P.J. Luck

Properties of whey and egg white protein foams

Abstract Foams made of varying concentrations (2–20% w/v protein) of egg white and whey protein isolate were compared by measuring rheological and microstructural properties. Egg white proteins formed foams with higher yield stress (τ) at lower protein concentrations and less whipping time than whey protein isolate foams. The model of Princen and Kiss [J. Coll. Interf. Sci. 128 (1989) 176] predicts a relationship among τ, surface tension (σ), phase volume (φ), and bubble size (R32). This was supported by τ increasing with φ, and the relationship between τ and φ1/3 becoming more linear as protein concentration increased. However, egg white foams had yield stress values as much as 100 Pa greater than whey protein foams, despite having similar phase volumes, bubble size, and lower surface tensions. The experimentally determined factors, Y(φ), for egg white and whey protein isolate foams were within the range determined by Princen and Kiss [J. Coll. Interf. Sci. 128 (1989) 176] for concentrated emulsions. Egg white foams were different in that the values for Y(φ) increased at lower phase volumes than for whey protein isolate foams or concentrated emulsions. These results suggest that specific proteins contribute to foam τ by some means in addition to altering surface properties.

Roles of charge interactions on astringency of whey proteins at low pH

Whey proteins are a major ingredient in sports drink and functional beverages. At low pH, whey proteins are astringent, which may be undesirable in some applications. Understanding the astringency mechanism of whey proteins at low pH could lead to developing ways to minimize the astringency. This study compared the astringency of beta-lactoglobulin (beta-LG) at low pH with phosphate buffer controls having the same amount of phosphate and at similar pH. Results showed that beta-LG samples were more astringent than phosphate buffers, indicating that astringency was not caused by acid alone and that proteins contribute to astringency. When comparing among various whey protein isolates (WPI) and lactoferrin at pH 3.5, 4.5, and 7.0, lactoferrin was astringent at pH 7.0 where no acid was added. In contrast, astringency of all WPI decreased at pH 7.0. This can be explained by lactoferrin remaining positively charged at pH 7.0 and able to interact with negatively charged saliva proteins, whereas the negatively charged WPI would not interact. Charge interactions were further supported by beta-LG or lactoferrin and salivary proteins precipitating when mixed at conditions where beta-LG, lactoferrin, or saliva themselves did not precipitate. It can be concluded that interactions between positively charged whey proteins and salivary proteins play a role in astringency of proteins at low pH.

Comparison of functional properties of 34% and 80% whey protein and milk serum protein concentrates

This study compared the functional properties of serum protein concentrate (SPC) with whey protein concentrate (WPC) made from the same milk and with commercial WPC. The experimental SPC and WPC were produced at 34% or 80% protein from the same lot of milk. Protein contents of WPC and SPC were comparable; however, fat content was much lower in SPC compared with WPC and commercial WPC. The effect of drying methods (freeze vs. spray drying) was studied for 34% WPC and SPC. Few differences due to drying method were found in turbidity and gelation; however, drying method made a large difference in foam formation for WPC but not SPC. Between pH 3 and 7, SPC was found to have lower turbidity than WPC; however, protein solubility was similar between SPC and WPC. Foaming and gelation properties of SPC were better than those of WPC. Differences in functional properties may be explained by differences in composition and extent of denaturation or aggregation.

Caramel as a Model System for Evaluating the Roles of Mechanical Properties and Oral Processing on Sensory Perception of Texture

Food formulation can have a significant impact on texture perception during oral processing. We hypothesized that slight modifications to caramel formulations would significantly alter mechanical and masticatory parameters, which can be used to explain differences in texture perception. A multidisciplinary approach was applied by evaluating relationships among mechanical properties, sensory texture, and oral processing. Caramels were utilized as a highly adhesive and cohesive model system and the formulation was adjusted to generate distinct differences in sensory hardness and adhesiveness. Descriptive analysis was used to determine sensory texture, and mechanical properties were evaluated by oscillatory rheology, creep recovery, and pressure sensitive tack measurements. Oral processing was measured by determining activity of anterior temporalis and masseter muscles via electromyography and tracking jaw movement during chewing. The substitution of agar or gelatin for corn syrup at 0.6% w/w of the total formulation resulted in increased sensory hardness and decreased adhesiveness. Creep recovery and pressure sensitive tack testing were more effective at differentiating among treatments than oscillatory rheology. Hardness correlated inversely with creep compliance, and both stickiness and tooth adhesiveness correlated with pressure sensitive adhesive force. Harder samples, despite being less adhesive, were associated with increased muscle activity and jaw movement during mastication. Tooth packing, not linked with any mechanical property, correlated with altered jaw movement. The combination of material properties and oral processing parameters were able to explain all sensory texture differences in a highly adhesive food.

Milk Protein Products | Whey Protein Products

Whey proteins, a coproduct of cheesemaking and casein manufacture, represent a rich and heterogeneous mixture of proteins with a broad range of nutritional and functional properties. Significant progress in the utilization of whey has been made in the past 30 years, especially with the current research findings on the health benefits of whey proteins and their derivatives. The future growth of whey utilization is expected to be led by the industry’s increasing focus on nutritional products, particularly in the dietary, sports, and clinical segments of the market. Functional properties of whey proteins in foods include solubility, dispersibility, heat stability, network formation (gels and edible films), and surface activity (emulsions and foams). This article discusses the production, processing, and applications of whey proteins and their derivatives.