Reduced calorie emulsion-based foods: Protein microparticles and dietary fiber as fat replacers

The potential of using microparticulated whey protein (MWP) in combination with either modified starch or locust bean gum (LBG) as fat mimetics to fabricate reduced calorie emulsion-based sauces and dressings was studied. The influence of food matrix composition (protein, polysaccharide, and fat content), ionic strength, and pH on the properties of thermally processed model emulsions (90 °C/10 min) was investigated. Increasing protein concentration (2.5–7.5%) increased the mean (d_3,2) particle diameter due to the formation of large protein aggregates. All MWP-containing systems had a creamy white appearance with high lightness (L* > 75). Addition of fat droplets (5%) further increased their lightness (L* > 90) due to enhanced light scattering. Addition of starch, LBG, or MWP increased emulsion viscosity due to the increased effective volume fraction of the dispersed phase. Addition of calcium chloride (10 mM) and pH adjustment (2–8) caused little change in the physicochemical properties of the mixed systems. Overall, the appearance and rheological properties of the mixed systems were similar to commercial sauces and dressings. This study demonstrates that reduced calorie food emulsions with appearance and consistency similar to those of full-fat versions can be formulated using protein microparticles and polysaccharides.     

Gelation of single heated vs. double heated whey protein isolate

Gelation of single and double heated whey protein dispersions was investigated using Ca²⁺ as inducing agents. Whey protein isolate (WPI) dispersions (10% w/w) were single heated (30 min, 80 °C at pH 7.0) or double heated (30 min, 80 °C at pH 8.0 and 30 min, 80 °C at pH 7.0) and diluted to obtain the desired protein and/or calcium ions concentration (4–9% and 5–30 mm, respectively). Calcium ions were added directly or by using a dialysis method. Double-heated dispersions gelled faster at lower protein and calcium ion concentrations than single-heated dispersions. Gels obtained from double-heated dispersions had lower values of shear strain and shear stress at fracture than gels obtained from single-heated dispersions. Double heating caused a significant complex modulus (G*) increase at 4% WPI and 15 mm calcium ions in comparison with gels obtained from single-heated dispersion. Less significant differences between gels made from double and single-heated dispersions were observed at 6% WPI, however a higher value of complex modulus was obtained for 8% protein gels from the single-heated solution. Native and non-reduced SDS–PAGE did not show clearly the effect of different procedures of heating on the quantities of polymerised proteins. Proteins in double-heated dispersions had higher hydrophobicity. Increased calcium concentration caused decreased protein hydrophobicity for both single and double-heated solutions.     

Surface Tension of Whey and Whey Derivatives

The surface tension of various whole wheys, solutions of component whey proteins, UF fractions, and the effect of heating on the surface tensions of these solutions were determined using the Wilhemy plate method. The mean surface tension of three commercial cottage cheese wheys, a commercial cheddar cheese whey, and a laboratory rennet whey was found to be 41.7 ± 1.2 dyne/cm (25°C) and did not vary significantly with the type of whey despite differences in both pH and protein content. The surface tensions of aqueous solutions of individual pure protein fractions of whey (serum albumin, β-lactoglobulin, α-lactalbumin, and gammaglobulins), in concentrations approximating normal whey contents, were significantly different and greater than for the whole wheys.Heating of individual protein solutions at 80°C for 50 min produced insignificant changes in measured surface tension despite producing protein precipitation in some of the solutions. Similar heating of the whole whey solutions resulted in a significant decrease in surface tension and marked precipitation in most cases.The fractionation of the wheys into UF permeates and retentates resulted in a retentate fraction of significantly lower surface tension than for UF permeates. Heating increased the surface tension of retentate fractions while the permeate fractions showed a decrease.     

Effect of pH and heat treatment of cheese whey on solubility and emulsifying properties of whey protein concentrate produced by ultrafiltration

The effects of pH and heat treatment of cheese whey on protein solubility (PS) at pH 4.6 and on emulsifying properties of whey protein concentrate (WPC) were studied by response surface methodology (RSM). PS followed a quadratic relationship with pH and a linear relationship with heat treatment. Highest values for PS were found between pH 6.0 and 6.6 with heat treatment at 68 °C for 2 min, and maximum solubility was reached at pH 6.3. Heat treatment strongly decreased protein solubility throughout the entire pH range. The emulsifying properties were notably benefited by raising the pH from 6 to 7, best values being shown at pH 7 with a heat treatment of 70 °C for 2 min. The effect of heat treatment on the emulsifying properties was dependent on the pH level. At about pH 7, the heat treatment adversely affected the emulsifying properties, probably due to excessive protein denaturation.     

