protein aggregation in high-protein caramel a series of complex reactions and ... the various casein...

30 November 2016 • The Manufacturing Confectioner

Caramel is unique among confections inthat it calls for a dairy ingredient.

Through a series of complex reactions andprocesses, the proteins in the dairy ingredi-ent help provide a unique color, flavor andtexture in caramel. From a structural stand-point, caramel is made up of an amorphoussugar (sucrose, corn syrup, lactose) contin-uous phase with fat globules homoge-neously dispersed throughout. Lecithin isoften used to help create small fat globules,although proteins and the high-viscosityamorphous phase help prevent lipid coa-lescence. By varying water content, caramelscan be made with textures from soft andrunny to hard and glassy.

Proteins from the dairy ingredient are acritical component of caramel, providingcolor, flavor and structure through changesthat take place during cooking. Proteinsparticipate in Maillard browning, reactingwith reducing sugars to provide the desir-able caramel flavor and brown color. Someof them also undergo thermal denaturationand aggregation to form structures aroundthe fat globules and throughout the amor-phous phase to provide standup properties.However, when the extent of protein aggre-gation is excessive, the proteins actuallycoagulate and the result is protein grain.

Here, the caramel takes on a tapioca-likestructure, with large visible aggregates ofprotein structures (Figure 1), as it loses itsdesirable smooth texture.

There are two general categories of pro-teins in milk — the caseins (≈80%) and theserum proteins (≈20%). The various caseinproteins form into small (10 – 30 nm)micelles in milk in order to protect thehydrophobic components from interactingwith water. The hydrophilic segment thatforms the outer surface of the casein micelle,k-casein, provides steric protection againstaggregation of micelles. It is believed thatcolloidal calcium phosphate (c c p) con-tributes to hold the casein micelle together.However, the balance between calcium inthe serum phase and the ccp is dynamicand depends on conditions like tempera-ture, pH and addition of other salts. Thisbalance is key to controlling protein aggre-gation during heating.

Serum pro-teins include thetwo main wheyproteins, a-lac-talbumin and b-lactoglobulin, aswell as numerousother proteins,

Protein Aggregation in High-Protein CaramelThe current trend of increasing protein content in caramel to enhancenutrition can cause protein graining. Certain process steps can help.

Annaliese Eberle, Heather Mendenhall, Rich HartelUniversity of Wisconsin – Madison

Rich Hartel is a professorof food engineering inthe department of foodscience at the Universityof Wisconsin – Madison.He has worked theresince 1986. Part of hisduties include coordina-tion of the ResidenceCourse on Candy Sci-ence and Technology.

Figure 1

Protein Grain inCaramel

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