Whey protein is a group of globular dairy proteins recovered from the liquid fraction of milk after casein removal, used in confections for aeration, Maillard browning, emulsification, and increasingly for nutritional fortification. Because it combines strong foaming behavior with high Maillard reactivity, whey protein occupies a functional role that few other ingredients can replace in aerated and heat-processed candies.

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What types of whey protein are used in confectionery?

Whey proteins reach confectionery formulators in several standardized forms, distinguished primarily by protein content and processing history:

- Sweet whey powder: derived from rennet-coagulated cheese production (pH ~6.5), containing approximately 11–14.5% protein alongside lactose and minerals. Used where lactose and Maillard browning are both desired [1].

- Whey protein concentrate (WPC): protein content ranging from 34% to 80%, produced by ultrafiltration of liquid whey. WPC-80 is the most common concentrate grade in confectionery for its balance of functionality and cost [2,3].

- Whey protein isolate (WPI): ≥90% protein on a dry basis, produced by microfiltration, ion-exchange chromatography, or extended diafiltration. Chosen when low lactose, low fat, and clean flavor are priorities [3].

- Whey protein hydrolysate (WPH): enzymatically pre-cleaved to varying degrees of hydrolysis (DH). Used for improved solubility, reduced allergenic potential, and specific texture targets, though hydrolysates carry characteristic bitter notes.

- Acid whey powder: byproduct of acid-coagulated dairy production (pH ~4.6), higher in lactic acid and minerals. Less common in confectionery due to flavor and hygroscopicity issues.

- Reduced-lactose and demineralized whey powders: modified powders where lactose, minerals, or both have been reduced to improve stability and functionality in specific applications.

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How is whey protein produced?

Whey enters the process as the liquid fraction remaining after casein has been separated from milk. In the sweet-whey route, rennet-coagulated cheese production leaves a whey stream at approximately pH 6.5. In the acid-whey route, isoelectric or cultured coagulation produces a stream near pH 4.6 [1,9].

The liquid whey is clarified to remove residual fat and fine casein particles, then concentrated. Ultrafiltration through membranes with molecular weight cutoffs of 10–20 kDa retains proteins while permeating lactose, minerals, and water — this is the primary route to WPC. Higher-purity isolates use additional diafiltration, microfiltration, or ion-exchange chromatography to selectively remove non-protein components. Spray drying yields the final powder [2,3]. Hydrolysates undergo an enzymatic step — typically with proteases such as trypsin, chymotrypsin, or Alcalase — before drying, producing peptides of controlled size distribution.

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What does whey protein do in confections?

Whey protein contributes multiple functions across candy categories. In nougat, marshmallow, and aerated bars, β-lactoglobulin and α-lactalbumin adsorb at the air-water interface and stabilize foams, sometimes replacing or complementing egg albumen [4,5]. In caramels, toffees, and fudge, whey proteins drive Maillard browning through reaction between lysine residues and reducing sugars, generating characteristic color and flavor compounds [1,6]. In chews and protein bars, whey proteins bind water, contribute chewy texture, and provide nutritional protein content — a category that has grown substantially in confectionery over the past decade [5]. In emulsion-based systems such as fat-containing caramels, whey proteins stabilize the fat-water interface through their amphiphilic structure.

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What is the molecular structure of whey protein?

The whey protein fraction is a mixture of globular proteins with distinct structures and functional behaviors. β-Lactoglobulin (β-lg) accounts for approximately 50–55% of bovine whey protein, is composed of 162 amino acid residues with a molecular weight near 18.4 kDa, and contains a hydrophobic β-barrel that binds small ligands including fatty acids and flavor compounds [1,3]. α-Lactalbumin (α-la) makes up 20–25% of the fraction, contains 123 residues at approximately 14.2 kDa, and binds calcium at a specific site that stabilizes its tertiary structure. Bovine serum albumin, immunoglobulins, lactoferrin, and lactoperoxidase are present as minor fractions [1].

Isoelectric points differ across the fraction — approximately 5.2 for β-lg and 4.2–4.5 for α-la — which drives the pH-dependent solubility behavior described below.

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What are the functional properties of whey protein in confections?

Solubility: Whey proteins are broadly soluble across the pH range but reach minimum solubility near their isoelectric points (~pH 4.5–5.2). Isolates typically maintain higher solubility than concentrates at any given pH due to lower fat and mineral content [3,5].

Thermal Behavior: α-Lactalbumin denatures reversibly near 62–65°C, while β-lactoglobulin denatures near 78°C with subsequent irreversible aggregation through disulfide interchange. This behavior determines cook-temperature limits for foam and emulsion stability [1,4].

Foaming: β-Lactoglobulin is the primary contributor to whey protein foam stability. Foam behavior is sensitive to pH, ionic strength, and prior thermal history, and is disrupted by residual fat — a key reason isolates outperform concentrates in aerated systems [4,5].

Maillard Reactivity: The lysine ε-amino groups on whey proteins react readily with reducing sugars during cooking and storage, driving both desirable browning in caramels and undesirable color and off-flavor development in stored powders [1,6].

Hygroscopicity: Whey powders are moderately to highly hygroscopic depending on lactose content, since amorphous lactose readily absorbs moisture and can trigger caking and Maillard browning during storage [1,7].

Shelf Stability: Storage stability is limited primarily by Maillard browning, lactose crystallization in high-lactose powders, and lipid oxidation in concentrates with residual fat. Cool, dry storage below 25°C and 65% RH is standard industry practice.

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How is whey protein regulated?

In the United States, whey and whey protein ingredients are affirmed as Generally Recognized as Safe (GRAS) under 21 CFR Part 184. Relevant sections include:

- 21 CFR 184.1979 — Whey

- 21 CFR 184.1979a — Reduced lactose whey

- 21 CFR 184.1979b — Reduced minerals whey

- 21 CFR 184.1979c — Whey protein concentrate

Under the Food Allergen Labeling and Consumer Protection Act (FALCPA), whey-containing products must declare milk as a major allergen. In the European Union, whey protein ingredients carry no E-number but must be labeled as containing milk under Regulation (EU) No 1169/2011. Codex Standard 289-1995 establishes international identity requirements for whey powders [8].

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References

1. Fox, P.F., Uniacke-Lowe, T., McSweeney, P.L.H., & O'Mahony, J.A. (2015). *Dairy Chemistry and Biochemistry* (2nd ed.). Springer.

2. Walstra, P., Wouters, J.T.M., & Geurts, T.J. (2006). *Dairy Science and Technology* (2nd ed.). CRC Press.

3. de Wit, J.N. (1998). Nutritional and functional characteristics of whey proteins in food products. *Journal of Dairy Science*, 81(3), 597–608.

4. Kinsella, J.E., & Whitehead, D.M. (1989). Proteins in whey: Chemical, physical, and functional properties. *Advances in Food and Nutrition Research*, 33, 343–438.

5. Foegeding, E.A., Davis, J.P., Doucet, D., & McGuffey, M.K. (2002). Advances in modifying and understanding whey protein functionality. *Trends in Food Science & Technology*, 13(5), 151–159.

6. Damodaran, S., & Parkin, K.L. (Eds.). (2017). *Fennema's Food Chemistry* (5th ed.). CRC Press.

7. Minifie, B.W. (1989). *Chocolate, Cocoa and Confectionery: Science and Technology* (3rd ed.). Van Nostrand Reinhold.

8. U.S. Food and Drug Administration. 21 CFR Part 184 — Direct Food Substances Affirmed as Generally Recognized as Safe.

9. Edwards, W.P. (2000). *The Science of Sugar Confectionery*. Royal Society of Chemistry.

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