Binding of retinyl acetate to whey proteins or phosphocasein micelles: Impact of pressure-processing on protein structural changes and ligand embedding

A whey protein isolate (WPI) and native phosphocaseins (PC) at pH 6.5–6.6 were processed with retinyl acetate (RAC) using pressure-assisted technological tools to improve RAC embedding through processing-induced protein structural changes. To this end, protein-RAC dispersions were submitted to ultra-high pressure homogenisation (UHPH) at 300 MPa and an initial fluid temperature (T_in) of 14 °C or 24 °C, or isostatic high-pressure at 300 MPa and 14 °C or 34 °C for 15 min. A short-time thermal treatment (STTT, 73 °C for 4 s) able to generate WPI aggregates was assessed for comparison. Processing effects were investigated in terms of protein particle sizes and molecular weights (M_w). M_w calculated using protein size determination obtained from light scattering measurements were in agreement with the known values. The amounts of RAC retained in WPI particles (unfolded and/or aggregated proteins) or in PC assemblies were quantitated after protein precipitation by ammonium sulphate. A 2.3–3.7 nmol RAC was carried per mg of pressure-denatured whey proteins, significantly less than after STTT (6.3 nmol RAC per mg of heat-denatured whey proteins) indicating that RAC embedding varied according to the technological tool, pressure or temperature. A 3.8–5.4 nmol RAC was carried per mg of PC assemblies through pressure-induced dissociation/reassociation of PC micelles. Combined pressure and mild temperature increased RAC embedding in PC assemblies.     

Determination of Whey Protein Denaturation in Heat-Processed Milks: Comparison of Three Methods

Fast protein liquid chromatography was used to determine the extent of whey protein denaturation in various heat-treated milk samples: Sordi-indirect UHT (145°C/3 s), Dasi-direct UHT (142°C/3 s), HTST (80°C/30 s), and batch (63°C/30 min). Results were compared with other published methods (differential scanning calorimetry, whey protein nitrogen index, and Kjeldahl nitrogen on salt fractions). Results of the differential scanning calorimetry method were too erratic to be used to quantify whey protein denaturation. The remaining methods (fast protein liquid chromatography, Kjeldahl nitrogen, and whey protein nitrogen index) gave reproducible results and the extent of denaturation (highest to lowest) was consistently predicted as Sordi > Dasi > HTST > batch. There was no difference between fast protein liquid chromatography and Kjeldahl nitrogen, but there was a significant difference between fast protein liquid chromatography and whey protein nitrogen index and between Kjeldahl nitrogen and whey protein nitrogen index. Fast protein liquid chromatography appears to be an effective method to determine whey protein denaturation in heat-treated milks.     

Ability of conventional and nutritionally-modified whey protein concentrates to stabilize oil-in-water emulsions

The ability of a modified whey protein concentrate (MWPC), which contains relatively high proportions of phospholipid and high molecular weight protein fractions, to form and stabilize 10 wt% corn oil-in-water emulsions (pH 7.0, 5 mM phosphate buffer) was compared with that of a conventional whey protein concentrate (CWPC). The MWPC stabilized emulsions required less protein to prepare stable emulsions with monomodal particle size distributions and small mean droplet diameters (d₄₃ ≈ 0.3 μm at [WPC] ⩾ 0.5 wt%) than CWPC stabilized emulsions (d₄₃ ≈ 0.4 μm at [WPC] ⩾ 0.9 wt%) under similar homogenization conditions (5 passes at 5000 psi). In addition, the emulsions stabilized by 0.9 wt% MWPC were more stable to high salt concentration (NaCl ⩽ 200 mM), thermal processing (30–90 °C for 30 min) and pH (3, 6 and 7) than those stabilized by the same concentration of CWPC, which was attributed to polymeric steric repulsion rather than electrostatic repulsion. This study has important implications for the wide application of WPC as a natural emulsifier in food products.     

