Thermal Denaturation of Milk Whey Proteins: A Comprehensive Review on Rapid Quantification Methods Being Studied, Developed and Implemented

Abstract

Heat treatment of milk signifies a certain degree of protein denaturation, which modifies the functional properties of dairy products. Traditional methods for detecting and quantifying the denaturation of whey proteins are slow, complex and require sample preparation and qualified staff. The world’s current trend is to develop rapid, real-time analytical methods that do not destroy the sample and can be applied on/in-line during processing. This review presents the rapid methods that are being studied, developed and/or applied to determine and quantify the thermal denaturation of whey proteins, including spectroscopic, electrochemical and miniaturized methods. The selected methods save a significant amount of time and money compared to the traditional ones. In addition, the review emphasizes the methods being applied directly to milk and/or that have potential for on/in/at-line application. There are interesting options to quantify thermal denaturation of whey proteins such as biosensors, nanosensors and microchips, which have fast responses and could be automated. In addition, electrochemical sensors are simple to use and portable, while spectroscopy alternatives are suitable for on/in/at-line process.

Changes in the physiochemical, flavor and stability of whey protein solutions during UHT processing and storage: a review

“…When heated, β-Lg expands and divides into two monomers, each of which has the reactive free sulfhydryl group that was hidden in the native structure as well as disulphide linkages. Because the exposed monomer creates disulphide bonds with additional molecules of α-La and β-Lg over 70 °C, denaturation becomes irreversible [7].…”

“…Indirect UHT treatment results in a lesser ratio, which means that more α-La and less β-Lg attach. A high β-Lg/α-La ratio is produced by intense heating, such as direct UHT processing [7].…”

“…The most common UHT milk degradation signs are sedimentation, gelation, and fat separation, which cause customer complaints and product recalls that result in significant financial losses [7]. Both the attempts to reduce global food waste and the food security policies for poor nations may be greatly impacted by the availability of UHT milk.…”

“…Whey protein could fractionated into several key components, such as β-lactoglobulin (β-Lg), α-lactalbumin (α-La), bovine serum albumin (BSA), immunoglobulins (Igs) and proteose peptones [6]. The physiochemical reactions like denaturation, age gelation, sedimentation and off-flavor during storage are highly related to these protein fractions [7]. Denaturation of BSA occurs when above 65 °C [8], and β-Lg denaturation is irreversible once above 70-74 °C, and would cause soluble protein aggregates [9].…”

“…Sulfide will be released during protein denaturation and contribute to off-flavor. A physiochemical process known as age gelation is triggered by plasmin or bacterial protease [7]. A significant factor reducing UHT milk's shelf life is age gelation during storage.…”