogenization

“…Particle density and tapped density of MPC 60 was 1.12 and 0.54 g/mL, respectively (Crowley et al 2014). The observed difference among the loose and packed bulk densities of MPC60 powders could be attributed to the existing difference in the feed (treated with different treatments) characteristics particularly in TS and viscosity of 59 UFR as earlier reported by Meena et al (2016) that might have altered the atomization and could resulted in altered density, occluded and interstitial air content, SSA and particle size distribution of the resultant powders. Bulk density of powders being complex property cannot be correlated with single factor only as it is affected by feed properties, atomizer type, particle size (distribution) and density; occluded and interstitial air contents (Schuck 2013).…”

“…Results obtained during the present investigation (mean value, n = 3) were subjected to one-way analysis of variance (ANOVA) using SAS Enterprise guide (5.1, 2012) developed by SAS Institute Inc., North Carolina, USA (SAS 2008) and represented using Tukey's Studentized Range (HSD) test as per Meena et al (2016). Crowley et al (2014) and Huppertz and Gazi (2015).…”

“…Significant (P \ 0.05) variations in the SSA; d 10 , d 50, and d 90 ; D 3,2 and D 4,3 values of the MPC60 powders were observed which might be attributed to the reported variation in composition of feed and its viscosity (Meena et al 2016) prior to its drying. The maximum and minimum values (Table 2) of SSA; d 10 , d 50, and d 90 ; D 3,2 and D 4,3 were observed in MPC60-Na-K and MPC60-H; MPC60-H and MPC60-Na-K, MPC60-C and MPC60-H, MPC60-H and MPC60-Na-K; MPC60-H and MPC60-Na-K, respectively.…”

“…Concentration factor (CF) i.e. ratio of original feed volume to final feed volume was calculated for milk on weight basis as reported by Meena et al (2016). All salts used in this study were of analytical grade and procured from Sigma-Aldrich, USA.…”

“…Lactose contents of the powders were determined by difference i.e. by subtracting protein, fat and ash from TS contents of respective powders as earlier reported for retentates by Meena et al (2016). Calcium content of all powders were analyzed in a Shimadzu AA-7000, atomic absorption spectrophotometer (AAS) using the method of AOAC (2005) adopting the procedure earlier reported by Kaushik et al (2014).…”