Effect of fermentation on biochemical and sensory characteristics of sorghum flour supplemented with whey protein

Changes in pH, titrable acidity, protein, non-protein nitrogen, total soluble solids, protein fractions and in vitro protein digestibility were investigated during fermentation and/or after supplementation of sorghum flour with whey protein. The pH of the fermenting material decreased sharply with a concomitant increase in the titrable acidity. The total soluble solids increased with progressive fermentation time. The crude protein and non-protein nitrogen both increased with fermentation time. The protein content and fractions were significantly (p ⩽ 0.05) increased after supplementation with whey protein. The albumin plus globulin fraction increased significantly (p ⩽ 0.05) during the first 8 h of fermentation after supplementation with 5% whey protein. Other fraction contents were observed to fluctuate during the fermentation time. Supplementation of the cultivar flour with 10% whey protein greatly increased the protein content as well as the albumin plus globulin fraction while other fractions were significantly decreased. The in vitro protein digestibility was significantly (p ⩽ 0.05) improved during fermentation and even after supplementation. Sensory evaluation of locally processed sorghum products (Kisra, Asida and Nasha) before and after supplementation showed no difference between the supplemented samples and the control ones as judged by trained panellists.     

Gel-Forming Characteristics of Milk Proteins. 1. Effect of Heat Treatment

Skim milk with or without preheating (60 to 80°C for 30 min) were acid coagulated at 60 to 80°C for 1 h with glucono-delta-lactone. Preheating below 70°C has no effect on gel firmness and water-holding capacity. When coagulated below 70°C, the gels were weak and had low water-holding capacity. When coagulated at 80°C, the gels were solid and had high water-holding capacity. Gels prepared from skim milks preheated to above 80°C had a different quality: when coagulated at less than 70°C, gel firmness increased slightly, and when coagulated at 80°C, gel firmness decreased sharply. Change in the accessibility of sulfhydryl groups in milk protein caused by heating, was also measured using Ellman's reagent. Changes in the gel-forming property of milk protein, caused by the heat treatment, were closely related to increase in available sulfhydryl groups in milk proteins, and also were related to heat denaturation of whey protein or the formation of β-lactoglobulin/κ-casein complex.     

Physical Properties of Yogurt: A Comparison of Vat Versus Continuous Heating Systems of Milk

Milk was processed by vat (85°C for 10 to 40 min), high temperature, short time (98°C for .5 to 1.87 min), and ultra-high temperature (140°C for 2 to 8 s) heating systems and made into yogurt. Yogurt firmness ranged from 90 to 104 g force for vat treatments, 74 to 96 g for high temperature, short time treatments, and 47 to 65 g for ultra-high temperature treatments. Planned contrasts between heating systems indicated significantly higher yogurt firmness and viscosity for vat versus high temperature, short time and ultra-high temperature systems. Yogurt from high temperature, short time milk showed the highest water-holding capacity, followed by ultra-high temperature and vat treatments. Correlation coefficient between yogurt firmness and whey protein denaturation was .83 and between apparent viscosity and whey protein denaturation was .89. Sensory evaluation indicated an overall preference for yogurt made from high temperature, short time (1.87 min) milk.     

Comparison of a modified spectrophotometric and the pH-stat methods for determination of the degree of hydrolysis of whey proteins hydrolysed in a tangential-flow filter membrane reactor

A procedure was developed to determine the degree of hydrolysis (DH) of whey protein hydrolysates (WPH) during hydrolysis in either 3 kDa or 10 kDa tangential-flow filter (TFF) enzymatic membrane reactors (EMR). Protease N Amano G (IUB 3.4.24.28, Bacillus subtilis) was used to hydrolyse an initial 5% (w v^?1) aqueous solution of whey protein isolate (86.98% protein) at pH 7.0 and 55 °C with continuous recirculation and simultaneous removal of hydrolysates through the TFF, in single- or two-stage operation. The DH in the permeate and the retentate were determined as the concentration of the free α-NH₂ using 2,4,6-trinitrobenzene 1-sulphonic acid (TNBS) and compared to the pH-stat method. In the new method, the DH of the permeate, the retentate and for the total EMR process could be quantified together or independently. The pH-stat method exaggerated the DH in the EMR because of the leakage of the alkali. The TNBS method was more reliable for DH estimation in the EMR.     

Kinetics of browning during accelerated storage of sweet whey powder and prediction of its shelf life

Sweet whey powder (SWP) of different pH was prepared by exposing native SWP to acetic acid vapors in a desiccator. Samples were subjected to accelerated browning at temperatures of 40, 60 and 80 °C in sealed vials and the rate of color formation was measured. Sample lightness decreased over time and the rate of decrease was faster at higher temperature and lower pH. Results were modeled using a pseudo-first-order reaction kinetic equation. The shelf life of SWP was estimated using a time–temperature plot. Increasing the temperature and decreasing the pH strongly decreased the shelf life from greater than 2 years at 53 °C for native SWP (pH∼6.3) to 5.2 days at 60 °C for intermediate acid SWP (pH∼5.0). A time–temperature–tolerance approach involving the practical storage life was used to predict the impact of temperature abuse during manufacture, transportation or storage.     

Comparison of properties of oil-in-water emulsions stabilized by coconut cream proteins with those stabilized by whey protein isolate

Coconut cream protein (CCP) fractions were isolated from coconuts using two different isolation procedures: isoelectric precipitation (CCP1-fraction) and freeze–thaw treatment (CCP2-fraction). The ability of these protein fractions to form and stabilize oil-in-water emulsions was compared with that of whey protein isolate (WPI). Protein solubility was a minimum at ∼pH 4, 4.5 and 5 for CCP1, CCP2, and WPI, respectively, and decreased with increasing salt concentration (0–200 mM NaCl) for the coconut proteins. All of the proteins studied were surface active, but WPI was more surface active than the two coconut cream proteins. The two coconut cream proteins were used to prepare 10 wt% corn oil-in-water emulsions (pH 6.2, 5 mM phosphate buffer). CCP2 emulsions had smaller mean droplet diameters (d₃₂ ≈ 2 μm) than CCP1 emulsions (d₃₂ ≈ 5 μm). Corn oil-in-water emulsions (10 wt%) stabilized by 0.2 wt% CCP2 and WPI were prepared with different pH values (3–8), salt concentrations (0–500 mM NaCl) and thermal treatments (50–90 °C for 30 min). Considerable droplet flocculation occurred in the emulsions near the isoelectric point of the proteins: CCP2 (pH ∼ 4.3); WPI (pH ∼ 4.8). Emulsions with monomodal particle size distributions, small mean droplet diameters, and good creaming stability could be produced at pH 7 for WPI, but CCP2 produced bimodal distributions at this pH. The CCP2 and WPI emulsions remained relatively stable to droplet aggregation and creaming at NaCl concentrations ⩽50 and ⩽100 mM, respectively. In the absence of salt, both CCP2 and WPI emulsions were quite stable to thermal treatments (50–90 °C for 30 min).     

Survival of Salmonella Enteritidis PT 30 on inoculated almond kernels in hot water treatments

Almonds are blanched by exposure to hot water or steam-injected water to remove the pellicle (skin) from the kernel. This study evaluated the survival of Salmonella Enteritidis PT 30, Salmonella Senftenberg 775W and Enterococcus faecalis on whole raw almond kernels exposed to hot water. Whole, inoculated (7 to 9 log CFU/g) Nonpareil almonds (40 g) were submerged in 25 L of water maintained at 60, 70, 80 and 88 °C. Almonds were heated for up to 12 min, drained for 2 s, and transferred to 80 mL of cold (4 °C) tryptic soy broth. Almonds in broth were stomached at high speed for 2 min, serially diluted, plated onto tryptic soy and bismuth sulfite agars (Salmonella) or bile esculin agar (Enterococcus) and incubated at 37 °C for 24 and 48 h, respectively. D values of 2.6, 1.2, 0.75 and 0.39 min were calculated for exposure of S. Enteritidis PT 30 to water at 60, 70, 80 and 88 °C, respectively; the calculated z value was 35 C°. D values determined for Salmonella Senftenberg 775W and E. faecalis at 88 °C were 0.37 and 0.36 min, respectively. Neither Salmonella serovar could be recovered by enrichment of 1-g samples after almonds inoculated at 5 log CFU/g were heated at 88 °C for 2 min. These data will be useful to validate almond industry blanching processes.     

Effect of preheating and other process parameters on whey protein reactions during skim milk powder manufacture

Skim milk powder was manufactured in a milk powder plant using different preheating temperatures, concentrate heating temperatures and spray drying temperatures. Varying the preheating conditions from 70 °C for 52 s to 120 °C for 52 s had a marked effect on the denaturation of $\beta$-lactoglobulin A, $\beta$-lactoglobulin B, $\alpha$-lactalbumin, bovine serum albumin (BSA), and immunoglobulin G. In contrast, varying concentrate heating temperature (65–74 °C) and inlet/outlet air dryer temperature (200/101 °C–160/89 °C) had a minimal effect on whey protein denaturation. Most of the whey protein denaturation and association with the casein micelle occurred in the preheating section of the powder plant. Aggregation of β-lactoglobulin (β-lg) and BSA predominantly involved disulphide bonds. Although, greater than 90% of the β-lg and BSA was denatured after preheating at 120 °C for 52 s, the extent of association with the casein micelle was lower, 50% for β-lg and 75% for BSA.     

Influence of high intensity ultrasound on microbial reduction,physico-chemical characteristics and fermentation of sweet whey

The aim of this study was to investigate the influence of high intensity ultrasound on quality of reconstituted sweet whey in order to substitute thermal treatments i.e. pasteurization. Also, it was intended to study the influence of ultrasound on fermentation process of pasteurized or thermo-sonicated whey with respect to culture activation and sensory properties of the fermented whey. In the first stage, whey was subjected to treatments with different power inputs (480 W, 600 W) over 6.5, 8 and 10 min at constant temperature (45 °C, 55 °C). Treated whey samples were analyzed for microbiological quality, particle size distribution, protein content, acidity, electrical conductivity, viscosity and sensory properties. All of the analyzed parameters were compared with the control sample (pasteurized) and fresh whey. Subsequently, influence of high intensity ultrasound on pasteurized or thermo-sonicated whey fermentation with yoghurt culture and with monoculture Lactobacillus acidophilus La-5 was investigated. Ultrasound treatments were applied for culture activation prior to or after the inoculation. Whey thermo-sonication by nominal power of 480 W for 10 min at 55 °C resulted in better microbiological quality and sensory properties in comparison to whey pasteurization. Ultrasound treatments with nominal input power of 84 W over 150 s resulted in the highest increase of the viable count during the activation process. Whey fermentation by ultrasonicated culture La-5 lasted 30 min shorter and resulted in higher viable cells count.Industrial relevanceAttached paper (“Influence of high intensity ultrasound on microbial reduction, physico-chemical characteristics and fermentation of sweet whey”) reports the influence of high intensity ultrasound on quality and fermentation process of sweet whey. Also, the influence of high intensity ultrasound on pasteurized or thermo-sonicated whey fermentation with yoghurt culture and with monoculture Lactobacillus acidophilus La-5 was investigated.Whey proteins are thermo-labile proteins and degradable at higher temperatures (above 60 °C), and at conventional processing (pasteurization), denaturation and precipitation of proteins occur. Ultrasound gives a great replacement for pasteurization where precipitation does not occur. Also, ultrasonic treatment of the whey results in homogenization and thus, stability is increased. When microbiological cultures for fermentation, prior to the inoculation in the samples, are treated by ultrasound their activity is higher (explained in the paper) and thus fermentation is faster.From an economical point of view, processing by ultrasound can reduce costs a lot, since fermentation time is shorter, and the same effect as pasteurization is achieved. Ultrasonic treatment is a future in the dairy industry.     

Effect of cook temperature on starter and non-starter lactic acid bacteria viability,cheese composition and ripening indices of a semi-hard cheese manufactured using thermophilic cultures

Semi-hard cheeses were manufactured using Streptococcus thermophilus and Lactobacillus helveticus cultures and their ripening was characterised. During cheese manufacture, curds were cooked to a maximum temperature of 47, 50 or 53 °C, pre-pressed under whey at pH 6.15, moulded, pressed and brined. Increased cook temperature resulted in increased manufacture time, a significantly reduced growth rate of S. thermophilus during manufacture in the order 47≈50 °C>53 °C and in significantly lower mean viable cell counts of S. thermophilus up to 56 d of ripening. Increasing cook temperature had no significant effect on mean viable cell numbers of L. helveticus or non-starter lactic acid bacteria (NSLAB). Cheeses produced from curds cooked to 47 °C had significantly higher levels of moisture in non-fat substances (MNFSs), salt-in-moisture and a significantly lower pH and levels of butyrate compared with cheeses produced from curds cooked to 50 or 53 °C.     

Effect of heat treatment and casein to whey protein ratio of skim milk on graininess and roughness of stirred yoghurt

The aim of this work was to study how heat treatment and casein (CN) to whey protein (WP) ratio of skim milk affect physical characteristics of stirred yoghurt. Different heat treatments (95 °C/256 s, 110 °C/180 s and 130 °C/80 s) were applied to the yoghurt milk with the CN to WP ratios of 1.5:1, 2:1, 3:1 and 4:1. Physical properties, including graininess and roughness, of stirred yoghurt were determined during storage at 4 °C for 15 days. Visual roughness, number of grains, perimeter of grains, storage modulus, and yield stress decreased, when heating temperature or CN to WP ratio increased.     

Instant flour from quality protein maize (Zea mays L). Optimization of extrusion process

Traditional nixtamalization process for producing instant flours is highly time and energy consuming; in addition, it presents problems of high liquid waste discharges (3–10 L H₂O/kg maize). Extrusion represents an alternative technological for producing instant flours and does not generate effluents. The objective of this work was to determine the best combination of extrusion process variables for the production of instant flour from quality protein maize (QPM) (Zea mays L) V537 variety. Prior to extrusion, the maize kernels were broken to obtain grits (1−2 mm) which were mixed with lime and water to reach a moisture content of 28 g/100 g. The single screw extruder operation conditions were selected from a factorial combination of process variables: extrusion temperature (ET, 70–100°C), lime concentration (LC, 0.1–0.3 g/100 g maize) and screw velocity (SV, 30–80 rpm). A central composite experimental design with five variation levels was chosen. Response surface methodology was applied as optimization technique, over four response variables: in vitro protein digestibility (PD), total color difference (ΔE), water absorption index (WAI) and pH. Predictive models for response variables were developed as a function of process variables. The conventional graphical method was applied to obtain maximum PD, WAI, pH and minimum ΔE. Contour plots of each of the response variables were utilized applying superposition surface methodology, to obtain three contour plots for observation and selection of a superior (optimum) combination of ET (79.4°C), LC (0.24 g/100 g maize) and SV (73.5 rpm) to obtain optimized extruded maize flour (EMF) from QPM with a single screw extruder. Optimized EMF had similar physico-chemical and functional characteristics than commercial nixtamalized maize flours (NMF).     

Influence of lupin-based milk alternative heat treatment and exopolysaccharide-producing lactic acid bacteria on the physical characteristics of lupin-based yogurt alternatives

In the present study we investigated the influence of heat treatment of lupin-based (LB) milk alternatives and different exopolysaccharide (EPS)-producing lactic acid bacteria on the physical characteristics of set-type LB yogurt alternatives. LB milk alternatives, obtained from protein isolate of Lupinus angustifolius cv. Boregine, were either pasteurized at 80 °C for 60 s or ultra-high temperature (UHT) heated at 140 °C for 10 s and was fermented with Lactobacillus plantarum TMW 1.460 and 1.1468, Pediococcus pentosaceus BGT B34 and Lactobacillus brevis BGT L150. Fermentation duration was strongly affected by heat treatment: different strains needed between 25 to 35 h in UHT LB milk alternative to reach a pH of 4.5 compared to 14 to 24 h in pasteurized LB milk alternative. EPS extraction revealed slightly higher amounts of EPS for UHT LB yogurt alternatives (~ 0.5–0.9 g/l; pasteurized: ~ 0.4–0.7 g/l). The more intensive heat treatment (UHT) resulted also in better rheological (apparent viscosity, hysteresis loop area, flow point, elastic, viscous and complex modulus) and textural properties (firmness, consistency, cohesiveness and index of viscosity) of the investigated LB yogurt alternatives. Furthermore, LB yogurt alternatives out of UHT milk alternative revealed a lower tendency to syneresis, measured with siphon and centrifugation method. This work contributes to the fundamental knowledge of the textural properties of LB yogurt alternatives.